Growth Rate Coefficient Research Articles

Population structure of Indian scad fish (Decapterus russelli) that was landed at the Nusantara Fishing Port of Ternate, North Maluku, Indonesia

Indian scad fish (Decapterus russelli) is a small pelagic fish species commonly caught in Indonesian seas. Excessive fishing efforts can cause population degradation, so it is necessary to understand its population structure. The purpose of this study was to analyze the population structure parameters of Indian scad fish, including growth parameters, cohort, and mortality. Sampling was done by Stratified Random Sampling method. Data analysis used the FISAT II application. Study results showed that there were 4 cohorts. The growth parameters of Indian scad fish obtained asymptote length (L∞) of 296.15 mm, coefficient of growth rate (K) of 0.60 per year, and initial age (t0) of -0.66 years. Value of coefficient of growth rate (K) indicated that growth of scad was relatively slow. The total mortality value (Z) was 0.51 per year, natural mortality (M) was 0.0034 per year, and fishing mortality (F) was 0.51 per year. So that the highest Indian scad fish mortality was caused by fishing mortality. The exploitation rate (E) was 1 per year, indicating that the Indian scad fish resources have been overexploited.

Population dynamics of sailfin catfish (pterygoplichthys sp. Hancock, 1828) in sidenreng lake water, Sidenreng Rappang District, South Sulawesi

The aim of this research is to know some dynamic parameters of cat fishes population cohort, growth, mortality, exploitation rate, and Relative Yield per Recruitment Relative (Y / R’) based on sex. The usefulness of this research is expected to be a basic data to provide an overview of age distribution, growth patterns, and mortality as well as the estimation of cat fishes rate of exploitation in Sidenreng Lake. In addition, the results of this study are expected to become information material for appropriate and sustainable management steps. The research was conducted for two months on March until April 2019 in Sidenreng Lake, Sidenreng Rappang Regency, South Sulawesi. Analysis of sample fish was carried out at the Laboratory of Fisheries Biology, Department of Fisheries, Faculty of Marine Sciences and Fisheries, Hasanuddin University, Makassar. Sampling of catfishes is obtained from all catches of one fisherman operating in Lake Sidenreng. The number of cat fish samples obtained during the study were 1056, consisting of 565 male cat fishes and 491 female cat fishes. The results of the analysis using a 2 cm length class interval obtained 16 classes. Cohort in the cat fishes in male fish and female fish there were 2 cohorts each. The growth rate coefficient for male fish and female fish was 0.69 per year and 0.46 per year fish reach the maximum length faster than female fish. The mortality value obtained in male and female cat fishes shows that the mortality value is more due to natural mortality than the capture mortality value.

A study of brown-marbled grouper (Epinephelus fuscoguttatus) population dynamics in Takabonerate National Park Waters, South Sulawesi, Indonesia

Abstract. Fatma, Mallawa A, Najamuddin, Zainuddin M, Fachrie R. 2021. A study of brown-marbled grouper (Epinephelus fuscoguttatus) population dynamics in Takabonerate National Park Waters, South Sulawesi, Indonesia. Biodiversitas 22: 4298-4307. Understanding aspects of the population dynamics of groupers such as the brown-marbled grouper can provide valuable insights into how to manage grouper stocks effectively. Conducted from February 2020 to February 2021 in Takabonerate National Park waters, Selayar Islands District, South Sulawesi, Indonesia, this study sought to elucidate the size structure and cohorts, population growth rate, total mortality rate, fishing mortality rate, natural mortality rate, exploitation rate and yield per recruit (Y/R) of the brown-marbled grouper. Grouper samples were caught using several fishing gears (i.e., hand line fishing, spearfishing, and trapping) with a total catch of 1042 specimens. The sampled specimens exhibited significant size structure and were classified into five age-specific cohorts. The growth rate coefficient was 0.46/year, with the brown-marbled grouper population tending to exhibit slow growth (K < 0.5/year). The estimated asymptotic length was 109.0 cm. The fishing mortality was higher than the natural mortality, with an exploitation rate of 0.65, indicating that brown-marbled groupers in the waters of Takabonerate National Park have been subjected to extensive and intensive fishing, as also indicated by an estimated Y/R lower than the optimum Y/R rate.

