Impact of Periodic Current Pulses on Li-Ion Battery Performance

International audiencePulse charging and pulse discharging have been reported by many authors in the literature to improve the performance of various secondary electrochemical cells. Only a few authors mentioned the effects of such charge and discharge method on lithium-ion batteries. The overall objective of this work is to experimentally investigate the impact of certain current pulse profiles on the electrical performance of Li-ion batteries. The results highlight a detrimental impact of periodic pulses on the cell performance compared to profiles with constant current

Synthesis and reactivity of low valent main-group compounds

Low-valent, low-coordinate or multiply bonded main group compounds are of interest for their reactivity. Properties usually observed for transition metals, such as small molecule activation, are possible for these classes of main group compounds. The development of the coordination chemistry of main group elements allows the synthesis of new types of species, which could not be achieved before, by providing electronic and kinetic stabilisation. In the following sections are presented reactivity studies of silylenes, low-valent silicon species, and phosphaborenes (RP=BR’), multiply bonded phosphorus-boron compounds. Chapter I gives an overview of low-valent and low-coordinate silicon chemistry. Two main types of silicon species can be distinguished in this area: silylenes and base-stabilised silicon compounds. Silylenes (:SiR2) are heavier analogue of carbenes (:CR2) and have simultaneously similar and different properties compared to carbenes. Although less studied than carbenes, silylenes also have interesting potential for coordination chemistry to transition metals or main group elements. Base-stabilised silicon compounds have been known for more than a century, however, only the recent use of N-heterocyclic carbene (NHC) ligands has allowed isolation of new low coordinate silicon species, such as the carbene-stabilised diatomic and triatomic silicon(0) clusters, which respectively feature two and three silicon atoms in the formal oxidation state of zero. Chapter II is a study of oxidative addition to an N-heterocyclic silylene 1,3-bis(diisopropylphenyl)-1,3-diaza-2-silacyclopent-4-en-2-ylidene, a heavier analogue of N-heterocyclic carbene. An N-heterocyclic silylene was reacted with several main group halides (SiI4, PCl3 and BBr3). Oxidative addition was observed in each case, however, stability studies of the oxidative addition products show that only the product from the reaction with SiI4 is isolable. The reactivity of this product was studied toward reduction with alkali metals, reaction with bases, such as carbenes, organolithium reagents and phosphines. The addition of an excess of the N-heterocyclic silylene allows double oxidative addition from SiI4 to two N-heterocyclic silylenes. Finally, the addition of an excess of N-heterocyclic silylenes to BBr3 allows the observation of a relatively stable silylene-coordinated silylborane. Chapter III covers the attempted synthesis of a new type of N-heterocyclic silylene, which involves a bridgehead nitrogen atom, providing enhanced reactivity to this N-heterocyclic silylene compared to classical examples. This chapter includes the full synthesis and characterisation of the diamine ligand precursor N-1,3- diisopropylphenyl-3-piperidinemethanamine. The study of its reactivity was then carried out in order to insert silicon halide species into the structure, to reach the targeted N-heterocyclic silylene by reduction. The different conditions, which were tried on the ligand, did not successfully afford the targeted silane. The N-heterocyclic silylene could not be achieved. Chapter IV introduces the chemistry of mixed group III-V (13-15) compounds, which are widely used in electronic devices. Their synthesis involves harsh conditions such as chemical vapor deposition (CVD), metal-organic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE). Solution phase synthesis is a possible route to these mixed group III-V compounds, which will allow the use of milder conditions. Already achieved for some of them (GaAs, GaP, GaSb, InP, InSb), the solution phase synthesis of lighter mixed group III-V compounds, such as boron-phosphide (PB), is still elusive. The recent development of the chemistry of bas-estabilised phosphaborenes RP=BR’(L), mixed compounds involving a phosphorus-boron double bond, highlighted a possible way to make boron-phosphide through solution phase preparation. The use of N-heterocyclic carbenes (L) could also allow stabilisation of new allotropes of boron-phosphide PB(L). Chapter V explores the chemistry of minimally substituted base-stabilised phosphinoboranes [(Me3Si)2PBBr2(L)] (L = NHC) and phosphaborenes [Me3SiP=BBr(L)] achieved by base-promoted abstraction of trimethylsilyl halide from a phosphorus-borane adduct precursor [(Me3Si)3P→BBr3]. The functionalisation of [(Me3Si)2PBBr2(L)] affords the [H2PBBr2(L)] and similar base-promoted dehydrohalogenation allows the synthesis of the phosphaborene [HP=BBr(L)]. An unsaturated NHC used in this chemistry showed limited stability to the conditions used in the attempt to form base-stabilised boron-phosphide. The chemistry has been reexplored using a new NHC, which is expected to be more stable and enable the synthesis of base-stabilised boron-phosphide PB(L). The reactivity of phosphaborenes has been explored and hydrogenation of [HP=BBr(L)] or [(Me3Si)P=BBr](L) successfully gives the phosphinoboranes [H2PBHBr(L)] and [(Me3Si)HPBHBr(L)]. Base-promoted dehydrohalogenation from [H2PBHBr(L)] allows the observation of the base-stabilised parent diphosphadiboretane, [(HPBH)2(L)2]

