Grégory Boel
email: boel@ibpc.fr

Cédric Orelle
email: cedric.orelle@ibcp.fr

Jean-Michel Jault
email: jean-michel.jault@ibcp.fr

Elie Dassa
email: elie.dassa@pasteur.fr

ABC Systems: structural and functional variations on a common theme

ATP-binding cassette (ABC) systems constitute one of the largest superfamilies of proteins that catalyze an extremely wide variety of biological processes. They are involved not only in unidirectional transport through cellular or organelle membranes, but also in transcriptional regulation, mRNA translation, DNA repair and chromosome organization, and biogenesis of ironsulfur centers. These ATP-dependent nanomachines are present in all living organisms, Archaea, Bacteria and Eukaryotes, and they are also found in the genome of some large viruses [START_REF] Davidson | Structure, function, and evolution of bacterial ATP-binding cassette systems[END_REF].

All ABC systems share a conserved nucleotide-binding domain or protein (NBD) that binds and hydrolyzes ATP to energize them. Strikingly, genes encoding the NBDs are among the most highly conserved ones on Earth, together with rRNA and tRNA gene sequences [START_REF] Isenbarger | The most conserved genome segments for life detection on Earth and other planets[END_REF]. This NBD interacts with other components (proteins, protein domains or nucleic acids) to constitute the three main families of ABC systems: transporters, which are either importers or exporters, and systems involved in non-transport processes. In ABC transporters, the NBDs interact with transmembrane domains or proteins (TMD). Almost all importers are of prokaryotic origin. In general, they have a common architecture with TMD and NBD carried by two independent polypeptides and segregate into three types [START_REF] Rice | Diversity in ABC transporters: type I, II and III importers[END_REF]. Type I and type II importers have at least one additional extra-cytoplasmic (periplasmic or membrane-tethered) substrate-binding protein (SBP), which captures the substrate and delivers it to the TMDs. Type III importers, however, directly recruit their substrate through a dedicated membrane protein. Exporters are found in eukaryotes and prokaryotes, with their TMD and NBD mostly present on the same polypeptide chain. They have either the TMD or the NBD at the N-terminus of the protein, with configurations symbolized as (TMD-NBD) and (NBD-TMD), respectively. These transporters can form homo-or hetero-dimers. In eukaryotes, the four domains are often borne on the same polypeptide and in these cases they alternate with either a (TMD-NBD)2 or a (NBD-TMD)2 organization. ABC systems involved in cellular processes unrelated to transport are comprised of soluble NBD proteins that interact with other cytosolic protein complexes or nucleic acids to fulfill their functions [START_REF] Davidson | Structure, function, and evolution of bacterial ATP-binding cassette systems[END_REF]. We present in this special issue a series of papers focused on the characterization of selected representatives of the three ABC systems families.

In the opening article of this issue, I. Barry Holland draws a vivid historical sketch tracing the milestones leading to the present understanding of the evolution, structures and functions of these systems and critically analyzes the mechanistic models that were proposed through the years [START_REF] Holland | Rise and rise of the ABC transporter families[END_REF].

Type I importers contain at least five transmembrane segments in each TMD and function by an alternating access mechanism. The maltose-maltodextrin transport system is one of the most studied representatives of type I importers, whose structure and mechanism is the object of the review by Rebecca Mächtel and collaborators [START_REF] Mächtel | An integrated transport mechanism of the maltose ABC importer[END_REF].

Oligopeptide ABC importers are key players in providing bacteria with complex nitrogen and carbon sources, but not only. Specific systems in Gram-positive bacteria, which are involved in the uptake of signaling peptides are important in the regulation of sporulation, virulence and conjugation, as discussed by Leyla Slamti and Didier Lereclus [START_REF] Slamti | The oligopeptide ABC-importers are essential communication channels in Gram-positive bacteria[END_REF].

Type II importers, whose main representatives are Vitamin B12 and iron-siderophores transport systems, possess a single larger TMD that probably arose from an ancient TMD with six transmembrane segments by duplication. In this issue, structures of SBPs of Type II importers and the mechanism of transport are reviewed by Philippe Delepelaire [START_REF] Delepelaire | Bacterial ABC transporters of iron containing compounds[END_REF].

