Logistic Growth Rate Research Articles

Postnatal Growth Rates of Hummingbirds: Review and New Records

We review the published information on postnatal growth rates of hummingbirds (13 species), and report previously unpublished records for nine additional trochilid species. The allometric relationship based on the log10-transformed data of K (logistic growth rate constant) and body mass has a slope of −0.313 and an intercept of −0.346 (n = 22; r2 = 0.18; P = 0.049). The allometric relationship has a slope of −0.366 and an intercept of −0.327 (n = 20; r2 = 0.30; P = 0.013) if the two Nearctic records are excluded. Visual inspection suggests that higher K-values occur in Nearctic hummingbirds (x̄ = 0.422; n = 2) compared to Neotropic species (x̄ = 0.269; n = 20). We suggest a revival of studies collecting basic life history information such as postnatal growth rates of birds, especially of tropical taxa.

Global solution for a chemotactic–haptotactic model of cancer invasion

This paper deals with a mathematical model of cancer invasion of tissue recently proposed by Chaplain and Lolas. The model consists of a reaction–diffusion-taxis partial differential equation (PDE) describing the evolution of tumour cell density, a reaction–diffusion PDE governing the evolution of the proteolytic enzyme concentration and an ordinary differential equation modelling the proteolysis of the extracellular matrix (ECM). In addition to random motion, the tumour cells are directed not only by haptotaxis (cellular locomotion directed in response to a concentration gradient of adhesive molecules along the ECM) but also by chemotaxis (cellular locomotion directed in response to a concentration gradient of the diffusible proteolytic enzyme). In one space dimension, the global existence and uniqueness of a classical solution to this combined chemotactic–haptotactic model is proved for any chemotactic coefficient χ > 0. In two and three space dimensions, the global existence is proved for small χ/μ (where μ is the logistic growth rate of the tumour cells). The fundamental point of proof is to raise the regularity of a solution from L1 to Lp (p > 1). Furthermore, the existence of blow-up solutions to a sub-model in two space dimensions for large χ shows, to some extent, that the condition that χ/μ is small is necessary for the global existence of a solution to the full model.

Approximating the ideal free distribution via reaction–diffusion–advection equations

We consider reaction–diffusion–advection models for spatially distributed populations that have a tendency to disperse up the gradient of fitness, where fitness is defined as a logistic local population growth rate. We show that in temporally constant but spatially varying environments such populations have equilibrium distributions that can approximate those that would be predicted by a version of the ideal free distribution incorporating population dynamics. The modeling approach shows that a dispersal mechanism based on local information about the environment and population density can approximate the ideal free distribution. The analysis suggests that such a dispersal mechanism may sometimes be advantageous because it allows populations to approximately track resource availability. The models are quasilinear parabolic equations with nonlinear boundary conditions.

Models of population dynamics (abstract only)

This project explains the mathematical equations used to approximate species populations. The equations used are the exponential growth rate, logistic growth rate, and the predator-prey systems. The purpose is to show how the equations are taken from simple mathematical principles and assumptions. Basic techniques in Calculus and Linear Algebra are used to analyze the quantitative properties of solutions to the differential equation models.

The role of PGP9.5 as a tumor suppressor gene in human cancer

PGP9.5 is a controversial molecule from an oncologic point of view. We recently identified frequent methylation of PGP9.5 gene exclusively in primary head and neck squamous cell carcinoma (HNSCC), suggesting that it could be a tumor suppressor gene. On the other hand, PGP9.5 was reported to be overexpressed in a subset of human cancers presumably due to intrinsic oncogenic properties or as a result of transformation. To demonstrate that PGP9.5 possesses tumor suppressive activity, we examined forced expression by stable transfection of PGP9.5 in 4 HNSCC cell lines. Although all 4 cell lines demonstrated reduced log growth rates in culture after transfection, only 2 cell lines with wild type p53 (011, 022) demonstrated decreased growth in soft agar. In 2 cell lines with mutant p53 (013, 019), we observed no altered growth in soft agar and increased sensitivity to UV irradiation. We then tested for and found a high frequency of promoter methylation in a larger panel of primary tumors including HNSCC, esophageal SCC, gastric, lung, prostate and hepatocellular carcinoma. Our data support the notion that PGP9.5 is a tumor suppressor gene that is inactivated by promoter methylation or gene deletion in several types of human cancers.

