Y Bouhoute

D Grekov

N Merle

K Szeto

C Larabi

I Del Rosal

L Maron

L Delevoye

R M Gauvin

M Taoufik

I Del Rosal

On the

  L'archive ouverte pluridisciplinaire

Introduction

Tungsten oxide dispersed on silica, also known as the Phillips catalyst (not to be confused with the Cr/SiO 2 olefin polymerization Phillips catalyst), is used in several major industrial processes, due to its efficiency in olefin metathesis. 1,2,3 Beyond trial and error approach for its improvement, there is a major interest in investigating the nature of the active sites within this system, especially down to a molecular level. In particular, bis-siloxide oxo carbenic species [(SiO) 2 WO(CHR)] have been proposed as catalytically active sites. 4 Since our early works about 10 years ago on well-defined silicagrafted [WOR 3 (OSi)] species (R= CH 2 C(CH 3 ) 3 ), 5 the quest for models and alternatives to this illdefined catalyst has motivated several studies, where variation of the ligands present in the coordination sphere of the metal was performed. Examples of metathesis active silica-supported oxo carbenic species have been reported. 6 In addition, thanks to proper design of the organometallic precursor, we have developed bisgrafted species [(SiO) 2 WO(CH 2 SiMe 3 ) 2 ] from grafting of [WO(CH 2 SiMe 3 ) 3 Cl] onto silica dehydroxylated at 200 °C. 7 This ²species displayed very interesting catalytic properties, which motivated further investigation on related siloxide species. Indeed, in order to retain a similar tungsten coordination sphere, we chose in the present study to perform the grafting of the oxo bisalkyl bisiloxide complexes described by Wolczanscki for oxo atom transfer reaction, namely of the type [WOR 2 (OSitBu 3 ) 2 ]. 8 They feature a coordination sphere close to that postulated for the active centers in WO 3 /SiO 2 , and closely related to that of [(SiO) 2 WO(CH 2 SiMe 3 ) 2 ]. More precisely, we considered using the silox 9 derivative [WOMe 2 (OSitBu 3 ) 2 ] (1-Me) as a precursor for the design of silica-supported precatalysts for olefin metathesis. We therefore proceeded to study the reactivity of 1-Me towards partially dehydroxylated silica. Furthermore, bearing in mind the high potential of solid state NMR to investigate the molecular structure of (supported) organometallic species, 10 we also resorted to 17 O MAS NMR as a tool for the structural understanding of the molecular complexes and of the corresponding silica grafted derivatives. 11 17 O MAS NMR is a very informative approach to the characterization of materials and molecules, though with some hurdles and challenges. 12 As this nucleus features a rather low gyromagnetic ratio (-3.628 10 7 rad.s -1 .T -1 ), use of high magnetic field is of importance. Furthermore, due to the low natural abundance (0.037 %) of this quadrupolar nucleus, S=5/2, isotopic enrichment is most often a prerequisite. 13,14,15 As described by Wolczanski, 1-Me can be prepared by alkylation of 1-Cl, which itself derives from WOCl 4 (Scheme 1). 8 This synthetic scheme is well-suited for the oxo moiety labeling, as we have previously reported the efficient 17 O-labelling of WOCl 4 using WCl 6 and isotopically-labelled O(SiMe 3 ) 2 , itself prepared from 90%- 17 O enriched H 2 O and SiMe 3 Cl (Scheme 1a). 16,17 This offers an efficient entry into the synthesis of 17 O-enriched oxo siloxide alkyl complexes. To ease the assessment of the NMR parameters, we recorded the 17 O NMR spectra of the enriched compounds at two different magnetic fields, namely 9.4 and 18.8 T. The 17 O MAS NMR spectra of 17 O-labelled 1-Cl and 1-Me are displayed in Figures 1 and2, respectively. Also featured on the figures are the corresponding best-fit simulations. The same set of parameters was used for the simulation of a given material at the two different magnetic fields. Isotropic and anisotropic parameters were deduced from best-fit simulations for both 1-Cl and 1-Me, (Table 1). Regarding the isotropic chemical shift (CS), both values are in line with those previously obtained for similar high-valent tungsten species bearing terminal oxo moieties. 7,1618 The line shapes are characteristic of 17 O sites featuring low quadrupolar coupling constants and moderate chemical shift anisotropies. The chloride derivative features a higher CS value than its alkyl counterpart, in line with the electron-withdrawing effect from the halide ligands, compared to the σ-donating alkyl substituents. Regarding the anisotropic parameters, such as the quadrupolar coupling constant, a higher value was determined for 1-Cl compared to that of 1-Me (2.7 and 0.15 MHz, respectively).

Results and discussion

Comparison with DFT calculated values showed that chemical shift and quadrupolar coupling constant are well in line with experimental data (Table 1). This is not so much the case for the chemical shift anisotropy, or for the asymmetry parameters, which may differ significantly. These sets of 17 O NMR parameters for the terminal oxo species can be compared to that of the WOR 3 X derivative. Whereas compounds 1-Cl and 1-Me adopt a trigonal bipyramidal configuration with the oxo in the trigonal plane, the trisalkyl species feature a square pyramidal configuration with an apical position for the oxo functionality. We can then propose a classification for terminal oxo species, depending on the geometry. ] has a CS value in the lower range, care should be taken as in the solid-state structure this compound consists of chains of tungsten species interacting via coordination of the oxo moiety. 16 The oxo function is therefore not to be considered as purely terminal in this compound. When comparing structurally related species, for instance and [WOCl(CH 2 CMe 3 ) 3 ] and [WO{OSi(OtBu) 3 }(CH 2 CMe 3 ) 3 ], the substitution of a chloride by a siloxide has only a minor influence on the CS value (735 and 731 ppm, respectively).

In order to shed light on the significant difference in the chemical shift values of 1-Cl and 1-Me, a natural chemical shielding (NCS) analysis 20 has been performed on the corresponding DFT models (Figure 3). When considering the quadrupolar coupling constant for complexes featuring an oxo moiety in apical poisition, the geometry of the considered species has a major, clear-cut impact: square pyramidal configuration gives rise to values significantly lower than those of trigonal bipyramidal ones (respectively [1.0 -< 2] MHz and [4.6 -5.5] MHz range). This tendency is also observed for the chemical shift anisotropy, which is most particularly high in the case of the trigonal bipyramidal species (-1062 --1136 ppm), resulting in the very characteristic signal manifold for such species. 18,19 In the case of 1-Cl and 1-Me, in the absence of single crystal X-ray diffraction study, one may rely on DFT-optimized structure for geometry assessment (Figure 3). Both compounds feature a configuration analogous to that of the bis n-butyl derivative [WO(n-Bu) 2 (OSitBu 3 ) 2 ], namely of distorted trigonal bipyramidal type, with the oxo and alkyl groups in the meridional positions. Significant differences between the two computed structures are observed, most particularly regarding the SiO-W-OSi and X-W-X angles (X= Cl, CH 3 , Figure 3). These values can be used to calculate the τ parameter, which is a descriptor for assessment of pentacoordinated complex geometry distinguishing between square pyramidal (τ = 0) and trigonal bipyramidal geometry (τ = 1). 22 17 O chemical shift tendency falls short of providing structural information. 23 As discussed above, the grafting of such species is interesting when aiming at preparing high-valent oxo tungsten (pre-)catalysts for olefin metathesis, that can be probed as models for the industrial Phillips catalyst's active sites. ). This material features a specific area of 190 m 2 .g -1 , and a SiOH surface density of 0.7 OH.nm -2 . The residual silanol groups are noninteracting, as evidenced by the characteristic sharp signal at 3747 cm -1 on the infrared spectrum (Figure 5a). 5b). The non-interacting silanol signal at 3747 cm -1 is mostly absent from the IR spectrum of 2, and weak, broad bands resulting from interacting silanols are observed at 3692 and 3490 cm -1 (the latter being very broad). It results most probably from SiO-H perturbed by grafted organometallic centers. Accordingly, (C-H) bands are also observed in the 2990-2880 cm -1 range. In order to gain a better understanding on the grafting reaction of 1-Me onto SiO 2-700 , the enthalpy profile for this reaction was computed at the DFT level (B3PW91). The isolated silanols groups onto the SiO 2-700 surface were modeled using a molecular polyoligosilsesquioxane complex, as successfully used in previous studies. 7,18,24 Two different reaction pathways have been computed (Figure 8): either (i) the W-CH 3 silanolysis with the concomitant methane release or (ii) the W-OSitBu 3 silanolysis leading to the release of HOSitBu 3 . The W-CH 3 silanolysis, as can be seen in the blue and green profiles are kinetically accessible (21.4 and 18.3 kcal mol -1 ) and thermodynamically very favorable (-36.5 and -37.7 kcal mol -1 ). This barrier is lower (by 7 kcal mol -1 ) for the W-OSitBu 3 silanolysis, as can be seen in the black and red profiles, due to a better charge distribution at the transition state.

However, It is also noteworthy that, from a thermodynamic point of view, the formation of [(SiO)WOMe(OSitBu 3 ) 2 ] is more favorable than that of [(SiO)WOMe 2 (OSitBu 3 )] (~37 vs ~9.5

kcal.mol -1 ). Thus, calculations suggest that [(SiO)WOMe 2 (OSitBu 3 )] is the kinetic product of the grafting reaction, while [(SiO)WOMe(OSitBu 3 ) 2 ] is the thermodynamic one. S1). Simulated 17 O MAS NMR spectra of the two DFT models are displayed on Figure 7 (c for 2A and d for 2B). Thus, if interconversion occurs rapidly under the measurement conditions, it is expected that the 17 O NMR signal manifold will be significantly affected. It has been reported by Schurko et al. that if an exchange occurs between two states of non-equal ground state energies, the resulting NMR lineshape will most likely be heavily weighted to the lowest energy conformer and would be minimally affected by motions. 25 In the present case, based on the isotropic chemical shift of the WO moiety in 2 estimated at about 730 ppm, it is more likely that the major configuration of the surface species is that of DFT model 2A, namely with the oxo function in trans position to the surface siloxide.

Bis-alkyl complex 1-Me is thermally stable, that is, despite the cis arrangement of the two alkyl groups, they do not undergo α-H elimination to generate a alkylidene function. 8 This is most probably due to the insufficient steric pressure within the dimethyl species, hindering the process. 26 However, we also observed previously that [(SiO)WO(CH 2 ECH 3 ) 3 ] (E= C, Si) do not afford alkylidene complexes upon heating, but generate carbene species in the presence of the olefinic substrate, as metathesis is initiated under such conditions. Thus, it seemed relevant to probe the reactivity of 2 toward olefins. We first attempted to perform propene metathesis in batch reactor, based on our previous results with group 6 oxo pre-catalysts. However, no conversion of propene was observed even upon heating at 80°C for 10 hours. We thus probed the reactivity of 2 towards a less demanding substrate such as norbornene. Indeed, oxo alkyl species were previously shown to be able to initiate the ring opening metathesis polymerization of this monomer. 27 There again, no activity was detected, both for the molecular 1-Me and the supported 2. Nevertheless, this lack of activity in metathesis nicely illustrates the importance of the coordination sphere geometry: Indeed, species featuring a oxobisalkyl-bissiloxide set of ligands but with a different geometry (square pyramidal) than that of 2 (presumably trigonal bipyramidal from DFT calculations) display high activity in propene metathesis, due to a more efficient initiation into catalytically-active carbene species.

