908 resultados para residual fertilization


Relevância:

20.00% 20.00%

Publicador:

Resumo:

The objective of this experiment was to evaluate tiller population density and the dynamics of the tillering process in marandu palisade grass subjected to strategies of rotational stocking management and nitrogen fertilization. Treatments corresponded to combinations between two targets of pre-grazing conditions (sward surface height of 25 and 35 cm) and two rates of nitrogen application (50 and 200 kg ha-1 year-1), and were allocated to experimental units according to a 2 x 2 factorial arrangement in a randomised complete block design, with four replications. The following response variables were studied: initial (TPDi), intermediate (TPDm) and final (TPDf) tiller population density as well as the rates of tiller appearance (TAR) and death (TDR) and the tiller population stability index (SI). TPDi was similar to all treatments, with differences in tiller population density becoming more pronounced as the experiment progressed, resulting in larger TPDf on swards managed at 25 cm pre-grazing height. Tiller death was larger on swards managed at 35 cm, with differences in tiller appearance being recorded only from February 2010 onwards. Stability of tiller population was higher on swards managed at 25 cm pre-grazing height. Overall, there was no effect of nitrogen on the studied variables, and the most adequate grazing strategy corresponded to the pre-grazing height of 25 cm, regardless of the nitrogen application rate used.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Cutting tools with higher wear resistance are those manufactured by powder metallurgy process, which combines the development of materials and design properties, features of shape-making technology and sintering. The annual global market of cutting tools consumes about US$ 12 billion; therefore, any research to improve tool designs and machining process techniques adds value or reduces costs. The aim is to describe the Spark Plasma Sintering (SPS) of cutting tools in functionally gradient materials, to show this structure design suitability through thermal residual stress model and, lastly, to present two kinds of inserts. For this, three cutting tool materials were used (Al2O3-ZrO2, Al2O3-TiC and WC-Co). The samples were sintered by SPS at 1300 °C and 70 MPa. The results showed that mechanical and thermal displacements may be separated during thermal treatment for analysis. Besides, the absence of cracks indicated coherence between experimental results and the residual stresses predicted.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

The presence of heparin and a mixture of penicillamine, hypotaurine, and epinephrine (PHE) solution in the in vitro fertilization (IVF) media seem to be a prerequisite when bovine spermatozoa are capacitated in vitro, in order to stimulate sperm motility and acrosome reaction. The present study was designed to determine the effect of the addition of heparin and PHE during IVF on the quality and penetrability of spermatozoa into bovine oocytes and on subsequent embryo development. Sperm quality, evaluated by the integrity of plasma and acrosomal membranes and mitochondrial function, was diminished (P<0.05) in the presence of heparin and PHE. Oocyte penetration and normal pronuclear formation rates, as well as the percentage of zygotes presenting more than two pronuclei, was higher (P<0.05) in the presence of heparin and PHE. No differences were observed in cleavage rates between treatment and control (P>0.05). However, the developmental rate to the blastocyst stage was increased in the presence of heparin and PHE (P>0.05). The quality of embryos that reached the blastocyst stage was evaluated by counting the inner cell mass (ICM) and trophectoderm (TE) cell numbers and total number of cells; the percentage of ICM and TE cells was unaffected (P>0.05) in the presence of heparin and PHE (P<0.05). In conclusion, this study demonstrated that while the supplementation of IVF media with heparin and PHE solution impairs spermatozoa quality, it plays an important role in sperm capacitation, improving pronuclear formation, and early embryonic development

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Proyecto y presentación del Proyecto Fin de Carrera titulado "DISEÑO DE UN SISTEMA DE CAPTACIÓN DE ENERGÍA RESIDUAL BASADO EN EL ACONDICIONADOR EH300 DE LA EMPRESA ADVANCED LINEAR DEVICES"

Relevância:

20.00% 20.00%

Publicador:

Resumo:

