989 resultados para Variables did


Relevância:

30.00% 30.00%

Publicador:

Resumo:

As condições de ambiente térmico e aéreo, no interior de instalações para animais, alteram-se durante o dia, devido à influência do ambiente externo. Para que análises estatísticas e geoestatísticas sejam representativas, uma grande quantidade de pontos distribuídos espacialmente na área da instalação deve ser monitorada. Este trabalho propõe que a variação no tempo das variáveis ambientais de interesse para a produção animal, monitoradas no interior de instalações para animais, pode ser modelada com precisão a partir de registros discretos no tempo. O objetivo deste trabalho foi desenvolver um método numérico para corrigir as variações temporais dessas variáveis ambientais, transformando os dados para que tais observações independam do tempo gasto durante a aferição. O método proposto aproximou os valores registrados com retardos de tempo aos esperados no exato momento de interesse, caso os dados fossem medidos simultaneamente neste momento em todos os pontos distribuídos espacialmente. O modelo de correção numérica para variáveis ambientais foi validado para o parâmetro ambiental temperatura do ar, sendo que os valores corrigidos pelo método não diferiram pelo teste Tukey, a 5% de probabilidade dos valores reais registrados por meio de dataloggers.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

Objectives To investigate the effects of levomepromazine and different desflurane concentrations upon electrocardiographic variables.Animals Twenty adult mongrel dogs of both sexes weighing 6-28 kg.Methods Dogs were divided into two groups of 10 animals. Group I received 1 mg kg(-1) lV of levomepromazine and 15 minutes later anesthesia was induced with propofol (3 mg kg(-1) IV). Desflurane end-tidal concentration was set at 1.6 MAC. After 30 minutes at this concentration, measurements were taken and the end-tidal concentration was reduced to 1.4 MAC. Thereafter, it was reduced to 1.2 and then 1.0 MAC at 1.5-minute intervals. The same procedure was followed for group 2, except that levomepromazine was replaced with 0.2 mL kg(-1) of 0.9% saline solution and more propofol was needed for induction (7 mg kg(-1)). The animals' body temperature was maintained between 38.3 and 39 degreesC using a heating pad. The electrocardiographic tracing was obtained from lead II throughout the experimental period. The measurements were taken immediately before the administration of levomepromazine or placebo (T-1), 15 minutes after pre-medication (T-2) and 30 minutes after the establishment of 1.6 MAC (T-3)The other measurements were made at the concentrations of 1.4, 1.2, and 1.0 MAC, respectively (T4-6). The numerical data were submitted to analysis of variance plus F-test (p < 0.05).Results the dogs that received levomepromazine had a decrease in heart rate. However, in both groups it increased with desflurane administration. Levomepromazine, in association with desflurane, did not induce significant electrocardiographic changes, and all mean values (except P-wave duration) were within the reference range for this species.Conclusions and clinical relevance This study documented that levomepromazine, in association with desflurane, does not induce significant changes in electrocardiographic variables, suggesting that this drug combination has minimal effect on myocardial conduction.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

The influence of 2 different levels of the inspired oxygen fraction (FiO(2)) on blood gas variables was evaluated in dogs with high intracranial pressure (ICP) during propofol anesthesia (induction followed by a continuous rate infusion [CRI] of 0.6 mg/kg/min) and intermittent positive pressure ventilation (IPPV). Eight adult mongrel dogs were anesthetized on 2 occasions, 21 d apart, and received oxygen at an FiO(2) of 1.0 (G100) or 0.6 (G60) in a randomized crossover fashion. A fiberoptic catheter was implanted on the surface of the right cerebral cortex for assessment of the ICP. An increase in the ICP was induced by temporary ligation of the jugular vein 50 min after induction of anesthesia and immediately after baseline measurement of the ICP. Blood gas measurements were taken 20 min later and then at 15-min intervals for 1 h. Numerical data were submitted to Morrison's multivariate statistical methods. The ICP, the cerebral perfusion pressure and the mean arterial pressure did not differ significantly between FiO(2) levels or measurement times after jugular ligation. The only blood gas values that differed significantly (P < 0.05) were the arterial oxygen partial pressure, which was greater with G100 than with G60 throughout the procedure, and the venous haemoglobin saturation, that was greater with G100 than with G60 at M0. There were no significant differences between FiO(2) levels or measurement times in the following blood gas variables: arterial carbon dioxide partial pressure, arterial hemoglobin saturation, base deficit, bicarbonate concentration, pH, venous oxygen partial pressure, venous carbon dioxide partial pressure and the arterial-to-end-tidal carbon dioxide difference.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Relevância:

30.00% 30.00%

Publicador:

Resumo:

Recent studies have shown that ingestion by the army worm Spodoptera frugiperda of Cry1Ac toxin from Bt cotton promotes histochemical and ultrastructural changes in the digestive cells of the predatory pentatomid bug Podisus nigrispinus. Therefore, mindful of the changes in the midgut of the predator, which represents the first line of defence in this insect, our aim was to test the hypothesis that the consumption of Bt cotton-fed S. frugiperda by P. nigrispinus might lead to alterations in components of the immune system of P. nigrispinus. The Cry1Ac toxin level in the leaves of Bt cotton, nitric oxide, phenoloxidase activity, and total proteins were quantified by ELISA. Total and differential hemocyte counts were evaluated, and hemocyte ultrastructure analysis was undertaken. We found that ingestion of the prey fed daily with approximately 23 ± 0.70 ng g-1 Cry1Ac by wet weight of leaves, and expressed by the Bt cotton, induces small ultrastructural changes in the predator's granulocytes and plasmatocytes. However, these changes did not affect the total number and differential and humoral variables analyzed for the bug's hemocytes. © 2013 Copyright Taylor and Francis Group, LLC.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

The present study investigated the osmotic dehydration (OD) of mangoes cv.Palmer, dehydrated in a sucrose solution with added ascorbic acid (AA), aiming toevaluate the influence of the process variables (sucrose concentration, AA concen-tration and time) on vitamin C, water, sugars and total phenolic compound (TPC)contents by way of an analysis of the effects and the variance of the factors. Thesucrose concentration did not affect the vitamin C content, but the AA concentra-tion in the solution and the process time exerted a positive influence on thisresponse. The addition of AA also presented a significant positive effect on theTPC contents because this vitamin interferes with the quantification of the TPC.On discounting the interferences, no losses of phenolic compounds were found.Impregnation with vitamin C during OD was shown to be effective in obtainingminimally processed mangoes with high nutritional value.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

Background: Studies on functional capacity in community-dwelling older people have shown associations between declines in instrumental activities of daily living (IADL) and several factors. Among these, age has been the most consistently related to functional capacity independent of other variables. We aimed at evaluating the performance of a sample of healthy and cognitively intact Brazilian older people on activities of daily living and to analyze its relation to social-demographic variables. Methods: We conducted a secondary analysis of data collected for previous epidemiological studies with community-dwelling subjects aged 60 years or more. We selected subjects who did not have dementia or depression, and with no history of neurological diseases, heart attack, HIV, hepatitis or arthritis (n = 1,111). Functional capacity was assessed using the Brazilian version of the Older American Resources and Services Questionnaire (BOMFAQ). ADL performance was analyzed according to age, gender, education, and marital status (Pearson's chi(2), logistic regression). Results: IADL difficulties were present in our sample, especially in subjects aged 80 years or more, with lower levels of education, or widowed. The logistic regression analysis results indicated that "higher age" and "lower education" (p <= 0.001) remained significantly associated with IADL difficulty. Conclusions: Functional decline was present in older subjects even in the absence of medical conditions and cognitive impairment. Clinicians and researchers could benefit from knowing what to expect from older people regarding IADL performance in the absence of medical conditions.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