Type III importers, also known as Energy-Coupling Factor (ECF) systems, are involved in the transport of transition metals, vitamins and micronutrients. ECF systems comprise a membrane-bound substrate-binding protein (S component), unrelated in sequence and structure to SBPs, which forms a complex with two other subunits, the A (ATPase) and T (transmembrane) components. This assembly constitutes the whole type III importer, and is reviewed by Friedrich Finkenwirth and Thomas Eitinger [START_REF] Finkenwirth | ECF-type ABC transporters for uptake of vitamins and transition metal ions into prokaryotic cells[END_REF].

ABC exporters, as stated above, are generally composed of homo-or heterodimeric proteins displaying fused TMDs and NBDs. However, the inner membrane complex in a very few number of exporters displays the same architecture as importers, with subunits carried by individual polypeptides. This is the case for the LPT system, involved in the trafficking of LPS across the Gram-negative bacteria envelope. Recently, progresses were made in the understanding of the LPT system structure and mechanism, as described in the review of Paola Sperandeo and collaborators [START_REF] Sperandeo | The Lpt ABC transporter for lipopolysaccharide export to the cell surface[END_REF].

The Escherichia coli ftsE gene was found to be involved in cell division in 1968. Later, it was reported that FtsE is the ATPase that interacts with FtsX, its TMD counterpart, to form an ABC transporter. Recent genetic studies demonstrated that the FtsEX complex is located at cell division sites and is involved in cell division for a wide variety of bacteria. It is presently established that this atypical ABC transporter (probably of type VI) interacts with peptidoglycan hydrolases to control cell separation after septation and regulates the assembly and activation of the divisome, as discussed by Sebastien Pichoff and collaborators [START_REF] Pichoff | Roles of FtsEX in cell division[END_REF].

Canonical prokaryotic exporters, with a TMD-NBD organization (TMD at the N-terminus of the polypeptide) participate in the efflux of several molecules, including proteins, peptides, polysaccharides and drugs. They also participate in the flipping of lipids or lipid-linked macromolecules across the cytoplasmic membrane. Multidrug ABC exporters are clinically important because of the promiscuity of their expelled molecules and their up-regulation in response to certain stresses thereby contributing to the failure of chemotherapy and antibiotic treatments. The properties and the transport mechanism of such transporters are the subject of the review of Cédric Orelle and collaborators [START_REF] Orelle | Multidrug ABC transporters in bacteria[END_REF].

Energy coupling of transport is very predominantly dependent on ATP binding and hydrolysis in ABC systems. However, Hendrik van Veen and collaborators provide arguments in favor of an involvement of ion-gradients in some members of this family, as discussed in their review [START_REF] Van Veen | Energy coupling in ABC exporters[END_REF].

The emergence of multidrug resistant bacteria (MDR) and the decrease in the development of new antibiotics led to evaluation of the efficacy of new antibacterial agents.

Bacterial antimicrobial peptides (bacteriocins) might be promising tools to combat drug resistance. Bacteria use ABC systems to export bacteriocins into their environment, to outcompete other microorganisms living in the same ecological niche and also to develop immunity against the toxic peptides they produce. Konstantinos Beis and Sylvie Rebuffat present the mechanistic and structural aspects of these systems [START_REF] Beis | Multifaceted ABC transporters associated to microcin and bacteriocin export[END_REF].

In Gram-negative bacteria, the highly conserved CydDC export system, presented by Robert Poole and collaborators in this issue, translocates cysteine and glutathione across the cytoplasmic membrane into the periplasmic space, where the latter are needed for the redox cycle of enzymes involved in disulphide bond formation and isomerization [START_REF] Poole | The CydDC family of transporters[END_REF].

