A Numerical Model for Determining Integral Primary Production and its Application to Lake Michigan

1973 ◽  
Vol 30 (10) ◽  
pp. 1447-1468 ◽  
Author(s):  
Everett J. Fee
Keyword(s):  
Primary Production ◽  
Lake Michigan ◽  
Model Parameters ◽  
Time Interval ◽  
Actual Distribution ◽  
In Situ Experiments ◽  
Routine Basis ◽  
Computer Based ◽  
Large Water

A computer-based model for determining production by phytoplankton, integrated over depth and over an arbitrary time interval, is described. The solution incorporates light inhibition and uses the actual distribution of surface irradiance for the time interval of interest, since it is not possible to predict the detailed nature of cloudiness. Statistical procedures for estimating the model parameters from experimental data relating the rate of carbon uptake to irradiance are described. The model is applied to data collected from May 27, 1970 through February 3, 1971 from Lake Michigan.Integral primary production was bimodal at inshore and offshore stations with minimum production in midsummer and winter. There was great daily variability of integral production, due solely to variation of light. From this it is inferred that occasional in situ measurements would give a very poor knowledge of true seasonal trends.The model output was verified by performing two in situ experiments. The agreement was better than 95% on both dates. The model makes it possible to estimate integral primary production on a routine basis in large water bodies with well-mixed photic zones.

“Sintering” Models and In-Situ Experiments: Data Assimilation for Microstructure Prediction in SLS Additive Manufacturing of Nylon Components

MRS Advances ◽  
2020 ◽  
Vol 5 (29-30) ◽  
pp. 1593-1601
Author(s):  
W. Steven Rosenthal ◽  
Francesca C. Grogan ◽  
Yulan Li ◽  
Erin I. Barker ◽  
Josef F. Christ ◽  
...  
Keyword(s):  
Adaptive Sampling ◽  
Selective Laser Sintering ◽  
Phase Field Model ◽  
Estimation Algorithm ◽  
Model Parameters ◽  
Multiple Data ◽  
In Situ Experiments ◽  
Parameter Estimation Algorithm ◽  
Microstructure Prediction

ABSTRACTSelective laser sintering methods are workhorses for additively manufacturing polymer-based components. The ease of rapid prototyping also means it is easy to produce illicit components. It is necessary to have a data-calibrated in-situ physical model of the build process in order to predict expected and defective microstructure characteristics that inform component provenance. Toward this end, sintering models are calibrated and characteristics such as component defects are explored. This is accomplished by assimilating multiple data streams, imaging analysis, and computational model predictions in an adaptive Bayesian parameter estimation algorithm. From these data sources, along with a phase-field model, bulk porosity distributions are inferred. Model parameters are constrained to physically-relevant search directions by sensitivity analysis, and then matched to predictions using adaptive sampling. Using this feedback loop, data-constrained estimates of sintering model parameters along with uncertainty bounds are obtained.

scholarly journals Solar and Temporal Effects on Escherichia coli Concentration at a Lake Michigan Swimming Beach

2004 ◽  
Vol 70 (7) ◽  
pp. 4276-4285 ◽  
Author(s):  
Richard L. Whitman ◽  
Meredith B. Nevers ◽  
Ginger C. Korinek ◽  
Muruleedhara N. Byappanahalli
Keyword(s):  
Escherichia Coli ◽  
Uv Radiation ◽  
Wave Height ◽  
Lake Level ◽  
Lake Michigan ◽  
Management Strategies ◽  
Day Length ◽  
E Coli ◽  
In Situ Experiments

ABSTRACT Studies on solar inactivation of Escherichia coli in freshwater and in situ have been limited. At 63rd St. Beach, Chicago, Ill., factors influencing the daily periodicity of culturable E. coli, particularly insolation, were examined. Water samples for E. coli analysis were collected twice daily between April and September 2000 three times a week along five transects in two depths of water. Hydrometeorological conditions were continuously logged: UV radiation, total insolation, wind speed and direction, wave height, and relative lake level. On 10 days, transects were sampled hourly from 0700 to 1500 h. The effect of sunlight on E. coli inactivation was evaluated with dark and transparent in situ mesocosms and ambient lake water. For the study, the number of E. coli samples collected (n) was 2,676. During sunny days, E. coli counts decreased exponentially with day length and exposure to insolation, but on cloudy days, E. coli inactivation was diminished; the E. coli decay rate was strongly influenced by initial concentration. In situ experiments confirmed that insolation primarily inactivated E. coli; UV radiation only marginally affected E. coli concentration. The relationship between insolation and E. coli density is complicated by relative lake level, wave height, and turbidity, all of which are often products of wind vector. Continuous importation and nighttime replenishment of E. coli were evident. These findings (i) suggest that solar inactivation is an important mechanism for natural reduction of indicator bacteria in large freshwater bodies and (ii) have implications for management strategies of nontidal waters and the use of E. coli as an indicator organism.

scholarly journals Primary Production, an Index of Climate Change in the Ocean: Satellite-Based Estimates over Two Decades