El objetivo general de esta Tesis doctoral fue estudiar la influencia de diversos factores nutricionales sobre los parámetros productivos y el desarrollo del tracto digestivo de pollitas rubias destinadas a la producción de huevos comerciales. Para alcanzar este objetivo se realizaron tres experimentos donde se estudió el cereal principal, el tamaño de partícula del cereal y el nivel de energía y la presentación de los piensos. En el experimento 1 se estudió la influencia del cereal (piensos con enzimas) y la presentación del pienso sobre los parámetros productivos y las características del tracto digestivo en 576 pollitas rubias de 1 a 120 d de edad. De 1 a 45 d de la edad, se utilizaron 4 piensos experimentales organizados de forma factorial con 2 cereales al 50% de inclusión (maíz vs. trigo) y 2 presentaciones del pienso (harina vs. gránulo de 2- mm de diámetro). Cada tratamiento se replicó 6 veces (24 pollitas por réplica). De 46 a 120 d de edad todas las dietas (maíz o trigo) se ofrecieron en harina y por tanto, la única diferencia entre tratamientos fue el cereal utilizado. De 1 a 120 d de edad, las pollitas que recibieron los piensos basados en maíz tuvieron una ganancia de peso vivo (PV) superior (P < 0,05) que las que recibieron los piensos basados en trigo, pero el índice de conversión (IC) fue similar para ambos grupos. De 1 a 45 d de edad, las pollitas alimentadas con gránulo consumieron más pienso (P < 0,001) y tuvieron una ganancia de peso superior (P < 0,001) que las pollitas alimentadas con harina. Gran parte de los efectos beneficiosos de la granulación sobre los parámetros productivos se mantuvieron al final de la prueba (120 d de edad). A los 45 d de edad, el peso relativo de la molleja (PR; g/kg PV) fue superior (P < 0,01) en pollitas alimentadas con maíz que en pollitas alimentadas con trigo. La alimentación en gránulo redujo el PR del tracto gastro intestinal (TGI) y de la molleja (P < 0,001), así como la longitud relativa (LR; cm/kg PV) del intestino delgado (P< 0.01) a ambas edades (45 y 120 d de edad). El tipo de cereal utilizado no afectó al pH del contenido de la molleja a 120 d de edad pero fué inferior (P < 0,01) en las pollitas que recibieron el pienso en harina de 1 a 45 d de la edad que en las que recibieron el pienso en gránulo. Se concluye que el trigo puede substituir al maíz en piensos para pollitas si se acepta una ligera reducción en la ganancia de peso. Asímismo, la alimentación en gránulo de 1 a 45 d de edad aumentó la ganancia de peso a esta edad y al final de la prueba, así como el pH de la molleja a 120 d de edad. La presentación del pienso en gránulo redujo el PR de la molleja y la LR del TGI a 120 d de edad. En el experimento 2 se utilizaron un total de 864 pollitas rubias Hy-Line de 1 d de edad para estudiar la influencia del cereal de la dieta (500 g de maíz o trigo/kg) y el tamaño de partícula del mismo (molienda con molino de martillos con un diámetro de criba de 6, 8, o 10-mm) sobre los parámetros productivos y las características del TGI de 1 a 120 d de edad. Cada uno de los 6 tratamientos se replicó 6 veces (24 pollitas por réplica). De 1 a 45 d de edad, la ganancia de PV aumentó (P< 0,001) y el IC se mejoró (P < 0,05) al reducir el tamaño de partícula del cereal, pero no se observaron diferencias en el periodo crecimiento de 45 a 120 d de edad. A los 45 d de vida, las pollitas alimentadas con maíz tendieron (P < 0,10) a tener un mayor PR del TGI y del proventrículo y una mayor LR del intestino delgado que las pollitas alimentadas con trigo. Asímismo, el PR del TGI a esta edad, aumentó (P < 0,05) a medida que aumentaba el tamaño de partícula del cereal utilizado. A los 120 d de edad, el tratamiento no afectó el PR de ninguno de los órganos del TGI ni al pH de la molleja. Sin embargo, la LR del intestino delgado fue superior (P < 0,05) para las pollitas alimentadas con trigo que para las pollitas alimentadas con maíz. La LR del TGI se redujó (P < 0,05) al aumentar el tamaño de partícula del cereal. Se concluye que el trigo puede incluirse 500 g/kg en piensos de pollitas de 1 a 120 días de edad y que el tamaño de partícula de los cereales afecta el crecimiento de las pollitas durante los primeros 45 d de vida, pero no después. Por lo tanto, se recomienda moler el cereal utilizado al inicio del período de recría (1 a 45 d de edad) con una criba de diámetro igual o inferior a 8 mm. En el experimento 3 se utilizaron un total de 1.152 pollitas rubias Hy-Line de 1 d de edad para estudiar la influencia del nivel de energía de la dieta y la