Search

We show that atomically flat single SrO-terminated SrTiO3(001) substrates can be obtained through simple high-temperature treatment. Amplitude-modulation atomic force microscopy with phase-lag analysis and x-ray photoelectron spectroscopy, have been used to demonstrate that the ratio between the two chemical terminations can be tailored by choosing the annealing time. Moreover, the progressive SrO surface enrichment (up to 100%) is accompanied by a self-assembly process which results in the spatial separation at the nanoscale of both chemical terminations. We further demonstrate that this opens a interesting avenue for selective chemical reaction and growth of oxide nanostructures. [ABSTRACT FROM AUTHOR]

Magnetic hysteresis of ErFeO[sub3] is investigated in the temperature interval between the compensation point T[subcomp] = 46K and erbium ordering transition at T[sub12] = 4.1 K. The shape of the hysteresis loops evolves from rectangular near the compensation point to a double-triangle loops (similar to perminvar loops) near the erbium ordering transition. The evolution of the loop shape explains the peculiar temperature hysteresis observed at constant applied field. [ABSTRACT FROM AUTHOR]

Silicon‐based materials are needed in cutting‐edge technological fields, for which hierarchical porosity and photonic properties help improve performance. In this work, the versatility of several fabrication routes that combine silicon infiltration by chemical vapor deposition (CVD), reactive ion etching (RIE), and carbon calcination, which produce a palette of novel silicon‐based material architectures, is demonstrated. Design strategies are discussed and the main features of the processing steps are addressed to provide a variety of new silicon‐based materials with high morphological versatility and photonic quality. Three‐dimensional hollow carbon opals (HCO) permit control of the porosity of subsequent architectures through the initial silicon infiltration, while open or closed surfaces are achieved primarily as a function of RIE conditions. The composition of derived structures depends on the sequence in which the processes are applied. As a result, pure Si and hybrid C–Si inverse structures can be produced with open or closed spheres in the top layer and with an optional passivation layer. Remarkably, by properly choosing the Si infiltration parameters and the calcination/RIE procedure, final structures are achieved with double‐shell spheres. [ABSTRACT FROM AUTHOR]

The ring nematode genus Xenocriconemella De Grisse and Loof, 1965 comprises only one nominal species, Xenocriconemella macrodora (Taylor, 1936) De Grisse and Loof, 1965. The initial objective of the present study was to investigate the morphological–morphometric and molecular diversity of 28 X. macrodora populations in the Iberian Peninsula associated with tree forests (mainly Quercus spp.). However, a detailed integrative taxonomic analysis (morphological–morphometric and molecular data) from each population and analysis of this data using principal component analysis (PCA) for morphometric data (including these 28 populations and other 25 X. macrodora populations around the world) and molecular and phylogenetic species delimitation methods revealed that X. macrodora forms a species complex. This species complex is composed by species that are morphometricly and morphologically similar, but clearly different at the molecular level. Three new species are described applying integrative taxonomy, namely as Xenocriconemella iberica sp. nov., Xenocriconemella paraiberica sp. nov. and Xenocriconemella pradense sp. nov. However, the molecular diversity of this species in USA and Italy confirmed that additional species are likely present in this species complex, and the diversity of this group may be higher than expected. The study of X. macrodora topotypes can clarify the position of this species using molecular markers under an integrative approach. [ABSTRACT FROM AUTHOR]

Ion beam patterning of a nanoscale ripple surface has emerged as a versatile method of imprinting uniaxial magnetic anisotropy (UMA) on a desired in-plane direction in magnetic films. In the case of ripple patterned thick films, dipolar interactions around the top and/or bottom interfaces are generally assumed to drive this effect following Schlömann's calculations for demagnetizing fields of an ideally sinusoidal surface [E. Schlömann, J. Appl. Phys. 41, 1617 (1970)]. We have explored the validity of his predictions and the limits of ion beam sputtering to induce UMA in a ferromagnetic system where other relevant sources of magnetic anisotropy are neglected: ripple films not displaying any evidence of volume uniaxial anisotropy and where magnetocrystalline contributions average out in a fine grain polycrystal structure. To this purpose, the surface of 100 nm cobalt films grown on flat substrates has been irradiated at fixed ion energy, fixed ion fluency but different ion densities to make the ripple pattern at the top surface with wavelength K and selected, large amplitudes (ω) up to 20 nm so that stray dipolar fields are enhanced, while the residual film thickness t=35-50 nm is sufficiently large to preserve the continuous morphology in most cases. The film-substrate interface has been studied with X-ray photoemission spectroscopy depth profiles and is found that there is a graded silicon-rich cobalt silicide, presumably formed during the film growth. This graded interface is of uncertain small thickness but the range of compositions clearly makes it a magnetically dead layer. On the other hand, the ripple surface rules both the magnetic coercivity and the uniaxial anisotropy as these are found to correlate with the pattern dimensions. Remarkably, the saturation fields in the hard axis of uniaxial continuous films are measured up to values as high as 0.80 kG and obey a linear dependence on the parameter ω2/Λ/t in quantitative agreement with Schlömann's prediction for a surface anisotropy entirely ruled by dipolar interaction. The limits of UMA tuning by a ripple pattern are discussed in terms of the surface local angle with respect to the mean surface and of the onset of ripple detachment. [ABSTRACT FROM AUTHOR]

