In situ quantification of CH4 bubbling events from a peat soil using a new infrared laser spectrometer

International audienceCH4 emissions from peatlands are space- and time-dependent. The variety of efflux routes contributes to these variabilities. CH4 bubbling remains difficult to investigate since it occurs on a timescale of seconds. The aims of this study were to test the capacity of a recently built infrared high resolution spectrometer, SPIRIT (SPectrometre Infra-Rouge In situ Troposphérique), to (1) measure in situ CH4 fluxes, (2) observe online bubbling events with quantification of CH4 emission fluxes corresponding to this very sudden degassing event. Material and methods: The closed dynamic chamber method was used and the gas concentration was measured every 1.5 seconds. Emission fluxes were calculated by the accumulation rate of CH4 against time. Measurements were undertaken during daytime in March 2009 and during day- and nighttime in May 2009, in a bare peat area, temporarily forming a shallow pool. Results and discussion: The results show that the CH4 emissions estimated with the SPIRIT ranged from 2.79 to 86.0 mg CH4-C m-2 h-1. These values are consistent with those already published. The high emissions, both through diffusion and bubbling, were on the same order as the emissions estimated in natural shallow pools. During daytime, CH4 bubbling was higher in May (56.2% of the total emission) than in March (40.7%) probably because of increased CH4 production and accumulation in peat. In May, bubbling was higher at nighttime (68.6%) than in daytime (56.2%). This has an important implication for carbon budget assessment in peatlands, particularly in boreal areas. Conclusions: The recently built infrared spectrometer, SPIRIT, was able to reliably measure CH4 fluxes and quantify CH4 flux during the degassing of a bubble. The emissions obtained are in agreement with previously published data using other measurement techniques. The results of this preliminary work highlight (1) the importance of shallow pools in peatland CH4 emissions, (2) the sensitivity of such fluxes to atmospheric pressure, a relation that has not been fully investigated or taken into account in assessing peatland carbon balance

Inhibition of endothelial activation: a new way to treat cerebral malaria?

BACKGROUND: Malaria is still a major public health problem, partly because the pathogenesis of its major complication, cerebral malaria (CM), remains incompletely understood. However tumor necrosis factor (TNF) is thought to play a key role in the development of this neurological syndrome, as well as lymphotoxin alpha (LT). METHODS AND FINDINGS: Using an in vitro model of CM based on human brain-derived endothelial cells (HBEC-5i), we demonstrate the anti-inflammatory effect of LMP-420, a 2-NH2-6-Cl-9-[(5-dihydroxyboryl)-pentyl] purine that is a transcriptional inhibitor of TNF. When added before or concomitantly to TNF, LMP-420 inhibits endothelial cell (EC) activation, i.e., the up-regulation of both ICAM-1 and VCAM-1 on HBEC-5i surfaces. Subsequently, LMP-420 abolishes the cytoadherence of ICAM-1-specific Plasmodium falciparum-parasitized red blood cells on these EC. Identical but weaker effects are observed when LMP-420 is added with LT. LMP-420 also causes a dramatic reduction of HBEC-5i vesiculation induced by TNF or LT stimulation, as assessed by microparticle release. CONCLUSION: These data provide evidence for a strong in vitro anti-inflammatory effect of LMP-420 and suggest that targeting host cell pathogenic mechanisms might provide a new therapeutic approach to improving the outcome of CM patients

INTRUSION OF RECENT AIR IN POLAR STRATOSPHERE DURING SUMMER 2009 REVEALED BY BALLOON-BORNE IN SITU CO MEASUREMENTS

International audienceThe SPIRALE (Spectroscopie Infa-Rouge par Absorption de Lasers Embarqués) balloon-borne instrument has been launched twice within 17 days in the polar region (Kiruna, Sweden, 67.9°N-21.1°E) during summer, at the beginning and at the end of August 2009. In situ measurements of several trace gases have been performed including CO and O 3 between 10 and 34 km height, with very high vertical resolution (~5 m). The both flight results are compared and the CO stratospheric profile of the first flight presents specific structures associated with mid-latitude intrusion in the lowest stratospheric levels. Their interpretation is made with the help of results from several modeling tools (MIMOSA and FLEXTRA) and available satellite data (IASI). We also used the O 3 profile correlated with CO to calculate the proportion of recent air in the polar stratosphere. The results indicate the impact of East Asia urban pollution on the chemistry of polar stratosphere in summer