2020 ◽  
Vol 12 (5) ◽  
pp. 826 ◽  
Author(s):  
Gemma Kulk ◽  
Trevor Platt ◽  
James Dingle ◽  
Thomas Jackson ◽  
Bror F. Jönsson ◽  
...  
Keyword(s):  
Primary Production ◽  
Environmental Variables ◽  
Linear Trend ◽  
In Situ Measurements ◽  
Marine Phytoplankton ◽  
Initial Slope ◽  
Model Parameters ◽  
Photosynthetic Parameters ◽  
Photosynthetic Response

Primary production by marine phytoplankton is one of the largest fluxes of carbon on our planet. In the past few decades, considerable progress has been made in estimating global primary production at high spatial and temporal scales by combining in situ measurements of primary production with remote-sensing observations of phytoplankton biomass. One of the major challenges in this approach lies in the assignment of the appropriate model parameters that define the photosynthetic response of phytoplankton to the light field. In the present study, a global database of in situ measurements of photosynthesis versus irradiance (P-I) parameters and a 20-year record of climate quality satellite observations were used to assess global primary production and its variability with seasons and locations as well as between years. In addition, the sensitivity of the computed primary production to potential changes in the photosynthetic response of phytoplankton cells under changing environmental conditions was investigated. Global annual primary production varied from 38.8 to 42.1 Gt C yr − 1 over the period of 1998–2018. Inter-annual changes in global primary production did not follow a linear trend, and regional differences in the magnitude and direction of change in primary production were observed. Trends in primary production followed directly from changes in chlorophyll-a and were related to changes in the physico-chemical conditions of the water column due to inter-annual and multidecadal climate oscillations. Moreover, the sensitivity analysis in which P-I parameters were adjusted by ±1 standard deviation showed the importance of accurately assigning photosynthetic parameters in global and regional calculations of primary production. The assimilation number of the P-I curve showed strong relationships with environmental variables such as temperature and had a practically one-to-one relationship with the magnitude of change in primary production. In the future, such empirical relationships could potentially be used for a more dynamic assignment of photosynthetic rates in the estimation of global primary production. Relationships between the initial slope of the P-I curve and environmental variables were more elusive.

scholarly journals Empirically based minimalistic model for representing seasonal phytoplankton dynamics

2020 ◽  
Vol 640 ◽  
pp. 63-77
Author(s):  
SH Piltz ◽  
PG Hjorth ◽  
Ø Varpe
Keyword(s):  
Differential Equation ◽  
Primary Production ◽  
Equation Model ◽  
Trophic Levels ◽  
Model Parameters ◽  
Division Rate ◽  
The North ◽  
Approximate Bayesian ◽  
Relative Change

Supported by chl a satellite data in the North Atlantic (and phytoplankton division rates computed from that data), the disturbance-recovery hypothesis for the initiation of phytoplankton blooms posits that the change in chl a concentration is proportional to the relative change in the phytoplankton division rate. We used this hypothesis, introduced by Behrenfeld, as a principal model assumption and constructed a non-autonomous ordinary differential equation model for seasonally varying chl a concentrations. Our quantitative comparison between model simulations and in situ measurements of chl a and primary production collected from a Swedish fjord was 2-fold: first, using approximate Bayesian computations, we found distributions of values for the 3 model parameters that best described the chl a data. Then, we validated our model by comparing the simulated (not fitted) division rate to the division rate determined from the data. Our minimalistic model was able to capture (1) the yearly trend in the chl a concentration, (2) the pattern of growth and decline in the phytoplankton division rate, and (3) the decreasing trend in the relative change of the division rate exhibited in the data for several individual years. Moreover, the modeling efficiency was positive (between 0.3 and 0.9 with an average of 0.63) for all 11 yr included in this study. We conclude that the change in chl a concentration being proportional to the relative change in the division rate is a possible explanation for the bloom dynamics in the Gullmar fjord. In addition, our work provides a simple and empirically based differential equation for representing yearly dynamics of primary production, e.g. for generating ecological hypotheses using models of other trophic levels.

Dynamics of Lake Michigan Phytoplankton: Primary Production and Growth

1987 ◽  
Vol 44 (3) ◽  
pp. 499-508 ◽  
Author(s):  
Gary L Fahnenstiel ◽  
Donald Scavia
Keyword(s):  
Primary Production ◽  
Thermal Stratification ◽  
Lake Michigan ◽  
Production Model ◽  
Daily Production ◽  
Model Estimate ◽  
Phytoplankton Primary Production ◽  
Net Production ◽  
Assimilation Number

Primary production was measured with the 14C technique during May through July–August 1982–84. 14C experiments varied from short-term incubations (1–2 h) in a photosynthesis–irradiance (P–I) chamber to 24-h in situ incubations. The maximum assimilation number from six P–I experiments during thermal stratification averaged 2.1 mg C∙mg Chl−1∙h−1 which agreed well with estimates from the 1970s. Chlorophyll-corrected P–I curves were combined with incident irradiation, chlorophyll concentrations, and extinction coefficients to estimate daily production (model estimate). Summer average integral production estimates in 1983 and 1984 were 615–630 mg C∙m−2∙d−1. Approximately 50% of summer primary production occurred below the epilimnion. Daily model production estimates were higher than 24-h in situ estimates at light intensities above Ik, the light saturation parameter, and similar at intensities below Ik. Comparisons of production estimates converted to growth rates suggest that 24-h in situ estimates provide a measure close to net production whereas model estimates provide a measure greater than net production. Summer epilimnetic growth rate estimates were low (range 0.06–0.60∙d−1), reflecting the limited availability of phosphorus.