ANGLER NUMERICAL RESPONSE ACROSS LANDSCAPES AND THE COLLAPSE OF FRESHWATER FISHERIES

Recreational angling opportunities in lakes are distributed across landscapes and attract anglers based on the combination of angling quality, travel distance, and availability of facilities. The relationship between angler density and fishing quality, as measured by catch rate, represents a numerical response that is analogous to a predator numerical response to variability in prey abundance. We quantified this numerical response of anglers to rainbow trout, Oncorhynchus mykiss, populations distributed over a large lake district in south-central British Columbia, Canada. We developed a harvest dynamics model by linking this empirical description of the spatial numerical response of anglers to a logistic population growth rate model. The model was parameterized for rainbow trout and simulated spatial patterns of angler density and catch rates over a landscape. At locations distant from urban centers, angler density is low and catch rate high, suggesting near pristine conditions; at intermediate distances angler density is higher while catch rates are lower and approximate maximum sustainable levels; and at short distances angler density is sufficiently high to harvest to local extirpation. We extrapolated the model to other lake districts varying in human population size using an empirically derived angling participation rate relationship. Extrapolation to lake districts with one-tenth the human population maintained viable fisheries close to the urban area, and districts with 10 times the human populations could not maintain viable fisheries across much of their lake district. Landscape-scale spatial patterns differed quantitatively for species varying in rates of intrinsic population growth and carrying capacity, but the qualitative spatial patterns were consistent among species, demonstrating the pervasive impacts of the angler numerical response. To achieve a management goal of sustaining fisheries across landscapes, a change in management perspective is necessary, from that of individual lakes to one of dynamic harvest processes across landscapes. This new approach makes it clear that a one-size-fits-all management approach must be replaced with a mosaic of approaches cognizant of landscape-scale processes.

Nonstandard finite-difference methods for predator–prey models with general functional response

Predator–prey systems with linear and logistic intrinsic growth rate of the prey are analyzed. The models incorporate the mutual interference between predators into the functional response which stabilizes predator–prey interactions in the system. Positive and elementary stable nonstandard (PESN) finite-difference methods, having the same qualitative features as the corresponding continuous predator–prey models, are formulated and analyzed. The proposed numerical techniques are based on a nonlocal modeling of the growth-rate function and a nonstandard discretization of the time derivative. This discretization approach leads to significant qualitative improvements in the behavior of the numerical solution. In addition, it allows for the use of an essentially implicit method for the cost of an explicit method. Applications of the PESN methods to specific predator–prey systems are also presented.

A regulated transitive reduction (RTR) for longer memory race recording

Now at VMware. Multithreaded deterministic replay has important applications in cyclic debugging, fault tolerance and intrusion analysis. Memory race recording is a key technology for multithreaded deterministic replay. In this paper, we considerably improve our previous always-on Flight Data Recorder (FDR) in four ways: •Longer recording by reducing the log size growth rate to approximately one byte per thousand dynamic instructions. •Lower hardware cost by reducing the cost to 24 KB per processor core. •Simpler design by modifying only the cache coherence protocol, but not the cache. •Broader applicability by supporting both Sequential Consistency (SC) and Total Store Order (TSO) memory consistency models (existing recorders support only SC).These improvements stem from several ideas: (1) a Regulated Transitive Reduction (RTR) recording algorithm that creates stricter and vectorizable dependencies to reduce the log growth rate; (2) a Set/LRU timestamp approximation method that better approximates timestamps of uncached memory locations to reduce the hardware cost; (3) an order-value-hybrid recording methodthat explicitly logs the value of potential SC-violating load instructions to support multiprocessor systems with TSO.

