Limited Growth Rate Research Articles

Multispecies-coadsorption-induced rapid preparation of graphene glass fiber fabric and applications in flexible pressure sensor

Direct chemical vapor deposition (CVD) growth of graphene on dielectric/insulating materials is a promising strategy for subsequent transfer-free applications of graphene. However, graphene growth on noncatalytic substrates is faced with thorny issues, especially the limited growth rate, which severely hinders mass production and practical applications. Herein, graphene glass fiber fabric (GGFF) is developed by graphene CVD growth on glass fiber fabric. Dichloromethane is applied as a carbon precursor to accelerate graphene growth, which has a low decomposition energy barrier, and more importantly, the produced high-electronegativity Cl radical can enhance adsorption of active carbon species by Cl–CH2 coadsorption and facilitate H detachment from graphene edges. Consequently, the growth rate is increased by ~3 orders of magnitude and carbon utilization by ~960-fold, compared with conventional methane precursor. The advantageous hierarchical conductive configuration of lightweight, flexible GGFF makes it an ultrasensitive pressure sensor for human motion and physiological monitoring, such as pulse and vocal signals.

Costs of ribosomal RNA stabilization affect ribosome composition at maximum growth rate

Ribosomes are key to cellular self-fabrication and limit growth rate. While most enzymes are proteins, ribosomes consist of 1/3 protein and 2/3 ribonucleic acid (RNA) (in E. coli).Here, we develop a mechanistic model of a self-fabricating cell, validated across diverse growth conditions. Through resource balance analysis (RBA), we explore the variation in maximum growth rate with ribosome composition, assuming constant kinetic parameters.Our model highlights the importance of RNA instability. If we neglect it, RNA synthesis is always cheaper than protein synthesis, leading to an RNA-only ribosome at maximum growth rate. Upon accounting for RNA turnover, we find that a mixed ribosome composed of RNA and proteins maximizes growth rate. To account for RNA turnover, we explore two scenarios regarding the activity of RNases. In (a) degradation is proportional to RNA content. In (b) ribosomal proteins cooperatively mitigate RNA instability by protecting it from misfolding and subsequent degradation. In both cases, higher protein content elevates protein synthesis costs and simultaneously lowers RNA turnover expenses, resulting in mixed RNA-protein ribosomes. Only scenario (b) aligns qualitatively with experimental data across varied growth conditions.Our research provides fresh insights into ribosome biogenesis and evolution, paving the way for understanding protein-rich ribosomes in archaea and mitochondria.

Investigation into struvite precipitation: A commonly encountered problem during fermentations on chemically defined media.

Chemically defined mineral media are widely used in bioprocesses, as these show less batch to batch variation compared with complex media. Nonetheless, the recommended media formulations often lead to the formation of precipitants at elevated pH values. These precipitates are insoluble and reduce the availability of macronutrients to the cells, which can result in limiting growth rates and lower productivity. They can also damage equipment by clogging pipes, hoses, and spargers in stirred tank fermenters. In this study, the observed precipitate was analyzed via X-ray fluorescence spectroscopy and identified as the magnesium ammonium phosphate salt struvite (MgNH4 PO4 × 6H2 O). The solubility of struvite crystals is known to be extremely low, causing the macronutrients magnesium, phosphate, and ammonium to be bound in the struvite crystals. Here, it was shown that struvite precipitates can be redissolved under common fermentation conditions. Furthermore, it was found that the struvite particle size distribution has a significant effect on the dissolution kinetics, which directly affects macronutrient availability. At a certain particle size, struvite crystals rapidly dissolved and provided unlimiting growth conditions. Therefore, struvite formation should be considered during media and bioprocess development, to ensure that the dissolution kinetics of struvite are faster than the growth kinetics.