presentación del pienso sobre la productividad y las características del TGI. De 1 a 45 d de edad se utilizaron 6 piensos organizados de forma factorial con 3 concentraciones energéticas (baja: 11,44 MJ; media: 12,05 MJ y alta: 12,66 MJ/kg) y 2 presentaciones del pienso (harina vs. gránulo). De 45 a 120 d todos los piensos experimentales se suministraron en forma de harina y por tanto, la única diferencia entre tratamientos fue el nivel de EMAn utilizado. Cada uno de los 6 tratamientos se replicó 8 veces y la unidad experimental fue la jaula con 24 pollitas. De 1 a 120 d de edad, la ganancia de PV y el IC mejoraron a medida que aumentó la EMAn del pienso (P < 0,001). Las pollitas alimentadas con gránulo de 1 a 45 d de edad comieron mas y tuvieron una ganancia de peso superior (P < 0,001) que las alimentadas con harina. En el global de la prueba, la ganancia de PV fue mayor (P < 0,01) para las pollitas alimentadas con piensos en gránulo. A los 45 d de edad, el PR de todos los segmentos del TGI estudiados fue inferior para las pollitas alimentadas con piensos de alta energía que para las pollitas alimentadas con piensos de media o baja energía. A 120 d de edad, el PR de la molleja fue superior (P < 0,01) para las pollitas alimentadas con piensos de baja energía que con los otros piensos. Sin embargo, la LR del TGI no se vió afectada por el nivel de energía de los piensos. A los 45 d de edad, la alimentación con gránulo redujo el PR del proventrículo (P < 0,05), de la molleja (P < 0,001) y del TGI (P < 0.001), así como la LR del intestino delgado (P < 0,05) y de los ciegos (P < 0,001). A pesar de que las pollitas solo recibieron los piensos en gránulo durante los primeros 45 d de vida, la alimentación con gránulos redujo el PR de la molleja y del proventrículo a 120 d de edad. Se concluye que la alimentación con gránulos durante los primeros 45 d de vida mejora el consumo de pienso y el PV de las pollitas a 120 d de edad. Un aumento del nivel de energía de la dieta de 12,0 a 12,7 MJ/kg mejora los parámetros productivos de 1 a 120 d de edad pero reduce el tamaño del proventrículo y de la molleja. En base de estos resultados concluimos que maíz y trigo con enzimas pueden utilizarse indistintamente en piensos para pollitas de 1 a 120 d de edad con sólo una ligera disminución del PV final con trigo. La granulación y la reducción del tamaño de partícula del cereal del pienso de primera edad (1 a 45 d de vida) y el uso de piensos de alta densidad energética, mejoran los PV a 120 d de edad. Por lo tanto, es recomendable moler los cereales con cribas de no más de 8-mm de diámetro. También, la granulación del pienso y el uso de piensos de alta energía (pobres en fibra bruta) pueden reducir el desarrollo del TGI especialmente de la molleja, lo que puede perjudicar el consumo posterior de pienso durante el inicio del ciclo de puesta. ABSTRACT The general objective of this Thesis was to study the effect of different nutritional factors on productive performance and the development of the gastrointestinal tract (GIT) of commercial brown egg-laying pullets from 1 to 120 d of age. In this respect, the influence of type and particle size of the cereal, and feed form, and energy content of the die,t were studied in 3 experiments. In experiment 1, the influence of the main cereal and feed form of the diet on performance and GIT traits was studied in 576 brown-egg laying pullets from 1 to 120 d of age. From 1 to 45 d of age, 4 diets arranged factorially with 2 cereals (maize vs. wheat) and 2 feed forms (mash vs. pellets) were used. Each treatment was replicated 6 times (24 pullets per replicate). From 46 to 120 d of age, all diets were offered in mash form and therefore, the only difference among diets was the cereal used. Cumulatively, pullets fed the maize diets had higher body weight (BW) gain (P< 0.05) but similar feed conversion ratio (FCR) than pullets fed the wheat diets. From 1 to 45 d of age, pullets fed pellets consumed more feed (P < 0.001) and had higher BW gain (P < 0.001) than pullets fed mash. Most of the beneficial effects of pelleting on productive performance of the birds were still evident at 120 d of age. At 45 d of age, gizzard relative weight (RW; g/kg BW) was higher (P < 0.01) in pullets fed maize than in pullets fed wheat. Feeding pellets reduced the RW of the GIT and the gizzard (P < 0.001) as well as the relative length (RL; cm/kg BW) of the small intestine (SI, P < 0.01) at both ages. The pH of the gizzard contents at 120 d of age was not affected by the main cereal of the diet, but was