Constraints on muscular performance: trade-offs between power output and fatigue resistance

An important functional and evolutionary constraint on the physical performance of vertebrates is believed to be the trade-off between speed and endurance capacity. However, despite the pervasiveness of physiological arguments, most studies have found no evidence of the trade-off when tested at the whole-animal level. We investigated the existence of this trade-off at the whole-muscle level, the presumed site of this physiological conflict, by examining inter-individual variation in both maximum power output and fatigue resistance for mouse extensor digitorum longus (EDL) muscle using the work-loop technique. We found negative correlations between several measures of in vitro maximum power output and force production with fatigue resistance for individual mouse EDL muscles, indicating functional trade-offs between these performance parameters. We suggest that this trade-off detected at the whole-muscle level has imposed an important constraint on the evolution of vertebrate physical performance.

Interindividual variation of isolated muscle performance and fibre-type composition in the toad Bufo viridus

Interindividual analyses of physiological performance represent one of the most powerful tools for identifying functional positive and negative linkages between various performance traits. In this study we investigated functional linkages in the whole-gastrocnemius performance of juvenile Bufo viridis by examining interindividual variation in in vitro muscle performance and muscle fibre-type composition. We used the work-loop technique to investigate the maximum in vitro power output and fatigue resistance of the gastrocnemius muscle during repeated sets of three cycles at the cycle frequency of 5 Hz, simulating an intermittent style of locomotion. We found several significant correlations between different measures of in vitro muscle performance, including a negative correlation between maximum net power output and fatigue resistance of power, indicating functional trade-offs between these performance traits. We also investigated the extent of individual variation in the proportions of different fibre types, and tested for correlations between individual variation in muscle fibre-type composition and the previously measured isolated muscle performance. Fast glycolytic fibres represented 84.0+/-3.4% of the muscle, while the combined slow oxidative and fast oxidative-glycolytic fibres represented 16+/-3.4%. We found no significant correlations between measures of in vitro muscle performance and the proportion of different fibre types in the gastrocnemius muscle. However, despite this lack of correlation between whole-muscle performance and muscle fibre-type composition data, we suggest the functional linkages detected between different measures of in vitro muscular performance have important ecological and evolutionary consequences.

Interindividual Differences in Leg Muscle Mass and Pyruvate Kinase Activity Correlate with Interindividual Differences in Jumping Performance of Hyla multilineata

Frog jumping is an excellent model system for examining the structural basis of interindividual variation in burst locomotor performance. Some possible factors that affect jump performance, such as total body size, hindlimb length, muscle mass, and muscle mechanical and biochemical properties, were analysed at the interindividual (intraspecies) level in the tree frog Hyla multilineata. The aim of this study was to determine which of these physiological and anatomical variables both vary between individuals and are correlated with interindividual variation in jump performance. The model produced via stepwise linear regression analysis of absolute data suggested that 62% of the interindividual variation in maximum jump distance could be explained by a combination of interindividual variation in absolute plantaris muscle mass, total hindlimb muscle mass ( excluding plantaris muscle), and pyruvate kinase activity. When body length effects were removed, multiple regression indicated that the same independent variables explained 43% of the residual interindividual variation in jump distance. This suggests that individuals with relatively large jumping muscles and high pyruvate kinase activity for their body size achieved comparatively large maximal jump distances for their body size.

Layered double hydroxide nanomaterials as potential cellular drug delivery agents

This paper briefly reviews the recent progress in using layered double hydroxide (LDH) nanomaterials as cellular delivery agents. The advantages of LDHs as cellular delivery agents are summarized, and the processes of interaction/de-intercalation of anionic drugs (genes) into/from LDH nanoparticles are discussed. Then the cellular delivery of LDH-drug (gene) nanohybrids and subsequent intracellular processes are presumably proposed. At the end, some challenges and remarks for efficient delivery of drugs (genes) via LDH nanoparticles are provided to the best of our knowledge.