We present a ferromagnetic resonance study of the dynamic properties of a set of amorphous Fe-B films deposited on Corning Glass® and MgO (001) substrates, either with or without capping. We show that the in plane anisotropy of the MgO grown films contains both uniaxial and biaxial components whereas it is just uniaxial for those grown on glass. The angular dependence of the linewidth strongly differs in terms of symmetry and magnitude depending on the substrate and capping. We discuss the role of the interfaces on the magnetization damping and the generation of the anisotropy. We obtained values of the intrinsic damping parameters comparable to the lowest ones reported for amorphous films of similar compositions. [ABSTRACT FROM AUTHOR]

We present a combined magnetooptic and ferromagnetic resonance study of a series of arrays of single-crystalline Fe stripes fabricated by electron beam lithography on epitaxial Au(001)/Fe(001)/MgO(001) films grown by pulsed laser deposition. The analysis of the films revealed a clear four-fold magnetocrystalline anisotropy, with no significant presence of other anisotropy sources. The use of a large series of arrays, with stripe widths between 140 and 1000 nm and separation between them of either 200 nm or 500 nm, allowed studying their magnetization processes and resonance modes as well as the effects of the dipolar interactions on both. The magnetization processes of the stripes were interpreted in terms of a macrospin approximation, with a good agreement between experiments and calculations and negligible influence of the dipolar interactions. The ferromagnetic resonance spectra evidenced two types of resonances linked to bulk oscillation modes, essentially insensitive to the dipolar interactions, and a third one associated with edge-localized oscillations, whose resonance field is strongly dependent on the dipolar interactions. The ability to produce a high quality, controlled series of stripes provided a good opportunity to achieve an agreement between the experiments and calculations, carried out by taking into account just the Fe intrinsic properties and the morphology of the arrays, thus evidencing the relatively small role of other extrinsic factors. [ABSTRACT FROM AUTHOR]

Graphene functionalization with organics is expected to be an important step for the development of graphene-based materials with tailored electronic properties. However, its high chemical inertness makes difficult a controlled and selective covalent functionalization, and most of the works performed up to the date report electrostatic molecular adsorption or unruly functionalization. We show hereafter a mechanism for promoting highly specific covalent bonding of any amino-terminated molecule and a description of the operating processes. We show, by different experimental techniques and theoretical methods, that the excess of charge at carbon dangling-bonds formed on single-atomic vacancies at the graphene surface induces enhanced reactivity towards a selective oxidation of the amino group and subsequent integration of the nitrogen within the graphene network. Remarkably, functionalized surfaces retain the electronic properties of pristine graphene. This study opens the door for development of graphene-based interfaces, as nano-bio-hybrid composites, fabrication of dielectrics, plasmonics or spintronics. [ABSTRACT FROM AUTHOR]

Dagger and needle nematodes included in the family Longidoridae (viz. Longidorus, Paralongidorus, and Xiphinema) are highly polyphagous plant-parasitic nematodes in wild and cultivated plants and some of them are plant-virus vectors (nepovirus). The mitochondrial (mt) genomes of the dagger and needle nematodes, Xiphinema rivesi, Xiphinema pachtaicum, Longidorus vineacola and Paralongidorus litoralis were sequenced in this study. The four circular mt genomes have an estimated size of 12.6, 12.5, 13.5 and 12.7 kb, respectively. Up to date, the mt genome of X. pachtaicum is the smallest genome found in Nematoda. The four mt genomes contain 12 protein-coding genes (viz. cox1-3, nad1-6, nad4L, atp6 and cob) and two ribosomal RNA genes (rrnL and rrnS), but the atp8 gene was not detected. These mt genomes showed a gene arrangement very different within the Longidoridae species sequenced, with the exception of very closely related species (X. americanum and X. rivesi). The sizes of non-coding regions in the Longidoridae nematodes were very small and were present in a few places in the mt genome. Phylogenetic analysis of all coding genes showed a closer relationship between Longidorus and Paralongidorus and different phylogenetic possibilities for the three Xiphinema species. [ABSTRACT FROM AUTHOR]