Conclusion

Tungsten oxo siloxide species were probed as precatalysts for olefin metathesis, in the view of mimicking postulated active sites in industrial catalysts. Use of 17 O solid state NMR helped in linking spectroscopic and structural features for coordination and organometallic WO derivatives, with the support of theoretical calculations. Grafting of such a derivative was studied via a joint experimental and spectroscopic study. We demonstrated that selective grafting occurs by siloxide ligand protonolysis, affording a bisalkyl species. While the supported material proved inactive towards linear and cyclic olefinic substrates, this contribution illustrates how the design of catalysts is of prime importance in the development of efficient catalytic systems, as can be mediated via ligand sphere modifications. 28

Experimental section

All experiments were carried out by using standard Schlenk and glovebox techniques. Solvents were purified and dried according to standard procedures. C 6 D 6 (SDS) was distilled from NaK and stored in glovebox. 1-Cl and 1-Me were synthesized following the literature procedure. 8 17 O-enriched WOCl 4 was prepared using the reported method using 90 % 17 O-labelled water from Cortecnet. 16 SiO 2-700 was prepared from Aerosil silica (Degussa, specific area of 200 m 2 g -1 ), which was dehydroxylated at 700 °C under high vacuum (10 -5 Torr) for 15 h to give a white solid having a specific surface area of 190 m 2 g -1 and containing 0.7 OH nm -2 . Elemental analyses were performed at the Pascher Mikroanalytisches Labor at Remagen-Bandorf (Germany). IR spectra were recorded on a Nicolet 6700 FT-IR spectrometer by using a DRIFT cell equipped with CaF 2 windows. The samples were prepared under argon within a glovebox. Typically, 64 scans were accumulated for each spectrum (resolution 4 cm -1 ).

NMR Characterization. Solution NMR spectra were recorded on an Avance-300 Bruker spectrometer. All chemical shifts were measured relative to residual 1 H or 13 C resonances in the deuterated solvent: C 6 D 6 ,  7.15 ppm for 1 H, 128 ppm for 13 C. 1 H and 13 C solid-state MAS NMR spectra were recorded on Bruker Avance-500 and Bruker Avance-300 spectrometers with a conventional double-resonance 4 mm CP MAS probe at the Laboratoire de Chimie Organométallique de Surface. The samples were introduced under argon in a zirconia rotor (4 mm), which was then tightly closed. In all experiments, the rotation frequency was set to 10 kHz unless otherwise specified.

Chemical shifts were given with respect to TMS as external reference for 1 H, 13 C and 29 Si NMR. The DFT Methodological Details. All DFT calculations were carried out with the Gaussian 09 suite of programs. 29 Geometries were fully optimized in gas phase without symmetry constraints, employing the B3PW91 functional. 30,31 The nature of the extrema was verified by analytical frequency calculations. The calculation of electronic energies and enthalpies of the extrema of the potential energy surface (minima and transition states) were performed at the same level of theory as the geometry optimizations. IRC calculations were performed to confirm the connections of the optimized transition states. Stuttgart effective core potentials and their associated basis set were used for silicon and tungsten. 32 The basis sets were augmented by a set of polarization functions (ζd = 0.284 for Si and ζf = 0.823 for W). 33 For the other elements (H, C, Cl and O), Pople's double-ζ basis set 6-31G(d,p) was used. 34 The optimized structures were used for 17 O NMR calculations. These calculations were also performed using a higher Dunning's correlation consistent basis set cc-PVTZ for the oxygen atoms. 35 In all cases, among the various theories available to compute shielding tensors, the Gauge Including Atomic Orbital (GIAO) method has been adopted for the numerous advantages it presents. 36 Typically, in order to compare our calculations with experimental values, 17 O shielding has been converted to chemical shift using the usual equation: δ iso = σ iso ref -σ iso sample , where σ iso ref is the isotropic 17 O shielding of the liquid water. In the continuation of our previous studies, 7,18 an internal reference is

Scheme 1 .

 1 Scheme 1. Synthesis of a) 17 O-labelled WOCl 4 and b) 1-Me and 2

Figure 1 .

 1 Figure 1. 17 O MAS NMR spectra of 1-Cl at a) 9.4 and c) 18.8 T, along with the corresponding best-fit

Figure 2 .

 2 Figure 2. 17 O MAS NMR spectra of 1-Me at a) 9.4 and c) 18.8 T, along with the corresponding best-

Figure 3 .

 3 Figure 3. DFT Optimized structures of 1-Cl and 1-Me and selected angles.

Figure 4 .

 4 Figure 4. a) Orientation of the chemical shielding tensor in 1-Cl and 1-Me and b) results of the NCS

Figure 5 . 2 The 1 H 1 ppm in 1 -

 52111 Figure 5. DRIFTS spectra of a) SiO 2-700 and b) 2

Figure 6 . 1 H

 61 Figure 6. 1 H (left) and 13 C CP (right) MAS NMR spectra of 2 (11.75 T, spinning speed 10 kHz)

Figure 7 .

 7 Figure 7. a) 17 O MAS NMR spectrum of 2 at 18.8 T, with arrow designating the isotropic chemical

Figure 8 .

 8 Figure 8. Calculated enthalpy profiles of the different pathways of the grafting of 1-Me onto SiO 2-700

  used for the calibration of the σ iso ref value: σ iso ref = 292.2 ppm. The17 O quadrupolar coupling constant C Q and the asymmetry parameter η Q , which describes the interaction between nuclear quadrupole moment of the oxygen nuclei with the electric field gradient (EFG) arisen at these sites, are calculated from the EFG tensor eigenvalues V 11 , V 22 , and V 33 . The NCS-NBO analysis 37 allows a quantitative partitioning of the isotropic shielding constants of each nucleus for which GIAO calculations were performed, showing the Lewis "L" and non-Lewis "NL" contributions arising from each occupied NBO as well as the analysis of the shielding tensor in terms of canonical MOs, following Ditchfield's original treatment.Authorscontribution Y. B.: investigation; D. G.: investigation, writing, N. M.: investigation, K. S.: investigation, C. L.: investigation, I. D. R.: investigation, writing, L. M.: investigation, writing, L. D.: supervision, writing, R. M. G.: supervision, writingoriginal draft, M. T.: supervision, conceptualization, writing.

Table 1 .

 1 Experimental and calculated17 O NMR parameters for 1

-Cl and 1-Me

	Speci es		CS (ppm)	C Q (MHz)	 Q	 CSA	 CSA
	1-Cl	exp.	782 (±2)	2.7 (±0.2)	0.5 (±0. 2)	555 (±10)	0.2 (±0.1)
		calc.	769	2.9	0.4	789	0.9
	1-Me	exp.	675 (±2)	0.2 (±0.2)	0.2 (±0.1)	270 (±30)	0.2 (±0.2)
		calc.	655	0.36	0.7	456	0.3

Table 2 .

 2 Structure -NMR parameters relationships for oxo species (error margins are omitted for the

	sake of clarity)
	Species	CS (ppm)	C Q (MHz)	 CSA (ppm)	Ref.
	[WOCl 4 ]	671	1.0	-330	16
	[(SiO) 2 WOCl 3 ]	828	<1.3	-350	16
	[(SiO)WOCl 2 ]	810	<2.0	-640	16
	[(SiO)WO(CH 2 CMe 3 ) 3 ]	757	5.3	-1136	18
	[(SiO)WO(CH 2 SiMe 3 ) 3 ]	774	5.2	-1110	19
	[(SiO) 2 WO(CH 2 SiMe 3 ) 2 ]	766	5.5	-1062	7
	[WOCl(CH 2 CMe 3 ) 3 ]	735	5.1	-1110	18
	[WO{OSi(OtBu) 3 }(CH 2 CMe 3 ) 3 ]	731	5.44	-1128	18
	[O(WO(CH 2 CMe 3 ) 3 )]	775	4.6	-1112	18
	[WOCl 2 (OSitBu 3 ) 2 ] (1-Cl)	782	2.7	555	This work
	[WOMe 2 (OSitBu 3 ) 2 ] (1-Me)	675	0.2	270	This work
	Over the scope of structures studied by 17 O NMR, chemical shift values are observed within the 828-
	675 ppm range. Noteworthy, though [WOCl 4

  Complex 1-Cl features a τ value of = 0.13, thus being close to square pyramidal, while 1-Me yields a τ value of = 0.64, thus leaning toward a trigonal bipyramidal configuration. For comparison, the τ value is of 0.57 in [WO(n-Bu) 2 (OSitBu 3 ) 2 ]. Thus, the impact of these distinct geometries for 1-Cl and 1-Me is a significant difference in quadruplar coupling constant (respectively of 2.7 and 0.16 MHz). Interestingly, DFTcalculated C Q value for isolated molecules of [WOCl 4 ] (of square pyramidal geometry) is 1.8 MHz,

comparable to the experimental value of 1-Cl. This illustrates how this anisotropic parameter can be a better descriptor than isotropic chemical shift, when characterizing terminal oxo species. Moreover, it also demonstrates the advantage of relying on solid-state MAS rather than on liquid state NMR spectroscopy, as it provides anisotropic parameters, as illustrated by the study on a series of vanadium oxo derivatives featuring alkyl and siloxide groups, where

  If surface silanols react with W-Me or W-OSitBu 3 moieties, this affords respectively [(SiO)WOMe(OSitBu 3 ) 2 ] (with methane release) or [(SiO)WOMe 2 (OSitBu 3 )] (with tBu 3 SiOH release). The silica used as a support in this case is Aerosil 200 from Evonik, which was partially dehydroxylated under vacuum at 700 °C (SiO 2-700

Immobilization of 1-Me may proceed via distinct pathways, such as the W-C or W-O silanolysis.

1 -

 1 Me was reacted with SiO 2-700 at room temperature in pentane, affording material 2 as a pale-yellow powder. Gas phase analysis showed no trace of methane released in the grafting process. Elemental analysis indicates W and C loadings of 3.31 and 3.71 w%, which correspond to 17 C/W within the material. This is in line with the formation of [(SiO)WOMe 2 (OSitBu 3 )] (15 C/W), resulting from HOSitBu 3 release. This silanol compound was indeed observed by1 H NMR analysis of the supernatant liquid from the grafting reaction. The tungsten loading is lower than that of related materials, such as 4.02 w% for [(SiO)WO(CH 2 tBu) 3 ], for instance. This latter compound results from the grafting of WOCl(CH 2 tBu) 3 on SiO 2-700 , which proceeds with full silanol consumption. Thus, the silanol reaction is unlikely to be complete in the case of 1-Me grafting, most probably due to the severe steric hindrance from the OSitBu 3 groups. The uncomplete SiOH consumption is confirmed by IR studies indicating partial consumption of the silanols (Figure

  17 O solid-state NMR spectra were acquired on a Bruker Avance II 400 ( 1 H, 400.13 MHz;17 O, 54.27 MHz) and Avance III 800 ( 1 H, 800.13 MHz, 17 O, 108.47 MHz) spectrometers, using a single pulse sequence (Avance II 400 : pulse excitation of 5 µs at an RF field strength of 60 kHz, Avance III 800:pulse excitation of 4 µs at an RF field strength of 60 kHz) and 3.2 mm rotor diameter. No proton decoupling was applied. The recycle delay was 0.5 sec. Schlenk tube in order to quantify methane evolved during grafting. The powder was then dried at 25 °C under static vacuum for 1 h. Analysis of the gas phase by gas chromatography indicated the formation of only traces of CH 4 during the grafting. Elemental analysis: W 3.31 %wt; C 3.71 %wt.