ZusammenfassungDie Bildung von mittelozeanischen Rückenbasalten (MORB) ist einer der wichtigsten Stoffflüsse der Erde. Jährlich wird entlang der 75.000 km langen mittelozeanischen Rücken mehr als 20 km3 neue magmatische Kruste gebildet, das sind etwa 90 Prozent der globalen Magmenproduktion. Obwohl ozeanische Rücken und MORB zu den am meisten untersuchten geologischen Themenbereichen gehören, existieren weiterhin einige Streit-fragen. Zu den wichtigsten zählt die Rolle von geodynamischen Rahmenbedingungen, wie etwa Divergenzrate oder die Nähe zu Hotspots oder Transformstörungen, sowie der absolute Aufschmelzgrad, oder die Tiefe, in der die Aufschmelzung unter den Rücken beginnt. Diese Dissertation widmet sich diesen Themen auf der Basis von Haupt- und Spurenelementzusammensetzungen in Mineralen ozeanischer Mantelgesteine.Geochemische Charakteristika von MORB deuten darauf hin, dass der ozeanische Mantel im Stabilitätsfeld von Granatperidotit zu schmelzen beginnt. Neuere Experimente zeigen jedoch, dass die schweren Seltenerdelemente (SEE) kompatibel im Klinopyroxen (Cpx) sind. Aufgrund dieser granatähnlichen Eigenschaft von Cpx wird Granat nicht mehr zur Erklärung der MORB Daten benötigt, wodurch sich der Beginn der Aufschmelzung zu geringeren Drucken verschiebt. Aus diesem Grund ist es wichtig zu überprüfen, ob diese Hypothese mit Daten von abyssalen Peridotiten in Einklang zu bringen ist. Diese am Ozeanboden aufgeschlossenen Mantelfragmente stellen die Residuen des Aufschmelz-prozesses dar, und ihr Mineralchemismus enthält Information über die Bildungs-bedingungen der Magmen. Haupt- und Spurenelementzusammensetzungen von Peridotit-proben des Zentralindischen Rückens (CIR) wurden mit Mikrosonde und Ionensonde bestimmt, und mit veröffentlichten Daten verglichen. Cpx der CIR Peridotite weisen niedrige Verhältnisse von mittleren zu schweren SEE und hohe absolute Konzentrationen der schweren SEE auf. Aufschmelzmodelle eines Spinellperidotits unter Anwendung von üblichen, inkompatiblen Verteilungskoeffizienten (Kd's) können die gemessenen Fraktionierungen von mittleren zu schweren SEE nicht reproduzieren. Die Anwendung der neuen Kd's, die kompatibles Verhalten der schweren SEE im Cpx vorhersagen, ergibt zwar bessere Resultate, kann jedoch nicht die am stärksten fraktionierten Proben erklären. Darüber hinaus werden sehr hohe Aufschmelzgrade benötigt, was nicht mit Hauptelementdaten in Einklang zu bringen ist. Niedrige (~3-5%) Aufschmelzgrade im Stabilitätsfeld von Granatperidotit, gefolgt von weiterer Aufschmelzung von Spinellperidotit kann jedoch die Beobachtungen weitgehend erklären. Aus diesem Grund muss Granat weiterhin als wichtige Phase bei der Genese von MORB betrachtet werden (Kapitel 1).Eine weitere Hürde zum quantitativen Verständnis von Aufschmelzprozessen unter mittelozeanischen Rücken ist die fehlende Korrelation zwischen Haupt- und Spuren-elementen in residuellen abyssalen Peridotiten. Das Cr/(Cr+Al) Verhältnis (Cr#) in Spinell wird im Allgemeinen als guter qualitativer Indikator für den Aufschmelzgrad betrachtet. Die Mineralchemie der CIR Peridotite und publizierte Daten von anderen abyssalen Peridotiten zeigen, dass die schweren SEE sehr gut (r2 ~ 0.9) mit Cr# der koexistierenden Spinelle korreliert. Die Auswertung dieser Korrelation ergibt einen quantitativen Aufschmelz-indikator für Residuen, welcher auf dem Spinellchemismus basiert. Damit kann der Schmelzgrad als Funktion von Cr# in Spinell ausgedrückt werden: F = 0.10×ln(Cr#) + 0.24 (Hellebrand et al., Nature, in review; Kapitel 2). Die Anwendung dieses Indikators auf Mantelproben, für die keine Ionensondendaten verfügbar sind, ermöglicht es, geochemische und geophysikalischen Daten zu verbinden. Aus geodynamischer Perspektive ist der Gakkel Rücken im Arktischen Ozean von großer Bedeutung für das Verständnis von Aufschmelzprozessen, da er weltweit die niedrigste Divergenzrate aufweist und große Transformstörungen fehlen. Publizierte Basaltdaten deuten auf einen extrem niedrigen Aufschmelzgrad hin, was mit globalen Korrelationen im Einklang steht. Stark alterierte Mantelperidotite einer Lokalität entlang des kaum beprobten Gakkel Rückens wurden deshalb auf Primärminerale untersucht. Nur in einer Probe sind oxidierte Spinellpseudomorphosen mit Spuren primärer Spinelle erhalten geblieben. Ihre Cr# ist signifikant höher als die einiger Peridotite von schneller divergierenden Rücken und ihr Schmelzgrad ist damit höher als aufgrund der Basaltzusammensetzungen vermutet. Der unter Anwendung des oben erwähnten Indikators ermittelte Schmelzgrad ermöglicht die Berechnung der Krustenmächtigkeit am Gakkel Rücken. Diese ist wesentlich größer als die aus Schweredaten ermittelte Mächtigkeit, oder die aus der globalen Korrelation zwischen Divergenzrate und mittels Seismik erhaltene Krustendicke. Dieses unerwartete Ergebnis kann möglicherweise auf kompositionelle Heterogenitäten bei niedrigen Schmelzgraden, oder auf eine insgesamt größere Verarmung des Mantels unter dem Gakkel Rücken zurückgeführt werden (Hellebrand et al., Chem.Geol., in review; Kapitel 3).Zusätzliche Informationen zur Modellierung und Analytik sind im Anhang A-C aufgeführt