Mechanistic insights into ureolysis mediated calcite precipitation

Microbially induced calcite precipitation (MICP) has applications in self-healing concrete, soil consolidation and bio-grouting. Development of models of processes involved in MICP is a step towards gaining mechanistic insights and building reliable predictive models of MICP. This work deals with understanding the reactions and transport processes involved in ureolysis mediated calcite precipitation in Sporosarcina pasteurii (S. pasteurii). Particularly, a simple structured model that describes urea uptake, ureolysis, ammonium assimilation and ammonium excretion processes is developed. The structured model describes extra-cellular processes like transport processes and important intra-cellular reactions involved in ureolysis. The model parameters are estimated using measured concentrations of extracellular and intracellular metabolites during experiments. In this work, The maximum specific growth rate and yield coefficient of S. pasteurii are found to be 0.78 d−1 and 4.93 gDW/g, respectively. The maximum urease activity of 1.79 μmoles/min/gDW biomass was observed during the fourth day of growth when grown in minimal media. It is shown that the urea uptake can be described by a first-order kinetics suggesting active transport. The estimated parameter of rate constant of first-order kinetics is 9.8 × 10−2d−1. On the other hand, the ammonium ion excretion takes place through free diffusion. The estimated parameter of permeability coefficient for ammonium ion diffusion is 9.2 × 10−3 m d−1.

Effect of Humidity on the Writing Speed and Domain Wall Dynamics of Ferroelectric Domains

AbstractThe switching dynamics of ferroelectric polarization under electric fields depends on the availability of screening charges in order to stabilize the switched polarization. In ferroelectrics, thin films with exposed surfaces investigated by piezoresponse force microscopy (PFM), the main source of external screening charges is the atmosphere and the water neck, and therefore relative humidity (RH) plays a major role. Here, it is shown how the dynamic writing of domains in BaTiO3 thin films changes by varying scanning speeds in the range of RH between 2.5% and 60%. The measurements reveal that the critical speed for domain writing, which is defined as the highest speed at which electrical writing of a continuous stripe domain is possible, increases non‐monotonically with RH. Additionally, the width of line domains shows a power law dependence on the writing speed, with a growth rate coefficient decreasing with RH. The size of the written domains at a constant speed as well as the creep‐factor μ describing the domain wall kinetics follow the behavior of water adsorption represented by the adsorption isotherm, indicating that the screening mechanism dominating the switching dynamics is the thickness and the structure of adsorbed water structure and its associated dielectric constant and ionic mobility.

Analysis of COVID-19 Outbreak in Ecuador Using the Logistic Model

At the end of 2019, the COVID-19 disease emerged in the city of Wuhan, China, and caused an outbreak of unusual viral pneumonia. Being highly transmissible, this novel coronavirus disease has spread fast all over the world. COVID-19 continues to challenge most developed countries in the search for an effective strategy to either prevent infection or to avoid the spreading of the disease. While several developed countries have managed to contain COVID-19, several countries in Latin America continue to report an increase in the daily number of infected people. Ecuador, particularly, became the epicenter of the COVID-19 outbreak in the region during March and April 2020. In this context, the present study shows a simple mathematical approach to understand the effect of the COVID-19 outbreak in Ecuador (and some Latin American countries such as Brazil, Peru, and Colombia). The proposed method is based on the exponential model, discrete logistic equation, and differential logistic model using one-year data from March 1, 2020, to February 28, 2021. This study presents the estimated growth rate coefficient (λ), the total number of cases (N), and the midpoint of maximum infection (t_0) as well as the variability of the λ coefficient as a function of total cases and time. The exponential model shows a high value of λ=0.185 which decreases to λ=0.014 and λ=0.056 according to the discrete and differential logistic models, respectively. An accurate value of the total number of cases of infected people was found by analyzing the number of daily cases as a function of the total of cases whose value (N~409 K) agrees with the data reported at the end of May 2021, validating the proposed approach. How to use the current mathematical approach for long-term prediction is also discussed here. Most importantly, the proposed method has two important characteristics: (i) the mathematical model is as simple as possible compared to other time-consuming approaches, and (ii) it can be used to study the effect of COVID-19 and predicts its consequences in other countries, allowing revenue new decisions against the COVID-19 disease. Doi: 10.28991/esj-2021-SPER-09 Full Text: PDF

