Investigation of biomechanical factors affecting rowing performance

It was hypothesized that a crew's rowing performance was predictable based on their total propulsive power, synchrony (a real-time comparison of rower propulsive force magnitudes) and total drag contribution (a measure of the rowers' effect on shell drag forces during the recovery), quantities calculated from individual rower's force-time profiles and recovery kinematics. A rowing pair was equipped with transducers to gather shell velocity, propulsive blade force, oar angular position and seat displacement. Eight subjects (four port, four starboard) participated in two rounds of data collection. The first round pairings were random, while the second round pairings were assigned based on Round 1 results. Regression analysis and ANCOVA were used to test the validity of assumptions inherent in the predictive model and, if applicable, explore a linear model predicting rowing performance based on total propulsive power, synchrony and total drag contribution. Total propulsive power, synchrony and total drag contribution were correlated and further were affected by pairing, violating assumptions inherent in the linear model. The original hypothesis was not supported based on these violations. Important findings include (1) performance cannot be predicted using the simple linear model proposed, (2) rowers' force-time profiles are repeatable between trials, with some but not all rowers adapting their force-time profile dependent on their pair partner, presumably in an effort to increase the level of synchrony between the two, and (3) subtle biomechanical factors may play a critical role in performance.     

Ecological factors affecting wetland occupancy by breeding Anatidae in the southwestern mediterranean

Conservation of Anatidae in North Africa is hindered by lack of information concerning population size, population trends, and species-habitat relationships. In this work, we used a 2-year survey data in 25 wetlands distributed throughout Morocco to model duck spatial distribution and to assess the relevance of a set of environmental and anthropogenic factors in predicting site occupancy, by means of Generalized Linear Mixed Models (GLMM). Mallards and Ferruginous ducks were the most commonly detected species, whereas White-Headed Ducks and Common Pochards were the least detected ones. An inter-annual variation in site occupancy was recorded for Ruddy Shelducks, Red-Crested Pochards and White-Headed Ducks. Geographical location (measured mainly as distance to the coastline and altitude) was the major predictor of the occurrence probability of Ruddy Shelducks, Marbled Teals and Red-Crested Pochards, while human presence and habitat features were the most relevant factors in shaping Mallard’s distribution. However, none of the considered environmental and anthropogenic factors explained the distribution patterns of the Ferruginous Duck, Common Pochard and Gadwall. The results of this study clearly show that there are still gaps in our knowledge on factors driving wetland occupancy by breeding Anatidae in Morocco. The pursuit of the investigations, while considering other explanatory factors such as water quality (limnological data), diet, predation, and conservation status, is of great importance to more profoundly understand the dynamics of Moroccan duck populations.     

The main factors affecting the reproductive performance of rabbit does: a review

This paper reviews the main factors affecting the reproductive performance of rabbit does. In the last 15 years the profitability of rabbit farms has increased mainly due to improvements in management and genetic selection but several problems related to animal welfare have also occurred. The replacement and the mortality rates of female per year are very high and the replaced does often show poor body condition and poor health status. The effect of kindling order, litter size, genetic strain, weaning age and reproductive rhythm on the reproductive performance and welfare of females and mechanisms implicated in these effects are discussed. The rabbit doe of modern strains produces a lot of milk with high energetic value, which leads to a mobilization of body fat resulting in a negative energy balance. In the current reproductive rhythms, there is an extensive overlap between lactation and gestation. The resulting energetic and hormonal antagonism reduces the fertility rate and lifespan of the doe. Strategies to optimize these parameters are discussed. An approach that combines various strategies seems to be required to meet these objectives. Since the factors involved in this system are predetermined (genetic strain, environment) the most powerful way to improve doe welfare is to choose a reproductive rhythm more adapted to the physiology of the does.     

