bluuebunny/crossref_metadata_2025 huggingface dataset:
A physical mechanism of the atmospheric response over Antarctica to decadal trends in tropical SST
Authors: Grassi Barbara , Redaelli Gianluca , Visconti Guido
Published: September 2006

The atmospheric response to the tendency of oceanic equatorial temperature observed during recent decades has been simulated, leading to the identification of a possible link between tropical Sea Surface Temperature (SST) and Antarctic climate change. The dynamical mechanism, by which changes in tropical SSTs exert an influence on the upper latitude atmospheric dynamics, is investigated. The analysis of the simulations suggests that the perturbations of the atmospheric circulation are induced by changes in the annual cycle of the tropical convective activity, which influences the intensity of the wave forcing. In particular, the introduction of the SST perturbation generates a strong vertical wind shear at middle latitude during the Antarctic winter affecting the propagation of convectively generated waves during the following spring.
Variability in Deep Western Boundary Current transports: Preliminary results from 26.5°N in the Atlantic
Authors: Meinen Christopher S. , Baringer Molly O. , Garzoli Silvia L.
Published: September 2006

Transport fluctuations of the deep limb of the Meridional Overturning Circulation (MOC) near the western boundary are presented from a line of inverted echo sounders, bottom pressure sensors, and a deep current meter east of Abaco Island, Bahamas, at 26.5°N from September 2004 through September 2005. The mean southward flow between 800 dbar and 4800 dbar was 39 × 106 m3 s−1, with a northward recirculation of 28 × 106 m3 s−1, leaving a net southward flow of 11 × 106 m3 s−1 as the through‐flow of the Deep Western Boundary Current (DWBC). The mean southward DWBC flow essentially equals previous values that were measured at the same location by arrays of current meters deployed from 1986 to 1992. DWBC transport spectra indicate that barotropic and baroclinic changes have very similar energy levels at most periods less than 10 days and that barotropic changes dominate at periods of 10–80 days.
Formation mechanisms of temperature inversions in the southeastern Arabian Sea
Authors: Kurian Jaison , Vinayachandran P. N.
Published: September 2006

Numerical simulations using a high resolution (0.25° × 0.25°, 40 levels) OGCM of the Indian Ocean are used to study the formation mechanisms of temperature inversions (TI) in the southeastern Arabian Sea (SEAS) during winter. To the west and south of India, haline stratification is a necessary pre‐requisite for TI formation. Off the southern tip of India, low‐salinity water advected from the Bay of Bengal is cooled by strong winds and leads to TI formation. In the southern part of the SEAS, advection of this cooler low‐salinity water over warm salty SEAS water leads to the formation of TI and occur at a deeper depth (∼80 m) due to the downwelling within the Lakshadweep High. In the northern part, TI occur at a much shallower depth (∼20 m) and are caused by shortwave radiation penetrating below the mixed layer of about 12 m.
Relationships between albedo and microwave emissions over thin newly formed sea ice during fall freeze‐up
Authors: Hwang Byong Jun , Ehn Jens K. , Barber David G.
Published: September 2006

This study examines the relationship between albedo and microwave emissions over thin newly formed Arctic sea ice using in‐situ measurements collected 19 Oct – 13 Nov 2003 in the Cape Bathurst Polynya, southern Beaufort Sea. Regression analysis show that statistically significant relationships exist between the microwave polarization ratio (PR(19)) and sea ice albedo. The albedo derived from the relationship with the PR(19) is compared to the albedo calculated from two parameterization schemes used in the climate models. The results show that the parameterized albedo significantly underestimates over thin ice or overestimates over thick snow‐covered ice relative to both the in‐situ and microwave‐derived albedo. This study suggest that use of satellite passive microwave data should be considered in order to improve the treatment of surface albedo in regional climate models, in seasonal or marginal ice zones.
Vibrational relaxation of CO2(ν2) by atomic oxygen
Authors: Castle Karen J. , Kleissas Katherine M. , Rhinehart Justin M. , Hwang Eunsook S. , Dodd James A.
Published: September 2006

In the Earth's upper atmosphere, collisions with ambient O atoms efficiently excite the CO2 [0000] vibrational ground‐state population to the first excited, [0110] or ν2, vibrational bend state. Subsequent relaxation of the ν2 population occurs through spontaneous emission of 15‐μm radiation. Much of this radiation escapes into space, thereby removing ambient kinetic energy from the atmosphere. This cooling mechanism is especially important at altitudes between the mesopause and the lower thermosphere, approximately 80–120 km, where the O‐atom density is relatively high and the kinetic temperature is rising. Laboratory measurements have been performed to better characterize the CO2(ν2)‐O vibrational relaxation rate coefficient kO(ν2). A 266‐nm laser pulse photolyzed trace amounts of O3 in a CO2‐O3‐rare gas mixture, simultaneously creating O atoms and raising the gas temperature to create a nonequilibrium CO2 vibrational distribution. Transient diode laser absorption spectroscopy was used to monitor CO2 vibrational level population reequilibration. A global nonlinear least squares fitting technique was used to interpret the kinetic data, yielding kO(ν2) = (1.8 ± 0.3) × 10−12 cm3s−1. The result is in good agreement with previous laboratory measurements, with published kO(ν2) values in the (1.2–1.5) × 10−12 cm3s−1 range and at the low end of the (2–6) × 10−12 cm3s−1 range estimated from the analysis of upper atmospheric data.
Lagrangian study of the Panama Bight and surrounding regions
Authors: Chaigneau Alexis , Abarca del Rio Rodrigo , Colas François
Published: September 2006