lower in pullets fed mash from 1 to 45 d of age (P < 0.01) than in pullets fed pellets. We conclude that wheat supplemented with enzymes can be used in substitution of maize in pullet diets with only a slight reduction in BW gain at 120 d of age. Also, feeding pellets from 1 to 45 d of age increased BW gain and pH of the gizzard, and reduced the RW of the gizzard and the RL of the GIT at 120 d of age. In experiment 2, a total of 864 brown-egg laying pullets was used to study the effects of the main cereal of the diet (500 g maize or wheat/kg) and particle size of the cereal (hammer milled to pass through a 6, 8, and 10-mm screen) on growth performance and GIT traits from 1 to 120 d of age. Each of the 6 treatments was replicated 6 times (24 pullets per replicate). Type of cereal did not affect pullet performance at any age. From 1 to 45 d of age, BW gain was increased (P < 0.001) and FCR was improved (P < 0.05) as the particle size of the cereal was reduced, but no effects were observed after this age. At 45 d of age, pullets fed maize tended (P < 0.10) to have a heavier RW of the GIT and proventriculus and a higher relative length (RL, cm/kg BW) of the SI than pullets fed wheat. Also at this age, the RW of the GIT increased (P < 0.05) with increases in particle size of the cereal. At 120 d of age, dietary treatment did not affect the RW of any of the organs studied or gizzard pH, but the RL of the SI was higher (P < 0.05) for pullets fed wheat than for pullets fed maize. Also, the RL of the SI was reduced (P < 0.05) as the particle size of the cereal increased. We conclude that 500 g wheat/kg can be included in pullet feeds from 1 to 120 d of age, and that particle size of the cereal affects pullet performance during the first 45 d of life but not thereafter. Therefore, it is recommended to grind the cereal used in this period with a screen size of no more than 8-mm. In experiment 3, a total of 1,152 one-day-old Hy-Line Brown egg laying pullets were used to study the influence of the energy content of the diet and feed form on productive performance and on several GIT traits. From 1 to 45 d of age, there were 6 diets arranged factorially with 3 concentrations of AMEn (low: 11.66 MJ/kg, medium: 12.05 MJ/kg and high: 12.66 MJ/kg) of the diet and 2 feed forms (mash vs. pellets). From 45 to 120 d all diets were fed in mash form and therefore, the only difference among treatments in this period was the energy content of the diets. Each of the 6 treatments was replicated 8 times and the experimental unit was formed by 24 pullets. Cumulatively, BW gain and FCR improved as the AMEn of the diet increased (P < 0.001). Also, pullets fed pellets from 1 to 45 d of age had higher feed intake and BW gain (P < 0.001) in this period and higher cumulative BW gain (P < 0.01) than pullets fed mash. At 45 d of age, the RWof all the segments of the GIT was lower for pullets fed the high- than for pullets fed the medium- or low- energy diets. At 120 d of age, the RW of the gizzard was higher (P < 0.01) for pullets fed the low energy diets than for pullets fed the other diets. However, the RL of the GIT was not affected by the energy content of the diet. Feeding pellets reduced the RW of the proventriculus (P < 0.05), gizzard (P < 0.001), and GIT (P < 0.001), as well as the RL of the small intestine (P < 0.05) and the ceaca (P < 0.001) at 45 d of age. The effects of feeding pellets on RW of gizzard and proventriculus were still evident at 120 d of age. We concluded that feeding pellets from 1 to 45 d of age improved feed intake and BW of pullets at 120 d of age and that an increase in the energy content of the diet increased pullet performance at all ages but reduced the RW of the proventriculus and gizzard. We conclude that maize and wheat can be used indistinctly in diets for egg laying pullets from 1 to 120 d of age, with only a slight reduction in final BW when wheat is used. Also, particle size of the cereal affects pullet performance during the first 45 d of life but not thereafter. Pelleting of the feeds, and grinding the cereal with a screen size of no more than 8-mm from 1 to 45 d of age, and the use of high density energy diets are recommended in order to achieve adequate target BW at 120 d of age. However, pelleting of the feed, very fine grinding, and the use of high AMEn diets might hinder the development of the GIT, especially that of the gizzard, which might affect feed intake of laying hens especially at the beginning of the production cycle.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

