2,417 research outputs found

    Ground-based FTIR measurements of CO from the Jungfraujoch: characterisation and comparison with <i>in situ</i> surface andMOPITT data

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    International audienceCO vertical profiles have been retrieved from solar absorption FTIR spectra recorded at the NDSC station of the Jungfraujoch (46.5° N, 8° E and 3580 m a.s.l.) for the period from January 1997 to May 2001. The characterisation of these profiles has been established by an information content analysis and an estimation of the error budgets. A partial validation of the profiles has been performed through comparisons with correlative measurements. The average volume mixing ratios (vmr) in the 3 km layer above the station have been compared with coincident surface measurements. The agreement between monthly means from both measurement techniques is very good, with a correlation coefficient of 0.87, and no significant bias observed. The FTIR total columns have also been compared to CO partial columns above 3580 m a.s.l. derived from the MOPITT (Measurement Of Pollution In The Troposphere) instrument for the period March 2000 to May 2001. Relative to the FTIR columns, the MOPITT partial columns exhibit a positive bias of 8±8% for daytime and of 4±7% for nighttime measurements

    Productivity of Intensive Grazing Systems Based upon Irrigated Pangola Pastures in the French West Indies

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    This work deals with the comparison of the productivity of intensive grazing systems (IGS) in the French West Indies, used for meat production with cattle, goat and sheep. IGS are based upon the use of irrigated, fertilized, and high stocked (1.8 to 1.4 t live weight/ha/year) and rotational grazing Digitaria decumbens pastures. They lie upon good performance levels of local breeds, Creole cattle and Creole goats of Guadeloupe and Martinik ewes, and upon improved general husbandry. Both sheep and goat in IGS exhibit high levels of productivity. They reached up to 1000 kg LW of weaned offsprings and 1400 kg LW of fattened offsprings per ha and per year. Results for cattle were 522 and 1061 kg LW, respectively. The relative interests of species are presented with the aim of increasing meat production in the tropical zone and in limited land resource conditions

    Bar coding MS2 spectra for metabolite identification

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    [Image: see text] Metabolite identifications are most frequently achieved in untargeted metabolomics by matching precursor mass and full, high-resolution MS(2) spectra to metabolite databases and standards. Here we considered an alternative approach for establishing metabolite identifications that does not rely on full, high-resolution MS(2) spectra. First, we select mass-to-charge regions containing the most informative metabolite fragments and designate them as bins. We then translate each metabolite fragmentation pattern into a binary code by assigning 1’s to bins containing fragments and 0’s to bins without fragments. With 20 bins, this binary-code system is capable of distinguishing 96% of the compounds in the METLIN MS(2) library. A major advantage of the approach is that it extends untargeted metabolomics to low-resolution triple quadrupole (QqQ) instruments, which are typically less expensive and more robust than other types of mass spectrometers. We demonstrate a method of acquiring MS(2) data in which the third quadrupole of a QqQ instrument cycles over 20 wide isolation windows (coinciding with the location and width of our bins) for each precursor mass selected by the first quadrupole. Operating the QqQ instrument in this mode yields diagnostic bar codes for each precursor mass that can be matched to the bar codes of metabolite standards. Furthermore, our data suggest that using low-resolution bar codes enables QqQ instruments to make MS(2)-based identifications in untargeted metabolomics with a specificity and sensitivity that is competitive to high-resolution time-of-flight technologies

    VUV and X-ray coherent light with tunable polarization from single-pass free-electron lasers

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    Tunable polarization over a wide spectral range is a required feature of light sources employed to investigate the properties of local symmetry in both condensed and low-density matter. Among new-generation sources, free-electron lasers possess a unique combination of very attractive features, as they allow to generate powerful and coherent ultra-short optical pulses in the VUV and X-ray spectral range. However, the question remains open about the possibility to freely vary the light polarization of a free-electron laser, when the latter is operated in the so-called nonlinear harmonic-generation regime. In such configuration, one collects the harmonics of the free-electron laser fundamental emission, gaining access to the shortest possible wavelengths the device can generate. In this letter we provide the first experimental characterization of the polarization of the harmonic light produced by a free-electron laser and we demonstrate a method to obtain tunable polarization in the VUV and X-ray spectral range. Experimental results are successfully compared to those obtained using a theoretical model based on the paraxial solution of Maxwell's equations. Our findings can be expected to have a deep impact on the design and realization of experiments requiring full control of light polarization to explore the symmetry properties of matter samples

    Towards understanding the variability in biospheric CO2 fluxes:Using FTIR spectrometry and a chemical transport model to investigate the sources and sinks of carbonyl sulfide and its link to CO2

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    Understanding carbon dioxide (CO2) biospheric processes is of great importance because the terrestrial exchange drives the seasonal and interannual variability of CO2 in the atmosphere. Atmospheric inversions based on CO2 concentration measurements alone can only determine net biosphere fluxes, but not differentiate between photosynthesis (uptake) and respiration (production). Carbonyl sulfide (OCS) could provide an important additional constraint: it is also taken up by plants during photosynthesis but not emitted during respiration, and therefore is a potential means to differentiate between these processes. Solar absorption Fourier Transform InfraRed (FTIR) spectrometry allows for the retrievals of the atmospheric concentrations of both CO2 and OCS from measured solar absorption spectra. Here, we investigate co-located and quasi-simultaneous FTIR measurements of OCS and CO2 performed at five selected sites located in the Northern Hemisphere. These measurements are compared to simulations of OCS and CO2 using a chemical transport model (GEOS-Chem). The coupled biospheric fluxes of OCS and CO2 from the simple biosphere model (SiB) are used in the study. The CO2 simulation with SiB fluxes agrees with the measurements well, while the OCS simulation reproduced a weaker drawdown than FTIR measurements at selected sites, and a smaller latitudinal gradient in the Northern Hemisphere during growing season when comparing with HIPPO (HIAPER Pole-to-Pole Observations) data spanning both hemispheres. An offset in the timing of the seasonal cycle minimum between SiB simulation and measurements is also seen. Using OCS as a photosynthesis proxy can help to understand how the biospheric processes are reproduced in models and to further understand the carbon cycle in the real world

    Multi-Color Imaging of Magnetic Co/Pt Multilayers

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    We demonstrate for the first time the realization of a spatial resolved two color, element-specific imaging experiment at the free-electron laser facility FERMI. Coherent imaging using Fourier transform holography was used to achieve direct real space access to the nanometer length scale of magnetic domains of Co/Pt heterostructures via the element-specific magnetic dichroism in the extreme ultraviolet spectral range. As a first step to implement this technique for studies of ultrafast phenomena we present the spatially resolved response of magnetic domains upon femtosecond laser excitation