Si3N4 single-crystal nanowires grown from silicon micro- and nanoparticles near the threshold of passive oxidation

A simple and most promising oxide-assisted catalyst-free method is used to prepare silicon nitride nanowires that give rise to high yield in a short time. After a brief analysis of the state of the art, we reveal the crucial role played by the oxygen partial pressure: when oxygen partial pressure is slightly below the threshold of passive oxidation, a high yield inhibiting the formation of any silica layer covering the nanowires occurs and thanks to the synthesis temperature one can control nanowire dimensions

Green manure incorporation timing for organically grown broccoli

The objective of this work was to determine the effect of incorporation timing of the velvet bean (Stizolobium cinereum) (GM) on both organic broccoli yield and N status. Mineral N content in the soil, biologically fixed N recovery by broccoli, GM biomass decomposition and N release kinetics were also determined. Plots were fertilized with 12 Mg ha-1 of organic compost and received GM either at 0, 15, 30 or 45 days after transplant. Other treatments were compost (12 or 25 Mg ha-1), GM, mineral fertilizers and control (no fertilizer). The data were collected in four completely randomized blocks. GM decomposition increased mineral N content in soil as rapidly as mineral fertilizer or the supply of 25 Mg ha-1 of compost. The N half-life in GM (24 days) is smaller than the mass half-life (35 days) and the biological fixation contributed with 23.6% of N present in the aboveground biomass of broccoli. The result suggests a higher synchrony between the crop relative growth rate and N release from the GM when incorporated at crop early growth stage. The incorporation of GM until 15 days after transplanting replaces 50% of the highest compost dose, without yield loss.

Red clover grown in a mixture with grasses : yield, persistence and dynamics of quality characteristics

Selostus: Puna-apilan pysyvyys apila-heinänurmessa sekä seosnurmen satoisuus ja laadun muutokset erilaisissa kasvuoloissa

Environmental and genetic variation of isoflavone content of soybean seeds grown in Brazil

The objective of this work was to evaluate isoflavone concentrations in seeds of different Brazilian soybean cultivars grown in a range of locations and environmental conditions in Brazil. Seeds of 233 cultivars grown in Ponta Grossa, PR, Brazil, during the 2001/2002 soybean season, and of 22 cultivars sown in different locations of Brazilian Northeast, Southeast on South regions were analyzed for total isoflavones, including daidzin, glycitin, genistin and acetylgenistin. The total isoflavones ranged from 12 mg 100 g-1 (cv. Embrapa 48) to 461 mg 100 g-1 (cv. CS 305) among the 233 cultivars grown in Ponta Grossa, and the differences among them are due to genetic effects since all cultivars were grown and collected at the same locatation and year. This is an indication of the possibility of breeding for isoflavone content. Differences in isoflavone content observed in the cultivars grown in different locations permit the selection of locations for optimum isoflavone content (low or high), depending on the uses of soybean. In the Northeast region (5-8°S), higher concentrations of total isoflavones were observed at São Raimundo das Mangabeiras (232 mg 100 g-1) and Tasso Fragoso (284 mg 100 g-1) municipalities, and in the South (23-30°S), isoflavones were higher in Guarapuava, Canoinhas, Vacaria and Campos Novos municipalities, ranging from 130 to 409 mg 100 g-1.

Leaf mineral composition of grafted eggplant grown in soil infested with Verticillium and root-knot nematodes

The objective of this work was to determine differences in leaf mineral composition between ungrafted and grafted onto (Solanum torvum) eggplant (Solanum melongena), cultivars 'Faselis' and 'Pala', grown in a soil infested with Verticillium dahliae and Meloidogyne incognita, or in a noninfested soil. Grafting increased leaf P and Mn concentrations, and decreased N concentrations, in both soils. Grafting also enhanced leaf Ca concentration of 'Pala', but it did not affect that of 'Faselis' depending on the cropping year. Leaf Mg concentration of grafted plants in infested soil was lower than that of ungrafted ones in noninfested soil. Results showed that, under the same fertilization program, the grafted 'Faselis' plants used the nutrients more efficiently than the 'Pala' ones. Use of S. torvum as a rootstock for 'Faselis' resulted in an effective protection against multiple pathogen infestation. Fertilization may be necessary when grafted 'Faselis' plants are grown in a soil infested with the pathogens, since grafting and infestation generally decrease leaf N, Mg, Ca and Fe concentrations, either by reducing the nutrient concentrations directly or by increasing leaf Mn concentration.

