Discovering Precise Temporal Patterns in Large-Scale Neural Recordings through Robust and Interpretable Time Warping

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Density-dependent population regulation detected in short time series of saproxylic beetles

Understanding the regulation of natural populations has been a long-standing problem in ecology. Here we analyze the population dynamics of 17 species of saproxylic beetles in Shizuoka Prefecture, Japan collected over 11–12 years using autoregressive integrated moving average (ARIMA) models. We first examined the dynamics for indications of the order of the ARIMA models and evaluated the time series to determine that it was not simply a random, white noise sequence. All species dynamics were not mere random noise, and ARIMA models up to lag 3 were considered. The best model was selected from the possible ones using several criteria: model convergence, weak residual autocorrelation, the small sample AIC must be among the smallest that were not significantly different, and the lag indicated by the cutoff values in the detrended partial autocorrelation function. We found significant and nearly significant direct density-dependence for 14 of the 17 species, varying from −0.709 and stronger. The characteristic return rates were strong and only one species had a weak return rate (>0.9), implying that these species were strongly regulated by density-dependent factors. We found that populations with higher order ARIMA models (lag 2 and 3) had weaker return rates than populations with ARIMA models with only one lag, suggesting that species with more complex dynamics were more weakly regulated. These results contrast with previous suggestions that 20+ years are needed to detect density dependence from population time series and that most populations are weakly regulated.     

Time Course of the Metabolite Patterns of Intraventricularly Injected [3H]Noradrenaline in Rat Brain Regions

In the hypothalamus, septum, pons with medulla, and hippocampus regions of rat brain, the level of radioactivity of [3H]noradrenaline and of five of its metabolites were determined up to 6 h after intraventricular injection of the tritiated amine. The following main results were found: In anterior hypothalamus and septum, the [3H]noradrenaline level declined in two phases. Similar turnover curves were obtained for the primary deaminated metabolites, with almost the same final half-lives as for [3H]noradrenaline. The level of the initial methylation product, normetanephrine, also showed a biphasic decline, which did not correspond to that of [3H]noradrenaline but rather was faster throughout the experiment. The final metabolites (i.e., the glycol sulfates) reached maximal levels in hypothalamus and septum earlier than in other regions. Thereafter, their levels declined with almost similar rates in all areas tested, but always faster than the [3H]noradrenaline level. The following conclusions were drawn: In areas rich in catecholaminergic nerve terminals, there seems to be a site, in addition to the vesicular storage pool, that accumulates exogenous noradrenaline and then releases it with relatively short half-lives. The contents of primary deaminated metabolites followed the turnover of [3H]noradrenaline at both sites. Exogenous [3H]noradrenaline seems to be methylated at two extraneuronal sites, which are distinguished by the rates of subsequent deamination. The size of the pool of slowly deaminated [3H]normetanephrine that is formed immediately after [3H]noradrenaline injection determined the apparent turnover of this product throughout the experiment and, thus, like the final metabolites, reflects for several hours the initial degradation of the unstored [3H]noradrenaline, rather than the metabolism of the stored amine.(ABSTRACT TRUNCATED AT 250 WORDS)     

Assessment of nitrogen flows into the Cuban landscape

The alteration of the nitrogen (N) cycle by human activities is widespread and has often resulted in increased flows of nitrogen to the marine environment. In this paper we have attempted to know the changes of N fluxes in Cuba by quantifying the N inputs to the landscape from (1) fertilizer applications, (2) atmospheric deposition, (3) biological nitrogen fixation and (4) net import of food and feeds. N-inputs to the country progressively increased until the end of the 20th century, reaching a peak during the 80s when low cost fertilizer imported from the former Soviet Union led to heavy rates of application. This rapid growth represented more than a 5-fold increase with respect to pristine values; higher than the two-fold global increase of anthropogenic N reported by Vitousek et al. (1997 Human alteration of the global nitrogen cycle: sources and consequences. Ecol. Appl. 7:737–750). Inorganic fertilizer was the largest single source of reactive N, followed by atmospheric deposition, biological fixation, and net imports of foods and feedstocks. Nitrogen inputs peaked in 1987 and data expressed on an area basis show that N flux to the Cuban landscape, in the 80s, was one of the highest reported in the literature. During the 90s, there was a dramatic drop in nitrogen inputs mainly associated to a decrease in the use of inorganic fertilizer. Other factors reducing nutrient inflows to Cuba, during the same period, were imports of foodstuff and livestock feeds, a decrease of nitrogen oxide emissions, and a decrease in the sugar cane crop area. Using an empirical relationship (Howarth et al. 1996 Regional nitrogen budgets and riverine N & O fluxes for the drainages to the North Atlantic Ocean: Natural and human influences. Biogeochemistry 35:75–139) we present a very preliminary estimate of N-inputs to coastal waters and discuss the consequences of these changes on the coastal zone.     

A Microfluidic Device for Studying Multiple Distinct Strains

The study of cell responses to environmental changes poses many experimental challenges: cells need to be imaged under changing conditions, often in a comparative manner. Multiwell plates are routinely used to compare many different strains or cell lines, but allow limited control over the environment dynamics. Microfluidic devices, on the other hand, allow exquisite dynamic control over the surrounding conditions, but it is challenging to image and distinguish more than a few strains in them. Here we describe a method to easily and rapidly manufacture a microfluidic device capable of applying dynamically changing conditions to multiple distinct yeast strains in one channel. The device is designed and manufactured by simple means without the need for soft lithography. It is composed of a Y-shaped flow channel attached to a second layer harboring microwells. The strains are placed in separate microwells, and imaged under the exact same dynamic conditions. We demonstrate the use of the device for measuring protein localization responses to pulses of nutrient changes in different yeast strains.     

The 24-h time budget of a takh harem stallion (Equus ferus przewalskii) pre- and post-reintroduction

Focal animal sampling was used to determine the 24-h time budget of a takh harem stallion (Equus ferus przewalskii) during the 2 weeks prior to, and the two weeks following, reintroduction into the Hustain Nuruu Steppe Reserve, Mongolia. Both before and after release, the stallion spent approximately 47% of his time grazing, 6% standing, and 5% in recumbent rest. The biggest changes to the time budget after release were a 4-fold increase in the amount of time spent moving, and a 50% decrease in the amount of time spent resting in a standing position. During the middle of the day when the temperatures were hottest, the stallion exhibited less grazing and more standing resting behaviour than in the morning or evening hours. Recumbent rest invariably occurred in the hours before dawn.     

Optimizing cell-anatomical chronologies of Scots pine by stepwise increasing the number of radial tracheid rows included—Case study based on three Scandinavian sites

Cell-anatomical studies are a fast growing branch of dendrochronology, since they promise additional environmental proxy information with high temporal resolution. It is unclear, however, how many radial files of tracheids have to be considered to establish reliable wood anatomical time series for conifer species. Here, we investigate this question for four common cell-anatomical variables (cell-wall thickness, lumen area, lumen diameter and cell diameter) in Scots pine using examples from three Scandinavian sites. Cell-anatomical time series averaged from six measurement paths can reach the 90% confidence level of ten measurement paths at all sites. While lumen area generally required the most measurement paths in other cell-anatomical variables, cell-wall thickness required the least measurement paths.