Graphene in silicon photovoltaic cells

Graphene is an allotrope of carbon. Its structure is one-atom-thick planar sheets of carbon atoms that are densely packed in a honeycomb crystal lattice [1]. The richness of optical and electronic properties of graphene attracts enormous interest. Its true potential seems to be in photonics and optoelectronics, where the combination of its unique optical and electronic properties can be fully exploited. The optical absorption of graphene layers is proportional to the number of layers, each absorbing A=1-T=πα=2.3% over the visible spectrum [2].The rise of graphene in photonics and optoelectronics is shown by several recent results, ranging from solar cells and light emitting devices, to touch screens, photodetectors and ultrafast lasers. Current photovoltaic (PV) technology is dominated by Si cells, with an energy conversion coefficient up to 25% [3]. Such an inorganic PV consists in a current transparent conductor (TC) replacing one of the electrodes of a PIN photodiode. The standard material used so far for these electrodes is indium-tinoxide, or ITO. But indium is expensive and relatively rare, so the search has been on for a suitable replacement. A possible substitute made from inexpensive and ubiquitous carbon is graphene. Being only constituted of carbon, it will become cheap and easily recyclable. But at the moment, the major difficulty consists in its fabrication and/or transfer. Our project consists in synthetizing graphene by CVD (Chemical Vapor Deposition) on Cu and in transferring the obtained layer on silicon PV cells, and then in testing their energy conversion efficiency

Electrostatic Directed Assembly of Colloidal Microparticles Assisted by Convective Flow

International audienceElectrostatic directed assembly of colloidal particles on charged patterns, that is, nanoxerography, has proven to find innovative applications in plasmonics, anticounterfeiting, or particle sorting. However, this technique was restricted to dispersions of nanoparticles whose diameters are typically below 100 nm. The combination of experiments and simulations shows that this limitation is due to an uncontrolled dewetting of the substrate and to the low mobility of large particles. The “convective nanoxerography” process developed in this work overcomes this limit and allows making selective and dense assemblies of micrometer-sized particles expanding by a factor 40 the size range foreseeable

Monitoring elderly activities at home

International audienceThe elderly population is expected to grow dramatically over the next 20 years. As people grow older, they need more healthcare assistance. Without receiving sufficient care, elderly are at risk of loosing their autonomy. Thus a system permitting elderly to live safely at home is more than needed. Medical professionals believe that one of the best ways to detect emerging physical and mental health problems (before it becomes critical – particularly for the elderly) is to look for changes in their activities of daily living (ADLs). For this purpose, we propose a monitoring system which aims at detecting activities of daily living (ADLs) at home

From petrochemical polyurethanes to biobased polyhydroxyurethanes

From a green and sustainable chemistry standpoint, the current challenge in the polyurethane's industry is to switch from petrobased polyurethanes (PUs) to biobased polyhydroxyurethanes (PHUs). This review describes the main alternative strategies being developed with a focus on PHUs from vegetable oils and derivatives. The substitution of petrobased polyols by natural oil based polyols was the first route to biobased PUs to be developed. The second strategy involves synthesis without the need of harmful isocyanate by the nucleophilic polyaddition of polyamines to polycyclic carbonates. The technological barrier to the synthesis of biobased cyclic carbonates could be overcome by the chemical transformation of epoxidized vegetable oils or by the use of glycerine carbonate-based intermediates. New families of biobased PHUs with a lower environmental footprint could be generated

Effective ecosystem monitoring requires a multi-scaled approach

Ecosystem monitoring is fundamental to our understanding of how ecosystem change is impacting our natural resources and is vital for developing evidence-based policy and management. However, the different types of ecosystem monitoring, along with their recommended applications, are often poorly understood and contentious. Varying definitions and strict adherence to a specific monitoring type can inhibit effective ecosystem monitoring, leading to poor program development, implementation and outcomes. In an effort to develop a more consistent and clear understanding of ecosystem monitoring programs, we here review the main types of monitoring and recommend the widespread adoption of three classifications of monitoring, namely, targeted, surveillance and landscape monitoring. Landscape monitoring is conducted over large areas, provides spatial data, and enables questions relating to where and when ecosystem change is occurring to be addressed. Surveillance monitoring uses standardised field methods to inform on what is changing in our environments and the direction and magnitude of that change, whilst targeted monitoring is designed around testable hypotheses over defined areas and is the best approach for determining the causes of ecosystem change. The classification system is flexible and can incorporate different interests, objectives, targets and characteristics as well as different spatial scales and temporal frequencies, while also providing valuable structure and consistency across distinct ecosystem monitoring programs. To support our argument, we examine the ability of each monitoring type to inform on six key types of questions that are routinely posed for ecosystem monitoring programs, such as where and when change is occurring, what is the magnitude of change, and how can the change be managed? As we demonstrate, each type of ecosystem monitoring has its own strengths and weaknesses, which should be carefully considered relative to the desired results. Using this scheme, scientists and land managers can design programs best suited to their needs. Finally, we assert that for our most serious environmental challenges, it is essential that we include information from each of these monitoring scales to inform on all facets of ecosystem change, and this is best achieved through close collaboration between the scales. With a renewed understanding of the importance of each monitoring type, along with greater commitment to monitor cooperatively, we will be well placed to address some of our greatest environmental challenges