	Preparation and characterization of 2. A mixture of finely ground 1-Me [WOMe 2 (OSitBu 3 ) 2 ] (134
	mg, 0.203 mmol) and SiO 2-200 (545 mg) was stirred at 40 °C (5 h) under dynamic vacuum whilst all
	volatile compounds were condensed into a cold trap. Pentane was then added and the solid was
	washed 5 times. The resulting yellow powder was dried under vacuum (10 -5 Torr) and transferred to a
	500 mL Simulation of 17 O MAS NMR spectra. All 17 O MAS NMR numerical spectra were calculated using
	SOLA module included in TopSpin software package, using Haeberlen chemical shift tensor
	convention.

Acknowledgement

This work was principally financed by the gence Nationale de la echerche ( N -12-S07-0021-01, O OC T). The CN S, French inistry of esearch and igher ducation, Institut de chimie de Lyon, Chevreul Institute (F 2638), gion Nord-Pas de Calais, and FEDER are acknowledged for their supplementary support. Financial support from the IR-RMN-THC FR 3050 for conducting the research is gratefully acknowledged. L.M. is member of the Institut Universitaire de France. This work was performed using HPC resources from CALMIP (Grant 2016-p0833).

Conflict of interest

No conflict of interest to declare.


Solène Stoens
email: solene.stoens@femto-st.fr

Rémi Daudin

Alexis Lenain

Sébastien Gravier

Guillaume Colas

Pierre-Henri Cornuault

Cr content of the sliding counterpart as a way to control friction of Ni62Nb33Zr5 Bulk Metallic Glass

Keywords: Tribology, Bulk Metallic Glass, Friction, Wear

Bulk Metallic Glasses (BMG) are known to demonstrate exceptional mechanical properties combining very high yield stress and fracture toughness with large elastic strain limit. There is, however, no consensus regarding the suitability of BMG for tribological applications, because they are said to exhibit erratic behavior in friction. The present study proposes to control friction of Ni62Nb33Zr5 BMG by controlling the Cr content of the sliding steel ball. Different steels demonstrating similar C content, but different Cr contents were chosen. Results confirm that Cr can greatly influence the friction coefficient while keeping very low wear.

Introduction

Metallic glasses (MG), also known as amorphous metallic alloys (AMA), were first obtained as ribbons in the 60's by quenching an AuSi melt [START_REF] Klement | Non-crystalline Structure in Solidified Gold-Silicon Alloys[END_REF]. They are now produced in bulk form (BMG) which opens up the possibilities of applications. The wear resistance of BMGs as compared to crystalline alloys is highly debated and somewhat unpredictable. Nonetheless two recent studies conducted respectively at the nanoscale [START_REF] Caron | Structure vs chemistry: Friction and wear of Pt-based metallic surfaces[END_REF] and at the macroscale [START_REF] Cornuault | On the diversity of accommodation mechanisms in the tribology of Bulk Metallic Glasses[END_REF] are suggesting that it is possible to control friction and wear of BMG by carefully selecting the counterpart based on its elemental composition. The present paper focuses on Ni62Nb33Zr5 BMG and on the Cr content of the steel counterpart to verify experimentally if such assumption is relevant.

Methods

One Ni-based (Ni62Nb33Zr5) and three different steels compositions (C90, 100Cr6, and X105CrMo17) are used in this study. Those alloys were chosen because of their respective content in Cr and C (Table 1). They also demonstrate similar mechanical properties. Ni62Nb33Zr5 plate were tested under dry sliding condition against 5 mm steel ball, in reciprocating linear motion with a ± 1 mm displacement stroke at 1 Hz, and during 10,000 backward-and-forward friction cycles. A constant normal force FN = 0.25 N was applied using dead loads.

After the test, surface topography characterization of every friction tracks were performed using a variable focus optical microscope. Wear volumes of the ball and the plate are tentatively calculated. Friction track were also analyzed by SEM and EDS. The Cr content of the counterpart appears to greatly drive the friction coefficient (Fig 1). The higher the friction is, the higher the Cr content is. This observation is all supported by Cr/Fe ratio that is higher inside the friction track as compared to the initial composition of the steel. Meanwhile, attempts to quantify the wear of both BMGs and steel counterparts revealed infructuous even through highly resolved measurement method.

Results and discussion

The study shows that BMG can exhibit low friction and low wear, and in a reproducible manner, which opens up many possibilities for tribological applications where they are foreseen to be used.

Figure 1 :

 1 Figure 1: Friction coefficient of the Ni62Nb33Zr5 sliding against different steel balls.

Table 1 :

 1 Counterparts chemical composition

	Steel	C	Cr
	X105CrMo17	0.95-1.20	16.00-18.00
	100Cr6	0.95-1.05	1.40-1.65
	C90	0.9	0

th World Tribology Congress, WTC 2021 September 5-10, 2021, Lyon, France


Qingxiang Ji

Yunchao Qi

Chenwei Liu

Songhe Meng

Jun Liang

Muamer Kadic

Guodong Fang

Design of thermal cloaks with isotropic materials based on machine learning

Keywords: Transformation thermotics, Thermal cloak, Artificial neural network

à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Introduction

Thermal manipulation has recently attracted wide attention and researches following the pioneering works of transformed theory [START_REF] Pendry | Controlling electromagnetic fields[END_REF][START_REF] Fan | Shaped graded materials with an apparent negative thermal conductivity[END_REF][START_REF] Chen | Cloak for curvilinearly anisotropic media in conduction[END_REF][START_REF] Guenneau | Transformation thermodynamics: cloaking and concentrating heat flux[END_REF][START_REF] Farhat | Ultrabroadband elastic cloaking in thin plates[END_REF][START_REF] Kadic | Metamaterials beyond electromagnetism[END_REF]. Many novel thermal meta-devices are created, like invisible cloaks, sensors and illusion devices [START_REF] Kadic | Plasmonic space folding: Focusing surface plasmons via negative refraction in complementary media[END_REF][START_REF] Schittny | Experiments on transformation thermodynamics: molding the flow of heat[END_REF][START_REF] Schittny | Invisibility cloaking in a diffusive light scattering medium[END_REF][START_REF] Shen | Thermally hiding an object inside a cloak with feeling[END_REF][START_REF] Yang | Invisible sensors: Simultaneous sensing and camouflaging in multiphysical fields[END_REF][START_REF] Xu | Achieving arbitrarily polygonal thermal harvesting devices with homogeneous parameters through linear mapping function[END_REF][START_REF] Qin | Experimental demonstration of irregular thermal carpet cloaks with natural bulk material[END_REF][START_REF] Hu | Illusion thermotics[END_REF][START_REF] Zhou | Thermal illusion with twinbornlike heat signatures[END_REF][START_REF] Huang | Macroscale thermal diode-like black box with high transient rectification ratio[END_REF][START_REF] Xu | Controlling thermal waves with transformation complex thermotics[END_REF]. Thermal meta-devices face the challenge of extreme constitutive properties. Most reported devices are realized by metamaterials with unconventional thermal conductivity, i.e., anisotropic and graded. Yet practical applications desire materials with realistic physical properties. Researchers have proposed many fruitful strategies to design thermal meta-devices with bulky material compositions, such as composite structures design [START_REF] Schittny | Experiments on transformation thermodynamics: molding the flow of heat[END_REF][START_REF] Narayana | Heat flux manipulation with engineered thermal materials[END_REF][START_REF] Ji | Designing thermal energy harvesting devices with natural materials through optimized microstructures[END_REF][START_REF] Ji | Achieving thermal concentration based on fiber reinforced composite microstructures design[END_REF], scattering-cancellation approach [START_REF] Han | Experimental demonstration of a bilayer thermal cloak[END_REF][START_REF] Xu | Ultrathin three-dimensional thermal cloak[END_REF][START_REF] Xu | Bilayer thermal harvesters for concentrating temperature distribution[END_REF][START_REF] Zhou | Binary masses manipulation with composite bilayer metamaterial[END_REF] and neutral inclusion method [25, 26, 1 liangjun@bit.edu.cn, fanggd@hit.edu.cn [START_REF] Zhang | A bilayer thermal-electric camouflage device suitable for a wide range of natural materials[END_REF][START_REF] Ji | Thermal cloaking of complex objects with the neutral inclusion and the coordinate transformation methods[END_REF]. However, these design schemes are still not easy to implement, as they need complex alternating layer shapes or they have low topological property and finite functionalities. Considering that these direct strategies possess drawbacks in technical realization, researchers have developed inverse design methodology. Inverse design approach features its advantage over other methods in that it allows to take into account various kinds of constraints on solutions including those related to technical realization [START_REF] Alekseev | Particle swarm optimization-based algorithms for solving inverse problems of designing thermal cloaking and shielding devices[END_REF][START_REF] Jin | Particle swarm optimization for realizing bilayer thermal sensors with bulk isotropic materials[END_REF]. Topology optimization is introduced into the inverse design of thermal meta-devices, demonstrating simplified material properties and excellent performances [START_REF] Fujii | Exploring optimal topology of thermal cloaks by cma-es[END_REF][START_REF] Fujii | Optimizing the structural topology of bifunctional invisible cloak manipulating heat flux and direct current[END_REF][START_REF] Fujii | Topology-optimized thermal carpet cloak expressed by an immersed-boundary level-set method via a covariance matrix adaptation evolution strategy[END_REF][START_REF] Fujii | Cloaking a concentrator in thermal conduction via topology optimization[END_REF], whereas, topology optimization method usually results in complex structural configuration that imposes difficulties to fabrications. In addition, conventional optimization usually encounters the local minima problem and needs a well-defined objective function for accurate design [START_REF] Ahmed | Deterministic and probabilistic deep learning models for inverse design of broadband acoustic cloak[END_REF]. New design schemes are required with the purpose to simplify engineering preparations and reduce the computational workloads.

In this work, we propose a data driven approach to design thermal cloaks with bulk isotropic materials. A multilayered concentric cloak is designed where each layer is composed of different isotropic materials. An artificial neural network is proposed and trained to intelligently learn the intrinsic relation between input material parameters and their influences on cloaking performances [START_REF] Ahmed | Deterministic and probabilistic deep learning models for inverse design of broadband acoustic cloak[END_REF][START_REF] Liu | Thermal transparency with periodic particle distribution: A machine learning approach[END_REF]. The network proves effective by accurately learning intrinsic relations from a small number of samples, and is efficient in significantly reducing computation time by predicting solutions immediately after the training phase [START_REF] Ahmed | Deterministic and probabilistic deep learning models for inverse design of broadband acoustic cloak[END_REF]. By using deep learning we have exploited the intricate relationship between each layer's material properties and general cloaking performances. Optimal material properties of each layer are retrieved, and the optimized thermal cloak not only simplifies practical fabrication, but demonstrates excellent heat cloaking effects in both simulations and experiments.

Methods and results

Design scheme

We consider a cylindrical thermal cloak with a concentric shell configuration. The goal is to render the object (indicated in white in Fig. 1a) thermally invisible, without disturbing original thermal profiles. Basically, one can achieve this goal in one of following ways: preset layer thickness and find the optimal material properties, or choose shell materials and determine the optimal layer thickness, or use both layer thickness and material properties as design variables. Here we choose the first approach and build a thermal cloak with four layers where each layer is made of different materials but with equal thickness, as illustrated in Fig. 1a. The design space is characterized by each layer's thermal conductivity k m , where m is the layer index. Note that the deep learning model (as shown later) is readily applicable to thermal cloaks with different number of layers.