A regulated transitive reduction (RTR) for longer memory race recording

Now at VMware. Multithreaded deterministic replay has important applications in cyclic debugging, fault tolerance and intrusion analysis. Memory race recording is a key technology for multithreaded deterministic replay. In this paper, we considerably improve our previous always-on Flight Data Recorder (FDR) in four ways: •Longer recording by reducing the log size growth rate to approximately one byte per thousand dynamic instructions. •Lower hardware cost by reducing the cost to 24 KB per processor core. •Simpler design by modifying only the cache coherence protocol, but not the cache. •Broader applicability by supporting both Sequential Consistency (SC) and Total Store Order (TSO) memory consistency models (existing recorders support only SC).These improvements stem from several ideas: (1) a Regulated Transitive Reduction (RTR) recording algorithm that creates stricter and vectorizable dependencies to reduce the log growth rate; (2) a Set/LRU timestamp approximation method that better approximates timestamps of uncached memory locations to reduce the hardware cost; (3) an order-value-hybrid recording methodthat explicitly logs the value of potential SC-violating load instructions to support multiprocessor systems with TSO.

A regulated transitive reduction (RTR) for longer memory race recording

Now at VMware. Multithreaded deterministic replay has important applications in cyclic debugging, fault tolerance and intrusion analysis. Memory race recording is a key technology for multithreaded deterministic replay. In this paper, we considerably improve our previous always-on Flight Data Recorder (FDR) in four ways: •Longer recording by reducing the log size growth rate to approximately one byte per thousand dynamic instructions. •Lower hardware cost by reducing the cost to 24 KB per processor core. •Simpler design by modifying only the cache coherence protocol, but not the cache. •Broader applicability by supporting both Sequential Consistency (SC) and Total Store Order (TSO) memory consistency models (existing recorders support only SC).These improvements stem from several ideas: (1) a Regulated Transitive Reduction (RTR) recording algorithm that creates stricter and vectorizable dependencies to reduce the log growth rate; (2) a Set/LRU timestamp approximation method that better approximates timestamps of uncached memory locations to reduce the hardware cost; (3) an order-value-hybrid recording methodthat explicitly logs the value of potential SC-violating load instructions to support multiprocessor systems with TSO.

On the pH and Osmotic Stress Tolerance of High Ethanol Tolerant Palm Wine <i>Saccharomyces</i> Yeast Isolates

Saccharomyces yeast strains Y13, Y522 and Y1189 isolated from fermenting palm wine juice showed marked differences in their optimum growth pH and possessed osmotolerance comparable to established industrial yeast strains. Shifts in medium pH beyond the growth optimum elicited obvious reductions in growth rate as depicted by the decrease in mean log growth rate (K) and influenced the response of the test yeasts to osmotic stress. Key Words: Osmotolerance, Ethanol tolerance, Osmotic stress, Saccharomyces Bio-Research Vol.2(1) 2004: 1-7

SYNTHESIS OF SURVIVAL RATES AND CAUSES OF MORTALITY IN NORTH AMERICAN WOLVERINES

Abstract Understanding population vital rates is fundamental to the evaluation of conservation options for wolverines (Gulo gulo). We estimated survival rates and causes of wolverine mortality in trapped and untrapped populations within montane, boreal, and tundra environments using data from 12 North American radiotelemetry studies conducted between 1972 and 2001. Rates were based on data for 62 mortalities of 239 radiomarked wolverines. Mortalities included 22 wolverines that were trapped or hunted, 3 road or rail killed, 11 that were predated, 18 that starved, and 8 deaths of unknown cause. Annual survivorship rates were estimated for sex and age class using Kaplan-Meier staggered-entry techniques. Survival was substantially lower in trapped ( 0.84 for all age–sex classes) populations. Human-caused mortality was mostly additive to natural mortality for wolverines in a management context. Logistic growth rate estimates indicated that trapped populations ...

ENERGETICS OF ALTRICIAL NESTLINGS IN COLD CLIMATES: INSIGHTS FROM THE MOUNTAIN WHITE-CROWNED SPARROW

Abstract We determined the energy budget of nestling Mountain White-crowned Sparrows (Zonotrichia leucophrys oriantha) at a 2900-m-high subalpine site by combining growth data with measurements of field metabolic rate (doubly labeled water technique) and resting metabolic rate made on different-aged nestlings. Nestling sparrows grow rapidly (their logistic growth rate constant is 129% of the allometric prediction) and they fledge at 9 days of age weighing 20.6 g (75% of adult mass). Relatively rapid growth in a cool montane environment (mean daytime air temperature = 16.5 ± 1.4°C) is associated with high daily and total nestling energy requirements. During the 9 days between hatching and fledging, each nestling metabolized a total of 443 kJ of energy; a value 25% higher than expected for an open-nesting passerine bird. The relative cost of producing a fledgling White-crowned Sparrow (21.5 kJ per g body mass) exceeds that of the three other open-nesting passerine species that have been measured with doubly...