We have experimentally characterized the magnetization processes of a square array of micron sized circular antidots lithographed on a Fe(001)/GaAs film with its diagonals along the Fe magnetocrystalline easy axes (100). Both the anisotropy and the angular dependence of the magnetization reversal were measured by means of magnetooptic techniques. The coercivity of the loops along the easy and in-plane hard axes of the array increases approximately 2.5 times with respect to that measured in the continuous film region, and the first order anisotropy constant remains equal to that of bulk Fe. The magnetization reversal takes place in two steps for all the loops measured out of the easy and hard axes. We have simulated the magnetization reversal using two different micromagnetic models. In the first one, assuming that the reversal takes place fully inside the array, we have observed that the reversal nucleates at the magnetic inhomogeneities occurring at the antidot boundaries and resulting from magnetostatic energy minimization. In our second model we artificially introduced a domain wall outside the antidot region that governs the magnetization reversal showing a qualitative agreement with the angular dependence of coercivity. [ABSTRACT FROM AUTHOR]

Morphologial, biochemical, molecular and karyological analyses of different populations and races of the stem and bulb nematode Ditylenchus dipsaci have suggested that it represents a species complex, of which only D. dipsaci sensu stricto and its morphologically larger variant, known as the giant race of the stem and bulb nematode, are plant parasites of economic importance. The present study singles out the giant race from this complex, herein described as a new species named Ditylenchus gigas n. sp., on the basis of morphological and molecular data obtained from several populations collected from broad beans in southern Italy, southern Spain and Lebanon. The new species epithet, which refers to the large body size of the nematode with respect to the normal races, must be considered to be conspecific with the D. dipsaci ‘giant race’ from Fabaceae in recent literature. Morphologically, the new species is characterized by a body size 1Æ5–2 times longer than the ‘normal race’, stylet delicate (11Æ5–13Æ0 lm long) with knobs distinctly sloping backwards, and long post-vulval uterine sac (81–150 lm long). Results of molecular analysis of rDNA sequences including the ITS1-5.8S-ITS2 region, the D2–D3 fragment of the 28S gene, the small 18S subunit, the partial mitochondrial gene for cytochrome c oxidase I (mtCOI), and hsp90 gene sequences, support the new taxonomic species status for the former D. dipsaci giant race from Vicia faba, and clearly distinguish D. gigas n. sp. from D. dipsaci sensu stricto. [ABSTRACT FROM AUTHOR]

Gallium nanoparticles (Ga NPs) are attracting increasing attention because of their appealing physical‐chemical properties. In particular, their mechanical properties play a key role in the implementation of these core‐shell structures on certain applications, such as soft and stretchable electronics. Thus, efforts are being addressed to modulate them mainly by chemical means. In contrast, this study investigates how the mechanical properties of the outer gallium thin oxide shell change when its thickness is increased through a thermal oxidation strategy. Specifically, as‐deposited Ga NPs, as well as those subjected to thermal oxidation at 300 °C for three different times, are studied by performing single‐particle indentations by atomic force microscopy over a wide range of NP radius. This analysis helps to confirm that the Reissner's thin‐shell model for small deformations within the elastic regime is obeyed. From these data, the dependence of the shell stiffness and the Young's modulus of the gallium oxide on the thermal treatment is obtained. It is found that the shell stiffness increases with the annealing time, even by a factor of 50 under prolonged thermal oxidation, while the gallium oxide Young's modulus, close to 30 GPa, does not change significantly. [ABSTRACT FROM AUTHOR]

We report on the effect, on the local magnetization reversal taking place in amorphous Fe80B20 stripes, of the irradiation with nanobeam synchrotron X-ray. That irradiation preserves the amorphous structure and results on the increase of the local coercivity with respect to that measured in a non-irradiated sample, in which the coercivity is mediated by the nucleation-propagation of a single wall. The local coercivity increases in a non-linear way with the width of the irradiated regions when that width is smaller than that of the wall mediating the magnetization switching in the non-irradiated stripe and gets saturated when the irradiated regions dimension is larger than the propagating wall width. We correlate this behavior with the induction at the irradiated regions of a reduction of the local effective anisotropy with respect to the stripe as-lithographed value. From the relationship between the coercivity and the width of the irradiated regions we estimate the local anisotropy reduction in a 25% of that measured in the non-irradiated stripe. [ABSTRACT FROM AUTHOR]