Relevância:

20.00% 20.00%

Publicador:

Resumo:

The ability of integrating into a unified percept sensory inputs deriving from different sensory modalities, but related to the same external event, is called multisensory integration and might represent an efficient mechanism of sensory compensation when a sensory modality is damaged by a cortical lesion. This hypothesis has been discussed in the present dissertation. Experiment 1 explored the role of superior colliculus (SC) in multisensory integration, testing patients with collicular lesions, patients with subcortical lesions not involving the SC and healthy control subjects in a multisensory task. The results revealed that patients with collicular lesions, paralleling the evidence of animal studies, demonstrated a loss of multisensory enhancement, in contrast with control subjects, providing the first lesional evidence in humans of the essential role of SC in mediating audio-visual integration. Experiment 2 investigated the role of cortex in mediating multisensory integrative effects, inducing virtual lesions by inhibitory theta-burst stimulation on temporo-parietal cortex, occipital cortex and posterior parietal cortex, demonstrating that only temporo-parietal cortex was causally involved in modulating the integration of audio-visual stimuli at the same spatial location. Given the involvement of the retino-colliculo-extrastriate pathway in mediating audio-visual integration, the functional sparing of this circuit in hemianopic patients is extremely relevant in the perspective of a multisensory-based approach to the recovery of unisensory defects. Experiment 3 demonstrated the spared functional activity of this circuit in a group of hemianopic patients, revealing the presence of implicit recognition of the fearful content of unseen visual stimuli (i.e. affective blindsight), an ability mediated by the retino-colliculo-extrastriate pathway and its connections with amygdala. Finally, Experiment 4 provided evidence that a systematic audio-visual stimulation is effective in inducing long-lasting clinical improvements in patients with visual field defect and revealed that the activity of the spared retino-colliculo-extrastriate pathway is responsible of the observed clinical amelioration, as suggested by the greater improvement observed in patients with cortical lesions limited to the occipital cortex, compared to patients with lesions extending to other cortical areas, found in tasks high demanding in terms of spatial orienting. Overall, the present results indicated that multisensory integration is mediated by the retino-colliculo-extrastriate pathway and that a systematic audio-visual stimulation, activating this spared neural circuit, is able to affect orientation towards the blind field in hemianopic patients and, therefore, might constitute an effective and innovative approach for the rehabilitation of unisensory visual impairments.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

