bluuebunny/crossref_metadata_2025 huggingface dataset:
Spin-transfer-induced magnetic domain formation
Authors: Yang T. , Hirohata A. , Kimura T. , Otani Y.
Published: October 2006

A special nanopillar comprised of a thick top ferromagnetic layer and a thin bottom ferromagnetic layer is fabricated and the transport properties are measured by applying a dc current and an external field. It is shown experimentally that the dc current flowing through the nanopillar could lead to intermediate states between the antiparallel and the parallel magnetic configurations. The intermediate states are characterized to be the result of domain formation in the bottom ferromagnetic layer, due to the injection of spin-polarized current. The results verify that the spin-transfer effect may induce domain formation in a magnetic thin film. It is also suggested that when the spin-transfer effect is utilized to switch the nanopillar device, the domain formation may result in the incomplete magnetization switching.
Ferroelectric switching of electrically commanded alignment layers for liquid crystal displays
Authors: Drevenšek-Olenik I. , Kunstelj K. , Koncilija J. , Komitov L.
Published: October 2006

Optical second harmonic generation (SHG) was used to probe the structural and dynamic properties of electrically commanded alignment layers for liquid crystal displays. The layers were 200nm thick and were made of siloxane-based side chain ferroelectric liquid crystal polymer (FLCP). The effect of an external dc electric field in the range of 0–2V∕μm on the SHG signal was probed in an empty sandwich cell and in a cell filled with an isotropic liquid (hexadecane). In both cases the nonlinear induced polarization shows characteristics of the “V-shaped” switching, which is associated with a relatively minor reorientational perturbation of the film. This signifies a presence of domain structure, which is strongly pinned to the substrates. The values of switching times deduced from the SHG response are two orders of magnitude larger from the values obtained by optical birefringence measurements. This observation suggests that in the top surface layer of the FLCP, which is mainly responsible for the birefringence and also for the so-called electrically commanded surface effect, the reorientation of the polymer side chains takes place much faster than in the regions close to the substrate.
Perpendicular magnetic anisotropy of epitaxially grown L1-FePdCu nanoparticles with preferential c-axis orientation
Authors: Naganuma Hiroshi , Sato Kazuhisa , Hirotsu Yoshihiko
Published: October 2006

Oriented and well-isolated 14-nm-sized Fe41Pd52Cu7 ternary alloy nanoparticles with the L10-type ordered structure have been fabricated by the sequential deposition of Pd, Cu, and Fe on NaCl (001) substrate followed by postdeposition annealing. The annealing temperature required to obtain a high coercivity decreased by at least 50K upon the addition of a small amount of Cu. Furthermore, it was revealed that a strong preferential c-axis orientation along the film normal direction was achieved by the addition of Cu, which resulted in a strong perpendicular magnetic anisotropy. The population of the nanoparticles with their c-axis oriented normal to the film plane was 74%. The alloy composition was independent of the particle size, as determined by energy dispersive x-ray spectroscopy using nanoprobe electrons. Nanobeam electron diffraction revealed that the axial ratio is constant for FePdCu nanoparticles with sizes between 10 and 25nm. Interparticle magnetostatic and exchange interactions played an insignificant role in the isolated FePdCu nanoparticles. The correlation between their preferential c-axis orientation and magnetic properties is discussed based on the rotation magnetization of single magnetic domain particles.
Structural modifications of SnO2 due to the incorporation of Fe into the lattice
Authors: Mathew Xavier , Enriquez J. P. , Mejía-García C. , Contreras-Puente G. , Cortes-Jacome M. A. , Toledo Antonio J. A. , Hays J. , Punnoose A.
Published: October 2006

Recently there is an increased interest in developing magnetic semiconductors due to their promising applications in spintronics. The semiconductors can be made ferromagnetic by doping with transition-metal ions. In this paper, the results of our studies using x-ray diffraction (XRD) and IR and Raman spectroscopic techniques on the effect of Fe doping on the structural properties of SnO2 are presented. The XRD results showed that the doping affects the structure and the lattice constants decrease as doping concentration increases, reaches a minimum, and again increases. The doped samples are under compressive strain and the strain is maximum for the sample doped with 3% (at. %) Fe. The grain size of the nanoparticles decreases from 42nm in undoped SnO2 to 26nm in Sn0.90Fe0.10O2. It was observed that the preferred orientation is along the (101) direction and both texture coefficient and preferential orientation show a dependence on doping level. The Raman spectra showed clear evidences of the change in grain size and incorporation of Fe into the crystal lattice. The Raman bands observed in the 700cm−1 region are assigned to the vibrational local modes of the Fe3+ ions which are occupying the sites of Sn4+ ions. The intensities of the Raman bands showed a strong dependence on the doping concentration. The decrease in intensity of the Sn–O symmetric stretching band at 630cm−1 for higher doping concentrations is explained to be due to the decrease in grain size. A striking correlation is found between the Fe Raman mode intensities and the ferromagnetic magnetization of Sn1−xFexO2, suggesting that the ferromagnetic behavior results from Fe3+ ions incorporated in the host SnO2 lattice.
Structural, optical, and electrical properties of (Zn,Al)O films over a wide range of compositions
Authors: Lu J. G. , Ye Z. Z. , Zeng Y. J. , Zhu L. P. , Wang L. , Yuan J. , Zhao B. H. , Liang Q. L.
Published: October 2006