Near‐surface circulation of the Panama Bight and surrounding regions [0–9°N; 73°W–90°W] was studied using satellite‐tracked drifter trajectories from 1979–2004. This region encompasses three major currents showing typical velocities of ∼30 cm s−1: (1) the eastward North Equatorial Counter Current (NECC), (2) the near‐circular Panama Bight Cyclonic Gyre (PBCG), and (3) the westward South Equatorial Current (SEC). We do not observe significant modification of the mean surface circulation during El Niño Southern Oscillation events, even if the SEC is slightly reinforced during relatively warm El Niño periods. At seasonal scales, the circulation is strongly controlled by the activity of the Panama wind‐jet: in boreal winter, the currents are stronger and an anticyclonic cell is present west of the PBCG. This dipole leads to a strong ∼200 km wide southward current which then disappears during the rest of the year. In summer, the three major currents have reduced intensity by 30%–40%. Large‐scale current vorticity shows that the upwelling associated with the PBCG is also 3–4 times stronger in winter than during summer months. The kinetic energy is largely dominated by eddy activity and its intensity is double in winter than during summer. Ageostrophic motions and eddy activity appear to have a substantial impact on the energy spatial distribution. In the NECC and SEC regions, Lagrangian scales are anisotropic and zonally enhanced in the direction of the mean currents. The typical integral time and length scales of these regions are 2.5 days and 50–60 km in the zonal direction and 1.5 days and 25–30 km in the meridional direction. Lateral eddy diffusivity coefficients are on the order of 11–14 107 cm2 s−1 zonally and 5–6 107 cm2 s−1 meridionally. In contrast, in the PBCG region, the Lagrangian characteristics are isotropic with typical timescales of 1.7 days, space scales of 30 km and eddy diffusivity coefficients of 6 107 cm2 s−1 in both directions.
Gibberellic‐acid‐induced reorientation of cortical microtubules in living plant cells
Authors: LLOYD C. W. , SHAW P. J. , WARN R. M. , YUAN M.
Published: September 2006

By microinjecting rhodamine‐conjugated porcine tubulin into pea epidermis we recently showed how cortical microtubules reorientate from transverse to longitudinal in living cells (Yuan et al., 1994, Proc. Nat. Acad. Sci, USA91, 6050–6053). In the present paper we compare this reorientation with the contrary longitudinal to transverse realignment induced by adding gibberellic acid to pre‐injected cells on the microscope slide. Both kinds of reorientation are initiated by the appearance of ‘discordant’ microtubules which do not share the existing alignment but anticipate the new direction. These increase in number as the existing microtubules depolymerize, one alignment apparently replacing the other in a continuous process.

By rotating stacks of confocal sections by computer methods we have previously shown that microtubules at the outer tangential cell wall do not necessarily have the same orientation as microtubules at the adjoining anticlinal walls of the same cell (Yuan et al., 1995, Plant J.7, 17–23). This suggests that microtubule reorientations in these epidermal cells occur mainly (or, at least, first) at the outer wall, indicating that the array may not reorientate as a whole. Collectively, these data emphasize the discontinuous nature of the realignment process, the importance of new microtubule polymerization, and the special property of the outer epidermal surface as a sensitive domain.
Video microscopy of dynamic plant cell organelles: principles of the technique and practical application
Authors: LICHTSCHEIDL I. K. , FOISSNER I.
Published: September 2006

Video microscopy, including video‐enhanced contrast, ultraviolet and video‐intensified fluorescence microscopy, was applied to the visualization and analysis of organelles and cytoskeletal elements at the border of resolution of the light microscope. We describe the principles of video microscopy and the necessary technical equipment, and discuss the advantages and limitations with the example of three selected plant cells. In characean internodal cells we observed the motility and disappearance of Golgi secretory vesicles during wound wall formation by video‐enhanced contrast microscopy. In Byblis gland hairs we investigated the movement of different organelles along bundles of actin microfilaments by ultraviolet microscopy, and in onion inner epidermal cells we visualized the arrangement of actin microfilaments during different stages of plasmolysis with video‐intensified fluorescence microscopy.
Localization of Methyl Benzoate Synthesis and Emission in Stephanotis floribunda and Nicotiana suaveolens Flowers
Authors: Rohrbeck D. , Buss D. , Effmert U. , Piechulla B.
Published: September 2006

Abstract: The emission of fragrances can qualitatively and quantitatively differ in different parts of flowers. A detailed analysis was initiated to localize the floral tissues and cells which contribute to scent synthesis in Stephanotis floribunda (Asclepiadaceae) and Nicotiana suaveolens (Solanaceae). The emission of scent compounds in these species is primarily found in the lobes of the corollas and little/no emission can be attributed to other floral organs or tissues. The rim and centre of the petal lobes of S. floribunda contribute equally to scent production since the amount of SAMT (salicylic acid carboxyl methyltransferase) and specific SAMT activity compensate each other in the rim region and centre region. In situ immunolocalizations with antibodies against the methyl benzoate and methyl salicylate‐synthesizing enzyme indicate that the adaxial epidermis with few subepidermal cell layers of S. floribunda is the site of SAMT accumulation. In N. suaveolens flowers, the petal rim emits twice as much methyl benzoate due to higher total protein concentrations in the rim versus the petal centre; and, both the adaxial and abaxial epidermis house the BSMT (salicylic acid/benzoic acid carboxyl methyltransferase).
Modification of Primary and Secondary Metabolism of Potato Plants by Nitrogen Application Differentially Affects Resistance to Phytophthora infestans and Alternaria solani
Authors: Mittelstraß K. , Treutter D. , Pleßl M. , Heller W. , Elstner E. F. , Heiser I.
Published: September 2006