Pleiotropic Drug Resistance (PDR) multidrug ABC transporters are found in fungi and plants. They differ from other ABC exporters by an NBD-TMD organization. In pathogenic fungi, they are the major actors of multidrug resistance, and play a role in virulence. In their review, Alexis Moreno and coauthors discuss substrate polyspecificity of PDR systems and their NBD asymmetry in terms of ATP-binding sites [START_REF] Moreno | PDR-like ABC systems in pathogenic fungi[END_REF]. ABC systems involved in cellular processes unrelated to membrane transport comprise cytoplasmic ATPase whose function and mechanisms of action have long remained enigmatic until recently. The first example is the SUF system, distributed in prokaryotes and chloroplasts, which is involved in the assembly of Iron-Sulfur centers and their delivery to target proteins.

Recent advances were made in understanding the structure and the mechanism of action of the SUF machinery, as reviewed by Pierre Simon Garcia and collaborators [START_REF] Garcia | The SUF system: an ABC ATPase-dependent protein complex with a role in Fe-S cluster biogenesis[END_REF].

The ABC-F proteins, widely distributed among living organisms, modulate mRNA translation by interaction with the ribosomal E-site. A prokaryotic subgroup named ARE-ABC-F is implicated in resistance to many classes of antibiotics. Farés Ousalem and co-authors discuss the structure and mechanism of ABC-F systems [START_REF] Ousalem | ABC-F proteins in mRNA translation and antibiotic resistance[END_REF].

The universality and importance of ABC systems among living organisms were recognized about 35 years ago [START_REF] Higgins | A family of closely related ATP-binding subunits from prokaryotic and eucaryotic cells[END_REF], although their conservation within bacteria was reported earlier [START_REF] Gilson | Extensive homology between membrane-associated components of histidine and maltose transport systems of Salmonella typhimurium and Escherichia coli[END_REF].

Many research teams worldwide participated in the acquisition of the present body of knowledge, most notably during the past ten years, with the elucidation of dozens of structures of ABC complexes. Looking beyond the present status, based mainly on static snapshots of various conformational states of different ABC systems, novel discoveries will reveal the dynamics and kinetics of conformational changes occurring during their catalytic cycles by using methods such as single molecule Förster resonance energy transfer (sm-FRET) as stated by several contributors of this special issue [START_REF] Holland | Rise and rise of the ABC transporter families[END_REF][START_REF] Mächtel | An integrated transport mechanism of the maltose ABC importer[END_REF][START_REF] Beis | Multifaceted ABC transporters associated to microcin and bacteriocin export[END_REF].

Acknowledgements

We wish to thank all the contributors of this special issue, and Géraldine Legras for her help and expert advice during the editorial process.


Karima Sini

Damien Bourgeois

Madjid Idouhar

Madjid IDOUHAR b Michaël Carboni
email: michael.carboni@cea.fr

Daniel Meyer

Karima Sini Ab

Metal-organic framework sorbents for the removal of perfluorinated compounds in an aqueous environment

Keywords: Perfluorinated Pollutants, Hydrophobic interaction, Waste water treatment, Metal-Organic Framework, Porous materials