(Zn,Al)O thin films have been prepared by a dc reactive magnetron sputtering system with the Al contents in a wide range of 0–50at.%. The structural, optical, and electrical properties of (Zn,Al)O films were detailedly and systematically studied. The amount of Al in the film was nearly the same as, but often lower than, that in the sputtering target. The growth rate of films monotonically decreased as the Al content increased. In a low Al content region (<10at.%), Al-doped ZnO (AZO) thin films could be obtained at 400°C in an Ar–O2 ambient with good properties. The optimal results of n-type AZO films were obtained at an Al content of 4at.%, with low resistivity ∼10−4Ωcm, high transmittance ∼90% in the visible region, and acceptable crystal quality with a high c-axis orientation. The band gap could be widened to 3.52eV at 4at.% Al due to the Burstein-Moss shift [E. Burstein, Phys. Rev. 93, 632 (1954)] modulated by many-body effects. An appropriate Al-doping concentration served effectively to release the residual, compressive stress in film, which may be the reason for the improvement in film stability and the increment in grain size as well. In a medium Al content region (10–30at.%), however, the film quality was degraded, which was presumably due to the formation of clusters or precipitates in the grains and boundaries. Besides the (002) plane, other diffraction peaks such as (100) and (101) planes of ZnO were observed, but the (Zn,Al)O films still exhibited a single-phase wurtzite ZnO structure. An intragrain cluster scattering mechanism was proposed to interpret the reduction of carrier mobility in films with the Al contents in the 7–20at.% region. The solubility limit of Al in ZnO film was identified to be in the 20–30at.% range, much higher than the thermodynamic solubility limit of 2–3at.% in ZnO. In a high Al content region (⩾30at.%), there were distinct observations for (Zn,Al)O films. As the Al content was 30at.%, the film appeared in a two-phase nature with ZnO hexagonal and Al2O3 rhombohedral structures. At the 50at.% Al content, the matrix of the (Zn,Al)O film was Al2O3, and no evident trace of wurtzite ZnO was observed. The electrical and optical properties for both cases were also very different from those at the Al contents below 30at.%.
Influence of hydrogen on the growth of FePt thin films
Authors: Maaß R. , Weisheit M. , Fähler S. , Schultz L.
Published: October 2006

FePt films have been prepared by pulsed laser deposition on MgO(100) in a forming gas atmosphere of 5% hydrogen in argon. At a pressure and temperature combination of 0.1 mbar and 800 °C, smooth continuous and well ordered L10 phase films can be obtained. The anisotropy field is close to the bulk value, while the coercivity is comparatively low at 0.15 T. This is in contrast to films deposited in vacuum, which are granular in nature and show huge coercivity. It is proposed that nucleation centers for island growth introduced by hydrogen on the MgO surface are responsible for this difference in growth mode. The temperature and pressure dependence of the surface morphology are explained by this assumption.
Leaky Lamb wave of a piezoelectric plate subjected to conductive fluid loading: Theoretical analysis and numerical calculation
Authors: Lee Yung-Chun , Kuo Shi Hoa
Published: October 2006

This paper examines in detail the characteristics of a leaky Lamb wave propagating in a piezoelectric plate immersed in a dielectric or conductive fluid. The analysis is based on the partial wave analysis and its numerical calculations. Some corrections have been made so that both the changes in phase velocity and the wave attenuation of leaky Lamb waves caused by fluid’s mechanical, dielectric, and conductive loadings are determined accurately. Influences of each material property of the loading fluid such as mass density, wave speed, permittivity, and conductivity on the leaky Lamb wave have been quantitatively characterized. Particular emphasis is placed on the velocity variations and excessive attenuation caused by the fluid’s conductivity. The results are important in designing piezoelectric acoustic wave sensors working in liquid phase.
Diagnostics of cadmium plasma produced by laser ablation
Authors: Shaikh Nek M. , Rashid B. , Hafeez S. , Mahmood S. , Saleem M. , Baig M. A.
Published: October 2006

Optical measurements of the cadmium plasma produced by the fundamental, second, and third harmonics of a Nd:YAG laser are reported. The excitation temperature and ionic temperature have been determined from the Boltzmann plot and Saha equation, whereas the number density is estimated from the Stark broadened profile of the spectral lines. The variations in the excitation temperature and number density with the ambient air pressure as well as with the laser irradiance have been studied. Besides, the spatial distributions of the temperature and number density have been investigated.
Quantitative x-ray phase-contrast imaging of air-assisted water sprays with high Weber numbers
Authors: Wang Y. J. , Im Kyoung-Su , Fezzaa K. , Lee W. K. , Wang Jin , Micheli P. , Laub C.
Published: October 2006

X-ray in-line phase-contrast imaging along with a single-image phase retrieval reconstruction was used to visualize the near-nozzle breakup of optically dense water jets atomized by a high-speed, annular air flow. The influence of the atomizing air on water mass distribution was investigated to reveal the complex air/liquid interactions at various breakup stages. Unlike low-Weber-number jets, the breakup of high-Weber-number jets can occur in the liquid core, which causes sudden decreases in liquid volume fraction.
Si
O
2
∕
Si
3
N
4
∕
Al
2
O
3
stacks for scaled-down memory devices: Effects of interfaces and thermal annealing
Authors: Lisiansky M. , Heiman A. , Kovler M. , Fenigstein A. , Roizin Y. , Levin I. , Gladkikh A. , Oksman M. , Edrei R. , Hoffman A. , Shnieder Y. , Claasen T.
Published: October 2006