A Computer system to monitor older adults at home: Preliminary results

International audienceDetermining the individual transition from the 3rd to the 4th of frailty phase of life is important for both the safety of the older person and to support the care provider. We developed an automatic monitoring system consisting of cameras and different sensors that analyze human behaviors and looks for changes in their activities by detecting the presence of people, their movements, and automatically recognizing events and Activities of Daily Living (ADLs). Assessment took place in a laboratory environment (GERHOME) comprised of four rooms (kitchen, living-room, bedroom, and bathroom). Data from 2 volunteers (64 and 85 years old) were analyzed. Precision in recognizing postures and events ranged from 62-94%, while sensitivity fell in the range of 62-87%. The system could differentiate ADL levels for the 64 and 85 year old subjects. These results are promising and merit replication and extension. Considerable work remains before the complete transition from 3rd to 4th life phase can be reliably detected. The GERHOME system is promising in this respect

World Antimalarial Resistance Network I: Clinical efficacy of antimalarial drugs

The proliferation of antimalarial drug trials in the last ten years provides the opportunity to launch a concerted global surveillance effort to monitor antimalarial drug efficacy. The diversity of clinical study designs and analytical methods undermines the current ability to achieve this. The proposed World Antimalarial Resistance Network (WARN) aims to establish a comprehensive clinical database from which standardised estimates of antimalarial efficacy can be derived and monitored over time from diverse geographical and endemic regions. The emphasis of this initiative is on five key variables which define the therapeutic response. Ensuring that these data are collected at the individual patient level in a consistent format will facilitate better data management and analytical practices, and ensure that clinical data can be readily collated and made amenable for pooled analyses. Such an approach, if widely adopted will permit accurate and timely recognition of trends in drug efficacy. This will guide not only appropriate interventions to deal with established multidrug resistant strains of malaria, but also facilitate prompt action when new strains of drug resistant plasmodia first emerge. A comprehensive global database incorporating the key determinants of the clinical response with in vitro, molecular and pharmacokinetic parameters will bring together relevant data on host, drug and parasite factors that are fundamental contributors to treatment efficacy. This resource will help guide rational drug policies that optimize antimalarial drug use, in the hope that the emergence and spread of resistance to new drugs can be, if not prevented, at least delayed

Estimating Attributable Mortality Due to Nosocomial Infections Acquired in Intensive Care Units

Background. The strength of the association between intensive care unit (ICU)-acquired nosocomial infections (NIs) and mortality might differ according to the methodological approach taken. Objective. TO assess the association between ICU-acquired NIs and mortality using the concept of population-attributable fraction (PAF) for patient deaths caused by ICU-acquired NIs in a large cohort of critically ill patients. Setting. Eleven ICUs of a French university hospital. Design. We analyzed surveillance data on ICU-acquired NIs collected prospectively during the period from 1995 through 2003. The primary outcome was mortality from ICU-acquired NI stratified by site of infection. A matched-pair, case-control study was performed. Each patient who died before ICU discharge was defined as a case patient, and each patient who survived to ICU discharge was denned as a control patient. The PAF was calculated after adjustment for confounders by use of conditional logistic regression analysis. Results. Among 8,068 ICU patients, a total of 1,725 deceased patients were successfully matched with 1,725 control Patients. The adjusted PAF due to ICU-acquired NI for patients who died before ICU discharge was 14.6% (95% confidence interval [CI], 14.4%—14.8%). Stratified by the type of infection, the PAF was 6.1% (95% CI, 5.7%-6.5%) for pulmonary infection, 3.2% (95% CI, 2.8%-3.5%) for central venous catheter infection, 1.7% (95% CI, 0.9%-2.5%) for bloodstream infection, and 0.0% (95% CI, -0.4% to 0.4%) for urinary tract infection. Conclusions. ICU-acquired NI had an important effect on mortality. However, the statistical association between ICU-acquired NI and mortality tended to be less pronounced in findings based on the PAF than in study findings based on estimates of relative risk. Therefore, the choice of methods does matter when the burden of NI needs to be assesse

Molecular epidemiology of multidrug-resistant Shigella dysenteriae type 1 causing dysentery outbreaks in Central African Republic, 2003-2004.

