Subsequent Growth Rate Research Articles

Temporal correlations in population trends: Conservation implications from time-series analysis of diverse animal taxa

Population trends play a large role in species risk assessments and conservation planning, and species are often considered threatened if their recent rate of decline meets certain thresholds, regardless how large the population is. But how reliable an indicator of extinction risk is a single estimate of population trend? Given the integral role this decline-based approach has played in setting conservation priorities, it is surprising that it has undergone little empirical scrutiny. We compile an extensive global dataset of time series of abundance data for over 1300 vertebrate populations to provide the first major test of the predictability of population growth rates in nature. We divided each time series into assessment and response periods and examined the correlation between growth rates in the two time periods. In birds, population declines tended to be followed by further declines, but mammals, salmon, and other bony fishes showed the opposite pattern: past declines were associated with subsequent population increases, and vice versa. Furthermore, in these taxa subsequent growth rates were higher when initial declines were more severe. These patterns agreed with data simulated under a null model for a dynamically stable population experiencing density dependence. However, this type of result could also occur if conservation actions positively affected the population following initial declines—a scenario that our data were too limited to rigorously evaluate. This ambiguity emphasizes the importance of understanding the underlying causes of population trajectories in drawing inferences about rates of decline in abundance.

Inoculum optimization of Clostridium beijerinckii for reproducible growth.

Spore-forming solventogenic Clostridium spp. are receiving renewed attention due to their butanol production abilities. However, there is an absence of literature describing the preparation of dense, vigorous and homogeneous seed cultures of Clostridium spp., guaranteeing reproducibility during fermentation. Therefore, we performed a series of growth experiments of Clostridium beijerinckii NCIMB 8052 and its offspring SA-1 to evaluate the influence of inoculum age (harvest time) on the subsequent population's maximum specific growth rate, as a signal of population homogeneity. The organisms were cultivated in Reinforced Clostridial Medium and supplemented sweet sorghum juice. The best inoculum ages coincided with the late-exponential growth phase: between 9 and 11 h in the conditions tested. Additionally, the harvest time was delayed up to 4 h by pre-adapting the seed culture with 0.75 g L(-1) butyric acid. These findings were validated by performing a series of bench-top batch fermentations showcasing reproducibility in growth kinetics with 95% confidence limits. Overall, these experiments allowed us to understand the transient nature of seed cultures of C. beijerinckii NCIMB 8052 and SA-1, while enabling reproducibility and consistent culture performance.

Relationships between day one piglet serum immunoglobulin immunocrit and subsequent growth, puberty attainment, litter size, and lactation performance.

Colostrum affects gut and uterine gland development in the neonatal piglet, suggesting that subsequent growth and reproductive performance may be affected. Measuring immunoglobulin in piglet serum using the immunoglobulin immunocrit on Day 1 of age provides a simple, inexpensive indication of the amount of colostrum acquired by the piglet in the first day of life. Relationships between serum immunoglobulin immunocrit measures and subsequent growth rates, age at puberty, incidence of puberty failure, litter size, and lactation performance were examined in pigs born and subsequently farrowing between 2009 and 2013. Immunoglobulin immunocrit measures were collected on 16,762 piglets on Day 1 of age. Of these piglets, BW measurements were available from 15,324 (7,684 males and 7,640 females) piglets at a range of ages from weaning to 200 d of age, allowing an assessment of growth rates. Age at puberty was recorded from a subset of 2,857 of the females after observing them for estrous behavior from approximately 170 to 250 d of age. To examine relationships between d 1 immunocrit and puberty failure, gilts with immunocrit measures that failed to reach puberty (n = 119) were matched with littermate gilts with immunocrit measures that achieved puberty (n = 167). Similarly, number born alive was collected on a subset (n = 799) of females from first to fourth parities for which d 1 immunocrits were measured on them as neonates. Finally, d 1 immunocrit effect on adult lactational competence was assessed by measuring litter average (offspring of 440 females) and litter average piglet preweaning growth rate (offspring of 774 females) in females where d 1 immunocrits were available from them as neonates. Results indicated that low d 1 immunocrits were subsequently associated with reduced growth (P < 0.01), increased age at puberty (P < 0.01), reduced number born alive (P < 0.05), reduced litter average immunocrit (P < 0.05), and reduced litter average preweaning growth rate during lactation (P < 0.05). This suggests that management efforts to improve the amount of colostrum ingested by neonatal piglets would result in beneficial changes in production efficiency, particularly for gilts destined for the breeding herd. It also suggests that the immunoglobulin immunocrit can be useful in monitoring colostrum ingestion to maximize the beneficial effects of colostrum on subsequent performance.