Introduction

Fluorosurfactants are com osed o ver strong F ond (116 kcal.mol -1 ) and lead to very low surface tension in aqueous solutions. [START_REF] Richardson | Water Analysis: Emerging Contaminants and Current Issues[END_REF] Owing to these properties and despite their high costs, fluorocarbons have been used during several decades in many applications, eg cooling agents, fire-fighting foams or in the photolithographic industry. [START_REF] Mcculloch | Fluorocarbons in the global environment: a review of the important interactions with atmospheric chemistry and physics[END_REF] Perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) (denoted as PFOX along the manuscript) are very stable and considered as almost nonbiodegradable, generating a large pollution in natural environment. Several studies have reported that PFOX are widely present in surface water, in ground, marine or drinking water at mg.L -1 to low g.L -1 levels. [START_REF] Rumsby | Perfluorooctane sulphonate and perfluorooctanoic acid in drinking and environmental waters[END_REF] They have received great attention because of their bioaccumulation, and potential health concerns due to their toxicity and carcinogenicity have been largely discussed in the literature. [START_REF] Viberg | Perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA)[END_REF] Recently, PFOS has been added to the list of Persistent Organic Pollutants (POPs) under the Stockholm Convention, [START_REF] Mclachlan | Can the Stockholm convention address the spectrum of chemicals currently under regulatory scrutiny? Advocating a more prominent role for modeling in POP screening assessment[END_REF] and the European Food Safety Authority (EFSA) has established a tolerable daily intake (TDI) for both PFOS and PFOA present in food. [START_REF] Noorlander | Levels of Perfluorinated Compounds in Food and Dietary Intake of PFOS and PFOA in The Netherlands[END_REF] Numerous methods have been developed for the degradation of PFOX in aqueous environments, such as sonochemical, [START_REF] Moriwaki | Sonochemical Decomposition of Perfluorooctane Sulfonate and Perfluorooctanoic Acid[END_REF] irradiation [START_REF] Yamamoto | Photodegradation of Perfluorooctane Sulfonate by UV Irradiation in Water and Alkaline 2-Propanol[END_REF] or oxidation methods. [START_REF] Zhuo | Efficient Electrochemical Oxidation of Perfluorooctanoate Using a Ti/SnO 2 -Sb-Bi Anode[END_REF] However, these techniques have high operating costs, and extraction has also been evaluated with adsorbents such as granular activated carbon (GAC) or resins. But their adsorption capacities remain rather low (112 -160 and 46 -41 mg of PFOA and PFOS respectively per gram of GAC and resin). [START_REF] Yu | Sorption of perfluorooctane sulfonate and perfluorooctanoate on activated carbons and resin: Kinetic and isotherm study[END_REF] Hybrid organic-inorganic materials, metal-organic frameworks (MOFs), have attracted considerable interest because of their large specific surface areas and pore volumes. [START_REF] Zhou | Metal-Organic Frameworks (MOFs)[END_REF] Zirconium-MOFs, UiO-66 and 67 built with bdc (benzene-dicarboxylic acid) and bpdc (biphenyl-dicarboxylic acid) ligands respectively, have shown to possess very high thermal, chemical and water stability, [START_REF] Katz | A facile synthesis of UiO-66, UiO-67 and their derivatives[END_REF] making them suitable as sorbents for environmental purposes. [START_REF] Amador | BTEX removal from aqueous solution with hydrophobic Zr metal organic frameworks[END_REF][START_REF] Amador | Sorption and photodegradation under visible light irradiation of an organic pollutant by a heterogeneous UiO-67-Ru-Ti MOF obtained by postsynthetic exchange[END_REF] Recently, we have shown that Zirconium-MOF UiO-66, with small cavity, can efficiently adsorb PFOX. [START_REF] Sini | Metal-organic framework sorbents for the removal of perfluorinated compounds in an aqueous environment[END_REF] In this study, we evaluated the efficiency of UiO-67, with larger cavity, for the removal of PFOX in aqueous solution. Comparison with UiO-66 revealed that the size of the cavity is essential to efficient sorption of pollutants inside the material. Results show that the sorption mechanism is based on a physical process, with very rapid sorption of pollutants in aqueous solution (around 1 hour), but different mechanism according to the cavity size.

Experimental

Synthesis and characterizations

All reagents were purchased from Aldrich and were used without further purification. UiO-66 and UiO-67 were synthesized as reported in the literature [START_REF] Katz | A facile synthesis of UiO-66, UiO-67 and their derivatives[END_REF] and characterized by PXRD and SEM (Supplementary information).

Sorption experiments

Sorption experiments were performed at 298 K in an aqueous solution at pH 4 with a 1 mg/mL MOF concentration. After centrifugation, the solution was analyzed with 19 F NMR (Brucker) with the use of an internal standard (trifluoroethanol), and the concentration of PFOX determined after integration of characteristic peaks as previously reported. [START_REF] Sini | Metal-organic framework sorbents for the removal of perfluorinated compounds in an aqueous environment[END_REF] All experiments were at least duplicated. Calibration curves were performed for [PFOX] range of 100 to 1000 mg.L -1 (Figure S1).