Abstract: Potato plants (Solanum tuberosum L. cv. Indira) were grown at two levels of N supply in the greenhouse. Plants supplied with 0.8 g N per plant (high N variant) showed significantly increased biomass as compared to plants without additional N fertilisation (low N variant). C/N ratio was lower and protein content was higher in leaves of the high N variant. The concentration of chlorogenic acids and flavonols was significantly lower in leaves from the high N variant. Whereas resistance to Alternaria solani increased when plants were supplied with additional nitrogen, these plants were more susceptible to Phytophthora infestans. After infection with both pathogens, we found a strong induction of p‐coumaroylnoradrenaline and p‐coumaroyloctopamine, which are identified for the first time in potato leaves and are discussed as resistance factors of other solanaceous plants.
Lipopolysaccharides of Pectobacterium atrosepticum and Pseudomonas corrugata Induce Different Defence Response Patterns in Tobacco, Tomato, and Potato
Authors: Desender S. , Klarzynski O. , Potin P. , Barzic M.‐R. , Andrivon D. , Val F.
Published: September 2006

Abstract: Lipopolysaccharides (LPS), ubiquitous cell surface components of Gram‐negative bacteria, are directly implicated in plant/pathogen interactions. However, their perception by the plant, the subsequent signal transduction in both compatible and incompatible interactions, as well as the defence reactions induced in compatible interactions are as yet poorly understood. We focused on biochemical and physiological reactions induced in cell suspensions of three Solanaceae species (tobacco, tomato, and potato) by purified lipopolysaccharides from Pectobacterium atrosepticum (Pa), a pathogen of potato, and Pseudomonas corrugata (Psc), a pathogen of tomato. LPS Pa and LPS Psc caused a significant acidification of potato, tomato, and tobacco extracellular media, whereas laminarin (a linear β□1,3 oligosaccharide elicitor) induced an alkalinisation in tobacco and tomato, but not in potato cell suspensions. None of the two LPS induced the formation of active oxygen species in any of the hosts, while laminarin induced H2O2 production in cells of tobacco but not of tomato and potato. In tomato cells, LPS Pa and LPS Psc induced a strong but transitory stimulation of lipoxygenase activity, whereas laminarin induced a stable or slightly increasing LOX activity over the first 24 h of contact. In tobacco, LOX activity was not triggered by either LPS, but significantly increased following treatment with laminarin. In potato, neither LPS nor laminarin induced LOX activity, in contrast with concentrated culture filtrate of Phytophthora infestans (CCF). These results demonstrate that LPS, as well as laminarin, are perceived in different ways by Solanaceae species, and possibly cultivars. They also suggest that defence responses modulated by LPS depend on plant genotypes rather than on the type of interaction.
Gas Exchange and Growth Responses of Ectomycorrhizal Picea mariana, Picea glauca, and Pinus banksiana Seedlings to NaCl and Na2SO4
Authors: Nguyen H. , Calvo Polanco M. , Zwiazek J. J.
Published: September 2006

Abstract: Black spruce (Picea mariana), white spruce (Picea glauca), and jack pine (Pinus banksiana) seedlings were inoculated with Hebeloma crustuliniforme or Laccaria bicolor and subjected to NaCl and Na2SO4 treatments. The effects of ectomycorrhizas on salt uptake, growth, gas exchange, and needle necrosis varied depending on the tree and fungal species. In jack pine seedlings, ectomycorrhizal (ECM) fungi reduced shoot and root dry weights and in the ECM white spruce, there was a small increase in dry weights. Sodium chloride treatment reduced net photosynthesis and transpiration rates in the three studied tree species. However, NaCl‐treated black spruce and jack pine colonized by H. crustuliniforme maintained relatively high photosynthetic and transpiration rates and needle necrosis of NaCl‐treated black spruce seedlings was reduced by the ECM fungi. Higher concentrations of Na+ were found in shoots compared with roots of the three examined conifer species. ECM fungi reduced the concentrations of Na+ mainly in the shoots and this reduction was greater in plants treated with NaCl compared with Na2SO4. Shoots contained generally higher concentrations of Cl‐ compared with roots. In the NaCl‐treated black spruce and white spruce, both ECM species significantly reduced Cl‐ concentrations. Our results point to overall greater phytotoxicity of NaCl compared with Na2SO4 and support our earlier findings which demonstrated beneficial effects of ECM fungi for woody plants exposed to NaCl stress.
A Novel Rice MAPK Gene,OsBIMK2,is Involved in Disease‐Resistance Responses
Authors: Song D. , Chen J. , Song F. , Zheng Z.
Published: September 2006