Shigella dysenteriae type 1 (Sd1) represents a particular threat in developing countries because of the severity of the infection and its epidemic potential. Antimicrobial susceptibility testing and molecular subtyping by pulsed-field gel electrophoresis (PFGE) and plasmid profiling (PP) of Sd1 isolates collected during two dysentery outbreaks (2013 and 445 cases of bloody diarrhoea) in Central African Republic (CAR) during the period 2003-2004 were reported. Eleven Sd1 comparison strains (CS) acquired by travellers or residents of Africa (n=10) or Asia (n=1) between 1993 and 2003 were also analysed. The 19 Sd1 isolates recovered from CAR outbreaks were multidrug resistant, although susceptible to quinolones and fluoroquinolones. Molecular subtyping by PFGE was more discriminatory than PP. The PFGE using XbaI and NotI restriction enzymes indicated that the two outbreaks were due to two different clones and also revealed a genetic diversity among the CS recovered from outbreak or sporadic cases between 1993 and 2003. This study was the result of a fruitful collaboration between field physicians and microbiologists. The data collected will serve as the basis for establishing long-term monitoring of Sd1 in CAR

PALÉORIVAGES, DUNES CÔTIÈRES ET OCCUPATIONS HUMAINES À L’EMBOUCHURE DE L’OUED TAMRI, MAROC ATLANTIQUE, AU PLÉISTOCÈNE SUPÉRIEUR (SIM 5)

A l’embouchure de l’oued Tamri, rive gauche, un paléorivage de faciès marin et fluvio-marin (unité U1) culmine aux environs de + 6m a.s.l. Une coquille marine de Patella sp. prélevée dans cette unité U1 (faciès marin) a été datée 100,02 ± 1,662 ka et 101,188 ±  1,339 ka par la méthode U/Th (SIM 5.3). La dune surincombante (série Sx) a été datée par OSL 84 ± 4 ka (SIM 5.1). A Tighrine Imksawne, à 200 m au Sud de l’embouchure, ce paléorivage est surmonté d’une séquence de dépôts dunaires et colluviaux de plus de 20 m d’épaisseur. Ces derniers renferment plusieurs paléosols rubéfiés interstratifiés et des encroûtements, témoins de périodes humides et de ruissellements, qui permettent de distinguer trois unités principales (unités U2, U3, U4) :(U2), unité d’accumulation interdunaire inférieure, où dominent les faciès détritiques continentaux de colluvionnement/ruissellement, avec de nombreux Hélicidés et de rares témoins d’outillage lithique. (U3), unité d’accumulation éolienne moyenne, à séries dunaires encroûtées, où la série (S5) a été datée par OSL 92 ± 6 ka (SIM 5.3 ou SIM 5.2), et où le paléosol rubéfié (S6) a fourni une industrie à proto-hachereaux. (U4), unité d’accumulation éolienne supérieure à séries friables, séparée de la précédente par une paléo-surface encroûtée (S6/S7) à industrie probablement épipaléolithique, et où des coquilles d’œufs d’Autruche de la série (S8) sont datées par radiocarbone à plus de 30 ka. BPLes analyses géomorphologiques, sédimentologiques et pétrographiques aboutissent à un modèle sédimentaire d’accumulation de pied de falaise morte qui permet de répondre aux contradictions apparentes entre la position de l’industrie lithique et des datations.A l’embouchure de l’oued Tamri, rive gauche, un paléorivage de faciès marin et fluvio-marin (unité U1) culmine aux environs de + 6m a.s.l. Une coquille marine de Patella sp. prélevée dans cette unité U1 (faciès marin) a été datée 100,02 ± 1,662 ka et 101,188 ±  1,339 ka par la méthode U/Th (SIM 5.3). La dune surincombante (série Sx) a été datée par OSL 84 ± 4 ka (SIM 5.1). A Tighrine Imksawne, à 200 m au Sud de l’embouchure, ce paléorivage est surmonté d’une séquence de dépôts dunaires et colluviaux de plus de 20 m d’épaisseur. Ces derniers renferment plusieurs paléosols rubéfiés interstratifiés et des encroûtements, témoins de périodes humides et de ruissellements, qui permettent de distinguer trois unités principales (unités U2, U3, U4) :(U2), unité d’accumulation interdunaire inférieure, où dominent les faciès détritiques continentaux de colluvionnement/ruissellement, avec de nombreux Hélicidés et de rares témoins d’outillage lithique. (U3), unité d’accumulation éolienne moyenne, à séries dunaires encroûtées, où la série (S5) a été datée par OSL 92 ± 6 ka (SIM 5.3 ou SIM 5.2), et où le paléosol rubéfié (S6) a fourni une industrie à proto-hachereaux. (U4), unité d’accumulation éolienne supérieure à séries friables, séparée de la précédente par une paléo-surface encroûtée (S6/S7) à industrie probablement épipaléolithique, et où des coquilles d’œufs d’Autruche de la série (S8) sont datées par radiocarbone à plus de 30 ka. BPLes analyses géomorphologiques, sédimentologiques et pétrographiques aboutissent à un modèle sédimentaire d’accumulation de pied de falaise morte qui permet de répondre aux contradictions apparentes entre la position de l’industrie lithique et des datations