396 research outputs found
In the darkness of the polar night, scallops keep on a steady rhythm
Published version. Source at http://doi.org/10.1038/srep32435.
License CC BY 4.0.Although the prevailing paradigm has held that the polar night is a period of biological quiescence, recent studies have detected noticeable activity levels in marine organisms. In this study, we investigated the circadian rhythm of the scallop Chlamys islandica by continuously recording the animal’s behaviour over 3 years in the Arctic (Svalbard). Our results showed that a circadian rhythm persists throughout the polar night and lasts for at least 4 months. Based on observations across three polar nights, we showed that the robustness and synchronicity of the rhythm depends on the angle of the sun below the horizon. The weakest rhythm occurred at the onset of the polar night during the nautical twilight. Surprisingly, the circadian behaviour began to recover during the darkest part of the polar night. Because active rhythms optimize the fitness of an organism, our study brings out that the scallops C. islandica remain active even during the polar night
Monitoring biological rhythms through the dynamic model identification of an oyster population
International audienceThe measurements of valve activity in a population of bivalves under natural environmental conditions (16 oysters in the Bay of Arcachon, France) are used for a physiological model identification. A nonlinear auto-regressive exogenous (NARX) model is designed and tested. The method to design the model has two parts. 1) Structure of the model: The model takes into account the influence of environmental conditions using measurements of the sunlight intensity, the moonlight, tide levels, precipitation and water salinity levels. A possible influence of the internal circadian/circatidal clocks is also analyzed. 2) Least square calculation of the model parameters. Through this study, it is demonstrated that the developed dynamical model of the oyster valve movement can be used for estimating normal physiological rhythms of permanently immersed oysters and can be considered for detecting perturbations of these rhythms due to changes in the water quality, i.e. for ecological monitoring
A Fault Detection Method for Automatic Detection of Spawning in Oysters
Using measurements of valve activity (i.e., the distance between the two valves) in populations of bivalves under natural environmental conditions (16 oysters in the Bay of Arcachon, France, in 2007, 2013, and 2014), an algorithm for an automatic detection of the spawning period of oysters is proposed in this brief. Spawning observations are important in aquaculture and biological studies, and until now, such a detection is done through visual analysis by an expert. The algorithm is based on the fault detection approach and it works through the estimation of velocity of valve movement activity, which can be obtained by calculating the time derivative of the valve distance. A summarized description of the methods used for the derivative estimation is provided, followed by the associated signal processing and decision-making algorithm to determine spawning from the velocity signal. A protection from false spawning detection is also considered by analyzing the simultaneity in spawning. Through this study, it is shown that spawning in a population of oysters living in their natural habitat (i.e., in the sea) can be automatically detected without any human expertise, saving time and resources. The fault detection method presented in this brief can also be used to detect complex oscillatory behavior which is of interest to control engineering community.<br/
Evidence of separate influence of moon and sun on light synchronization of mussel's daily rhythm during the polar night
Marine organisms living at high latitudes are faced with a light climate that undergoes drastic annual changes, especially during the polar night (PN) when the sun remains below the horizon for months. This raises the question of a possible synchronization and entrainment of biological rhythms under the governance of light at very low intensities. We analyzed the rhythms of the mussel Mytilus sp. during PN. We show that (1) mussels expressed a rhythmic behavior during PN; (2) a monthly moonlight rhythm was expressed; (3) a daily rhythm was expressed and influenced by both sunlight and moonlight; and (4) depending on the different times of PN and moon cycle characteristics, we were able to discriminate whether the moon or the sun synchronize the daily rhythm. Our findings fuel the idea that the capability of moonlight to synchronize daily rhythms when sunlight is not sufficient would be a crucial advantage during PN.publishedVersio
Temperature dependence of the electrochemical behavior of the 690 Ni-base alloy between 25 and 325 °C