Growth Characteristics of Artificially Reared Sika Deer (Cervus nippon)

Body weights of 21 artificially reared sika deer (Cervus nippon), including 10 males and 11 females, were measured from birth until 24-36 months of age, and the data were analyzed. The increases in body weights of the males and females from birth to 3 months of age were almost the same. However, the rate of increase in body weights of males became greater than that of females after 4 months of age, and this difference became greater with the advance of age. The rate of increase in body weights of females, but not of males, became asymptotic after 30 months of age. A significant inter-family difference was found in body weights of the deer from 4 to 12 months of age, suggesting the influence of genetic factors on growth rate. Significant differences between sexes, but not between families were found in rate of maturing, body weight at the inflection point on the logistic growth curve and growth rate. The inflection points on the logistic growth curves for males and females, which were thought to indicate the onset of puberty, were 8.5 and 7.3 months of age, respectively.

Reconciling Classical and Individual‐Based Approaches in Theoretical Population Ecology: A Protocol for Extracting Population Parameters from Individual‐Based Models

The two main approaches in theoretical population ecology-the classical approach using differential equations and the approach using individual-based modeling-seem to be incompatible. Linked to these two approaches are two different timescales: population dynamics and behavior or physiology. Thus, the question of the relationship between classical and individual-based approaches is related to the question of the mutual relationship between processes on the population and the behavioral timescales. We present a simple protocol that allows the two different approaches to be reconciled by making explicit use of the fact that processes operating on two different timescales can be treated separately. Using an individual-based model of nomadic birds as an example, we extract the population growth rate by deactivating all demographic processes-in other words, the individuals behave but do not age, die, or reproduce. The growth rate closely matches the logistic growth rate for a wide range of parameters. The implications of this result and the conditions for applying the protocol to other individual-based models are discussed. Since in physics the technique of separating timescales is linked to some concepts of self-organization, we believe that the protocol will also help to develop concepts of self-organization in ecology.

Reconciling Classical and Individual-Based Approaches in Theoretical Population Ecology: A Protocol for Extracting Population Parameters from Individual-Based Models

The two main approaches in theoretical population ecology—the classical approach using differential equations and the approach using individual‐based modeling—seem to be incompatible. Linked to these two approaches are two different timescales: population dynamics and behavior or physiology. Thus, the question of the relationship between classical and individual‐based approaches is related to the question of the mutual relationship between processes on the population and the behavioral timescales. We present a simple protocol that allows the two different approaches to be reconciled by making explicit use of the fact that processes operating on two different timescales can be treated separately. Using an individual‐based model of nomadic populabirds as an example, we extract the population growth rate by deactivating all demographic processes—in other words, the individuals behave but do not age, die, or reproduce. The growth rate closely matches the logistic growth rate for a wide range of parameters. The implications of this result and the conditions for applying the protocol to other individual‐based models are discussed. Since in physics the technique of separating timescales is linked to some concepts of self‐organization, we believe that the protocol will also help to develop concepts of self‐organization in ecology.

Permanence of a nonautomonous population model

A nonautomonous predator-prey system is studied in this paper. A logistic growth rate of the prey and a functional response of the predator are assumed. Throughout this paper, the main interest is in the results yielding the threshold between the weak permanence in the mean and the extinction of populations.