Results and discussion

Both materials have been obtained after solvothermal syntheses with the use of HCl as modulator in order to increase the crystallinity of the materials. [START_REF] Katz | A facile synthesis of UiO-66, UiO-67 and their derivatives[END_REF] The UiO phase was confirmed for both materials by SEM and optical microscopy through the formation of discrete octahedral crystals (Figure S2), and by diffractograms recorded at high angle peaks ( e ond 2θ o 30º) in agreement with the theoretical pattern (Figure S3). Sorption kinetics of fluorinated pollutants with both MOFs was first studied (Figure 1, top-left). A large amount of pollutant is adsorbed in less than 20 minutes and equilibrium is reached within 60 minutes. Pseudo-first order (1) and pseudo-second order (2) equations were used to model the experimental data (q e and q t are the sorption capacities at equilibrium and any time t, respectively, and k 1 and k 2 are the pseudo-first-and pseudo-second-order rate constants, respectively). The pseudosecond order model (Figure 1, top-right) leads to much better fits in comparison with the pseudo-first order (Table S1) with correlation coefficients of 0.999 to 0.996.

(

) 1
(2)

Temperature effect on sorption capacities of PFOA and PFOS was studied over a range of 298 K to 318 K. A sorption increase with an increase of the temperature was observed, and is attributed to a higher diffusion of PFOX molecules into the MOFs cavities. The thermodynamic parameters of the sorption including were calculated from the Van't Ho equation ( 3) and are summarized in Table S2.

Ln Kd = ΔS°/ R -ΔH°/ RT (3)
In all cases, ΔG and ΔH values indicate respectively that the sorption process is spontaneous and endothermic, whereas ΔS values suggest that the randomness at the solid-liquid is largely compensated by the release of the freedom in the water phase. UiO-66 best fit with Langmuir model:

UiO-67 best fit with Freundlich model:

( Fits are performed using the Langmuir model for UiO-66 and the Freundlich model for UiO-67.

m ax m ax 1 1 q K q C q C L e e e   
Sorption isotherms of both PFOX by both MOFs show an increase with the PFOX concentration until saturation (Figure 2). Experimental data were then fitted using the linear form of the Langmuir model (Equation 4, Figure S4) and the Freundlich model (Equation 5, Figure S4). Fitting results are summarized in Table 1, where q e is the sorption capacity at equilibrium, q m is the saturation sorption capacity, C e is the PFOX concentration in solution at equilibrium, K L is the Langmuir constant related to binding site affinity, K f is the Freundlich constant and n (dimensionless; 0 < n < 10) is a Freundlich intensity parameter. Complete saturation was observed only for UiO-66. In this case, the Langmuir model seems adequate and supposes that sorption occurs on a homogeneous surface by a monolayer deposition. In the case of UiO-67, the increase of cavity size leads to a change in sorption mechanism, possibly related to a multi-layer process, partially limited by diffusion inside the cavity. Also, higher sorption (up to 743 mg.g -1 in the case of PFOA) is observed.

Figure 1 :

 1 Figure 1: Top: (left) Sorption kinetics of PFOX with UiO-66 and UiO-67; (right) Application of the pseudo-second-order kinetic model. Bottom: (left) Evolution of sorption according to temperature; (right) Van't Ho lot (pH = 4, [PFOX] = 500 mg.L -1 , [MOF] = 1 mg/mL, 60 min).

Figure 2 :

 2 Figure 2 : Sorption isotherms of PFOA and PFOS by UiO-66 and UiO-67 in water (pH 4) at 298 K.

ConclusionA

  Zirconium-MOF based on bpdc (biphenyl-dicarboxylic acid) ligand, UiO-67, has been used for the extraction of fluorinated pollutants from aqueous solutions. It has shown higher capacities than the equivalent MOF based on bdc (benzene-dicarboxylic acid) ligand, UiO-66, which possesses smaller cavities. These results are in full agreement with a sorption mechanism based on hydrophobic interactions between the pollutant and the MOF cavity, instead of coordination of the pollutant on the metal node. The increase of the cavity size also leads to a change in sorption mechanism: this highlights the importance of detailed studies on such materials. MOFs are indeed simple and scalable materials, and this works demonstrates their potential use for the decontamination of organic pollutants from aqueous solutions.

