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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
531

Short-term Statistics Of Wind Waves Around The Turkish Coast

Akbasoglu, Sinan 01 January 2004 (has links) (PDF)
In this thesis, the wind-wave records obtained at three locations along the Turkish coasts (Alanya, Dalaman and Hopa) are analyzed. Probability distributions of individual wave characteristics (wave height, wave period and wave steepness) are obtained and compared with the model distributions. Goodness of fit of the observed distributions is checked by Chi-square test and Kolmogorov-Smirnov tests. Joint probability distribution of individual wave heights and periods is also studied and compared with the theoretical distributions. The relationships among various statistical wave height parameters and statistical wave period parameters are investigated and compared with the theoretical and reported values.
532

Neural Network Prediction Of Tsunami Parameters In The Aegean And Marmara Seas

Erdurmaz, Muammer Sercan 01 July 2004 (has links) (PDF)
Tsunamis are characterized as shallow water waves, with long periods and wavelengths. They occur by a sudden water volume displacement. Earthquake is one of the main reasons of a tsunami development. Historical data for an observation period of 3500 years starting from 1500 B.C. indicates that approximately 100 tsunamis occurred in the seas neighboring Turkey. Historical earthquake and tsunami data were collected and used to develop two artificial neural network models to forecast tsunami characteristics for future occurrences and to estimate the tsunami return period. Artificial Neural Network (ANN) is a system simulating the human brain learning and thinking behavior by experiencing measured or observed data. A set of artificial neural network is used to estimate the future earthquakes that may create a tsunami and their magnitudes. A second set is designed for the estimation of tsunami inundation with relation with the tsunami intensity, the earthquake depth and the earthquake magnitude that are predicted by the first set of neural networks. In the case study, Marmara and Aegean regions are taken into consideration for the estimation process. Return periods including the last occurred earthquake in the Turkish seas, which was the izmit (Kocaeli) Earthquake in 1999, were utilized together with the average earthquake depths calculated for Marmara and Aegean regions for the prediction of the earthquake magnitude that may create a tsunami in the stated regions for various return periods of 1-100 years starting from the year of 2004. The obtained earthquake magnitudes were used together with tsunami intensities and earthquake depth to forecast tsunami wave height at the coast. It is concluded that, Neural Networks predictions were a satisfactory first step to implement earthquake parameters such as depth and magnitude, for the average tsunami height on the shore calculations.
533