We report on the design and testing of new graphite and graphene oxide‐based extended π‐conjugated synthetic scaffolds for applications in sustainable chemistry transformations. Nanoparticle‐functionalised carbonaceous catalysts for new Fischer Tropsch and Reverse GasWater Shift (RGWS) transformations were prepared: functional graphene oxides emerged from graphite powders via an adapted Hummer's method and subsequently impregnated with uniform‐sized nanoparticles. Then the resulting nanomaterials were imaged by TEM, SEM, EDX, AFM and characterised by IR, XPS and Raman spectroscopies prior to incorporation of Pd(II) promoters and further microscopic and spectroscopic analysis. Newly synthesised 2D and 3D layered nanostructures incorporating carbon‐supported iron oxide nanoparticulate pre‐catalysts were tested, upon hydrogen reduction in situ, for the conversion of CO2 to CO as well as for the selective formation of CH4 and longer chain hydrocarbons. The reduction reaction was also carried out and the catalytic species isolated and fully characterised. The catalytic activity of a graphene oxide‐supported iron oxide pre‐catalyst converted CO2 into hydrocarbons at different temperatures (305, 335, 370 and 405 °C), and its activity compared well with that of the analogues supported on graphite oxide, the 3‐dimensional material precursor to the graphene oxide. Investigation into the use of graphene oxide as a framework for catalysis showed that it has promising activity with respect to reverse gas water shift (RWGS) reaction of CO2 to CO, even at the low levels of catalyst used and under the rather mild conditions employed at atmospheric pressure. Whilst the γ‐Fe2O3 decorated graphene oxide‐based pre‐catalyst displays fairly constant activity up to 405 °C, it was found by GC‐MS analysis to be unstable with respect to decomposition at higher temperatures. The addition of palladium as a promoter increased the activity of the iron functionalised graphite oxide in the RWGS. The activity of graphene oxide supported catalysts was found to be enhanced with respect to that of iron‐functionalised graphite oxide with, or without palladium as a promoter, and comparable to that of Fe@carbon nanotube‐based systems tested under analogous conditions. These results display a significant step forward for the catalytic activity estimations for the iron functionalised and rapidly processable and scalable graphene oxide. The hereby investigated phenomena are of particular relevance for the understanding of the intimate surface morphologies and the potential role of non‐covalent interactions in the iron oxide‐graphene oxide networks, which could inform the design of nano‐materials with performance in future sustainable catalysis applications. [ABSTRACT FROM AUTHOR]

Anatase TiO2 has become a material of great interest for photocatalytic production of hydrogen, environmental purification and solar energy conversion. Among the key parameters boosting the photocatalytic efficiency of the anatase nanoparticles, an increased light absorption to expand its optical response to the visible region, together with an improved charge separation of the photo-generated electrons and holes, can be enumerated. In this work, yellow-coloured, single-phase anatase nanoparticles have been obtained using a simple two-step solvothermal routine which requires no external addition of dopants, nor the use of a harassing/aggressive synthesis atmosphere. The obtained powders display a lowered bandgap (<3.0 eV) and significantly reduce the recombination processes, eventually leading to an improved photocatalytic performance under visible light, as exemplified by an enhanced degradation of phenol. This exceptional response is linked to the presence of intrinsic defects in the yellowish particles and, hence, the specific conditions of the proposed methodology become crucial to produce a propitious TiO2-defective nanomaterial capable of photo-degrade the phenol molecule, in contrast with the lack of photocatalytic activity currently exhibited by commercial photocatalysts under visible light. [ABSTRACT FROM AUTHOR]