Application de l'étude de la matière organique à l'analyse de l'érosion : exemple du bassin versant du Moulin, dans les terres noires des Alpes-de-Haute-Provence (France) Determination of eroded geological formations using organic matter characterization (Moulin basin, Alpes-de-Haute-Provence, France).

Laboratoire de géochimie organique, UMR 6531, bât. Géosciences, université d'Orléans, 45067 Orléans, France - Laboratoire intégré à l'ISTO UMR6113 - CNRS - Université d'OrléansCe travail s'appuie sur l'étude de la matière organique présente dans les sols, substratum géologique et particules fluviatiles, d'un bassin versant équipé par le Cemagref. L'analyse des palynofaciès confirme la contribution significative de matière organique fossile dans les cours d'eau actuels. La pyrolyse Rock-Eval permet de discriminer les formations géologiques alimentant, soit les charges de fond, soit les matières en suspension, et de préciser leur mode d'érosion. Ainsi, la matière organique, traditionnellement étudiée pour la reconstitution des environnements passés, autorise en outre la caractérisation des formations géologiques érodées et des processus érosifs les ayant affectées. The present study is based on the optical (palynofacies) and geochemical (pyrolyse Rock-Eval) characterization of the organic matter occurring both in bedrock, soils, river sediments (suspended matter and bedload) in a Draix Erosional Research Basin (Cemagref). Results confirm firstly the contribution of reworked organic matter in modern fluxes. Numerous previous studies have shown that organic matter analysis can be an accurate tool to provide information concerning past climates and past environments. Present results suggests that such analysis can also give information concerning the characterization of eroded bedrocks and of erosional processes such as river bank erosion and runoff

Global atmospheric budget of acetaldehyde: 3-D model analysis and constraints from in-situ and satellite observations