Investigations of GaAs based heterostructures for spintronics

In the present work are reported investigations of structural, magnetic and electronic properties of GaAs/Ga1-xInxAs/GaAs quantum wells (QW) having a 0.5 - 1.8 monolayer thick Mn layer, separated from the quantum well by a 3 nm thick spacer. The structure of the samples is analyzed in details by photoluminescence and high-resolution X-ray difractometry and reflectometry, confirming that Mn atoms are practically absent from the QW. Transport properties and crystal structure are analyzed for the first time for this type of QW structures with so high mobility. Observedconductivity and the Hall effect in quantizing magnetic fields in wide temperature range, defined by transport of holes in the quantum well, demonstrate properties inherent to ferromagnetic systems with spin polarization of charge carriersin the QW. Investigation of the Shubnikov ¿ de Haas and the Hall effects gave the possibility to estimate the energy band parameters such as cyclotron mass andFermi level and calculate concentrations and mobilities of holes and show the high-quality of structures. Magnetic ordering is confirmed by the existence of the anomalous Hall effect.

Variation of grain nitrogen content in relation with grain yield in old and modern Spanish wheats grown under a wide range of agronomic conditions in a Mediterranean region

Wheat yield and grain nitrogen concentration (GNC; mg N/g grain) are frequently negatively correlated. In most growing conditions, this is mainly due to a feedback process between GNC and the number of grains/m2. In Mediterranean conditions, breeders may have produced cultivars with conservative grain set. The present study aimed at clarifying the main physiological determinants of grain nitrogen accumulation (GNA) in Mediterranean wheat and to analyse how breeding has affected them. Five field experiments were carried out in north-eastern Spain in the 2005/06 and 2006/ 07 growing seasons with three cultivars released at different times and an advanced line. Depending on the experiment, source-sink ratios during grain filling were altered by reducing grain number/m2 either through pre-anthesis shading (unshaded control or 0.75 shading only between jointing and anthesis) or by directly trimming the spikes after anthesis and before the onset of the effective grain filling period (un-trimmed control or spikes halved 7–10 days after anthesis). Grain nitrogen content (GN content ; mg N/grain) decreased with the year of release of the genotypes. As the number of grains/m2 was also increased by breeding there was a clear dilution effect on the amount of nitrogen allocated to each grain. However, the increase in GN content in old genotypes did not compensate for the loss in grain nitrogen yield (GNY) due to the lower number of grains/m2. GN content of all genotypes increased (increases ranged from 0.13 to 0.40 mg N/grain, depending on experiment and genotype) in response to the post-anthesis spike trimming or pre-anthesis shading. The degree of source-limitation for GNA increased with the year of release of the genotypes (and thus with increases in grain number/m2) from 0.22 (mean of the four manipulative experiments) in the oldest cultivar to 0.51 (mean of the four manipulative experiments) in the most modern line. It was found that final GN content depended strongly on the source-sink ratio established at anthesis between the number of grains set and the amount of nitrogen absorbed at this stage. Thus, Mediterranean wheat breeding that improved yield through increases in grain number/m2 reduced the GN content by diluting a rather limited source of nitrogen into more grains. This dilution effect produced by breeding was further confirmed by the reversal effect produced by grain number/m2 reductions due to either pre-anthesis shading or post-anthesis spike trimming.

