Are long‐run output growth rates falling? Li, Mengheng; Mendieta‐Muñoz, Ivan
Metroeconomica,
February 2020, 2020-02-00, 20200201, Volume:
71, Issue:
1
Journal Article
Peer reviewed
Open access
This paper studies the evolution of long‐run output and technical progress growth rates in the G‐7 countries during the post‐war period by considering the concept of the natural rate of growth. We ...use time‐varying parameter models that incorporate both stochastic volatility and a Heckman‐type two‐step estimation procedure that deals with the possible endogeneity problem in the econometric models. Our results show a significant decline in long‐run growth rates that is not associated with the detrimental effects of the Great Recession, and that the rate of growth of technical progress appears to be behind the slowdown in long‐run GDP growth.
We consider log-growth rates of Romanian cities’ populations for all cities in the country in the period 1992-2019 on an annual basis. We construct annual, quinquennial and decennial log-growth rates ...and fit to them thirty-one different statistical distributions. The best results with Kolmogorov–Smirnov, Cramér–von Mises and Anderson–Darling statistics are obtained by a mixture of five stretched Gaussian distributions (5sG) with some fixed parameters, and with the AIC, BIC, HQC information criteria are obtained with mixtures of three logistic distributions (3L), that may have or may have not exponential tails. Just as an illustration, we propose a generating stochastic mechanism for the 3L. Dedicated to Laura Andrés Alcalde
Growth rates made easy Hall, Barry G; Acar, Hande; Nandipati, Anna ...
Molecular biology and evolution
31, Issue:
1
Journal Article
Peer reviewed
Open access
In the 1960s-1980s, determination of bacterial growth rates was an important tool in microbial genetics, biochemistry, molecular biology, and microbial physiology. The exciting technical developments ...of the 1990s and the 2000s eclipsed that tool; as a result, many investigators today lack experience with growth rate measurements. Recently, investigators in a number of areas have started to use measurements of bacterial growth rates for a variety of purposes. Those measurements have been greatly facilitated by the availability of microwell plate readers that permit the simultaneous measurements on up to 384 different cultures. Only the exponential (logarithmic) portions of the resulting growth curves are useful for determining growth rates, and manual determination of that portion and calculation of growth rates can be tedious for high-throughput purposes. Here, we introduce the program GrowthRates that uses plate reader output files to automatically determine the exponential portion of the curve and to automatically calculate the growth rate, the maximum culture density, and the duration of the growth lag phase. GrowthRates is freely available for Macintosh, Windows, and Linux. We discuss the effects of culture volume, the classical bacterial growth curve, and the differences between determinations in rich media and minimal (mineral salts) media. This protocol covers calibration of the plate reader, growth of culture inocula for both rich and minimal media, and experimental setup. As a guide to reliability, we report typical day-to-day variation in growth rates and variation within experiments with respect to position of wells within the plates.
Plant populations are limited by resource availability and exhibit physiological trade‐offs in resource acquisition strategies. These trade‐offs may constrain the ability of populations to exhibit ...fast growth rates under water limitation and high cover of neighbours. However, traits that confer drought tolerance may also confer resistance to competition. It remains unclear how fitness responses to these abiotic conditions and biotic interactions combine to structure grassland communities and how this relationship may change along a gradient of water availability.
To address these knowledge gaps, we estimated the low‐density growth rates of populations in drought conditions with low neighbour cover and in ambient conditions with average neighbour cover for 82 species in six grassland communities across the Central Plains and Southwestern United States. We assessed the relationship between population tolerance to drought and resistance to competition and determined if this relationship was consistent across a precipitation gradient. We also tested whether population growth rates could be predicted using plant functional traits.
Across six sites, we observed a positive correlation between low‐density population growth rates in drought and in the presence of interspecific neighbours. This positive relationship was particularly strong in the grasslands of the northern Great Plains but weak in the most xeric grasslands. High leaf dry matter content and a low (more negative) leaf turgor loss point were associated with high population growth rates in drought and with neighbours in most grassland communities.
Synthesis: A better understanding of how both biotic and abiotic factors impact population fitness provides valuable insights into how grasslands will respond to extreme drought. Our results advance plant strategy theory by suggesting that drought tolerance increases population resistance to interspecific competition in grassland communities. However, this relationship is not evident in the driest grasslands, where above‐ground competition is likely less important. Leaf dry matter content and turgor loss point may help predict which populations will establish and persist based on local water availability and neighbour cover, and these predictions can be used to guide the conservation and restoration of biodiversity in grasslands.