The genetic basis of human height : the role of estrogen

Carter, Shea L. January 2008 (has links)
Height is a complex physical trait that displays strong heritability. Adult height is related to length of the long bones, which is determined by growth at the epiphyseal growth plate. Longitudinal bone growth occurs via the process of endochondral ossification, where bone forms over the differentiating cartilage template at the growth plate. Estrogen plays a major role in regulating longitudinal bone growth and is responsible for inducing the pubertal growth spurt and fusion of the epiphyseal growth plate. However, the mechanism by which estrogen promotes epiphyseal fusion is poorly understood. It has been hypothesised that estrogen functions to regulate growth plate fusion by stimulating chondrocyte apoptosis, angiogenesis and bone cell invasion in the growth plate. Another theory has suggested that estrogen exposure exhausts the proliferative capacity of growth plate chondrocytes, which accelerates the process of chondrocyte senescence, leading to growth plate fusion. The overall objective of this study was to gain a greater understanding of the molecular mechanisms behind estrogen-mediated growth and height attainment by examining gene regulation in chondrocytes and the role of some of these genes in normal height inheritance. With the heritability of height so well established, the initial hypothesis was that genetic variation in candidate genes associated with longitudinal bone growth would be involved in normal adult height variation. The height-related genes FGFR3, CBFA1, ER and CBFA1 were screened for novel polymorphisms using denaturing HPLC and RFLP analysis. In total, 24 polymorphisms were identified. Two SNPs in ER (rs3757323 C>T and rs1801132 G>C) were strongly associated with adult male height and displayed an 8 cm and 9 cm height difference between homozygous genotypes, respectively. The TC haplotype of these SNPs was associated with a 6 cm decrease in height and remarkably, no homozygous carriers of the TC haplotype were identified in tall subjects. No significant associations with height were found for polymorphisms in the FGFR3, CBFA1 or VDR genes. In the epiphyseal growth plate, chondrocyte proliferation, matrix synthesis and chondrocyte hypertrophy are all major contributors to long bone growth. As estrogen plays such a significant role in both growth and final height attainment, another hypothesis of this study was that estrogen exerted its effects in the growth plate by influencing chondrocyte proliferation and mediating the expression of chondrocyte marker genes. The examination of genes regulated by estrogen in chondrocyte-like cells aimed to identify potential regulators of growth plate fusion, which may further elucidate mechanisms involved in the cessation of linear growth. While estrogen did not dramatically alter the proliferation of the SW1353 cell line, gene expression experiments identified several estrogen regulated genes. Sixteen chondrocyte marker genes were examined in response to estrogen concentrations ranging from 10-12 M to 10-8 M over varying time points. Of the genes analysed, IHH, FGFR3, collagen II and collagen X were not readily detectable and PTHrP, GHR, ER, BMP6, SOX9 and TGF1 mRNAs showed no significant response to estrogen treatments. However, the expression of MMP13, CBFA1, BCL-2 and BAX genes were significantly decreased. Interestingly, the majority of estrogen regulated genes in SW1353 cells are expressed in the hypertrophic zone of the growth plate. Estrogen is also known to regulate systemic GH secretion and local GH action. At the molecular level, estrogen functions to inhibit GH action by negatively regulating GH signalling. GH treated SW1353 cells displayed increases in MMP9 mRNA expression (4.4-fold) and MMP13 mRNA expression (64-fold) in SW1353 cells. Increases were also detected in their respective proteins. Treatment with AG490, an established JAK2 inhibitor, blocked the GH mediated stimulation of both MMP9 and MMP13 mRNA expression. The application of estrogen and GH to SW1353 cells attenuated GH-stimulated MMP13 levels, but did not affect MMP9 levels. Investigation of GH signalling revealed that SW1353 cells have high levels of activated JAK2 and exposure to GH, estrogen, AG490 and other signalling inhibitors did not affect JAK2 phosphorylation. Interestingly, AG490 treatment dramatically decreased ERK2 signalling, although GH did stimulate ERK2 phosphorylation above control levels. AG490 also decreased CBFA1 expression, a transcription factor known to activate MMP9 and MMP13. Finally, GH and estrogen treatment increased expression of SOCS3 mRNA, suggesting that SOCS3 may regulate JAK/STAT signalling in SW1353 cells. The modulation of GH-mediated MMP expression by estrogen in SW1353 cells represents a potentially novel mechanism by which estrogen may regulate longitudinal bone growth. However, further investigation is required in order to elucidate the precise mechanisms behind estrogen and GH regulation of MMP13 expression in SW1353 cells. This study has provided additional evidence that estrogen and the ER gene are major factors in the regulation of growth and the determination of adult height. Newly identified polymorphisms in the ER gene not only contribute to our understanding of the genetic basis of human height, but may also be useful in association studies examining other complex traits. This study also identified several estrogen regulated genes and indicated that estrogen modifies the expression of genes which are primarily expressed in the hypertrophic region of the epiphyseal growth plate. Furthermore, synergistic studies incorporating GH and estrogen have revealed the ability of estrogen to attenuate the effects of GH on MMP13 expression, revealing potential pathways by which estrogen may modulate growth plate fusion, longitudinal bone growth and even arthritis.
534

The reliability of retrospective methods for exploring onset of height fear : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Psychology at Massey University, Palmerston North, New Zealand

Chin, Edwin Chun-Hong January 2008 (has links)
The non-associative framework on fear argues that evolutionary-relevant fears, such as heights and water, are largely innate and do not require associative conditioning experiences to develop (Menzies & Clarke, 1993a, b; Poulton & Menzies, 2002a). However, this framework has been criticized for its reliance on retrospective recall for empirical support (Mineka & Öhman, 2002), which has been found to be highly unreliable (Taylor, Deane, & Podd, 1999). Thirty height-fearful undergraduate students completed the Origins Questionnaire-II (OQ-II; Menzies & Parker, 2001) and were classified into one of the several associative and non-associative pathways of fear onset based on their responses. A control group of 43 non-fearful students completed a modified version of the OQ-II to report any past experiences with heights. To examine the stability of these responses over time, the same questionnaires for both groups were completed again three months (Time 2) and 12 months (Time 3) after the initial administration of the test, along with measures of fear severity. Results showed that neither associative nor non-associative accounts took precedence over the other in explaining the onset of height fear. Instabilities in pathway ascriptions were observed in 18.18% of cases over three months (between Time 1 and Time 2), and 27.27% of cases over nine months (between Time 2 and Time 3). The theoretical and practical implications of the results are discussed with consideration of some of the study’s procedural and instrumental limitations. In light of these limitations, this study identified a substantial role of non-associative pathways on the development of height fear, and provided further support for the limitations of retrospective recall for ascertaining the pathway to fear onset.
535