Identification of clean energy development routes under carbon emission constraints: A path towards structural adjustment of the power system

Clarifying the clean energy (CE) development path is significant for realizing energy system transformation, coping with climate risks, and ensuring energy and ecological security. This paper uses national data from China from 1978 to 2021 as a sample. It considers the year-by-year dynamic indicators of changes in technology, population, industry, and economic factors in the short term. It takes the mandatory carbon emission reduction targets set by the country as the basis for carbon constraints. The Markov chain model was introduced to construct a power demand structure prediction model under scenarios to more accurately quantify the energy-saving and emission-reduction paths under different carbon constraints and economic development scenarios. The results show that China's electricity demand will rapidly grow in the short term. The upper limit constraint of thermal power generation under the high and normal economic growth models still has room to grow in the short term under the target carbon emission constraint scenario. During 2025–2030, the overall lower limit growth rate of the CE power generation structure under the target emission reduction scenario must exceed 8%, and the overall growth rate under the high-efficiency emission reduction scenario must exceed 12%. By 2030, the proportion of hydropower in CE generation is estimated to decrease to 33.7%, while nuclear power, wind power, and photovoltaic power generation will increase to 16.3%, 30.5% and 19.5%, respectively. These results provide a reference for the government to formulate a CE development path against the background of carbon constraints.

PSV-28 Effects of the Dietary Concentrate Level and Harvest Weight on Growth Performance of Spanish Goat Wethers and Doelings

Abstract Thirty-six Spanish goat wethers and 36 doelings with initial mean age of 4.3 ± 0.03 months and body weight (BW) of 20.6 and 18.6 kg, respectively (SEM = 0.41), were used in 2 phases to determine effects of dietary concentrate level and harvest weight on growth performance. Three animals of each type were allocated to 12 pens for a total of 6 per pen. The diet in the first phase, 13 weeks in length, had 20% concentrate and 80% forage (20C) with crude protein and neutral detergent fiber (NDF) concentrations of 13 and 50%, respectively. At the end of Phase 1, animals in 2 pens were harvested. In phase 2 that lasted 9 to 11 weeks, two pens per dietary treatment and animal type continued to be fed diets with different levels of concentrate (20C, 40C, 50C, 60C, and 70C) with the same crude protein concentration of 13% and NDF level of 50, 35, 33, 33, and 31%, respectively. Animals were harvested from treatments of 50C and 70C, 40C and 60C, and 20C after 9, 10, and 11 weeks, respectively. Dry matter intake in Phase 1 was 733 ± 18.1 g/day and 3.39 ± 0.070 % BW, with an average BW during the phase of 21.6 ± 0.26 kg. Average daily gain (ADG) in Phase 2 was not affected by diet or diet × animal type (P = 0.712) but was greater (P < 0.05) for wethers than for doelings (44 and 18 g, respectively; SEM = 5.4). There was a tendency (P = 0.055) for differences in ADG among treatments (4, 44, 43, 17, and 45 g for 20C, 40C, 50C, 60C, and 70C, respectively; SEM = 8.7). Dry matter intake in g/day in Phase 2 was similar among treatments (644, 750, 680, 597, and 621 g/day; SEM = 36.9) but in % BW was greatest among diets (P < 0.05) for 40C (2.73, 3.25, 2.84, 2.62, and 2.63 for 20C, 40C, 50C, 60C, and 70C, respectively; SEM = 0.062). Also, there was a tendency (P = 0.057) for ADG during the entire experiment to differ among treatments (46, 17, 27, 30, 20, and 30 for 20C (phase 1 only) 20C, 40C, 50C, 60C, and 70C (phase 1 and phase 2), respectively; SEM = 5.0). These results suggest that a low concentrate diet followed by diets higher in concentrate containing similar CP and NDF content of 31 to 35% may not influence growth performance of Spanish goat wethers and doelings, but continuous feeding of a low concentrate diet with 50% NDF limits growth rate.

