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See detailIon beam figuring of small BK7 and Zerodur optics : thermal effects
Gailly, Patrick ULg; Collette, Jean-Paul; Renson, Luc et al

in Geyl, Roland; Maxwell, Jonathan (Eds.) Optical Fabrication and Testing, Proc. SPIE Volume: 3739 (1999, September 06)

optics these last years. One of the disadvantages of ion figuring is the high surface temperature of the workpiece. Temperature aspects have already been mentioned by some authors but are weakly detailed ... [more ▼]

optics these last years. One of the disadvantages of ion figuring is the high surface temperature of the workpiece. Temperature aspects have already been mentioned by some authors but are weakly detailed. Therefore thermal effects on BK7 and Zerodur, mainly surface figure distortions and surface temperature measurements, have been investigated here in more detail. Distortion of the optical figure due to high temperature and temperature gradients induced by ion figuring is described. High figure distortion has been observed on 10 cm diameter BK7 samples. Distortions can also be observed on Zerodur samples (although much weaker). Differences between BK7 and Zerodur distortions are discussed. In order to analyse the nonuniform heating of the workpiece during ion bombardment, the surface temperature has been monitored with an infrared camera. Furthermore, surface temperature measurements with respect to ion beam parameters have also been performed. All these measurements show the necessity to care about thermal aspects during ion beam figuring for some sensible materials like BK7, but even for low expansion material like Zerodur. [less ▲]

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See detailIon Beam Induced Luminescence & Cultural Heritage
Calvo Del Castillo, Helena ULg

Scientific conference (2007, April)

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See detailIon Beam Induced Luminescence & Cultural Heritage
Calvo Del Castillo, Helena ULg

Scientific conference (2007, December)

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See detailIon beam induced luminescence of minerals
Calvo Del Castillo, Helena ULg; Ruvalcaba Sil, Jose Luis; Calderón, Tomás

Poster (2006)

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See detailIon channel degeneracy enables robust and tunable neuronal firing rates.
Drion, Guillaume ULg; O'Leary, Timothy; Marder, Eve

in Proceedings of the National Academy of Sciences of the United States of America (2015)

Firing rate is an important means of encoding information in the nervous system. To reliably encode a wide range of signals, neurons need to achieve a broad range of firing frequencies and to move ... [more ▼]

Firing rate is an important means of encoding information in the nervous system. To reliably encode a wide range of signals, neurons need to achieve a broad range of firing frequencies and to move smoothly between low and high firing rates. This can be achieved with specific ionic currents, such as A-type potassium currents, which can linearize the frequency-input current curve. By applying recently developed mathematical tools to a number of biophysical neuron models, we show how currents that are classically thought to permit low firing rates can paradoxically cause a jump to a high minimum firing rate when expressed at higher levels. Consequently, achieving and maintaining a low firing rate is surprisingly difficult and fragile in a biological context. This difficulty can be overcome via interactions between multiple currents, implying a need for ion channel degeneracy in the tuning of neuronal properties. [less ▲]

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See detailIon channel modulators: more diversity than previously thought
Dilly, Sébastien ULg; Lamy, Cédric; Marrion, Neil et al

in Chembiochem : A European Journal of Chemical Biology (2011), 12(12), 1808-1812

Ion channel function can be modified in various ways. For example, numerous studies have shown that currents through voltage-gated ion channels are affected by pore block or modification of voltage ... [more ▼]

Ion channel function can be modified in various ways. For example, numerous studies have shown that currents through voltage-gated ion channels are affected by pore block or modification of voltage-dependence of activation/inactivation. Recent experiments performed on various ion channels show that allosteric modulation is an important mechanism to affect channel function. For instance, in KCa2 (formerly SK) channels, the prototypic “blocker” apamin prevents conduction by an allosteric mechanism, while TRPV1 channels are prevented from closing by a tarantula toxin, DkTx, through an interaction with residues located away from the selectivity filter. The recent evidence therefore suggests that, in several ion channels, the region around the outer mouth of the pore is rich in binding sites which may be exploited therapeutically. These discoveries also suggest that the pharmacological vocabulary should be adapted to define these various actions. [less ▲]