Τεχνικογεωλογικές συνθήκες κατά τη διάνοιξη των σηράγγων Πλατάνου και Τράπεζας της Σ.Γ.Υ.Τ. Κιάτου – Αιγίου. Εφαρμογή αναλυτικών προσεγγίσεων για τον προσδιορισμό της αλληλεπίδρασης αντιστήριξης και περιβάλλουσας βραχομάζας / Geotechnical conditions during the excavation of two tunnels at Platanos and Trapeza of the Kiato - Egio railroad . Application of analytical programs (Plaxis) for determining the interaction between primary support and surrounding rock mass

Σωτήρχος, Αλέξανδρος 07 October 2011 (has links)
Σκοπός της παρούσας διατριβής είναι η παρουσίαση και μελέτη των τεχνικογεωλογικών συνθηκών κατά την διάνοιξη των σηράγγων Πλάτανου και Τράπεζας της Σ.Γ.Υ.Τ. Κιάτου – Αίγιου. Στην παρούσα εργασία θα γίνει η χρήση αναλυτικών μεθόδων και συγκεκριμένα της μεθόδου ανάλυσης πεπερασμένων στοιχείων του κώδικα Plaxis για τον προσδιορισμό της αλληλεπίδρασης μέτρων αντιστήριξης και περιβάλλουσας βραχομάζας. Αυτό θα γίνει μελετώντας τις μετρημένες κατά την διάνοιξη σύγκλισης και σύγκριση τους με τις υπολογισμένες από την μέθοδο των πεπερασμένων στοιχειών. / In this dissertation are presented and examined the geotechnical conditions during the excavation of two tunnels at Platanos and Trapeza of the Kiato - Egio railroad. Using analytical methods namely finite element method (FEM) and the code Plaxis for determining the interaction between primary support and surrounding rock mass. There examined the real displacement measured during the excavation in contrast with the calculated displacement by FEM. Also, there are correlated vertical displacements at the roof of the tunnel with overburden height.
536

Stem form, height and volume models for teak in Tanzania

Van Zyl, Louis 03 1900 (has links)
Thesis (MScFor (Forest and Wood Science))--University of Stellenbosch, 2005. / The aim of this study was to develop a set of models that will allow the determination of volume for Tectona grandis trees and stands grown in plantation form in Tanzania. As a secondary objective, models describing tree and dominant stand height were developed. Total volume and volume ratio models were fitted that respectively predict total tree volume and merchantable volume. In order to allow the calculation of volume for different product classes and dimensions, taper models were fitted. All the data were collected by non-destructive sampling methods using a Barr and Stroud optical dendrometer. This proved to be an accurate and inexpensive method of collecting data for developing volume and taper models. Sampling stratification was based on age and site quality and as wide a range as possible was covered to ensure adequate representation of all growing sites and ages present in Tanzanian teak plantations. A total of 2617 individual observations were made from 222 trees at three teak plantations. Several models were selected from the literature to describe teak volume and shape. Results indicated that the Schumacher and Hall (1933) volume equation best describes total volume over and underbark to a fixed upper limit of 7.5 cm. Merchantable volume to upper stem diameter and height limits were best described by respectively the Burkhart (1977) volume ratio model and the Cao and Burkhart (1980) modification thereof. Many of the fitted taper models were unable to adequately describe stem shape over the whole stem, mainly due to the large range in tree sizes and ages used in model fitting. The variable form taper model by Perez, Burkhart and Stiff (1990) provided the best results according to various criteria and is recommended for predicting teak underbark diameters to various heights and, if only a single model is required, the merchantable volume. Top height growth of teak stands was adequately described by the generalized Schumacher (1939) model with the value of the exponent k estimated from the sample data. From this a series of anamorphic site index curves were developed. Suitable height-dbh curves were obtained by a simple linear model and predictions improved by including stand age and site index as predictor variables.
537

Efeitos da exposição ao fumo durante a gestação nas medidas antropométricas dos recém-nascidos / Effects of passive tobacco exposure during pregnancy on anthropometric measurements of newborns