Whole-cell metabolic control analysis

Since its conception some fifty years ago, metabolic control analysis (MCA) aims to understand how cells control their metabolism by adjusting the activity of their enzymes. Here we extend its scope to a whole-cell context. We consider metabolism in the evolutionary context of growth-rate maximisation by optimisation of protein concentrations. This framework allows for the prediction of flux control coefficients from proteomics data or stoichiometric modelling. Since genes compete for finite biosynthetic resources, we treat all protein concentrations as interdependent. We show that elementary flux modes (EFMs) emerge naturally as the optimal metabolic networks in the whole-cell context and we derive their control properties. In the evolutionary optimum, the number of expressed EFMs is determined by the number of protein-concentration constraints that limit growth rate. We use published glucose-limited chemostat data of S. cerevisiae to illustrate that it uses only two EFMs prior to the onset of fermentation and that it uses four EFMs during fermentation. We discuss published enzyme-titration data to show that S. cerevisiae and E. coli indeed can express proteins at growth-rate maximising concentrations. Accordingly, we extend MCA to elementary flux modes operating at an optimal state. We find that the expression of growth-unassociated proteins changes results from classical metabolic control analysis. Finally, we show how flux control coefficients can be estimated from proteomics and ribosome-profiling data. We analyse published proteomics data of E. coli to provide a whole-cell perspective of the control of metabolic enzymes on growth rate. We hope that this paper stimulates a renewed interest in metabolic control analysis, so that it can serve again the purpose it once had: to identify general principles that emerge from the biochemistry of the cell and are conserved across biological species.

Re-evaluating cloud chamber constraints on depositional ice growth in cirrus clouds – Part 1: Model description and sensitivity tests

Abstract. Ice growth from vapor deposition is an important process for the evolution of cirrus clouds, but the physics of depositional ice growth at the low temperatures (<235 K) characteristic of the upper troposphere and lower stratosphere is not well understood. Surface attachment kinetics, generally parameterized as a deposition coefficient αD, control ice crystal habit and also may limit growth rates in certain cases, but significant discrepancies between experimental measurements have not been satisfactorily explained. Experiments on single ice crystals have previously indicated the deposition coefficient is a function of temperature and supersaturation, consistent with growth mechanisms controlled by the crystal's surface characteristics. Here we use observations from cloud chamber experiments in the Aerosol Interactions and Dynamics in the Atmosphere (AIDA) aerosol and cloud chamber to evaluate surface kinetic models in realistic cirrus conditions. These experiments have rapidly changing temperature, pressure, and ice supersaturation such that depositional ice growth may evolve from diffusion limited to surface kinetics limited over the course of a single experiment. In Part 1, we describe the adaptation of a Lagrangian parcel model with the Diffusion Surface Kinetics Ice Crystal Evolution (DiSKICE) model (Zhang and Harrington, 2014) to the AIDA chamber experiments. We compare the observed ice water content and saturation ratios to that derived under varying assumptions for ice surface growth mechanisms for experiments simulating ice clouds between 180 and 235 K and pressures between 150 and 300 hPa. We found that both heterogeneous and homogeneous nucleation experiments at higher temperatures (>205 K) could generally be modeled consistently with either a constant deposition coefficient or the DiSKICE model assuming growth on isometric crystals via abundant surface dislocations. Lower-temperature experiments showed more significant deviations from any depositional growth model, with different ice growth rates for heterogeneous and homogeneous nucleation experiments.

Different nitrogen acquirement and utilization strategies might determine the ecological competition between ferns and angiosperms.

The abundance or decline of fern populations in response to environmental change has been found to be largely dependent on specific physiological properties that distinguish ferns from angiosperms. Many studies have focused on water use efficiency and stomatal behaviours, but the effects of nutrition acquirement and utilization strategies on niche competition between ferns and flowering plants are rarely reported. We collected 34 ferns and 42 angiosperms from the Botanic Garden of Hokkaido University for nitrogen (N), sulphur (S), NO3- and SO42- analysis. We then used a hydroponic system to compare the different N and S utilization strategies between ferns and angiosperms under N deficiency conditions. Ferns had a significantly higher NO3--N concentration and NO3--N/N ratio than angiosperms, although the total N concentration in ferns was remarkably lower than that in the angiosperms. Meanwhile, a positive correlation between N and S was found, indicating that nutrient concentration is involved in assimilation. Pteris cretica, a fern species subjected to further study, maintained a slow growth rate and lower N requirement in response to low N stress, while both the biomass and N concentration in wheat (Triticum aestivum) responded quickly to N deficiency conditions. The different nutritional strategies employed by ferns and angiosperms depended mainly on the effects of phylogenetic and evolutionary diversity. Ferns tend to adopt an opportunistic strategy of limiting growth rate to reduce N demand and store more pooled nitrate, whereas angiosperms probably utilize N nutrition to ensure as much development as possible under low N stress. Identifying the effects of mineral nutrition on the evolutionary results of ecological competition between plant species remains a challenge.