Effects of interfaces and thermal annealing on the electrical performance of the SiO2∕Si3N4∕Al2O3 (ONA) stacks in nonvolatile memory devices were investigated. The results demonstrated the principal role of Si3N4∕Al2O3 and Al2O3/metal-gate interfaces in controlling charge retention properties of memory cells. Memory devices that employ both electron and hole trappings were fabricated using a controlled oxidation of nitride surface prior to the Al2O3 growth, a high-temperature annealing of the ONA stack in the N2+O2 atmosphere, and a metal gate electrode having a high work function (Pt). These devices exhibited electrical performance superior to that of their existing SiO2∕Si3N4∕SiO2 analogs.
Electrical properties of a single microcoiled carbon fiber
Authors: Shen Jiaoyan , Chen Zhaojia , Wang Nanlin , Li Wenjun , Chen Lijuan
Published: October 2006

Regular microcoiled carbon fibers with a double helix structure have been synthesized by the catalytic pyrolysis of acetylene at 750–790°C using Ni powder as a catalyst and thiophene as a promotor. The measurements by a standard four-probe technique of resistance, I-V curves, and magnetoresistance of a single microcoiled fiber are presented. I-V curves and the temperature dependence of the resistance are in accordance with Mott-David [Electronic Processes in Noncrystalline Materials (Oxford University Press, Oxford, 1979), 2nd ed., p. 32] variable range hopping above 13K and Shklovskii-Efros [Electronic Properites of Doped Semiconductors (Springer, Berlin, 1984), p. 202]; Pollak-Shklovshii [Hopping Transport in Solids, (North-Holland, Amsterdam, 1991), 273] variable range hopping below 13K. In addition, a positive magnetoresistance with H2-dependence behavior is observed at low temperature.
Generation of high-fidelity, down-chirped sub-10fsmJ pulses through filamentation for driving relativistic laser-matter interactions at 1kHz
Authors: Hauri C. P. , Trisorio A. , Merano M. , Rey G. , Lopez-Martens R. B. , Mourou G.
Published: October 2006

The authors present a simple add on for multicycle, multimJ Ti:sapphire-based amplifier systems to efficiently generate 9.5fs pulses with 1.8mJ. Filamentary propagation yields spectrally broadened pulses carrying an unexpected large group-delay dispersion of −500fs2 which allows linear propagation of the few-cycle pulses towards target areas without need of any sophisticated dispersion control. Pulse compression could easily be achieved by transmission through a combination of different glass substrates. The pulse wave front, the low energy fluctuations, and the good temporal contrast make this source well suited for relativistic laser-solid experiments with intense few-cycle pulses at kilohertz repetition rate.
Effects of C70 derivative in low band gap polymer photovoltaic devices: Spectral complementation and morphology optimization
Authors: Yao Yan , Shi Chenjun , Li Gang , Shrotriya Vishal , Pei Qibing , Yang Yang
Published: October 2006

Efficient polymer solar cells based on a low band gap copolymer poly{(9,9-dioctylfluorene)-2,7-diyl-alt-[4,7-bis(3-decyloxythien-2-yl)-2,1,3-benzothiadiazole]-5′,5″-diyl} and (6,6)-phenyl-C71-butyric acid methyl ester (C70-PCBM) were demonstrated with 2.4% power conversion efficiency under air mass 1.5G, 100mW∕cm2 illumination. The broad absorption peak of C70-PCBM in 440–530nm complements the absorption valley (regions between two absorption peaks at 416 and 584nm) of the polymer. The external quantum efficiency measurement further demonstrates that this increased absorption contributes significantly to the generation of photocurrent. Morphology studies on the blend films indicated that excellent miscibility between polymer and C70-PCBM favors exciton separation. The linear relationship between light intensity and short circuit current density shows efficient and balanced charge transport resulting in increased photocurrent and fill factor.
Simultaneous formation of SiC and Si nanostructures on silicon by local ion implantation and electron beam annealing
Authors: Markwitz A. , Johnson S. , Rudolphi M.
Published: October 2006

The authors demonstrate the fabrication of SiC nanocrystals on silicon by carbon ion implantation into silicon followed by electron beam annealing at 1000°C. A continuous asymmetric, pyramidal ridge around 20nm in height is observed at the boundary between the implanted and unimplanted regions. Adjacent to the ridge within the implanted region appears a trough which is continuous around the perimeter of the implanted/unimplanted boundary. The surface of the unimplanted region consists of pyramidal structures with an average height of 5–10nm which cover the entire surface.
Analysis of trapped quantum degenerate dipolar excitons
Authors: Rapaport Ronen , Chen Gang , Simon Steven
Published: October 2006

The dynamics of quantum degenerate two-dimensional dipolar excitons confined in electrostatic traps is analyzed and compared to recent experiments. The model results stress the importance of artificial trapping for achieving and sustaining a quantum degenerate exciton fluid in such systems and suggest that a long-lived, spatially uniform, and highly degenerate exciton system was experimentally produced in those electrostatic traps.
Low-voltage organic transistors on a polymer substrate with an aluminum foil gate fabricated by a laminating and electropolishing process
Authors: Yang Chanwoo , Shin Kwonwoo , Yang Sang Yoon , Jeon Hayoung , Choi Danbi , Chung Dae Sung , Park Chan Eon
Published: October 2006

The authors report flexible and low-voltage pentacene organic field-effect transistors (OFETs) constructed with an aluminum foil gate electrode, which was fabricated by the simple and low-cost roll-to-roll lamination process. Electropolishing the surface of laminated aluminum foil and spin coating it with an additional thin polymer film resulted in a gate dielectric surface with a root-mean-square roughness of about 0.85nm. These pentacene OFETs with a poly(α-methylstyrene)/anodized Al2O3 dual-layered gate dielectric exhibit a mobility of 0.52cm2∕Vs, an on-off ratio of 105, a subthreshold swing of 317mV/decade, and little hysteresis when operating at −5V.
Effects of compressive strain on optical properties of InxGa1−xN∕GaN quantum wells
Authors: Khan N. , Li J.
Published: October 2006

