Life Histories in an Epifaunal Community: Coupling of Adult and Larval Processes

Marine invertebrates growing epifaunally on red mangrove (Rhizophora mangle) prop roots in the Indian River, Florida, USA, were studied in a small mangrove island (Jim Island) through which a number of channels had been cut. Roots hanging down into the water supported diverse epifaunal communities including sponges, oysters, barnacles, bryozoans, and ascidians. To determine what factors control species\u27 population dynamics and contribute to the high degree of spatial heterogeneity characteristic of communities in this unique habitat, two hypotheses were tested: (1) Distributions of species on the roots are controlled by differential growth and mortality due to physical features; and (2) Recruitment, as influenced by larval supply, structures the community. Four channels of the island were chosen for comparison and experimentation. Distributions and abundances of epifauna in the channels were determined and physical parameters (i.e., temperature, pH, salinity, flow, turbidity) were measured over a 13-mo period. Adult and early juvenile organisms were transplanted among channels and growth and survival were monitored. Patterns of water flow in the island were studied, and plankton samples were taken to determine how larval supply varied among channels in different parts of the island. General patterns of recruitment were measured for 9 mo and patterns were compared to adult distributions. Epifaunal cover differed among the study channels, with dramatic differences in abundance and species diversity. Except for flow, physical factors did not differ significantly among channels. Flow rate, per se, was not responsible for disjunct distributions since neither adult nor juvenile survival (processes expected to be most affected by flow) differed among channels. Plankton samples and recruitment measurements revealed that the importance of larval supply depended on the life history of the individual species. Those producing short-lived lecithotrophic larvae showed patchy distributions that were strongly affected by the location of source populations and prevailing patterns of water flow. Species with long-lived planktotrophic larvae were more evenly distributed and post-settlement processes played a more important role in their population dynamics. On large temporal or spatial scales, the effects of physical factors on juvenile and adult organisms are probably quite important in controlling epifaunal distributions. However, in this study, the distributions of organisms on Rhizophora mangle root within Jim Island were best explained by differential larval input, with larval life history determining the strength of coupling between adult populations, larval supply, and patterns of recruitment

Optimization methods applied to the aerodynamic design of helicopter rotor blades

Described is a formal optimization procedure for helicopter rotor blade design which minimizes hover horsepower while assuring satisfactory forward flight performance. The approach is to couple hover and forward flight analysis programs with a general-purpose optimization procedure. The resulting optimization system provides a systematic evaluation of the rotor blade design variables and their interaction, thus reducing the time and cost of designing advanced rotor blades. The paper discusses the basis for and details of the overall procedure, describes the generation of advanced blade designs for representative Army helicopters, and compares design and design effort with those from the conventional approach which is based on parametric studies and extensive cross-plots

The surgical aspects of water and salt metabolism

I. Water and Salt metabolism has been discussed both in their theoretical and in their practical aspects.2. A series of experiments was conducted on normal human subjects to prove or disprove certain conceptions of salt metabolism.3. In general these conceptions were substantiated and, arising from this work the clinical applications are as follows:A. To diminish the mortality and morbidity from operations both water and electrolytes must be given in adequate amounts to restore or maintain normality. Two main types of problem therefore, may confront the surgeon.I. The case which comes under his care with depleted fluids and electrolytes and rules have been given for the restoration of both to normal.2. The case which in hospital after operation loses electrolytes and fluids from vomiting, fistulae, etc. Such a case can be maintained in fluid balance by the application of the rules of water balance enunciated by W. G. Maddock and detailed in this paper. The electrolyte balance can also be maintained by the administration of a volume of 0.9% sodium chloride solution equal to the volume of the abnormal fluid losses (vomitus, drainage from fistulae etc.) without endangering the patient by overloading him with sodium chloride.B. The following table shows the degree of accuracy which results from the application of these rules, and I feel that, although much further work is needed fully to substantiate our claims, the clinical administration of sodium chloride has been placed on a sound basis

Some aspects of the pre and post operative care of surgical patients

The first forty years of the twentieth century have seen greater advances in the science and art of surgery than the whole of preceding time. But, as the field of surgical endeavour has widened, new problems have arisen. Operations are now carried out upon patients so reduced by their disease that formerly interference would not have even have been considered. The outcome of such enterprises depends upon meticulous care in the pre and post-operative treatment, not the least important aspect of which is the maintenance of normal water and electrolyte metabolism. In this connection it is interesting to recall that as long ago as 1831 Dr. W. B. O'Shaughnessy of Newcastle upon Tyne recognised the essentials of water and electrolyte depletion and also outlined treatment. In a brief letter to the London Medical Gazette he summarised the changes which occur in the blood of patients suffering from cholera. He stated that:1. "The blood drawn in the worse cases of cholera is unchanged in its anatomical or globular structure."2. It has lost a large proportion of its water, 1000 parts of cholera serum having but the average of 850 parts of water."3. "It has lost also a great proportion of its neutral saline ingredients."4. "Of the free alkali contained in healthy serum, not a particle is present in some cholera cases, and barely a trace in others."5. "Urea exists in the cases where suppression of urina has been a marked sympton."6. "All the salts deficient in the blood, especially the alkali or carbonate of soda, are present in large quantities in the peculiar white dejected matters."From the early papers and the very numerous investigations which have since been carried out, it has become obvious that loss of water and sodium chloride from the body so alters "the innumerable and interrelated chemical reactions that together accomplish what we call metabolism that life itself may thereby be seriously endangered. Therefore rational fluid therapy must be directed not to restoring the normal body content of any particular component of the body fluids (which indeed is separately impossible), but to the restoration and maintenance of the normal volume, composition, and distribution of the body fluids as a whole, so that metabolism may proceed under the most favourable of circumstances. It is the purpose of this paper to discuss the metabolism of the body fluids, the practical applications of fluid therapy in surgical patients, and to make some contribution to our knowledge of the therapeutics of sodium chloride

Instabilities in neutrino-plasma density waves

One examines the interaction and possible resonances between supernova neutrinos and electron plasma waves. The neutrino phase space distribution and its boundary regions are analyzed in detail. It is shown that the boundary regions are too wide to produce non-linear resonant effects. The growth or damping rates induced by neutrinos are always proportional to the neutrino flux and $G_{{\rm F}}^{2}$.Comment: 9 pages, a few words modified to match PRD publicatio