Root abundance of maize in conventionally-tilled and zero-tilled soils of Argentina

Maize root growth is negatively affected by compacted layers in the surface (e.g. agricultural traffic) and subsoil layers (e.g. claypans). Both kinds of soil mechanical impedances often coexist in maize fields, but the combined effects on root growth have seldom been studied. Soil physical properties and maize root abundance were determined in three different soils of the Rolling Pampa of Argentina, in conventionally-tilled (CT) and zero-tilled (ZT) fields cultivated with maize. In the soil with a light Bt horizon (loamy Typic Argiudoll, Chivilcoy site), induced plough pans were detected in CT plots at a depth of 0-0.12 m through significant increases in bulk density (1.15 to 1.27 Mg m-3) and cone (tip angle of 60 º) penetrometer resistance (7.18 to 9.37 MPa in summer from ZT to CT, respectively). This caused a reduction in maize root abundance of 40-80 % in CT compared to ZT plots below the induced pans. Two of the studied soils had hard-structured Bt horizons (clay pans), but in only one of them (silty clay loam Abruptic Argiudoll, Villa Lía site) the expected penetrometer resistance increases (up to 9 MPa) were observed with depth. In the other clay pan soil (silty clay loam Vertic Argiudoll, Pérez Millán site), penetrometer resistance did not increase with depth but reached 14.5 MPa at 0.075 and 0.2 m depth in CT and ZT plots, respectively. However, maize root abundance was stratified in the first 0.2 m at the Villa Lía and Pérez Millán sites. There, the hard Bt horizons did not represent an absolute but a relative mechanical impedance to maize roots, by the observed root clumping through desiccation cracks.

Late and post-Hercyniam low temperature veins in the Catalonian Coastal Ranges

Many of the veins enclosed within the Paleozoic basement of the Catalonian Coastal Ranges show severa1 common characteristics: low temperature of formation (between 75 and 200C), the presence of complex polisaline fluids and a certain relationship to the pretriassic paleosurface. Mineralogical composition and age are variable, ranging from Pb-Zn veins with carbonate gangue of late Hercynian age through metal poor fluorite rich veins to barite rich veins of Triasssic age. Mineralizing fluids are not related to late Hercynianmagmatism and deposition took place in active fractures developed either in extensional as in compressive regimes.

Level shifts in a panel data based unit root test : an application to the rate of unemployment

Several unit root tests in panel data have recently been proposed. The test developed by Harris and Tzavalis (1999 JoE) performs particularly well when the time dimension is moderate in relation to the cross-section dimension. However, in common with the traditional tests designed for the unidimensional case, it was found to perform poorly when there is a structural break in the time series under the alternative. Here we derive the asymptotic distribution of the test allowing for a shift in the mean, and assess the small sample performance. We apply this new test to show how the hypothesis of (perfect) hysteresis in Spanish unemployment is rejected in favour of the alternative of the natural unemployment rate, when the possibility of a change in the latter is considered.

New evidence of the real interest rate parity for OECD countries using panel unit root tests with breaks

This paper tests for real interest parity (RIRP) among the nineteen major OECD countries over the period 1978:Q2-1998:Q4. The econometric methods applied consist of combining the use of several unit root or stationarity tests designed for panels valid under cross-section dependence and presence of multiple structural breaks. Our results strongly support the fulfilment of the weak version of the RIRP for the studied period once dependence and structural breaks are accounted for.

Effect of soil-spraying time on root-colonization ability of antagonistic Streptomyces griseoviridis

Selostus: Kasvualustan käsittelyajan vaikutus Streptomyces griseoviridis -antagonistin juurten asutuskykyyn

Changes in anatomy and root cell ultrastructure of soybean genotypes under manganese stress

The deleterious effects of both Mn deficiency and excess on the development of plants have been evaluated with regard to aspects of shoot anatomy, ultrastructure and biochemistry, focusing mainly on the manifestation of visual symptoms. However, there is little information in the literature on changes in the root system in response to Mn supply. The objective of this study was to evaluate the effects of Mn doses (0.5, 2.0 and 200.0 μmol L-1) in a nutrient solution on the anatomy of leaves and roots of the Glycine max (L.) cultivars Santa Rosa, IAC-15 and IAC-Foscarin 31. Visual deficiency symptoms were first observed in Santa Rosa and IAC-15, which were also the only cultivars where Mn-toxicity symptoms were observed. Only in IAC-15, a high Mn supply led to root diameter thickening, but without alteration in cells of the bark, epidermis, exodermis and endodermis. The degree of disorganization of the xylem vessels, in particular the metaxylem, differed in the cultivars. Quantity and shape of the palisade parenchyma cells were influenced by both Mn deficiency and toxicity. A reduction in the number of chloroplasts was observed in the three Mn-deficient genotypes. The anatomical alterations in IAC-15 due to nutritional stress were greater, as expressed in extensive root cell cytoplasm disorganization and increased vacuolation at high Mn doses. The degree of changes in the anatomical and ultrastructural organization of roots and leaves of the soybean genotypes studied differed, suggesting the existence of tolerance mechanisms to different intensities of Mn deficiency or excess.