Neraca Kehidupan Spodoptera pectinicornis (Hampson) dengan Pakan Gulma Kayu Apu Pistia stratiotes Linn yang diberi Pupuk NPK dan AB Mix

This study aims to examine the life balance of the biological control agent Spodoptera pectinicornis fed Pistia stratiotes with NPK and AB mix fertilization.. The research was carried out from March to May 2021 at the Laboratory Pengendalian Hayati and Greenhouse Entomology Faculty of Agriculture University Lambung Mangkurat Banjarbaru. The data in this study were analyzed descriptively by calculating the population. S. pectinicornis in one life cycle. There are 3 treatments and 3 replications on the 100 egg s. pectinicornis, The highest gross reproductive rate (GRR) was in the AB mix treatment of 1912 individuals/generation. The highest net reproduction rate (Ro) was found in the AB mix treatment of 129.520. The average value of the shortest generation period (T) in the NPK fertilizer treatment was only 26.334 days. The highest intrinsic growth rate (r) was found in the AB mix fertilizer treatment of 0.164 individuals/parent/day. The calculation of the limited growth rate (λ) showed that the AB mix treatment had the highest population increase of 1,174 individuals/parent/day. Apu wood treated with NPK and AB mix fertilizers can increase the rate of population development in the life table of the insect S. pectinicornis.

Effect of catalyst composition on growth and crack defects of large diamond single crystal under high temperature and pressure

Under the condition of 5.6 GPa and 1250–1450 ℃, the diamond single crystals are synthesized in a cubic anvil high-pressure and high-temperature apparatus. High-purity FeNiCo solvents or NiMnCo solvents are chosen as the catalysts. High-purity (99.99%) graphite powders selected as a carbon source. High-quality abrasive grade diamond single crystals with relatively developed (100) or (111) crystal planes are used as crystal seeds. The effects of catalyst composition on crack defects in diamond single crystals are studied carefully. Firstly, using FeNiCo and NiMnCo catalysts respectively, we carry out the diamond single crystal growth experiments. It is found that under the same crystal growth condition, the probability of crystal crack defects in diamond single crystals grown with FeNiCo catalyst is significantly higher than that of crystals grown with NiMnCo catalyst. We believe that this is related to the high viscosity, poor fluidity of FeNiCo catalyst melt, and the large specific surface area of the crystal during growth, which leads to its high requirements for the stability of growth conditions. Secondly, the relationship between the growth time and the limit weight gain speed of the diamond single crystal synthesized, respectively, by FeNiCo catalyst and NiMnCo catalyst are investigated. The results are shown below. 1) The limiting growth rate of diamond single crystal increases with the growth time going by. 2) In the same growth time, the limit growth rate of diamond crystal grown with NiMnCo catalyst is higher than that of diamond crystal grown with NiMnCo catalyst. Thirdly, by scanning electron microscopy (SEM), we calibrate the surface morphology of the synthesized diamond single crystal. The test results show that the diamond single crystal has a high surface flatness. Even for the crystals with crack defects in the interior, the surface flatness is still good. However, Fourier transform infrared (FTIR) measurements show that the nitrogen impurity content of diamond crystal grown by FeNiCo catalyst with crack defect is about 3.66×10<sup>–4</sup>. The content of nitrogen impurity in the crystal grown by NiMnCo catalyst without crack defect is about 4.88×10<sup>–4</sup>. The results show that there is no direct correlation between nitrogen impurity content and crack defects in diamond crystal.