Output-Feedback Adaptive Control of Nonlinear Systems With Input–Output-Dependent Lower-Triangular Growth Rate: A Logic-Based Switching Approach

By incorporating a logic-based switching mechanism into high-gain linear controllers, global output-feedback adaptive stabilization is achieved for a class of nonlinear systems with unknown input–output-dependent lower-triangular growth rate and uncertain control coefficient. When a controller candidate, associated with a Lyapunov candidate, is connected into the closed-loop, the logic unit constantly supervises the change rate of the Lyapunov candidate. If it does not decrease as rapidly as predicted, another controller candidate will be switched in to replace the former one. It is theoretically proved that there is only a finite number of switching times, and asymptotic stability of the closed-loop system is guaranteed. Compared with existing results, the logic-based switching adaptive control approach can tolerate strong input–output-dependent nonlinearities, as well as large uncertainties from the system dynamics including the control coefficient. Finally, a numerical example is provided to illustrate the feasibility and the effectiveness of the proposed approaches.

First report on embryonic and larval development of 2n/3n mosaic sterlet

Mosaicism is frequently observed in aquaculture practices, and it adversely affects the production as well as the restoration programme of the sturgeon. The purpose of the present study was the induction of 2n/3n mosaic in sterlet, Acipenser ruthenus L., and compare their embryonic and larval development with diploid control sterlet. Microsatellite DNA loci genotyping was conducted for the identification of the genotypes and parentage analysis. Embryonic development was monitored in experimental groups at every 24 h interval. Identification of individual stages of embryonic development was recorded based on a 36-degree scale of development. Additionally, the BW and body length (LT) of experimental fishes were taken during 110 days of the rearing period. The Fulton’s condition coefficient (F), length-weight parameters, and specific growth rate (SGR) coefficient were calculated. The analysis of embryonic development of the 2n/3n mosaic and the diploid control group did not show differences. However, higher mortality (88%) was observed in 2n/3n mosaic groups in comparison to the diploid control groups (55%). BW and body length of 2n/3n mosaic sterlet were slightly lower than the diploid control sterlet, but the differences were not statistically significant. F analysis did not confirm a lower growth performance of the fishes in the 2n/3n mosaic group. Microsatellite DNA loci genotyping confirmed both the incidence of polyspermy and retention of the second polar body. This paper presents the first report on embryonic development and growth performance of 2n/3n mosaic sturgeons.

Maternal size on reproductive performance, egg and larval quality in the endangered Asian catfish, Clarias magur

The Asian catfish, Clarias magur, is an endangered fish species, which is immensely important due to its high commercial value in India and other South-East Asian countries. Various anthropogenic activities and natural habitat loss have greatly impacted the biodiversity of C. magur in natural water bodies, leading to the addition of this species to the endangered species list. The development of captive spawning and selection of an ideal broodstock size are critical steps to maximize the efficiency and robustness of conservation efforts for the catfish. An induced spawning experiment was conducted to ascertain the reproductive performance, egg and larval quality of catfish broodstock from fish with varying body weights. Five female C. magur broodfish from each of the following size ranges, F65 (65 ± 5.0); F130 (130 ± 7.9), F180 (180 ± 3.5) and F250 (253 ± 9.7g), were selected along with male broodfish with the same body weight range. The present study's results revealed that the stripping response was higher (F = 2.06; p = 0.15) for medium-sized F180 magur female broodstock; however, no significant differences were observed for this group. Total (F = 20.79; p < 0.001) and relative fecundity (F = 3.09; p = 0.057) were found to be significantly higher for F250 and F65 broodfish respectively. Total fecundity had a strong significant positive correlation (r = 0.99; p = 0.012) and also had significant linear regression relation (R2 = 0.98; p = 0.012) to maternal size. Hatching rate was observed to be significantly higher (F = 7.82; p = 0.002) for the medium-sized broodfish, F130. The medium-sized broodstock of 130–180 g had strong positive influence on the growth and survival of the progeny, while F250 broodfish produced poor-quality larvae, which resulted in reduced larval growth performance and survival. Specific growth rate (SGR) and thermal growth coefficient (TGC) were also found to be significantly higher for F130 female broodstock. Hence, the selection of medium-sized (130–180) or 1- to 2-year-old female broodstock had a significant effect on the reproductive performance, egg and larval quality of magur in captivity. The results from this study can be utilized as helpful and practical information enhancing selection protocols for the hatchery operators to select ideal broodstock based on size, enabling the production of viable egg and larvae in indoor conditions and a scalable seed production system.

