Saturated Growth Rate Research Articles

A three-dimensional water quality-macrophyte interaction model for shallow lakes

A dynamic three-dimensional water quality model for macrophyte-dominated shallow lakes was proposed and tested. The proposed model is capable of simulating macrophytes and its interactions with water quality constituents such as dissolved oxygen (DO), organic nitrogen, ammonia, nitrate, organic phosphorus, orthophosphate, biochemical oxygen demand, phytoplankton and the sediment layer in shallow lakes. An existing two-dimensional hydrodynamic model has been utilized in conjunction with the water quality model to simulate water levels, velocities and flow rates. The modelled macrophyte processes are photosynthesis, respiration, mortality and excretion. Hourly simulation of photosynthesis process has been realized. The hourly simulations need special attention to predict diurnal variations of DO in macrophyte dominated lakes. The proposed water quality simulation model was subjected to calibration, verification and prediction processes using the data collected from Mogan Lake, Turkey. Mogan Lake exhibits wide variations of macrophyte biomass seasonally. The lake also exhibits highly variable DO levels both seasonally and diurnally. Statistical error quantification methods have been utilized to test the goodness of fit between the water quality model predictions and field measurements. Good agreement has been achieved between model predictions and measurements. Moreover, uncertainty analysis has been carried out for macrophyte and DO constituents. The analysis showed that the magnitude of the saturated growth rate of macrophyte is the most sensitive model parameter both for macrophyte and DO. The proposed water quality simulation model gave some promising initial results as a management tool to predict the expected reductions for the undesired consequences of eutrophication problem.

Weakly Nonlinear Investigation of the Saffman–Taylor Problem in a Rectangular Hele–Shaw Cell

We analyze the Saffman–Taylor viscous fingering problem in rectangular geometry. We investigate the onset of nonlinear effects and the basic symmetries of the mode coupling equations, highlighting the link between interface asymmetry and viscosity contrast. Symmetry breaking occurs through enhanced growth of sub-harmonic perturbations. Our results explain the absence of finger tip-splitting in the early flow stages, and saturation of growth rates compared with the predictions of linear stability.

Self limiting growth on nominally oriented (111)A GaAs substrates in atomic layer epitaxy

Layer-by-layer growth on nominally oriented (111)A GaAs substrate has been performed by atomic layer epitaxy (ALE). Under enough AsH 3 feeding, the growth rate saturation of one-fourth monolayer per cycle was observed at the T g range between 560°C and 600°C and three-eighths of monolayer per cycle at the T g range below 550°C on (111)A substrate. The drastic change of the growth rate saturation at around 550°C indicates some kinds of surface reconstructions or site occupation on (111)A surface during AsH 3 supply.

Some new optical measurement techniques for the study of crystal growth and electrode processes

This paper discusses some new optical measurement techniques for the study of crystal growth and electrode processes, namely, holographic phase-contrast interferometric microphotography (HPCIM), phase conjugation interferometry (PCI) and laser diffractometry. Using these techniques, real-time crystal growth and electrode processes can be observed; solid-liquid interface boundary layers and the crystal surface morphology can be studied quantitatively and solution saturation and crystal growth rates can be measured precisely. These techniques are also compared with other methods.

Atomic Layer Epitaxy of III-V Electronic Materials

Atomic layer epitaxy (ALE) was proposed by Suntola & Antson (1) in 1977. ALE is different from conventional growth methods, such as molec­ ular beam epitaxy (MBE) and metalorganic vapor phase epitaxy (MOVPE), in that it is a stepwise monolayer growth process. This unique characteristic is due to chemical interaction saturation between a substrate surface and a reactant source gas. Accordingly, ALE monolayer growth can be achieved without precise control of growth conditions, such as growth temperature and source gas partial pressures. The name digital epitaxy was introduced by Watanabe & Usui (2) to describe this mono­ layer/cycle growth over a wide range of growth conditions. Although ALE was originally used for II-VI materials and dielectric thin films for electroluminescent display devices (3), it has recently attracted significant attention from III-V people. This is because of ALE's great potential for achieving a tomic-layer-controlled ultra-thin film heterostructures, which are rapidly being developed for application to high speed devices, opto­ electronic integrated circuits, and sophisticated quantum confinement structures. The first report on ALE of III-V materials was published by Nishizawa et al (4), who called this method molecular layer epitaxy ( MLE). They demonstrated growth rate saturation at monolayer growth for GaAs. This research was followed by further studies of ALE for III-V electronic materials in many laboratories (5-20). Presently, studies have been carried out not only for binary compounds, but also for ternary materials and