An in situ and ex situ TEM study of the formation of thin cobalt silicide films by molecular beam epitaxy on the silicon (100) surface

1988 ◽  
Vol 46 ◽  
pp. 884-885
Author(s):  
D. Loretto ◽  
J. M. Gibson ◽  
S. M. Yalisove ◽  
R. T. Tung
Keyword(s):  
Molecular Beam Epitaxy ◽  
Molecular Beam ◽  
Defect Density ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Ex Situ ◽  
Metal Base ◽  
In Situ Experiments ◽  
Potential Applications

The cobalt disilicide/silicon system has potential applications as a metal-base and as a permeable-base transistor. Although thin, low defect density, films of CoSi2 on Si(111) have been successfully grown, there are reasons to believe that Si(100)/CoSi2 may be better suited to the transmission of electrons at the silicon/silicide interface than Si(111)/CoSi2. A TEM study of the formation of CoSi2 on Si(100) is therefore being conducted. We have previously reported TEM observations on Si(111)/CoSi2 grown both in situ, in an ultra high vacuum (UHV) TEM and ex situ, in a conventional Molecular Beam Epitaxy system.The procedures used for the MBE growth have been described elsewhere. In situ experiments were performed in a JEOL 200CX electron microscope, extensively modified to give a vacuum of better than 10-9 T in the specimen region and the capacity to do in situ sample heating and deposition. Cobalt was deposited onto clean Si(100) samples by thermal evaporation from cobalt-coated Ta filaments.

Electron and ion irradiation-induced dissolution of mechanical twins in the intermetalic U3Si: An in situ HVEM study

1989 ◽  
Vol 47 ◽  
pp. 652-653
Author(s):  
Charles W. Allen ◽  
Robert C. Birtcher
Keyword(s):  
Elevated Temperatures ◽  
Ion Irradiation ◽  
Ion Beam ◽  
National Laboratory ◽  
Argonne National Laboratory ◽  
Heavy Ion ◽  
High Energy ◽  
Mechanical Twinning ◽  
In Situ Experiments

The uranium silicides, including U3Si, are under study as candidate low enrichment nuclear fuels. Ion beam simulations of the in-reactor behavior of such materials are performed because a similar damage structure can be produced in hours by energetic heavy ions which requires years in actual reactor tests. This contribution treats one aspect of the microstructural behavior of U3Si under high energy electron irradiation and low dose energetic heavy ion irradiation and is based on in situ experiments, performed at the HVEM-Tandem User Facility at Argonne National Laboratory. This Facility interfaces a 2 MV Tandem ion accelerator and a 0.6 MV ion implanter to a 1.2 MeV AEI high voltage electron microscope, which allows a wide variety of in situ ion beam experiments to be performed with simultaneous irradiation and electron microscopy or diffraction.At elevated temperatures, U3Si exhibits the ordered AuCu3 structure. On cooling below 1058 K, the intermetallic transforms, evidently martensitically, to a body-centered tetragonal structure (alternatively, the structure may be described as face-centered tetragonal, which would be fcc except for a 1 pet tetragonal distortion). Mechanical twinning accompanies the transformation; however, diferences between electron diffraction patterns from twinned and non-twinned martensite plates could not be distinguished.

A computer-control program for TEM in situ fatigue experiments

1989 ◽  
Vol 47 ◽  
pp. 620-621
Author(s):  
Kenneth S. Vecchio ◽  
John A. Hunt
Keyword(s):  
Slow Crack Growth ◽  
Computer Control ◽  
Control Program ◽  
Video Tape ◽  
Computer Control System ◽  
Transmission Electron ◽  
In Situ Experiments ◽  
Tremendous Amount ◽  
And Control

In-situ experiments conducted within a transmission electron microscope provide the operator a unique opportunity to directly observe microstructural phenomena, such as phase transformations and dislocation-precipitate interactions, “as they happen”. However, in-situ experiments usually require a tremendous amount of experimental preparation beforehand, as well as, during the actual experiment. In most cases the researcher must operate and control several pieces of equipment simultaneously. For example, in in-situ deformation experiments, the researcher may have to not only operate the TEM, but also control the straining holder and possibly some recording system such as a video tape machine. When it comes to in-situ fatigue deformation, the experiments became even more complicated with having to control numerous loading cycles while following the slow crack growth. In this paper we will describe a new method for conducting in-situ fatigue experiments using a camputer-controlled tensile straining holder.The tensile straining holder used with computer-control system was manufactured by Philips for the Philips 300 series microscopes. It was necessary to modify the specimen stage area of this holder to work in the Philips 400 series microscopes because the distance between the optic axis and holder airlock is different than in the Philips 300 series microscopes. However, the program and interfacing can easily be modified to work with any goniometer type straining holder which uses a penrmanent magnet motor.

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