We report on the low temperature magnetic behavior of an epitaxially grown multilayer formed by 32 repetitions of a nominal period corresponding to 1 monolayer (ML) Co and 16 ML Ag. The study of the magnetic properties was based on the measurement of the temperature dependencies of the dc magnetization upon field cooling (FC) and zero field cooling (ZFC) and of the ac field real and imaginary parts of the susceptibility. From our results we conclude about the occurrence of i) a well-defined bilayers stacking sequence matching the nominal one, ii) a discontinuous growth in the Co layers resulting on close-to-monodisperse, spherical Co nanoparticles having an average diameter of 1.6 nm, iii) a frequency dependent peak in the temperature dependence of the real part of the ac susceptibility exhibiting a per decade relative temperature variation of 4.5 x 10−2, iv) an applied dc field, Hdc, variation of the temperature at which the irreversibility is detected in the FC/ZFC curves corresponding to the Almeida-Thouless prediction, and v) a critical behavior characterized by a glass-transition temperature slightly below the peak temperatures observed at low frequency in the temperature dependence of the ac susceptibility and a dynamic scaling exponent in the range of the values usually obtained for spin glass systems. From our results we conclude that i) our sample experiences a superspin-glass/paramagnetic phase transition, ii) the interactions mediating the spin glass freezing process are the dipolar ones taking place among the Co particles (creating fields at the average interparticle distance of the order of 8 x 105 A/m) which provide competitiveness that combined with the reduced amount of disorder built-in the Co layers results on frustration. [ABSTRACT FROM AUTHOR]

Three‐dimensional fluorescent graphene frameworks with controlled porous morphologies are of significant importance for practical applications reliant on controlled structural and electronic properties, such as organic electronics and photochemistry. Here we report a synthetically accessible approach concerning directed aromatic stacking interactions to give rise to new fluorogenic 3D frameworks with tuneable porosities achieved through molecular variations. The binding interactions between the graphene‐like domains present in the in situ‐formed reduced graphene oxide (rGO) with functional porphyrin molecules lead to new hybrids via an unprecedented solvothermal reaction. Functional free‐base porphyrins featuring perfluorinated aryl groups or hexyl chains at their meso‐ and β‐positions were employed in turn to act as directing entities for the assembly of new graphene‐based and foam‐like frameworks and of their corresponding coronene‐based hybrids. Investigations in the dispersed phase and in thin‐film by XPS, SEM and FLIM shed light onto the nature of the aromatic stacking within functional rGO frameworks (denoted rGOFs) which was then modelled semi‐empirically and by DFT calculations. The pore sizes of the new emerging reduced graphene oxide hybrids are tuneable at the molecular level and mediated by the bonding forces with the functional porphyrins acting as the "molecular glue". Single crystal X‐ray crystallography described the stacking of a perfluorinated porphyrin with coronene, which can be employed as a molecular model for understanding the local aromatic stacking order and charge transfer interactions within these rGOFs for the first time. This opens up a new route to controllable 3D framework morphologies and pore size from the Ångstrom to the micrometre scale. Theoretical modelling showed that the porosity of these materials is mainly due to the controlled inter‐planar distance between the rGO, coronene or graphene sheets. The host‐guest chemistry involves the porphyrins acting as guests held through π‐π stacking, as demonstrated by XPS. The objective of this study is also to shed light into the fundamental localised electronic and energy transfer properties in these new molecularly engineered porous and fluorogenic architectures, aiming in turn to understand how functional porphyrins may exert stacking control over the notoriously disordered local structure present in porous reduced graphene oxide fragments. By tuning the porosity and the distance between the graphene sheets using aromatic stacking with porphyrins, it is also possible to tune the electronic structure of the final nanohybrid material, as indicated by FLIM experiments on thin films. Such nanohybrids with highly controlled pores dimensions and morphologies open the way to new design and assembly of storage devices and applications incorporating π‐conjugated molecules and materials and their π‐stacks may be relevant towards selective separation membranes, water purification and biosensing applications. [ABSTRACT FROM AUTHOR]

A detailed electronic and microstructural characterization is reported for the LiBH4-MgH2 reactive hydride composite system with and without titanium isopropoxide as additive. Surface characterization by x-ray photoelectron spectroscopy combined to a morphological study by scanning electron microscopy as well as elemental map composition analysis by energy dispersive x-ray emission are presented in this paper for the first time for all sorption steps. Although sorption reactions are not complete at the surface due to the unavoidable superficial oxidation, it has been shown that the presence of the additive is favoring the heterogeneous nucleation of the MgB2 phase. Ti-based phases appear in all the samples for the three sorption steps well dispersed and uniformly distributed in the material. Li-based phases are highly dispersed at the surface while the Mg-based ones appear, either partially covered by the Li-based phases, or forming bigger grains. Ball milling is promoting mixing of phases and a good dispersion of the additive what favors grain refinement and heterogeneous reactions at the interfaces. [ABSTRACT FROM AUTHOR]

