Remote sensing of sunlight-induced chlorophyll fluorescence and reflectance of Scots pine in the boreal forest during spring recovery

A measurement campaign to assess the feasibility of remote sensing of sunlight-induced chlorophyll fluorescence (ChlF) from a coniferous canopy was conducted in a boreal forest study site (Finland). A Passive Multi-wavelength Fluorescence Detector (PMFD) sensor, developed in the LURE laboratory, was used to obtain simultaneous measurements of ChlF in the oxygen absorption bands, at 687 and 760 nm, and a reflectance index, the PRI (Physiological Reflectance Index), for a month during spring recovery. When these data were compared with active fluorescence measurements performed on needles they revealed the same trend. During sunny days fluorescence and reflectance signals were found to be strongly influenced by shadows associated with the canopy structure. Moreover, chlorophyll fluorescence variations induced by rapid light changes (due to transient cloud shadows) were found to respond more quickly and with larger amplitude under summer conditions compared to those obtained under cold acclimation conditions. In addition, ChlF at 760 nm was observed to increase with the chlorophyll content. During this campaign, the CO₂ assimilation was measured at the forest canopy level and was found remarkably well correlated with the PRI index.     

Impurity photovoltaic effect in GaAs solar cell with two deep impurity levels

The impurity photovoltaic (IPV) effect has been extensively investigated for silicon solar cells with indium impurities. A small positive effect on the efficiency was theoretically predicted, provided that efficient light trapping schemes are applied. Since IPV effects are predicted to be more pronounced in wider band gap materials and possibly also by introducing more than one impurity level, we carried out a numerical study on GaAs solar cells with copper impurities. Indeed, copper introduces multiple acceptor type mid-gap levels in GaAs, two of which are investigated here: one at 0.14 eV and another at 0.40 eV above the valence band edge. We used a solar cell device simulator (SCAPS) specially adapted to include the IPV effect. We varied the impurity concentration and the light trapping parameters of the device, and calculated the occupation probability of the impurity levels, the generation and recombination through these levels (thermal and optical) and the solar cell characteristics: quantum efficiency, QE(λ), short-circuit current J_sc, open-circuit voltage V_oc and efficiency η.A significant IPV effect with extended response in the infrared is calculated when efficient light trapping is present. When an internal reflection coefficient R=0.99 can be reached at both the front and the back surface of the solar cell, an increase of the short-circuit current densities 2 mA/cm² can be obtained. The consequences of two levels instead of one are calculated and discussed, leading to a trade-off between J_sc improvement and a V_oc decrease.     

Kinetic modeling of polychlorinated dibenzo-p-dioxin and dibenzofuran formation based on carbon degradation reactions

Combustion experiments in a laboratory-scale fixed bed reactor were performed to determine the role of temperature and time in polychlorinated dibenzo-p-dioxin (PCDD) and polychlorinated dibenzofuran (PCDF) formation, allowing a global kinetic expression to be written for PCDD/F formation due to soot oxidation in fly ash deposits. Rate constants were calculated for the reactions of carbon degradation, PCDD/F formation, desorption, and degradation. For the first time, values for activation and thermodynamic parameters for the overall reactions have been calculated for PCDD/F formation, desorption, and destruction reactions. Good agreement was found between the calculated rate constants for carbon degradation and for PCDD/F formation, indicating that the two processes have a common rate-determining step. Moreover, PCDD/F formation was found to be still active after long reaction times (24 h). These results points out the importance of carbon deposits in the postcombustion stages that can account for emissions long after their formation (memory effects). The calculated formation rates were 7-15 times higher than those reported in the literature from fly ash-only experiments, indicating the importance of both soot and a continuous source of chlorine. A comparison between full-scale incinerator rates and model calculated rates indicates that our model based on carbon degradation kinetic can be a tool to estimate emissions.     

5-Nitro-1,2,4-triazole-3-one: A review of recent advances（英）

The 3-Nitro-1,2,4-triazole-5-one (NTO) is a high energydensity materials of keen interest for both commercial and scientific worlds owing to its reduced sensitivity, better thermal stability and high performances. It plays a significant role to replace the current energetic ingredients. In this review, we summarize various strategies involved in the synthesis of NTO as well as the existing approaches to tailor its particle morphology and sizes. The most prominent properties of NTO, such as insensitivity and performance, which are usually required to produce efficient formulations,have been concisely discussed. In addition, this overview reports on some newer forms of NTO including derivatives and co-crystals available inthe literature, which can enhance the NTO features and extend its applications. The advantages and shortcomings of various NTO forms for specific and potential use are also highlighted together with the attempts made to overcome these issues. Therefore, efforts will certainly continue to improve characteristics and performances of NTO either by chemical modification or by co-crystallization in order to produce promisingformulations for widespread applications in the near future.     

Mobility analysis in vehicular ad hoc network (VANET)

This paper focuses on vehicle mobility analysis in VANET. The performance of vehicle mobility in terms of average inter-vehicle link available time and the average number of inter-vehicle link changes for maintaining an active link in VANET is analyzed using both handover model and random moving model, respectively. The theoretical analysis is verified by simulation experiments. The numerical results indicate that the analytical random moving model is able to appropriately present the behavior of vehicle moving under different conditions, especially when mobile vehicle is moving relatively fast. On the other hand, the effect of traffic conditions on the accuracy of theoretical analysis is also investigated.     