The heat conduction equation in cylindrical system is expressed as

∂ 2 T 0 ∂r 2 + 1 r ∂T 0 ∂r + 1 r 2 ∂ 2 T 0 ∂θ 2 = 0 (1) ∂ 2 T m ∂r 2 + 1 r ∂T m ∂r + 1 r 2 ∂ 2 T m ∂θ 2 = 0 (2)
where the subscript 0 denote the central region and m = 1, 2, 3, 4, 5 denote regions from the center to outermost.

Considering the symmetry of boundary conditions, the temperature distributions in different regions can be expressed as

T 0 = A 0 + B 0 r cos θ + C 0 r -1 cos θ, (3)
T m = A 0 + B m r cos θ + C m r -1 cos θ, (4)
where A 0 is the known temperature of the central point, B 0 , B m and C m are unknown coefficients to be determined. Boundary continuity conditions of temperature and normal heat flux require

       T m-1 r=r m = T m r=r m -k m-1 ∇T m-1 r=r m = -k m ∇T m r=r m . (5)
Combining Eq. ( 4) and Eq. ( 5), we obtain the simplified form

B m-1 r m + C m-1 r -1 m = B m r m + C m r -1 m -k m-1 B m-1 -C m-1 r -2 m = -k m B m -C m r -2 m (6)
Generally, a thermal cloak should accomplish following goals: (a) guiding heat flows to detour without invading the object; (b) directing heat flows to return to their original paths without disturbing external thermal profiles. Considering perfect thermal neutrality effects (no perturbations to external thermal field), we have C 0 = C 5 = 0, and B 5 can be easily obtained by the applied uniform thermal gradient. We now have nine unknown coefficients to be determined but have ten equations, which will result in a matching condition between material properties k 0 , k m and geometry parameters r i (see the supporting information). Thermal cloaking effects are achieved if all the material properties and structural parameters completely match this criterion. In theory, we can find the analytical expression of Eq. ( 6). However, it may be tough to determine the material properties that simultaneously achieve undisturbed external fields and zero temperature variations in the central region, especially in the case of large number of layers, more complicated shapes or under material property constraints. Besides, the material properties are associated with each other and there may exist multiple potential solutions. The influences of material properties k m on thermal cloaking performances can be revealed intuitively by Eq. ( 6). A practical implementation may demand flexibility in the design due to external perturbation, i.e., unavailability of material properties. For a given object and predefined geometry, the analytical solution may be not well-satisfied due to such external perturbations, hence a local optimal solution is indeed needed. We notice that there exists a mapping relation between each layer's materials properties and the cloaking performances. Hence we turn the inverse problem into an optimization problem and reversely design the material properties that results in thermal cloaking effects.

To quantitatively demonstrate the thermal cloaking effects, two objective functions are defined, one to characterize the thermal difference within the ob-ject domain:

∆T = T x=r 1 -T x=-r 1 , (7)
and the other to characterize thermal neutrality of the cloak:

M V = Ω |T (x, y, z) -T r (x, y, z)| dΩ Ω dΩ , (8)
where Ω represents the probe domain of external fields r > r 5 , and T r denotes the reference thermal field of a homogeneous plate as

T r = T H -T H -T L L (x + L 2 ).
In our design, thermal properties of the central region and background region are respectively k 0 = 394 Wm -1 K -1 and k 5 = 77.6 Wm -1 K -1 , the sidelength is L = 0.125 m, the inner radius is r 1 = 0.025 m and the outer radius r 5 = 0.05 m. Considering fabrication easiness and availability, we have defined ranges of the design parameters as 0.15 < k 1 < 27, 360 < k 2 < 394, 0.15 < k 3 < 27, 360 < k 4 < 394 in units of Wm -1 K -1 [START_REF] Schittny | Experiments on transformation thermodynamics: molding the flow of heat[END_REF]. We mention by passing that broader ranges may decrease the prediction efficiency, but this can be compensated by building more data samples. We denote the original design space by the symbol D 0 = {k 1 , k 2 , k 3 , k 4 }. The goal is to find an optimal set of parameters k m within the constraint design space D 0 = {k 1 , k 2 , k 3 , k 4 }. Generally, the optimization objective should be illustrated as:

min M V min ∆T S.t. k m ∈ D 0 . (9)
Perfect cloaking performances are achieved when optimized design parameters yield zero M V and ∆T . However, we notice that M V and ∆T may achieve minimal values at different points, rendering no solutions to Eq. ( 9). Therefore, the objective is accomplished in following two steps.

First, we obtain a design space D * within which the samples have values of M V infinitely approach the minimal value, which can be illustrated as:

M V → M min V S.t. k m ∈ D 0 . ( 10
)
where M min V denotes the minimum value within the samples space D 0 .

Then we search for the optimal design parameters that yields minimum ∆T within the design space D * , which can be illustrated as:

min ∆T S.t. k m ∈ D * . ( 11
)

Artificial neural network

We propose an artificial neural network to learn the intrinsic relations between the design parameters and the thermal cloaking performances (see Fig. 1b). The forward neural network maps the design space [k 1 , k 2 , k 3 , k 4 ] (the input layer) to the results space [M V , ∆T ] (the output layer). For the hidden layer, the number of layer nodes is determined by an empirical formula:

N = √ n 1 + n 2 + δ, (12)
where n 1 and n 2 are the number of layer nodes for the input layer and output layer, respectively, δ is an empirical constant. We obtain the number of layer nodes N = 6 following Eq. 12. Details about the structure of the artificial neural network can be found in the supporting information.

Optimal Latin hypercube sampling technique is used to obtain 1000 sample control points. The created sample points spread evenly in the design space, which adds more prediction accuracy to the deep learning model. We solved the direct problem [k 1 , k 2 , k 3 , k 4 ] numerically by the commercial software COMSOL Multiphysics and got corresponding values of M V and ∆T for the control points. We train the artificial neural network with the relation from each layer's material properties to the cloaking performances using the obtained samples, which are split into three sets: for training (70%), for validation (15%) and for final testing (15%), respectively. The input data are normalized and then fed into the network to expedite the convergence of the algorithm. Mean square error (MSE) is used as the loss function between the predicted and desired output. However, we notice that it is impossible to build an effective prediction model between the input parameters and the two output index (see the supporting information). This is physically explained by the fact that there does not exist a well-predicted intrinsic relation between each layer's material properties k m and thermal difference ∆T . Therefore, we instead establish the artificial neutral network only predicting the dependence of thermal neutrality of M V on material properties k m . Levenberg-Marquardt algorithm is selected as the training algorithm. The loss functions of training , validation and testing set vary with the number of iterations as shown in Fig. 2a. The loss function converges gradually after 400 epochs, implying completion of the training phase. The three loss function match well with each other, indicating that the artificial neural network is smooth without overfitting. Mean relative errors (MRE) on the samples are shown in Fig. 2(b-d) and listed in the inset table, where we observe that all the three sets of MREs are less than 2.3%. These results demonstrate high prediction accuracy and reliability of the artificial neural network on single output layer M V .

We then turn to consider the output parameter ∆T . In practice, feasible material parameters are often desired with least temperature differences ∆T . Yet it is ineffective here to directly train the proposed artificial neural network in an inverse direction, either to derive a set of optimal design parameters D by an inverse-mapping. To avoid such a pitfall, we generate a new set of 10000 design samples as the input of the network, using the relation we have established between M V and k m . Note that M V of the 1000 original samples are got by finite element method, while for the 10000 new samples, the objective function M V are obtained by the network directly. The process of searching for the optimal values is completed in the 10000 new samples. Considering that ∆T is not well-predictable by the artificial network, we first filter out the 1% samples that result in least M V values and finally obtain the particular set of parameter that yields minimal ∆T from the selected 1% samples. We note by passing that it takes 76 seconds to generate the 10000 new samples by the network, whereas finite element analysis requires around 13 minutes.

= [k 1 , k 2 , k 3 , k 4 ] from the target functions R = [∆T, M V ]
We obtain one set of optimal design parameters as k 1 = 23.11, k 2 = 386.58, k 3 = 5.91 and k 4 = 394 in units of Wm -1 K -1 . To verify the design method effective, we establish a thermal cloak of which each layer is constituted by the optimal material properties. We conduct numerical simulations and compare the results with the ideal cloak, the bare obstacle case and the homogeneous plate (see Fig. 3). Note that the ideal cloak here refers to a thermal cloak designed by transformation thermotics theory [START_REF] Pendry | Controlling electromagnetic fields[END_REF][START_REF] Guenneau | Transformation thermodynamics: cloaking and concentrating heat flux[END_REF]. It is observed that the optimized thermal cloak successfully guides heat flows to pass around the object and return to their original paths. For the optimized cloak, the temperature field in probe domain Ω shows few perturbations and are analogous to the field generated by the homogeneous plate. By contrast, the thermal field are drastically distorted in the case of a bare object. In addition, the optimized thermal cloak closely mimics the ideal cloak and significantly reduces the temperature differences in the inner domain, validating effectiveness of the design. We conduct quantitative analysis and show the calculated objective functions for different cases, as shown in Tab. 1. The results clearly show that the designed cloak significantly reduces the heat flux that invades the object and demonstrates excellent neutrality performances.

Experimental validation

The material properties of each layer and the background medium are not readily available by naturally existing materials. To obtain desired thermal con-

k 5 = k c 1 + 2(k p -k c) f k p +k c -(k p -k c) f
, where f denotes holes area fraction. The sample is manufactured by CNC machining technique, as shown in Fig. 4. Note that refined circular discretization of each layer can better approximate the required thermal properties, but at the same time results in more fabrication complexity. We have fabricated a thermal cloak with finite holes or arc grooves shown in Fig. 4c as a good trade-off.

In Fig. 4, we show the experimental system used to verify the performances of the designed thermal cloak. An infrared thermal camera (FLIR A6702sc) is used to capture thermal images via Planck thermal emission. The hot and cold ends are realized by thermostat water bath, remaining sides are left open and covered with PDMS layer of thickness around 1 mm. Heat convection between the samples and the surroundings are significantly reduced by this PDMS layer.

In Fig. 5, we show the numerical and experimental results for the proposed thermal cloak. It is observed that the thermal cloak successfully fulfills its task in that heat flux are guided to pass around the central region without invasion. The heat density are reduced in the central region than its surroundings. Furthermore, the temperature field outside of the device are almost not affected, as if nothing was there. Quantitative results plotted in Tab. 2 further verified the effectiveness of our designed cloak, where both temperatures difference in the central region and external temperature perturbations are minimized. The experimental results agree well with simulation re- sults, indicating the accuracy of the artificial neural network enabled design approach. We note slight discrepancies between simulations (see Tab. 1) and experimental results (see Tab. 2). The difference is mainly caused by fabrication errors and inaccuracy in temperature controlling systems.

Conclusion

We have proposed the design method of a multilayered thermal cloak with core-shell configuration driven by deep learning. In particular, we establish an artificial neural network to predict the cloaking responses for given material properties. Optimal material properties are retrieved for target cloaking effects. We implement an optimized thermal cloak with bulk isotropic materials and verify excellent heat cloaking performances by both simulations and experiments, validating the effectiveness of our design method. The proposed method can be extended to other static physical fields, such as acoustic waves and electromagnetic field, suggesting an efficient route to design cloaks and related meta-devices.