Age, Growth, and Mortality of Atlantic Tripletail in the North‐Central Gulf of Mexico

AbstractIn the southeastern USA and the Gulf of Mexico (GOM), Atlantic Tripletail Lobotes surinamensis are increasingly targeted by recreational anglers, indicating that stock status should be assessed. A critical need for such assessments is age‐specific data; however, previous studies have drawn conflicting conclusions regarding the most appropriate structure for aging. Moreover, growth parameters and mortality rates for GOM Atlantic Tripletail are unknown. Therefore, the goals of this study were to (1) evaluate sagittal otoliths and first dorsal spines as aging structures; (2) model combined and sex‐specific growth; and (3) estimate mortality rates for GOM Atlantic Tripletail. From 2012 to 2019, Atlantic Tripletail (N = 230, including a near‐record‐size specimen) were collected from the north‐central GOM via hook and line and were aged using otoliths and first dorsal spines. Total length ranged from 212 to 940 mm, and age ranged from 0.07 to 5.27 years. Otoliths produced higher percent agreement (95.0%) and lower average percent error (3.0%) between readers compared to spines (82.9% and 6.5%, respectively). The von Bertalanffy growth parameters differed slightly between the otolith‐based data (mean asymptotic length [L∞] = 762.42 mm, Brody growth rate coefficient [k] = 0.69 year−1, and hypothetical age at which length equals zero [t0] = −0.58 year) and spine‐based data (L∞ = 718.83 mm, k = 0.79 year−1, and t0 = −0.56 year). For both otolith‐ and spine‐based sex‐specific data, the best‐fitting version of the von Bertalanffy growth function permitted L∞ to vary by sex. Chapman–Robson estimates of instantaneous total mortality rate and total annual mortality rate were 1.15 and 68.66%, respectively. Based on empirical, life history‐based methods, the instantaneous natural mortality rate was estimated at 0.75–0.97 and the instantaneous fishing mortality rate was estimated at 0.18–0.45, suggesting low levels of exploitation. These growth parameters and mortality estimates will provide information for future stock assessments, thereby ensuring sustainability of the GOM stock of Atlantic Tripletail.

Population dynamics of mantis shrimp (Gonodactylus chiragra Fabricius, 1781) in Batukalasi waters, South Sulawesi, Indonesia

The purpose of this research was to determine several population dynamics parameters of a mantis shrimp (Gonodactylus chiragra) population including growth, mortality, exploitation rate, and relative yield per recruit. Mantis shrimp were sampled from the waters around Batukalasi, South Sulawesi Indonesia from 16th June to 21st July 2019. Each specimen was measured, weighed and the sex determined. Growth parameters were estimated using the Von Bertalanffy equation. Natural mortality (M) was estimated using Pauly’s empirical equation. Total mortality (Z) was estimated using the Beverton and Holt equations. Fishing mortality was calculated from the equation Z = F + M. The exploitation level and relative yield per recruit were estimated using the Beverton and Holt equations. These analyses were conducted in the FAO-ICLARM Fish Stock Assessment Tools II (FISAT II) program. The 707 mantis shrimp samples were collected comprised of 245 females and 462 males. The growth rate coefficient was higher in male than female mantis shrimps, while male mantis shrimps reached their asymptotic length faster than females. For both male and female mantis shrimps, the estimated natural mortality was higher than fishing mortality, indicating the stock is not over-exploited. The relative yield per recruit was below the optimum value for both female and male mantis shrimp (0.035 and 0.046, respectively).