Schuh, Claudia Maria January 2008 (has links)
Objetivos: Diversos trabalhos documentaram a associação entre o fumo ativo na gestação e a redução no peso,comprimento e perímetro cefálico dos recémnascidos. Porém, existem controvérsias quanto aos efeitos do fumo passivo. Esse estudo buscou colaborar na elucidação sobre os efeitos da exposição da gestante ao fumo nas medidas antropométricas do recém-nascido. Métodos: Estudo transversal, que incluiu 200 parturientes, identificando a intensidade da exposição das mesmas ao fumo através da mensuração da cotinina urinária e do auto-relato sobre seu hábito tabágico e de seus familiares,o que possibilitou categorizá-las em não fumantes, fumantes passivas e fumantes ativas e posterior comparação com as medidas antropométricas dos recémnascidos. Resultados: Encontramos uma diferença estatisticamente significativa no peso,quando comparamos as fumantes passivas às não fumantes, -152g (IC95%: -285 a -18;P=0,026) e a diferença encontrada nas fumantes ativas foi de - 159g (IC95%: -301 a -16; P=0,029), em relação às não fumantes. Na medida do comprimento, observou-se uma diferença significativa entre as fumantes passivas, -0,8cm (IC95%: -1,4 a -0,2;P=0,012) em relação às não fumantes, e entre as fumantes ativas a diferença foi de -1,0cm (IC95%: -1,6 a -0,3;P=0,003), quando comparado às não fumantes. Quanto à medida do perímetro cefálico, não foram observadas diferenças significativas quando os grupos, das fumantes passivas e fumantes ativas, foram comparados ao grupo das não fumantes. Conclusões: Os resultados sugerem que o fumo passivo durante a gestação pode apresentar efeitos semelhantes aos do fumo ativo nas medidas antropométricas dos recém-nascidos. / Objectives: Several studies have documented the association between active smoking during pregnancy to weight, height and head circumference reduction on newborns. However, there are controversies about the passive smoking. The present study sough the elucidation of the effects of tobacco exposition of pregnant women on anthropometric measurements of newborns. Methods: Cross-sectional study, including 200 in labor women, identifying the intensity of their exposition to tobacco through the measurement of urine cotinine and the self reported information about the smoking habit of their relatives and themselves, what allowed us to classify them as non-smokers, passive smokers and active smokers and later the comparison with the anthropometric measurements of newborns. Results: We found a statistically significant difference in weight when comparing passive smokers to non-smokers, -152g (CI 95%: -285 to –18; P=0.026) and the difference found on active smokers was - 159g (CI 95%: -301 to 16; P=0.029) when compared to non-smokers. On the height measurements, a significant difference was found within the group of passive smokers, -0,8 cm (CI 95%: -1,4 to -0.2; P=0.012) comparing to the non-smokers group, within the smokers group the difference was -1,0 cm (CI 95%: -1,6 to -0.3; P=0.003) when compared to nonsmokers. About the measurements of head circumference, no was found a significant difference when the passive smokers and active smokers group was compared to non-smokers group. Conclusions: The results suggest that the passive smoking during pregnancy may present similar effects as the active smoking on the anthropometric measurements of newborns.
538

Fenologia, desenvolvimento e produtividade de cultivares de soja em função de épocas de semeadura e densidades de plantas /

Oliveira, Arnold Barbosa de. January 2010 (has links)
Orientadora: Maria Aparecida Pessôa da Cruz Centurion / Banca: Paulo Henrique Caramori / Banca: Pedro Luís da Costa Aguiar Alves / Resumo: O objetivo do trabalho foi avaliar fenologia, crescimento, desenvolvimento, acamamento e produtividade de soja, conforme cultivar, época de semeadura e densidade de plantas, em Londrina - PR. Dez cultivares de soja foram semeadas em 18/10 e 28/11/2008, e conduzidas nas densidades de 250 e 400 mil plantas por hectare. Utilizou-se o delineamento em blocos ao acaso, com quatro repetições, e parcelas de quatro linhas de 8 m de comprimento. Quantificaram-se: (i) os dias, crescimento da haste e nós formados da emergência ao início do florescimento (VE-R1) e até a colheita (VE-R8); (ii) os dias até o início de enchimento de grãos (VE-R5); além de (iii) vagens e grãos por planta, massa de 100 sementes, ramificação, acamamento e produtividade na colheita (R8). A menor densidade de plantas promoveu maior formação de nós e ramos na haste principal. A primeira época condicionou maior crescimento das plantas no período reprodutivo e maior número de ramos. A segunda condicionou maior crescimento no período vegetativo. Períodos juvenis, na primeira, e fotoperíodos críticos, na segunda, influenciaram florescimentos, interagindo com os fotoperíodos, para a maioria das cultivares. O fator genético exerceu maior influência sobre as variáveis relacionadas ao desenvolvimento, produtividade e componentes da produção / Abstract: The objective of this research work was to evaluate phenology, plant growth, development, lodging and grain yield of soybean, according to cultivar, sowing date and plant density in Londrina, PR. Ten soybean cultivars were sown on Oct/18 and Nov/28/2008, and cropped under 250 and 400 thousand plants per hectare. A randomized block design with four replicates was applied with plots consisting of four rows of 8 m long. The following evaluations were determined: (i) number of days, stem growth and nodes formed from seedling emergence to beginning flowering (VE-R1) and also up to harvesting (VE-R8); (ii) number of days to beginning of seed filling (VE-R5); and (iii) number of pods and grains per plant, mass of 100 seeds, branching, lodging and grain yield at harvest (R8). The lowest plant population resulted in the largest number of branches and nodes on the main stem. The first sowing date promoted the largest plant growth on the reproductive stage and largest number of branches. The second resulted in the largest plant growth in the vegetative period. Juvenile period in the first planting date and critical photoperiods in the second influenced flowering, which interacted with photoperiods for the majority of the cultivars. Genetic factors had the greatest influence on the variables related to plant development, grain productivity and yield components / Mestre
539