A better understanding of how both biotic and abiotic factors impact population fitness provides valuable insights into how grasslands will respond to extreme drought. These results advance plant strategy theory by suggesting that drought tolerance increases population resistance to interspecific competition in grassland communities. However, this relationship is not evident in the driest grasslands, where above‐ground competition is likely less important. Leaf dry matter content and turgor loss point may help predict which populations will establish and persist based on local water availability and neighbour cover, and these predictions can be used to guide the conservation and restoration of biodiversity in grasslands.
The Madden-Julian Oscillation (MJO) is the most prominent mode of intraseasonal variability in the tropics which is responsible for much of the observed intraseasonal climate variance not only there ...but also in higher latitudes. The short time-span of modern instrumental data limits our understanding of the MJO and obtaining MJO information from natural archives could extend this greatly. Here a Giant Clam shell (Tridacna spp.) with a life span about two years (from January 29, 2012 to December 9, 2013) was collected from the northern South China Sea, in the western Pacific. Several daily to hourly resolution biological and geochemical proxy records, including the daily growth rate, hourly Fe/Ca, Sr/Ca and fluorescence intensity, were developed to compare these with local weather/climate records. Spectral analyses suggested that these ultra-high resolution proxy records can clearly record MJO variability in the tropics. The substantial connection between the proxy records and MJO possibly linking through the local effective solar radiation, SST, precipitation and wind speeds. This is the first record of the MJO signal in a natural paleoclimate archive. Our findings provide new insights to study the MJO beyond the instrumental records, and since fossil Tridacna shells from different geological times can be used to investigate the MJO under various climate conditions.
•Giant Clam shell (Tridacna spp.) has clear daily growth bands.•Daily to hourly resolution biogeochemical proxy records were developed.•MJO spectral bands were found in proxy records.•The first time MJO signal has been detected from a paleoclimate archive.•Paleo-MJO could be studied using fossil Tridacna shells.
Deep-sea corals are a useful archive of thermocline, intermediate, and deep waters in past oceans. However, application of traditional oceanographic tracers to deep-sea corals remains a challenge due ...to our insufficient understanding of their “vital effects”. Deep-sea corals are ideal test organisms to study the mechanism underlying vital effects generally, due to the large tracer gradients in individual corals living under relatively constant environmental conditions. Lessons learned from these corals might apply to other scleractinia and to marine calcifiers more generally. Here we present stable isotope, minor and trace metal (Me/Ca ratios) data in a suite of modern Desmophyllum dianthus specimens, collected over multiple spatial scales in individual corals (bulk, micromill, SIMS, NanoSIMS), with multi-proxy analyses made on the same material whenever possible. Spatially coherent Me/Ca correlations are observed in the fibrous aragonite of individual corals, including positive correlations between Mg/Ca, Li/Ca and B/Ca, as well as negative correlations between Mg/Ca and Sr/Ca, consistent with previous studies. We also for the first time document strong correlations between the isotopic (δ18O and δ13C) and elemental compositions of the skeletons, most notably a negative correlation between δ18O and Mg/Ca. The centers of calcification (COCs) in the coral skeletons show distinct tracer correlations from the aragonite fibers that possibly reflect a more complicated formation mechanism. We interpret the spatially coherent tracer correlations in deep-sea corals with a numerical model of coral calcification previously developed for stable isotopes that considers the role of the enzyme carbonic anhydrase in the calcification processs. With the carbonate chemistry in the model constrained by the stable isotope data, we are able to explain the observed Me/Ca correlations as well as their range of variability, as a result of internal pH elevation in the extracellular calcifying fluid (ECF) of the corals with limited Ca-pumping through the calicoblastic membrane. In particular, the positive Mg/Ca–B/Ca correlation in the fibrous aragonite suggests a borate (B(OH)4–) substitution for carbonate ion (CO32–) incorporation mechanism in biogenic aragonite. We also suggest the growth rate dependence of the incorporation of minor and trace elements based conceptually on an ion-by-ion growth model may help explain the absolute Me/Ca values in biogenic aragonites. Finally, we generally find more limited tracer variability in corals from undersaturated seawater compared to their counterparts from supersaturated conditions, suggesting a limit to their internal pH elevation in response to this environmental stress. Understanding the biomineralization mechanisms underlying the vital effects is important for better use of these tracers for paleoceanographic applications, and may shed light on the response of marine calcification to future ocean acidification.
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•Heat transfer of static layer melt crystallization in tubular crystallizer.•Structure of crystal layer with large amounts of bubbles.•Model correlating growth rate with physical and ...experimental parameters.•Effective thermal conductivity of crystal layer.•Four distinct stages in the process of static layer melt crystallization.