La investigación de esta tesis se centra en el estudio de técnicas geoestadísticas y su contribución a una mayor caracterización del binomio factores climáticos-rendimiento de un cultivo agrícola. El inexorable vínculo entre la variabilidad climática y la producción agrícola cobra especial relevancia en estudios sobre el cambio climático o en la modelización de cultivos para dar respuesta a escenarios futuros de producción mundial. Es información especialmente valiosa en sistemas operacionales de monitoreo y predicción de rendimientos de cultivos Los cuales son actualmente uno de los pilares operacionales en los que se sustenta la agricultura y seguridad alimentaria mundial; ya que su objetivo final es el de proporcionar información imparcial y fiable para la regularización de mercados. Es en este contexto, donde se quiso dar un enfoque alternativo a estudios, que con distintos planteamientos, analizan la relación inter-anual clima vs producción. Así, se sustituyó la dimensión tiempo por la espacio, re-orientando el análisis estadístico de correlación interanual entre rendimiento y factores climáticos, por el estudio de la correlación inter-regional entre ambas variables. Se utilizó para ello una técnica estadística relativamente nueva y no muy aplicada en investigaciones similares, llamada regresión ponderada geográficamente (GWR, siglas en inglés de “Geographically weighted regression”). Se obtuvieron superficies continuas de las variables climáticas acumuladas en determinados periodos fenológicos, que fueron seleccionados por ser factores clave en el desarrollo vegetativo de un cultivo. Por ello, la primera parte de la tesis, consistió en un análisis exploratorio sobre comparación de Métodos de Interpolación Espacial (MIE). Partiendo de la hipótesis de que existe la variabilidad espacial de la relación entre factores climáticos y rendimiento, el objetivo principal de esta tesis, fue el de establecer en qué medida los MIE y otros métodos geoestadísticos de regresión local, pueden ayudar por un lado, a alcanzar un mayor entendimiento del binomio clima-rendimiento del trigo blando (Triticum aestivum L.) al incorporar en dicha relación el componente espacial; y por otro, a caracterizar la variación de los principales factores climáticos limitantes en el crecimiento del trigo blando, acumulados éstos en cuatro periodos fenológicos. Para lleva a cabo esto, una gran carga operacional en la investigación de la tesis consistió en homogeneizar y hacer los datos fenológicos, climáticos y estadísticas agrícolas comparables tanto a escala espacial como a escala temporal. Para España y los Bálticos se recolectaron y calcularon datos diarios de precipitación, temperatura máxima y mínima, evapotranspiración y radiación solar en las estaciones meteorológicas disponibles. Se dispuso de una serie temporal que coincidía con los mismos años recolectados en las estadísticas agrícolas, es decir, 14 años contados desde 2000 a 2013 (hasta 2011 en los Bálticos). Se superpuso la malla de información fenológica de cuadrícula 25 km con la ubicación de las estaciones meteorológicas con el fin de conocer los valores fenológicos en cada una de las estaciones disponibles. Hecho esto, para cada año de la serie temporal disponible se calcularon los valores climáticos diarios acumulados en cada uno de los cuatro periodos fenológicos seleccionados P1 (ciclo completo), P2 (emergencia-madurez), P3 (floración) y P4 (floraciónmadurez). Se calculó la superficie interpolada por el conjunto de métodos seleccionados en la comparación: técnicas deterministas convencionales, kriging ordinario y cokriging ordinario ponderado por la altitud. Seleccionados los métodos más eficaces, se calculó a nivel de provincias las variables climatológicas interpoladas. Y se realizaron las regresiones locales GWR para cuantificar, explorar y modelar las relaciones espaciales entre el rendimiento del trigo y las variables climáticas acumuladas en los cuatro periodos fenológicos. Al comparar la eficiencia de los MIE no destaca una técnica por encima del resto como la que proporcione el menor error en su predicción. Ahora bien, considerando los tres indicadores de calidad de los MIE estudiados se han identificado los métodos más efectivos. En el caso de la precipitación, es la técnica geoestadística cokriging la más idónea en la mayoría de los casos. De manera unánime, la interpolación determinista en función radial (spline regularizado) fue la técnica que mejor describía la superficie de precipitación acumulada en los cuatro periodos fenológicos. Los resultados son más heterogéneos para la evapotranspiración y radiación. Los métodos idóneos para estas se reparten entre el Inverse Distance Weighting (IDW), IDW ponderado por la altitud y el Ordinary Kriging (OK). También, se identificó que para la mayoría de los casos en que el error del Ordinary CoKriging (COK) era mayor que el del OK su eficacia es comparable a la del OK en términos de error y el requerimiento computacional de este último es mucho menor. Se pudo confirmar que existe la variabilidad espacial inter-regional entre factores climáticos y el rendimiento del trigo blando tanto en España como en los Bálticos. La herramienta estadística GWR fue capaz de reproducir esta variabilidad con un rendimiento lo suficientemente significativo como para considerarla una herramienta válida en futuros estudios. No obstante, se identificaron ciertas limitaciones en la misma respecto a la información que devuelve el programa a nivel local y que no permite desgranar todo el detalle sobre la ejecución del mismo. Los indicadores y periodos fenológicos que mejor pudieron reproducir la variabilidad espacial del rendimiento en España y Bálticos, arrojaron aún, una mayor credibilidad a los resultados obtenidos y a la eficacia del GWR, ya que estaban en línea con el conocimiento agronómico sobre el cultivo del trigo blando en sistemas agrícolas mediterráneos y norteuropeos. Así, en España, el indicador más robusto fue el balance climático hídrico Climatic Water Balance) acumulado éste, durante el periodo de crecimiento (entre la emergencia y madurez). Aunque se identificó la etapa clave de la floración como el periodo en el que las variables climáticas acumuladas proporcionaban un mayor poder explicativo del modelo GWR. Sin embargo, en los Bálticos, países donde el principal factor limitante en su agricultura es el bajo número de días de crecimiento efectivo, el indicador más efectivo fue la radiación acumulada a lo largo de todo el ciclo de crecimiento (entre la emergencia y madurez). Para el trigo en regadío no existe ninguna combinación que pueda explicar más allá del 30% de la variación del rendimiento en España. Poder demostrar que existe un comportamiento heterogéneo en la relación inter-regional entre el rendimiento y principales variables climáticas, podría contribuir a uno de los mayores desafíos a los que se enfrentan, a día de hoy, los sistemas operacionales de monitoreo y predicción de rendimientos de cultivos, y éste es el de poder reducir la escala espacial de predicción, de un nivel nacional a otro regional. ABSTRACT This thesis explores geostatistical techniques and their contribution to a