In 0.2 Ga 0.8 N ∕ Ga N multiple quantum well (MQW) blue light emitting diode (LED) structure was grown on a specially designed sapphire substrate (with increasing thickness from the edge to the center within a single wafer). X-ray diffraction revealed that the GaN lattice constant c decreases continuously from the edge to the center, indicating a continuous variation in the compressive strain. The spectral peak positions of the electroluminescence (EL) spectra exhibited a blueshift when probed at the edge as compared to the center, which is a direct consequence of the continuous variation in the compressive strain across the wafer. Based on the experimental results, a ratio of elastic stiffness constants (C33∕C13) for GaN was deduced to be ∼5.0±1.0, which was in agreement with the calculated value of ∼4.0. A linear relation of the EL emission peak position of LEDs with the biaxial strain was observed, and a linear coefficient of 19meV∕GPa characterizing the relationship between the band gap energy and biaxial stress of In0.2Ga0.8N∕GaN MQWs was also obtained.
Characterization of ultrashallow junctions using frequency-dependent junction photovoltage and its lateral attenuation
Authors: Faifer V. N. , Current M. I. , Schroder D. K.
Published: October 2006

A contactless method for ultrashallow junction (USJ) characterization is described based on analysis of frequency-dependent junction photovoltages from illuminated and nonilluminated areas. Relevant equations for junction photovoltages are derived. It is shown that the measured leakage current in USJ formed in halo profiles is related to space-charge region recombination.
Photochemical switching behavior of azofunctionalized polymer liquid crystal/SiO2 composite photonic crystal
Authors: Moritsugu M. , Kim S. N. , Ogata T. , Nonaka T. , Kurihara S. , Kubo S. , Segawa H. , Sato O.
Published: October 2006

A photochemically tunable photonic crystal was prepared by infiltrating azopolymer liquid crystal in a SiO2 inverse opal structure. The SiO2 inverse opal film obtained reflected a light corresponding to the periodicity as well as the refractive indices of the inverse opal structure. Linearly polarized light irradiation shifted the reflection band to longer wavelength more than 15nm. This is caused by the formation of anisotropic molecular orientation of the azopolymer. The switched state was stable in the dark, and the reversible switching of the reflection band can be achieved by the linearly and circularly polarized light irradiations.
A taxonomic revision of the genus Cyanostegia (Chloanthaceae).
Authors: Abid MA
Published: October 2006

A taxonomic revision of Cyanostegia is provided. Five species are recognized
of which C. corifolia is described for the first time. C. turcraninowii (nomen illegit.)
var dentata and angustifolia (nomina nuda) are found to be identical with the typical
varieties of C. microphylla and C. angustifolia respectively.
The affinities and distribution are discussed for each species. A new key to the species
is provided and a detailed revised description of each taxon is supplemented by a habit
sketch of a flowering branch and analytical drawings of the flowers.
A taxonomic revision of the genus Adenanthos (Proteaceae)
Authors: Nelson EC
Published: October 2006

Adenanthos Labill. (Proteaceae) is endemic to parts of southern Australia.
The presence of morphologic diversity and plasticity within the genus has resulted in taxo-
nomic uncertainty. The morphology of Adenanthos and associated terminology, as well
as aspects of the history of the genus, are discussed.
Adenanthos is revised taxonomically. The nomenclature of the infrageneric sections is
revised, and a new subsect. Anaclastos, within sect. Adenanthos, is designated. The
feminine gender is retained for the generic name. Eight new species are described:
A. dobagii,A. glabrescens, A eyrei,A. oreophila,A. macropodiana.A. labillardierei,A. ileticos
and A. cacomorpha. Four new subspecies are described: A. sericea subsp. sphalma,
A. cygnorum subsp. chamaephyton, A. pungens subsp. effusa and A. glabrescens subsp.
exasperata. Species and infraspecific taxa are described, and their ecology, relationships
and phytogeography are discussed. Putative hybrids are listed.
The genus Lepidium L. (Brassicaceae) in New Guinea.
Authors: Hewson HJ
Published: October 2006

A close study of the genus Papuzilla Ridley in conjunction with a revision of the
genus Lepidium L. in Australia has revealed that these taxa are synonymous. Three species
are recognized for New Guinea?two requiring new combinations, L. minutiflorum (Ridley)
Hewson, L. laeteviride (P. Royen) Hewson?and one new species, L. maccowagei Hewson.
The inflorescence is analysed.
Proposal for delineation of Botanical regions in Australia.
Authors: Barlow BA
Published: October 2006

A division of Australia into 33 botanical regions is proposed. The regions
may be useful for describing and illustrating geographic distributions of plant taxa, for
arrangement of specimens in herbaria, or for data base construction. The proposed
common boundaries of the botanical regions are meridians of longitude and parallels
of latitude, generating regions comprising from 10 to 44 1-degree grid cells. The botanical
regions proposed are thus compatible with grid cell mapping systems.
Yakirra (Paniceae, Poaceae), a new genus for Australia.
Authors: Lazarides M , Webster RD
Published: October 2006

