The fluctuating resource hypothesis explains invasibility, but not exotic advantage following disturbance

Invasibility is a key indicator of community susceptibility to changes in structure and function. The fluctuating resource hypothesis (FRH) postulates that invasibility is an emergent community property, a manifestation of multiple processes that cannot be reliably predicted by individual community attributes like diversity or productivity. Yet, research has emphasized the role of these individual attributes, with the expectation that diversity should deter invasibility and productivity enhance it. In an effort to explore how these and other factors may influence invasibility, we evaluated the relationship between invasibility and species richness, productivity, resource availability, and resilience in experiments crossing disturbance with exotic seed addition in 1-m2 plots replicated over large expanses of grasslands in Montana, USA and La Pampa, Argentina. Disturbance increased invasibility as predicted by FRH, but grasslands were more invasible in Montana than La Pampa whether disturbed or not, despite Montana´s higher species richness and lower productivity. Moreover, invasibility correlated positively with nitrogen availability and negatively with native plant cover. These patterns suggested that resource availability and the ability of the community to recover from disturbance (resilience) better predicted invasibility than either species richness or productivity, consistent with predictions from FRH. However, in ambient, unseeded plots in Montana, disturbance reduced native cover by >50% while increasing exotic cover >200%. This provenance bias could not be explained by FRH, which predicts that colonization processes act on species? traits independent of origins. The high invasibility of Montana grasslands following disturbance was associated with a strong shift from perennial to annual species, as predicted by succession theory. However, this shift was driven primarily by exotic annuals, which were more strongly represented than perennials in local exotic vs. native species pools. We attribute this provenance bias to extrinsic biogeographic factors such as disparate evolutionary histories and/or introduction filters selecting for traits that favor exotics following disturbance. Our results suggest that (1) invasibility is an emergent property best explained by a community´s efficiency in utilizing resources, as predicted by FRH but (2) understanding provenance biases in biological invasions requires moving beyond FRH to incorporate extrinsic biogeographic factors that may favor exotics in community assembly.Fil: Pearson, Dean. United State Forest Service; Estados Unidos. University of Montana; Estados UnidosFil: Ortega, Yvette K.. United State Forest Service; Estados UnidosFil: Villarreal, Diego. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Lekberg, Ylva. University of Montana; Estados UnidosFil: Cock, Marina Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Ciencias de la Tierra y Ambientales de La Pampa. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales. Instituto de Ciencias de la Tierra y Ambientales de La Pampa; ArgentinaFil: Eren, Ozkan. Adnan Menderes Universitesi; TurquíaFil: Hierro, Jose Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Ciencias de la Tierra y Ambientales de La Pampa. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales. Instituto de Ciencias de la Tierra y Ambientales de La Pampa; Argentin

Redefining the Organizational Resilience Construct using a Frame Based Methodology : A New Perspective from the Ecology Based Approach

Open Access via the Elsevier AgreementPeer reviewedPostprin

Development of a task-level robot programming and simulation system

An ongoing project in developing a Task-Level Robot Programming and Simulation System (TARPS) is discussed. The objective of this approach is to design a generic TARPS that can be used in a variety of applications. Many robotic applications require off-line programming, and a TARPS is very useful in such applications. Task level programming is object centered in that the user specifies tasks to be performed instead of robot paths. Graphics simulation provides greater flexibility and also avoids costly machine setup and possible damage. A TARPS has three major modules: world model, task planner and task simulator. The system architecture, design issues and some preliminary results are given

Tree Growth Yield and Fruit Quality of Different Apple Cultivars Trained as Super Spindle

This study was carried out on Topaz, Cooper 39 and Muscat apple cultivars grafted on M27 rootstocks under Tokat ecological conditions during 2008 - 2010. The trees planted in 2.0 m x 0.5 m row spacing (10,000 trees ha-1) and trained to super spindle (SS) training system. The vegetative development, yield and fruit quality performances of the trees supported by wire – pole combination were observed for three years. At the end of the experiment, it was determined that Cooper 39 had a higher trunk cross sectional area (TCA) than Topaz and Muscat. While cumulative yield (CY) per tree and cumulative yield efficiency (CYE) were determined to be the highest in Cooper 39, these values were found to be the lowest in Topaz. CY per hectare over the first three crop year was found to be the highest in Cooper 39 and the yield reached to 142.9 t.ha1. The lowest CY per hectare (69.6 ton ha-1) was determined in Topa

Questioning impact: interconnection between extra-organizational resources and agency of equality and diversity officers

This paper examines the change agency of equality and diversity (E&D) officers with a specific emphasis on the role of extra-organizational influences and resources. The paper is informed by qualitative material collected through interviews with E&D officers from 20 higher education institutions in the UK. The paper offers an evidence-based analysis of the utility of extra-organizational mechanisms and intervention programmes for organizational E&D agenda and for the agentic influence of E&D officers. The paper contributes to both academic literature and policy-making. We present original empirical insights into the change agency of E&D officers by exploring the impact of extra-organizational bodies as potential mechanisms for support and influence. At the policy level, the paper provides evidence on the value of extra-organizational resources and tools that are produced by policy bodies in promoting progressive E&D agendas in organizations

Effects of dietary fish oil and flax seed on cholesterol and fatty acid composition of egg yolk and blood parameters of laying hens