better characterization of the relationship between climate factors and agricultural crop yields. The crucial link between climate variability and crop production plays a key role in climate change research as well as in crops modelling towards the future global production scenarios. This information is particularly important for monitoring and forecasting operational crop systems. These geostatistical techniques are currently one of the most fundamental operational systems on which global agriculture and food security rely on; with the final aim of providing neutral and reliable information for food market controls, thus avoiding financial speculation of nourishments of primary necessity. Within this context the present thesis aims to provide an alternative approach to the existing body of research examining the relationship between inter-annual climate and production. Therefore, the temporal dimension was replaced for the spatial dimension, re-orienting the statistical analysis of the inter-annual relationship between crops yields and climate factors to an inter-regional correlation between these two variables. Geographically weighted regression, which is a relatively new statistical technique and which has rarely been used in previous research on this topic was used in the current study. Continuous surface values of the climate accumulated variables in specific phenological periods were obtained. These specific periods were selected because they are key factors in the development of vegetative crop. Therefore, the first part of this thesis presents an exploratory analysis regarding the comparability of spatial interpolation methods (SIM) among diverse SIMs and alternative geostatistical methodologies. Given the premise that spatial variability of the relationship between climate factors and crop production exists, the primary aim of this thesis was to examine the extent to which the SIM and other geostatistical methods of local regression (which are integrated tools of the GIS software) are useful in relating crop production and climate variables. The usefulness of these methods was examined in two ways; on one hand the way this information could help to achieve higher production of the white wheat binomial (Triticum aestivum L.) by incorporating the spatial component in the examination of the above-mentioned relationship. On the other hand, the way it helps with the characterization of the key limiting climate factors of soft wheat growth which were analysed in four phenological periods. To achieve this aim, an important operational workload of this thesis consisted in the homogenization and obtention of comparable phenological and climate data, as well as agricultural statistics, which made heavy operational demands. For Spain and the Baltic countries, data on precipitation, maximum and minimum temperature, evapotranspiration and solar radiation from the available meteorological stations were gathered and calculated. A temporal serial approach was taken. These temporal series aligned with the years that agriculture statistics had previously gathered, these being 14 years from 2000 to 2013 (until 2011 for the Baltic countries). This temporal series was mapped with a phenological 25 km grid that had the location of the meteorological stations with the objective of obtaining the phenological values in each of the available stations. Following this procedure, the daily accumulated climate values for each of the four selected phenological periods were calculated; namely P1 (complete cycle), P2 (emergency-maturity), P3 (flowering) and P4 (flowering- maturity). The interpolated surface was then calculated using the set of selected methodologies for the comparison: deterministic conventional techniques, ordinary kriging and ordinary cokriging weighted by height. Once the most effective methods had been selected, the level of the interpolated climate variables was calculated. Local GWR regressions were calculated to quantify, examine and model the spatial relationships between soft wheat production and the accumulated variables in each of the four selected phenological periods. Results from the comparison among the SIMs revealed that no particular technique seems more favourable in terms of accuracy of prediction. However, when the three quality indicators of the compared SIMs are considered, some methodologies appeared to be more efficient than others. Regarding precipitation results, cokriging was the most accurate geostatistical technique for the majority of the cases. Deterministic interpolation in its radial function (controlled spline) was the most accurate technique for describing the accumulated precipitation surface in all phenological periods. However, results are more heterogeneous for the evapotranspiration and radiation methodologies. The most appropriate technique for these forecasts are the Inverse Distance Weighting (IDW), weighted IDW by height and the Ordinary Kriging (OK). Furthermore, it was found that for the majority of the cases where the Ordinary CoKriging (COK) error was larger than that of the OK, its efficacy was comparable to that of the OK in terms of error while the computational demands of the latter was much lower. The existing spatial inter-regional variability between climate factors and soft wheat production was confirmed for both Spain and the Baltic countries. The GWR statistic tool reproduced this variability with an outcome significative enough as to be considered a valid tool for future studies. Nevertheless, this tool also had some limitations with regards to the information delivered by the programme because it did not allow for a detailed break-down of its procedure. The indicators and phenological periods that best reproduced the spatial variability of yields in Spain and the Baltic countries made the results and the efficiency of the GWR statistical tool even more reliable, despite the fact that these were already aligned with the agricultural knowledge about soft wheat crop under mediterranean and northeuropean agricultural systems. Thus, for Spain, the most robust indicator was the Climatic Water Balance outcome accumulated throughout the growing period (between emergency and maturity). Although the flowering period was the phase that best explained the accumulated climate variables in the GWR model. For the Baltic countries where the main limiting agricultural factor is the number of days of effective growth, the most effective indicator was the accumulated radiation throughout the entire growing cycle (between emergency and maturity). For the irrigated soft wheat there was no combination capable of explaining above the 30% of variation of the production in Spain. The fact that the pattern of the inter-regional relationship between the crop production and key climate variables is heterogeneous within a country could contribute to one is one of the greatest challenges that the monitoring and forecasting operational systems for crop production face nowadays. The present findings suggest that the solution may lay in downscaling the spatial target scale from a national to a regional level.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

