533 research outputs found
Ion Mobility Spectrometry in Food Analysis: Principles, Current Applications and Future Trends
In the last decade, ion mobility spectrometry (IMS) has reemerged as an analytical separation
technique, especially due to the commercialization of ion mobility mass spectrometers. Its applicability
has been extended beyond classical applications such as the determination of chemical warfare agents
and nowadays it is widely used for the characterization of biomolecules (e.g., proteins, glycans, lipids,
etc.) and, more recently, of small molecules (e.g., metabolites, xenobiotics, etc.). Following this trend,
the interest in this technique is growing among researchers from different fields including food science.
Several advantages are attributed to IMS when integrated in traditional liquid chromatography
(LC) and gas chromatography (GC) mass spectrometry (MS) workflows: (1) it improves method
selectivity by providing an additional separation dimension that allows the separation of isobaric and
isomeric compounds; (2) it increases method sensitivity by isolating the compounds of interest from
background noise; (3) and it provides complementary information to mass spectra and retention time,
the so-called collision cross section (CCS), so compounds can be identified with more confidence,
either in targeted or non-targeted approaches. In this context, the number of applications focused on
food analysis has increased exponentially in the last few years. This review provides an overview of
the current status of IMS technology and its applicability in different areas of food analysis (i.e., food
composition, process control, authentication, adulteration and safety).M.H.-M. was granted a postdoctoral fellowship (University Research Plan, Program “Perfeccionamiento
de doctores en el extranjero 2017”) by the University of Granada (Spain)
The SPHERE data center: a reference for high contrast imaging processing
The objective of the SPHERE Data Center is to optimize the scientific return
of SPHERE at the VLT, by providing optimized reduction procedures, services to
users and publicly available reduced data. This paper describes our motivation,
the implementation of the service (partners, infrastructure and developments),
services, description of the on-line data, and future developments. The SPHERE
Data Center is operational and has already provided reduced data with a good
reactivity to many observers. The first public reduced data have been made
available in 2017. The SPHERE Data Center is gathering a strong expertise on
SPHERE data and is in a very good position to propose new reduced data in the
future, as well as improved reduction procedures.Comment: SF2A proceeding
Kinetics of photoelectrochemical oxidation of methanol on hematite photoanodes
The kinetics of photoelectrochemical (PEC) oxidation of methanol, as a model organic substrate, on α-Fe2O3 photoanodes are studied using photoinduced absorption spectroscopy and transient photocurrent measurements. Methanol is oxidized on α-Fe2O3 to formaldehyde with near unity Faradaic efficiency. A rate law analysis under quasi-steady-state conditions of PEC methanol oxidation indicates that rate of reaction is second order in the density of surface holes on hematite and independent of the applied potential. Analogous data on anatase TiO2 photoanodes indicate similar second-order kinetics for methanol oxidation with a second-order rate constant 2 orders of magnitude higher than that on α-Fe2O3. Kinetic isotope effect studies determine that the rate constant for methanol oxidation on α-Fe2O3 is retarded ∼20-fold by H/D substitution. Employing these data, we propose a mechanism for methanol oxidation under 1 sun irradiation on these metal oxide surfaces and discuss the implications for the efficient PEC methanol oxidation to formaldehyde and concomitant hydrogen evolution
A narrow, edge-on disk resolved around HD 106906 with SPHERE
HD~106906AB is so far the only young binary system around which a planet has
been imaged and a debris disk evidenced thanks to a strong IR excess. As such,
it represents a unique opportunity to study the dynamics of young planetary
systems. We aim at further investigating the close (tens of au scales)
environment of the HD~106906AB system. We used the extreme AO fed, high
contrast imager SPHERE recently installed on the VLT to observe HD~106906. Both
the IRDIS imager and the Integral Field Spectrometer were used. We discovered a
very inclined, ring-like disk at a distance of 65~au from the star. The disk
shows a strong brightness asymmetry with respect to its semi-major axis. It
shows a smooth outer edge, compatible with ejection of small grains by the
stellar radiation pressure. We show furthermore that the planet's projected
position is significantly above the disk's PA. Given the determined disk
inclination, it is not excluded though that the planet could still orbit within
the disk plane if at a large separation (2000--3000 au). We identified several
additional point sources in the SPHERE/IRDIS field-of-view, that appear to be
background objects. We compare this system with other debris disks sharing
similarities, and we briefly discuss the present results in the framework of