Characteristics of gross morphology, epidermal features of
the palea of the fertile floret, and leaf anatomy are used to establish a new Australian
endemic genus, Yakirra. Its component of five species consists of three transferred from
Panicum L. (Yakirra australiensis, Y. pauciflora, Y. majuscula), one from Ichnanthus
P. Beauv. '(Y. muelleri) and one new species (Y. nulla Lazarides & R. Webster). A
systematic comparison with closely related genera shows the diagnostic features of
Yakirra. A morphological key and diagnoses of the species of Yakirra are provided.
A new North Queensland species of Glycine Willd. (Fabaceae)
Authors: Tindale MD
Published: October 2006

A new species of Glycine (Phaseolae) is described, viz.
G. curvata. It is illustrated in detail and a photograph of the seed coat surface provided.
A key is given to distinguish between G. curvata and its closest ally, G. cyrtoloba, from
Queensland and New South Wales.
Eucalyptus virens, a new species of Ironbark form Queensland.
Authors: Brooker MIH , Bean AR
Published: October 2006

Eucalyptus virens, a new species of ironbark from
Queensland, is described and illustrated and distribution maps are provided. The new
species belongs in the informal 'E. series Paniculatae' Pryor & Johnson and is closest to
E. panda S. T. Blake. E. virens is known only from three widely separated populations,
viz. north-west of Injune (upper Maranoa River), north of Tara and east of Inglewood.
Two of these populations are endangered by proposed or potential land development.
A taxonomic Revision of Calytrix Labill. (Myrtaceae)
Authors: Craven LA
Published: October 2006

A taxonomic revision of Calytrix Labill., an Australian endemic genus of
Myrtaceae, tribe Chamelaucieae, is presented. Lhotskya Schauer is reduced to a synonym
of Calytrix. Seventy-two species are recognized of which the following 22 are described
as new: C. amethystina, C. carinata, C. chrysantha, C. divergens, C. duplistipulata, C.
eneabbensis, C. erosipetala, C. formosa, C. gurulmundensis, C. gypsophila, C.
habrantha, C. islensis, C. microcoma, C. parvivallis, C. paucicostata, C. platycheiridia,
C. praecipua, C. rupestris, C. similis, C. truncatifolia, C. verruculosa and C.
warburtonensis. Two species comprise two subspecies each, of which one, C. simplex
subsp. suboppositifolia, is also described as new. Other than autonyms the following new
names result from the transfer of Calycothrix and Lhotskya species to Calytrix, and/ or
changes in taxonomic rank: C, acuttfolia, C, breviseta subsp. stipulosa, C. brownii, C.
drummondii, C. glaberrima, C. harvestiana, C. merrelliana, C. nematoclada, C.
purpurea, C. smeatoniana and C. sylvana.
Distinctive features of the morphology are discussed. A new term, cheiridium, is proposed
for an apparently adaptive structure formed from the peduncle and persistent,
connate bracteoles. Other biological aspects that are discussed briefly include floral
biology, fruit and dispersal, and geography. An informal infrageneric classification, based
largely upon floral features, is outlined. New taxa are illustrated. Distribution maps are
provided for all taxa.
Renal cortical cyclooxygenase 2 expression is differentially regulated by angiotensin II AT
1
and AT
2
receptors
Authors: Zhang Ming-Zhi , Yao Bing , Cheng Hui-Fang , Wang Su-Wan , Inagami Tadashi , Harris Raymond C.
Published: October 2006

Macula densa cyclooxygenase 2 (COX-2)-derived prostaglandins serve as important modulators of the renin-angiotensin system, and cross-talk exists between these two systems. Cortical COX-2 induction by angiotensin-converting enzyme (ACE) inhibitors or AT
1
receptor blockers (ARBs) suggests that angiotensin II may inhibit cortical COX-2 by stimulating the AT
1
receptor pathway. In the present studies we determined that chronic infusion of either hypertensive or nonhypertensive concentrations of angiotensin II attenuated cortical COX-2. Angiotensin II infusion reversed cortical COX-2 elevation induced by ACE inhibitors. However, we found that angiotensin II infusion further stimulated cortical COX-2 elevation induced by ARBs, suggesting a potential role for an AT
2
receptor-mediated pathway when the AT
1
receptor was inhibited. Both WT and AT
2
receptor knockout mice were treated for 7 days with either ACE inhibitors or ARBs. Cortical COX-2 increased to similar levels in response to ACE inhibition in both knockout and WT mice. In WT mice ARBs increased cortical COX-2 more than ACE inhibitors, and this stimulation was attenuated by the AT
2
receptor antagonist PD123319. In the knockout mice ARBs led to significantly less cortical COX-2 elevation, which was not attenuated by PD123319. PCR confirmed AT
1a
and AT
2
receptor expression in the cultured macula densa cell line MMDD1. Angiotensin II inhibited MMDD1 COX-2, and CGP42112A, an AT
2
receptor agonist, stimulated MMDD1 COX-2. In summary, these results demonstrate that macula densa COX-2 expression is oppositely regulated by AT
1
and AT
2
receptors and suggest that AT
2
receptor-mediated cortical COX-2 elevation may mediate physiologic effects that modulate AT
1
-mediated responses.
A role for adrenomedullin as a pain-related peptide in the rat
Authors: Ma Weiya , Chabot Jean-Guy , Quirion Remi
Published: October 2006