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See detailIon Dissociation Kinetics in Mass Spectrometry
Leyh, Bernard ULg

in Reedijk, J. (Ed.) Reference Module in Chemistry, Molecular Sciences and Chemical Engineering (2013)

The variation of fragmentation rate constants as a function of the parent ion internal energy, or, alternatively, as a function of temperature, is crucial information to unravel the dissociation ... [more ▼]

The variation of fragmentation rate constants as a function of the parent ion internal energy, or, alternatively, as a function of temperature, is crucial information to unravel the dissociation mechanisms of molecular ions. This contribution provides the reader first with basic information on the statistical theories used to model unimolecular rate constants. Various experimental methods to measure such rate constants in the 102 to 1010 s^(-1) range are then discussed. Kinetic isotope effects are also briefly dealt with. How reaction mechanisms can be inferred from kinetic data is handled in an extensive section where selected examples from the recent literature are discussed. [less ▲]

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See detailIon homeostasis in the chloroplast
Hanikenne, Marc ULg; Bernal, Maria; Urzica, Eugen

in Wollman, Francis-Andre; Theg, Steve M. (Eds.) Plastid Biology (2014)

The chloroplast is an organelle of high demand for macro- and micro-nutrient ions, which are required for the maintenance of the photosynthetic process. To avoid deficiency while preventing excess ... [more ▼]

The chloroplast is an organelle of high demand for macro- and micro-nutrient ions, which are required for the maintenance of the photosynthetic process. To avoid deficiency while preventing excess, homeostasis mechanisms must be tightly regulated. Here, we describe the needs for nutrient ions in the chloroplast and briefly highlight their functions in the chloroplastidial metabolism. We further discuss the impact of nutrient deficiency on chloroplasts and the acclimation mechanisms that evolved to preserve the photosynthetic apparatus. We finally present what is known about import and export mechanisms for these ions. Whenever possible, a comparison between cyanobacteria, algae and plants is provided to add an evolutionary perspective to the description of ion homeostasis mechanisms in photosynthesis. [less ▲]

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See detailIon Mobility - Mass Spectrometry as a new approach for the screening of pesticide residues in food
Joly, Laure; Goscinny, Séverine ULg; Touilloux, Romain et al

Conference (2011, September)

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See detailIon Mobility Spectrometry Reveals Duplex DNA Dissociation Intermediates
Burmistrova, Anastasia; Gabelica, Valérie; Duwez, Anne-Sophie ULg et al

in Journal of the American Society for Mass Spectrometry (2013), 24

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See detailION MOBILITY – MASS SPECTROMETRY AS A NEW APPROACH FOR THE SCREENING OF PESTICIDE RESIDUES IN FOOD
Goscinny, Séverine ULg; Touilloux, Romain; Joly, Laure et al

in Organohalogen Compounds (2011)

Pesticide residue analysis requires methods that can determine hundreds of compounds at low levels in complex food matrices. This challenge has given rise to multi residue methods, the only efficient ... [more ▼]

Pesticide residue analysis requires methods that can determine hundreds of compounds at low levels in complex food matrices. This challenge has given rise to multi residue methods, the only efficient analytical approach. This type of analytical method entails a “generic” extraction followed by a soft or no purification step to avoid any analytes looses. With over a 1000 active compounds with different physical chemical properties, gas and liquid chromatography are used as complementary separative techniques. In the past decade, the determination has been performed on tandem mass analyzers, a powerful tool to overcome co-eluting compounds with excellent sensitivity. Nevertheless, these instruments can guarantee these results per acquisition cycles for more or less 150 compounds. This represents a serious limitation when the number of pesticides to be sought for monitoring and MRL enforcement is growing each year. As multiple injections from the same sample are not viable for laboratories, alternative options have to be explored. We propose the investigation of ion mobility (IM) coupled with mass spectrometry as a new approach for pesticide residue analysis in food. [less ▲]

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See detailIon mobility-mass spectrometry to perform structural classifications of disulfide-bridged-peptides
Massonnet, Philippe ULg; Upert, Gregory; Morsa, Denis ULg et al

Poster (2014, November)

Detailed reference viewed: 60 (26 ULg)