Systematic changes in the duration and precision of interception in response to variation of amplitude and effector size

The results of two experiments are reported that examined how performance in a simple interceptive action (hitting a moving target) was influenced by the speed of the target, the size of the intercepting effector and the distance moved to make the interception. In Experiment 1, target speed and the width of the intercepting manipulandum (bat) were varied. The hypothesis that people make briefer movements, when the temporal accuracy and precision demands of the task are high, predicts that bat width and target speed will divisively interact in their effect on movement time (MT) and that shorter MTs will be associated with a smaller temporal variable error (VE). An alternative hypothesis that people initiate movement when the rate of expansion (ROE) of the target's image reaches a specific, fixed criterion value predicts that bat width will have no effect on MT. The results supported the first hypothesis: a statistically reliable interaction of the predicted form was obtained and the temporal VE was smaller for briefer movements. In Experiment 2, distance to move and target speed were varied. MT increased in direct proportion to distance and there was a divisive interaction between distance and speed; as in Experiment 1, temporal VE was smaller for briefer movements. The pattern of results could not be explained by the strategy of initiating movement at a fixed value of the ROE or at a fixed value of any other perceptual variable potentially available for initiating movement. It is argued that the results support pre-programming of MT with movement initiated when the target's time to arrival at the interception location reaches a criterion value that is matched to the pre-programmed MT. The data supported completely open-loop control when MT was less than between 200 and 240 ms with corrective sub-movements increasingly frequent for movements of longer duration.

Effects of relational policies in export channels

Two key causes of failure for exporters are (1) the availability of adequate resources at the point of entry, and, (2) the quality of the exporter-foreign distributor relationship. Generally, export research has found that, as foreign distributor relationship-specific investments increase and as relational bonds are established, performance improves (e.g., Bello and Gilliland 1997). However, investments and the quality of the relationship are challenged by the foreign distributor���s motivation to participate in the relationship. One way exporters deal with this issue is by developing trade policies, which we refer to as “relational policies,” that are intended to motivate relational behaviors on the part of the foreign distributor.

Exploring the dimensions and transactional outcomes of incomplete business contracts

With an increased emphasis on outsourcing and shortening business cycles, contracts between firms have become more important. Carefully written contracts contribute to the efficiency and longevity of inter-firm relationships as they may constrain opportunism and are often a less costly governance mechanism than maintaining complex social relationships (Larson 1992). This exploratory examination adds to our understanding of how incomplete contracts affect interorganizational exchange. First, we consider the multiple dimensions of contract constraints (safeguards). We also investigate the extent that constraints affect decisions to enforce the relationship by delaying payments, and whether the decision is efficient. Finally, we examine the extent the constraints are effective (and ineffective) at reducing transaction problems associated with enforcement. Based on 971 observations of transactions using explicit, written terms and other secondary data in the context of IT transaction in The Netherlands we test our research propositions.

Radial deformation measurement of a cylinder under compression using multicore fibre

A multicore fibre (MCF) sensor to measure the radial deformation of a compliant cylinder under compression is presented. The sensor is connectorised and need not be permanently bonded to the test object. A differential measurement technique using FBGs written into the MCF makes the sensor temperature insensitive. FBG measurement of axial strain of a cylinder under compression is also reported.

A paradigm shift for mobile interaction:a decade later

In the proceedings of CASCON'2003 we published an article entitled "A Paradigm Shift: Alternative Interaction Techniques for Use with Mobile & Wearable Devices" and were honoured to receive the Best Paper Award for that year's conference. A decade on, we are equally honoured to have the same paper recognised as the Most Influential Paper of the 2003 conference. To this end, we have been asked to provide a brief overview of our intervening research in relation to that original publication, and so that is the purpose of this extended abstract.

Radial deformation measurement of a cylinder under compression using multicore fibre

A multicore fibre (MCF) sensor to measure the radial deformation of a compliant cylinder under compression is presented. The sensor is connectorised and need not be permanently bonded to the test object. A differential measurement technique using FBGs written into the MCF makes the sensor temperature insensitive. FBG measurement of axial strain of a cylinder under compression is also reported.

Developing Ecological Criteria for Prescribed Fire in South Florida Pine Rockland Ecosystems

The pine rocklands of South Florida, characterized by a rich herbaceous flora with many narrowly endemic taxa beneath an overstory of south Florida slash pine (Pinus elliottii var. densa), are found in three areas: the Miami Rock Ridge of southeastern peninsular Florida, the Lower Florida Keys, and slightly elevated portions of the southern Big Cypress National Preserve. Fire is an important element in these ecosystems, since in its absence the pine canopy is likely to be replaced by dense hardwoods, resulting in loss of the characteristic pineland herb flora. Prescribed fire has been used in Florida Keys pine forests since the creation of the National Key Deer Refuge (NKDR), with the primary aim of reducing fuels. Because fire can also be an effective tool in shaping ecological communities, we conducted a 4-year research study which explored a range of fire management options in NKDR. The intent of the study was to provide the Fish and Wildlife Service and other land managers with information regarding when and where to burn in order to perpetuate these unique forests.