Family planning: formal health care providers’ challenges in the district of Antananarivo Avaradrano

Background: Recorded contraceptive prevalence may not represent all the women using contraceptives. Nevertheless, it serves as a fundamental tool in decision-making at Ministry and international level. This study aims to determine the actual contraceptive prevalence and identify factors determining users’ positions about modern contraception and local services deliveries in the district of Antananarivo Avaradrano.Methods: A cross-sectional survey was conducted, where an interviewer-administered questionnaire has been used to collect data. Targeted female respondents aged 18-39 were asked about their contraceptive use, knowledge and information sources on family planning, perception of social support and perception on the local health care providers.Results: Contraceptive prevalence is underestimated. Moreover, it is higher among women aged 35 to 39 and those having two children or more, but lower among those who have reached university level of education. Women who are able to tell two benefits of family planning, informed by the community health agents (CHA), and deciding with their partners on contraception use are more likely to use contraceptives on a regular basis. Women complain on their poor relationship with health care providers and doubt about their real competence.Conclusions: This study demonstrates the evidence of an underestimation of contraceptive prevalence. The challenge is how to collect reliable data, thus recording systems have to be improved. Besides, government efforts in increasing contraceptive use ought to be targeted on adolescents and young people aged 20-25, the couple itself, health-care provider – woman relationship, and on the CHA’s activities.

Self-medication with oral contraceptives in the Urban District of Antananarivo

Background: Oral contraception is the second hormonal contraceptive method most used in the world. Currently, self-medication with oral contraceptives experienced resurgence, most often with no medical supervision. This study aims to estimate the prevalence of self-medication with oral contraceptives, identify the socio-economic status and identify the reasons why women aged 21 to 49 of the Urban District of Antananarivo (UDA) practice self-medication with oral contraceptives.Methods: A cross-sectional survey was conducted, where an interviewer-administered questionnaire has been used to collect data. Targeted female respondents aged 21-49 were asked about their contraceptive use during the twelve months preceding the survey.Results: Self-medication prevalence rate is 59.1%, considering oral contraception users. Moreover, it is higher among married women, those aged <36, less educated and having more than two children. Financial problem, affordability of the pills, former use of pills and information by their surroundings are the reasons why women self-medicate. Women who received a medical prescription at the first take of the pills are more likely to presently practice self-medication.Conclusions: This study demonstrates the evidence of a high prevalence of self-medication in the UDA. Self-medication can be harmful: the fight against its risks should get reinforced

Solvent contribution to the stability of a physical gel characterized by quasi-elastic neutron scattering

The dynamics of a physical gel, namely the Low Molecular Mass Organic Gelator {\textit Methyl-4,6-O-benzylidene-$\alpha$ -D-mannopyranoside ($\alpha$-manno)} in water and toluene are probed by neutron scattering. Using high gelator concentrations, we were able to determine, on a timescale from a few ps to 1 ns, the number of solvent molecules that are immobilised by the rigid network formed by the gelators. We found that only few toluene molecules per gelator participate to the network which is formed by hydrogen bonding between the gelators' sugar moieties. In water, however, the interactions leading to the gel formations are weaker, involving dipolar, hydrophobic or $\pi-\pi$ interactions and hydrogen bonds are formed between the gelators and the surrounding water. Therefore, around 10 to 14 water molecules per gelator are immobilised by the presence of the network. This study shows that neutron scattering can give valuable information about the behaviour of solvent confined in a molecular gel.Comment: Langmuir (2015

Giant capsids from lattice self-assembly of cyclodextrin complexes

Proteins can readily assemble into rigid, crystalline and functional structures such as viral capsids and bacterial compartments. Despite ongoing advances, it is still a fundamental challenge to design and synthesize protein-mimetic molecules to form crystalline structures. Here we report the lattice self-assembly of cyclodextrin complexes into a variety of capsidlike structures such as lamellae, helical tubes and hollow rhombic dodecahedra. The dodecahedral morphology has not hitherto been observed in self-assembly systems. The tubes can spontaneously encapsulate colloidal particles and liposomes. The dodecahedra and tubes are respectively comparable to and much larger than the largest known virus. In particular, the resemblance to protein assemblies is not limited to morphology but extends to structural rigidity and crystallinity-a well-defined, 2D rhombic lattice of molecular arrangement is strikingly universal for all the observed structures. We propose a simple design rule for the current lattice self-assembly, potentially opening doors for new protein-mimetic materials