Magnetic and structural characteristics of ErFeO3, TmFeO3, and YbFeO3 single crystals were studied over a wide temperature range. Magnetic measurements found that the spin-rotation transitions in all crystals are well described by the earlier proposed theory with no fitting parameters. Additionally, they have shown the absence of the magnetic compensation point in TmFeO3 and a noticeable growth of the c-axis magnetization at low temperatures in TmFeO3 and ErFeO3. The x-ray measurements found no symmetry-lowering lattice distortions during the reorientation. Overall, the measurements cover a wide range of material parameters and demonstrate the generality of the modified mean field theory of the Γ4→Γ24→Γ2 orientation phase transitions in orthoferrites. [ABSTRACT FROM AUTHOR]

The aim of the present study was to evaluate the geographical distribution, infestation degree, and diversity of Potato Cysts Nematode (PCN) in Algeria, including the southern regions. Accurate identification of PCN is essential to determine the appropriate control methods to be used in an Integrated Pest Management program. PCNs were found in forty percent (12 out of thirty) of localities sampled. The average population density of PCN was much higher in the southern regions, compared to the northern regions (9.8 cysts per 100 cm3 vs.4.6 cysts per 100 cm3). The southern potato production areas were more infested with PCN than those of the north (7 from 25 fields in North vs. 5 from 5 fields in the South). Globodera pallida occurred predominantly in the northern region of Algeria, whereas G. rostochiensis occurred predominantly in the southern regions. No mixtures of these species were found in any of the positive studied localities. These species were confirmed by the molecular analysis based on PCR with species-specific primers, ITS-rDNA, and cytochrome b of mtDNA. The low molecular diversity and their phylogenetic association with the European populations of PCN suggest that Algerian populations were probably introduced from Europe, probably by infested seed-potato. [ABSTRACT FROM AUTHOR]

Ferromagnetic resonance (FMR) is used to probe the magnetic properties of Co/Ag superlattices (SLs) with ultrathin Co layers (2–6 Å). Different series of 5×[Ag/Co] multilayers have been grown by molecular beam epitaxy on Si(111) substrates, monitoring the growth by reflection high energy electron diffraction. Cross-section transmission electron microscopy confirms the growth of local areas with the designed SL periodicity, a sharp compositional modulation, well defined Ag–Co interfaces, and a perfect fcc (111) stacking. FMR spectra have been recorded at various polar angles in the 0°–90° range. A single and extremely broad resonance peak is observed in all cases. While SLs with Ag layers thinner than 10 Å exhibit similar values of the perpendicular anisotropy, a clear reduction is observed for samples with Ag layers about 14 Å thick. Possible causes for this change are discussed. [ABSTRACT FROM AUTHOR]

Composites based on an epoxy-novolac matrix and a Cuban henequen fiber reinforcement were investigated. A satisfactory reinforcing effect was observed for a composite material prepared by compression molding at room temperature using long random fiber mats. Tensile and impact experiments were run on the material, and its thermogravimetric analysis was performed. The breaking zone of the specimens tested in tension was examined by an electron sweep microscope. The results obtained are presented graphically and in photographs. [ABSTRACT FROM AUTHOR]

Thick hard-magnetic films have been prepared from NdFeB microparticles dispersed in polymethylmethacrylate solutions. The preparation process included the application of different magnetic fields during the drying of the hard particles dispersion, which resulted on different degrees of out-of-plane macroscopic anisotropy. From the analysis of the temperature dependence of the coercivity of the films it was concluded that the induced macroscopic anisotropy was linked to the occurrence of columnar particle aggregates. [ABSTRACT FROM AUTHOR]

The synergistic effect of three phytochemicals, nonacosan-10-ol, 23a-homostigmast-5-en-3β-ol and cis- and trans-protopinium were assessed in four combinations and three concentrations (5, 50 and 100 ^g ml-1) against Meloidogyne incognita, in vitro and in planta on the tomato cultivar Riogrande. Additionally, an in vitro phytotoxicity test on tomato seedlings was performed with the same phytochemical combinations. A combination of nonacosane-10-ol and 23a-homostigmast-5-en-3β-ol inhibited egg hatching at the highest rate and induced 100.0% mortality of second-stage juvenile (J2) at the concentration of 100 ^g ml-1. The egg hatch inhibition and J2 mortality were positively correlated with an increase in the concentrations of phytochemical as well as with the incubation time. All phytochemical mixtures displayed anematicidal effect against M. incognita in inplanta studies. The combine application of nonacosan-10-ol and 23a-homostigmast-5-en-3β-ol resulted in the highest reduction in nematode parameters (viz., galls, gall index, females g- 1 of root and eggs g-1 of root) and promoted the greatest increase in the plant parameters (such as shoot and root lengths, fresh and dry shoot weights, and number of flowers plant-1) at the highest concentration of 100 ^g ml-1. The phytochemical mixtures did not induce phytotoxic effects on tomato seed germination and seedling growth in in vitro tests. It was concluded from the present study that such phytochemical mixtures offer nematocidal potential in organic vegetable production systems or could be integrated with other management tools as a part of sustainable control strategies for plant-parasitic nematodes. [ABSTRACT FROM AUTHOR]