El consumo mundial, impulsor del desarrollo y crecimiento económico de los pueblos, no ha sido igual para todas las naciones, ya que sus efectos han sido diferentes para los ciudadanos de los países del Norte y los del Sur, principalmente por dos razones: una, porque han originado complejos y diferentes estilos de vida y aspiraciones, lo que ha originado grandes diferencias entre los individuos de unos y otros países, y, dos, por su falta de valores sociales y éticos. Ante esta situación, la sociedad en su conjunto debe tomar conciencia de este hecho, y a través de un consumo responsable y de un mayor conocimiento de las relaciones comerciales entre los pueblos, debe optar por consumir productos elaborados bajo criterios de justicia y equidad. Para ayudar a alcanzar estos objetivos de equidad, solidaridad, justicia y ética, nació el Comercio Justo, que, en el caso de España, llegó con veinte años de retraso en la década de los ochenta. Aunque a día de hoy sus ventas crecen a un buen ritmo, siguen siendo inferiores al resto de los países europeos, por cuatro razones: (1) el desconocimiento que la mayoría de los potenciales consumidores tienen de este movimiento social; (2) la dificultad de acceder a los productos que comercializan; (3) el poco impulso que se ofrece desde las Administraciones Públicas; y, (4) porque hay pocas investigaciones en las que se haya analizado el Comercio Justo desde la perspectiva de la demanda, lo que ha implicado que no haya un conocimiento profundo sobre los consumidores de este tipo de productos y sobre sus motivaciones de compra. En base a todo lo expuesto, el presente trabajo se concibe como un estudio exploratorio, que tiene como objetivo principal analizar el perfil de los consumidores y no consumidores de productos de Comercio Justo, sus motivaciones de compra y no compra, así como las variables que influyen en la intención de compra futura, tanto en el segmento de consumidores actuales, como en el segmento de no consumidores de este tipo de productos. Para la realización de este trabajo, se ha utilizado, por una parte, una metodología cualitativa, que ha permitido acceder a la información sobre las opiniones y actitudes que intervienen en los procesos de decisión de compra; y, por otra, una metodología cuantitativa, a través de una encuesta online dirigida a 6.500 individuos, que ha permitido tener información, a través de sendos análisis descriptivos univariante y bivariante, de los individuos encuestados sobre el objeto del estudio. Para validar los modelos y contrastar las hipótesis planteadas, se ha utilizado el análisis de fiabilidad y validación de las escalas de medición seleccionadas (Alpha de Cronbach); el análisis factorial exploratorio, para comprobar la dimensionalidad y validez convergente de las escalas de medida; el análisis factorial confirmatorio, para validar la idoneidad de los modelos de medida propuestos; la regresión logística, para comprobar la validez del modelo general de la probabilidad de la compra o no compra de productos de Comercio Justo; y la regresión lineal múltiple, para comprobar la validez de los modelos específicos de intención de compra futura en los segmentos de compradores y de no compradores. Para realizar todos estos análisis, se han utilizado las herramientas informáticas SPSS v21 y AMOS. Las principales conclusiones del trabajo son: (1) que se deben establecer unos criterios claros que definan quién es quién en el movimiento de Comercio Justo, sus fines, sus objetivos, los productos que comercializan, así como su funcionamiento y desarrollo en España; (2) que, a pesar de las grandes ventajas y posibilidades del Comercio Justo, hay una falta de demanda de estos productos por parte de los consumidores responsables, debido principalmente a la falta de información-comunicación sobre el propio movimiento, y, muy especialmente, a la falta de información sobre los productos, los canales de comercialización, las políticas de precios, las políticas de comunicación, etc., y a la necesidad de que estos productos estén accesibles en los lugares donde los consumidores hacen su compra habitual; y (3) que el Comercio Justo español debe afrontar una serie de desafíos, como son la coordinación entre las diferentes organizaciones que participan en su desarrollo; la sensibilización de los consumidores; la creación de una imagen de marca que defina de una manera clara y sencilla qué es el Comercio Justo; la orientación al cliente y no al producto; y extender la red de comercialización de productos de Comercio Justo a los canales donde los consumidores hacen su compra habitualmente. ABSTRACT Global consumption, the driver of economic growth and development of nations, is not the same for all countries, since its effects have been different on people coming from the North or the South. This is due mainly to two reasons: firstly, because they have developed complex and different lifestyles and aspirations, which have led to significant differences between individuals of one country and another and secondly, because they lack social and ethical values. Given this situation, society as a whole should be aware of this fact, and through responsible consumption and a greater knowledge of trade relations between countries, should opt for consuming products produced with criteria of justice and equity. Fair Trade began as a way to help reach these goals of equity, solidarity, justice and ethics. In the case of Spain it did not start until 20 years later, in the eighties. Although today sales of Fair Trade products are growing at a good rate, they are still below that of other European countries, for four reasons: (1) unawareness of this social movement; (2) the difficult access to these products; (3) insufficient government support; (4) the limited research carried out to analyse Fair Trade from the perspective of demand, resulting in a lack of knowledge about this type of consumer and their purchasing motivations. Based on the above, the present study is designed as an exploratory investigation, aimed at analyzing the profile of consumers and non-consumers of Fair Trade, their motivations for buying and not buying, as well as the variables which influence future purchase intention in both the current consumer segment, and the non-user segment of such products. To carry out this study we have used, on the one hand, a qualitative methodology, to obtain information about the views and attitudes involved in the purchase decision process; and on the other, a quantitative methodology, through an online survey of 6,500 individuals, which provided information through two separate univariate and bivariate descriptive analysis, of the individuals interviewed about the object of this study. To validate the models and contrast hypotheses, we have used the reliability analysis and validation of the selected measurement scales (Cronbach's Alpha); exploratory factor analysis to verify the dimensionality and convergent validity of the measurement scales; confirmatory factor analysis to validate the adequacy of the models of measurement proposed; logistic regression, to verify the validity of the general model of the probability of buying or not buying Fair Trade products; and multiple linear regression to test the validity of specific models in future purchase intention in the segments of buyers and non-buyers. To carry out these analyses, we used SPSS v21 software tools and AMOS. The principal conclusions of the investigation are: (1) the need to establish clear criteria which define who is who in the Fair Trade movement, its goals, objectives, the products they sell, as well as its operation and development in Spain; (2) that despite the great advantages and possibilities of Fair Trade, there is a lack of demand for these products by responsible consumers, mainly due to the lack of information-communication about the movement itself, and especially on the range of products, sales channels, pricing policies, communication policies, etc., and the need for these products to be available in places where consumers make their usual purchase; and (3) that Spanish Fair Trade must address a number of challenges such as: coordination between the different organizations involved in trade development; consumer awareness; creation of a brand image that defines in a clear and simple way what Fair Trade is; focus on the customer rather than the product; and expansion of the network of Fair Trade sales outlets to include the channels where consumers usually make their purchases.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

Background and Objective: To examine if commonly recommended assumptions for multivariable logistic regression are addressed in two major epidemiological journals. Methods: Ninety-nine articles from the Journal of Clinical Epidemiology and the American Journal of Epidemiology were surveyed for 10 criteria: six dealing with computation and four with reporting multivariable logistic regression results. Results: Three of the 10 criteria were addressed in 50% or more of the articles. Statistical significance testing or confidence intervals were reported in all articles. Methods for selecting independent variables were described in 82%, and specific procedures used to generate the models were discussed in 65%. Fewer than 50% of the articles indicated if interactions were tested or met the recommended events per independent variable ratio of 10: 1. Fewer than 20% of the articles described conformity to a linear gradient, examined collinearity, reported information on validation procedures, goodness-of-fit, discrimination statistics, or provided complete information on variable coding. There was no significant difference (P >.05) in the proportion of articles meeting the criteria across the two journals. Conclusion: Articles reviewed frequently did not report commonly recommended assumptions for using multivariable logistic regression. (C) 2004 Elsevier Inc. All rights reserved.