The first INTEGRAL-OMC catalogue of optically variable sources

The Optical Monitoring Camera (OMC) onboard INTEGRAL provides photometry in the Johnson V-band. With an aperture of 50 mm and a field of view of 5deg x 5deg, OMC is able to detect optical sources brighter than V~18, from a previously selected list of potential targets of interest. After more than nine years of observations, the OMC database contains light curves for more than 70000 sources (with more than 50 photometric points each). The objectives of this work have been to characterize the potential variability of the objects monitored by OMC, to identify periodic sources and to compute their periods, taking advantage of the stability and long monitoring time of the OMC. To detect potential variability, we have performed a chi-squared test, finding 5263 variable sources out of an initial sample of 6071 objects with good photometric quality and more than 300 data points each. We have studied the periodicity of these sources using a method based on the phase dispersion minimization technique, optimized to handle light curves with very different shapes.In this first catalogue of variable sources observed by OMC, we provide for each object the median of the visual magnitude, the magnitude at maximum and minimum brightness in the light curve during the window of observations, the period, when found, as well as the complete intrinsic and period-folded light curves, together with some additional ancillary data.Comment: Accepted by Astronomy & Astrophysics; 13 pages, 16 figures. Figures' resolution has been degraded to fit astro-ph constraint

Parasites from freshwater fishes and Mollusca; a new species of Capillaria from the minnow and five new Cercariae from Limnaea

Since the discovery of sporocysts and rediae "by Steenstrup in 1842, the study of the life histories of different Trematodes has received much attention by investigators, for instance Wagener in 1857, leuckart in 1882, Thomas in 1883, Heckert in 1889, Greutzberg in 1890 and Looss in recent times. It was from the observations of these workers that the life cycle of Trematodes was put on a firm basis. But no real importance was attached to the study of miracidia, sporocysts, rediaeand cercariae until after the classical work of Thomas in 1883, which resulted in a thorough explanation of the life history of the liver fluke and its transmission from sheep to sheep.Since 1883 numerous investigations have been carried out from the economical and medical point of view, and the bulk of the contributions to the knowledge of cerca.riae consists of the results of observations and experiments on the cercariee of the Trematodes infecting man and the domestic animals Particular attention was paid to the different intermediate hosts and the conditions under which they are capable of causing the infection of the definitive hosts.A serious study of the organisation of cercariae was long neglected and in spite of the numerous cercariae described by many investigators, it is impossible to identify many of the species correctly. It was only after the study of the cercariae of the Schistosomidae infecting man that the study of the morphology and histology of other cercariae was adequately undertaken, and authors began to attach importance to features of the internal organisation, which may throw light on the structure of the adult. The systems which have been carefully studied are the alimentary tract, the excretory and genital systems, and specific differences were observed even among cercariae closely resembling one another. Certain glands in the body have also been observed, and have proved in many cases to play an important part in the process of infection of the definitive host.If the external and internal structures of a cercaria be considered, we may divide the characters into two sets:(A) 'Those structures such as the suckers, the alimentary tract, the excretorysystem, the genital system, and some parenchymatous cells which form the basis or are the miniatures of the corresponding adult structures,(B) Those structures such as tails, spines, processes, stylets, eye spots, salivary glands, cystogenous cells and parenchymatous cells,which are purely larval structures and are not carried over to the adult. The structures belonging to the former group are relatively well known but in the case of the larval structures there is much yet to be explained.What are termed salivary glands may have the same structure but different functions in different cases. The cystogenous cells are distinguishable from parenchymatous cells by possessing larger nuclei poor in chromatin, and cytoplasm which may contain obvious granules or may be faintly granular, but their function is not always demonstrable. Lastly the parenchymatous cells are indistinguishable from other cells such as those surrounding the nerve ganglia, those under the cuticle, which have received the name of cuticular cells and from cells which are destined to give rise to other structures such as vitelline glands. Looss emphasized the fact that thesecells are at first indistinguishable cytologically and maintained that many of these mesodermal cells remain findifferentiated for a considerable time. There is also reason to believe that some cells in the parenchyma form the basis of other structures such as the excretory system, for the collecting ducts are not bounded by cellular walls, but are merely lumina among certain cells. Certain other parenchymatous cells both in the body and in the tail of some cerc&riae are more vacuolated and distended and their function appears to be that of buoyancy

New Measure of the Dissipation Region in Collisionless Magnetic Reconnection

A new measure to identify a small-scale dissipation region in collisionless magnetic reconnection is proposed. The energy transfer from the electromagnetic field to plasmas in the electron's rest frame is formulated as a Lorentz-invariant scalar quantity. The measure is tested by two-dimensional particle-in-cell simulations in typical configurations: symmetric and asymmetric reconnection, with and without the guide field. The innermost region surrounding the reconnection site is accurately located in all cases. We further discuss implications for nonideal MHD dissipation