•A field study evaluated Red Snapper growth after the Deepwater Horizon oil spill.•Pre- and post-spill vonBertalanffy growth curves were not significantly different.•Age-specific growth of the ...dominant ages declined significantly following the spill.•Environmental variables were unable to describe the significant growth variation.•Results have implications for population productivity in the short- and long-term.
The explosion of the Deepwater Horizon (DWH) oil platform in 2010 released more than 200 million gallons of crude oil into the northern Gulf of Mexico (GoM). Elevated levels of carcinogenic polycyclic aromatic hydrocarbons (PAHs) were abundant in the upper water column throughout the event. Previous research suggests that PAHs may have negatively affected fishes in the northern GoM. Our objective was to test whether crude oil contamination from the DWH oil spill was correlated with changes in growth rates in adult Red Snapper, Lutjanus campechanus. We fit von Bertalanffy growth curves and back-calculated length-at-age using data collected from 2011–2013 during long-line surveys in the northern GoM and on the West Florida Shelf. No significant variation in von Bertalanffy growth parameters existed among the catch years; a combined-years model gave L∞, k, and t0 values of 82.91, 0.20, and 0.43, respectively. No significant difference existed between pre- (back-calculated) and post-DWH growth curves. However, annual widths of the fourth, fifth, and sixth increments (the dominant cohorts in the population) declined significantly post-DWH (2010–2012) by 13%, 15%, and 22%, respectively, and were significantly smaller than the mean width of each respective increment in pre-spill years (2006–2009). While the DWH event was related temporally to growth declines in the dominant adult age groups, other environmental factors (winds, temperature, and river discharge) may also affect growth. Accordingly, meridional (V) and zonal (U) winds, sea level height anomalies (a proxy for water temperature variation), and Mississippi River discharge were compared to increment widths but none of the factors were strongly correlated with variation in age-specific growth increments (maximum Pearson’s r=0.47). Therefore, we are unable to reject the hypothesis that the DWH resulted in growth rate declines as opposed to climatic variation.
The aim of this study was to evaluate the effect of different controlled water regimes on the morphophysiological indicators, phenophases, and ideal cutting time of forage cacti clones grown in a ...semiarid environment. From 2016 to 2018, in the semi-arid region of Brazil, the Miúda (MIU), Orelha de Elefante Mexicana (OEM) and IPA Sertânia (IPA) clones were submitted to three regimes (40%, 80% and 120% ETc, where ETc is crop evapotranspiration) and to rainfed conditions (0% ETc). Cladode area index and the dry matter yield (DM) were used for calculating the morphophysiological indices. The cladode emission aided in delimiting the phenophases and, based on the DM accumulation, defined the ideal time for cutting the crop. The OEM clone excelled in terms of dry matter accumulation with a maximum value of 0.0441 Mg ha−1 °Cday−1. The water regimes above 80% ETc rise the number of phenophases in MIU and IPA clones. Cultivating forage cactus under water regime up to 40% ETc for OEM (895 °Cday) and 80% ETc for MIU and IPA (737 °Cday and 708 °Cday, respectively) anticipates the harvest time. Thus, a controlled reduction in the amount of water no negatively impact the growth dynamics, phenology, or cutting time.
•Water regimes changes morphophysiology, phenophase and cutting time of cactus clones.•Cactus O. stricta proved to be more efficient in accumulating dry matter.•Phenophase 2 showed greater sensitivity to increases in the water amount.•Cutting time showed variations due to the clones and, water regimes.•Controlled water deficit brings forward the harvest time of the cactus clones.
We consider strongly damped wave equations with logarithmic mass-like terms with a parameter θ∈(0,1. This research is a part of a series of wave equations that was initiated by Charão-Ikehata 6, ...Charão-D'Abbicco-Ikehata considered in 5 depending on a parameter θ∈(1/2,1) and Piske-Charão-Ikehata 26 for small parameter θ∈(0,1/2). We derive a leading term as t→∞ of the solution, and by using it, a growth and a decay property of the solution itself can be precisely studied in terms of L2-norm. An interesting aspect appears in the case of n=1, roughly speaking, a small θ produces a diffusive property, and a large θ gives a kind of singularity, expressed by growth rates.
We estimate the effect of broadband infrastructure, which enables high-speed internet, on economic growth in the panel of OECD countries in 1996-2007. Our instrumental variable model derives its ...non-linear first stage from a logistic diffusion model where pre-existing voice telephony and cable TV networks predict maximum broadband penetration. We find that a 10 percentage point increase in broadband penetration raised annual per capita growth by 0.9-1.5 percentage points. Results are robust to country and year fixed effects and controlling for linear second-stage effects of our instruments. We verify that our instruments predict broadband penetration but not diffusion of contemporaneous technologies like mobile telephony and computers.