Performance of West African dwarf goats fed supplemented with Myrianthus arboreus leaf meal concentrates

A feeding trial was conducted to evaluate the performance of West African Dwarf goats fed Panicum maximum supplemented with Myrianthus arboreus leaf meal for 49 days. Four diets were formulated such that diet A contained 0.00% Myrianthus arboreus, diet B contained 10.00% Myrianthus arboreus, diet C contained 11.00% Myrianthus arboreus and diet D contained 12.00% Myrianthus arboreus respectively. A total of twelve (12) West African Dwarf goats were randomly allocated to the four diets with three animals per diet, each serving as a replicate. Parameters assessed were the chemical composition of the experimental diets, growth rate and digestibility coefficient of the animals. The results showed that diet D had the highest dry matter (92.55%) and crude protein (20.55%) contents. The average daily weight gain (g/day) of animals was significantly (P&lt;0.05) nfluenced across the treatments. Animals fed diet D recorded the highest weight gain (19.39g/day) while the least weight gain (7.55g/day) was recorded for animals on diet B. The highest total dry matter intake (340.34g/day) was recorded for animals on diet D while the least (313.18g/day) was observed in animals fed diet C. The best feed conversion ratio(17.55) was recorded in animals fed diet D. There were significant differences (P&lt;0.05) in the nutrient digestibility of the experimental animals. The highest dry matter (82.70%), crude protein (86.18%) digestibilities were observed in diet D while the least dry matter digestibility (72.73%) was observed in diet B. However, the least fibre fractions digestibilities were observed in diet D. It can therefore be concluded that supplementation of Myrianthus arboreus leaf meal concentrate at 12% inclusion with Panicum maximum as basal diet for goats can enhance nutrient digestibility and improve growth without any deleterious effects on the animals.

ANALISIS MORFOMETRIK UKURAN TUBUH KAMBING LOKAL UMUR PRA SAPIH YANG DI PELIHARA SECARA TRADISIONAL

This study aims to determine body size and body size of pre-age old goat breeds traditionally maintained in Kabila Bone District, Bone Bolango District and to find out the local goat maintenance system applied by farmers in Kabila Bone District, Bone Bolango District. The research material was local goat aged pre-age from 1 week to 10 weeks as many as 30 individuals. This study used a survey method. Retrieval of data by purposive sampling and sample determination by accidental sampling. The data obtained were analyzed by calculating the mean, standard deviation, coefficient of variation, regression equation, and growth rate between age and body size. Based on the statistical results, the average value obtained was 8.62 cm head length, 6.92 cm head width, 9.47 cm head height, 15.16 cm chest width, 19.94 cm chest inside, 34.25 cm shoulder height, chest circumference 33.49 cm, body length 34.36 cm, canon circumference 6.31 cm and body size increase between age and head length is 0.056 cm.

Dietary essential oil extract from sweet orange (Citrus sinensis) and bitter lemon (Citrus limon) peels improved Nile tilapia performance and health status

The effects of dietary essential oils extract from sweet orange (Citrus sinensis) (OEO) and/or lemon (Citrus limon) (LEO) peels on performance and health status of Nile tilapia were investigated. Seven triplicate groups (Control "CG", OEO1‰, OEO3‰, LEO0.75‰, LEO1‰, OEO1‰ × LEO0.75‰ and OEO3‰ × LEO1‰) of fish (16.42 ± 0.059 g, N = 210) were fed basal diet, basal diet contain OEO 1‰, OEO 3‰, LEO 0.75‰, LEO 1‰, OEO 1‰ × LEO 0.75‰ and OEO 3‰ × LEO1‰ respectively, for 60 day. Results showed significant improvement in growth (final weight, weight gain, specific growth rate and thermal growth coefficient), blood health (increased total protein, albumin, globulin and decreased aspartate aminotransferase, alanine aminotransferase, cholesterol, triglycerides and glucose), immune response (phagocytic activity, phagocytic index and lysozyme activity) and oxidative status (super oxide dismutase and catalase) of fish received OEO or/and LEO in respect to CG (p < 0.05) with the best findings observed in OEO 3‰ × LEO1‰. In a dose-dependent effect, liver insulin growth factor I (IGF-I), super oxide dismutase (SOD) and tumour necrosis factor-alpha (TNF-α) significantly upregulated in fish received OEO or/and LEO compared with CG (p < 0.05). Dietary supplementation of OEO or/and LEO significantly improved the intestinal morphometry (villi length, inter villi space and number of goblet cells) of fish compared to CG (p < 0.05) with the best results detected in OEO 3‰ × LEO1‰. Conclusively, OEO 3‰ × LEO1‰ have significant physiological, antioxidant and immunostimulant activities that could be used as natural constituents during the formulation of aquafeeds to improve fish welfare via dietary management.