Adrenomedullin (AM) belongs to the calcitonin gene-related peptide (CGRP) family and is a well known potent vasodilator. We show here that AM is a powerful pain-inducing neuropeptide. AM-like immunoreactivity is widely distributed in both CGRP-containing and lectin IB4-binding nociceptors in dorsal root ganglion and axon terminals in the superficial dorsal horn of the rat spinal cord. Specific binding sites for the radioligand, [
125
I]AM13–52 as well as immunoreactivity for receptor markers such as the calcitonin receptor-like receptor and three receptor-activity-modifying proteins are localized in the superficial dorsal horn, demonstrating the existence of AM/CGRP receptors in this region. Intrathecal injection of rat AM1–50, dose- and time-dependently, induced long-lasting heat hyperalgesia and increased the phosphorylation of Akt and GSK3β in the dorsal horn. Pre- and posttreatments with the AM receptor antagonist AM22–52 and PI3 kinase inhibitors (LY294002 and Wortmannin) significantly blocked or reversed AM-induced heat hyperalgesia. Pre- and posttreatments with AM22–52 and Wortmannin also significantly blocked or reversed intraplantar capsaicin-induced heat hyperalgesia. Taken together, our results demonstrate that AM acts as a pain-inducing peptide in the dorsal horn. By activating specific receptors (likely AM2) and the PI3K/Akt/GSK3β signaling pathway, AM could play a significant role in long-lasting heat hypersensitivity and inflammatory heat hyperalgesia.
Powering the planet: Chemical challenges in solar energy utilization
Authors: Lewis Nathan S. , Nocera Daniel G.
Published: October 2006

Global energy consumption is projected to increase, even in the face of substantial declines in energy intensity, at least 2-fold by midcentury relative to the present because of population and economic growth. This demand could be met, in principle, from fossil energy resources, particularly coal. However, the cumulative nature of CO2emissions in the atmosphere demands that holding atmospheric CO2levels to even twice their preanthropogenic values by midcentury will require invention, development, and deployment of schemes for carbon-neutral energy production on a scale commensurate with, or larger than, the entire present-day energy supply from all sources combined. Among renewable energy resources, solar energy is by far the largest exploitable resource, providing more energy in 1 hour to the earth than all of the energy consumed by humans in an entire year. In view of the intermittency of insolation, if solar energy is to be a major primary energy source, it must be stored and dispatched on demand to the end user. An especially attractive approach is to store solar-converted energy in the form of chemical bonds, i.e., in a photosynthetic process at a year-round average efficiency significantly higher than current plants or algae, to reduce land-area requirements. Scientific challenges involved with this process include schemes to capture and convert solar energy and then store the energy in the form of chemical bonds, producing oxygen from water and a reduced fuel such as hydrogen, methane, methanol, or other hydrocarbon species.
Modular chemical mechanism predicts spatiotemporal dynamics of initiation in the complex network of hemostasis
Authors: Kastrup Christian J. , Runyon Matthew K. , Shen Feng , Ismagilov Rustem F.
Published: October 2006

This article demonstrates that a simple chemical model system, built by using a modular approach, may be used to predict the spatiotemporal dynamics of initiation of blood clotting in the complex network of hemostasis. Microfluidics was used to create
in vitro
environments that expose both the complex network and the model system to surfaces patterned with patches presenting clotting stimuli. Both systems displayed a threshold response, with clotting initiating only on isolated patches larger than a threshold size. The magnitude of the threshold patch size for both systems was described by the Damköhler number, measuring competition of reaction and diffusion. Reaction produces activators at the patch, and diffusion removes activators from the patch. The chemical model made additional predictions that were validated experimentally with human blood plasma. These experiments show that blood can be exposed to significant amounts of clot-inducing stimuli, such as tissue factor, without initiating clotting. Overall, these results demonstrate that such chemical model systems, implemented with microfluidics, may be used to predict spatiotemporal dynamics of complex biochemical networks.
Human DNA polymerase κ forms nonproductive complexes with matched primer termini but not with mismatched primer termini
Authors: Carlson Karissa D. , Johnson Robert E. , Prakash Louise , Prakash Satya , Washington M. Todd
Published: October 2006

Human DNA polymerase kappa (pol κ) is a member of the Y family of DNA polymerases that function in translesion synthesis. It synthesizes DNA with moderate fidelity and does not efficiently incorporate nucleotides opposite DNA lesions. Pol κ has the unusual ability to efficiently extend from mismatched primer termini, and it extends readily from nucleotides inserted by other DNA polymerases opposite a variety of DNA lesions. All of this has suggested that pol κ functions during the extension step of translesion synthesis. Here, we have carried out pre-steady-state kinetic studies of pol κ using DNA with matched and mismatched primer termini. Interestingly, we find that mismatches present only a modest kinetic barrier to nucleotide incorporation by pol κ. Moreover, and quite surprisingly, active-site titrations revealed that the concentration of active pol κ is very low with matched DNA, and from DNA trapping experiments we determined that this was due to the formation of nonproductive protein·DNA complexes. In marked contrast, we found that the concentration of active pol κ was six-fold greater with mismatched DNA than with matched DNA. Thus, pol κ forms nonproductive complexes with matched but not with mismatched DNA. From these observations, we conclude that pol κ has evolved to specifically function on DNA substrates with aberrant primer-terminal base pairs, such as the ones it would encounter during the extension step of translesion synthesis.
Cross Talk between Activation and Slow Inactivation Gates of Shaker Potassium Channels
Authors: Panyi Gyorgy , Deutsch Carol
Published: October 2006