Abstract:The mitogen‐activated protein kinase (MAPK) cascades play important roles in transmission of extracellular signals to the downstream effector proteins through a mechanism of protein phosphorylation. In this study, we isolated and identified a novel rice MAPK gene,OsBIMK2(Oryzae sativaL. BTH‐Induced MAP Kinase 2). TheOsBIMK2encodes a 506 amino acid protein with molecular weight of 63 kD. The recombinantOsBIMK2expressed inEscherichia colishowed an autophosphorylation activityin vitro.OsBIMK2is a single‐copy gene in the rice genome. Expression ofOsBIMK2was activated upon treatment with benzothiadiazole (BTH), which is capable of inducing disease resistance in rice. Expression of OsBIMK2 was also up‐regulated during early stage after inoculation withMagnaporthe griseain BTH‐treated rice seedlings and during an incompatible interaction betweenM. griseaand a blast‐resistant rice genotype. Over‐expression of the riceOsBIMK2gene in transgenic tobacco resulted in an enhanced disease resistance against tomato mosaic virus and a fungal pathogen,Alternaria alternata. These results suggest thatOsBIMK2plays a role in disease resistance responses.
Molecular Cloning and Expression of a cDNA Encoding a Hybrid Histidine Kinase Receptor in Tropical Periwinkle Catharanthus roseus
Authors: Papon N. , Bremer J. , Vansiri A. , Glévarec G. , Rideau M. , Creche J.
Published: September 2006

Abstract: Signalling pathways involving histidine kinase receptors (HKRs) are widely used by prokaryotes and fungi to regulate a large palette of biological processes. In plants, HKRs are known to be implicated in cytokinin, ethylene, and osmosensing transduction pathways. In this work, a full length cDNA named CrCIK was isolated from the tropical species Catharanthus roseus (L.) G. Don. It encodes a 1205 amino acid protein that belongs to the hybrid HKR family. The deduced amino acid sequence shows the highest homology with AtHK1, an osmosensing HKR in Arabidopsis thaliana. In return, CrCIK protein shares very low identity with the other 10 Arabidopsis HKRs. Southern blot analysis indicates that the CrCIK corresponding gene is either present in multiple copies or has very close homologues in the genome of the tropical periwinkle. The gene is widely expressed in the plant. In C. roseus C20D cell suspension, it is slightly induced after exposure to low temperature, pointing to a putative role in cold‐shock signal transduction.
Colleters in Bathysa nicholsonii K. Schum. (Rubiaceae): Ultrastructure, Secretion Protein Composition, and Antifungal Activity
Authors: de Castro Miguel E. , Moreira Gomes V. , de Oliveira M. A. , da Cunha M.
Published: September 2006

Abstract: Colleters are secretory structures well distributed in many organs of Angiosperms. Ultrastructurally, the colleters secretory cell presents an enhanced endoplasmic reticulum, Golgi apparatus, and mitochondria. Secretion synthesis, transportation, and passage through outer cell wall is poorly characterized. This study characterized the anatomy and ultrastructure of Bathysa nicholsonii (Rubiaceae) colleters and evaluated the presence of protein in the secretion and its antifungal property. Samples were collected and prepared according to usual techniques in light and electron microscopy, electrophoresis, and fungal growth inhibition assay. Colleters are of a standard type, cylindrical and elongated, formed by one secretory epidermal palisade layer, and a central axis formed by parenchymatic cells and a vascular trace. Epidermal cells have dense cytoplasm with abundant ribosome, a nucleus, enhanced endoplasmic reticulum and Golgi apparatus. The outer cell wall presented morphologically distinct layers. The presence of secretory cavities was noted in all outer cell wall extents. Secretion preparations analyzed by SDS‐PAGE showed that B. nicholsonii secretion is a mixture of proteins with molecular masses covering a range of approximately 66 to 24 kDa. This preparation presented an inhibitory effect on the fungi spore growth.
Effects of Cytokinin Production under Two SAG Promoters on Senescence and Development of Tomato Plants
Authors: Swartzberg D. , Dai N. , Gan S. , Amasino R. , Granot D.
Published: September 2006

Abstract: Two promoters of senescence‐associated Arabidopsis genes, SAG12 and SAG13, were used in tomato plants to express IPT that catalyzes the rate‐limiting step in cytokinin biosynthesis. Expression of these heterologous promoters in tomato plants was analyzed using the reporter gene β‐glucuronidase. Both promoters are expressed in tomato leaves in a manner similar to their expression in Arabidopsis plants. The SAG12 promoter is very specific to senescing leaves, whereas the SAG13 promoter is expressed in mature leaves prior to the onset of visible senescence and its expression increases in senescing leaves. Expression of both promoters in tomato tissues other than leaves was very low. IPT expressed under the control of SAG12 and SAG13 promoters PSAG12::IPT and PSAG13::IPT, respectively) resulted in suppression of leaf senescence and advanced flowering, as well as in a slight increase in fruit weight and fruit total soluble solids (TSS). However, expression of PSAG13::IPT also led to stem thickening, short internodal distances and loss of apical dominance. In contrast to the autoregulation of PSAG12::IPT, PSAG13::IPT is expressed at higher levels in mature leaves. This difference is likely due to PSAG13::IPT exhibiting two phases of expression ‐ a senescence‐independent expression prior to the onset of senescence that is not subjected to autoregulation by cytokinin, and enhanced expression throughout senescence which is autoregualted by cytokinin. This moderate different autoregulated behavior of PSAG12::IPT and PSAG13::IPT markedly influenced plant development, emphasizing the biological effects of cytokinin in addition to senescence inhibition.
Correlated Expression of gfp and Bt cry1Ac Gene Facilitates Quantification of Transgenic Hybridization between Brassicas
Authors: Shen B.‐C. , Stewart C. N. , Zhang M.‐Q. , Le Y.‐T. , Tang Z.‐X. , Mi X.‐C. , Wei W. , Ma K.‐P.
Published: September 2006