The Rise in Life Expectancy and Economic Growth in the 20th Century

This research exploits conditional exogenous variation in mortality from the diffusion of modern medicine to study the effect of growth in life expectancy on the growth in GDP per capita. The empirical analysis establishes that countries that obtained higher growth rates of life expectancy due to this shock to mortality in the mid-twentieth century experienced lower growth rates of GDP per capita in the second half of the twentieth century. In addition, a negative relationship between initial level of life expectancy and the subsequent growth rate of GDP per capita is found.

Effects of Folic Acid Deficiency on the Murine Mammary Gland

The epithelial ducts within the mammary glands (MG) undergo phases of isometric and allometric growth during early, postnatal life. Breast cancer is suggested to have origins in early life, a period during which folate requirements are high. We investigated the effects of folic acid (FA) on early MG development. Dams were assigned to either a control (2 mg FA/kg), deficient (0 mg FA/kg), excess (5 mg FA/kg), or super excess (20 mg FA/kg) amino acid defined diet and offspring continued to receive the same diet as their respective dams through postnatal and pubertal development. MG tissues from offspring were assessed at weaning and in early puberty. We observed no significant effects of excess or super excess FA diets on the MG. The area occupied by the mammary ducts at weaning and during early puberty was reduced in FA deficient animals compared with controls (p&lt;0.0001). The rate of MG growth in the isometric phase, from birth to weaning, was less for the MG of deficient females compared with those from controls (slope 95% confidence limits 0.23‐0.78 versus 1.47‐1.82, respectively). The subsequent rate of allometric growth was unaffected by diet. The supramammary lymph nodes in deficient animals were smaller than in control animals alongside a reduction in the area of the thymic medulla. Epigenetic and local expression analysis of signaling and growth factors in the MG are ongoing. We conclude that dietary FA deficiency alters normal development of the epithelial ducts and lymph node in the MG of prepubertal female mice. Funding source: CA Breast Cancer Research Program Grant #18IB‐000

The Influence of Reading on Vocabulary Growth: A Case for a Matthew Effect.

Individual differences in vocabulary development may affect academic or social opportunities. It has been proposed that individual differences in word reading could affect the rate of vocabulary growth, mediated by the amount of reading experience, a process referred to as a Matthew effect (Stanovich, 1986). In the current study, assessments of written word-reading skills in the 4th grade and oral vocabulary knowledge collected in kindergarten and in the 4th, 8th, and 10th grades from a large epidemiologically based sample (n = 485) allowed a test of the relationship of early word-reading skills and the subsequent rate of vocabulary growth. Consistent with the hypothesis, multilevel modeling revealed the rate of vocabulary growth after the 4th grade to be significantly related to 4th-grade word reading after controlling for kindergarten vocabulary level, that is, above average readers experienced a higher rate of vocabulary growth than did average readers. Vocabulary growth rate differences accumulated over time such that the effect on vocabulary size was large.