MCRA noise estimation for KLT-VRE-based speech enhancement

A new signal subspace-based approach is proposed for the enhancement of speech corrupted by a high level of noise. Conventional subspace-based methods use the minimum mean square error criterion to optimize the Karhunen-Loève Transform (KLT). In non-stationary noisy environments, the selection of the optimal order of the KLT-based speech enhancement model is a critical issue. Indeed, estimation of the relevant subspace dimensions depends on the environmental conditions that may change unpredictably. Therefore, a drastic KLT-based dimension reduction may induce the loss of relevant components of speech and conversely, a reconstruction using a higher order of the KLT model will be ineffective to remove the noise. The method presented in this paper uses a Variance of Reconstruction Error (VRE) criterion to optimally select the KLT order model. A prominent point of this subspace method is that it incorporates the Minima Controlled Recursive Averaging (MCRA) to estimate the noise Power Spectral Density (PSD) used in the gain function. Three variants of the VRE combined with MCRA methods are implemented and compared, namely the VRE-MCRA, VRE-MCRA2 and VRE-IMCRA. Objective measures show that VRE-based approaches achieve a lower signal distortion and a higher noise reduction than existing enhancement methods.     

Direct activation of K(Ca) channel in airway smooth muscle by nitric oxide: involvement of a nitrothiosylation mechanism?

The rat parotid gland produces a number of well-characterized secretory proteins. Relatively little is known, however, about the onset of their synthesis and cellular localization during gland development. Secretory protein expression was studied in parotid glands of fetal and postnatal rats using light and electron microscopic immunocytochemistry and Northern blotting. Amylase, parotid secretory protein (PSP), common salivary protein-1 (CSP-1), and SMGB were first detected by immunofluorescence in parotid glands of 18 day fetuses. By 5 days after birth, light and electron microscopic immunolabeling localized all of these proteins to the secretory granules of developing acinar cells. Labeling of acinar cells for DNAse I, however, was not observed until 18 days after birth. Between 9 and 25 days, CSP-1 and SMGB reactivity of acinar cells declined, but increased in intercalated duct cells. After 25 days, CSP-1 and SMGB were found only in intercalated ducts, and amylase, PSP, and DNAse I were restricted to acinar cells. Levels of CSP-1 and SMGB mRNA were relatively constant through 21 postnatal days, but declined significantly after that. Amylase and PSP mRNA increased rapidly and continuously from five days after birth to the adult stage. In contrast, DNAse I mRNA was not detectable until 18 days after birth. The immunocytochemical and molecular analyses define three basic patterns of protein expression in the rat parotid gland: proteins whose synthesis is initiated early in development and is maintained in the acinar cells, such as amylase and PSP; proteins that are initially synthesized by immature acinar cells but are restricted to intercalated ducts in the adult gland, such as CSP-1 and SMGB; and proteins that are synthesized only by mature acinar cells and first appear during the third postnatal week, such as DNAse I. The parotid gland exhibits four distinct developmental stages: prenatal, from initiation of the gland rudiment until birth; neonatal, from 1 day up to about 9 days postnatal; transitional, from 9 days to 25 days of age; and adult, from 25 days on. Although differences exist in timing and in the specific proteins expressed, these developmental stages are similar to those seen in the rat submandibular gland. Additionally, the results support the suggestion that intercalated ducts may differentiate from the neonatal acini.     

Effect of moisture, charge size, and chlorine concentration on PCDD/F emissions from simulated open burning of forest biomass

Loblolly pine (Pinus taeda) was combusted at different charge sizes, fuel moisture, and chlorine content to determine the effect on emissions of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDDs/Fs) as well as copollutants CO, PM, and total hydrocarbons. The experiments were performed in an enclosed chamber under conditions simulating open, prescribed burns of forest biomass. Burn progress was monitored through on line measurement of combustion gases and temperature while PCDD/F concentrations were determined by ambient sampling methods. PCDD/F toxic equivalency (TEQ) and total (tetra- to octa-CDD/F) emission factors were independent of charge size (1-10 kg) and moisture content (7-50%). However, the lower chlorinated, mono- to tri-CDD/F compounds were increased by poor combustion conditions: combustion efficiency lower than 0.919 was generally found when the moisture content was higher than 30%. The increase of fuel matrix chlorine from 0.04% to 0.8% using a brine bath resulted in about a 100-fold increase of PCDD/F to about 90 ng TEQ/kg of carbon burned, C(b). These emission factors were linearly dependent on Cl concentration in the biomass. PCDD 2,3,7,8-Cl-substituted congeners and homologue patterns were also influenced by the addition of chlorine resulting in emissions with a higher abundance of the most toxic congeners (TeCDD and PeCDD). When both chlorine and moisture content were increased in the fuel, a simultaneous effect of the two parameters was observed. The increased TEQ values expected from higher Cl concentrations were mitigated by the presence of water, giving MCE = 0.868, promoting formation of mono- to tri-PCDD/F, and lowering the TEQ value. Open burn simulations were used to study PCDD/F formation in different combustion conditions providing a mathematical correlation between PCDD/F emissions and chlorine and moisture content in the fuel.