Site exposure, substrate, depth, and the thermocline affect the growth of native unionid mussels in a stratified lake

The distribution of the native mussel Elliptio complanata (Lightfoot, 1786) in lakes is limited to nearshore areas above the thermocline. Their distribution appears to be constrained by wind-driven physical forces, and if so, we expect: 1) lower growth at the edges of their depth range, at shallow exposed sites, and at deep sites close to the thermocline; and 2) long-term changes in growth with lake warming and changing thermocline depth. This study compares the growth of juvenile and adult E. complanata over their depth range in a stratified lake and across sites with different exposures and sediment types. I used thin shell sections covering as long of a period as possible (7–54 y) to measure growth of 195 mussels. The average growth, measured as the von Bertalanffy growth rate coefficient, k, of juveniles ranged more than 3-fold (k = 0.06–0.27) around a single lake basin and that of adults 2-fold (0.3–0.6 mm/y). Mussel growth decreased with increasing depth and with increasing site exposure, but a positive relationship with sediment organic content suggests that sediments provide a refuge for adult mussels. Coherence between growth series was strongest at the deepest sites (6 m; expressed population signal = 0.82), where mussel growth responded to thermocline depth. Longer stratification periods and shallower thermoclines are expected to compress the range of these mussels in lakes and may similarly affect the wider littoral benthic communities.

Biodegradation of Phenol by Rhodococcus sp. Strain SKC: Characterization and Kinetics Study.

This study focuses on the kinetics of a pure strain of bacterium Rhodococcus sp. SKC, isolated from phenol-contaminated soil, for the biodegradation of phenol as its sole carbon and energy source in aqueous medium. The kinetics of phenol biodegradation including the lag phase, the maximum phenol degradation rate, maximum growth rate (Rm) and maximum yield coefficient (Y) for each Si (initial phenol concentration, mg/L) were fitted using the Gompertz and Haldane models of substrate inhibition (R2 > 0.9904, RMSE < 0.00925). The values of these parameters at optimum conditions were μmax = 0.30 h−1, Ks = 36.40 mg/L, and Ki = 418.79 mg/L, and that means the inhibition concentration of phenol was 418.79 mg/L. By comparing with other strains of bacteria, Rhodococcus sp. SKC exhibited a high yield factor and tolerance towards phenol. This study demonstrates the potential application of Rhodococcus sp. SKC for the bioremediation of phenol contaminate.

Nucleation and crystal growth kinetic parameter optimization of a continuous Poiseuille flow struvite crystallizer using a discretized population balance and dynamic fluid model

Struvite crystallization is an important process in recovering phosphorus from waste streams, but kinetic parameters involve significant uncertainty. In this research a model is developed which includes population balance, fluid flow equations, and kinetic relations. Power law rate coefficients for struvite nucleation (knuc=7.509×107L-1.min-1) and growth (kg=16.72μm.min-1) are optimised by combining a Poiseuille flow reactor model (PFR) and experimental data for phosphorus concentration and particle size distribution (PSD) at the reactor outlet. Nucleation and crystal growth rates were optimized using both filtered and sonicated PSD samples. The model incorporated three key aspects: non-ideal thermodynamics; Poiseuille fluid flow (including advection, diffusion and reaction); and a discretized population balance model (PBM). Sensitivity analysis using deltas (min/max) showed diffusion effects to be negligible and indicated that power law rate constants for both nucleation and growth were more influential on PSD and phosphorus concentration than the associated rate orders. Optimized parameters agreed reasonably well with a previous study conducted by our group under different conditions, using a different model, providing confidence in results. The optimized nucleation rate, knuc, was only 12% lower than that found using a similar model for a seeded system, where secondary nucleation is dominant. Additionally, a primary nucleation model provided a poor fit to experimental data. These two factors indicate that secondary nucleation is an influential mechanism. A 2nd order growth model provided a better fit to data than a previously suggested 5th order growth model. The optimized growth rate coefficient, kg, was higher than in any previous studies, an effect attributed to sonication, which eliminated aggregates.