Self-employment and job generation in metropolitan areas, 1969–2009

Many regional development policy initiatives assume that entrepreneurial activities promote economic growth. Empirical research has presented rationale for this argument showing that small firms create proportionally more new jobs than large firms. However, little research has been performed on the issue of net job generation at the urban level, particularly when self-employment is considered as an indicator of entrepreneurial activities. This paper investigates to what extent US metropolitan areas in the 1969–2009 period characterized by relatively high rates of self-employment also have shown relatively high rates of subsequent total employment growth. The analysis corrects for the influence of sectoral composition, wage level, educational attainment, presence of research universities and size of the metropolitan area to measure the extent to which the number and quality of self-employed in a region contribute to total employment growth. It finds the relationship between self-employment rates and subsequent total employment growth to be positive on average during the 40-year period but to weaken over time.

Public Debt and Economic Growth in Emerging Market Economies

AbstractThis paper empirically studies the relationship between public debt and economic growth for selected emerging market economies by performing panel data estimations. The results reveal a statistically significant positive correlation between public debt and the subsequent growth rate of per capita gross domestic product (GDP). Population and investment are also positively correlated with per capita growth, whereas the initial level of real GDP per capita exerts a negative influence on growth, implying conditional convergence. Other variables such as the inflation rate, the trade balance or the exchange rate do not yield a statistically significant effect with respect to economic growth.

Predicting early life connectivity of Antarctic silverfish, an important forage species along the Antarctic Peninsula

The early life stages of the Antarctic silverfish (Pleuragramma antarctica), an important prey species for higher predators in the Southern Ocean ecosystem, dominate the larval fish assemblages of the Bransfield Strait, one of the most important areas for larval retention off the Antarctic Peninsula. Nevertheless, the spatial location of areas where they were spawned and the timing of larval hatching remain unknown. By linking Lagrangian particle tracking simulations with age data obtained using otolith microincrements from fish caught north of Joinville Island in a pelagic survey, we estimated the distribution of hatch dates and subsequent growth rates of silverfish reaching the Bransfield Strait, and predicted the areas where they were spawned. Larval hatching peaked during the last week of December, and the inner shelf and shelf break, east of the Larsen Ice shelf, were the dominant areas predicted to contribute to larval assemblages in the Bransfield Strait. Over simulated periods of 600–630 days, 35–40% of particles remained within the Bransfield Strait, suggesting an important source of supply to higher predators feeding off the northern Antarctic Peninsula. The daily growth rate at the mean size of 22.3 mm was 0.18 mm, corresponding to a daily change in size of approximately 0.82% standard length (SL), and large variability in growth rate suggested a wide range of environmental conditions experienced during the period of advection from the spawning areas. These results provide spatial predictions that can be tested empirically in future studies, using the simulated trajectories to inform sampling design and spatial coverage.

Genetically Determined Variation in Developmental Physiology of Bivalve Larvae (Crassostrea gigas).

Understanding the complex interactions that regulate growth and form is a central question in developmental physiology. We used experimental crosses of pedigreed lines of the Pacific oyster, Crassostrea gigas, to investigate genetically determined variations in larval growth and nutrient transport. We show that (i) transport rates at 10 and 100 μM glycine scale differentially with size; (ii) size-specific maximum transport capacity (Jmax) is genetically determined; and (iii) Jmax serves as an early predictive index of subsequent growth rate. This relationship between genetically determined Jmax and growth suggests the potential use of transporter genes as biomarkers of growth potential. Analysis of the genome of C. gigas revealed 23 putative amino acid transporter genes. The complexity of gene families that underpin physiological traits has additional precedents in this species and others and warrants caution in the use of gene expression as a biomarker for physiological state. Direct in vivo measurements of physiological processes using species with defined genotypes are required to understand genetically determined variance of nutrient flux and other processes that regulate development and growth.