Abstract
Terrestrial animals in global wet-dry tropical ecosystems experience year-round high temperatures but concentrated summer rainfall. This highly seasonal precipitation is expected to have ...major evolutionary and ecological consequences for animals. We considered how strong seasonal patterns of rainfall might influence the environment and biological attributes of the world’s largest predatory lizard, the Komodo dragon (Varanus komodoensis). We predicted that annual variation in rainfall or temperature may influence the seasonal phenology of vegetation, and in turn, the phenology of Komodo dragon reproduction and hatchling emergence. Similarly, seasonal environmental differences may affect Komodo dragon rates of somatic growth, body condition, survival and daily movement. Our results indicated evidence of strong seasonal variation in mean monthly rainfall and leaf area index for open deciduous forest and closed dense forest. These environmental variables were significantly correlated with female Komodo dragon nesting activity and hatchling emergence. Neither Komodo dragon somatic growth rate nor body condition exhibited seasonal differences. There was, however, increased daily movement rates of Komodo dragons during the dry season. This suggests dry season associated life-history activities or thermoregulatory efficiency might explain increased daily movement. Ultimately, the Komodo dragon showed differential sensitivities in its biology to seasonal environmental variation.
Improving growth rates in indigenous Turcana breed should be one of the most important objectives for sheep specialists, do to the fact that over 70% of the sheep population from Romania is ...represented by the breed. Researches were carried out in a commercial farm from Timis county, on a number of 48 crossbreed F1 German Blackheaded Mutton x Turcana (GBMT) lambs, the control group was represented by purebreed Turcana (TU) lambs, both males and females (33 heads). The lambs were weighed at birth, at 28 days and at 8 months of age. During first 28 days, F1 GMBT registered an average daily gain of 229.46 g, compared to Turcana lambs witch registered an average of 194.12 g, differences being very significant statistically (p<0.001). Total growth gain at the age of 240 days was registered 40.51 kg in crossbreed lambs, and of 33.35 kg in purebreed Turcana lambs, differences were very significant statistically between the two groups (p<0.001). German Blackheaded Mutton rams could be used as crossing sires for indigenous Turcana breed in order to substantially improve growth rates in F1 lambs.
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•Crack tip stored energy density captures short fatigue crack growth rates across samples with strongly differing texture.•Elastic anisotropy and yield stress mismatch at grain ...boundaries in HCP Zircaloy-4 drive short crack growth rate fluctuations.•Crack path tortuosity in HCP single crystals is linked with the cyclic development of a shear back stress.
Rates of fatigue crack growth in Zircaloy-4 are highly microstructurally sensitive and dependent upon texture. Crystal plasticity finite element modelling with the eXtended Finite Element Method and a stored energy density fracture criterion are used to simulate crack propagation in single crystals and polycrystalline microstructures for comparison with experimental crack growth rate data. Results demonstrate that growth rate fluctuations at microstructural features are driven primarily by elastic anisotropy and yield stress mismatch. Additionally, reduced rate of growth in soft hexagonal close packed grains (relative to the remote loading direction) can be linked with crack path tortuosity, which is shown to be controlled by the cyclic development of an in-plane shear back stress. Most importantly, stored energy density is shown to accurately capture major microstructure-driven differences in crack growth rate. Comparison of simulated fatigue crack growth rates with experimental data enables estimation of the critical stored energy density for crack propagation in Zircaloy-4 to be 250 J/m2.
Arctica islandica supports an important fishery in the US Mid-Atlantic. This species is extremely slow growing and long-lived, characteristics that may make this species particularly vulnerable to ...fishing pressure and climate change. Understanding regional growth dynamics over time and growth responses to changing environments will improve current fishery assessments to maintain the sustainability of this stock. Two populations of A. islandica from Georges Bank and off Long Island on the US continental shelf with observed ages between 17 and 310 y were evaluated for age-at-length relationships and growth trends over time. Growth rates have been increasing at Georges Bank and Long Island since the 1700s. Growth rates at Long Island have been accelerating and have exceeded those at Georges Bank since the 1980s. Growth rates from this study support previous research that this species is sexually dimorphic, and females grow faster than males within a population post-maturation. Positive growth index periods at both sites may be synchronous with 32-y harmonics of the Atlantic Multi-Decadal Oscillation. A modification to the traditional Tanaka growth model that included a growth term to further increase growth at old age proved the best-fit growth model to not only each population, but also to birth-year cohorts. Both the classic and modified Tanaka models used in this study are vast improvements over the von Bertalanffy models currently applied to this species in assessment models and population dynamics models. Increasing growth rates over time resulted in fewer years of reproduction prior to recruiting to the fishery as A. islandica are reaching fishery size in an increasingly short period of time. The impact that reduced years of reproduction has on A. islandica population resiliency is yet unknown.
•A. islandica growth rates have been increasing over the past three centuries (USA).•Growth rates at Long Island have exceeded those at Georges Bank since the 1980s.•Growth is synchronous with 32-y harmonics of the Atlantic Multi-Decadal Oscillation.•A modification of the Tanaka growth model is the best-fit growth model.•Growth rates support evidence of sexual dimorphism.
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