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Search Results: 1 - 10 of 223953 matches for " Martial R. Depczynski "
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Spot the Difference: Mimicry in a Coral Reef Fish
Monica Gagliano, Martial Depczynski
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0055938
Abstract: Eyespots on the body of many animals have long been assumed to confer protection against predators, but empirical evidence has recently demonstrated that this may not always be the case and suggested that such markings may also serve other purposes. Clearly, this raises the unresolved question of what functions do these markings have and do they contribute to an individual’s evolutionary fitness in the wild. Here, we examined the occurrence of eyespots on the dorsal fin of a coral reef damselfish (Pomacentrus amboinensis), where these markings are typical of the juvenile stage and fade away as the fish approaches sexual maturation to then disappear completely in the vast majority of, but not all, adult individuals. By exploring differences in body shape among age and gender groups, we found that individuals retaining the eyespot into adulthood are all sexually mature males, suggesting that these eyespots may be an adult deceptive signal. Interestingly, the body shape of these individuals resembled more closely that of immature females than mature dominant males. These results suggest that eyespots have multiple roles and their functional significance changes within the lifetime of an animal from being a juvenile advertisement to a deceptive adult signal. Male removal experiments or colour manipulations may be necessary to establish specific functions.
Unprecedented Mass Bleaching and Loss of Coral across 12° of Latitude in Western Australia in 2010–11
James A. Y. Moore, Lynda M. Bellchambers, Martial R. Depczynski, Richard D. Evans, Scott N. Evans, Stuart N. Field, Kim J. Friedman, James P. Gilmour, Thomas H. Holmes, Rachael Middlebrook, Ben T. Radford, Tyrone Ridgway, George Shedrawi, Heather Taylor, Damian P. Thomson, Shaun K. Wilson
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0051807
Abstract: Background Globally, coral bleaching has been responsible for a significant decline in both coral cover and diversity over the past two decades. During the summer of 2010–11, anomalous large-scale ocean warming induced unprecedented levels of coral bleaching accompanied by substantial storminess across more than 12° of latitude and 1200 kilometers of coastline in Western Australia (WA). Methodology/Principal Findings Extreme La-Ni?a conditions caused extensive warming of waters and drove considerable storminess and cyclonic activity across WA from October 2010 to May 2011. Satellite-derived sea surface temperature measurements recorded anomalies of up to 5°C above long-term averages. Benthic surveys quantified the extent of bleaching at 10 locations across four regions from tropical to temperate waters. Bleaching was recorded in all locations across regions and ranged between 17% (±5.5) in the temperate Perth region, to 95% (±3.5) in the Exmouth Gulf of the tropical Ningaloo region. Coincident with high levels of bleaching, three cyclones passed in close proximity to study locations around the time of peak temperatures. Follow-up surveys revealed spatial heterogeneity in coral cover change with four of ten locations recording significant loss of coral cover. Relative decreases ranged between 22%–83.9% of total coral cover, with the greatest losses in the Exmouth Gulf. Conclusions/Significance The anomalous thermal stress of 2010–11 induced mass bleaching of corals along central and southern WA coral reefs. Significant coral bleaching was observed at multiple locations across the tropical-temperate divide spanning more than 1200 km of coastline. Resultant spatially patchy loss of coral cover under widespread and high levels of bleaching and cyclonic activity, suggests a degree of resilience for WA coral communities. However, the spatial extent of bleaching casts some doubt over hypotheses suggesting that future impacts to coral reefs under forecast warming regimes may in part be mitigated by southern thermal refugia.
Using Age-Based Life History Data to Investigate the Life Cycle and Vulnerability of Octopus cyanea
Jade N. Herwig, Martial Depczynski, John D. Roberts, Jayson M. Semmens, Monica Gagliano, Andrew J. Heyward
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0043679
Abstract: Octopus cyanea is taken as an unregulated, recreationally fished species from the intertidal reefs of Ningaloo, Western Australia. Yet despite its exploitation and importance in many artisanal fisheries throughout the world, little is known about its life history, ecology and vulnerability. We used stylet increment analysis to age a wild O. cyanea population for the first time and gonad histology to examine their reproductive characteristics. O. cyanea conforms to many cephalopod life history generalisations having rapid, non-asymptotic growth, a short life-span and high levels of mortality. Males were found to mature at much younger ages and sizes than females with reproductive activity concentrated in the spring and summer months. The female dominated sex-ratios in association with female brooding behaviours also suggest that larger conspicuous females may be more prone to capture and suggests that this intertidal octopus population has the potential to be negatively impacted in an unregulated fishery. Size at age and maturity comparisons between our temperate bordering population and lower latitude Tanzanian and Hawaiian populations indicated stark differences in growth rates that correlate with water temperatures. The variability in life history traits between global populations suggests that management of O. cyanea populations should be tailored to each unique set of life history characteristics and that stylet increment analysis may provide the integrity needed to accurately assess this.