Beef embryos in dairy cows: calfhood growth of Angus-sired calves from Holstein, Jersey, and crossbred beef dams.

Improved reproductive management has allowed dairy cow pregnancies to be optimized for beef production. The objective of this sire-controlled study was to characterize the effects of beef or dairy maternal genetics and the dairy management system on calf growth. Pregnancies were created with a 2 × 2 factorial arrangement of dam breed (Holstein or Jersey) and mating type (artificial insemination or implantation of an in vitro produced embryo from a commercial beef cow oocyte). Resulting calves were reared in a calf ranch. Additionally, commercial beef cows were inseminated and reared resulting calves on range. Therefore, the five treatments were Angus × Holstein (A × H; n = 19), Angus × Jersey (A × J; n = 22), Angus × beef gestated by Holstein (H ET; n = 18), Angus × beef gestated by Jersey (J ET; n = 8), and Angus × beef raised by beef (A × B; n = 20). Beginning at birth, calf body weight, cannon circumference, forearm circumference, top width, hip width, and hip height were measured approximately every 28 d until ~196 d of age. At birth, A × J calves weighed the least (P < 0.01). At 150 d of age, body weight was greatest (P < 0.05) among A × B calves, intermediate among H ET and A × H calves, and least among J ET and A × J calves (P < 0.05). Morphometric differences were detected between treatments (multivariate analysis of variance, P < 0.01). Primary discriminant function scores identified A × B calves having lesser values than A × J or A × H calves (analysis of variance [ANOVA], P < 0.01); A × B calves had greater cannon circumference, greater top width, and less hip height (standardized loadings of -0.47, -0.48, and 0.63, respectively). Secondary discriminant function scores identified J ET and H ET to have greater forearm circumference-a key indicator of muscling-than A × J or A × H (ANOVA, P < 0.01; standardized loading of 0.99). The dairy management system limited growth rate of beef genetics compared to the beef management system. In addition, Holstein dams transmitted greater growth potential than Jersey dams. Replacing maternal dairy genetics with beef genetics moderated frame size and created a more muscular phenotype.

Effects of Nano-Graphene Oxide on the Growth and Reproductive Dynamics of Spodoptera frugiperda Based on an Age-Stage, Two-Sex Life Table.

Simple SummaryFall armyworm (FAW), Spodoptera frugiperda, is an important pest in a variety of different crops. Graphene oxide (GO) is a promising candidate used in a biological context because of its versatility. In agriculture, GO could be potentially used as a pesticide additive to improve the efficacy of insecticides. In this study, the effects of GO on the development and reproduction of FAWs were determined based on life table analysis. The results showed that GO could prolong the duration of the egg stage and instar larval stages, but shorten lifespan of male and female adults, and this effect was enhanced with increasing GO concentrations. GO also reduced the number of eggs laid by female moths. In addition, the expression of genes related to reproduction have also been affected by GO. In conclusion, GO prolonged the developmental period of FAWs, decreased fecundity, and may decline the population size. The study provides a basis for the rational use of GO as a pesticide synergist for FAW control.The development and reproduction of the fall armyworm (FAW), Spodoptera frugiperda, which were reared on artificial diets containing nano-graphene oxide (GO), were determined based on age-stage, two-sex life table analysis. The results showed that GO had adverse effects on FAWs. Compared with the control, the duration of the egg stage and first, second, and sixth instar larval stages increased with increasing GO concentrations; however, the lifespan of male and female adults decreased with increasing GO concentrations. Weights of FAW pupae that were supplied with GO-amended diets increased by 0.17–15.20% compared to the control. Intrinsic growth, limited growth, and net reproductive rates of FAWs feeding on GO supplemented diets were significantly lower than the control, while mean generational periods (0.5 mg/g: 38.47; 1 mg/g: 40.38; 2 mg/g: 38.42) were significantly longer than the control. The expression of genes encoding vitellogenin (Vg) and vitellogenin receptor (VgR) expression was abnormal in female FAW adults feeding on GO-amended diets; the number of eggs laid decreased relative to the control, but Vg expression increased. In conclusion, GO prolonged the developmental period of FAWs, decreased fecundity, and led to a decline in the population size. The study provides a basis for the rational use of GO as a pesticide synergist for FAW control.