Direct sublimation of a Cu4Cl4 metal–organic cluster on Cu(110) under ultra-high vacuum allows the formation of ultra-large well-organized metal–organic supramolecular wires. Our results show that the large monomers assemble with each other by π–π interactions connecting dipyrimidine units and are stabilized by the surface. [ABSTRACT FROM AUTHOR]

The formation and dynamics of nanopatterns produced on Si(100) surfaces by 40-keV Ar+ oblique (α = 60°) bombardment with concurrent Fe codeposition have been studied. Morphological and chemical analysis has been performed by ex situ atomic force microscopy, Rutherford backscattering spectrometry, x-ray photoelectron spectroscopy, and scanning and transmission electron microscopies. During irradiation, Fe atoms incorporated into the target surface react with Si to form silicides, a process enhanced at this medium-ion energy range. The silicides segregate at the nanoscale from the early irradiation stages. As the irradiation proceeds, a ripple pattern is formed without any correlation with silicide segregation. From the comparison with the pattern dynamics reported previously for metal-free conditions, it is demonstrated that the metal incorporation alters both the pattern dynamics and the morphology. Although the pattern formation and dynamics are delayed for decreasing metal content, once ripples emerge, the same qualitative pattern of morphological evolution is observed for different metal content, resulting in an asymptotic saw-tooth-like facetted surface pattern. Despite the medium ion energy employed, the nanopatterning process with concurrent Fe deposition can be explained by those mechanisms proposed for low-ion energy irradiations such as shadowing, height fluctuations, silicide formation and segregation, ensuing composition dependent sputter rate, and ion sculpting effects. In particular, the interplay between the ion irradiation and metal flux geometries, differences in sputtering rates, and the surface pattern morphology produces a dynamic compositional patterning correlated with the evolving morphological one. [ABSTRACT FROM AUTHOR]

Pathogenicity and host-parasite relationships in root-knot disease of celery ( Apium graveolens ) caused by Meloidogyne incognita race 1 were studied under glasshouse conditions. Naturally and artificially infected celery cv. D’elne plants showed severe yellowing and stunting, with heavily deformed and damaged root systems. Nematode-induced mature galls were spherical and/or ellipsoidal and commonly contained more than one female, males and egg masses with eggs. Feeding sites were characterized by the development of giant cells that contained granular cytoplasm and many hypertrophied nuclei. The cytoplasm of giant cells was aggregated along their thickened cell walls and consequently the vascular tissues within galls appeared disrupted and disorganized. The relationship between initial nematode population density ( Pi) and growth of celery plants was tested in glasshouse experiments with inoculum levels that varied from 0 to 512 eggs and second-stage juveniles (J2) mL−1 soil. Seinhorst's model y =  m + (1 –  m) zP–T was fitted to height and top fresh weight data of the inoculated and control plants. The tolerance limit with respect to plant height and fresh top weight of celery to M. incognita race 1 was estimated as 0·15 eggs and J2 mL−1 soil. The minimum relative values ( m) for plant height and top fresh weight were 0·37 and 0·35, respectively, at Pi ≥ 16 eggs and J2 mL−1 soil. The maximum nematode reproduction rate ( Pf/Pi) was 407·6 at an initial population density ( Pi) of 4 eggs and J2 mL−1 soil. [ABSTRACT FROM AUTHOR]

While the biology of nitrogen-fixing root nodules has been extensively studied, little is known about the evolutionary events that predisposed legume plants to form symbiosis with rhizobia. We have studied the presence and the expression of two pectic gene families in Medicago, polygalacturonases (PGs) and pectin methyl esterases (PMEs) during the early steps of the Sinorhizobium meliloti– Medicago interaction and compared them with related pollen-specific genes. First, we have compared the expression of MsPG3, a PG gene specifically expressed during the symbiotic interaction, with the expression of MsPG11, a highly homologous pollen-specific gene, using promoter- gus fusions in transgenic M. truncatula and tobacco plants. These results demonstrated that the symbiotic promoter functions as a pollen-specific promoter in the non-legume host. Second, we have identified the presence of a gene family of at least eight differentially expressed PMEs in Medicago. One subfamily is represented by one symbiotic gene ( MtPER) and two pollen-expressed genes ( MtPEF1 and MtPEF2) that are clustered in the M. truncatula genome. The promoter- gus studies presented in this work and the homology between plant PGs, together with the analysis of the PME locus structure and MtPER expression studies, suggest that the symbiotic MsPG3 and MtPER could have as ancestors pollen-expressed genes involved in polar tip growth processes during pollen tube elongation. Moreover, they could have been recruited after gene duplication in the symbiotic interaction to facilitate polar tip growth during infection thread formation. [ABSTRACT FROM AUTHOR]