Abstract: Gene flow from transgenic oilseed rape (Brassica napus) might not be avoidable, thus, it is important to detect and quantify hybridization events with its relatives in real time. Data are presented showing the correlation between genetically linked green fluorescent protein (GFP) with Bacillus thuringiensis (Bt) cry1Ac gene expression in hybrids formed between transgenic B. napus“Westar” and a wild Chinese accession of wild mustard (B. juncea) and hybridization between transgenic B. napus and a conspecific Chinese landrace oilseed rape. Hybrids were obtained either by spontaneous hybridization in the field or by hand‐crossing in a greenhouse. In all cases, transgenic hybrids were selected by GFP fluorescence among seedlings originating from seeds harvested from B. juncea and the Chinese oilseed rape plants. Transgenicity was confirmed by PCR detection of transgenes. GFP fluorescence was easily and rapidly detected in the hybrids under greenhouse and field conditions. Results showed that both GFP fluorescence and Bt protein synthesis decreased as either plant or leaf aged, and GFP fluorescence intensity was closely correlated with Bt protein concentration during the entire vegetative lifetime in hybrids. These findings allow the use of GFP fluorescence as an accurate tool to detect gene‐flow in time in the field and to conveniently estimate Bt cry1Ac expression in hybrids on‐the‐plant.
13C Labelling Reveals Different Contributions of Photoassimilates from Infructescences for Fruiting in Two Temperate Forest Tree Species
Authors: Hoch G. , Keel S. G.
Published: September 2006

Abstract: The pathways of currently fixed carbon in fruit bearing branchlets were investigated in two temperate forest tree species (Carpinus betulus and Fagus sylvatica), which differ in texture of their vegetative infructescence tissues (leaf‐like in Carpinus vs. woody in Fagus). During late spring, 13C pulse‐labelling was conducted on girdled, defoliated, girdled plus defoliated and untreated fruiting branchlets of mature trees in situ, to assess changes in C relations in response to the introduced C source‐sink imbalances. At harvest in early August, 75 ‐ 100 % of the recovered 13C label was bound to infructescences (either fruits or vegetative infructescence tissue), revealing them as the prime C sinks for current photoassimilates. Leaves on girdled branchlets were not stronger labelled than on ungirdled ones in both species, indicating no upregulation of the leaves photosynthetic capacity in response to the prevention of phloemic transport, which was also supported by measurements of light saturated photosynthesis. In contrast, 13C labels tended to be higher after complete defoliation in the vegetative infructescence tissues of Carpinus, suggesting enhanced net photosynthesis of green infructescence parts as compensation for the loss of regular leaves. The total labelling‐derived 13C content of whole infructescences was very similar between foliated and defoliated Carpinus branchlets. Cupulae of Fagus, on the other hand, remained almost unlabelled on defoliated branchlets, indicating the photosynthetic inactivity of this woody infructescence tissue. Consequently, Carpinus still produced relatively high fruit masses on girdled plus defoliated branchlets, while in Fagus fruit development ceased almost completely at this most severe treatment. Our results highlight that green vegetative infructescence tissue assimilates substantial amounts of C and can partly substitute regular leaves as C sources for successful fruit development.
Diversification of CYCLOIDEA‐like TCP Genes in the Basal Eudicot Families Fumariaceae and Papaveraceae s.str.
Authors: Kölsch A. , Gleissberg S.
Published: September 2006

Abstract: CYCLOIDEA‐like genes belong to the TCP family of transcriptional regulators and have been shown to control different aspects of shoot development in various angiosperm lineages, including flower monosymmetry in asterids and axillary meristem growth in monocots. Genes related to the CYC gene from Antirrhinum show independent duplications in both asterids and rosids. However, it remains unclear to what extent this affected the evolution of flower symmetry and shoot branching in these and other eudicot lineages. Here, we show that CYC‐like genes have also undergone duplications in two related Ranunculales families, Fumariaceae and Papaveraceae s.str. These families exhibit morphological diversity in flower symmetry and inflorescence architecture that is potentially related to functions of CYC‐like genes. We present sequences of 14 CYC‐related genes covering 9 genera. Phylogenetic analyses indicate the presence of three clades of CYC‐like genes. Shared motifs in the region between the TCP and R domains of CYC‐like genes between Fumariaceae, Papaveraceae s.str., and Aquilegia (Ranunculaceae) indicate that the observed duplications originated from a single CYC gene present in all Ranunculales. RT□PCR expression data suggest that gene duplication and diversification in Fumariaceae and Papaveraceae s.str. was accompanied by divergence in expression patterns.
Negative strain rate sensitivity in bulk metallic glass and its similarities with the dynamic strain aging effect during deformation
Authors: Dalla Torre Florian H. , Dubach Alban , Siegrist Marco E. , Löffler Jörg F.
Published: September 2006

Detailed investigations were carried out on the deformation behavior of Zr-based monolithic bulk metallic glass and bulk metallic glass matrix composites. The latter, due to splitting and multiplication of shear bands, exhibits larger compressive strains than the former, without significant loss of strength. Serrated flow in conjunction with a negative strain rate sensitivity was observed in both materials. This observation, together with an increase in stress drops with increasing strain and their decrease with increasing strain rate, indicates phenomenologically close similarities with the dynamic strain aging deformation mechanism known for crystalline solids. The micromechanical mechanism of a shear event is discussed in light of these results.
Optoelectronic switches based on diffusive conduction
Authors: Demir Hilmi Volkan , Koklu Fatih Hakan , Yairi Micah B. , Harris James S. , Miller David A. B.
Published: September 2006

