Electronic structure and carrier dynamics in InAs/InP double-cap quantum dots

International audienceThe carrier dynamics in InAs double-cap quantum dots DC-QDs grown on InP113B are investigated. The shape of these QDs can be controlled during the growth, yielding an emission wavelength of the system of about 1.55 m at room temperature. The DC-QD dynamics is studied by time-resolved photoluminescence experiments at low temperature for various excitation densities. A simplified dynamic model is developed, yielding results consistent with experimental data. This analysis yields the determination of the Auger coefficients and the intradot relaxation time in this system

Carrier relaxation dynamics in InAs/InP quantum dots

International audienceThe electronic properties of InAs/InP(113)B double-cap quantum dots (QDs) emitting around 1.55 μm are investigated. The carrier dynamics in QDs is studied by non-resonant timeresolved photoluminescence (tr-PL) experiments. This analysis reveals the QD electronic structure and the transient filling of the confined QD levels. Under low excitation densities, the spontaneous exciton lifetime is estimated and compared to previous time-resolved resonant and non-resonant experiments. Under high excitation density, a direct Auger recombination effect is identified. The temperature analysis enables us to distinguish Auger and phonon-assisted relaxation processes

In-situ nanodiamond to carbon onion transformation in metal matrix composites

In the present study, nickel matrix composites reinforced with a fine distribution of nanodiamonds (6.5 vol%) as reinforcement phase are annealed in vacuum at different temperatures ranging from 750 °C to 1300 °C. This is carried out to evaluate the in-situ transformation of nanodiamonds to carbon onions within a previously densified composite. The resulting materials are thoroughly analyzed by complementary analytical methods, including Raman spectroscopy, transmission electron microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. The proposed in-situ transformation method presents two main benefits. On one hand, since the particle distribution of a nanodiamond-reinforced composite is significantly more homogenous than in case of the carbon onions, it is expected that the transformed particles will preserve the initial distribution features of nanodiamonds. On the other hand, the proposed process allows for the tuning of the sp3/sp2 carbon ratio by applying a single straightforward post-processing step

Probing the growth window of LaVO₃ perovskites thin films elaborated using magnetron co-sputtering

LaVO3 is a promising material for tuning and improving solar cell performances when modifying the La/V stoichiometry. However, the production of LaVO3 thin films still requires a complex process (MBE, PLD), and the growth window of LaVO3 structure in terms of La/V ratio, already defined in the literature using hybrid-MBE is not determined for elaboration based on magnetron co-sputtering of both vanadium and lanthanum targets followed by an external reducing annealing that we use here. La/V ratio has been varied from 0.52 to 1.68 by changing the power applied to the vanadium target in order to synthesize films with different La/V ratios. The off-stoichiometry growth window has been investigated by complementary methods (XRD, XPS, FTIR and TEM). X-ray diffraction highlights the LaVO3 structure for all the films. For La-rich samples (La/V ratio andgt;1.2), the formation of lanthanum oxide La2O3 is observed at the top surface and interface with the substrate, according to XPS, FTIR and TEM investigations. On the other hand, for V-rich samples, only a slight modification of the structure is observed below the La/V ratio = 0.6; with the presence of a new IR vibration mode corresponding to a small contribution of vanadium oxide(s) present in volume. Our study allows a better definition of the LaVO3 growth window in terms of La/V ratio, estimated from 0.6 to 1.2. © 201

Pengenalan Budi Daya Ikan dalam Ember untuk Kemandirian Pangan di Kampung Enam, Kota Tarakan