Large Eddy Simulation of soot evolution in turbulent reacting flows: Strain-Sensitive Transport Approach for Polycyclic Aromatic Hydrocarbons

Polycyclic Aromatic Hydrocarbons (PAH) are confined to spatially intermittent regions of low scalar dissipation rates due to their slow formation chemistry. The length scales of these regions are on the order of the Kolmogorov scale or smaller, where molecular diffusion dominates over turbulent mixing irrespective of the large-scale turbulent Reynolds number. A strain-sensitivity parameter is proposed to identify such species. A Strain-Sensitive Transport Approach (SSTA) is then developed to model this differential transport in the nonpremixed flamelet equations. Specifically, the strain-sensitive species are modeled with their non-unity molecular effective Lewis numbers, while the remaining species are modeled with unity effective Lewis numbers. An a priori analysis of nonpremixed flamelet solutions reveals that the flame temperature and strain-insensitive species (e.g., major products of combustion, acetylene, etc.) profiles from the proposed SSTA closely match those from the unity effective Lewis number approach, but the mass fractions of strain-sensitive species (e.g., naphthalene) are significantly modified compared to the unity effective Lewis number approach and are consistent with Direct Numerical Simulation (DNS) data. This new SSTA model is implemented within a Large Eddy Simulation (LES) framework, applied to a series of laboratory-scale turbulent nonpremixed sooting jet flames, and validated via comparisons with experimental measurements of temperature and soot volume fraction. Both the unity effective Lewis number approach and SSTA model provide temperature predictions in good agreement with the experimental data, but the non-unity molecular effective Lewis number approach overpredicts the flame length. Compared to the unity effective Lewis number approach, the spatial distribution of soot volume fraction predicted by SSTA is in better agreement with the experimental measurements in terms of the upstream growth of the soot volume fraction and the location of its peak value along the centerline, both of which strongly depend on accurate predictions of the PAH mass fraction. The maximum soot volume fraction is minimally influenced and in good agreement with the experimental measurements. Finally, with this new SSTA model, the influence of global strain rate on turbulent nonpremixed sooting jet flames is analyzed to find that, even though PAH is inversely proportional to the global strain rate, the soot volume fraction may not be inversely proportional to the global strain rate due to an increase in the acetylene surface growth rate coefficient with global strain rate.

Coexistence and bistability of a competition model with mixed dispersal strategy

In this paper, we investigate a Lotka–Volterra competition model with Danckwerts boundary conditions in a one-dimensional habitat where one species assumes pure random diffusion while another one undergoes mixed movement (both random and directed movements). We focus on the joint influence of advection rate, intrinsic growth rate and interspecific competition coefficient on the competition outcomes. It turns out that there exist some critical curves which separate the stable region of the semitrivial steady states from the unstable one. The locations of these curves determine whether coexistence or bistability occurs. More precisely, there are various tradeoffs between advection rate, intrinsic growth rate and interspecific competition coefficient that allow the transition of competition outcomes including competition exclusion, coexistence and bistability. We illustrate our results in various parameter spaces.

Lipschitz stability for the growth rate coefficients in a nonlinear Fisher-KPP equation

<p style="text-indent:20px;">We consider a reaction-diffusion model of biological invasion in which the evolution of the population is governed by several parameters among them the intrinsic growth rate <inline-formula><tex-math id="M1">\begin{document}$ \mu(x) $\end{document}</tex-math></inline-formula>. The knowledge of this growth rate is essential to predict the evolution of the population, but it is a priori unknown for exotic invasive species. We prove uniqueness and unconditional Lipschitz stability for the corresponding inverse problem, taking advantage of the positivity of the solution inside the spatial domain and studying its behaviour near the boundary with maximum principles. Our results complement previous works by Cristofol and Roques [<xref ref-type="bibr" rid="b11">11</xref>,<xref ref-type="bibr" rid="b13">13</xref>].