Implications of thallus thickness for growth-irradiance relationships of marine macroalgae

We have tested the importance of thallus thickness in marine macroalgae for the growth-irradiance relationship measured in the laboratory and for the maximum growth rate measured in the field. We found large differences in the growth-irradiance relationship depending on the biomass parameter (surface area, fresh weight, carbon content) applied. Use of carbon content yielded meaningful reproducible patterns and it appeared to be the most suitable descriptor of plant energetics. Surface area and fresh weight increased in the dark despite loss of carbon in the plant tissue. The growth kinetic parameters were closely related to thallus thickness, here described as thallus-specific carbon (TSC, mol tissue C m−2 surface area). Both the loss rates in the dark and the growth rates in carbon biomass at low and high irradiance decreased with increasing TSC of the species. The decline in growth rate with increasing TSC was described by the allometric equation log(growth rate) = a + b × log(TSC). The slope, b, was between −0·50 and −0·52 in field data derived from 30–34 species of macroalgae. In similar descriptions of maximum photosynthesis at high light (as a function of TSC) derived from the literature, b was between −0·47 and −0·80. The relationships between growth and TSC and photosynthesis and TSC were, however, weak for thin species, and thus resemble the weaker size dependence of growth previously described for unicellular algae. TSC is recommended as a suitable continuous variable to describe the relationship between thallus form and growth and metabolism in marine macroalgae which can be extended to microalgae.

Growth and Energy Requirements of Hand-Reared Great Blue Heron (Ardea herodias) Chicks

The energy requirements of 12 hand-reared Great Blue Heron (Ardea herodias) chicks were determined using a continuous feeding trial. Male (n = 8) and female (n = 4) chicks did not differ in their hatching mass, but by day 30 the mass of male chicks was significantly greater than the mass of female chicks. At fledging, male chicks (x = 2,465 + SE of 51 g) were about 13% heavier than female chicks (2, 179 ? 10 g). The growth rate of male chicks (logistic growth rate (k) of 0.167 ? 0.004/day and absolute growth rate (AGR) of 70.7 ? 4.1 g/day) was significantly different from the growth rate of female chicks (k of 0.178 ? 0.003 /day, and AGR of 60.5 ? 0.4 g/day). Metabolizable energy intake (ElME) and energy requirements did not differ between male and female chicks. El,, was maximal between days 26 and 41 at 2,027 ? 25 kJ/day. The total energy requirement for gain (kJ/day) was greatest between 10 and 29 days of age, the time of maximum growth. The total energy requirement for maintenance (kJ/day) was greatest between 30 and 39 days of age. Our study provides evidence to support the hypothesis that reproductive success of Great Blue Herons is limited by the parents' ability to gather food. Brood size at fledging predicted by the relationship between parental effort and the chicks' energy requirements is similar to the observed number of young fledged per successful nest. Peak mortality of wild nestlings occurs during the time of peak chick energy requirements as indicated by our study. Received 7 June 1993, accepted

Studies on tetragonal lysozyme crystal growth rates.

A computer-controlled apparatus able to simultaneously follow the face growth rate of up to 40 crystals was developed. This apparatus was used to investigate the effects of solution pH on the (110) and (101) face growth rates of tetragonal lysozyme. Growth rates were measured at pH 4.0, 4.4, 4.8 and 5.2, in 0.1 M sodium acetate buffer with 5% NaCl, 295 K. Initial crystal sizes ranged from 10 to 40 microm. Plots of log supersaturation ratio (either C/C(sat) or C/C(sat) - 1) versus log(growth rate) are not linear, typically having a slope of approximately 8 at the lowest growth rates determined (10(-6) microm s(-1)), which falls off to a slope of approximately 2 at the highest growth rates (10(-2) microm s(-1)) measured. Ratios of C/C(sat) ranged from 4 to >20. The data show that lower solubility solutions require higher supersaturation ratios for equivalent growth rates. Data for the growth rate of the (101) face at pH 4.0 were widely scattered, especially at lower supersaturation ratios. Time-lapse video of crystals at low supersaturations shows that initially only the (110) faces grow, leaving 'notches' at the (110)-(110) corners. These corners then fill in and macro-steps appear on the (101) faces which rapidly move inward in the form of an octagon, restoring the crystal to a 'normal' appearance. This phenomenon has been observed for tetragonal crystals grown in either still or flowing solutions. Flowing solutions at lower supersaturations also gave cases where the corners did not fill in, with the (110) faces continuing to grow out until growth ceased.