In the last years, sustainable horticulture has been increasing; however, to be successful this practice needs an efficient soil fertility management to maintain a high productivity and fruit quality standards. For this purpose composted organic materials from agri-food industry and municipal solid waste has been used as a source to replace chemical fertilizers and increase soil organic matter. To better understand the influence of compost application on soil fertility and plant growth, we carried out a study comparing organic and mineral nitrogen (N) fertilization in micro propagated plants, potted trees and commercial peach orchard with these aims: 1. evaluation of tree development, CO2 fixation and carbon partition to the different organs of two-years-old potted peach trees. 2. Determination of soil N concentration and nitrate-N effect on plant growth and root oxidative stress of micro propagated plant after increasing rates of N applications. 3. Assessment of soil chemical and biological fertility, tree growth and yield and fruit quality in a commercial orchard. The addition of compost at high rate was effective in increasing CO2 fixation, promoting root growth, shoot and fruit biomass. Furthermore, organic fertilizers influenced C partitioning, favoring C accumulation in roots, wood and fruits. The higher CO2 fixation was the result of a larger tree leaf area, rather than an increase in leaf photosynthetic efficiency, showing a stimulation of plant growth by application of compost. High concentrations of compost increased total soil N concentration, but were not effective in increasing nitrate-N soil concentration; in contrast mineral-N applications increased linearly soil nitrate-N, even at the lowest rate tested. Soil nitrate-N concentration influenced positively plant growth at low rate (60- 80 mg kg-1), whereas at high concentrations showed negative effects. In this trial, the decrease of root growth, as a response to excessive nitrate-N soil concentration, was not anticipated by root oxidative stress. Continuous annual applications of compost for 10 years enhanced soil organic matter content and total soil N concentration. Additionally, high rate of compost application (10 t ha-1 year-1) enhanced microbial biomass. On the other hand, different fertilizers management did not modify tree yield, but influenced fruit size and precocity index. The present data support the idea that organic fertilizers can be used successfully as a substitute of mineral fertilizers in fruit tree nutrient management, since they promote an increase of soil chemical and biological fertility, prevent excessive nitrate-N soil concentration, promote plant growth and potentially C sequestration into the soil.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Paramagnetic triple decker complexes of lanthanides are promising Single Molecule Magnets (SMMs), with many potential uses. Some of them show preferable relaxation behavior, which enables the recording of well resolved NMR spectra. These axially symmetric complexes are also strongly magnetically anisotropic, and this property can be described with the axial component of the magnetic susceptibility tensor, χa. For triple decker complexes with phthalocyanine based ligands, the Fermi˗contact contribution is small. Hence, together with the axial symmetry, the experimental chemical shifts in 1H and 13C NMR spectra can be modeled easily by considering pseudocontact and orbital shifts alone. This results in the determination of the χa value, which is also responsible for molecular alignment and consequently for the observation of residual dipolar couplings (RDCs). A detailed analysis of the experimental 1H-13C and 1H-1H couplings revealed that contributions from RDCs (positive and negative) and from dynamic frequency shifts (negative for all observed couplings) have to be considered. Whilst the pseudocontact shifts depend on the average positions of 1H and 13C nuclei relative to the lanthanide ions, the RDCs are related to the mobility of nuclei they correspond to. This phenomenon allows for the measurement of the internal mobility of the various groups in the SMMs.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Lesions to the primary geniculo-striate visual pathway cause blindness in the contralesional visual field. Nevertheless, previous studies have suggested that patients with visual field defects may still be able to implicitly process the affective valence of unseen emotional stimuli (affective blindsight) through alternative visual pathways bypassing the striate cortex. These alternative pathways may also allow exploitation of multisensory (audio-visual) integration mechanisms, such that auditory stimulation can enhance visual detection of stimuli which would otherwise be undetected when presented alone (crossmodal blindsight). The present dissertation investigated implicit emotional processing and multisensory integration when conscious visual processing is prevented by real or virtual lesions to the geniculo-striate pathway, in order to further clarify both the nature of these residual processes and the functional aspects of the underlying neural pathways. The present experimental evidence demonstrates that alternative subcortical visual pathways allow implicit processing of the emotional content of facial expressions in the absence of cortical processing. However, this residual ability is limited to fearful expressions. This finding suggests the existence of a subcortical system specialised in detecting danger signals based on coarse visual cues, therefore allowing the early recruitment of flight-or-fight behavioural responses even before conscious and detailed recognition of potential threats can take place. Moreover, the present dissertation extends the knowledge about crossmodal blindsight phenomena by showing that, unlike with visual detection, sound cannot crossmodally enhance visual orientation discrimination in the absence of functional striate cortex. This finding demonstrates, on the one hand, that the striate cortex plays a causative role in crossmodally enhancing visual orientation sensitivity and, on the other hand, that subcortical visual pathways bypassing the striate cortex, despite affording audio-visual integration processes leading to the improvement of simple visual abilities such as detection, cannot mediate multisensory enhancement of more complex visual functions, such as orientation discrimination.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Laser Shock Peening (LSP) is a surface enhancement treatment which induces a significant layer of beneficial compressive residual stresses of up to several mm underneath the surface of metal components in order to improve the detrimental effects of the crack growth behavior rate in it. The aim of this thesis is to predict the crack growth behavior in metallic specimens with one or more stripes which define the compressive residual stress area induced by the Laser Shock Peening treatment. The process was applied as crack retardation stripes perpendicular to the crack propagation direction with the object of slowing down the crack when approaching the peened stripes. The finite element method has been applied to simulate the redistribution of stresses in a cracked model when it is subjected to a tension load and to a compressive residual stress field, and to evaluate the Stress Intensity Factor (SIF) in this condition. Finally, the Afgrow software is used to predict the crack growth behavior of the component following the Laser Shock Peening treatment and to detect the improvement in the fatigue life comparing it to the baseline specimen. An educational internship at the “Research & Technologies Germany – Hamburg” department of AIRBUS helped to achieve knowledge and experience to write this thesis. The main tasks of the thesis are the following: •To up to date Literature Survey related to “Laser Shock Peening in Metallic Structures” •To validate the FE model developed against experimental measurements at coupon level •To develop design of crack growth slowdown in Centered Cracked Tension specimens based on residual stress engineering approach using laser peened strip transversal to the crack path •To evaluate the Stress Intensity Factor values for Centered Cracked Tension specimens after the Laser Shock Peening treatment via Finite Element Analysis •To predict the crack growth behavior in Centered Cracked Tension specimens using as input the SIF values evaluated with the FE simulations •To validate the results by means of experimental tests

