At mid-shore levels on rocky shores in New South Wales, grazing gastropods are the dominant species in sheltered areas. Where wave-exposure is great, barnacles occupy most of the space. At intermediate levels of waveexposure, there are mixtures of grazing gastropods and barnacles, and the patterns of occupancy of space, and structure of the community change from time to time. The major species found in these areas are the coronuloid barnacle Tesseropora rosea, the patellid limpet Cellana tramoserica, the smaller acmaeid limpet, Patelloida latistrigata, which is mostly confined amongst barnacles, and the predatory whelk Morula marginalba. The roles of each of these species in determining the structure and persistence of intertidal communities were investigated by experimental manipulations of the densities of each of these organisms. In most experiments, a range of densities of limpets and barnacles was used, rather than the simple removal of all of one species.Recruitment of Cellana was negatively associated with increasing density of adult limpets, and with increasing density of barnacles. Growth and survival of juvenile Cellana were decreased by increasing densities of barnacles, probably because barnacles occupied space, preventing limpets from grazing. Morula had no effect on recruitment or survival of juvenile Cellana. Recruitment of juvenile Patelloida was not affected by different densities of barnacles, but survival to adult sizes was poor in areas where whelks are active. In areas where whelks were removed, Patelloida showed increased survivorship with increased cover of barnacles, probably because Patelloida amongst barnacles found refuge from the superior competitive effects of Cellana.The settlement and subsequent survival of Tesseropora were affected in complex ways by the activities of Cellana. At great densities, Cellana can have deleterious effects on newly-settled barnacles, probably by crushing them whilst grazing. In some areas, and at some densities, however, limpets can have beneficial effects on the recruitment and/or survival of Tesseropora. The limpets graze the juvenile stages of growth of foliose macroalgae, preventing them from growing up to pre-empt the rock-surface (thus preventing settlement of barnacles) or to smother alreadysettled barnacles. The effect of limpets on the recruitment and survival of barnacles in any area is a function of the densities of limpets and barnacles, and the height on the shore and local weather (the latter factors influence the rates of growth of algae).Increased cover of the rock-surface by adult barnacles caused reductions in the densities of Cellana. Limpets migrated away from areas of great cover of barnacles, and, if confined in such areas, starved and lost weight. The dispersion, as well as the density of the barnacles was important in determining the effects of barnacle cover. Where barnacles occupied half the space, but were scattered, leaving only small patches of bare rock, they had the same deleterious effects on Cellana as in areas where they ...
Patients are increasingly seeking information about physicians online. Nearly 60% report that online reviews are important when choosing a physician. 1 Because publicly reported quality data are not reported at the physician level, patients must consult physician-rating websites to find such reviews. 2 The purpose of this cross-sectional study was to describe the structure of commercial physicianrating websites and the quantity of physician reviews on these sites. Methods |During September 2016, we searched Google for websites that allowed patients to review physicians in the United States, using search terms such as rate my doctor. We included active sites that were written in English, available to the public, allowed patients to leave reviews, did not require a subscription, and allowed searching by physician name. We excluded websites that were affiliated with an insurance company or health system or were limited to a single specialty. We cross-referenced search results against a published list, 3 added any websites that met inclusion criteria, and recorded website characteristics. We then used publicly available lists of registered and active physicians to identify a random sample of 600 physicians from 3 metropolitan areas (Boston, Massachusetts; Portland, Oregon; and Dallas, Texas). We searched each website for reviews and calculated mean and median number of reviews per physician per site using SAS (SAS Institute), version 9.3.
The Petawatt laser at LLNL has opened a new regime of laser-matter interactions in which the quiver motion of plasma electrons is fully relativistic with energies extending well above the threshold for nuclear processes. In addition to -few MeV ponderomotive electrons produced in ultra-intense laser-solid interactions, we have found a high energy component of electrons extending to -100 MeV apparently from relativistic self-focusing and plasma acceleration in the underdense pre-formed plasma. The generation of hard bremsstrahlung, photo-nuclear reactions, and preliminary evidence for positron-electron pair production will be discussed.
Concentrations of trace elements in the sagittal otoliths of pink snapper (Chrysophrys auratus) from seven locations along the coast of Western Australia were measured by inductively coupled plasma atomic emission spectrometry (ICP-AES). Canonical variate (discriminant) analyses of the concentrations of eight elements (Na, Mg, Si, P, S, K, Fe, and Sr) from all fish when corrected for fish length showed the pattern of concentrations to be specific to the location of capture of the fish. Trace elements are likely to be irreversibly deposited in the sagittae during growth and should provide an integrated environmental history of each fish. Differences in elemental composition may thus be useful for identifying nonmixing groups of fish that may be regarded as separate stocks for some fisheries management purposes.
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