A comparison of zooplankton production estimates obtained from three commonly used methods and a computer simulation program

We constructed a simple non–steady‐state model of trophic cycling relationships in the California Current Ecosystem and tested its predictions of mesozooplankton fecal‐pellet export against vertical carbon‐flux measurements by the 234Th method taken during Lagrangian experiments. To assess trophic relationships, we simultaneously measured 14C‐primary production and chlorophyll‐based rate estimates of phytoplankton growth, microzooplankton grazing, mesozooplankton grazing, and net phytoplankton growth. Study locations ranged from coastal upwelling to offshore oligotrophic conditions. E‐ratios (carbon export : 14C‐primary production) predicted by the model ranged from 0.08 to 0.14, in good agreement with both the magnitude and the variability found in contemporaneous measurements of 234Th export and C : 234Th‐ratios of sinking particles. E‐ratios were strongly decoupled from new production estimates. The lowest measured and predicted e‐ratios were associated with higher nutrient chlorophyll parcels with net accumulating phytoplankton in the inshore region. For our study sites, variability in export efficiency was determined by the local net balance of growth and grazing and the relative strengths of grazing pathways to microzooplankton and mesozooplankton. Despite very different plankton assemblages studied, the consistently good agreement between independently measured production‐grazing processes and biogeochemical rates suggest that zooplankton are the major drivers of vertical carbon‐flux in this system during springtime.

Estimates of production and respiration rates by a field community of ciliates were made in an experimental ricefield located in the province of Reggio Emilia (Northern Italy) from June to September 13, 1983. Particular attention was given to ciliate communities inhabiting both the water column and the sediment. Production in the sediment was higher than in the water column during the first period of rice cultivation (June–July); in the second period (August–September) production was higher in the water column. A similar trend was recorded for respiration rates. During the entire period, production was estimated at 471 KJ m-2, while energy losses due to respiration accounted for 178 KJ m-2. The net production efficiency (K2) of the total ciliate community was 72.5%. Results obtained are discussed and compared with published data on ciliated Protozoa in other ecosystems.

The F-layer at sunrise near the magnetic equator

Determination of the rate of production and dissolution of biosilica in marine waters by thermal ionisation mass spectrometry

Why use computer simulation as an educational tool? Why is computer simulation based on mathematical models? What kinds of computer simulations are there? What is the difference between computer simulation and modeling? What is the difference between a model and a program? What are some advantages and disadvantages of computer simulation programs? What is the difference between learning through discovery and various kinds of coached learning? In which five ways can computer simulation programs be used?

In shallow coastal systems dominated by vertical mixing, phytoplankton cells experience light variations due to vertical excursions. Therefore, it would be unusual for phytoplankton to experience constant irradiance during 4 or 24 h, the standard incubation times used to estimate daily primary production rates. The aim of this work was to determine conditions under which bias could occur in long-term simulated in situ incubations (SIS). Values of primary production estimated from 4 and 24 h SIS incubations have been compared with estimates of primary production based on photosynthetic parameters, which were determined on short incubation times (40 min). Sampling was conducted under different conditions of vertical mixing. It appears that daily primary production rates computed from 24 h incubation times are the lowest at each sampling station, whereas differences between daily production rates estimated from 4 h and 40 min incubation times depend on the sampling stations. Vertical mixing and available light intensity could control differences between the computed daily production rates on 4 h and 40 min incubation times. In fact, under conditions of non-limiting light intensity for photosynthesis, photoadaptation processes could occur in long-term SIS incubations, which do not take into account vertical mixing, and enhance primary production estimates.

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This work estimates probit and tobit models of the adoption of recombinant bovine somatotropin (rbST) on Connecticut dairy farms and then endogenizes that adoption in estimates of milk production and farm profit rates. The work improves on the current literature by allowing the rbST decision to be both continuous and contingent on other technology adoption decisions. The results show that larger farms, with more productivity technologies, and with younger, more educated farmers, are more likely to adopt rbST. While rbST is shown to significantly increase milk production, there is no evidence that it increases profits on a per cow basis.