Table 1 :

 1 Calculated parameters for sorption of PFOA and PFOS by UiO-66 and UiO-67, using Langmuir and Freundlich models.

	Adsorbent		Langmuir			Freundlich
			q m	K L	R 2	Kf	n	R 2
			(mg.g -1 )	(L.mg -1 )		(mg/g)(
						L/mg) 1/n
	UiO-66	PFOA	388	0.0182	0.9718	1.833	2.150	0.858
		PFOS	160	0.0466	0.9803	1.834	2.597	0.940
	UiO-67	PFOA	700	0.1143	0.9740	2.239	5.650	0.912
		PFOS	580	0.0884	0.9805	2.200	5.235	0.883


Aurélien Favre
email: favrea@coria.fr

Milan Dimitrijevic

Vincent Morel

Stevica Djurovic

Zoran Mijatovic

Gilles Godard

Arnaud Bultel

𝐧 𝐞

𝑻 𝒆 Evolutions

Study of the 777 nm Lines Profile of Atomic Oxygen Using Laser-Induced Plasmas

come

EXPERIMENTAL SETUP

The laser pulse (1064 nm, 30 ps, 14 mJ) is focused to produce a plasma in an Aceton-saturated Argon (80 % -20 % vol.) atmosphere (black chamber) at atmospheric pressure. The is formed (lifetime of the order of 10 𝜇𝑠). Its radiation is collected along a and analyzed using an Isoplane SCT-320 spectrometer over the 200, 850 𝑛𝑚 spectral range.

Electron temperature 𝑇 𝑒 is of the order of 15000 to 20000 𝐾.

Electron density

The determination of 𝑛 𝑒 is based on • The FWHM of the 𝐻 𝛼 line,

• The FWHM of the 𝐻 𝛽 line,

• The shift of the 𝐻 𝛼 line.

The uncertainty on 𝑛 𝑒 from the 𝐻 𝛼 FWHM is taken as twice the one from the 𝐻 𝛽 FWHM. The final 𝑛 𝑒 values are plotted in green.

WIDTH OF THE O I 777 NM TRIPLET

Redshift observed

Classical behavior.

Shift considered

From the FWHM of the triplet since the lines overlap for high values of the electron density.

Shift dynamics

Non linear shift towards 𝑛 𝑒 .

𝑯 𝟐 emission

𝑯 𝟐 emission

𝐹𝑊𝐻𝑀 𝑎𝑝𝑝. = 0.025 𝑛𝑚 For 𝒏 𝒆 < 𝟏𝟎 𝟐𝟒 𝒎 -𝟑 Satisfactory agreement with Griem's results.

For 𝒏 𝒆 > 𝟏𝟎 𝟐𝟒 𝒎 -𝟑 No experimental result available here. But Griem's shift increases rapidly. Griem's dynamics would lead to too strong values of the shift?