Predator���prey naïveté, antipredator behavior, and the ecology of predator invasions

We present a framework for explaining variation in predator invasion success and predator impacts on native prey that integrates information about predator���prey naïveté, predator and prey behavioral responses to each other, consumptive and non-consumptive effects of predators on prey, and interacting effects of multiple species interactions. We begin with the ‘naïve prey’ hypothesis that posits that naïve, native prey that lack evolutionary history with non-native predators suffer heavy predation because they exhibit ineffective antipredator responses to novel predators. Not all naïve prey, however, show ineffective antipredator responses to novel predators. To explain variation in prey response to novel predators, we focus on the interaction between prey use of general versus specific cues and responses, and the functional similarity of non-native and native predators. Effective antipredator responses reduce predation rates (reduce consumptive effects of predators, CEs), but often also carry costs that result in non-consumptive effects (NCEs) of predators. We contrast expected CEs versus NCEs for non-native versus native predators, and discuss how differences in the relative magnitudes of CEs and NCEs might influence invasion dynamics. Going beyond the effects of naïve prey, we discuss how the ‘naïve prey’, ‘enemy release’ and ‘evolution of increased competitive ability’ (EICA) hypotheses are inter-related, and how the importance of all three might be mediated by prey and predator naïveté. These ideas hinge on the notion that non-native predators enjoy a ‘novelty advantage’ associated with the naïveté of native prey and top predators. However, non-native predators could instead suffer from a novelty disadvantage because they are also naïve to their new prey and potential predators. We hypothesize that patterns of community similarity and evolution might explain the variation in novelty advantage that can underlie variation in invasion outcomes. Finally, we discuss management implications of our framework, including suggestions for managing invasive predators, predator reintroductions and biological control.

Professionalism and Ethics in Hospitality

In their discussion - Professionalism and Ethics in Hospitality - by James R. Keiser, Associate Professor and John Swinton, Instructor, Hotel, Restaurant and Institutional Management, The Pennsylvania State University, Keiser and Swinton initially offer: “Referring to “the hospitality profession” necessitates thinking of the ethics of that profession and how ethics can be taught. The authors discuss what it means for the hospitality industry to be a profession.” The authors will have you know, a cursory nod to the term or description, profession and/or professional, is awarded to the hospitality industry at large; at least in an academic sense. Keiser and Swinton also want you to know that ethics, and professionalism are distinctly unique concepts, however, they are related. Their intangible nature does make them difficult, at best, to define, but ethics in contemporary hospitality has, to some degree, been charted and quantified. “We have left the caveat emptor era, and the common law, the Uniform Commercial Code, and a variety of local ordinances now dictate that the goods and services hospitality offers carry an implied warranty of merchantability,” the authors inform you. About the symbiotic relationship between ethics and professionalism, the authors say this: The less precise a code of ethics goes, the general rule, the fewer claims the group has to professional status.” The statement above may be considered a cornerstone principle. “However, the mere existence of an ethical code (or of professional status, for that matter) does not ensure ethical behavior in any group,” caution Keiser and Swinton. “Codes of ethics do not really define professionalism except as they adopt a group's special, arcane, exclusionary jargon. Worse, they can define the minimum, agreed-upon standards of conduct and thereby encourage ethical corner-cutting,” they further qualify the thought. And, in bridging academia, Keiser and Swinton say, “Equipped now with a sense of the ironies and ambiguities inherent in labeling any work "professional," we can turn to the problem of instilling in students a sense of what is professionally ethical. Students appear to welcome this kind of instruction, and while we would like to think their interest comes welling up from altruism and intellectual curiosity rather than drifting down as Watergate and malpractice fallout, our job is to teach, not to weigh the motives that bring us our students, and to provide a climate conducive to ethical behavior, not supply a separate answer for every contingency.” Keiser and Swinton illustrate their treatise on ethics via the hypothetical tale [stylized case study] of Cosmo Cuisiner, who manages the Phoenix, a large suburban restaurant. Cosmo is “…a typical restaurant manager faced with a series of stylized, over-simplified, but illustrative decisions, each with its own ethical skew for the students to analyze.” A shortened version of that case study is presented. Figure 1 outlines the State Restaurant Association Code of Ethics.