Maternal factors affecting reproduction in a breeding colony of cynomolgus macaques (Macaca fascicularis)

A breeding colony of cynomolgus macaques (Macaca fascicularis), composed of imported and colony-born animals and established for 9 years, was evaluated for maternal factors associated with reproductive failure. The factors evaluated included age, gravidity, parity, origin, previous stillbirths, clinical incidents and type of housing. The effects of each factor on pregnancy rate (PR), stillbirth rate (SR), infant mortality rate (IMR) and pregnancy success (PS) were evaluated. The overall colony rates were: PR = 53%, SR = 22%, IMR = 22%, and PS = 60%. Neonatal death rate for the group was 12%. Pregnancy rate was most affected by maternal factors. Clinical incidents occurring during pregnancy were associated with a significant increase in the stillbirth rate, but did not affect infant mortality rate. Maternal age did not affect any of the measures of reproductive output. Pregnancy rate peaked at 6-8 years of age and decreased thereafter, while pregnancy success peaked at 9-11 years of age. Gravidity and parity had a positive linear relationship with pregnancy rate.     

Rotating biological contactors: a review on main factors affecting performance

Rotating biological contactors (RBCs) constitute a very unique and superior alternative for biodegradable matter and nitrogen removal on account of their feasibility, simplicity of design and operation, short start-up, low land area requirement, low energy consumption, low operating and maintenance cost and treatment efficiency. The present review of RBCs focus on parameters that affect performance like rotational speed, organic and hydraulic loading rates, retention time, biofilm support media, staging, temperature, influent wastewater characteristics, biofilm characteristics, dissolved oxygen levels, effluent and solids recirculation, step-feeding and medium submergence. Some RBCs scale-up and design considerations, operational problems and comparison with other wastewater treatment systems are also reported.     

Analysis of factors affecting the performance of partial nitrification in a sequencing batch reactor

The objective of this study was to analyze the factors affecting the performance of partial nitrification in a sequencing batch reactor. During a 140-day long-term operation, influent pH value, dissolved oxygen (DO), and chemical oxygen demand/nitrogen (COD/N) ratio were selected as operating factors to evaluate the maintenance and recovery of nitrite accumulation. Results showed that high DO concentration (2–4 mg/L) could damage nitrite accumulation immediately. However, nitrite accumulation ratio (NAR) could be increased from 1.68?±?1.51 to 35.46?±?7.86 % when increasing the pH values from 7.5 to 8.3 due to the increased free ammonia concentration. Afterwards, stable partial nitrification and high NAR could be recovered when the reactor operated under low DO concentration (0.5–1.0 mg/L). However, it required a long time to recover the partial nitrification of the reactor when the influent COD/N ratios were altered. Fluorescence in situ hybridization analysis implied that ammonium oxidizing bacteria were completely recovered to the dominant nitrifying bacteria in the system. Meanwhile, sludge volumetric index of the reactor gradually decreased from 115.6 to 56.6 mL/g, while the mean diameter of sludge improved from74.57 to 428.8 μm by using the strategy of reducing settling time. The obtained results could provide useful information between the operational conditions and the performance of partial nitrification when treating nitrogen-rich industrial wastewater.     

Characteristics of reproductive biology and proximate factors regulating seasonal breeding in captive golden-headed lion tamarins (Leontopithecus chrysomelas)

Reproduction is highly demanding in terms of energy expenditure, and the costs and benefits associated with postponing or investing in a reproductive effort are crucial determinants of an individual's fitness. Understanding the reproductive potential of a species under varying ecological conditions offers important insights into the dynamics of its social system. This study provides the first detailed analysis of the reproductive potential of wild- and captive-born golden-headed lion tamarins (Leontopithecus chrysomelas) under captive conditions, based on studbook data compiled during 1984-2000. Litters produced by wild-born females breeding in captivity are similar in size to litters observed in the wild, but smaller than litters of captive-born females. The more stringent ecological conditions experienced by wild-born females during maturation may result in a lifelong effect on litter size. However, interbirth intervals are shorter for wild-born than captive-born females. The relatively smaller burden of infant care that results from having smaller litters may allow wild-born females to sustain the next pregnancy sooner. Reproduction in the Brazilian captive population is highly seasonal for both wild-born females and females born in captivity in Brazil. Changes in photoperiod over a year provide a proximate explanation for changes in the proportion of conceptions and births per month. Outside Brazil, breeding occurs year-round, and no clear birth peak is apparent. Information from field reports that could be used to relate this finding to ecological factors, such as resource availability, is unavailable.     