  𝒕 = 𝟏𝟒𝟓 𝒏𝒔 𝒕 = 𝟐𝟗𝟓 𝒏𝒔 𝒕 = 𝟕𝟗𝟓 𝒏𝒔 𝒕 = 𝟒𝟗𝟓 𝒏𝒔 SHIFT OF THE O I 777 NM TRIPLET CONCLUSION & PERSPECTIVES Here 𝝎 𝒔 = 𝟒. 𝟏𝟎 × 𝟏𝟎 -𝟑 𝒏𝒎 instead of 𝟐. 𝟐𝟖 × 𝟏𝟎 -𝟑 𝒏𝒎 (Griem) 𝒏 𝒆 𝒎 -𝟑 = 𝟏. 𝟎𝟕𝟏𝟒 × 𝟏𝟎 𝟐𝟑 𝒆 ∆𝝀 𝑺 𝒏𝒎 𝟎.𝟎𝟒𝟗𝟒 for 𝒏 𝒆 < 𝟏𝟎 𝟐𝟒 𝒎 -𝟑 Shift precision ∆𝜆 = 0.006 𝑛𝑚 Conclusion • Laser-induced plasmas produced with spectra involving the emission of the O I triplet at 777.4 𝑛𝑚 • Stark broadening parameter obtained for 𝑛 𝑒 < 10 24 𝑚 -3 almost twice of the value of Griem • Stark shift parameter obtained for 𝑛 𝑒 < 10 24 𝑚 -3 in good agreement with the value of Griem Perspectives • Assessment of the departure from equilibrium using Ar lines • Validation of the 𝑛 𝑒 values by comparison with equilibrium calculations 𝒏 𝒆 = 𝟕 × 𝟏𝟎 𝟐𝟑 𝒎 -𝟑 𝒏 𝒆 = 𝟐. 𝟔 × 𝟏𝟎 𝟐𝟑 𝒎 -𝟑 𝒏 𝒆 = 𝟏. 𝟒 × 𝟏𝟎 𝟐𝟑 𝒎 -𝟑 𝒏 𝒆 = 𝟖. 𝟐 × 𝟏𝟎 𝟐𝟑 𝒎 -𝟑


Floriane Socchi

Michele Bigorre

Marion Normandin

Guillaume Captier

Didier Bessis

Michel Mondain

Catherine Blanchet

Mohamed Akkari

Pascal Amedro

Arthur Gavotto

Hemangiol® in infantile haemangioma: A paediatric post-marketing surveillance drug study


CONTEXT & OBJECTIVES

Diagnostic technique LIBS (Laser-Induced Breakdown Spectroscopy) For a target composed of elements in very low concentration or whose upper levels of common transitions are high (10 eV or more) the maximization of the output signal is mandatory. One efficient technique is to heat up the plasma with a second pulse shifted in time. This experimental process is called double pulse (DP).

Experimental characterization of double pulse laser-induced plasmas

CONCLUSIONS & PERSPECTIVES

The (1064 nm, 30 ps, 14 mJ) is focused to produce a plasma. The (512 nm, 6 ns, mJ) is focused in this plasma with a temporal shift of ∆𝐭.

radiation is collected on a to be analysed by our SCT-320 spectrometer.

LASERS:

- The experimental setup used for LIAS is rigorously the same as described above except that the second pulse is spatially translated.

We obtain two plasmas temporally shifted by a delay: and

• Effective temporally and spatially controlled double pulse setup.

• Detection limits are sorely enhanced, output signal is at least 5x multiplied.

• Possible determination of electron density and electron temperature.

• Possible characterization of lower states by absorption spectra.

• Accuracy can be strongly improved by working with a higher spectral resolution and signals with accumulations.

• Detection of light elements such as H isotopes in heavy matrices like W remains our long-term objective. )

1

  CORIA, UMR CNRS 6614, Normandie Université, 76801 Saint-Étienne du Rouvray, FRANCE ‡ arnaud.bultel@coria.fr AURÉLIEN FAVRE 1 , ARNAUD BULTEL 1 ‡ , VINCENT MOREL 1 , GILLES GODARD 1 Objectives • Obtaining an experimental setup accurately controlled in time and space. • Quantifying the improvements in terms of output spectral radiance. • Observing absorption lines by LIAS. • Quantifying roughly electron and low level number densities.

  EKSPLA PL-2251: ps -QUANTEL U100: ns ns ON ns OFF Comments • Double pulse setup effective. • Optimal time shifting to improve the output signal: ∆𝐭 = 150 ns • First determination of electron density: 𝟏𝟎 𝟐𝟒 𝐦 )𝟑 < 𝐧 𝐞 < 𝟏𝟎 𝟐𝟓 𝐦 )𝟑 Comments • Al II lines only observed in double pulse. ns OFF] configuration, we observe emission spectra. As Al I 394.40 nm and Al I 396.15 nm are the resonance doublet, auto-absorption is noticed. • In [ns ON] configuration, we can observe absorption spectra. Absorption is only significant for delay ≥ 1.2 𝛍𝐬.