• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 1941
  • 582
  • 218
  • 207
  • 182
  • 164
  • 70
  • 55
  • 49
  • 39
  • 38
  • 31
  • 19
  • 15
  • 12
  • Tagged with
  • 4431
  • 561
  • 459
  • 319
  • 315
  • 294
  • 286
  • 265
  • 204
  • 198
  • 198
  • 187
  • 179
  • 169
  • 167
  • 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

HistÃria de vida do caranguejo Goniopis Cruentata(Latreille, 1803) em um manguezal do nordeste brasileiro / Life history of the crab Goniopsis cruentata (Latreille, 1803) in a mangrove from Northeast Brazil.

Josà Jonathas Pereira Rodrigues de Lira 27 February 2012 (has links)
FundaÃÃo Cearense de Apoio ao Desenvolvimento Cientifico e TecnolÃgico / A histÃria de vida de um organismo envolve a interaÃÃo entre manutenÃÃo, crescimento e reproduÃÃo. Essa teoria se propÃe a explicar as variaÃÃes nos aspectos populacionais de uma espÃcie em funÃÃo das condiÃÃes e recursos disponÃveis no ambiente, sendo a base teÃrica para estudos relativos à dependÃncia de densidade. A densidade à um fator regulador da dinÃmica populacional por promover competiÃÃo. O presente estudo se propÃe a responder a seguinte questÃo: a densidade influencia o tamanho, a maturidade sexual e a proporÃÃo sexual em uma populaÃÃo do caranguejo Goniopsis cruentata?As condiÃÃes ambientais influenciam os aspectos biolÃgicos e potencializam os efeitos da densidade nesta espÃcie? ExpediÃÃes de campo foram conduzidas, mensalmente, de janeiro a novembro de 2011, nos municÃpios de Aracati e Fortim, CearÃ, Brasil. Os animais foram coletados manualmente em duas estaÃÃes de coleta, Alfredo (A) e Caldeleiro (C), em uma Ãrea de 400m para cada estaÃÃo, durante 40 minutos. Os indivÃduos foram sexados e mensurados quanto a sua largura de carapaÃa, comprimento do gonÃpodo nos machos e largura do abdÃmen nas fÃmeas. Dez indivÃduos de cada estaÃÃo foram submetidos a processamento histolÃgico para determinaÃÃo do estÃgio de desenvolvimento gonadal. A densidade foi calculada pelo nÃmero de indivÃduos por Ãrea (ind/mÂ) e correlacionada aos fatores abiÃticos: pluviosidade, pH e salinidade do solo. Os espÃcimes foram distribuÃdos em classes de tamanho, por estaÃÃo e por sexo. TambÃm foram calculadas a razÃo sexual e as maturidades morfolÃgica e fisiolÃgica. Os fatores abiÃticos de pluviosidade, pH e salinidade do solo foram mensurados e correlacionados à densidade de cada estaÃÃo. A densidade da estaÃÃo A foi maior que a da estaÃÃo C, o que pode ocorrer em funÃÃo da maior disponibilizaÃÃo de nutrientes nesta Ãrea, devido ao pH mais baixo que a estaÃÃo C. A pluviosidade se correlacionou com a densidade em C, devido a esta estaÃÃo apresentar topografia menos elevada, sofrendo maior influencia do nÃvel de Ãgua do rio. A salinidade do solo nÃo apresentou diferenÃas entre as estaÃÃes. O tamanho mÃdio entre machos nÃo variou entre as estaÃÃes, ao contrÃrio do que ocorreu em fÃmeas, com tamanho mÃdio maior na estaÃÃo com mais densa. Em ambos os sexos, os tamanhos mÃximos maiores foram observados na estaÃÃo com maior densidade, indicando menor mortalidade entre adultos e, assim, possibilitando retardo da maturidade nesta estaÃÃo. A distribuiÃÃo em classes de tamanho nÃo divergiu entre as estaÃÃes, mas apresentou uma tendÃncia a ser bimodal na estaÃÃo com maior densidade e unimodal na estaÃÃo com densidade menor. Esse resultado pode indicar influÃncia da densidade na distribuiÃÃo em classes de tamanho. A maturidade sexual foi antecipada na estaÃÃo com densidade menor e retardada na estaÃÃo com densidade maior, como previsto pela teoria de histÃria de vida. Essa tÃtica pode ser resultado de taxas de mortalidade maiores entre juvenis na estaÃÃo mais densa e maiores entre adultos na estaÃÃo menos densa. A proporÃÃo sexual nÃo diferiu entre as estaÃÃes, mas houve tendÃncia de maior proporÃÃo de machos na Ãrea com maior densidade, o que pode acarretar em maior competiÃÃo entre machos pelas fÃmeas. A maior proporÃÃo de fÃmeas observada na Ãrea de densidade menor pode proporcionar uma limitaÃÃo espermÃtica. Os resultados obtidos para o caranguejo Goniopsis cruentata no presente estudo corroboram