This study addresses the energetic coupling between the activation and slow inactivation gates of Shaker potassium channels. To track the status of the activation gate in inactivated channels that are nonconducting, we used two functional assays: the accessibility of a cysteine residue engineered into the protein lining the pore cavity (V474C) and the liberation by depolarization of a Cs+ ion trapped behind the closed activation gate. We determined that the rate of activation gate movement depends on the state of the inactivation gate. A closed inactivation gate favors faster opening and slower closing of the activation gate. We also show that hyperpolarization closes the activation gate long before a channel recovers from inactivation. Because activation and slow inactivation are ubiquitous gating processes in potassium channels, the cross talk between them is likely to be a fundamental factor in controlling ion flux across membranes.
Canalization of auxin flow by Aux/IAA-ARF-dependent feedback regulation of PIN polarity
Authors: Sauer Michael , Balla Jozef , Luschnig Christian , Wiśniewska Justyna , Reinöhl Vilém , Friml Jiří , Benková Eva
Published: October 2006

Plant development is characterized by a profound ability to regenerate and form tissues with new axes of polarity. An unsolved question concerns how the position within a tissue and cues from neighboring cells are integrated to specify the polarity of individual cells. The canalization hypothesis proposes a feedback effect of the phytohormone auxin on the directionality of intercellular auxin flow as a means to polarize tissues. Here we identify a cellular and molecular mechanism for canalization. Local auxin application, wounding, or auxin accumulation during de novo organ formation lead to rearrangements in the subcellular polar localization of PIN auxin transport components. This auxin effect on PIN polarity is cell-specific, does not depend on PIN transcription, and involves the Aux/IAA-ARF (indole-3-acetic acid-auxin response factor) signaling pathway. Our data suggest that auxin acts as polarizing cue, which links individual cell polarity with tissue and organ polarity through control of PIN polar targeting. This feedback regulation provides a conceptual framework for polarization during multiple regenerative and patterning processes in plants.
Uric acid and xanthine oxidase: future therapeutic targets in the prevention of cardiovascular disease?
Authors: Dawson Jesse , Walters Matthew
Published: October 2006

Serum uric acid may be an independent risk factor for cardiovascular disease. This review examines this association, potential mechanisms, and explores whether strategies to reduce uric acid will improve outcomes. The recent studies of xanthine oxidase inhibition are given particular focus. Epidemiological evidence supports the theory that uric acid is an independent risk factor for cardiovascular disease. Recent studies of losartan, atorvastatin and fenofibrate suggest that uric acid reduction contributes to the risk reduction offered by these therapies. Several small studies of xanthine oxidase inhibition have shown improvements in measures of cardiovascular function of a similar magnitude to that of other proven preventative treatments. These trial data and the convincing epidemiological evidence mandate that large clinical trials of uric acid‐lowering strategies are performed in patients with or at high risk of cardiovascular disease. If such approaches are shown to be effective in reducing cardiovascular events, they would represent a novel and cost‐effective preventative approach.
Isolation of an adult blood‐derived progenitor cell population capable of differentiation into angiogenic, myocardial and neural lineages
Authors: Porat Yael , Porozov Svetlana , Belkin Danny , Shimoni Daphna , Fisher Yehudit , Belleli Adina , Czeiger David , Silverman William F. , Belkin Michael , Battler Alexander , Fulga Valentin , Savion Naphtali
Published: October 2006

Blood‐derived adult stem cells were previously considered impractical for therapeutic use because of their small numbers. This report describes the isolation of a novel human cell population derived from the peripheral blood, termed synergetic cell population (SCP), and defined by the expression of CD31Bright, CD34+, CD45−/Dim and CD34Bright, but not lineage‐specific features. The SCP was capable of differentiating into a variety of cell lineages upon exposure to defined culture conditions. The resulting cells exhibited morphological, immunocytochemical and functional characteristics of angiogenic, neural or myocardial lineages. Angiogenic cell precursors (ACPs) expressed CD34, CD133, KDR, Tie‐2, CD144, von Willebrand factor, CD31Bright, concomitant binding of Ulex‐Lectin and uptake of acetylated low density lipoprotein (Ac‐LDL), secreted interleukin‐8, vascular endothelial growth factor and angiogenin and formed tube‐like structures in vitro. The majority of CD31Bright ACP cells demonstrated Ac‐LDL uptake. Neural cell precursors (NCPs) expressed the neuronal markers Nestin, βIII‐Tubulin, and Neu‐N, the glial markers GFAP and O4, and responded to neurotransmitter stimulation. Myocardial cell precursors (MCPs) expressed Desmin, cardiac Troponin and Connexin 43. In conclusion, the simple and rapid method of SCP generation and the resulting considerable quantities of lineage‐specific precursor cells makes it a potential source of autologous treatment for a variety of diseases.
Multiple anthropogenic stressors cause ecological surprises in boreal lakes
Authors: CHRISTENSEN MICHAEL R. , GRAHAM MARK D. , VINEBROOKE ROLF D. , FINDLAY DAVID L. , PATERSON MICHAEL J. , TURNER MICHAEL A.
Published: October 2006

The number of combinations of anthropogenic stressors affecting global change is increasing; however, few studies have empirically tested for their interactive effects on ecosystems. Most importantly, interactions among ecological stressors generate nonadditive effects that cannot be easily predicted based on single‐stressor studies. Here, we corroborate findings from anin situmesocosm experiment with evidence from a whole‐ecosystem manipulation to demonstrate for the first time that interactions between climate and acidification determine their cumulative impact on the food‐web structure of coldwater lakes. Interactions among warming, drought, and acidification, rather than the sum of their individual effects, best explained significant changes in planktonic consumer and producer biomass over a 23‐year period. Further, these stressors interactively exerted significant synergistic and antagonistic effects on consumers and producers, respectively. The observed prevalence of long‐ and short‐term ecological surprises involving the cumulative impacts of multiple anthropogenic stressors highlights the high degree of uncertainty surrounding current forecasts of the consequences of global change.
Structure and expression of a novel gene family showing male germline specific expression in Drosophila melanogaster
Authors: Di Cara F. , Morra R. , Cavaliere D. , Sorrentino A. , De Simone A. , Polito C. L. , Digilio A. F.
Published: October 2006