This study was conducted to determine the effects of the supplementation of different levels of fish oil (FO) and flax seed (FS) in the diets of layers on the content of egg yolk fatty acid, cholesterol, blood parameters, egg production and egg quality criteria. In the experiment, a total of 120 Isa-White laying hens of 34 weeks of age were used. Hens were divided randomly into five groups and fed different diets containing no FO and FS; 1.5% FO; 4.32% FS; 1.5% FO+4.32% FS and 8.64% FS for eight weeks. A significant decrease in yolk cholesterol content (mg/g yolk) was found in the eggs from hens fed the diets containing 1.5 % FO and 8.64% FS as compared with the control. Adding FO and FS to diets significantly increased the total omega-3 fatty acids in eggs at 28 (phase 1) and 56 (phase 2) days of the trial. By contrast, the addition of both FO and FS to diets had no effect on total omega-6 fatty acids in eggs in phase 1. But dietary 1.5% FO, 4.32% FS and 1.5% FO+4.32% FS supplementation decreased significantly the total omega-6 fatty acids compared to the controls in phase 2. The linolenic acid content of eggs was the highest in eggs from hens fed the diet with added FS, while docosahexaenoic acid content was the highest in eggs from hens fed diets with added FO. Dietary supplementation of FO and FS did not significantly affect the concentrations of serum trigliceride and high density lipoprotein. The serum cholesterol level of hens fed diets containing 1.5% FO+4.32% FS and 8.64% FS was lower than the control group. The addition of FO and FS to diets did not cause any negative effect on some egg quality criteria such as egg weight, yolk weight, yolk ratio, albumen weight, albumen ratio, shell weight, shell ratio, shell strength and shell thickness. The egg production of hens fed a diet containing 4.32% FS was significantly higher than the controls. Feed intake and feed conversion were not affected by all treatments. Keywords: Omega-3 fatty acids, Cholesterol eggs, Flax seed, Fish oil South African Journal of Animal Science Vol.33(4) 2003: 266-27

Protective effect of antioxidant enzymes against drug cytotoxicity in MCF-7 cells

Aim: To evaluate protective effect of antioxidant enzymes against epirubicin-HCI (EPI) cytotoxicity in vitro. Materials and Methods: Viability of MCF-7 cells treated with EPI was measured using the MTT test. Glutathione (GSH), protein content and enzymatic activity were measured spectrophotometrically. NADPH — dependent cytochrome P-450 reductase (NADPH-CYP-450) and glutathione S-transferase pi (GST-pi) expression in MCF-7 cells were determined by Western blot analysis. Results: The IC50 values of EPI in MCF-7 cells were 1.0, 0.7 and 0.5 ng/ml respectively for 24, 48 and 72 h applications. Simultaneously enzymatic activity of glutathione S-transferase, glutathione peroxidase, GSH and expression of GST-pi, NADPH-CYP-450 reductase were increased in EPI (1 ng/ml) — treated cells at the end of the 24 h incubation. Addition of superoxide dismutase, catalase and GSH decreased cytotoxicity of EPI. Conclusion: We hypothesized that the production of reactive oxygen species and hydrogen peroxide as result of EPI treatment can cause cytotoxicity in MCF-7 cells and antioxidant enzymes protect the cells against this process.Цель: оценить защитный эффект антиоксидантных ферментов против цитотоксичности эпирубицина-HCI (ЕРІ) in vitro. Материалы и методы: жизнеспособность клеток линии MCF-7, обработанных ЕРІ, оценивали при помощи MTT-метода. Содержание глутатиона (GSH), концентрацию белка и ферментативную активность измеряли спектрофотометрически. Экспрессию NADPH-зависимой цитохром P-450 редуктазы (NADPH-CYP-450) и глутатион-S-трансферазы-pi в клетках линии MCF-7 определяли при помощи Вестерн блот-анализа. Результаты: значения IC50 для клеток MСF-7, обработанных EPI, составили 1,0, 0,7 и 0,5 нг/мл при 24, 48 и 72 ч инкубации соответственно. Через 24 ч инкубации клеток с 1 нг/мл ЕРІ отмечали повышение ферментативной активности глутатион-S-трансферазы и глутатион-пероксидазы, а также уровней экспрессии GST-рi и NADPH-CYP-450 редуктазы. Прединкубация клеток с супероксиддисмутазой, каталазой и GSH приводила к снижению цитотоксичности ЕРІ. Выводы: образование свободных радикалов кислорода и перекиси водорода при действии ЕРІ на клетки линии MCF-7 приводит к цитотоксическому эффекту, в снижении которого участвуют антиоксидантные ферменты

Change detection for objects on surfaces slanted in depth

Change detection for objects associated with a surface extended in depth might be more difficult than for a frontal surface if it is easier to shift attention within a frontal surface. On the other hand, previous research has shown that ground surfaces have a special role in organizing the 3-D layout of objects shown against scene backgrounds. In the current study, we examined whether a frontal background or a ground surface background would result in superior change detection performance using a change detection flicker paradigm. In the first experiment, we considered whether background slant affects change detection performance. In Experiment 2, we examined the effect of height in the image on change detection performance. In Experiment 3, we examined change detection performance on slanted ceiling surfaces. The results of these experiments indicate that change detection is more efficient on near-ground planes than on surfaces at intermediate slants or ceiling surfaces. This suggests that any superiority of frontal plane backgrounds in a change detection task may be equivalent to the superiority of a near-ground plane in organizing a scene, with the lowest level of performance occurring for surfaces that are not frontal but further from a ground surface orientation