as previsÃes da teoria de histÃria de vida: (1) em populaÃÃes com densidade menor, a maturidade sexual à antecipada e os organismos alcanÃam tamanhos menores, e em densidade maior a maturidade à retardada com organismos atingindo tamanhos maiores; (2) A distribuiÃÃo em classes de tamanho foi diferente entre as estaÃÃes de coleta, indicando influencia da densidade populacional. / The life history traits of an organism are the result of trade-offs between maintenance, growth and reproduction. This theory aims to explain the variations in the population aspects of a given species in function of the conditions and available resources in the environment, being the theoretical basis for studies dealing on the dependence of density. The density is a factor regulating the population dynamics since it promotes the competition for resources and, thus, it influences the attributes of life history. The present study aims to answer the following questions: does density influence size and sexual maturity in a population of the crab Goniopsis cruentata? Do the environmental conditions influence the biological aspects and increase the density effects on this species? Field work was conducted from January to November 2011, in the Municipalities of Aracati and Fortim (CearÃ, Brazil). The crabs were manually collected in two sampling stations, Alfredo and Caldeleiro, in an area of 400m for each station, during 40 minutes. The individuals collected were sexed and measured at the carapace width, gonopod length (males) and abdomen width (females). Ten individuals from each station were submitted to a histological procedure to determine the stage of gonad development. Density was calculated as the number of individuals per area (ind/mÂ). The individuals collected were distributed in size classes, by station and by sex. Morphological and physiological maturities were also calculated. Abiotic factors such as rainfall, pH and salinity of the soil were measured and correlated to the density of each station. The density of the Alfredo station was higher than the Caldeleiro station one, which may occur due to the greater availability of nutrients at this area, due to the lower pH than the Caldeleiro station. The rainfall was correlated to the density at Caldeleiro, due to the fact that this station presented a lower topography, suffering a greater influence of the level of the river. The salinity of the soil did not show differences between the stations. Males mean size did not differ between the stations, contrary to what occurred in females, with larger mean size at the highest density local. In both sexes, the larger maximum sizes were observed in the station with higher density, showing lower mortality between adults and, thus, allowing a delay in maturation at this local. The size class distribution did not differ between the stations, but presented a tendency to be bimodal at the station with higher density and unimodal at the station with lower density. This result may indicate the influence of the density in the distribution by size classes. The sexual maturity was anticipated in the lowest density local and delayed in the highest density local, as predicted by the life history theory. This pattern may be a result of higher mortality rates in juveniles at the highest density local and higher mortality rates between adults at the less dense area. The larger proportion of females observed at the highest density area may provide a spermatic limitation. Males, copulating with a higher number of females, do not have the capacity to produce spermatozoids to fertilize all of them. The results of the present study corroborate the predictions of the life history theory: (1) in populations with lower density, sexual maturity is anticipated and organisms attain smaller sizes, and in populations with higher density maturity is delayed and organisms attain larger sizes; (2) the distribution in size classes was different between the sampling areas, showing the influence of the population density.
532

Evaluation of Five Effect Size Measures of Measurement Non-Invariance for Continuous Outcomes