Fig. 1 .

 1 Fig. 1. Framework of the deep learning model for the design of thermal cloaks. (a) The design scheme. (b) The artificial neural network.

Fig. 2 .

 2 Fig. 2. Artificial neural network learning process. (a) The learning curves as a function of training epochs. (b) Histogram of relative errors for the testing samples.

Fig. 3 .

 3 Fig. 3. Thermal profile for (a) the bare obstacle, (b) ideal thermal cloak, (c) the homogeneous plate and (d) the optimized cloak; (e) corresponding temperature profile along the observed line y = 0.

Fig. 4 .

 4 Fig. 4. The experimental system. (a) An infrared thermal camera is used to capture thermal images. The designed thermal cloak: (a) the numerical model and (b) the photograph.

Fig. 5 .

 5 Fig. 5. Simulated and measured temperature distributions: (a) simulated results for a bare obstacle; (b) Experimental results for a bare obstacle; (c) simulated results for the designed cloak; (d) Experimental results for a bare obstacle. The white lines denote iso-temperature lines. The object and cloak are outlined by black dash lines.

Table 1

 1 Comparison of cloaking performances for different cloaks.

		Ideal cloak Homogeneous plate Bare obstacle Optimized cloak
	M V (K) 4.9×10 -7	7.6×10 -10	1.3	0.1
	∆T (K)	0	20	7.2	1.5
	ductivity, we design composite structures by drilling
	holes into the copper plate (thermal conductivity k c =
	394 Wm -1 K -1 , thickness 2 mm) and filling them
	with polydimethylsiloxane (PDMS, thermal conduc-
	tivity k p = 0.15 Wm -1 K -1 ) [8]. For example, back-
	ground heat conductivity k 5 is achieved by building
	holes array (holes diameter 1.8 mm) with equal space
	(2 mm). The holes array parameters are obtained fol-
	lowing Maxwell-Garnett theory which is expressed

Table 2

 2 Experimental results of the cloaking performances, with the bare obstacle case as reference.

		Bare obstacle Ideal cloak
	M V (K)	1.38	0.11
	∆T (K)	5.4	2.2

Acknowledgments

This work was supported by the National Natural Science Foundation of China (Grant Nos. 11732002 and 12090034). We are also grateful to Natural Science Foundation of Heilongjiang Province of China (Grant Nos. YQ2021A004).

CRediT authorship contribution statement

Qingxiang Ji: Conceptualization, Formal analysis, Writing original draft. Yunchao Qi: Methodology, Software. Chenwei Liu: Formal analysis, Writing original draft. Songhe Meng: Investigation, Visualization, Validation, Data curation. Jun Liang: Investigation, Visualization, Project administration. Muamer Kadic: Simulations and revision. Guodong Fang: Supervision, Project administration, Review and editing.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.


Jean-François Faucher

Cristina Socolovschi

Camille Aubry

Catherine Chirouze

Laurent Hustache-Mathieu

Didier Raoult

Bruno Hoen

J.-F Faucher

Brill-Zinsser Disease in Moroccan Man, France, 2011

To the Editor: Epidemic typhus is caused by Rickettsia prowazekii and transmitted by human body lice. For centuries, it has been associated with overcrowding, cold weather, and poor hygiene. Brill-Zinsser disease is a recurrent form of epidemic typhus that is unrelated to louse infestation and develops sporadically years after the primary illness. Clinical features are similar to, but milder than, those of epidemic typhus [START_REF] Bechah | Epidemic typhus[END_REF]. We report a case of Brill-Zinsser disease in a patient who was born in Morocco and had no history of epidemic typhus.

A 69-year-old man living in France sought care from his general practitioner on March 7, 2011, after 2 days of high-grade fever (40°C) associated with headache, myalgia, fatigue, and mild cough. Amoxicillin was prescribed for a putative diagnosis of acute respiratory infection.

He was admitted to hospital on March 9 for persistent fever. Physical examination results were unremarkable. Blood test results were as follows: C-reactive protein 111 mg/L (reference 0-8 mg/L); procalcitonin 0.49 ng/mL (reference 0.1-0.4 ng/mL), lymphocyte count 0.7 × 10 3 cells/μL (reference 1-4 × 10 3 cells/μL), platelet count 92 × 10 The patient had been raised in Morocco. At 19 years of age, he emigrated to France, where he lived in a urban area. He subsequently traveled every 3 years to Morocco for 1-month summer holidays, always in urban areas. He had most recently traveled to Morocco in 2008. He denied any history of hospitalization for a severe febrile illness and any exposure to louse bites. In the weeks before disease onset, he had not taken any new drug. He had no immunoglobulin defi ciency.

On the basis of serologic analysis with Western blot, we confi rmed R. prowazekii infection in a patient with no recent travel and no contact with lice or fl ying squirrels. R. prowazekii infection may occur rarely in France; it was found in Marseille in 2002 in an asymptomatic homeless person (3). In contrast, the patient in our report was living in a hygienic environment, and an autochthonous infection is therefore highly unlikely.

Epidemic typhus was endemic to North Africa until the 1970s (4). Subsequently, this region was thought to be free from epidemic typhus, but 2 cases have been reported since 1999 in Algeria, where 1 case of Brill-Zinsser disease was observed in a man who had had epidemic typhus in 1960 during the Algerian civil war [START_REF] Niang | Epidemic typhus imported from Algeria[END_REF][START_REF] Mokrani | Reemerging threat of epidemic typhus in Algeria[END_REF][START_REF] Stein | Brill-Zinsser disease in France[END_REF]. Few published data exist about the seroprevalence of R. prowazekii infections in North Africa [START_REF] Letaïef | Epidemiology of rickettsioses in North Africa[END_REF]. In Tunisia, no epidemic typhus was found in 2005 among 47 febrile patients [START_REF] Kaabia | Serologic study of rickettsioses among acute febrile patients in central Tunisia[END_REF]. However, a seroepidemiologic survey performed in blood donors and hospitalized patients in the Aures, Algeria, found a prevalence of 2% (4). This fi nding suggests that R. prowazekii infection might have occurred in this population more often than suspected. No recent published data are available from Morocco.

Since 1970, reports of only 8 cases of Brill-Zinsser disease have been published (9,[START_REF] Mcquiston | Brill-Zinsser disease in a patient following infection with sylvatic epidemic typhus associated with fl ying squirrels[END_REF]. In all cases, known risk factors were present (overcrowding, poor hygiene, or contact with fl ying squirrels). Brill and Zinsser described that stress or waning immunity could reactivate R. prowazekii infection (2). Corticosteroids can trigger recurrence of R. prowazekii in mice [START_REF] Bechah | Adipose tissue serves as a reservoir for recrudescent Rickettsia prowazekii infection in a mouse model[END_REF], but no such observations were made in humans. In the case presented here, we found no stress factor, no immunosuppression, and no medical history of epidemic typhus.

Brill-Zinsser disease can develop >40 years after acute infection. The mechanism of R. prowazekii latency has not been established. A recently explored reservoir for silent forms of R. prowazekii infection is adipose tissue because it contains endothelial cells, which are the target cells for R. prowazekii infection, and because of its wide distribution throughout the body [START_REF] Bechah | Adipose tissue serves as a reservoir for recrudescent Rickettsia prowazekii infection in a mouse model[END_REF]. Brill-Zinsser disease should be considered as a possible diagnosis for acute fever in any patient who has lived in an area where epidemic typhus is endemic.

Temperate Climate Niche for Cryptococcus gattii in Northern Europe

To the Editor: Cryptococcus gattii was considered to be geographically restricted to countries with tropical and subtropical climates until 1999, when an outbreak of cryptococcosis in humans and animals occurred in the temperate climate of Vancouver Island, British Columbia, Canada (1). Montagna et al. reported the fi rst environmental C. gattii in Europe from the Mediterranean region of Italy; these authors isolated it from 11 (4.3%) of 255 samples of plant detritus of Eucalyptus camaldulensis trees collected from the residential locality of an autochthonous case of cryptococcal meningitis caused by C. gattii in Apulia (2). These observations were recently substantiated by the isolation of C. gattii from plant debris of trees belonging to Ceratonia siliqua (carob), Pinus halepensis (stone pine), and E. camaldulensis in Spain (3). We report environmental isolation of the primary pathogenic fungus C. gattii from a forest in Berg en Dal, the Netherlands, which extends its geographic distribution to the temperate climate of northern Europe.

We investigated 112 decayed wood samples collected from inside trunk hollows of 52 living trees belonging to 5 families during April-May 2011 in Nijmegen, the Netherlands. The trees sampled were chestnut (Castanea sativa, n = 24), Douglas fi r (Pseudotsuga menziesii, n = 17), oak (Quercus macranthera, n = 6), walnut (Juglans regia, n = 3), and mulberry (Morus alba, n = 2). The main criterion in selecting a tree for sampling was advanced age and presence of large trunk hollows variably sheltered from sunlight. The sampled sites had no bird nests and were apparently free from avian excreta. The decayed wood samples were collected with an in-house swabbing technique by using simplifi ed Staib niger seed agar as described (4). The plates were incubated at 30°C and periodically observed up to 7 days for isolation of C. gattii and C. neoformans. Suspected colonies of Cryptococcus spp. were purifi ed by dilution plating and identifi ed by their morphologic and biochemical profi les, including development of blue color on L-canavanine-glycine bromothymol blue medium.

Identity of the isolates was confi rmed by sequencing the internal trascribed spacer and D1/ D2 regions, and they were genotyped by using amplifi ed fragment-length polymorphism (AFLP) fi ngerprinting and multilocus sequence typing (MLST). The MLST loci CAP10, CAP59, GPD1, IGS, LAC1, MPD1, PLB1, SOD1, TEF1α, and URA5 of the environmental C. gattii isolates were amplifi ed and sequenced, and data were compared with MLST data from a large C. gattii population study [START_REF] Niang | Epidemic typhus imported from Algeria[END_REF] and with a recently published set of clinical, animal, and environmental C. gattii isolates from Mediterranean Europe and the Netherlands (Figure) [START_REF] Badiaga | Autochtonous epidemic typhus associated with Bartonella quintana bacteremia in a homeless person[END_REF][START_REF] Mokrani | Reemerging threat of epidemic typhus in Algeria[END_REF][START_REF] Stein | Brill-Zinsser disease in France[END_REF]. In addition, the mating type was determined with PCR by using mating type-specifi c primers for the STE12a and α alleles [START_REF] Kaabia | Serologic study of rickettsioses among acute febrile patients in central Tunisia[END_REF].

  for IgG. Western blot analyses and cross-adsorption studies strongly suggested R. prowazekii as the cause of the man's illness. Quantitative PCR result on DNA extracted from the acute-phase serum was negative (2).

	remained well.
	On the basis of serologic
	results, the following diagnoses
	could be ruled out: viral infections
	(HIV, cytomegalovirus, Epstein-
	Barr virus); tularemia; Q fever;
	leptospirosis; salmonellosis; and
	Legionella,	Mycoplasma,	and
	Chlamydia spp. infections. Acute-
	phase	and	convalescent-phase
	serum samples were positive for
	typhus-group rickettsiae by the
	microimmunofl uorescence	assay
	at the World Health Organization
	Collaborative Center for Rickettsioses
	and Other Arthropod-Borne Bacterial
	Diseases (Marseille, France). A
	microimmunofl uorescence	assay
	showed titers of 100 for IgM and
	6,400
	3 cells/μL (reference 150-450 × 10 3 cells/μL), and lactate
	dehydrogenase 376 U/L (reference
	94-246 U/L). Chest radiograph results
	were normal. Results of 5 blood
	cultures and a urine culture were
	negative. Stupor developed on March
	11. Cerebrospinal fl uid test results
	were normal. Because the patient
	lived near a goat farm, Q fever and
	tularemia were considered plausible
	hypotheses, and oral doxycycline was
	introduced on March 13. The patient
	became afebrile on March 15, and he
	was discharged from the hospital and

Emerging Infectious Diseases • www.cdc.gov/eid • Vol. 18, No. 1, January 2012

Emerging Infectious Diseases • www.cdc.gov/eid • Vol. 18, No. 1, January 2012


Les traumatismes physiques et moraux de la Grande Guerre dans les pièces de Philippe

Fauré-Frémiet : pour une humanité nouvelle Philippe Fauré-Frémiet (1889-1954) est le fils du compositeur Gabriel Fauré et le petitfils du sculpteur Emmanuel Frémiet1 . Il porte donc une lourde généalogie artistique, qu'il va honorer comme auteur. Avant la guerre, hormis quelques productions poétiques, sa carrière dramatique n'a pas commencé ; elle va véritablement s'épanouir à l'issue du conflit, qu'il connaît personnellement comme engagé volontaire, sur le front d'Orient d'abord, puis dans l'Hexagone, comme zouave, revenant avec la croix de guerre2 .

