Search results for "Dark"

Quasi-parallel precession diffraction: Alignment method for scanning transmission electron microscopes.

2018

Abstract A general method to set illuminating conditions for selectable beam convergence and probe size is presented in this work for Transmission Electron Microscopes (TEM) fitted with µs/pixel fast beam scanning control, (S)TEM, and an annular dark field detector. The case of interest of beam convergence and probe size, which enables diffraction pattern indexation, is then used as a starting point in this work to add 100 Hz precession to the beam while imaging the specimen at a fast rate and keeping the projector system in diffraction mode. The described systematic alignment method for the adjustment of beam precession on the specimen plane while scanning at fast rates is mainly based on …

Simulations of the effect of the contact energy levels on a simple model of a hot carrier cell

2016

In the present work, the performance of a simplified model of a hot carrier cell is examined at different energy levels of carrier collection. Incident photons, Monte Carlo generated by employing the ASTM G173-03 data set, are accounted for individually as they interact with the cell. It is assumed that the carriers can be collected ultra-fast, thus avoiding considering hot carrier thermalisation effects. Although the model is preliminary and lacking some mechanisms of hot carrier cells, it has been demonstrated that the present approach to modelling hot carrier solar cells can be developed into fully working models. Some effects of the absorption energy levels in the valence band have been…

Early Middle Ages Houses of Gien (France) from the Inside: Geoarchaeology and Archaeobotany of 9th–11th c. Floors

2018

International audience; At Gien (France), indoor floors from early Middle Ages occupation (8th–10th c. AD) are very well preserved, providing a new reference for archaeological investigation in northern France. This site is located on an outcrop, 20 m above the Loire valley, where a 15th c. castle stands now. The medieval occupation combines high-status houses with crafting and agricultural areas. They constitute a new urban nucleus, which grew 2 km east from an ancient Roman settlement. During the rescue excavation, four buildings of different status were sampled and studied using an integrated approach, combining stratigraphy, micromorphology, chemical, macro-remain and phytolith analyses…

Reevaluating the Role of Organic Matter Sources for Coastal Eutrophication, Oligotrophication, and Ecosystem Health

2019

Organic matter (OM) in aquatic systems is either produced internally (autochthonous OM) or delivered from the terrestrial environment (ter-OM). For eutrophication (or the reverse – oligotrophication), the amount of autochthonous OM plays a key role for coastal ecosystem health. However, the influence of ter-OM on eutrophication or oligotrophication processes of coastal ecosystems is largely unclear. Therefore, ter-OM, or ter-OM proxies are currently not included in most policies or monitoring programs on eutrophication. Nevertheless, ter-OM is increasingly recognized as a strong driver of aquatic productivity: By influencing underwater light conditions and nutrient- and carbon availability,…

First estimates of metabolic rate in Atlantic bluefin tuna larvae.

2020

Atlantic bluefin tuna is an iconic scombrid species with a high commercial and ecological value. Despite their importance, many physiological aspects, especially during the larval stages, are still unknown. Metabolic rates are one of the understudied aspects in scombrid larvae, likely due to challenges associated to larval handling before and during respirometry trials. Gaining reliable estimates of metabolic rates is essential to understand how larvae balance their high growth needs and activity and other physiological functions, which can be very useful for fisheries ecology and aquaculture. This is the first study to (a) estimate the relationship between routine metabolic rate (RMR) and …

A novel method to predict dark diversity using unconstrained ordination analysis

2019

[Questions] Species pools are the product of complex ecological and evolutionary mechanisms, operating over a range of spatial scales. Here, we focus on species absent from local sites but with the potential to establish within communities — known as dark diversity. Methods for estimating dark diversity are still being developed and need to be compared, as well as tested for the type, and amount, of reference data needed to calibrate these methods. [Location] South Bohemia (48°58′ N, 14°28′ E) and Železné Hory (49°52′ N, 15°34′ E), Czech Republic. [Method] We compared a widely accepted algorithm to estimate species pools (Beals smoothing index, based on species co-occurrence) against a nove…

Unexpected high production of biohydrogen from the endogenous fermentation of grape must deposits

2020

International audience; The aim of this work was to assess the performances of wine byproduct biomass for hydrogen production by dark fermentation. Grape must deposits from two grape varieties (Pinot Gris and Chardonnay) were considered, either with external microbial inoculum or without. We show that grape must residues contain endogenous microflora, well adapted to their environment, which can degrade sugars (initially contained in the biomass) to hydrogen without any nutrient addition. Indeed, hydrogen production during endogenous fermentation is as efficient as with an external heat-treated inoculum (2.5 ± 0.4 LH2.L-1reactor and 1.61 ± 0.41 molH2.mol-1consumed hexose, respectively) with…

Behavior of mixed Chlorophyceae cultures under prolonged dark exposure. Respiration rate modeling

2016

[EN] The behavior of three different microalgal cultures, when exposed for a long period (>48 h) to dark conditions, was studied with a methodology based on respirometry. The cultures were transferred to darkness and the oxygen evolution in the reactors was monitored after successive air injections. Several sequential oxygen uptake rates were thus calculated and a respiration constant, assuming a first order decay of a fraction of the biomass, was obtained by calibration. Initial specific oxygen uptake rates were in the range of 0.9 5.1 mg O2 g TSS−1 h−1 and dark respiration constants in the range of 0.005 0.018 h−1.

The preference and costs of sleeping under light at night in forest and urban great tits

2019

Artificial light at night (ALAN) is an increasing phenomenon associated with worldwide urbanization. In birds, broad-spectrum white ALAN can have disruptive effects on activity patterns, metabolism, stress response and immune function. There has been growing research on whether the use of alternative light spectra can reduce these negative effects, but surprisingly, there has been no study to determine which light spectrum birds prefer. To test such a preference, we gave urban and forest great tits (Parus major) the choice where to roost using pairwise combinations of darkness, white light or green dim light at night (1.5 lux). Birds preferred to sleep under artificial light instead of dar…

2021

Many phytophagous insects harbor symbiotic bacteria that can be transmitted vertically from parents to offspring, or acquired horizontally from unrelated hosts or the environment. In the latter case, plants are a potential route for symbiont transfer and can thus foster a tripartite interaction between microbe, insect, and plant. Here, we focus on two bacterial symbionts of the darkling beetle Lagria villosa that belong to the genus Burkholderia; the culturable strain B. gladioli Lv-StA and the reduced-genome strain Burkholderia Lv-StB. The strains can be transmitted vertically and confer protection to the beetle’s eggs, but Lv-StA can also proliferate in plants, and both symbiont strains h…