We construct a global atmospheric budget for acetaldehyde using a 3-D model of atmospheric chemistry (GEOS-Chem), and use an ensemble of observations to evaluate present understanding of its sources and sinks. Hydrocarbon oxidation provides the largest acetaldehyde source in the model (128 Tg a<sup>−1</sup>, a factor of 4 greater than the previous estimate), with alkanes, alkenes, and ethanol the main precursors. There is also a minor source from isoprene oxidation. We use an updated chemical mechanism for GEOS-Chem, and photochemical acetaldehyde yields are consistent with the Master Chemical Mechanism. We present a new approach to quantifying the acetaldehyde air-sea flux based on the global distribution of light absorption due to colored dissolved organic matter (CDOM) derived from satellite ocean color observations. The resulting net ocean emission is 57 Tg a<sup>−1</sup>, the second largest global source of acetaldehyde. A key uncertainty is the acetaldehyde turnover time in the ocean mixed layer, with quantitative model evaluation over the ocean complicated by known measurement artifacts in clean air. Simulated concentrations in surface air over the ocean generally agree well with aircraft measurements, though the model tends to overestimate the vertical gradient. PAN:NO<sub>x</sub> ratios are well-simulated in the marine boundary layer, providing some support for the modeled ocean source. We introduce the Model of Emissions of Gases and Aerosols from Nature (MEGANv2.1) for acetaldehyde and ethanol and use it to quantify their net flux from living terrestrial plants. Including emissions from decaying plants the total direct acetaldehyde source from the land biosphere is 23 Tg a<sup>−1</sup>. Other terrestrial acetaldehyde sources include biomass burning (3 Tg a<sup>−1</sup>) and anthropogenic emissions (2 Tg a<sup>−1</sup>). Simulated concentrations in the continental boundary layer are generally unbiased and capture the spatial gradients seen in observations over North America, Europe, and tropical South America. However, the model underestimates acetaldehyde levels in urban outflow, suggesting a missing source in polluted air. Ubiquitous high measured concentrations in the free troposphere are not captured by the model, and based on present understanding are not consistent with concurrent measurements of PAN and NO<sub>x</sub>: we find no compelling evidence for a widespread missing acetaldehyde source in the free troposphere. We estimate the current US source of ethanol and acetaldehyde (primary + secondary) at 1.3 Tg a<sup>−1</sup> and 7.8 Tg a<sup>−1</sup>, approximately 60{%} and 480% of the corresponding increases expected for a national transition from gasoline to ethanol fuel

Constant low-to-moderate mechanical asymmetries during 800-m track running

IntroductionModifications in asymmetry in response to self-paced efforts have not been thoroughly documented, particularly regarding horizontally-derived ground reaction force variables. We determined the magnitude and range of gait asymmetries during 800 m track running.MethodsEighteen physical education students completed an 800 m self-paced run on a 200 m indoor track. During the run, vertical and horizontal ground reaction forces were measured at a sampling frequency of 500 Hz using a 5 m-long force platform system, with data collected once per lap. The following mechanical variables were determined for two consecutive steps: contact time and duration of braking/push-off phases along with vertical/braking/push-off peak forces and impulses. The group mean asymmetry scores were evaluated using the “symmetry angle” (SA) formula, where scores of 0% and 100% correspond to perfect symmetry and perfect asymmetry, respectively.ResultsThere was no influence of distance interval on SA scores for any of the nine biomechanical variables (P ≥ 0.095). The SA scores were ∼1%–2% for contact time (1.3 ± 0.5%), peak vertical forces (1.8 ± 0.9%), and vertical impulse (1.7 ± 1.0%). The SA scores were ∼3%–8% for duration of braking (3.6 ± 1.1%) and push-off (3.2 ± 1.4%) phases, peak braking (5.0 ± 2.1%) and push-off (6.9 ± 3.1%) forces as well as braking (7.6 ± 2.3%) and push-off (7.7 ± 3.3%) impulses. The running velocity progressively decreased at 300 m and 500 m compared to that at 100 m but levelled off at 700 m (P < 0.001).DiscussionThere were no modifications in gait asymmetries, as measured at 200-m distance intervals during 800-m track running in physical education students. The 800 m self-paced run did not impose greater mechanical constraints on one side of the body. Experimental procedures for characterizing the gait pattern during 800 m track running could be simplified by collecting leg mechanical data from only one side

Spatial Distribution of Isoprene Emissions from North America Derived from Dormaldehyde Column Measurements by the OMI Satellite Sensor