Habitat Associations of Juvenile Fish at Ningaloo Reef, Western Australia: The Importance of Coral and Algae
Shaun K. Wilson,Martial Depczynski,Rebecca Fisher,Thomas H. Holmes,Rebecca A. O'Leary,Paul Tinkler
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0015185
Abstract: Habitat specificity plays a pivotal role in forming community patterns in coral reef fishes, yet considerable uncertainty remains as to the extent of this selectivity, particularly among newly settled recruits. Here we quantified habitat specificity of juvenile coral reef fish at three ecological levels; algal meadows vs. coral reefs, live vs. dead coral and among different coral morphologies. In total, 6979 individuals from 11 families and 56 species were censused along Ningaloo Reef, Western Australia. Juvenile fishes exhibited divergence in habitat use and specialization among species and at all study scales. Despite the close proximity of coral reef and algal meadows (10's of metres) 25 species were unique to coral reef habitats, and seven to algal meadows. Of the seven unique to algal meadows, several species are known to occupy coral reef habitat as adults, suggesting possible ontogenetic shifts in habitat use. Selectivity between live and dead coral was found to be species-specific. In particular, juvenile scarids were found predominantly on the skeletons of dead coral whereas many damsel and butterfly fishes were closely associated with live coral habitat. Among the coral dependent species, coral morphology played a key role in juvenile distribution. Corymbose corals supported a disproportionate number of coral species and individuals relative to their availability, whereas less complex shapes (i.e. massive & encrusting) were rarely used by juvenile fish. Habitat specialisation by juvenile species of ecological and fisheries importance, for a variety of habitat types, argues strongly for the careful conservation and management of multiple habitat types within marine parks, and indicates that the current emphasis on planning conservation using representative habitat areas is warranted. Furthermore, the close association of many juvenile fish with corals susceptible to climate change related disturbances suggests that identifying and protecting reefs resilient to this should be a conservation priority.
Modeling the Impact of Cell Type and Substrate Stiffness on Cell Traction  [PDF]
Srikanth Raghavan, Aravind R. Rammohan, Martial Hervy
Open Journal of Biophysics (OJBIPHY) , 2013, DOI: 10.4236/ojbiphy.2013.34028

We propose a mathematical model to suggest a unified explanation behind the observation that some cell types tend to spread more efficiently on stiff substrates and are able to adapt their internal stiffness to the external stiffness. Our model also offers an explanation regarding the dependence of cell spreading on cell type. We show that our model for stiffness adaptation is in good agreement with experimental data. We also apply our model to calculate the energy of traction on bulk substrates as well as thin coatings, thereby extracting estimates of critical coating thickness as a function of cell type and coating bulk modulus.

Study of Fourier-Based Velocimetry  [PDF]
Jean Martial Mari
Open Journal of Acoustics (OJA) , 2013, DOI: 10.4236/oja.2013.33A005

Standard phase-domain pulsed Doppler techniques used in Colour Flow Mapping such as spectral Doppler or autocorrelation are monochromatic, focused on the analysis of the centre transmit frequency. As such all the algorithms using those approaches are limited: in terms of spatial Doppler resolution because of the long pulses typically used for transmission, in terms of frame rate because of the necessity to perform many Doppler lines repetitions and additional B-mode imaging transmissions, and in terms of accuracy which depends on the stability of the Doppler signal at the frequency considered. A velocimetry technique is presented which estimates the shifts between successive Doppler line segments using the phase information provided by the Fourier transform. Such an approach allows extraction of more information from the backscattered signal through the averaging of results from multiple frequencies inside the bandwidth, as well as the transmission of wide band-high resolution-pulses. The technique is tested on Doppler signals acquired with a research scanner in a straight latex pipe perfused with water and cellulose scatterers, and on an ultrasound contrast agent solution. The results are compared with the velocity estimates provided by standard spectral Doppler and autocorrelation methods. Results show that the proposed technique performs better than both other approaches, especially when few Doppler lines are processed. The technique is also shown to be compatible with contrast Doppler imaging. The proposed approach enables high frame rate, high resolution Doppler.