The growth behaviors of crystal layers during static layer melt crystallization was studied from the perspectives of morphology structure, growth rates and temperature evolution. The temperature distributions of the melt and crystal layer were deduced. With these results, the heat transfer during crystallization was analyzed by considering the relative influences of natural convection, heat conduction in the melt and latent heat of crystallization. A model correlating growth rate with physical and experimental parameters was derived based on energy conservation. Effective thermal conductivity of crystal layers was evaluated. It was confirmed that the structure and density of the crystal layer can significantly affect the thermal conductivity. According to the temperature curves of melt, the static layer melt crystallization process in a tubular crystallizer can be divided into four stages as nucleation stage, fast growth stage, slow growth stage and steady state stage.
Environmental barrier coatings (EBCs) are an enabler for SiC/SiC ceramic matrix composites (CMCs) in gas turbines by protecting CMCs from environmental degradation. A critical EBC failure mode is the ...EBC spallation due to a build-up of elastic strains caused by the formation of SiO2 scale, known as TGO (thermally grown oxide). H2O, a byproduct of combustion reactions, accelerates the TGO-induced EBC failure by increasing TGO growth rates by orders of magnitude. NASA’s approach to improve the EBC life, therefore, is to reduce TGO growth rates. NASA discovered that modifying the TGO chemistry by modifying the EBC chemistry of Gen 2 EBC (Si / Yb2Si2O7) reduces the TGO thickness by up to ∼80 %. A study was undertaken to understand the oxidation mechanism of modified Gen 2 EBCs as well as to investigate the effect of EBC and CMC chemistry on TGO growth rates. This study confirmed the previously proposed TGO-controlled oxidation mechanism of modified Gen 2 EBCs and determined the correlations between the EBC and CMC chemistry, TGO chemistry, and TGO growth rates.
•Biological N fixation (BNF) was maximized early in the seed filling period, achieving a maximum rate of 3 kg N ha–1 day–1.•Biomass production was a better predictor of BNF than seed protein or ...environmental factors.•The BNF rate during seed-fill was driven by crop growth rate (C supply) rather than seed N accumulation rate (N demand).•The N exported in seed exceeded the N derived from BNF, indicating a negative partial N balance for soybean production.
The rainfed USA Midwestern region has deep, fertile soils and leads the USA in soybean Glycine max, (L.) Merr. production. Biological nitrogen (N) fixation (BNF) contributes a portion of the soybean N requirement, but variability in BNF is poorly understood and estimates of BNF for this region are rare. We established experiments in Iowa, USA to gain a better understanding of BNF and increase its predictability. We collected in-season BNF measurements accompanied by high temporal resolution soil and plant growth measurements. Across two years, two locations and two planting dates, we found that BNF contributed 23–65% of total aboveground N accumulation in soybean. The BNF rate was maximized at the early seed-filling period and varied from 1 to 3 kg N ha−1day−1. During seed filling period, the rate of BNF was related to crop growth rate (carbon (C) supply) but not to N accumulation by the reproductive organs (N demand). We found that a minimum crop growth rate of 135 kg dry matter ha−1day-1 is required to sustain maximum BNF rates. In contrast to BNF, the soil inorganic N uptake rate was related to seed N demand but not to C supply. Biomass production was the best predictor of total soybean BNF (R2 > 0.83). On average, 0.013 kg N was fixed per kg biomass produced. Across all trials, the N exported via seed was greater than the N imported via BNF, which suggests that Midwest US soybeans may reduce soil organic matter. We concluded that future research efforts should focus on increasing C – rather than N – availability during the seed filling period towards improving both grain yields and environmental sustainability.
According to the ‘fitness‐suitability' hypothesis, ongoing changes in climate are expected to affect habitat suitability and hence species' fitness. In trees, differences in fitness may manifest as ...changes in growth rates, which will alter carbon uptake. Using tree‐ring data, we calculated > 1.5 million annual stem growth rate estimates (standardized for tree size) for 15 677 trees representing 37 species from 558 populations throughout eastern North America. We used collections data and species distribution models to estimate each population's climatic suitability from 1900 to 2010. We then assessed the relationships between growth, suitability and time using linear mixed‐effects models. We found that stem growth rates decreased significantly through time independent of changes in climate suitability and that relationships between growth rates and climate suitability were highly variable across species. Contrary to expectations, we found that growth rates were negatively correlated with species' climate suitability, a relationship that was consistent over time for gymnosperms and became more negative through time for angiosperms. These results may suggest that stem growth rates are not a good proxy for fitness and/or that unidentified factors may be slowing tree growth and outweighing any potential benefits of climate change and increasing atmospheric CO2 concentrations. Regardless of the cause, this finding indicates that we should not count on the increased growth of eastern North American trees to help offset anthropogenic carbon emissions.
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