We report the characterization of two novel genes of Drosophila melanogaster, named mst36Fa and mst36Fb. They define a novel gene family, showing identical time and tissue‐specificity limited to male germ cells where their transcription starts during meiotic prophase. These two genes encode for two slightly basic proteins highly homologous to each other and fairly rich in leucine and glutamic acid. Although strictly clustered, these genes utilize different promoter regions as revealed by examination of transgenic flies bearing mst36F‐promoter‐lacZ reporter constructs and by reverse transcription–polymerase chain reaction assays. Our data suggest that at least one gene (mst36Fa) of the cluster is under translational repression until spermiogenesis suggesting a putative role in the spermatides differentiation. The present study is aimed at the structural analysis of these genes.
Population structure of an island malaria vector
Authors: FOLEY D. H. , TORRES E. P.
Published: October 2006

Abstract The impact of islands on the population structure of Anopheles flavirostris (Ludlow) (Diptera: Culicidae), the primary malaria vector in the Philippines, was assessed. A phylogenetic analysis of 16 cytochrome oxidase subunit 1 (CO1) haplotypes revealed three clades: one basal clade containing genetically disparate haplotypes from Mindanao, and two derived clades, one of which was largely confined to the largest island, Luzon, and one that was widespread except for Luzon. For the Luzon clade, nested clade analysis revealed an isolation‐by‐distance effect, and a mismatch distribution analysis diagnosed a recent demographic expansion (sum of squared deviation, SDD = 0.0093, P= 0.075), which mirrors demographic attributes found in mainland primary malaria vectors and could inflate estimates of gene flow from FST. For the widespread clade, evidence of range expansion and past fragmentation and/or long distance colonization from the Visayas or Mindanao to Palawan is suggested. A south‐to‐north range expansion of An. flavirostris is suggested; estimates of coalescence for the Luzon clade was 214 000 years ago (ya) (95% confidence interval 35 600–298 000 ya), i.e. late Pleistocene. Present day rather than Pleistocene island association and some, but not all, sea barriers appeared to be important for An. flavirostris population structure. Our results suggest that endemic island malaria vector species need to be considered before any generalizations are made about the population structure of primary and secondary vectors.
Assessment of gastric sensorimotor function in paediatric patients with unexplained dyspeptic symptoms and poor weight gain
Authors: Hoffman I. , Vos R. , Tack J.
Published: October 2006

Abstract  Recent studies indicate that impaired meal accommodation or hypersensitivity to distention are highly prevalent in adult functional dyspepsia (FD). Our aim was to investigate whether similar abnormalities also occur in paediatric FD. Sixteen FD patients (15 girls, 10–16 years) were studied. The severity (0–3; 0, absent; 3, severe) of eight dyspeptic symptoms (epigastric pain, fullness, bloating, early satiety, nausea, vomiting, belching and epigastric burning) and the amount of weight loss were determined by questionnaire. All children underwent a gastric barostat study after an overnight fast to determine sensitivity to distention and meal‐induced accommodation, which were compared with normal values in young adults (18–22 years). On a separate day, all patients underwent a gastric emptying breath test. A mean weight loss of 4.8 ± 0.9 kg was present in 14 children. Compared with controls, patients had lower discomfort thresholds to gastric distention (8.8 ± 1.0 mmHg vs 13.9 ± 1.9 mmHg, P < 0.02) and gastric accommodation (87 ± 25 mL vs 154 ± 20 mL P < 0.04). Hypersensitivity to distention and impaired accommodation were present in respectively nine (56%) and 11 (69%) patients. No relationship was found between barostat and gastric emptying, which was delayed in only three patients. The majority of children with unexplained epigastric symptoms have abnormalities of gastric sensorimotor function.
The relationship between the effects of short‐chain fatty acids on intestinal motility in vitro and GPR43 receptor activation
Authors: Dass N. B. , John A. K. , Bassil A. K. , Crumbley C. W. , Shehee W. R. , Maurio F. P. , Moore G. B. T. , Taylor C. M. , Sanger G. J.
Published: October 2006

Abstract  The G protein‐coupled receptors, GPR41 and GPR43, are activated by short‐chain fatty acids (SCFAs), with distinct rank order potencies. This study investigated the possibility that SCFAs modulate intestinal motility via these receptors. Luminal SCFA concentrations within the rat intestine were greatest in the caecum (c. 115 mmol L−1) and proximal colon. Using similar concentrations (0.1–100 mmol L−1), SCFAs were found to inhibit electrically evoked, neuronally mediated contractions of rat distal colon, possibly via a prejunctional site of action; this activity was independent of the presence or absence of the mucosa. By contrast, SCFAs reduced the amplitude but also reduced the threshold and increased the frequency of peristaltic contractions in guinea‐pig terminal ileum. In each model, the rank‐order of activity was acetate (C2) ≈ propionate (C3) ≈ butyrate (C4) > pentanoate (C5) ∼ formate (C1), consistent with activity at the GPR43 receptor. GPR43 mRNA was expressed throughout the rat gut, with highest levels in the colon. However, the ability of SCFAs to inhibit neuronally mediated contractions of the colon was similar in tissues from wild‐type and GPR43 gene knockout mice, with identical rank‐orders of potency. In conclusion, SCFAs can modulate intestinal motility, but these effects can be independent of the GPR43 receptor.