dynamical evolution.Comment: 7 pages, 6 figures, accepted by Astronomy & Astrophysic
IRDIS, the dual-band imager camera of SPHERE: testing the performances in laboratory
Next year the second generation instrument SPHERE will begin science
operations at the Very Large Telecope (ESO). This instrument will be dedicated
to the search for exoplanets through the direct imaging techniques, with the
new generation extreme adaptive optics. In this poster, we present the
performances of one of the focal instruments, the Infra-Red Dual-beam Imaging
and Spectroscopy (IRDIS). All the results have been obtained with tests in
laboratory, simulating the observing conditions in Paranal. We tested several
configurations using the sub-system Integral Field Spectrograph (IFS) in
parallel and simulating long coronographic exposures on a star, calibrating
instrumental ghosts, checking the performance of the adaptive optics system and
reducing data with the consortium pipeline. The contrast one can reach with
IRDIS is of the order of 2\times 10^{-6}$ at 0.5 arcsec separation from the
central star.Comment: 2 pages, 1 figure, IAU Symposium n 299 proceeding
Rate law analysis of water oxidation and hole scavenging on a BiVO4 photoanode
Spectroelectrochemical studies employing pulsed LED irradiation are used to investigate the kinetics of water oxidation on undoped dense bismuth vanadate (BiVO4) photoanodes under conditions of photoelectrochemical water oxidation and compare to those obtained for oxidation of a simple redox couple. These measurements are employed to determine the quasi-steady-state densities of surface-accumulated holes, ps, and correlate these with photocurrent density as a function of light intensity, allowing a rate law analysis of the water oxidation mechanism. The reaction order in surface hole density is found to be first order for ps 1 nm–2. The effective turnover frequency of each surface hole is estimated to be 14 s–1 at AM 1.5 conditions. Using a single-electron redox couple, potassium ferrocyanide, as the hole scavenger, only the first-order reaction is observed, with a higher rate constant than that for water oxidation. These results are discussed in terms of catalysis by BiVO4 and implications for material design strategies for efficient water oxidation
Divergent leukaemia subclones as cellular models for testing vulnerabilities associated with gains in chromosomes 7, 8 or 18
Haematopoietic malignancies are frequently characterized by karyotypic abnormalities. The development of targeted drugs has been pioneered with compounds against gene products of fusion genes caused by chromosomal translocations. While polysomies are equally frequent as translocations, for many of them we are lacking therapeutic approaches aimed at synthetic lethality. Here, we report two new cell lines, named MBU-7 and MBU-8, that differ in complete trisomy of chromosome18, a partial trisomy of chromosome 7 and a tetrasomy of the p-arm of chromosome 8, but otherwise share the same mutational pattern and complex karyotype. Both cell lines are divergent clones of U-937 cells and have the morphology and immunoprofile of monocytic cells. The distinct karyotypic differences between MBU-7 and MBU-8 are associated with a difference in the specific response to nucleoside analogues. Taken together, we propose the MBU-7 and MBU-8 cell lines described here as suitable in vitro models for screening and testing vulnerabilities that are associated with the disease-relevant polysomies of chromosome 7, 8 and 18
SPHERE: the exoplanet imager for the Very Large Telescope
Observations of circumstellar environments to look for the direct signal of
exoplanets and the scattered light from disks has significant instrumental
implications. In the past 15 years, major developments in adaptive optics,
coronagraphy, optical manufacturing, wavefront sensing and data processing,
together with a consistent global system analysis have enabled a new generation
of high-contrast imagers and spectrographs on large ground-based telescopes
with much better performance. One of the most productive is the
Spectro-Polarimetic High contrast imager for Exoplanets REsearch (SPHERE)
designed and built for the ESO Very Large Telescope (VLT) in Chile. SPHERE
includes an extreme adaptive optics system, a highly stable common path
interface, several types of coronagraphs and three science instruments. Two of
them, the Integral Field Spectrograph (IFS) and the Infra-Red Dual-band Imager
and Spectrograph (IRDIS), are designed to efficiently cover the near-infrared
(NIR) range in a single observation for efficient young planet search. The
third one, ZIMPOL, is designed for visible (VIR) polarimetric observation to
look for the reflected light of exoplanets and the light scattered by debris
disks. This suite of three science instruments enables to study circumstellar
environments at unprecedented angular resolution both in the visible and the
near-infrared. In this work, we present the complete instrument and its on-sky
performance after 4 years of operations at the VLT.Comment: Final version accepted for publication in A&
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