Une grande majorité des pièces qu'il fait jouer, à partir de 1920, porte la mémoire vivante et obsédante de la guerre. Il est d'ailleurs membre de l'association des Ecrivains combattants3 et les premières représentations de ses oeuvres ont lieu sous les auspices du groupement Aide et Protection4 . Ce n'est cependant pas comme témoin qu'il chercherait à faire oeuvre documentaire ; ses créations sont bien fictionnelles et, contrairement au contexte d'euphorie liée à la victoire, de célébration de la guerre et de ses héros, son théâtre s'intéresse davantage à l'intime, aux victimes des conséquences du conflit. Comme tous les autres « écrivains de guerre », il affronte l'épineuse question de la représentation de la mémoire et du trauma, mais comme « écrivain combattant », on attend de sa création une réalité historique, une narration de faits 5 . Or, sa dramaturgie n'est pas historique, mais éthique, « une sorte d'apostolat6 », comme le note un critique, à partir d'histoires singulières, sur l'humanité et son devenir après cette douloureuse fracture.

En abordant les conséquences physiques, psychiques et amoureuses, l'oeuvre de Fauré-Frémiet, loin de toute héroïsation classique, montre implacablement les destructions des corps et des âmes par la guerre. Les personnages d'anciens combattants, mais aussi de civils, de femmes en particulier, ne cherchent pas à retracer le conflit et son déroulement, mais à décrire les ravages de la guerre sur les êtres humains ; en d'autres termes, « ce que l'histoire fait aux hommes7 ». Toutefois, des lueurs d'espoir émergent dans ces pièces souvent pessimistes, lueurs d'espoir liées au pacifisme qui se répand alors, associées à la définition d'un nouvel humanisme, d'une foi retrouvée en l'Humanité, même après la guerre8 .

Corps et guerre

Le corps prend bien sûr une importance centrale dans l'épreuve des combats, largement relatés par les « écrivains combattants », qui veulent démontrer la participation des intellectuels et transmettre le récit vrai de ce que fut le conflit. Comme 15% des écrivains combattants, Fauré-Frémiet est un engagé volontaire, symbole de l' « Union sacrée » qui domine9 , avant de générer une totale désillusion. Dans la Grand'Geste du monde, « épopée en 15 tableaux, un prologue et un épilogue », donnée en 1927, on voit ainsi « les soldats dans leurs tranchées10 » et le « Poilu au créneau11 » ; les éclairages et les bruits de la mise en scène recréent l'atmosphère : « sifflement incessant des balles », « rayon d'un projecteur12 ». Le spectacle traduit ce que les historiens, plus tard, nommeront la « violence » et la « brutalisation » du conflit 13 . La guerre moderne aboutit à une déshumanisation, beaucoup étudiée depuis, mais tout à fait nouvelle pour les contemporains. Ainsi, le Soldat en sentinelle présent dans la pièce a « les pieds dans la boue », il monte la garde dans le froid, subit « le brouillard de balles » et enfin la mort. Cette pièce est toute d'allégories, telle la Mort qui s'avance, dès le début de la guerre, pour prendre possession du monde. On est donc loin du réalisme des descriptions qui caractérise nombre de récits à l'époque, chez Dorgelès ou Barbusse14 , par exemple. Loin aussi des héros magnifiés par les célébrations nationales et certaines productions artistiques, des images de propagande des actualités cinématographiques.

Les épisodes de combats et de tranchées sont nettement moins présents dans son oeuvre que les conséquences qu'ils ont eues sur les individus. Dans cette perspective de réindividualisation des masses anonymes broyées par la guerre, il s'attache en effet à des destins singuliers, qui peuvent bien sûr être tenus pour emblématiques et qui, dans nombre de ses pièces, sont présentés dans des intrigues croisées, simultanées, afin de mettre en scène les divers points de vue des êtres embourbésau sens propre et au sens figurédans la guerre. Sa première pièce, L'Autre Blessure15 , en 1920, inaugure le type qui va être omniprésent dans ses créations : le mutilé. Ici, Adrien se définit comme « un pauvre diable », rentré de la guerre « exténué, blessé, rompu16 ».

Dans la Haute Route, en 1925, « reparaît le souci constant de M. Fauré-Frémiet pour les mutilés de guerre que ce noble coeur n'oublie jamais 17 » : le fils de Patry, un vieux pêcheur, est aveugle et « héros de guerre 18 ». Mais c'est surtout dans Sic vos non vobis, pièce jouée en 1924, que les mutilés occupent une place centrale : « l'un a perdu la vue », c'est Jean ; « l'autre, qui était peintre, a perdu le bras droit19 », c'est Etienne ; un troisième, Candide, est un Africain qui a « été gazé » et depuis a « les poumons (…) en papier mâché20 ».

Ces corps sont « porteurs de la violence de la guerre, de sa pérennité », car Candide présente notamment les « suites de guerre [START_REF] Fouchard | Le Poids de la guerre. Les poilus et leur famille après 1918[END_REF] », ces pathologies développées par les anciens combattants, notamment dues aux gaz, dont on sait qu'ils causèrent des ravages [START_REF] Fauré-Frémiet | étudie, pendant la guerre[END_REF] . Les associations de mutilés se multiplient à partir de 1918 ; un groupe social spécifique se constitue, celui des invalides de guerre, les « ruines vivantes [START_REF] Ph | Sic vos non vobis[END_REF] » qu'évoque Etienne dans Sic vos non vobis. L'édition de la pièce, en 1926, est vendue au « bénéfice de l'Association Générale des Mutilés de la Guerre », mais certains critiques se demandent s'il est bien « opportun de transporter à la scène le sort des épaves qui ont survécu, amoindries, à la catastrophe [START_REF] Schneider | Le 'Gaulois' au théâtre[END_REF] ». Glorifiés par les discours publics, les invalides de guerre sont en réalité marginalisés et au début des années 20, en pleine euphorie des « années folles », les créations qui rappellent les horreurs et les souffrances encore visibles dans les corps sont parfois mal acceptées.

Dans la Grand'Geste du monde, ainsi, les morts se réveillent, à la fin de la pièce, à cause du bruit des fanfares et des défilés, incrédules face à cette joie et à ces célébrations sous l'Arc de triomphe, alors qu'ils ont enduré mille souffrances et payé de leur vie. On peut y déceler une allusion au célèbre « Debout les morts ! » lancé par Maurice Barrès 25 . C'est, peu ou prou, ce que semblent avoir éprouvé les soldats revenus à la vie civile, totalement en décalage avec le monde et la société, des morts parmi les vivants. Cette « geste », qui ambitionne de retracer les actions de héros anonymes, semble marquer la distance entre l'expérience de guerre ancrée dans la mémoire des anciens soldats et l'oubli dans la frénésie de vie des civils 26 . Elle s'oppose également aux discours officiels qui exaltent les héros et leur sacrifice, en occultant la réalité vécue du traumatisme. L'originalité de l'oeuvre de Fauré-Frémiet, au sein de la production des écrivains combattants, est de ne se cantonner ni aux descriptions des combats, ni aux blessures physiques, mais de consacrer l'essentiel de ses intrigues aux blessures de l'âme, aux conséquences psychologiques et affectives de la guerre.

L'âme et la guerre

Les personnages, outre les empreintes dans leur chair, présentent tous des traumatismes psychiques qui concrétisent les répercussions de la guerre, sans oublier la société civile. Ce sont d'abord les mères éplorées, voyant partir leur fils à la guerre, dans la Grand'Geste du monde.

Mathilde, dans Sic vos non vobis, est veuve de guerre. Le personnage féminin de l'Exilé, « Elle », attend son mari, encore prisonnier en Allemagne, même si la guerre est finie et que leur « petit [est] (…) mort de misère, pendant la guerre27 ». L'écriture recourt aux pronoms personnels pour désigner les personnages dans cette très courte pièce, ce qui contribue à généraliser le propos au-delà d'une identité particulière et peut mettre à distance l'héroïsation stérile de la mémoire officiellecelle des monuments aux morts par exemple.

Le fils de Madeleine, dans Sic vos non vobis, le petit Jeannot, est lui aussi mort de froid et de faim pendant la guerre, même si sa mère s'est prostituée pour tenter de le soigner. La Femme, dans la scène IV de la 2 e partie de la Grand'Geste du Monde, narre les affres de sa vie loin de l'Homme, le manque de lait pour nourrir leur enfant passé tout près de la mort. De l'autre côté de la scène, l'Homme, dans sa tranchée, se demande comment vont sa femme et son enfant et se languit pareillement d'eux. Le dispositif scénique, alors, matérialise la séparation des couples et les douleurs différentes, mais communes, touchant hommes et femmes, soldats et civils. Encore une fois, l'absence d'identité des personnages, associée à l'allégorie dominante de la pièce, souligne la souffrance collective, qui transcende les individus. Les femmes de ces pièces incarnent une réalité sociale, affrontant les privations et les travaux laissés vacants par les hommes partis au front. Dans l'après-guerre, on érige le dolorisme des mères et épouses comme vertu cardinale de la nation [START_REF] Capdevila Luc | Hommes et femmes dans la France en guerre[END_REF] , mais ces deuils, ces souffrances doivent être tournés vers les morts au champ d'honneur, non vers les civils ayant enduré autrement le conflit, qui doivent s'effacer derrière le sacrifice des soldats [START_REF] Beaupré | Le Traumatisme de la Grande Guerre[END_REF] .