Winter – the optimal logging season to sustain growth and performance of retained epiphytic lichens in boreal forests

Epiphytic lichens, comprising an important biodiversity component with significant functions in old boreal forests, are susceptible to logging. Leaving retention trees may partly compensate for the adverse effects of logging, but the impact of logging season on retained lichens is unknown. To identify the least harmful logging season seen from an epiphytic lichen perspective, we simulated logging events by transplanting two old forest model species – Lobaria pulmonaria (cephalolichen) and Lobariascrobiculata (cyanolichen) – in summer, autumn, winter and spring, respectively. Lichens were collected in intact old forests and transplanted in clear-cuts. They were placed on five aspects (N, E, S, W, and top) on artificial stands covered with bark. They all gained biomass and area in the following year. However, logging in January resulted in subsequent higher relative growth rates than in lichens being exposed to clear cuts in other seasons, consistent with clear seasonal logging effects. Aspect impacted lichen growth less than logging season, despite significant bleaching and chlorophyll contents in the most exposed aspects. The high annual growth rate and the low level of damage after transplantation to clear cuts during winter suggest that green tree retention (GTR) logging practices in winter can support life-boating of susceptible old forest lichen epiphytes. Logging simulation during other seasons than winter resulted in lower growth, implying higher risk of permanent damage. Successful use of GTR cannot compensate for the loss of epiphytes at timber harvest, but supports local retained lichen populations that subsequently may boost re-colonization of the young stand.

USING SIMULATION TO SUPPORT THE R&amp;D DECISION OF A PHARMACEUTICAL FIRM

This paper illustrates how simulation modeling can be employed to support the R&D decision of a pharmaceutical firm. We do this in the context of a simplified but realistic example, where a drug company has just successfully completed the second phase of a three-phase process for assessing the effectiveness of a proposed drug in treating a targeted ailment with acceptable levels of side-effects. We provide step-by-step instruction for simulating the net present value and the internal rate of return of a ten-year pharmaceutical R&D project. The uncertainty lies in the efficacy of proposed drug and that of an alternative drug. Random too, are the initial size of the total market, and its subsequent exponential growth rate. Market share depends on the efficacy of proposed drug relative to that of the alternative drug, as well as, the subsequent introduction of new, alternative drugs in the market, which arrive in a random fashion. Finally, the ratio of cost of goods sold to sales and the terminal EBITDA multiple are also random. The problem is a variation of the Newdrug examples in chapters 19-21 of Andrew Metrick and Ayako Yasuda’s (2010) venture capital finance text.

The effects of vaccination and immunity on bacterial infection dynamics in vivo.

Salmonella enterica infections are a significant global health issue, and development of vaccines against these bacteria requires an improved understanding of how vaccination affects the growth and spread of the bacteria within the host. We have combined in vivo tracking of molecularly tagged bacterial subpopulations with mathematical modelling to gain a novel insight into how different classes of vaccines and branches of the immune response protect against secondary Salmonella enterica infections of the mouse. We have found that a live Salmonella vaccine significantly reduced bacteraemia during a secondary challenge and restrained inter-organ spread of the bacteria in the systemic organs. Further, fitting mechanistic models to the data indicated that live vaccine immunisation enhanced both the bacterial killing in the very early stages of the infection and bacteriostatic control over the first day post-challenge. T-cell immunity induced by this vaccine is not necessary for the enhanced bacteriostasis but is required for subsequent bactericidal clearance of Salmonella in the blood and tissues. Conversely, a non-living vaccine while able to enhance initial blood clearance and killing of virulent secondary challenge bacteria, was unable to alter the subsequent bacterial growth rate in the systemic organs, did not prevent the resurgence of extensive bacteraemia and failed to control the spread of the bacteria in the body.

Corrosion pitting and environmentally assisted small crack growth

In many applications, corrosion pits act as precursors to cracking, but qualitative and quantitative prediction of damage evolution has been hampered by lack of insights into the process by which a crack develops from a pit. An overview is given of recent breakthroughs in characterization and understanding of the pit-to-crack transition using advanced three-dimensional imaging techniques such as X-ray computed tomography and focused ion beam machining with scanning electron microscopy. These techniques provided novel insights with respect to the location of crack development from a pit, supported by finite-element analysis. This inspired a new concept for the role of pitting in stress corrosion cracking based on the growing pit inducing local dynamic plastic strain, a critical factor in the development of stress corrosion cracks. Challenges in quantifying the subsequent growth rate of the emerging small cracks are then outlined with the potential drop technique being the most viable. A comparison is made with the growth rate for short cracks (through-thickness crack in fracture mechanics specimen) and long cracks and an electrochemical crack size effect invoked to rationalize the data.