January 2019 (has links)
abstract: To make meaningful comparisons on a construct of interest across groups or over time, measurement invariance needs to exist for at least a subset of the observed variables that define the construct. Often, chi-square difference tests are used to test for measurement invariance. However, these statistics are affected by sample size such that larger sample sizes are associated with a greater prevalence of significant tests. Thus, using other measures of non-invariance to aid in the decision process would be beneficial. For this dissertation project, I proposed four new effect size measures of measurement non-invariance and analyzed a Monte Carlo simulation study to evaluate their properties and behavior in addition to the properties and behavior of an already existing effect size measure of non-invariance. The effect size measures were evaluated based on bias, variability, and consistency. Additionally, the factors that affected the value of the effect size measures were analyzed. All studied effect sizes were consistent, but three were biased under certain conditions. Further work is needed to establish benchmarks for the unbiased effect sizes. / Dissertation/Thesis / Doctoral Dissertation Psychology 2019
533

Size-Weight Scaling in Healthy Young and Old Adults

Capper, Alyssa Lynn 01 July 2013 (has links)
Visual analysis of an object's size can be used to determine the lifting forces we program to lift the object so that the resulting movements achieve the goals of the lift. These forces are scaled or specified prior to the object moving, that is, before sensory feedback information about the object's weight is available. Sensorimotor memories are relied on to provide relevant information about an object's density and weight if the object was previously manipulated. It is well established that young adults accurately scale their forces based on visual size cues. The purpose of this study was to determine if old adults scale their forces to the size of the object or if they rely on sensorimotor memory of the previous object's weight. There are reports of impaired visuomotor programing for grasp and lift in old adults. In the present study old and young subjects were required to lift four different sized bottles of constant density from a force plate and then place the object on a shelf. Two experiments were performed. Experiment one featured blocks of lifts for three bottles in the following order: large, small and medium. Experiment two took place fifteen minutes after experiment one and featured a bottle slightly larger than the medium bottle used at the end of the experiment one. The second experiment addressed whether imperceptible changes in size cause changes in predictive force scaling. Peak load force rate in the first force pulse (prior to lift-off) was measured for each lift of the objects with the focus being on the initial and last lift of each bottle. Both experiments presented a significant effect for bottle size on lift force rates. This result was found regardless of age. It provides additional support that young adults accurately scale their lift force rate based on the visual size cues of the object. Old adults also demonstrated scaling of their lift force rates based on bottle size which failed to support the hypothesis that old adults would merely reproduce their lift force rates from the previous lift with a different object. While both young and old scale lift forces to object size, the old demonstrated a trend for utilizing high lift force rates throughout the experiment as well as greater differences in lift force rate between the initial lift with an object and the final lift with the same object. Most subjects utilized a target strategy in which they produced a single peak lift force rate pulse. This is indicative of a neural representation of the weight of the object being utilized to program the lift force rate. The remaining subjects exhibited a probing strategy that features several step-wise increases in lift force rate until the object is lifted off. This represents a more cautious approach to lifting novel objects. Our results indicate that old adults, much like young adults, are able to scale their forces based on visual size cues.
534

Historical Trends in the Size of US Olympic Female Artistic Gymnasts

Sands, William A., Slater, Cindy, McNeal, Jeni R., Murray, Steven Ross, Stone, Michael H. 01 December 2012 (has links)
Purpose: To assess the historical changes in the size and age of the US women’s Olympic gymnastics teams from 1956 to 2008. Methods: The official records from the US Olympic Committee and USA Gymnastics of Olympic team members were assessed at 2 levels: individual height, mass, age, and body-mass index (BMI) and the team performance scores and rankings. Fourteen Olympic teams with a total of 106 team members, including the alternates, were included. Trend analyses were conducted using linear and polynomial models. Results: Simple linear correlations indicated that since 1956, height, mass, age, BMI, and team Olympic rank have been declining. However, second-order polynomial curve fits indicated that in the last 4 Olympic Games the members of the US women’s gymnastics teams have been getting larger. Conclusion: Women Olympic gymnasts were getting smaller through approximately the 1980s and early 1990s. Since then the size of these gymnasts has increased. The minimum-age rule modifications may have played a role in athlete size changes along with a shift from the near dominance of the former communist Eastern Bloc.
535

The Effects of Ambiguous Appearance-related Feedback on Body Image, Mood States, and Intentions to Use Body Changes Strategies in College Women