Atomie Layer Epitaxy ia a Rotating Disk Reactor

ABSTRACTCurrent difficulties of Atomic Layer Epitaxy (ALE) include relatively low growth rates and narrow process windows. Gas phase reaction, complex behavior of valve switching and purging times are suggested as the major causes [1,2]. We have used a movable X-shaped mechanical barrier to divide the growth chamber into four zones. Each zone supplies either source gas or purging hydrogen. If the barrier is positioned 0.5–2 mm from the wafer carrier, it can efficiently shear off the boundary layer and therefore reduce gas phase reactions. The substrate, constantly rotating beneath the barrier, is alternately exposed to group III or V sources by purging zones. The result is that process times are significantly reduced, saturated growth rate of 1 μm/hour is obtained and a relatively wide process window is observed. It was found that the growth mode was not purely ALE, due to source gas mixing which contributes an additional, possible kinetically limited, component of growth rate. However, this was also found to result in uniform film.

Atomic Layer Epitaxy of GaAs and InAs

AbstractThe saturation behavior of growth of GaAs and InAs by atomic layer epitaxy is studied. The growth rate is found to be strongly dependent on alkyl exposure time for the same total alkyl exposure per cycle. The longer the exposure time, the higher the saturated growth rate is. For short exposure, the growth rate saturates to a value less than one monolayer (ML)/cycle. Strong saturation of the growth rate to one ML/cycle is achieved for InAs at a growth temperature of 340°C with 3 sec of trimethylindium exposure. For GaAs, saturation of the growth rate to one ML/cycle is achieved at the growth temperature of 400°C with 10 sec of trimethylgallium exposure. At higher growth temperatures, the growth rate does not saturate but increases slowly with increasing exposure. The large physical size and finite decomposition time of the initial adsorbate are suggested as the cause for the dependence of ALE growth rate on alkyl exposure time.

Critical concentrations of tissue nitrogen and phosphorus for growth rate and yield in the freshwater blue-green alga Microcystis aeruginosa Kütz. in the tropics

Critical concentrations of tissue nitrogen and phosphorus for growth rate and yield in the freshwater blue-green alga Microcystis aeruginosa Kütz. were investigated to facilitate its production in aquaculture ponds. Growth-curve and yield experiments in flask cultures of Microcystis confirmed earlier predictions of reductions in assessed yield-derived critical concentrations caused by culture-ageing effects. Yield-derived critical levels for 90% saturated response were 4.1% N and 0.28% P. A derivation which assumed a Droop equation parameterization of growth enabled conversion of the yield-derived values to growth-rate critical concentrations. For 90% saturated growth rate these were N ≤ 5.4% and P ≤ 0.42%. Field and culture pond measurements commonly found in excess of these values and the well-known ability of algae to remove nutrients from water indicate that fertilizer applications sufficient to maintain tissue levels in excess of the critical levels would be an efficient strategy for maximum Microcystis production in culture ponds.

Growth Rate Responses of Lotic Periphytic Diatoms to Experimental Phosphorus Enrichment: The Influence of Temperature and Light

Phosphate enrichment experiments were conducted year-round at the experimental troughs research apparatus (EXTRA) on the South Thompson River in British Columbia to determine the relationship between external concentration of orthophosphate and the growth rates of lotic periphytic diatom communities. Growth rate saturation always occurred at a phosphate concentration of approximately 0.3–0.6 μg P∙L−1. The maximum growth rate (μmax-P) with phosphorus enrichment varied seasonally with temperature. The relative specific growth rates (μ:μmax-P) as a function of external phosphate were constant. Seasonal changes in solar insolation (PAR) had no effect on the autotrophic community growth rates in unamended river water. Temperature exerted the most dominant influence on phosphorus-replete growth rates.