Alors qu'un Dorgelès s'exclame : « Ah ! non les civils, vos gueules ! 30 », Fauré-Frémiet, lui-même ancien combattant, ne néglige pourtant pas les femmes et les enfants comme victimes de guerre à part entière. Il fait s'interpénétrer, comme le dira plus tard Paul Ricoeur, mémoire individuelle et mémoire collective [START_REF] Paul | l'oubli[END_REF] . Cependant, les scènes de permissions durant lesquelles les soldats retournent au foyer soulignent l'irrémédiable incompréhension établie : « Je suis d'ici… » dit un soldat à un autre dans la Grand'Geste du monde, « Je veux retrouver ceux qui vivent et pensent comme moi [START_REF]L'argot du poilu invente le mot « ciblot » pour désigner le civil, radicalement séparé du « pays poilu[END_REF] ». Le lien familial est faible, comparé au lien du sang, qui unit les combattants. Il met en question la mémoire, que seuls partagent réellement ceux qui ont connu les réalités du conflit et la façon de les représenter pour les civils et pour les générations suivantes.

Mais c'est une autre souffrance qui concentre nombre des intrigues : celle de l'adultère. Si Elle, dans l'Exilé, repousse les avances de son ancien amoureux, Lui, pour rester fidèle à son mari prisonnier en Allemagne, Marguerite, dans L'Autre Blessure, trompe Adrien, poilu, avec Pierre, un exempté. Adrien, de retour, est rongé par la rancoeur, envers la guerre, envers Marguerite qui l'a trahi, envers Pierre, un embusqué, figure extrêmement présente dans la littérature d'après-guerre [START_REF] Charles | La chasse aux embusqués. Le refus de la guerre[END_REF] . Dans la Grand'Geste du monde, « le désir vient tenter les femmes restées seules au foyer 34 » et un poilu, revenu en permission, « ne trouve plus sa femme qui a décampé avec l'enfant [START_REF] Strowski Fortunat | Les spectacles. Théâtre de Grenelle[END_REF] ». Dans une scène toujours allégorique, une vieille mendiante représente la tentation de l'infidélité, les tourments de la chair, auprès d'une paysanne, d'une infirmière, d'une ouvrière, avant que n'arrive « L'Eros », incarnation du désir mais aussi de la mort. La publication contemporaine des thèses freudiennes sur les pulsions de vie et de mort [START_REF] Freud | Au-delà du principe de plaisir, publié en France en 1920. Fauré-Frémiet, outre son oeuvre dramaturgique, compose des essais philosophiques comme « L'effort réalisateur de la conscience[END_REF] a vraisemblablement nourri l'écriture de Fauré-Frémiet.

Madeleine, dans Sic vos non vobis, a trompé Pierre pendant qu'il était au front. Lui, qui n'est pas revenu mutilé de la guerre, contrairement à ses compagnons Jean, Candide et Etienne, est amputé tout de même de sa joie de vivre et de sa tranquillité d'âme, à cause de cet adultère qui le mène à tuer son rival. Les thèses de médecine d'après-guerre, les études sur les traumatismes divers de ceux qui sont revenus, montrent l'obsession des hommes, au front, quant à la fidélité de leurs compagnes. Les chiffres des demandes de divorce, pendant la guerre et juste après, augmentent fortement, enregistrant la coupure créée par le conflit dans les couples 37 . Le Petit Journal souligne le lien entre réalité et fiction en juxtaposant un compte-rendu de la pièce et un fait divers : au moment où Sic vos non vobis se joue, « un tuberculeux de la guerre a grièvement blessé d'une balle de revolver sa femme, qu'il soupçonnait de lui être infidèle 38 ».

Le scandale du Diable au corps de Radiguet (1923), qui déjà s'attachait aux relations illicites de l'arrière, corrobore cette hantise du soldat et le souci collectif d'occulter ce type de comportement. Le retour au foyer et à la paix ne s'accompagne pas d'une sérénité ou d'une joie ici, à rebours du discours majoritaire de l'époque. Il s'apparente plutôt une mort symbolique, celle du corps mutilé au combat, celle du coeur blessé. Deux possibilités s'offrent alors aux personnageset donc, métaphoriquement, à la société : se laisser aller au désespoir, ou bien devenir un individu neuf et apaisé.

Renaître de la guerre

Robert Eudeline, dans la Haute Route, a fait la guerre, mais en est revenu doté d'une frénésie sexuelle à la hauteur de l'angoisse de mort ressentie au front ; il n'hésite pas à séduire « la femme d'un ancien compagnon d'armes, devenu aveugle [START_REF] Paul | Courrier des théâtres[END_REF] » qui finit par se pendre de chagrin. Eudeline a ainsi profané la confrérie sacrée des combattants : « A la guerre, deux fois, la mort lui est apparue. C'est par miracle qu'il est sauf (…). Tous les actes lui (…) paraissent permis, absous. Sa conscience est atrophiée, éteinte. Il n'est plus qu'un animal inquiet de profiter de son temps d'existence. » [START_REF] Jane | Théâtre de la Grimace[END_REF] La brutalisation du conflit, déjà évoquée, génère aussi une animalisation de l'homme, dépossédé des valeurs morales habituelles par la pratique généralisée de l'homicide, traumatisé par les visions de la mort au champ de bataille et les angoisses de sa propre mort. On retrouve ici encore l'influence de la « pulsion de mort » freudienne. De même, les soldats de la Grand'Geste du monde, pendant les périodes de répit, se succèdent-ils chez une prostituée, pour « se saouler de chair humaine avant de mourir », « posséder ! Vivre ! 41 ». Ces personnages sont tous victimes des conséquences de la guerre, incapables d'aimer « comme avant », soit que la guerre a réveillé une frénésie de vivre et de jouir, comme chez Robert Eudeline, soit qu'elle a détruit leur aptitude au bonheur amoureux, comme dans L'Exilé, où Elle et Lui ne peuvent recommencer à s'aimer, car la fidélité aux événements prime leur bonheur individuel. Candide, de Sic vos non vobis, dont les poumons sont détruits par les gaz, accélère sa marche vers la mort en buvant et se consume aussi de ne pas revoir son Afrique natale, à laquelle il a été arraché pour combattre au nom d'une nation qui n'est pas la sienne : « Le mal galope en moi comme un cheval. Alors je veux galoper plus vite que lui. Je vais boire, pour galoper dans les nuages [START_REF]Sic vos non vobis[END_REF] ».

On sait que l'alcool, généreusement distribué au front pour que le poilu supporte les conditions de vie les plus abominables, mais aussi pour qu'il anesthésie sa peur de combattre ou sa douleur après une blessure, a entraîné une hausse très forte de l'alcoolisme dans la population après 1918. Dans la même pièce, Jean raconte à Mathilde la solidarité du front avec son « frère d'armes », Etienne, qui l'a parfois secouru « en partageant (…) un quart de vin [START_REF]Sic vos non vobis[END_REF] ». Dans la Grand'Geste du monde, les soldats partagent aussi leur quart, pour supporter leur vie et leurs peurs. Comme le dit Maurice Genevoix, grand témoin des faits de guerre, « Ce que nous avons fait, c'est plus qu'on ne pouvait demander à des hommes… [START_REF] Genevoix | Ecrivain combattant, Genevoix livre ses souvenirs de guerre dans plusieurs récits-témoignages[END_REF] ».

Toutefois, une autre voie, une plus « haute route », pour citer l'un des titres de Fauré-Frémiet, est possible pour l'humanité ; c'est ce que démontre l'auteur, notamment dans les scènes de Sic vos non vobis entre Jean et Etienne, symboles des deux façons de gérer le trauma. Meurtris tous deux dans leur chair, leurs réactions sont opposées : Etienne déplore sa « vie perdue, gâchée », son corps «estropié, mutilé » mais vivant ; son coeur est, dit-il « plein de haine (…). Contre tout l'univers, injuste et cruel, contre tous ceux qui ont édifié ou conservé leur bonheur derrière les ruines vivantes que nous sommes. Ce n'est pas pour nous, va, que nous avons travaillé ! 45 ».

Il éclaire par cette dernière réplique le titre latin de la pièce : « ce n'est pas pour nous que nous avons travaillé [START_REF]Vers de Virgile, suite à l'usurpation de Bathylle, qui s'est attribué la paternité de ses vers[END_REF] » ; les morts innombrables, les mutilations, les désespérances, les souffrances multiples se sont faites au nom de quelques-uns. La mise en accusation de la guerre, en général, et de ses chefs, en particulier, est tout à fait évidente et révèle le pacifisme dont Fauré-Frémiet se fait le porte-parole. Jean, au contraire, sans nier l'absurdité de la guerre, qu'il condamne tout aussi fermement qu'Etienne, a choisi de faire de ce traumatisme une force et une ligne de conduite pour l'avenir ; il symbolise, pour utiliser un anachronisme, la résilience, mais aussi l'abnégation. C'est ainsi qu'il renonce à l'amour partagé avec Mathilde, la jeune veuve de guerre, pour ne pas abandonner son « frère de misère », afin de « tenter de vivre tous trois au-dessus [des] désirs, [des] passions, au-dessus [des] corps mutilés 47 ».

Le spectateur peut entendre dans cette réplique un écho du célèbre Au-dessus de la mêlée, de Romain Rolland, qui causa un scandale extrême [START_REF] Rolland Romain | Au-dessus de la mêlée[END_REF] . Toute la pièce va d'ailleurs dans le sens de cette fraternité réclamée par Rolland, puisque Jean comme Etienne sont conscients de la communauté de destins des soldats allemands et français : « Vainqueurs et vaincus, tous sont dans le même sac de misère ou dans le même néant » résume Etienne ; Jean, lui, veut demeurer « Sans révolte et sans haine [START_REF] Jean | ) 50 Didascalie dans la Grand'Geste du monde[END_REF] », surtout envers les Allemands qui ont connu un sort identique au sien.

Dans la Grand'Geste du monde, nous assistons parallèlement aux itinéraires d'un soldat français et d'un soldat allemand, dans des scènes simultanées qui soulignent leur extrême similitude : même départ au milieu des pleurs familiaux, mêmes souffrances au combat, même fin tragique lorsqu'on les retrouve au dénouement. Ils ne se haïssent pas, mais se sont entretués, par devoir patriotique, alors que, avant guerre, ils s'apprêtaient à épouser chacun la soeur de l'autre. La scène simultanée souligne l'aberration du conflit, qui rend ennemis les frères d'hier et annihile toute faculté de juger, rend les actes automatiques, dénués de volonté propre. Dans les scènes suivantes, les didascalies précisent que le soldat porte un « uniforme de combattant qui n'est d'aucune armée 50 ». Alors que nombre d'oeuvres françaises accusent l'Allemagne et l'attitude des soldats allemands, Fauré-Frémiet symbolise durant toute la pièce cette profonde fraternité humaine qui lie les soldats, tous victimes des Archanges, qui, au prologue, décident d'envoyer la Guerre sur terre, mais aussi des gradés, des généraux et des profiteurs capitalistes, qui construisent leur réussite sur la mort. En d'autres termes, sa critique est politique et éthique, non ethnique.

Par conséquent, certains s'insurgent contre ce qu'ils considèrent comme une trahison : « On risque d'oublier qu'il y eut un peuple agresseur et un peuple assailli et que la psychologie ne l'un ne pouvait être celle de l'autre 51 » déplore Le Cardonnel. L'anonymat efface la nationalité du soldat dans les tranchées, au combat, afin de concrétiser cette communauté de sort, mais un article de la Rampe signale qu'il n'y a « rien de français là-dedans 52 », reproche dans lequel perce la difficulté nationale à envisager un avenir dans lequel l'Allemand ne serait plus « le Boche », le « Fridolin », le barbare. Fauré-Frémiet représente la France au congrès franco-allemand qui se tient à Rethel en 1931 pour envisager la perspective d'une union européenne [START_REF]Le congrès franco-allemand de Rethel[END_REF] , dans la logique des valeurs défendues dans ses pièces. Les coupables, selon lui, ne sont pas à chercher outre-Rhin, mais bien dans la condition humaine, qui doit être remise en question.