Response of model-based cambium phenology and climatic factors to tree growth in the Altai Mountains, Central Asia

• The principal growth limiting factor shifts from temperature to soil moisture from RU to FY. • Cambial dynamic was bimodal pattern in AL, right-skewed unimodal in FY and unimodal in RU. • The length of growing seasons had a significant positive trends in two sites from Northwest China – Chinese Altai Mountains for the last six decades. • The intra-seasonal growth rate regulated tree growth rather than length of growing season. It is important to study the relationships between tree growth and phenology and climate factors in Central Asia for the sustainable development of forest ecology and the exploration of carbon sink potential in the region in a context of global change. Herein, the process-based Vaganov-Shashkin model was used to simulate tree-ring growth rates, to assess a cambial phenology (start and end of growing season) of larch trees ( Larix sibirica ) based on three sites located on three different latitudes in the Altai-Sayan Mountains in Central Asia over 1960–2018. It was shown that the principal factor limiting growth rates was temperature in RU (located in southern central Siberia), cambial dynamic was unimodal. In RU site, although the length of growing season did not change significantly over the past 59 years, it was correlated with tree radial growth. Moisture was the principal factor limiting the growth rates of AL and FY (located in Chinese Altai Mountains), and cambium dynamics were bimodal and unimodal, respectively. Temperature and precipitation before the start of the growing season lengthen the growing season, but this did not promote the tree radial growth. In conclusion, we determined that the climate-influenced intra-seasonal growth rate regulated tree growth rather than length of growing season in this area. In this study, the VS-simulation showed high potential develop a long-term reconstruction of cambial phenology in the Altai Mountains, which was conducive to a more comprehensive understanding of the exogenous-endogenous factors effects on tree-ring growth.

PSIV-A-2 Beef Genetics in the Dairy Management System: Management System and Maternal Genetic Effects on Calf Growth and Body Measurements

Abstract Improved reproductive management allowed dairy cow pregnancies to be optimized for beef production. The objective of this sire-controlled study was to characterize effects of maternal genetics and the dairy management system on calf growth. Pregnancies were created with a 2 × 2 factorial arrangement of dam breed (Holstein or Jersey) and mating type (artificial insemination or implantation of an in vitro produced embryo from a commercial beef cow oocyte). Resulting calves were reared in a calf ranch. Additionally, commercial beef cows were inseminated and reared resulting calves on range. Therefore, the five treatments were Angus × Holstein (A×H; n = 19), Angus × Jersey (A×J; n = 22), Angus × Beef gestated by Holstein (H-ET; n = 18), Angus × Beef gestated by Jersey (J-ET; n = 8), and Angus × Beef raised by beef (A×B; n = 20). Beginning at birth, calf body weight, cannon circumference, forearm circumference, top width, hip width, and hip height were measured approximately every 28 days until approximately 196 days of age. At birth, A×J calves weighed the least (P &amp;lt; 0.01). At 150 days of age, body weight was greatest (P &amp;lt; 0.05) among A×B calves, intermediate among H-ET and A×H calves, and least among J-ET and A×J calves (P &amp;lt; 0.05). Morphometric differences were detected between treatments (MANOVA P &amp;lt; 0.01). Primary discriminant function scores identified A×B calves having lesser values than A×J or A×H calves (ANOVA P &amp;lt; 0.01); A×B calves had greater cannon circumference, greater top width, and less hip height (standardized loadings of -0.47, -0.48, and 0.63, respectively). The dairy management system limited growth rate of beef genetics compared to the beef management system. In addition, Holstein dams transmitted greater growth potential than Jersey dams. Replacing maternal dairy genetics with beef genetics increased top width and decreased hip height.