We study the process of diffusive conduction that we use in our optoelectronic switches to achieve rapid optical switching (on a picosecond time scale). We present the characteristic Green’s function of the diffusive conduction derived for arbitrary initial conditions. We also report the series solutions of the diffusive conduction obtained for different boundary conditions (V=0 and ∇V=0 along the device contact lines) in different device geometries (rectangular and circular mesas). Using these analytical results, we investigate the effect of boundary conditions on the switching operation and the steady state behavior in optical links. We demonstrate the feasibility of using such diffusive conductive optoelectronic switches to establish optical links in return-to-zero and non-return-to-zero coding schemes. For multichannel optical switching, we discuss possible use of a single optoelectronic switch to accommodate multiple channels at once, with >100 optical channels (with a 2000mm−2 channel density and <10% cross-talk), predicted on a 300×300μm2 mesa with a device switching bandwidth of >50GHz, leading to a 5Tb∕s aggregate transmission in principle. This approach of using multiple parallel channels on a single switch is completely opposite to the traditional idea of arraying many switches. This proposed scheme eliminates the need for on-chip switch integration and the need for the alignment of the optical channels to the integrated individual switches.
Phase stability of La0.5Sr0.5CoO3−y films upon annealing in hydrogen atmosphere
Authors: Rossel C. , Rosová A. , Hušeková K. , Machajdík D. , Fröhlich K.
Published: September 2006

The effect of annealing epitaxial La0.5Sr0.5CoO3−y films in forming gas (FG) mixed with 0.01%, 0.1%, and 1%mol oxygen was investigated using in situ x-ray diffraction at temperatures up to 800°C. The phase transition that occurs at 275°C in pure FG is shifted to higher temperatures by small admixtures of oxygen in FG. Electron diffraction patterns demonstrate that this is a transition into an oxygen-deficient ordered phase with 0,1∕3,0 and 0,2∕3,0 superstructures. The La0.5Sr0.5CoO3−y phase can be recovered by annealing in oxygen at moderate temperatures as long as it has not decomposed at higher temperatures.
Self-assembled InAs quantum wire lasers on (001)InP at 1.6μm
Authors: Suárez F. , Fuster D. , González L. , González Y. , García J. M. , Dotor M. L.
Published: September 2006

In this work, the authors present results on the growth by atomic layer molecular beam epitaxy and characterization of lasers with one and three stacked layers of InAs quantum wires (QWRs) as active zone and aluminum-free waveguides on (001) InP substrates. The separated confinement heterostructure consists of n-p InP claddings and a waveguide formed by short period superlattices of (InP)5∕(GaInAs)4 lattice matched to the InP substrate. The optimum growth conditions (substrate temperature and As and P pressures) have been determined to obtain waveguides with a flat surface in order to get a uniform QWR distribution. Lasing emission is observed at a wavelength of ∼1.66μm up to 270K from 15×3000μm2 devices, with a threshold current density at that temperature of 2kA∕cm2.
Time resolved observation of fracture events in mica crystal using scanning tunneling microscope
Authors: Marchenko A. , Fichou D. , Bonamy D. , Bouchaud E.
Published: September 2006

Scanning tunneling microscope (STM) is used for time resolved nanoscale observation of fracture events in a mica single crystal cleaved in accordance with Obreimoff’s [Proc. R. Soc. London Ser. A 127, 290 (1930)] experiment scheme. The changes in separation between the two parts of the mica crystal caused by crack propagation are seen as variations of the Z coordinate of the STM tip. A simplified geometric model allows to relate this variation to the instantaneous crack speed. Comparative nanoscale observations performed in air and in a chemically inert liquid (n-tetradecane) reveal qualitatively different crack evolutions. The role of the surrounding environment is discussed.
Accurate dependence of gallium nitride thermal conductivity on dislocation density
Authors: Mion C. , Muth J. F. , Preble E. A. , Hanser D.
Published: September 2006

The authors experimentally find that the thermal conductivity of gallium nitride depends critically on dislocation density using the 3-omega technique. For GaN with dislocation densities lower than 106cm−2, the thermal conductivity is independent with dislocation density. The thermal conductivity decreases with a logarithmic dependence for material with dislocation densities in the range of 107–1010cm−2. These results are in agreement with theoretical predictions. This study indicates that the hydride vapor phase epitaxy method offers an attractive route for the formation of semi-insulating gallium nitride with optimal thermal conductivity values around 230W∕mK and very low dislocation density near 5×104cm−2.
Hydrodynamics of shock waves with reflected particles. I. Rankine-Hugoniot relations and stationary solutions
Authors: Dasgupta B. , Burrows R. , Zank G. P. , Webb G. M.
Published: September 2006

In this work we investigate how reflected particles modify the Rankine-Hugoniot (RH) relations in a simple hydrodynamical framework. It is assumed that the ions are specularly reflected by the cross-shock potential. For simplicity, an exactly perpendicular shock is assumed, thus other reflection mechanisms, such as magnetic mirroring, can be neglected. Momentum and energy terms are introduced to model reflected particles at the shock and the RH conditions are examined using a geometrical entropy condition to distinguish the physically relevant states. Although such shocks have some common features with combustion shocks within a narrow range of reflection parameters, for a wide range of reflection parameters, particularly for highly oblique shocks, Chapman-Jouguet solutions do not exist. It is conjectured that these shocks comprise a distinct class. Decelerated solutions of the RH conditions are shown to exist only under specific conditions for shocks with reflected particles. Velocity flows both parallel and oblique to the perpendicular shock (with respect to an upstream magnetic field) are considered and found to be strongly sheared.
Buried microfluidic channel for integrated patch-clamping assay
Authors: Ong Wee-Liat , Kee Jack-Sheng , Ajay Agarwal , Ranganathan Nagarajan , Tang Kum-Cheong , Yobas Levent
Published: September 2006