L'Humanité décèle dans la « rhétorique de la guerre » présente dans la Grand'Geste du monde « toute la blanche fleur du pacifisme [START_REF] Parijanine | Ce qui se joue[END_REF] » et Fauré-Frémiet symbolise bien, en effet, ce refus des conflits qui se diffuse largement dans la société à partir des années 20, notamment propagé par les anciens combattants, dont bien sûr Barbusse [START_REF] Barbusse | pacifiste avant la guerre et collaborateur de la revue Paix, dirige le mouvement Clarté à partir de 1919, pour créer une association d'intellectuels contre la guerre. Voir RACINE Nicole, « Une revue d'intellectuels communistes dans les années vingt : 'Clarté' (1921-1928[END_REF] . La littérature connaît une évolution similaire, passant des récits de combats à une dénonciation des ravages matériels et humains causés par la guerre et à un appel à la paix. L'horreur, les souffrances n'ont pas engendré chez Fauré-Frémiet une misanthropie, bien au contraire : ses personnages, vus dans leur intimité, déshumanisés, sont ici réparés dans leur individualité et dans leur humanité.

Conclusion

Le récit de la guerre n'existe pas à proprement parler dans l'oeuvre de Fauré-Frémiet, qui s'attache bien davantage aux conséquences qu'elle eut, qu'elle avait encore sur les hommes, les femmes, les enfants. Il ne laisse de côté ni la société civile, souvent négligée eu égard aux intenses souffrances des combattants, ni les affres psychologiques dans lesquels sont plongés ceux qui sont revenus, mutilés dans leur corps ou dans leur âme. Ses souvenirs ne sont pas livrés, il s'attache, certes avec un certain réalisme, à rendre compte, mais ne raconte pas « sa » guerre. Un écrivain ancien combattant évoque, au moment où se joue la Grand'Geste du monde, « le monde de l'après-guerre (…) à reconstruire », en particulier par « ceux qui ont souffert », grâce à « des valeurs intellectuelles et morales [START_REF] Lamandé André | Après Versailles. Les écrivains anciens combattants[END_REF] ». Fauré-Frémiet, dès ses premières créations, ambitionne bien de régénérer l'humanité, pas comme les Archanges, en envoyant la guerre sur terre [START_REF]On peut rapprocher cet épisode des déclarations de Marinetti dans le Manifeste futuriste de 1919 et des convictions de Maurice Barrès sur la guerre comme seul moyen d'affermir la nation française[END_REF] , mais en indiquant la voie du pacifisme, de la réconciliation franco-allemande, du dépassement des appétits physiques. Un critique a dit de lui qu'il peignait « l'homme tel qu'il doit être [START_REF] Salini Formose | Un bel écrivain d'art dramatique : Philippe Fauré-Frémiet[END_REF] », ce qui semble parfaitement symboliser l'écriture de Fauré-Frémiet, engagée vers l'humain et son progrès, dans un contexte qui ne connaît pas encore un total désenchantement vis-à-vis de cette notion positiviste.

Finalement, c'est moins son propre traumatisme de la guerre qu'il exorcise par le récit, que le traumatisme collectif dont il tente une réappropriation pour un avenir meilleur. Comme il le confiait à Paris-Soir dans une interview, « la mission de l'artiste est de révéler l'essentiel, d'incarner la vie intérieure, donc de la porter vers la conscience, d'illuminer ce qui est obscur 59 ». Les pièces de Fauré-Frémiet n'ont été jouées que sur des scènes d'avant-garde, hormis Le Souffle du désordre, entré au répertoire de l'Odéon 60 , oeuvre qui n'évoque pas la guerre : est-ce le signe de la modernité de son écriture ou de l'inadéquation entre sa volonté de porter au public la mémoire du trauma collectif et l'occultation délibéré que promeut l'entredeux-guerres ? Nathalie COUTELET (Université Paris 8 -EA 1573) 59 FAURÉ-FRÉMIET Ph., « Du théâtre conscient », Paris-Soir, n° 803, 17 décembre 1925. 60 Le Souffle du désordre, pièce donnée par la troupe de la Grimace, jouée au Théâtre des Mathurins en juin 1922, entre au répertoire de l'Odéon en janvier 1928.

Emmanuel Frémiet (1824-1910) : neveu de Rude, membre de l'Académie des Beaux-Arts, il effectue des commandes officielles de sculptures animalières en particulier.

« La génération du feu. Le traité de Versailles jugé par les combattants », Le Matin, n° 14088, 15 octobre 1922.

Association fondée en 1919, réunissant des personnalités littéraires ayant combattu, afin de maintenir la fraternité du front, mais aussi pour signifier leur différence vis-à-vis des créations d'auteurs n'ayant pas connu les combats.

Aide et Protection est une compagnie théâtrale, subventionnée par la Ville de Paris, dirigée par Gabriel Imbert et Pierre Aldebert (1918). Durant les premières années, elle monte uniquement des oeuvres d'anciens combattants.

BEAUPRÉ Nicolas, Ecrire en guerre, écrire la guerre. France, Allemagne, 1914-1920, Paris, CNRS Editions, coll. « CNRS Histoire », 2006.

GINISTY Paul, « Courrier des théâtres », Le Petit Parisien, n° 17608, 15 mai 1925.

FIX Florence, L'Histoire au théâtre, Rennes, PUR, coll. « Interférences », 2010, p. 14.

VAISSE Maurice, Le Pacifisme en Europe des années 20 aux années 50, Bruxelles, Bruylant, 1993.

BEAUPRÉ N., op. cit., p. 33.

COQUET James de, « Courrier des théâtres », Le Figaro, n° 305, 1 er novembre 1927. D'abord donnée en lecture par le groupe du Canard Sauvage, en mai, la pièce est représentée par les Comédiens de la Croix-Nivert au Théâtre de Grenelle.

ANTOINE, L'Information, 31 novembre 1927, BnF, RT 3953.

Didascalies, scène V, 2 e partie, La Grand'Geste du monde, Paris, PUF, 1927, p. 52.

MOSSE Georges, De la Grande Guerre au totalitarisme, la brutalisation des sociétés européennes, Paris, Hachette,2000 [1990].

Roland Dorgelès dans les Croix de bois (1919) et Henri Barbusse dans le Feu (1915) consacrent la narration aux combats et à l'expérience du front pour les soldats.

Pièce donnée sous le patronage d'Aide et Protection, au Théâtre Antoine alors dirigé par Firmin Gémier. Sur Gémier, voir COUTELET Nathalie, Firmin Gémier, le démocrate du théâtre, Montpellier, L'Entretemps, coll. « Champ théâtral », 2009.

« Chronique théâtrale », Le Temps, n° 21482, 25 mai 1920.

DUBECH Lucien, « La Grimace : La Haute Route, de M. Fauré-Frémiet », 31 mai 1925, BnF, Arts du spectacle, RT 4082. La pièce est donnée par la compagnie de la Grimace, créée par Fernand Bastide.

SOREL Jean-Albert, « Chronique dramatique », L'Ermitage, juin-juillet

1927, BnF, Arts du spectacle, RT 4082.

DESCAVES Lucien, « Spectacles. Le théâtre », L'Intransigeant, n° 15941, 28 mars 1924. La pièce est montée par la compagnie du Canard sauvage, qui exploite le Théâtre Albert I er à partir de décembre 1923.

FAURÉ-FRÉMIET Philippe, Sic vos non vobis, Editions Rhéa, 1926, p. 66 (Acte II, scène 2). Le rôle de Candide est tenu par Habib Benglia ; voir COUTELET Nathalie, Histoire des artistes noirs du spectacle français. Une démocratisation multiculturaliste, Paris, L'Harmattan, coll. « Univers théâtral », 2012.

FAURÉ-FRÉMIET Ph., L'Exilé, pièce en un acte, Paris, Editions Rhéa, 1926, p. 21. Pièce jouée par la troupe des Compagnons du Griffon, au Théâtre de la Potinière, en décembre 1922.


Flavien Champagne

Amélie Vialet

Guillaume Fleury

Study of decidual teeth discovered in the 19th century in Saint-Acheul (Somme, France)

teaching and research institutions in France or abroad, or from public or private research centers.

Study of decidual teeth discovered in the 19 th

century in Saint-Acheul (Somme, France)

Flavien CHAMPAGNE 1 , Amélie VIALET 2 , Guillaume FLEURY 3

1 Université d'Angers, France, 2 UMR7194 HNHP, MNHN-CNRS-UPVD, Département Homme et Environnement, Musée de l'Homme, Paris, France, [START_REF] Bailey | What does it mean to be dentally "mordern[END_REF] Muséum de Toulouse, France.

Five isolated human decidual teeth (Fig. 1) have been identified in the collections of the Museum of Toulouse. An associated label mentioned the site of Saint-Acheul, the name of Lartet and the date of 1869. Moreover, the teeth were stored with a biface, an equid tooth, several pebbles and two fossil sea urchins used as hammerstones. No more information is known about the context of their discovery. The series includes an upper right central incisor (di 1 ), an upper right second molar (dm 2 ), a lower right central incisor (di 1 ), a lower right first molar (dm 1 ) and a lower right second molar (dm 2 ). The objective of this study is to determine the biological characteristics of these teeth, their taxonomic attribution and the taphonomic processes that would have affected them.

The study of the Saint-Acheul teeth includes observations of their metric and non-metric anatomical traits compared to bibliographic data of 93 fossil individuals from the Middle (n=62) and Late Pleistocene (n=31), representing a total of 160 teeth including 29 di

Introduction

Materials & methods

Results

due to the excessive degradation of its root, it was not possible to determine the developmental stage of di 1 . The enamel alteration observed could correspond to a predator partial digestion especially explained by differential erosion of dentine and enamel at the cervix 5 (Fig. 3).

Figure 1 .

 1 Figure 1. Saint-Acheul decidual teeth. a. Upper right central incisor; b. Upper right second molar; c. Lower right central incisor; d. Lower right first molar; e. Lower right second molar. For the incisors: 1. Buccal face; 2. Mesial face; 3. Lingual face. For the molars: 1. Buccal face; 2. Occlusal face; 3. Apical face. D = distal side; M = mesial side; L = lingual side; B = buccal side. Scale

Figure 3 .

 3 Figure 3. Examples of digestion marks on Saint-Acheul teeth. a. Upper right second molar; b. Lower right first molar. White arrow: apical enamel limit, black arrow: anatomical cervix. Scale bars: 1 mm.

Figure 2 .

 2 Figure 2. Box plots of buccolingual diameters. a. Upper central incisor; b. Upper second molar; c. Lower first molar; d. Lower second molar. ST-ACH = Saint-Acheul; NEAN = Neanderthals; HSPS = H. sapiens; HPM = Middle Pleistocene hominins; ANTE-NEAN = ante-Neanderthals; HERG = H. ergaster; HANT = H. antecessor; AURI = undetermined Aurignacians.

  1 , 36 dm 2 , 16 di 1 , 36 dm 1 and 43 dm 2 . The Liversidge and Molleson table was used to determine the age at death 1 .

	Comparative	morphometric
	analysis reveals many similarities
	between the Saint-Acheul teeth and
	those belonging to Neanderthals
	(rhomboidal crown shape of dm 2 with