The Covid-19 pandemic has had a major impact on society, such as job losses, rising staples, and economic hardship. Prices of food needs that continue to increase and are not affordable have resulted in food problems, one of which is protein. One of the high-quality protein is protein from fish. Fish as a fishery commodity that is relatively easy to cultivate on a large industrial scale and household scale for food self-sufficiency is catfish (Clarias sp). The purpose of this activity is to add insight and knowledge of the community about budikdamber for food self-sufficiency. The method of implementing community service activities in Kampung Six is carried out by counseling and training methods on Budikdamber. In this training activity, a bucket with 40 liters of water and 20 catfish seeds was used. Maintenance was carried out for 60 days with ad satiation feeding three times a day. Observations were made on growth, survival and water quality. The results of the activity found that 93% of the community partners had understood about Budikdamber. Budikdamber maintenance by partner communities gets an absolute weight growth value of catfish of 14 g, catfish survival value of 75%, and 1 bunch of kale per bucket. Based on the results of this activity, it is hoped that there will be the provision of special land for Budikdamber as an example for people who want to develop in their respective yards.The Covid-19 pandemic has had a major impact on society, such as job losses, rising staples, and economic hardship. Prices of food needs that continue to increase and are not affordable have resulted in food problems, one of which is protein. One of the high-quality protein is protein from fish. Fish as a fishery commodity that is relatively easy to cultivate on a large industrial scale and household scale for food self-sufficiency is catfish (Clarias sp). The purpose of this activity is to add insight and knowledge of the community about budikdamber for food self-sufficiency. The method of implementing community service activities in Kampung Six is carried out by counseling and training methods on Budikdamber. In this training activity, a bucket with 40 liters of water and 20 catfish seeds was used. Maintenance was carried out for 60 days with ad satiation feeding three times a day. Observations were made on growth, survival and water quality. The results of the activity found that 93% of the community partners had understood about Budikdamber. Budikdamber maintenance by partner communities gets an absolute weight growth value of catfish of 14 g, catfish survival value of 75%, and 1 bunch of kale per bucket. Based on the results of this activity, it is hoped that there will be the provision of special land for Budikdamber as an example for people who want to develop in their respective yards

Oral transfer of chemical cues, growth proteins and hormones in social insects.

Social insects frequently engage in oral fluid exchange - trophallaxis - between adults, and between adults and larvae. Although trophallaxis is widely considered a food-sharing mechanism, we hypothesized that endogenous components of this fluid might underlie a novel means of chemical communication between colony members. Through protein and small-molecule mass spectrometry and RNA sequencing, we found that trophallactic fluid in the ant Camponotus floridanus contains a set of specific digestion- and non-digestion related proteins, as well as hydrocarbons, microRNAs, and a key developmental regulator, juvenile hormone. When C. floridanus workers' food was supplemented with this hormone, the larvae they reared via trophallaxis were twice as likely to complete metamorphosis and became larger workers. Comparison of trophallactic fluid proteins across social insect species revealed that many are regulators of growth, development and behavioral maturation. These results suggest that trophallaxis plays previously unsuspected roles in communication and enables communal control of colony phenotypes

Carrier dynamics and saturation effect in (113)B InAs/InP quantum dot lasers

International audienceQuantum dot (QD) lasers exhibit many interesting and useful properties such as low threshold current, temperature insensitivity or chirpless behavior. In order to reach the standards of long-haul optical transmissions, 1.55 μm InAs QD lasers on InP substrate have been developed. Based on time resolved photoluminescence (PL) measurements, carrier dynamics behavior is at first investigated. Electroluminescence (EL) results are then shown at room temperature exhibiting a laser emission centered at 1.61 μm associated to a threshold current density as low as 820 A/cm2 for a six InAs QD stacked layers. Finally, a rate equation model based on the reservoir theory is used to model both time-resolved photoluminescence (TRPL) and electroluminescence results. It is shown that carrier dynamic calculations are in a good agreement with measurements since the saturation effect occurring at high injected power is clearly predicted

Past climate‐driven range shifts and population genetic diversity in arctic plants