Studies on grain boundaries in nanocrystalline silicon grown by Hot-Wire CVD

The use of a tantalum wire in hot-wire chemical vapour deposition (HWCVD) has allowed the deposition of dense nanocrystalline silicon at low filament temperatures (1550 °C). A transition in the crystalline preferential orientation from (2 2 0) to (1 1 1) was observed around 1700 °C. Transmission electron microscopy (TEM) images, together with secondary ion mass spectrometry (SIMS) measurements, suggested that no oxidation occurred in materials obtained at low filament temperature due to the high density of the tissue surrounding grain boundaries. A greater concentration of SiH 3 radicals formed at these temperatures seemed to be responsible for the higher density.

Alterations in growth and canopy architecture among dwarf, semidwarf and tall oat lines grown under northern conditions

Selostus: Korkeudeltaan eri tyyppisten kauralinjojen kasvu ja sadontuotto pohjoisissa viljelyoloissa

Spectroscopic ellipsometry study of the In1-x Gax Asy P1-y / InP Heterojunctions grown by metalorganic chemical-vapor deposition

The dielectric functions of InP, In0.53Ga0.47As, and In0.75Ga0.25As0.5P0.5 epitaxial layers have been measured using a polarization modulation spectroscopic ellipsometer in the 1.5 to 5.3 eV region. The oxide removal procedure has been carefully checked by comparing spectroscopic ellipsometry and x ray photoelectron spectroscopy measurements. These reference data have been used to investigate the structural nature of metalorganic chemical vapor deposition grown In0.53Ga0.47As/InP and In0.75Ga0.25As0.5P0.5/InP heterojunctions, currently used for photodiodes and laser diodes. The sharpness of the interfaces has been systematically compared for the two types of heterojunctions: In1 xGaxAsy/InP and InP/In1 xGaxAsyP1 y. The sharpest interface is obtained for InP growth on In0.75Ga0.25As0.5P0.5 where the interface region is estimated to be (10±10) Å thick. The importance of performing in situ SE measurements is emphasized.

Properties of amorphous silicon thin films grown in square wave modulated silane rf discharges.

Hydrogenated amorphous silicon (a‐Si:H) thin films have been obtained from pure SiH4 rf discharges by using the square wave modulation (SQWM) method. Film properties have been studied by means of spectroellipsometry, thermal desorption spectrometry, photothermal deflection spectroscopy and electrical conductivity measurements, as a function of the modulation frequency of the rf power amplitude (0.2-4000 Hz). The films deposited at frequencies about 1 kHz show the best structural and optoelectronic characteristics. Based upon the experimental results, a qualitative model is presented, which points up the importance of plasma negative ions in the deposition of a‐Si:H from SQWM rf discharges through their influence on powder particle formation.

Highly textured Sr, Nb, co-doped BiFeO3 thin films grown on SrRuO3/Si substrates by rf-sputtering

In this study, (011)-highly oriented Sr, Nb co-doped BiFeO3 (BFO) thin films were successfully grown on SrRuO3/Si substrates by rf-magnetron sputtering. The presence of parasite magnetic phases was ruled out based on the high resolution x-ray diffraction data. BFO films exhibited a columnar-like grain growth with rms surface roughness values of 5.3 nm and average grain sizes of 65-70 nm for samples with different thicknesses. Remanent polarization values (2Pr) of 54 lC cm 2 at room temperature were found for the BFO films with a ferroelectric behavior characteristic of an asymmetric device structure. Analysis of the leakage mechanisms for this structure in negative bias suggests Schottky injection and a dominant Poole-Frenkel trap-limited conduction at room temperature. Oxygen vacancies and Fe3þ/Fe2þ trap centers are consistent with the surface chemical bonding states analysis from x-ray photoelectron spectroscopy data. The (011)-BFO/ SrRuO3/Si film structure exhibits a strong magnetic interaction at the interface between the multiferroic film and the substrate layer where an enhanced ferromagnetic response at 5 K was observed. Zero-field cooled (ZFC) and field cooled (FC) magnetization curves of this film system revealed a possible spin glass behavior at spin freezing temperatures below 30 K depending on the BFO film thickness.