Space-borne formaldehyde (HCHO) column measurements from the Ozone Monitoring Instrument (OMI), with 13 × 24 km2 nadir footprint and daily global coverage, provide new constraints on the spatial distribution of biogenic isoprene emission from North America. OMI HCHO columns for June-August 2006 are consistent with measurements from the earlier GOME satellite sensor (1996–2001) but OMI is 2–14% lower. The spatial distribution of OMI HCHO columns follows that of isoprene emission; anthropogenic hydrocarbon emissions are undetectable except in Houston. We develop updated relationships between HCHO columns and isoprene emission from a chemical transport model (GEOS-Chem), and use these to infer top-down constraints on isoprene emissions from the OMI data. We compare the OMI-derived emissions to a state-of-science bottom-up isoprene emission inventory (MEGAN) driven by two land cover databases, and use the results to optimize the MEGAN emission factors (EFs) for broadleaf trees (the main isoprene source). The OMI-derived isoprene emissions in North America (June–August 2006) with 1° × 1° resolution are spatially consistent with MEGAN (R2 = 0.48–0.68) but are lower (by 4–25% on average). MEGAN overestimates emissions in the Ozarks and the Upper South. A better fit to OMI (R2 = 0.73) is obtained in MEGAN by using a uniform isoprene EF from broadleaf trees rather than variable EFs. Thus MEGAN may overestimate emissions in areas where it specifies particularly high EFs. Within-canopy isoprene oxidation may also lead to significant differences between the effective isoprene emission to the atmosphere seen by OMI and the actual isoprene emission determined by MEGAN.Earth and Planetary SciencesEngineering and Applied Science

Can a “state of the art” chemistry transport model simulate Amazonian tropospheric chemistry?

We present an evaluation of a nested high-resolution Goddard Earth Observing System (GEOS)-Chem chemistry transport model simulation of tropospheric chemistry over tropical South America. The model has been constrained with two isoprene emission inventories: (1) the canopy-scale Model of Emissions of Gases and Aerosols from Nature (MEGAN) and (2) a leaf-scale algorithm coupled to the Lund-Potsdam-Jena General Ecosystem Simulator (LPJ-GUESS) dynamic vegetation model, and the model has been run using two different chemical mechanisms that contain alternative treatments of isoprene photo-oxidation. Large differences of up to 100 Tg C yr^(−1) exist between the isoprene emissions predicted by each inventory, with MEGAN emissions generally higher. Based on our simulations we estimate that tropical South America (30–85°W, 14°N–25°S) contributes about 15–35% of total global isoprene emissions. We have quantified the model sensitivity to changes in isoprene emissions, chemistry, boundary layer mixing, and soil NO_x emissions using ground-based and airborne observations. We find GEOS-Chem has difficulty reproducing several observed chemical species; typically hydroxyl concentrations are underestimated, whilst mixing ratios of isoprene and its oxidation products are overestimated. The magnitude of model formaldehyde (HCHO) columns are most sensitive to the choice of chemical mechanism and isoprene emission inventory. We find GEOS-Chem exhibits a significant positive bias (10–100%) when compared with HCHO columns from the Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY) and Ozone Monitoring Instrument (OMI) for the study year 2006. Simulations that use the more detailed chemical mechanism and/or lowest isoprene emissions provide the best agreement to the satellite data, since they result in lower-HCHO columns

A public private partnership to fight against malaria along the Chad-Cameroon pipeline corridor: I. Baseline data on socio-anthropological aspects, knowledge, attitudes and practices of the population concerning malaria