Relevância:

20.00% 20.00%

Publicador:

Resumo:

During my three academic years, I focused on the effects of N fertilization on growth and function of plants and forest stands. The study had the dual objective of estimating the effects of atmospheric N deposition and evaluating the potential management value of N fertilization itself. In particular, the analysis took into account the changes induced in water use and intrinsic transpiration efficiency (ITE), an aspect often overlooked in world literature but of great importance especially in Mediterranean environment, where the positive effects of N fertilization may be denied by the parallel increased transpiration and exacerbated water stress.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

This thesis will focus on the residual function and visual and attentional deficits in human patients, which accompany damage to the visual cortex or its thalamic afferents, and plastic changes, which follow it. In particular, I will focus on homonymous visual field defects, which comprise a broad set of central disorders of vision. I will present experimental evidence that when the primary visual pathway is completely damaged, the only signal that can be implicitly processed via subcortical visual networks is fear. I will also present data showing that in a patient with relative deafferentation of visual cortex, changes in the spatial tuning and response gain of the contralesional and ipsilesional cortex are observed, which are accompanied by changes in functional connectivity with regions belonging to the dorsal attentional network and the default mode network. I will also discuss how cortical plasticity might be harnessed to improve recovery through novel treatments. Moreover, I will show how treatment interventions aimed at recruiting spared subcortical pathway supporting multisensory orienting can drive network level change.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

This thesis work encloses activities carried out in the Laser Center of the Polytechnic University of Madrid and the laboratories of the University of Bologna in Forlì. This thesis focuses on the superficial mechanical treatment for metallic materials called Laser Shock Peening (LSP). This process is a surface enhancement treatment which induces a significant layer of beneficial compressive residual stresses underneath the surface of metal components in order to improve the detrimental effects of the crack growth behavior rate in it. The innovation aspect of this work is the LSP application to specimens with extremely low thickness. In particular, after a bibliographic study and comparison with the main treatments used for the same purposes, this work analyzes the physics of the operation of a laser, its interaction with the surface of the material and the generation of the surface residual stresses which are fundamentals to obtain the LSP benefits. In particular this thesis work regards the application of this treatment to some Al2024-T351 specimens with low thickness. Among the improvements that can be obtained performing this operation, the most important in the aeronautic field is the fatigue life improvement of the treated components. As demonstrated in this work, a well-done LSP treatment can slow down the progress of the defects in the material that could lead to sudden failure of the structure. A part of this thesis is the simulation of this phenomenon using the program AFGROW, with which have been analyzed different geometric configurations of the treatment, verifying which was better for large panels of typical aeronautical interest. The core of the LSP process are the residual stresses that are induced on the material by the interaction with the laser light, these can be simulated with the finite elements but it is essential to verify and measure them experimentally. In the thesis are introduced the main methods for the detection of those stresses, they can be mechanical or by diffraction. In particular, will be described the principles and the detailed realization method of the Hole Drilling measure and an introduction of the X-ray Diffraction; then will be presented the results I obtained with both techniques. In addition to these two measurement techniques will also be introduced Neutron Diffraction method. The last part refers to the experimental tests of the fatigue life of the specimens, with a detailed description of the apparatus and the procedure used from the initial specimen preparation to the fatigue test with the press. Then the obtained results are exposed and discussed.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Laser Shock Peening (LSP) is a technological process used to improve mechanical properties in metallic components. When a short and intense laser pulse irradiates a metallic surface, high pressure plasma is generated on the treated surface; elasto-plastic waves, then, propagate inside the target and create plastic strain. This surface treatment induces a deep compressive residual stresses field on the treated area and through the thickness; such compressive residual stress is expected to increase the fatigue resistance, and reduce the detrimental effects of corrosion and stress corrosion cracking.