The authors present a microfluidic device towards an integrated patch-clamping assay. The device replaces conventional glass patch pipette with a buried microfluidic channel on silicon substrate. The microchannel fabrication involves reforming doped glass under heat and pressure, a process, in principle, analogous to the heat-pulling/polishing of glass patch pipettes. Unlike etching substrate, this process leaves a smooth glass surface for seal formation with cell membrane. The microchannel is evolved from a trapped void inside the trench during nonconformal deposition of the doped glass. The results of seal formation with mammalian cells captured at such microchannel opening are presented.
Cylindrical Couette flow of a vapor-gas mixture: Ghost effect and bifurcation in the continuum limit
Authors: Yoshida Hiroaki , Aoki Kazuo
Published: September 2006

A binary mixture of gases is confined in a gap between two coaxial circular cylinders rotating at different angular velocities. One of the component gases is the vapor of the substance that forms the cylinders, so that evaporation or condensation (or sublimation) of the vapor may take place on the surfaces of the cylinders. The other component is a noncondensable gas that neither evaporates nor condenses on the surfaces. Axisymmetric and axially uniform flows (the cylindrical Couette flow) of such a mixture are investigated on the basis of kinetic theory with special interest in the continuum (or fluid-dynamic) limit in which the Knudsen number goes to zero. The fluid-dynamic system that describes the behavior of the mixture is derived by a formal but systematic asymptotic analysis of the Boltzmann system. The resulting system shows some nontrivial phenomena such as the ghost effect and the flow bifurcation. These phenomena are also demonstrated by a Monte Carlo simulation for small Knudsen numbers using the Boltzmann equation.
The phase formation and magnetodielectric property in (1−x)Bi2Fe4O9–xBaO composites
Authors: Wang D. H. , Ong C. K.
Published: September 2006

The composites with composition (1−x)Bi2Fe4O9–xBaO, in which x varied as 0, 0.1, 0.2, and 0.3, were prepared by solid state reaction. X-ray diffraction showed that the content of Bi2Fe4O9 decreased with increasing content of BaO, while multiferroic BiFeO3 and ferrimagnetic BaFe12O19 appeared as the major phases in the composites. The magnetic and ferroelectric behaviors were observed in the composites at room temperature. Variation of dielectric constant (ε) with frequency in the range of 1–100kHz was measured. The maximum value of the magnetodielectric effect ([ε(H)−ε(0)]∕ε(0)) in the presence of magnetic field at room temperature was found to be 5% in the composites with x=0.3, while the applied magnetic field was 7kOe.
Self-heating effects in polycrystalline silicon thin film transistors
Authors: Valletta Antonio , Moroni Alessandro , Mariucci Luigi , Bonfiglietti Alessandra , Fortunato Guglielmo
Published: September 2006

Self-heating effects are investigated in polycrystalline silicon thin film transistors by combining experimental measurements and two-dimensional numerical simulations. From the thermodynamic model the temperature distribution was extracted and found rather uniform along the channel. This allowed the authors to introduce a simplified method to determine the channel temperature when the device is affected by self-heating effects.
Slipping Stokes flow around a slightly deformed sphere
Authors: Senchenko Sergey , Keh Huan J.
Published: September 2006

When a fluid may slip at the surface of a particle, the conventional boundary condition must be modified to incorporate the tangential stress at the surface. Even for the simplest nontrivial shapes of the slip particle, the resulting Stokes problem could not be analytically solved. We present a first attempt to obtain analytical approximations for the resistance relations for a rigid, slightly deformed slip sphere in an unbounded Stokesian flow. To the first order in the small parameter characterizing the deformation, we derive expressions for the hydrodynamic force and torque exerted on the particle, which are found to be in very good agreement with the available numerical results, even in the case in which deformations are not small. The drag force on a spheroid is found to be an either decaying or growing function of the aspect ratio of the particle.
Negative electrodes for lithium ion batteries: Tin/silica nanocomposites obtained from chemical reduction of SnI4 grafted Si-MCM-41
Authors: Santos-Peña Jesús , Sánchez Luis , Cruz-Yusta Manuel , Bach Stéphane , Soudan Patrick , Cuart-Pascual Juan-José , Turnes-Palomino Gemma
Published: September 2006

In this letter, the authors are reporting a time saving and cost-effective procedure to obtain tin-MCM-41 nanocomposites. This particular method simultaneously extracted the surfactant from MCM-41 and grafted the tin precursor creating Si–O–Sn–I bonds in the pore surface. The obtained solid reacted with KBH4, yielding tin containing nanospheres (average diameter of 75nm) embedded in a silica matrix. This nanocomposite electrochemically reacted with lithium forming Li–Sn alloys at 0.6V versus Li. The silica matrix hindered the formation of large Li–Sn aggregates during the reaction. Capacities up to 340mAhg−1 could be provided by the tin/silica nanocomposite at least for 10cycles.
Influence of the electronic energy level broadening on the ionization of atoms in hot and dense plasmas: An average atom model demonstration
Authors: Hou Yong , Jin Fengtao , Yuan Jianmin
Published: September 2006