Developability assessment of clinical drug products with maximum absorbable doses

Computer simulation techniques have become an essential tool for scientists and engineers in various areas including food processing. Cake baking is a very complex process that brings about a series of physical, chemical and biochemical changes within a product that are influenced by conditions in ovens. The objective of this study was to develop a computer simulation program for cake baking in a continuous industrial oven, which can be used to predict the transient and spatial temperature and moisture distributions inside the product, and the dynamic volume expansion of cakes under continuous oven conditions observed in multi-zones industrial ovens. A finite difference method was implemented to solve the thermal and mass transfer differential governing equations. The Kelvin model was used to describe the cake volume expansion considering a balance of driving forces and resistances. Variable zone temperature and moisture profiles and variable thermo-physical properties as a function of temperature and moisture were used. A set of experimental results of cake temperature and moisture under different processing conditions was used to compare with those obtained from various computer simulations. Statistical results showed that correlation coefficients for the relationship between predicted and experimental results were R2=0.96 for temperature and R2=0.92 for moisture. Several computer simulations were further used for a sensitivity analysis of main processing conditions on the development of the final cake volume. It can be expected that this computer simulation program will become a useful tool for the cake baking industry to search for optimal processing conditions to improve cake quality while saving energy.

Analytical theory of low and medium energy ion reflection by target surface atoms during sputtering

Program for computer simulation on photoproduction of mesons decaying into two photons

India is one of the very few developing countries which have a relatively long history of population censuses. The first census was taken in 1872, the second in 1881 and since then there has been a census every ten years, the latest in 1971. Yet the registration of births and deaths in India, even at the present time, is too inadequate to be of much help in estimating fertility and mortality conditions in the country. From time to time Indian census actuaries have indirectly constructed life tables by comparing one census age distribution with the preceding one. Official life tables are available for all the decades from 1872-1881 to 1951-1961, except for 1911-1921 and 1931-1941. Kingsley Davis(1) filled in the gap by constructing life tables for the latter two decades. He also estimated the birth and death rates ofIndia for the decades from 1881-1891 to 1931-1941. Estimates of these rates for the following two decades, 1941-1951 and 1951-1961, were made by Indian census actuaries. The birth rates of Davis and the Indian actuaries were obtained basically by the reverse survival method from the age distribution and the computed life table of the population. Coale and Hoover(2), however, estimated the birth and death rates and the life table of the Indian population in 1951 by applying stable population theory. The most recent estimates of the birth rate and death rate for 1963-1964 are based on the results of the National Sample Survey. All these estimates are presented in summary form in Table 1.

We reexamine the planetary nebulae in the greater solar neighborhood and find the local number density to be about 80 kpc/sup -3/ and a local birth (and death) rate of some 4--6 x 10/sup -3/ kpc/sup -3/ yr/sup -1/. For the corresponding whole-galaxy figures we adopt tentatively a total planetary population of about 38,000 +- 12,000 and a production rate of 2 or 3 per year. A simplified model of galactic star formation predicts that the local death rate of stars with main-sequence masses between 1 and 5 M/sub sun/ is 2--3 x 10/sup -3/ kpc/sup -3/ yr/sup -1/; and Weidemann's statistics and cooling times for white dwarfs yield a comparable production rate for those objects of 2--5 x 10/sup -3/ kpc/sup -3/ yr/sup -1/. These several local rates, derived from entirely different sets of data, are all comparable and therefore reinforce the widely held idea that planetary nebulae are cosmically evanescent episodes between the main-sequence and white-dwarf stages in the evolution of all or most modestly massive stars.The model of star formation also predicts that the local death rate of stars with main-sequence masses greater than 5 M/sub sun/ is a few times 10/sup -4/ kpc/sup -3/ yr/sup -1/,more » in rough agreement with current estimates of the local production rate of supernovae and of pulsars. We suggest that neutron stars of all ages up to the age of the Galaxy may account for a modest fraction of the local mass density required by the Oort limit.We also explore the planetary nebulae far from the galactic plane and suggest that there are no more than about 100 such systems in the halo of the Galaxy. With the unproved assumption that halo planetaries are physically comparable to those in the disk, we are able to calculate an approximate upper limit to the mass of the halo of 2--5 x 10/sup 9/ M/sub sun/, or 1--3 percent of the conventionally accepted mass of the Galaxy. (AIP)« less

The population dynamics and production of Cyclops vicious (Uljanin) in a shallow eutrophic reservoir were studied over a period of two years. Breeding continued throughout the year, but variations in the rate of egg production gave rise to a succession of generations that could be followed from stage to stage in development. A proportion of stage IV copepodites left the open water in midsummer and remained in diapause until the following spring. Seasonal fluctuations in the finite birth rate were related to changes in the egg stock, mean brood size and the proportion of egg bearing females. Egg development times were determined in culture, and estimates of copepodite instar duration obtained from field data. Production estimates were obtained from the population curves by calculating the number of animals passing through successive stages in each generation. Relationships between population and environmental variables were examined by the method of principal component analysis. There was a marked positive correlation between the C. vicious birth rate and the birth rate of Daphnia hyalina, the only other abundant species in the reservoir.