Dynamic Stability of Coral Reefs on the West Australian Coast
Conrad W. Speed, Russ C. Babcock, Kevin P. Bancroft, Lynnath E. Beckley, Lynda M. Bellchambers, Martial Depczynski, Stuart N. Field, Kim J. Friedman, James P. Gilmour, Jean-Paul A. Hobbs, Halina T. Kobryn, James A. Y. Moore, Christopher D. Nutt, George Shedrawi, Damian P. Thomson, Shaun K. Wilson
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0069863
Abstract: Monitoring changes in coral cover and composition through space and time can provide insights to reef health and assist the focus of management and conservation efforts. We used a meta-analytical approach to assess coral cover data across latitudes 10–35°S along the west Australian coast, including 25 years of data from the Ningaloo region. Current estimates of coral cover ranged between 3 and 44% in coral habitats. Coral communities in the northern regions were dominated by corals from the families Acroporidae and Poritidae, which became less common at higher latitudes. At Ningaloo Reef coral cover has remained relatively stable through time (~28%), although north-eastern and southern areas have experienced significant declines in overall cover. These declines are likely related to periodic disturbances such as cyclones and thermal anomalies, which were particularly noticeable around 1998/1999 and 2010/2011. Linear mixed effects models (LME) suggest latitude explains 10% of the deviance in coral cover through time at Ningaloo. Acroporidae has decreased in abundance relative to other common families at Ningaloo in the south, which might be related to persistence of more thermally and mechanically tolerant families. We identify regions where quantitative time-series data on coral cover and composition are lacking, particularly in north-western Australia. Standardising routine monitoring methods used by management and research agencies at these, and other locations, would allow a more robust assessment of coral condition and a better basis for conservation of coral reefs.
Beyond 50. challenges at work for older nurses and allied health workers in rural Australia: a thematic analysis of focus group discussions
Lyn J Fragar, Julie C Depczynski
BMC Health Services Research , 2011, DOI: 10.1186/1472-6963-11-42
Abstract: Nurses and allied health workers aged 50 years and over were invited to attend one of six local workshops held in the Hunter New England region of NSW, Australia. This qualitative action research project used a focus group methodology and thematic content analysis to identify and interpret issues arising from workshop discussions.Eighty older health workers from a range of disciplines attended the workshops. Tasks and aspects of work that have become more difficult for older health workers in hospital settings, include reading labels and administering medications; hearing patients and colleagues; manual handling; particular movements and postures; shift work; delivery of babies; patient exercises and suturing. In community settings, difficulties relate to vehicle use and home visiting. Significant issues across settings include ongoing education, work with computers and general fatigue. Wider personal challenges include coping with change, balancing work-life commitments, dealing with attachments and meeting goals and expectations. Work and age-related factors that exacerbate difficulties include vision and hearing deficits, increasing tiredness, more complex professional roles and a sense of not being valued in the context of greater perceived workload.Older health workers are managing a range of issues, on top of the general challenges of rural practice. Personal health, wellbeing and other realms of life appear to take on increasing importance for older health workers when faced with increasing difficulties at work. Solutions need to address difficulties at personal, workplace and system wide levels.The rural health workforce in Australia is ageing and is older than the urban health workforce [1-4]. In 2005, the average age of nurses in outer regional areas of Australia was 46.0 years, compared to 44.6 years in metropolitan areas [2]. Although younger than the nursing profession, rural allied health workers also tend to be older than their city counterparts [3].
Lógica, arquitet nica e estruturas constitutivas dos sistemas filosóficos
Martial Gueroult
Trans/Form/A??o , 2007, DOI: 10.1590/s0101-31732007000100016
The laser, from yesterday (1960) to tomorrow
Ducloy Martial
Europhysics News , 2011, DOI: 10.1051/epn/2011102
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