Extinction of top-predator in a three-level food-chain model

 In this paper we extend the Lyapunov functions, constructed by A. Ardito and P. Ricciardi for predator–prey system [1], to the three level food chain models. We first consider a general three-level food-chain model. A criterion for the extinction of top predator will be given. Then we restrict our attentions to the case in which the prey is of logistic growth and predators have Holling’s type II functional responses. Received: 10 October 1997     

Effects of marine algal proximate composition on methane yields

The suitability of differentGracilaria spp. and twoSargassum species for bioconversion to methane was determined through bioassays of methane yield.Gracilaria species and strains were excellent feedstocks for high methane yields, ranging from 0.28 to 0.40 m³ kg^–1 volatile solids added. These yields ranged from 58 to 95% of theoretical stoichiometric yields. Methane yields were highly correlated with acid soluble carbohydrate components of theGracilaria spp. BothSargassum fluitans andS. pteropleuron were poor feedstocks, with methane yields ranging from 0.12 to 0.19 m³ kg^–1 volatile solids added, 27 to 46% of theoretical stoichiometric yields, respectively. The various tissue types of theseSargassum species were also poor feedstocks for anaerobic digestion to methane. While there is no clear explanation for the low methane yields, the twoSargassum spp. appear to contain a high proportion of an insoluble, non-extractable component which may not be available as a substrate for bioconversion to methane.     

In silico investigation of factors affecting the MV imaging performance of a novel water-equivalent EPID

PurposeA Geant4 model of a novel, water-equivalent electronic portal imaging device (EPID) prototype for radiotherapy imaging and dosimetry utilising an array of plastic scintillating fibres (PSFs) has been developed. Monte Carlo (MC) simulations were performed to quantify the PSF-EPID imaging performance and to investigate design aspects affecting performance for optimisation.MethodsUsing the Geant4 model, the PSF-EPID’s imaging performance for 6 MV photon beams was quantified in terms of its modulation transfer function (MTF), noise power spectrum (NPS) and detective quantum efficiency (DQE). Model parameters, including fibre dimensions, optical cladding reflectivity and scintillation yield, were varied to investigate impact on imaging performance.ResultsThe MC-calculated DQE(0) for the reference PSF-EPID geometry employing 30 mm fibres was approximately nine times greater than values reported for commercial EPIDs. When using 10 mm long fibres, the PSF-EPID DQE(0) was still approximately three times greater than that of a commercial EPID. Increased fibre length, cladding reflectivity and scintillation yield produced the greatest decreases in NPS and increases in DQE.ConclusionsThe potential to develop an optimised next-generation water-equivalent EPID with MV imaging performance at least comparable to commercial EPIDs has been demonstrated. Factors most important for optimising prototype design include fibre length, cladding reflectivity and scintillation yield.     

Environmental factors and chemical agents affecting the growth of the pathogenic marine ciliate Uronema nigricans.

The scuticociliate Uronema nigricans is an opportunistically parasitic marine ciliate known to cause disease in some aquacultural environments with epizootics documented from marine larval rearing systems, marine aquaria and in southern bluefin tuna Thunnus macoyii growout enclosures. This study examined growth responses of laboratory cultures of the ciliate and prey bacteria to variations in temperature and salinity, and the efficacy of potential chemotherapeutants for control of U. nigricans infections. Differences in ciliate growth responses were marginal at temperatures of 10 to 25 degrees C and at salinities between 15 and 35 ppt, though 3.5 ppt or less was lethal. Ciliates were found to be sensitive to fluctuations in bacterial densities, which may be a factor in the seasonal occurrence of the ciliate-related disease in tuna. Commonly used chemotherapeutants such as formalin, malachite green and hydrogen peroxide were all effective against the ciliate during in vitro trials.     