Herbozo, Sylvia 24 May 2007 (has links)
Previous research has demonstrated the influential role of physical appearance-related feedback in the development of body image and eating disturbances. Teasing and negative feedback have been established as strong correlates and predictors of body dissatisfaction, maladaptive eating behaviors, and psychological distress. However, very little is known about ambiguous appearance-related feedback and its impact on others. The current study sought to explore this area with an experimental study to examine the effects of ambiguous appearance-related feedback on body image, mood states, and intentions to use body change strategies. Undergraduate women (N=146) were randomly assigned to an ambiguous appearance-related or ambiguous nonappearance-related feedback condition. Body image, mood states, and intentions to diet, exercise, and use unhealthy weight control methods were assessed before and after feedback was provided by a confederate. Results indicated no significant differences between feedback conditions in body image and mood states. The mean trends for all mood state, with the exception of anger, indicated better mood states after ambiguous appearance-related feedback compared to after ambiguous nonappearance-related feedback. State anger was greater in the ambiguous appearance-related feedback condition suggesting that this particular type of feedback was interpreted in a negative manner. Further, there was a significant difference between feedback conditions for intentions to diet and use bulimic behaviors, with lower levels in the ambiguous appearance-related feedback condition. No significant differences were found for intentions to exercise. State appearance comparison was not shown to mediate the relationship between ambiguous feedback and body image, mood states, or intentions to use body change strategies. Trait appearance satisfaction, appearance comparison, appearance schematicity, and thin ideal internalization were found to moderate the relationship between ambiguous feedback and state depression. Trait appearance comparison moderated the relationship between ambiguous feedback and intentions to use bulimic behaviors. Exploratory analyses conducted with subsamples developed using high versus low levels of trait disturbance showed significant results for the subsample based on trait appearance comparison levels. The findings are discussed in the context of possible reasons for the unexpected responses to the ambiguous appearance-related versus nonappearance-related feedback. The limitations of the study and directions for future research are also noted.
536

What Would You Buy? The Effect of Color and Font Size on Purchase Intention in Digital Advertisements

Castañeda, Julian E 01 January 2019 (has links)
Business professionals have always been intrigued on how to increase purchases through advertisements. Digital advertisements are a new medium in which businesses can utilize to connect with consumers. In this study, participants (n = 126) were presented advertisements on a Qualtrics survey that manipulated color (warm and cool) and font size (large and small) across three product types (electronics, food, and automobiles) to examine the effects of Purchase Intention. There were no significant main effects or interactions of color and font size on Purchase Intention throughout each product type. However, color and font size impacted other factors (Perception, Memory, and Appeal) in the study and showcased significant findings in Electronic and Automobile advertisement product types. These results have implications for the effectiveness of advertising in digital mediums, the power of personally tailoring advertisements to individual consumers, and ultimately converting prospective window shoppers to paying customers.
537

THE IMPACT OF CHILDHOOD SOCIOECONOMIC STATUS ON ADULT REACTIONS TOWARD QUANTITY SURCHARGES

Li, Wenjing 01 January 2018 (has links)
Quantity surcharges have been widespread in the marketplace for decades. However, little is known about what kinds of consumers and under what conditions they are more likely to be impacted by this pricing practice. The current research contributes to the existing literature by investigating how a person’s childhood socioeconomic status affects their reaction toward quantity surcharges during adulthood. Across four studies, we find that childhood socioeconomic status has a positive impact on the purchase of a large and surcharged package size. However, when the economic conditions are threatening, the positive effect of childhood socioeconomic status disappears. The current research also provides a theoretical explanation for the interaction effect of childhood socioeconomic status and economic conditions. The focus on acquiring sufficient resources accounts for the interaction effect.
538