Using Simulation to Support the R&amp;D Decision of a Pharmaceutical Firm

This paper illustrates how simulation modeling can be employed to support the R&D decision of a pharmaceutical firm. We do this in the context of a simplified but realistic example, where a drug company has just successfully completed the second phase of a three-phase process for assessing the effectiveness of a proposed drug in treating a targeted ailment with acceptable levels of side-effects. We provide step-by-step instruction for simulating the net present value and the internal rate of return of a ten-year pharmaceutical R&D project. The uncertainty lies in the efficacy of proposed drug and that of an alternative drug. Random too, are the initial size of the total market, and its subsequent exponential growth rate. Market share depends on the efficacy of proposed drug relative to that of the alternative drug, as well as, the subsequent introduction of new, alternative drugs in the market, which arrive in a random fashion. Finally, the ratio of cost of goods sold to sales and the terminal EBITDA multiple are also random. The problem is a variation of the Newdrug examples in chapters 19-21 of Andrew Metrick and Ayako Yasuda’s (2010) venture capital finance text.

Delayed density-dependent parasitism of eggs and pupae as a contributor to the cyclic population dynamics of the autumnal moth.

Many populations of forest Lepidoptera exhibit 10-year cycles in densities, with impressive outbreaks across large regions. Delayed density-dependent interactions with natural enemies are recognized as key factors driving these cyclic population dynamics, but emphasis has typically been on the larval stages. Eggs, pupae and adults also suffer mortality from predators, parasitoids and pathogens, but little is known about possible density relationships between mortality factors and these non-feeding life stages. In a long-term field study, we experimentally deployed autumnal moth (Epirrita autumnata) eggs and pupae to their natural enemies yearly throughout the 10-year population cycle in northern Norway. The abundance of another geometrid, the winter moth (Operophtera brumata), increased in the study area, permitting comparisons between the two moth species in predation and parasitism. Survival of autumnal moth eggs and pupae was related to the moth abundance in an inverse and delayed manner. Egg and pupal parasitoids dominated as density-dependent mortality factors and predicted the subsequent growth rate of the host population size. In contrast, effects of egg and pupal predators were weakly density dependent, and generally predation remained low. Parasitism rates did not differ between the autumnal and winter moth pupae, whereas predators preferred winter moth pupae over those of the autumnal moth. We conclude that parasitism of the autumnal moth by egg and pupal parasitoids can be related to the changes of the moth density in a delayed density-dependent manner. Furthermore, egg and pupal parasitoids cannot be overlooked as causal factors for the population cycles of forest Lepidoptera in general.

Impact of short-term salinity stress on larval development of the marine gastropod Crepipatella fecunda (Calyptraeidae)

Shallow-water coastal environments suffer frequent reductions in salinity due to heavy rains. This creates stressful conditions for the organisms found there, particularly for the early stages of development, including pelagic larvae. Freshly hatched larvae of the gastropod Crepipatella fecunda were exposed to different levels of salinity stress (32 (control), 25, 20 and 15) for a single 6h period. Subsequently, all veligers were maintained at normal control salinity (32) through metamorphosis. Periodic measurements were made of mortality, larval growth, and larval behavior. In particular, we measured changes in velar surface area, swimming velocity, clearance rate, oxygen consumption rate, shell growth rate, larval mortality, time to metamorphosis, and size at metamorphosis. The short exposure to salinity stress decreased subsequent mean growth rates at normal salinity and mean size at metamorphosis, but increased the duration of the planktonic period and the extent of larval mortality. It also reduced the rate at which the velar surface area increased relative to shell growth, and reduced mean larval swimming velocity. Mean oxygen consumption rates and clearance rates were also significantly lower for larvae that had been stressed early in larval life, compared with values obtained for control individuals. Exposure to low salinity for even a short time early in larval life can clearly have a substantial impact on the rest of larval development.