Leaf nutritional levels in peach and nectarine grown in subtropical climate

The study evaluated the leaf nutritional levels of peach and nectarine trees under subtropical climate in order to improve the fertilization practices. The experiment was carried out in São Paulo state University, Botucatu, São Paulo State, Brazil. The experimental design consisted of subdivided plots, in which plots corresponded to cultivars and subplots to the leaf sample periods. The evaluated peach cultivars were: Marli, Turmalina, Precocinho, Jubileu, Cascata 968, Cascata 848, CP 951C, CP 9553CYN, and Tropic Beauty, and that of nectarine was 'Sun Blaze'. The sample periods were: after harvest, plants in vegetative period; dormancy; beginning of flowering and fruiting (standard sample). Results indicated significant variations in the levels of N, P, K, Ca, Mg, S, B, Cu, Fe, Mn and Zn for the sampling period and in N, Ca, Mg, S, B, Fe and Mn levels for the cultivars.

Production and quality of Anacardium othonianum Rizz. seedlings grown in different substrates

This study aimed to evaluate the effect of substrate on growth, emergence, nutrition, and quality of Anacardium othonianum Rizz. (cerrado cashew tree) seedlings. The experiment was conducted in a greenhouse at the Plant Tissue Culture Laboratory on the Rio Verde campus. The following substrates were used: 1) Bioplant®, 2) Mecplant® (MP) + carbonized rice husk (CRH) (7:3), 3) fine-grained vermiculite (FGV), 4) FGV+CRH (3:1), 5) FGV+CRH (1:1), 6) FGV+CRH (1:3), and 7) sugarcane bagasse (SB) + sugarcane mill filter cake (FC) (3:2). Emerged seedlings were counted at 2-day intervals for 38 days following emergence of the first seedling. At 39, 64, and 89 days after seeding (DAS), the following variables were measured: stem length (SL), stem diameter (SD), and number of leaves (NL). Accumulated dry weight, quality indices, and leaf macro- and micronutrient levels were determined at 89 DAS. Plants grown in the FGV and FGV+CFH (1:3) substrates had shorter stem lengths than the plants grown in other substrates. Increases in seedling growth were smaller between 64 and 89 DAS compared to the initial period of the experiment. The highest leaf N concentrations were found in the SB+FC substrate treatment group; P and K concentrations were higher for the MP+CRH (7:3), SB+FC, and Bioplant® treatments; and Ca levels were higher for the SB+FC and MP+CRH (7:3) substrate treatments. The MP+CRH (7:3) substrate treatment group had the highest leaf B and Mn micronutrient concentrations, and plants from the Bioplant® substrate group had the highest leaf B micronutrient content. Mg, S, Cu, Zn, and Fe concentrations did not differ among the different substrates. The plant traits that differed most among the treatments included stem length for the FGV and FGV+CRH (1:3) substrate groups and leaf nutrient concentrations, which were higher for the SB+FC group followed by the MP+CRH and Bioplant® treatments.

Growth and production of irrigated vitória pineapple grown in semi-arid conditions

This study aimed to evaluate the growth characteristics of irrigated Vitória pineapple plants grown in semi-arid conditions and determine its developmental stages based on those characteristics. It was used a randomized block design with four replicates. The experimental treatments were: plant harvest at 270, 330, 390, 450, 510, 570, 690, 750, and 810 days after planting (DAP). The following variables were determined: plant height, stem diameter, D-leaf length, D-leaf fresh and dry mass, biomass production of plants and plant parts (organs), and vegetative biomass. Five phenological stages are proposed based on vegetative biomass production: < 20% biomass production (V1); 21-40% (V2); 41-60% (V3); 61-80% (V4); and > 80% (V5). The maximum growth rate for plant height, D-leaf length, and stem diameter was observed at the end of the phenological stage V1 (390-411 DAP), and at the end of stage V5 these plant traits had average values of 106, 82, and 7 cm, respectively. The maximum biomass accumulation rates were observed at stages V4 and V5, resulting in a final fruit yield and total fresh biomass of 72 t ha-1 and 326 t ha-1, respectively. Finally, we estimated that 80% of the accumulated biomass may remain in the field after fruit and slip harvest, and could be incorporated as plant residue into the soil.