Hemodynamics during pregnancy : a model for cardiac enlargement

Mendelson, David James 01 January 1986 (has links)
Cardiac output Increases by 30-50% during mammal Ian pregnancy. This Increase Is reflected by elevation In both heart rate and stroke volume. The primary mechanism of Increased stroke volume appears to be cardiac enlargement, rather than increased preload, afterload, or contractility. Animal studies have shown that enlargement of the heart occurs prior to an Increase In uterine blood flow during pregnancy and this type of enlargement can be mimicked by sex steroid administration. Systemic vascular resistance greatly decreases during pregnancy and with sex steroid administration. It has been postulated that systemic vascular resistance may be a signal for heart size changes. This study attempted to chronically decrease systemic vascular resistance by administration of an arterial vasodllator (hydralazlne) over a three week period to guinea pigs. At the time of study hemodynamlcs were measured which Included, heart rate, arterial pressure, right atrial pressure and cardiac output. In vitro left ventricular pressure volume relationships were also evaluated, as was total plasma volume.
539

Relationships Between Undigested And Physically Effective Fiber In Lactating Dairy Cow Diets

Smith, Wyatt Alexander 01 January 2019 (has links)
In recent years, economic, social, and environmental factors have encouraged higher forage diets to be fed to dairy cows. Consequently, a better understanding of both the chemical and physical properties of dietary forage fiber is needed. Undigested neutral detergent fiber after 240 hours of fermentation (uNDF240) is the fiber residue remaining after 240 hours of in vitro fermentation and has only recently been defined. Physically effective neutral detergent fiber (peNDF) was defined about two decades ago and is the fraction of dietary fiber with a particle size (i.e., ≥1.18-mm screen) that stimulates chewing behavior, forms the rumen digesta mat, and is resistant to passage from the rumen. To-date, the relationship between these two dietary fiber measurements has not been evaluated. The overall goal of this thesis research was to quantitate the relationship between dietary uNDF240 and peNDF on feed intake, lactational performance, chewing behavior, and the ruminal environment of lactating Holstein dairy cows. The focal study (Chapter 2) investigated the effects of dietary uNDF240 (low or high) and peNDF (low or high) on lactating dairy cows. The four treatments were: 1) low uNDF240, low peNDF (8.8%, 20.1%; LULP; 2) low uNDF240, high peNDF (8.9%, 21.8%; LUHP); 3) high uNDF240, low peNDF (11.4%, 18.6%; HULP); and 4) high uNDF240, high peNDF (11.6%, 22.0%; HUHP). Additionally, a new descriptive term, physically effective uNDF240 (peuNDF240) was calculated as the product of the dietary physical effectiveness factor (pef; % of particles retained on ≥1.18-mm screen with dry sieving) and uNDF240 as a percentage of dry matter (DM). This new descriptive term aimed to integrate the effects of dietary particle size and NDF (in)digestibility. The dietary peuNDF240 concentrations were 5.4% (LULP), 5.8% (LUHP), 5.9% (HULP), and 7.1% (HUHP). The LULP treatment resulted in greater dry matter intake (DMI) and energy corrected milk (ECM), as well as more favorable chewing behavior (i.e., no effect on rumination but less time spent eating) in comparison to the HUHP diet. When comparing the same two treatments, total volatile fatty acid concentration was greater, mean ruminal pH was lower, and NDF turnover rate tended to be greater for the LULP treatment. Milk fat percentage was influenced by dietary uNDF240 with the high uNDF240 diets having an elevated percentage. The LUHP and HULP treatments often did not differ in animal response variables, such as DMI, ECM, mean ruminal pH, and chewing behavior, reflecting their similar dietary peuNDF240 concentration. Importantly, by reducing peNDF of the high uNDF240 treatments, DMI increased to an amount similar to the low uNDF240 treatments. Animal responses were consistently different between the LULP and HUHP treatments as expected: the low uNDF240 diet, chopped more finely, encouraged greater DMI than the high uNDF240 diet chopped coarsely. However, the LUHP and HULP diets with similar peuNDF240 often resulted in similar cow responses, even though the peuNDF240 was obtained differently for each diet. With these diets fed to high-producing cows, it appears that the integration of particle size and indigestibility of fiber using a peuNDF240 measurement is highly related to DMI, ECM yield, chewing behavior, and ruminal environment. In the future, this relationship may prove useful in predicting DMI of lactating dairy cows fed a range of diets differing in uNDF240 and particle size.
540

Fault Scaling And Population Analyses In The Eastern California Shear Zone: Insights Into The Development Of Actively Evolving Plate Boundary Structures

January 2015 (has links)
1 / xu zhou

Page generated in 0.0363 seconds