The effect of substrate on high-temperature annealing of GaN epilayers: Si versus sapphire

We have studied the effects of rapid thermal annealing at 1300¿°C on GaN epilayers grown on AlN buffered Si(111) and on sapphire substrates. After annealing, the epilayers grown on Si display visible alterations with craterlike morphology scattered over the surface. The annealed GaN/Si layers were characterized by a range of experimental techniques: scanning electron microscopy, optical confocal imaging, energy dispersive x-ray microanalysis, Raman scattering, and cathodoluminescence. A substantial Si migration to the GaN epilayer was observed in the crater regions, where decomposition of GaN and formation of Si3N4 crystallites as well as metallic Ga droplets and Si nanocrystals have occurred. The average diameter of the Si nanocrystals was estimated from Raman scattering to be around 3¿nm. Such annealing effects, which are not observed in GaN grown on sapphire, are a significant issue for applications of GaN grown on Si(111) substrates when subsequent high-temperature processing is required.

Neuronal expression of the ubiquitin ligase Nedd4-2 in rat dorsal root ganglia: Modulation in the spared nerve injury model of neuropathic pain.

Neuronal hyperexcitability following peripheral nerve lesions may stem from altered activity of voltage-gated sodium channels (VGSCs), which gives rise to allodynia or hyperalgesia. In vitro, the ubiquitin ligase Nedd4-2 is a negative regulator of VGSC α-subunits (Na(v)), in particular Na(v)1.7, a key actor in nociceptor excitability. We therefore studied Nedd4-2 in rat nociceptors, its co-expression with Na(v)1.7 and Na(v)1.8, and its regulation in pathology. Adult rats were submitted to the spared nerve injury (SNI) model of neuropathic pain or injected with complete Freund's adjuvant (CFA), a model of inflammatory pain. L4 dorsal root ganglia (DRG) were analyzed in sham-operated animals, seven days after SNI and 48h after CFA with immunofluorescence and Western blot. We observed Nedd4-2 expression in almost 50% of DRG neurons, mostly small and medium-sized. A preponderant localization is found in the non-peptidergic sub-population. Additionally, 55.7±2.7% and 55.0±3.6% of Nedd4-2-positive cells are co-labeled with Na(v)1.7 and Na(v)1.8 respectively. SNI significantly decreases the proportion of Nedd4-2-positive neurons from 45.9±1.9% to 33.5±0.7% (p<0.01) and the total Nedd4-2 protein to 44%±0.13% of its basal level (p<0.01, n=4 animals in each group, mean±SEM). In contrast, no change in Nedd4-2 was found after peripheral inflammation induced by CFA. These results indicate that Nedd4-2 is present in nociceptive neurons, is downregulated after peripheral nerve injury, and might therefore contribute to the dysregulation of Na(v)s involved in the hyperexcitability associated with peripheral nerve injuries.

Analysis of S-rich CuIn(S,Se)2 layers for photovoltaic applications: Influence of the sulfurization temperature on the crystalline properties of electrodeposited and sulfurized CuInSe2 precursors

This paper reports the microstructural analysis of S-rich CuIn(S,Se)2 layers produced by electrodeposition of CuInSe2 precursors and annealing under sulfurizing conditions as a function of the temperature of sulfurization. The characterization of the layers by Raman scattering, scanning electron microscopy, Auger electron spectroscopy, and XRD techniques has allowed observation of the strong dependence of the crystalline quality of these layers on the sulfurization temperature: Higher sulfurization temperatures lead to films with improved crystallinity, larger average grain size, and lower density of structural defects. However, it also favors the formation of a thicker MoS2 interphase layer between the CuInS2 absorber layer and the Mo back contact. Decreasing the temperature of sulfurization leads to a significant decrease in the thickness of this intermediate layer and is also accompanied by significant changes in the composition of the interface region between the absorber and the MoS2 layer, which becomes Cu rich. The characterization of devices fabricated with these absorbers corroborates the significant impact of all these features on device parameters as the open circuit voltage and fill factor that determine the efficiency of the solar cells.