MsPG3 is a Medicago sativa polygalacturonase gene isolated in our laboratory, its expression during nodule development is associated with the presence of Sinorhizobium meliloti. By RT-PCR and in situ hybridization studies we showed the early induction of MsPG3 expression after inoculation of M. sativa plants with the microsymbiont, suggesting a role for MsPG3 product in the early stages of the interaction. To localize its expression in nodule as well as to characterize the transcriptional regulation of MsPG3, Medicago truncatula transgenic plants containing a 2.7 kb MsPG3 promoter-β-glucuronidase (gus) gene fusion have been obtained. These transgenic plants showed nodule-specific gus expression pattern. Five MsPG3 promoter fragments of different length (from 600 to 92 bp) fused to gus gene have been used to transform M. truncatula in order to determine the promoter regions responsible of this nodule specificity. The region between 600 and 413 bp of MsPG3 promoter was found necessary for transgenic gus expression in nodules. This result was also confirmed in V. hirsuta transgenic `hairy roots'. At position -474/-492 bp upstream of the start codon a sequence was identified that is homologous to the binding site of the transcription factor ENBP1. Our results suggest that MsPG3 expression in nodules could be regulated through this element. [ABSTRACT FROM AUTHOR]

Tip growth is a specialized type of polar growth where new cell wall is deposited in a localized region of the cell, the growing tip. These cells show a characteristic zonation, with a high accumulation of secretory vesicles containing cell wall components at the tip, followed by an organelle-enriched zone. MsPG3 is a Medicago sativa polygalacturonase gene isolated in our laboratory, specifically expressed during the interaction of this plant with its symbiotic partner Sinorhizobium meliloti and which might participate in tip growth processes during symbiosis. We have used MsPG3-GFP fusions to study in vivo protein transport processes and localization during root hair growth. Different MsPG3-GFP fusions were expressed in Medicago truncatula ‘hairy roots’ following a protocol developed for this study and also tested by transient expression in onion epidermal cells. Preferential accumulation of an MsPG3-GFP fusion protein in the tip of the growing root hair at different developmental stages was found, confirming the delivery of MsPG3 to the newly synthesized cell wall. This indicates that this protein may participate in tip growth processes during symbiosis and, in addition, that this fusion could be a useful tool to study this process in plants. [ABSTRACT FROM AUTHOR]

Presents a study which involved the characterization of a Medicago sativa polygalacturonase gene (MsPG3) specifically expressed during symbiosis with Rhizobium meliloti. Methodology used in the study; Localization of MsPG3 expression in root nodule primordia and nodules; Southern blot analysis of Medicago plants; What the MsPG3 gene represents.

The aim of this work is the evaluation of metal phytostabilisation potential of Lupinus luteus inoculated with Bradyrhizobium sp. 750 and heavy metal resistant PGPRs (plant-growth promoting rhizobacteria), for in situ reclamation of multi-metal contaminated soil after a mine spill. Yellow lupines accumulated heavy metals mainly in roots (Cu, Cd and especially Pb were poorly translocated to shoots). This indicates a potential use of this plant in metal phytostabilisation. Furthermore, As accumulation was undetectable. On the other hand, zinc accumulation was 10-100 times higher than all other metals, both in roots and in shoots. Inoculation with Bradyrhizobium sp. 750 increased both biomass and nitrogen content, indicating that nitrogen fixation was effective in soils with moderate levels of contamination. Co-inoculation of lupines with a consortium of metal resistant PGPR (including Bradyrhizobium sp., Pseudomonas sp. and Ochrobactrum cytisi) produced an additional improvement of plant biomass. At the same time, a decrease in metal accumulation was observed, both in shoots and roots, which could be due to a protective effect exerted on plant rhizosphere. Our results indicate the usefulness of L. luteus inoculated with a bacterial consortium of metal resistant PGPRs as a method for in situ reclamation of metal polluted soils., (Copyright (c) 2009 Elsevier B.V. All rights reserved.)