Desenvolvimento de um controlador híbrido Fuzzy-PID para estabilização de um VANT do tipo quadrirrotor na realização de um voo autônomo vertical

Morais, Edpo Rodrigues de 17 February 2017 (has links)
Submitted by Lara Oliveira (lara@ufersa.edu.br) on 2017-06-29T22:59:45Z No. of bitstreams: 1 EdpoRM_DISSERT.pdf: 4900218 bytes, checksum: 0b5f0ce9961abf50eb5fe43f882601c0 (MD5) / Rejected by Vanessa Christiane (referencia@ufersa.edu.br), reason: Corrigir referência. on 2017-07-03T12:21:49Z (GMT) / Submitted by Lara Oliveira (lara@ufersa.edu.br) on 2017-07-04T14:22:25Z No. of bitstreams: 1 EdpoRM_DISSERT.pdf: 4900218 bytes, checksum: 0b5f0ce9961abf50eb5fe43f882601c0 (MD5) / Approved for entry into archive by Vanessa Christiane (referencia@ufersa.edu.br) on 2017-07-04T16:48:02Z (GMT) No. of bitstreams: 1 EdpoRM_DISSERT.pdf: 4900218 bytes, checksum: 0b5f0ce9961abf50eb5fe43f882601c0 (MD5) / Approved for entry into archive by Vanessa Christiane (referencia@ufersa.edu.br) on 2017-07-04T16:58:07Z (GMT) No. of bitstreams: 1 EdpoRM_DISSERT.pdf: 4900218 bytes, checksum: 0b5f0ce9961abf50eb5fe43f882601c0 (MD5) / Made available in DSpace on 2017-07-04T17:03:31Z (GMT). No. of bitstreams: 1 EdpoRM_DISSERT.pdf: 4900218 bytes, checksum: 0b5f0ce9961abf50eb5fe43f882601c0 (MD5) Previous issue date: 2017-02-17 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This dissertation proposes the development of a Fuzzy-PID hybrid controller for the height stability control of a four-engine type UAV. The work also contemplates the development of a classical PID controller, used to compare with the hybrid one purposed. The AuRoRA platform is used for the realization of tests with both of the control structures, being this one provided with the parameters of the Drone used. With the test results, it was possible to conclude that both of the controllers, the classical PID and the Fuzzy-PID, are able to perform the Drone height control, and the hybrid control obtained some advantages such as the ability of self-adjust with the system variation, that dispenses the manual tuning of the gains, besides presenting an improvement in the Drone height stability / Esta dissertação propõe o desenvolvimento de um controlador híbrido Fuzzy-PID para o controle de estabilidade de altura de um VANT do tipo quadrirrotor. O trabalho ainda contempla o desenvolvimento de um controlador PID clássico, utilizado para fins de comparação com o controlador híbrido proposto. A plataforma AuRoRA é utilizada para a realização dos testes com ambas as estruturas de controle, sendo a mesma munida dos parâmetros do Drone utilizado. Com os resultados dos testes, foi possível verificar que ambos controladores, PID clássico e Fuzzy-PID, são capazes de realizar o controle de altura do Drone, tendo o controle híbrido obtido algumas vantagens como a capacidade de auto ajuste mediante variações no sistema, o que dispensa as sintonias manuais dos ganhos, além de apresentar uma melhoria na estabilidade da altura do Drone / 2017-06-29
540