Al – Ti – B master alloys: structure formation in modified alloys

This paper provides an overview of existing grain refinement mechanisms and describes the solidification kinetics typical of alloys modified with the Al &ndash; Ti &ndash; B system. Of practical interest are intermetallic compounds of the binary Al &ndash; Ti system, the state diagram of which requires further study. It was found that, with titanium concentrations being low, the behaviour of the system is influenced by peritectic reaction leading to &alpha;-grains of aluminium forming on titanium aluminide particles (TiAl3). A unique feature of the Al &ndash; Ti system is that, compared with other alloys, it has the highest limited growth rate Q, which explains the high grain refinement performance. Microparticles of titanium diboride (TiB2) that form in the liquid state of the Al &ndash; Ti &ndash; B system act as nucleation centres for the intermediate phase of TiAl3. At the same time, TiAl3 was found to display metastable properties and it dissolves as aluminium solidifies. The classical crystallization theory defines the importance of heterogeneous substrates that help grain nucleation by lowering the threshold energy. According to the heterogeneous nucleation theory, supercooling tends to increase dramatically during grain nucleation as the discrepancy rises between the crystal lattice of the solid body and that of the substrate. In terms of constitutional supercooling, it takes lower supercooling for grain nucleation on a particle. The contributing factors include a lower rate of latent heat release and low grain growth rates. As the master alloy was introduced in the melt, the authors observed reduced modification efficiency (with the concentration &gt;1.5 %) and dropped solubility of Ti in the presence of Si. Long soaking times would lead to the master alloy gradually lose its effect. The authors also considered how the properties of master alloys can be enhanced. Thus, they looked at breaking up TiAl3 by means of plastic deformation and deagglomerating TiB2 particles by contactless mixing.

Analysis of stability and bifurcation in logistics models with harvesting in the form of the holling type III functional response

The logistic model can be applied in the field of biological studies to investigate population growth problems and some important aspects of the ecological situation. This model is a growth model with a limited population growth rate, and ecologists describe this rate as carrying capacity. Carrying capacity can be interpreted as the ideal population size, where individuals in the population can live properly in their environment. The growth rate of a population can be influenced by the harvesting factor, in this case, it is assumed that harvesting is not constant. The effect of the harvest on the growth rate can be analyzed mathematically by using the Holling type III functional response. In this paper, describe the formation of a logistic model taking into account the effects of harvesting, using the Holling type III functional response. Then, perform a nondimensional process in the model, namely simplifying a model that has four parameters to a model that only has two parameters. Next, determine the equilibrium point of the model, perform a stability analysis at that equilibrium point, and investigate the possibility of bifurcation. As result, first obtained a logistic model which has two non-dimensional parameters, where one of the equilibrium points is zero and is unstable. Next, determine another equilibrium point through an implicit equation and investigate its stability through simulation. Finally, obtained two equilibrium points, which are fold bifurcation.

Phosphorus limitation in low nitrogen lakes in New Zealand

ABSTRACT Lakes on volcanic soils of the North Island of New Zealand, compared to north temperate lakes, have low total nitrogen:total phosphorus (TN:TP) ratios, low dissolved inorganic nitrogen concentrations during summer stratification, and have positive chlorophyll a responses to N additions more frequently than to P in nutrient enrichment bioassays. This response has resulted, in some cases, to the imposition of N loading caps on some lake catchments, in contrast to nutrient management in north temperate lakes focused more on P management. To explore this possible difference in limiting nutrients, a suite of nutrient status indicators based on measurement of ambient seston stoichiometry and metabolic activity, which have been widely used in north temperate lakes, were applied to 8 lakes on volcanic terrain with previously reported N limitation. These nutrient status measurements were previously calibrated to inform whether in situ phytoplankton are growth-rate limited and, if so, which nutrient is limiting growth rate. In austral summer 2015, all 8 lakes showed indications of P limitation, and P limitation was more extreme, pervasive, and persistent (among samplings) than N limitation. Indications of N limitation were not observed without contemporaneous evidence of P limitation, but P limitation was frequently observed without evidence of N limitation. One lake, Rotorua, was not strongly nutrient limited, and phytoplankton were likely growing at or near optimum growth rates. In this study the commonly used TN:TP ratio was a poor predictor of which nutrient was potentially limiting in situ phytoplankton.