High intra-specific genetic diversity is necessary for species adaptation to novel environments under climate change, but species tracking suitable conditions are losing alleles through successive founder events during range shift. Here, we investigated the relationship between range shift since the Last Glacial Maximum (LGM) and extant population genetic diversity across multiple plant species to understand variability in species responses.Location: The circumpolar Arctic and northern temperate alpine ranges.Methods: We estimated the climatic niches of 30 cold-adapted plant species using range maps coupled with species distribution models and hindcasted species suitable areas to reconstructions of the mid-Holocene and LGM climates. We computed the species-specific migration distances from the species glacial refugia to their current distribution and correlated distances to extant genetic diversity in 1295 populations. Differential responses among species were related to life-history traits.Results: We found a negative association between inferred migration distances from refugia and genetic diversities in 25 species, but only 11 had statistically significant negative slopes. The relationships between inferred distance and population genetic diversity were steeper for insect-pollinated species than wind-pollinated species, but the difference among pollination system was marginally independent from phylogenetic autocorrelation.Main conclusion: The relationships between inferred migration distances and genetic diversities in 11 species, independent from current isolation, indicate that past range shifts were associated with a genetic bottleneck effect with an average of 21% loss of genetic diversity per 1000 km−1. In contrast, the absence of relationship in many species also indicates that the response is species specific and may be modulated by plant pollination strategies or result from more complex historical contingencies than those modelled here

Global maps of soil temperature

Research in global change ecology relies heavily on global climatic grids derived from estimates of air temperature in open areas at around 2 m above the ground. These climatic grids do not reflect conditions below vegetation canopies and near the ground surface, where critical ecosystem functions occur and most terrestrial species reside. Here, we provide global maps of soil temperature and bioclimatic variables at a 1-km² resolution for 0–5 and 5–15 cm soil depth. These maps were created by calculating the difference (i.e., offset) between in-situ soil temperature measurements, based on time series from over 1200 1-km² pixels (summarized from 8500 unique temperature sensors) across all the world’s major terrestrial biomes, and coarse-grained air temperature estimates from ERA5-Land (an atmospheric reanalysis by the European Centre for Medium-Range Weather Forecasts). We show that mean annual soil temperature differs markedly from the corresponding gridded air temperature, by up to 10°C (mean = 3.0 ± 2.1°C), with substantial variation across biomes and seasons. Over the year, soils in cold and/or dry biomes are substantially warmer (+3.6 ± 2.3°C) than gridded air temperature, whereas soils in warm and humid environments are on average slightly cooler (-0.7 ± 2.3°C). The observed substantial and biome-specific offsets emphasize that the projected impacts of climate and climate change on near-surface biodiversity and ecosystem functioning are inaccurately assessed when air rather than soil temperature is used, especially in cold environments. The global soil-related bioclimatic variables provided here are an important step forward for any application in ecology and related disciplines. Nevertheless, we highlight the need to fill remaining geographic gaps by collecting more in-situ measurements of microclimate conditions to further enhance the spatiotemporal resolution of global soil temperature products for ecological applications

Global maps of soil temperature

Research in global change ecology relies heavily on global climatic grids derived from estimates of air temperature in open areas at around 2 m above the ground. These climatic grids do not reflect conditions below vegetation canopies and near the ground surface, where critical ecosystem functions occur and most terrestrial species reside. Here, we provide global maps of soil temperature and bioclimatic variables at a 1-km2 resolution for 0–5 and 5–15 cm soil depth. These maps were created by calculating the difference (i.e. offset) between in situ soil temperature measurements, based on time series from over 1200 1-km2 pixels (summarized from 8519 unique temperature sensors) across all the world\u27s major terrestrial biomes, and coarse-grained air temperature estimates from ERA5-Land (an atmospheric reanalysis by the European Centre for Medium-Range Weather Forecasts). We show that mean annual soil temperature differs markedly from the corresponding gridded air temperature, by up to 10°C (mean = 3.0 ± 2.1°C), with substantial variation across biomes and seasons. Over the year, soils in cold and/or dry biomes are substantially warmer (+3.6 ± 2.3°C) than gridded air temperature, whereas soils in warm and humid environments are on average slightly cooler (−0.7 ± 2.3°C). The observed substantial and biome-specific offsets emphasize that the projected impacts of climate and climate change on near-surface biodiversity and ecosystem functioning are inaccurately assessed when air rather than soil temperature is used, especially in cold environments. The global soil-related bioclimatic variables provided here are an important step forward for any application in ecology and related disciplines. Nevertheless, we highlight the need to fill remaining geographic gaps by collecting more in situ measurements of microclimate conditions to further enhance the spatiotemporal resolution of global soil temperature products for ecological applications