Effect of irradiances up to 2000 μE m −2 s −1 on marine Synechococcus WH7803—II. Photosynthetic responses and mechanisms

We investigated the photosynthetic behavior of Synechococcus WH7803 when grown over the irradiance range of 30–2000 μE m −2 s −1 in nutrient-replete, continuous light, pre-adapted batch cultures. For each of 8 growth irradiances investigated, we found a unique photosynthesis vs irradiance ( P vs I) relationship. Cell- and carbon-specific photosynthetic light harvesting efficiencies (α (cell) and α (C)) decreased 10-fold from the lowest to highest growth irradiances. Chlorophyll and phycocyanin-specific efficiencies also decreased but to a lesser extent. Phycoerythrin-specific efficiencies increased ca. 2-fold with increasing irradiances. Photosynthetic capacity ( P max) approximated the in situ rate of photosynthesis ( P i ) only at growth irradiances which saturated growth rate; at light limiting irradiances, P max increased to 2.9 times P i . Photoinhibition of photosynthesis was only observed in light-limited cells. The mechanism of photoadaptation which resulted in the observed growth rate vs irradiance (μ vs I) response involved regulation of α (cell) by changes in phycobilisome size over saturating irradiances and phycobilisome numbers over limiting irradiances. Our results are consistent with previously reported field observations of α (Chl), α (cell) and P max increasing with depth, and of no photoinhibition of near-surface collected assemblages, suggesting that high irradiances in near-surface waters can support maximal growth rates of Synechococcus. These results raise important questions regarding the interpretation of parameters of P vs I measurement from field studies. Our results do not conform to the previously reported hypothesis that a significant percentage of phycoerythrin serves as a non-photosynthetic nitrogen storage compound in these cells.

Mechanism of contamination build-up induced by fine electron probe irradiation

Abstract To clarify the transfer mechanism of contaminating molecules and the dominant source of them, carbon thin films were irradiated with a fine electron probe of 12 nm dia using three types of anti-contamination devices, individually. No contamination deposit was observed for a certain period or an incubation time after the specimen was pretreated by an electron beam shower. After the incubation time, the growth rate increased gradually with the elapsed time after the electron beam shower treatment and reached the saturated rate. The incubation time and the saturated growth rate depended largely on the type of the anti-contamination device used. It can be concluded that hydrocarbon molecules being adsorbed on the specimen surface are transferred to the irradiated area by surface diffusion. The dominant source of contaminating molecules is the residual gas molecules in the vicinity of the specimen even in a clean high vacuum.

Cold-sensitive expression of transformation by a host range mutant of type 5 adenovirus.

hr1, an E1a (0-4.5 map units) host range mutant of type 5 adenovirus (Ad5), transformed a cloned rat embryo fibroblast (CREF) cell line at about a 5-fold higher frequency than wild-type (wt) Ad5 when cells were cultured at 37 degrees C. However, if the cells were infected with hr1 and maintained at 32 degrees C morphological transformation did not occur. When infected cells were shifted from 32 degrees C to 37 degrees C 2 wk postinfection, the frequency of transformation by 6 wk was identical to that of cells grown continuously at 37 degrees C, whereas cultures shifted from 37 degrees C to 32 degrees C 2 wk postinfection displayed a greater than 96% reduction in morphological transformation. hr1-transformed cells had a fibroblastic morphology as contrasted with the typical epithelioid morphology of wt Ad5-transformed cells, but hr1- and wt Ad5-transformed cells had similar saturation densities, growth rates, and agar cloning efficiencies when assayed at 37 degrees C. However, when cells transformed by hr1 at 37 degrees C were grown at 32 degrees C, they had a saturation density close to that of normal CREF cells and grew at a lower efficiency in agar than wt-transformed cells. DNA transfer/hybridization analysis of two hr1-transformed cloned cell lines, A2 and B3, indicated that A2 cells contained a complete integrated copy of the Ad5 genome, whereas in B3 cells only part of the Ad5 genome was integrated. RNA transfer and RNA/DNA filter hybridization analyses indicated that the types of viral messenger RNAs and the relative amounts of RNA transcribed were similar in the A2 and B3 cell lines when they were grown at 32 degrees C and 37 degrees C. Indirect immunofluorescence, with antisera from hamsters bearing Ad-induced tumors, indicated a temperature dependence in staining--i.e., cells grown at 37 degrees C or shifted from 32 degrees C to 37 degrees C contained intense, particulate staining in the nuclear region, whereas the staining was decreased significantly in cells cultured at 32 degrees C and in cells shifted from 37 degrees C to 32 degrees C. These findings indicate that the gene product affected by the hr1 mutation is cold sensitive and is essential for the expression of the characteristics that identify the transformed cell.