Predator–prey density-dependent branching processes

Two density-dependent branching processes are considered to model predator–prey populations. For both models, preys are considered to be the main food supply of predators. Moreover, in each generation the number of individuals of each species is distributed according to a binomial distribution with size given by the species population size and probability of success depending on the density of preys per predator at the current generation. The difference between the two proposed processes lies in the food supply of preys. In the first one, we consider that preys have all the food they need at their disposal while in the second one, we assume that the natural resources of the environment are limited and therefore there exists a competition among preys for food supplies. Results on the fixation and extinction of both species as well as conditions for the coexistence are provided for the first model. On the event of coexistence of both populations and on the prey fixation event, the limiting growth rates are obtained. For the second model, we prove that the extinction of the entire system occurs almost surely. Finally, the evolution of both models over the generations and our analytical findings are illustrated by simulated examples.

The qualitative behavior of a plankton-fish interaction model with food limited growth rate and non-constant fish harvesting

&lt;p style='text-indent:20px;'&gt;The manuscript aims to investigate the qualitative analysis of a plankton-fish interaction with food limited growth rate of plankton population and non-constant harvesting of fish population. The ecological feasibility of population densities of both plankton and fish in terms of positivity and boundedness of solutions is shown. The conditions for the existence of various equilibrium points and their stability are derived thoroughly. This study mainly focuses on how the harvesting affects equilibrium points, their stability, periodic solutions and bifurcations in the proposed system. It is shown that the system exhibits saddle-node bifurcation in the form of a collision of two interior equilibrium points. Existence conditions for the occurrence of Hopf-bifurcation around interior equilibrium points are discussed. Lyapunov coefficients are examined to check the stability properties of these periodic solutions. We have also plotted the bifurcation diagrams for saddle-node, transcritical and Hopf bifurcations. A detailed algorithm for the occurrence of Bogdanov-Takens bifurcation is derived and finally some numerical simulations are also carried out to validate the theoretical results. This work suggests that the harvesting of fish population can change the dynamics of the system, which may be useful for the ecological management.&lt;/p&gt;

Comparative characterization of growth and phylogenetic relationship of some Poaceae C3 and C4 members in aquatic and terrestrial habitats

This study investigates the suitability of aquatic habitats to the growth of some Poaceae C3 and C4 members. Also, the phylogenetic relationship among these species was evaluated. Seven species were collected from aquatic and terrestrial habitats. Growth rate was higher in the C4 than in the C3 species in both habitats. Growth rate of the C4 species and Leersia hexandra (C3) was higher in the aquatic than in the terrestrial habitat. Water use efficiency (WUE) was not limiting to the growth of the C4 species in both habitats. However, high WUE could positively affect growth of the C4 compared to the C3 species in both habitats. The C4 species had not only higher photosynthetic efficiency (photosynthetic rate/Rubisco ratio, nitrogen use efficiency) than the C3 species but also this efficiency increased in the aquatic habitat. Aquatic conditions did not limit stomatal conductance (gs) in the C4 species and L. hexandra. In the aquatic C4 species, the increase in gs could lead to an increase in photosynthetic efficiency and growth rate. In the aquatic L. hexandra (C3), the increase in gs and Rubisco could enhance photosynthetic rate, but resulting in a decrease in photosynthetic efficiency compared to the C4 species. The accumulation of internal CO2 and sugars along with the increase in Rubisco may suggest that the C3 species had a limited growth rate compared to the C4 species even in the aquatic habitat. Aquatic habitats could be optimum to the growth of these C4 species.