BACKGROUND: Malaria is ranked as the major public health problem in Cameroon, representing 50% of illness in less than five year old children, 40-45% of medical consultation and 40% of the annual home income spent on health. The Cameroon Oil Transportation Company (COTCO) that exploits the Chad-Cameroon pipeline in Cameroon territory, initiated in 2010, a public private partnership project to control malaria along the pipeline corridor. A research component was included in the project so as to guide and evaluate the control measures applied in this pipeline corridor. This study presents the baseline socio-anthropological data as well as the knowledge, attitudes and practices of the local population concerning malaria, its transmission, management and prevention. METHODS: A descriptive cross-sectional survey was undertaken in four sentinel sites (one site per ecological zone) along the Chad-Cameroon pipeline corridor. Three structured questionnaires were used for the survey. Two of them were addressed to the heads of households (one for census and the other to collect information concerning the characteristics of houses and living conditions in households as well as their knowledge, attitudes and practices concerning malaria). The last questionnaire was used to collect information on malaria management and prevention. It was addressed to women who had delivered a living child within the past three years. Interviewers were recruited from each village and trained for two consecutive days on how to fill the different questionnaires. All data were analysed at 5% significant level using Epi-Info, SPSS and Cs PRO 4.0 STATA. Values of p ≤ 0.05 were considered statistically significant. RESULTS: Interviews were conducted in 2597 households (Bipindi 399, Bélabo 835, in Meidougou 820 and Dompta 543). Whatever the study site, 50% of the heads of household were workers of the agro-pastoral sector. Most of the heads of household were men (average 77.4% for men and 22.6% for females). The walls of households were mostly made-up of earth blocks and access to media was low. There were significant differences between mean ages and educational level of the heads of household. Significant differences were also observed between the characteristics of houses and the sites located in the southern regions (Bipindi and Bélabo) and those located in the northern regions (Meidougou and Dompta). The later household heads were younger and less educated than those in the other regions. In most of the study sites, paracetamol was cited as the first intention drug for malaria treatment, followed by chloroquine, a banned drug. More than half of the households studied had a correct knowledge of malaria and its mode of transmission: 120/155 (77.1%) in Bipindi, 244/323 (74.5%) in Bélabo, 171/235 (72.8%) in Meidougou and 118/218 (54.1%) in Dompta. Fever and headache were the malaria signs/symptoms most often cited by the households. An important percentage of pregnant women did not take any malaria prophylaxis during their last pregnancy (up to 43.4% in Bélabo). CONCLUSION: In all the study sites, there were conditions that indicated the all year round transmission of malaria (characteristics of houses and limited access to media making sensitization campaigns difficult). In general, most households had a good knowledge of malaria and its mode of transmission. However, malaria treatment drugs were most often inappropriate. In this study, recommendations were made in order to guide the implementation of control measures

Genetically engineered probiotic E. coli Nissle to consume amino acids associated with orphan metabolic diseases

Orphan metabolic diseases are rare genetic defects that interfere with metabolism due to ineffective or missing enzymes. Two of them, Phenylketonuria (PKU) and Maple Syrup Urine Disease (MSUD) are defined by accumulation of amino acids to toxic levels due to defective metabolism of protein break down products. PKU is caused by a defect in the gene encoding phenylalanine hydroxylase (PAH). MSUD is caused by a defect in a multi-enzyme complex found in mitochondria called branched chain ɑ-ketoacid dehydrogenase “BCKDH”. Without the activity of these enzymes, the amino acid phenylalanine (Phe) in the case of PKU or the branched-chain amino acids leucine (Leu), isoleucine and valine for MSUD build up to neurotoxic levels in the blood and brain, leading to neurological deficits. Current treatment options focus on dietary protein restriction, are insufficient and, unfortunately, can lead to a failure to thrive. Lifelong compliance with a prescription diet is also a concern. We have genetically engineered Nissle, a probiotic strain of E. coli, to reduce serum phenylalanine and leucine levels in patients with PKU or MSUD; preclinical data supporting the activity of these strains are described. Please click Additional Files below to see the full abstract

Subthalamic Nucleus Stimulation Affects Theory of Mind Network: A PET Study in Parkinson's Disease

Background: There appears to be an overlap between the limbic system, which is modulated by subthalamic nucleus (STN) deep brain stimulation (DBS) in Parkinson’s disease (PD), and the brain network that mediates theory of mind (ToM). Accordingly, the aim of the present study was to investigate the effects of STN DBS on ToM of PD patients and to correlate ToM modifications with changes in glucose metabolism. Methodology/Principal Findings: To this end, we conducted 18 FDG-PET scans in 13 PD patients in pre- and post-STN DBS conditions and correlated changes in their glucose metabolism with modified performances on the Eyes test, a visual ToM task requiring them to describe thoughts or feelings conveyed by photographs of the eye region. Postoperative PD performances on this emotion recognition task were significantly worse than either preoperative PD performances or those of healthy controls (HC), whereas there was no significant difference between preoperative PD and HC. Conversely, PD patients in the postoperative condition performed within the normal range on the gender attribution task included in the Eyes test. As far as the metabolic results are concerned, there were correlations between decreased cerebral glucos