International audienceThe electrochemical behavior and the chemical composition of passive films formed on the Alloy 690 at room temperature in borate buffer solution (pH = 9.0) was studied with different techniques for two surface finishings. XPS and quantum yield measurements showed the presence of Ni and Cr oxides and hydroxides for passive films formed on both the as received and the mechanically polished one, whereas the presence of mixed spinel type Ni (1-x) Fe x Cr 2 O 4 was only observed on the as received material. Additionally, Electrochemical Impedance Spectroscopy (EIS) highlighted a higher corrosion resistance for the as received alloy in comparison with the mechanically polished alloy, which was linked to the chemical composition of the oxide film. Electrochemical measurements were performed before, during, and after oxidation of the Alloy 690 of Steam Generator (SG) tube of Pressurized Water Reactor (PWR) at high temperature and high pressure in the simulated primary circuit of PWR. At high temperature, the interface becomes electrochemically active yielding the precipitation of the corrosion products which form a few tens of nm thick diffusion barrier for the released metal cations. This overlayer is built on the top of a few nm thick, Cr rich inner layer at the alloy/oxide interface which was found to behave similarly to that initially formed at ambient temperature. It is concluded that high temperature oxidation in the static condition of an autoclave at 325°C does not promote a better passivation state than the one already existing initially
Recommended isolated-line profile for representing high-resolution spectroscopic transitions (IUPAC Technical Report)
The report of an IUPAC Task Group, formed in 2011 on "Intensities and line
shapes in high-resolution spectra of water isotopologues from experiment and
theory" (Project No. 2011-022-2-100), on line profiles of isolated
high-resolution rotational-vibrational transitions perturbed by neutral
gas-phase molecules is presented. The well-documented inadequacies of the Voigt
profile (VP), used almost universally by databases and radiative-transfer
codes, to represent pressure effects and Doppler broadening in isolated
vibrational-rotational and pure rotational transitions of the water molecule
have resulted in the development of a variety of alternative line-profile
models. These models capture more of the physics of the influence of pressure
on line shapes but, in general, at the price of greater complexity. The Task
Group recommends that the partially Correlated quadratic-Speed-Dependent
Hard-Collision profile should be adopted as the appropriate model for
high-resolution spectroscopy. For simplicity this should be called the
Hartmann--Tran profile (HTP). The HTP is sophisticated enough to capture the
various collisional contributions to the isolated line shape, can be computed
in a straightforward and rapid manner, and reduces to simpler profiles,
including the Voigt profile, under certain simplifying assumptions.Comment: Accepted for publication in Pure and Applied Chemistr
Sex recognition by odour and variation in the uropygial gland secretion in starlings
1. Although a growing body of evidence supports that olfaction based on chemical compounds emitted by birds may play a role in individual recognition, the possible role of chemical cues in sexual selection of birds has been only preliminarily studied.2. We investigated for the first time whether a passerine bird, the spotless starling Sturnus unicolor, was able to discriminate the sex of conspecifics by using olfactory cues and whether the size and secretion composition of the uropygial gland convey information on sex, age and reproductive status in this species.3. We performed a blind choice experiment during mating, and we found that starlings were able to discriminate the sex of conspecifics by using chemical cues alone. Both male and female starlings preferred male scents. Furthermore, the analysis of the chemical composition of the uropygial gland secretion by using gas chromatography–mass spectrometry (GC–MS) revealed differences between sexes, ages and reproductive status.4. In conclusion, our study reveals for first time that a passerine species can discriminate the sex of conspecifics by relying on chemical cues and suggests that the uropygial gland secretion may potentially function as a chemical signal used in mate choice and/or intrasexual competition in this species.This research was funded by the Spanish Ministry of Education and Science ⁄ FEDER (CGL2008-00718) and PIE 200930I029 to J. M. Avilés and D. Parejo.The study was conducted under licence of the Junta de Andalucía GC–MS analyses were performed by Dr. Rafael Núñez at the Scientific Instrumentation Service (EEZ, CSIC) (Granada, Spain).Peer reviewe
Transcriptomic evidence for modulation of host inflammatory responses during febrile Plasmodium falciparum malaria
Identifying molecular predictors and mechanisms of malaria disease is important for understanding how Plasmodium falciparum malaria is controlled. Transcriptomic studies in humans have so far been limited to retrospective analysis of blood samples from clinical cases. In this prospective, proof-of-principle study, we compared whole-blood RNA-seq profiles at pre-and post-infection time points from Malian adults who were either asymptomatic (n = 5) or febrile (n = 3) during their first seasonal PCR-positive P. falciparum infection with those from malaria-naïve Dutch adults after a single controlled human malaria infection (n = 5). Our data show a graded activation of pathways downstream of pro-inflammatory cytokines, with the highest activation in malaria-naïve Dutch individuals and significantly reduced activation in malaria-experienced Malians. Newly febrile and asymptomatic infections in Malians were statistically indistinguishable except for genes activated by pro-inflammatory cytokines. The combined data provide a molecular basis for the development of a pyrogenic threshold as individuals acquire immunity to clinical malaria
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