The broadening of the electronic energy levels of atoms and ions in hot and dense plasmas is taken to be an energy band with a Gaussian distribution of the density of states, which is normalized to ensure that the integration of the density of state over one band is equal to the statistical weight of the corresponding atomic level. The distribution of the bound electrons among the energy bands is determined by the continuum Fermi-Dirac distribution. Within a self-consistent field average atom approach, it has been shown that explicit considerations for the electronic energy level broadening have significant effects on the ionization of the atoms in hot and dense plasmas. The instability of the pressure induced electronic ionization with density, which occurs often in a normal average atom model and is avoided usually by introducing pseudoshape resonance states, disappears naturally. As examples, the density dependence of the average ionization of Al and Au at 1, 10, 100, and 1000eV are presented.
Multiexponential decay autocorrelation function in dynamic light scattering in near-critical ternary liquid mixture
Authors: Ivanov D. A. , Winkelmann J.
Published: September 2006

The dynamic structure factor of a ternary liquid mixture is calculated from the theory of thermodynamic fluctuations with the help of linearized hydrodynamic equations. The theoretical model allows evaluating and classifying the transport properties near a critical solution point of a ternary mixture. In the vicinity of the critical solution point, experimental dynamic light scattering measurements reveal two hydrodynamic relaxation modes with well-separated characteristic relaxation times. From the autocorrelation functions, we can determine two effective diffusivities D1 and D2. As theoretically predicted by a model developed in this work, one of these two modes can be associated with thermal diffusion and the other with mass diffusion. In the special case of an incompressible liquid mixture limit, D1 and D2 are decoupled, becoming thermodiffusion coefficient DT and mutual mass diffusion coefficient Dij. A possible physical meaning of D1 and D2 for a ternary mixture is discussed.
Magneto-flow instability in symmetric field profiles
Authors: Tatsuno T. , Dorland W.
Published: September 2006

Since Rayleigh’s early work on shear-flow driven instabilities in fluids, it has been known that sheared flows are usually unstable only in the presence of an inflection point in the velocity profile. However, in magnetohydrodynamics, there are important instabilities for which no inflection point is required. In tokamak experiments, strongly sheared flows are associated with transport barriers. Instabilities that may limit the height and extent of transport barriers are of central importance. Here, we present linear and nonlinear simulations of an ideal magnetohydrodynamic instability that is driven by sheared flows without inflection points—instead, the instability mechanism requires reversed magnetic shear. Several symmetric field profiles are studied. In general, the instability leads to current profile modifications that push the local minimum value of the safety factor (qmin) upward. The possibility of causing disruption in a relatively slow time scale is pointed out when qmin crosses a rational (especially integral) value. The time scale of the instability is governed by the transit time of the shear flow, which is typically smaller than that of the Alfvén velocity. Characteristics of this instability are compared with recent experimental observations.
The flow of a power-law fluid in the near-wake of a flat plate
Authors: Zhou Min , Ladeinde Foluso , Bluestein Danny
Published: September 2006

The analysis of the near-wake flow downstream of a flat plate is reported in this paper for the case of a non-Newtonian (power-law) constitutive model. To our knowledge, the present paper is the first to address this problem, as previous work on near-wakes has been limited to the use of a Newtonian model. The motivation for this work comes from the biomedical engineering problem of blood flow around the bileaflet of a mechanical heart valve. In the present paper, the series method has been used to calculate the flow near the centerline of the wake, while an asymptotic method has been used for larger distances from the centerline. The effects of power-law inlet conditions on the wake flow are reported for various values of the power-law index n, within the range 0.7≤n≤1.3. The present analysis has been successfully validated by comparing the results for n=1 to the near-wake results by Goldstein [Proc. Cambridge Philos. Soc. 26, 1 (1930)]. We generalized the equations for arbitrary values of n, without any special considerations for n=1. Therefore, the accurate results observed for n=1 validate our procedure as a whole. The first major finding is that a fluid with smaller n develops faster downstream, such that decreasing n leads to monotonically increasing velocities compared to fluids with large n values. Another finding is that the non-Newtonian effects become more significant as the downstream distance increases. Finally, these effects tend to be more pronounced in the vicinity of the wake centerline compared to larger y locations.
Barrier tuning in thin PtSi∕Si contacts
Authors: Ding Yongping , Campbell S. A.
Published: September 2006

Pt Si ∕ Si contacts were studied as a function of thickness. A change of Schottky barrier height up to 100mV from its bulk value was detected when PtSi thickness decreased to 6nm. One explanation is the quantum size effect, generally confirming theoretical predictions. This effect also results in an increase of contact resistance in Ohmic PtSi∕p-Si contacts. Furthermore, the nanoscale PtSi thin layer presented a poor electron screen from the outside contact layer of Al. It was found that for PtSi>50nm, the contact properties of Al∕PtSi∕Si is unchanged by the presence of the Al layer.
All-optical micromechanical chemical sensors
Authors: Stievater T. H. , Rabinovich W. S. , Ferraro M. S. , Papanicolaou N. A. , Boos J. B. , McGill R. A. , Stepnowski J. L. , Houser E. J.
Published: September 2006

The authors describe experimental results from micromechanical resonators coated with a chemoselective polymer that detect chemical vapors from volatile organic compounds using all-optical interrogation. The shift in the resonant frequency of the gold microbeam is read out using photothermal actuation and microcavity interferometry. Response times of less than 5s are achieved for vapor concentrations as low as 60ppm using optical powers of a few megawatts.