Sistema de integração lavoura-pecuária : desempenho de novilhos superprecoces e variabilidade espacial do pasto / An integrated crop livestock system: performance of early finished beef steers and sward spatial variability

Wesp, Cristiane de Lima January 2010 (has links)
A introdução de bovinos em pastejo em áreas destinadas ao cultivo de culturas de grãos possibilita maximização de renda no sistema, contribuindo para o benefício da cultura em sucessão, quando a intensidade de pastejo é manejada adequadamente. O objetivo deste trabalho foi avaliar em um sistema de integração lavoura-pecuária, os efeitos de diferentes intensidades de pastejo, em função de quatro alturas de manejo de uma pastagem de aveiapreta e azevém anual em sucessão à cultura da soja, bem como, a influência dessas alturas sobre o desempenho animal, a variabilidade espacial do pasto e a resistência mecânica do solo à penetração. Os tratamentos consistiram das alturas de manejo de pasto de 10, 20, 30 e 40 cm; e de um tratamento sem pastejo (SP). A coleta de dados realizou-se entre julho e novembro de 2008, no município de Tupanciretã, RS, Brasil. Foram utilizados novilhos de corte, provenientes de cruzamento entre as raças Angus, Hereford e Nelore, com peso médio inicial de 203 ± 1,7 kg. Esses foram distribuídos em um delineamento experimental de blocos completos ao acaso, com três repetições, onde permaneceram em pastejo por 122 dias. As alturas médias reais, encontradas para os cinco tratamentos avaliados, corresponderam a 14,1; 22,6; 32,0; 41,1 e 45,0 cm, respectivamente. As variáveis massa de forragem, oferta de forragem e palhada residual responderam de maneira positiva e linear ao incremento da altura do pasto (P≤0,0001). O desempenho individual, o peso vivo ao abate e as características de carcaça dos novilhos apresentaram resposta quadrática, e foram otimizadas em alturas de manejo do pasto próximas a 30 cm (P≤0,0305). As menores alturas de manejo proporcionaram maiores ganhos por área, em função da maior carga animal utilizada. A presença de animais em pastejo proporcionou variabilidade espacial de alturas ao final do ciclo de utilização da pastagem. O mesmo foi observado para a resistência mecânica do solo à penetração, principalmente, nas camadas superciais do solo. Os valores de resistência evidenciaram os efeitos do pastejo até a profundidade de 0,20 m, sendo esses crescentes com o aumento das intensidades de pastejo impostas. Os resultados demonstram que alturas próximas a 30 cm permitem maiores ganhos individuais, em função do aumento da quantidade de forragem disponível por animal, não havendo comprometimento da palhada residual destinada à cultura subseqüente nesses casos, nem dos atributos físicos do solo avaliados. / The introduction of cattle into areas destined for grain crop production enables maximizing income from the system and can benefit the subsequent grain crop provided grazing intensity is managed properly. The objective of this study was to evaluate the effects of different grazing intensities on animal performance, sward spatial variability and soil penetration resistance within in a crop-livestock system. The treatments consisted of four grazing sward heights, 10, 20, 30 and 40 cm, and no grazing (NG), in a sward of black oat and annual ryegrass grown in succession with soybean. The study was conducted from May to November 2008, near Tupanciretã, RS, Brasil. Beef steers (Angus x Hereford x Nellore) with average initial weight of 203 ± 1.7 kg were distributed in a randomized complete block design, with three replications, where they grazed for 122 days. The observed average sward heights for the five treatments were 14.1; 22.6; 32.0; 41.1 and 45.0 cm, respectively. Herbage mass, herbage allowance and residual straw responded positively and linearly to increasing sward heights (P≤0.0001). Average daily gain, slaughter live weight, and carcass characteristics of the steers showed a quadratic response and were optimal in the 30 cm sward height treatment (P≤0.0305). The shorter sward heights provided higher total animal gain per area, due to the associated higher stocking rates. The presence of grazing animals resulted in spatial variability of sward heights at the end of the grazing cycle. The same was observed for soil penetration resistance, particularly in the surface layers of the soil. The soil penetration resistance showed the effect of animal traffic to a depth of 0.20 m, which increased with increasing grazing intensities. The results suggest that maintaining grazed sward heights near 30 cm provides better individual animal gains by the increasing amount of forage available per animal, while not compromising the residual straw remaining for the subsequent grain crop and without inducing excessive soil compaction.

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