Evaluation and optimization of factors affecting the performance of a flow-through system based on immobilized acetylcholineesterase as a biosensor

A flow-through system based on acetylcholineesterase (AChE) was studied. The system was prepared by mixing AChE and a multiwall carbon nanotube (MWCNT). Two important parameters, the ratios of AChE:MWCNT (X₁) and AChE-MWCNT:sol-gel (X₂) were optimized using response surface methodology. The results revealed that an enzyme immobilized within the MWCNT-sol-gel was more effective compared to one conducted with sol-gel. The optimum feed flow rate was 0.4 mL/min and ATChI concentration was found to be 1 mM. The optimum ratios of X₁ and X₂ for immobilization on ceramic packing were 1.07 and 0.43, respectively. The sensitivity of this flow-through system was 1.82 × 10⁻⁵/μM and long-term stability analyzed after 120 days was 74% of initial absorbance. With respect to an incubation time of 14 min, the detection limit for paraoxon was 7.3 × 10⁻¹² mol.     

Ultimate and proximate mechanisms underlying the occurrence of bears close to human settlements: review and management implications

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An overview of proximate factors affecting the nesting behavior of solitary wasps and bees (Hymenoptera: Aculeata) in preexisting cavities in wood

Guilds of Aculeate solitary wasps and bees that nest in preexisting cavities in wood are important components of terrestrial ecosystems because they engage in several ecological interactions (e.g. predation and pollination) with other species of plants and animals. Spatial and temporal variations in richness and abundance of solitary wasps and bees can be related to changes in environmental structure and in the diversity of other groups of organisms. The nesting period of these Aculeata is their most critical life cycle stage. Females of solitary wasp and bee species invest relatively more time constructing and provisioning their nests than do females of social species. Differently from species that nest in the soil or construct exposed nests, the main factors affecting the reproductive success of solitary species nesting in preexisting wood holes are still unknown. Our objective is to provide an overview of the role of proximate causes of nesting failure or success among solitary wasps and bees (Aculeata), for designing effective conservation and management strategies for these Hymenoptera.     

Modelling the niche for a marine vertebrate: a case study incorporating behavioural plasticity,proximate threats and climate change

The integration of satellite telemetry, remotely sensed environmental data, and habitat/environmental modelling has provided for a growing understanding of spatial and temporal ecology of species of conservation concern. The Republic of Cape Verde comprises the only substantial rookery for the loggerhead turtle Caretta caretta in the eastern Atlantic. A size related dichotomy in adult foraging patterns has previously been revealed for adult sea turtles from this population with a proportion of adults foraging neritically, whilst the majority forage oceanically. Here we describe observed habitat use and employ ecological niche modelling to identify suitable foraging habitats for animals utilising these two distinct behavioural strategies. We also investigate how these predicted habitat niches may alter under the influence of climate change induced oceanic temperature rises. We further contextualise our niche models with fisheries catch data and knowledge of fisheries ‘hotspots’ to infer threat from fisheries interaction to this population, for animals employing both strategies. Our analysis revealed repeated use of coincident oceanic habitat, over multiple seasons, by all smaller loggerhead turtles, whilst larger neritic foraging turtles occupied continental shelf waters. Modelled habitat niches were spatially distinct, and under the influence of predicted sea surface temperature rises, there was further spatial divergence of suitable habitats. Analysis of fisheries catch data highlighted that the observed and modelled habitats for oceanic and neritic loggerhead turtles could extensively interact with intensive fisheries activity within oceanic and continental shelf waters of northwest Africa. We suggest that the development and enforcement of sustainable management strategies, specifically multi‐national fisheries policy, may begin to address some of these issues; however, these must be flexible and adaptive to accommodate potential range shift for this species.