Effects of in ovo injection of conjugated linoleic acid on immune status and blood biochemical factors of broiler chickens

This experiment evaluated the effects of an in ovo injection of conjugated linoleic acid (CLA) on immune status and blood metabolites of broiler chicks at 21 and 42 days of age. One hundred and sixty fertilized eggs were selected from a young broiler breeder flock and allocated to4 treatments with 4 replicates each. CLA was injected into the air sack of the selected eggs (150 and 300 mg, dissolved in 100 mL of commercial diluents, CLA150 and CLA300) on Day18 of incubation. Two control groups (injected with or without diluent) were also included. In ovo injection of 150 or 300 ppm CLA increased (p&lt;0.05) feed intake of chickens as compared to control groups up to 42 days of age. Weight gain and feed conversion ratio of chickens from CLA300, were improved (p&lt;0.05) as compared to chicks hatched from eggs injected diluent or control group during total period. Cutaneous basophil hypersensitivity response to injection of phytohaemagglutinin-P significantly (p&lt;0.05) increased in chickens from CLA300 comparing to chicks from CLA150 or control ones. In ovo injection of 300 ppm CLA, decreased blood serum cholesterol and low density lipoprotein (LDL) of chickens as compared to control chicks or those from CLA150 (p&lt;0.05). Central lymphoid tissues such as bursa of Fabricius and thymus relative weights were increased (p&lt;0.05) in chickens from CLA300 as compared to chicks injected diluent or control groups. It is concluded that feeding 300 ppm CLA through in ovo injection may be effective to subsequent growth rate, immune response and decrease blood serum cholesterol and LDL of broiler chickens during whole experimental period.

Increased Risk of Very Low Birth Weight, Rapid Postnatal Growth, and Autism in Underweight and Obese Mothers

To determine whether prepregnancy weight was associated with children's birth weight, early physical growth, and autism diagnosis. Early Childhood Longitudinal Study-Birth Cohort data. United States. Representative sample of U.S. children followed from birth through kindergarten (n = 4800). Also, a subpopulation of the very low birth weight children was examined (n = 500). Maternal variables included age and prepregnancy body mass index. Changes in children's height, weight, and head circumference between 9 months and 2 years were used as growth metrics. Children's sex, age, birth weight, and reported autism were also considered. Logistic and multinomial logistic models assessed the impact of prepregnancy weight on birth weight and children's subsequent rate of physical growth and autism. Children born to underweight or obese mothers had increased odds of very low birth weight. Very low birth weight was related to rapid height and weight growth and more than twice the likelihood to subsequently be diagnosed with autism. For the subgroup of very low birth weight children, rapid head growth was related to a fivefold increase in the odds of autism. After accounting for the impact birth weight and growth rates, we found prepregnancy weight indirectly impacted autism risk. Being underweight or obese during prepregnancy indirectly increased risk for autism from increased odds of low birth weight and accelerated postnatal growth.

Fatigue Crack Growth in Aluminum Lithium Riveted Lap Joints

Fatigue crack initiation sites and the subsequent fatigue crack growth rate in riveted lap joints made of 2198-T8 Al-Li alloy were investigated through fractographic examinations. Two crack initiation sites were identified: 1) near the rivet holes and 2) at multiple sites along the faying surface. Fatigue crack tunneling was developed during the fatigue crack progression in all specimens, yielding final ductile fracture during the catastrophic fracture of the specimens. The fracture surface morphology exhibited shallow fatigue striations. The second phase constituents did not affect the fracture surface morphology. Multiple micro cracks and long interlaminar cracks occurred. Stereo (3-D) fracture surface morphologies indicate a meandering fracture surface, with local fatigue crack progressing along multiple directions and at different rates. Average crack growth rate (da/dN) along the width, thickness of the specimens and the feather lines were recorded, showing the effect of grain direction, alloying, and stress level on the fatigue crack growth behavior. The number of cycles to failure was also affected by the grain direction.