EFFECT OF NITROGEN SUPPLY ON NITROGEN CONTENT AND GROWTH RATE OF JUVENILE MACROCYSTIS PYRIFERA (PHAEOPHYTA) SPOROPHYTES1

ABSTRACTThe effect of nitrogen supply on nitrogen content and growth rate of juvenile Macrocystis pyrifera (L.) C. A. Agardh sporophytes was studied in two types of experiments: growth in continuously flowing mixtures of deep (nutrient‐rich) and surface (nutrient‐poor) seawater, and growth in batch cultures with alternate 7–10 day periods in deep and surface water. In the continuous flow experiments, the nitrogen content of the plants increased with the increased concentration of nitrate in the seawater. In the batch culture experiments, a lag period of 3–7 days often occurred before changes in the nitrogen supply were reflected in corresponding changes in the nitrogen content of the plants. Growth rates were a linear function of tissue nitrogen which varied between 1–3% dry weight. Saturation of growth rate as a function of tissue nitrogen did not occur, although tissue nitrogen levels did saturate as a function of external nitrate supply. Juvenile M. pyrifera sporophytes do not appear to “store” nitrogen. Total nitrogen varies from 1–6% dry weight in Laminariales and Fucales, but only some species of Laminaria appear to accumulate large pools of “surplus” nitrogen.

Retinoids specifically enhance the number of epidermal growth factor receptors.

Retinoids elicit many biological and biochemical responses from cells in vitro. One widely used criterion for the responsiveness of cells to retinoids is inhibition of growth; retinoids reduce the saturation density and/or growth rate of many normal and tumorigenic cell lines. Propagation of eukaryotic cells has been demonstrated to be dependent on the presence of macromolecular growth factors such as epidermal growth factor (EGF), which can stimulate proliferation of epithelial and fibroblastic cell lines. We now describe the effect of retinoids on the binding of EGF to its receptor. Retinoic acid enhances binding of 125I-labelled EGF to various fibroblastic and epidermal cell lines. It has no marked effect on the affinity of this growth factor for its receptor, but increases the number of EGF receptor sites. Retinoic acid has little effect on the binding of concanavalin A (Con A) and insulin, indicating the specific nature of the action of retinoids on cell-surface glycoproteins. Treatment of cells with the phorbol ester 12-o-tetradecanoyl phorbol-13-acetate (TPA) and retinoic acid shows poor antagonism between these compounds on EGF binding. It has been previously shown that retinoids induce or stimulate differentiation of embryonal carcinoma cells. EGF binding can be used as a marker to monitor differentiation of these cells.

Challenge of Michaelis-Menton Constants

Researchers measuring half saturation constants and growth rates are urged to evaluate their data using this proposed relationship. The replacement of the half saturation constant by biomass concentrations would eliminate the cause of variation in data analysis, eliminate the need for half saturation constants, and eliminate the anomalies in phytoplankton and nutrient predictions in lakes.

Saturation time and growth rate of parametrically excited ion acoustic waves

The amplitude evolution of parametrically excited ion acoustic waves is shown. The instabilities are generated by a strong electric field applied to a krypton plasma column.

A Growth Projection for Electricity Demand in San Diego County to the End of the Century

Abstract Growth of residential electricity demand in San Diego County between 1950 and 1970 is shown to be primarily associated with increasing saturation levels of individual appliances. Only a relatively minor contribution to the demand function is attributable to increased consumption per appliance unit. Using past saturation growth rates and an estimate of somewhat less than 1 %/yr for the increase in consumption per appliance, we arrive at a year 2000 electricity consumption level of about 12,000 kWh per average household, as compared with a 1970 level of about 4,900 kWh The electricity consumption in the commercial and industrial sector is estimated on the assumption that consumption is a linear function of commercial and industrial floor area. The 1972 estimate for the loading function is 27.6 kWh/ft2-yr. Projection of this function to later times is based on the assumption of growth along logistics curves to limiting values appropriate for all-electric structures Projections of total regional elec...