Microstructure and secondary phases in coevaporated CuInS2 films: Dependence on growth temperature and chemical composition

The microstructure of CuInS2-(CIS2) polycrystalline films deposited onto Mo-coated glass has been analyzed by Raman scattering, Auger electron spectroscopy (AES), transmission electron microscopy, and x-ray diffraction techniques. Samples were obtained by a coevaporation procedure that allows different Cu-to-In composition ratios (from Cu-rich to Cu-poor films). Films were grown at different temperatures between 370 and 520-°C. The combination of micro-Raman and AES techniques onto Ar+-sputtered samples has allowed us to identify the main secondary phases from Cu-poor films such as CuIn5S8 (at the central region of the layer) and MoS2 (at the CIS2/Mo interface). For Cu-rich films, secondary phases are CuS at the surface of as-grown layers and MoS2 at the CIS2/Mo interface. The lower intensity of the MoS2 modes from the Raman spectra measured at these samples suggests excess Cu to inhibit MoS2 interface formation. Decreasing the temperature of deposition to 420-°C leads to an inhibition in observing these secondary phases. This inhibition is also accompanied by a significant broadening and blueshift of the main A1 Raman mode from CIS2, as well as by an increase in the contribution of an additional mode at about 305 cm-1. The experimental data suggest that these effects are related to a decrease in structural quality of the CIS2 films obtained under low-temperature deposition conditions, which are likely connected to the inhibition in the measured spectra of secondary-phase vibrational modes.

Root system distribution of sugar cane as related to nitrogen fertilization, evaluated by two methods: monolith and probes

Few studies on sugar cane have evaluated the root system of the crop, in spite of its importance. This is mainly due to the difficulty of evaluation and high variability of results. The objective of this study was to develop an evaluation method of the cane root system by means of probes so as to evaluate the mass, distribution and metabolically active roots related to N fertilization at planting. For this purpose, an experiment was conducted in an Arenic Kandiustults with medium texture in Jaboticabal/SP, in a randomized block design with four replications and four treatments: control (without N) and 40, 80 and 120 kg ha-1 of N applied in the form of urea in the planting furrow of the cane variety SP81 3250. One week before harvest, a urea-15N solution was applied at the cane stalk base to detect active metabolism in the root system. Trenches of 1.5 m length and 0.6 m depth were opened between two sugar cane rows for root sampling by two methods: monoliths (0.3, 0.2 and 0.15 m wide, deep and long respectively) taken from the trench wall and by probe (internal diameter 0.055 m). For each method, 15 samples per plot were collected. The roots were separated from the soil in a sieve (2 mm mesh), oven-dried (at 65 ºC) and the dry matter was measured. Root sampling by probes resulted in root mass that did not differ from the evaluation in monoliths, indicating that this evaluation method may be used for sugar cane root mass, although neither the root distribution in the soil profile nor the rhizome mass were efficiently evaluated, due to the small sample volume. Nitrogen fertilization at planting did not result in a greater root accumulation in the sugar cane plant, but caused changes in the distribution of the root system in the soil. The absence of N fertilization led to a better root distribution in the soil profile, with 50, 34 and 16 % in the 0-0.2, 0.2-0.4 and 0.4-0.6 m layers, respectively; in the fertilized treatments the roots were concentrated in the surface layer, with on average 70, 17 and 13 % for the same layers. The metabolically active roots were concentrated in the center of the cane stool, amounting to 40 % of the total root mass, regardless of N fertilization (application of 120 kg ha-1 N or without N).

Fine speckle contrast in InGaAs/InP systems: Influence of layer thickness, missmatch, and growing temperature

This work is focused on the study of the fine speckle contrast present in planar view observations of matched and mismatched InGaAs layers grown by molecular beam epitaxy on InP substrates. Our results provide experimental evidence of the evolution of this fine structure with the mismatch, layer thickness, and growth temperature. The correlation of the influence of all these parameters on the appearance of the contrast modulation points to the development of the fine structure during the growth. Moreover, as growth proceeds, this structure shows a dynamic behavior which depends on the intrinsic layer substrate stress.

Pitfalls in cefepime titration from human plasma: plasma- and temperature-related drug degradation in vitro.

While developing a high-pressure liquid chromatography assay for cefepime in plasma, we observed significant drug degradation at 20 and 37 degrees C but not at 4 degrees C. This plasma-related degradation persisted after protein removal. This warrants caution regarding cefepime assays for pharmacokinetic and pharmacodynamic studies of cefepime in vitro and in vivo.