Marie Touchon

Samuel Nicolay

Benjamin Audit

Edward-Benedict Brodie Of Brodie

Yves D'aubenton-Carafa

Alain Arneodo

Claude Thermes

Minor category: EVOLUTION Replication-associated strand asymmetries in mammalian genomes: towards detection of replication origins

In the course of evolution, mutations do not affect both strands of genomic DNA equally. This mainly results from asymmetric DNA mutation and repair processes associated with replication and transcription. In prokaryotes, prevalence of G over C and T over A is frequently observed in the leading strand. The sign of the resulting TA and GC skews changes abruptly when crossing replication origin and termination sites, producing characteristic step-like transitions. In mammals, transcriptioncoupled skews have been detected, but so far, no bias has been associated with replication. Here, analysis of intergenic and transcribed regions flanking experimentally-identified human replication origins and the corresponding mouse and dog syntenic regions demonstrates the existence of compositional strand asymmetries associated with replication. Multi-scale analysis of human genome skew profiles reveals numerous transitions that allow us to identify a set of one thousand putative replication initiation zones. Around these putative origins, the skew profile displays a characteristic jagged pattern also observed in mouse and dog genomes. We therefore propose that in mammalian cells, replication termination sites are randomly distributed between adjacent origins. Altogether, these analyses constitute a step toward genome-wide studies of replication mechanisms.

INTRODUCTION

Comprehensive knowledge of genome evolution relies on understanding mutational processes that shape DNA sequences. Nucleotide substitutions do not occur at similar rates and in particular, owing to strand asymmetries of the DNA mutation and repair processes, they can affect each of the two DNA strands differently. Asymmetries of substitution rates coupled to transcription have been observed in prokaryotes (1)(2)(3) and in eukaryotes (4)(5)(6). Strand asymmetries (i.e. G ≠ C and T ≠ A) associated with the polarity of replication have been found in bacterial, mitochondrial and viral genomes where they have been used to detect replication origins (7)[START_REF] Mrazek | Proc. Natl. Acad. Sci[END_REF][START_REF] Tillier | [END_REF]. In most cases, the leading replicating strand presents an excess of G over C and of T over A. Along one DNA strand, the sign of this bias changes abruptly at the replication origin and at the terminus. In eukaryotes, the situation is unclear. Several studies failed to show compositional biases related to replication and analyses of nucleotide substitutions in the region of the ß-globin replication origin did not support the existence of mutational bias between the leading and the lagging strands [START_REF] Mrazek | Proc. Natl. Acad. Sci[END_REF]10,11). In contrast, strand asymmetries associated with replication were observed in the subtelomeric regions of Saccharomyces cerevisiae chromosomes, supporting the existence of replication-coupled asymmetric mutational pressure in this organism (12). We present here analyses of strand asymmetries flanking experimentally-determined human replication origins, as well as the corresponding mouse and dog syntenic regions. Our results demonstrate the existence of replication-coupled strand asymmetries in mammalian genomes. Multiscale analysis of skew profiles of the human genome using the wavelet transform methodology, reveals the existence of numerous putative replication origins associated with randomly distributed termination sites.

Data and Methods

Human replication origins. Nine replication origins were examined, namely those situated near the genes MCM4 (13), HSPA4 (14), TOP1 (15), MYC (16), SCA-7 (17), AR (17), DNMT1 (18), LaminB2 [START_REF] Giacca | Proc. Natl. Acad. Sci[END_REF] and ß-globin [START_REF] Kitsberg | [END_REF].

Sequences. Sequence and annotation data were retrieved from the Genome Browser of the University of California Santa Cruz (UCSC) for the human (May 2004), mouse (May 2004) and dog (July 2004) genomes. To delineate the most reliable intergenic regions, transcribed regions were retrieved from "all_mrna", one of the largest sets of annotated transcripts. To obtain intronic sequences, we used the KnownGene annotation (containing only protein-coding transcripts); when several transcripts presented common exonic regions, only common intronic sequences were retained. For the dog genome, only preliminary gene annotations were available, precluding the analysis of intergenic and intronic sequences. To avoid biases intrinsic to repeated elements, all sequences were masked with RepeatMasker, leading to 40-50% sequence reduction.

Strand asymmetries.

The TA and GC skews were calculated as S TA = (T -A) /(T + A), S GC = (G -C) /(G + C) and the total skew as S = S TA + S GC , in non-overlapping 1 kbp windows (all values are given in percent). The cumulated skew profiles Σ TA and Σ GC were obtained by cumulative addition of the values of the skews along the sequences. To calculate the skews in transcribed regions, only central regions of introns were considered (after removal of 530 nt from each extremity) in order to avoid the skews associated with splicing signals (6). To calculate the skews in intergenic regions, only windows that did not contain any transcribed region were retained. To eliminate the skews associated with promoter signals and with transcription downstream of polyA sites, transcribed sequences were extended by 0.5 kbp and 2 kbp at 5' and 3' extremities, respectively (6).

Sequence alignments.

Mouse and dog regions syntenic to the six human regions shown in Fig. 1 were retrieved from UCSC (Human Synteny). Mouse intergenic sequences were individually aligned using PipMaker (21) leading to a total of 150 conserved segments larger than 100 bp (> 70% identity) corresponding to a total of 26 kbp (5.3% of intergenic sequences).

Wavelet-based analysis of the human genome. The wavelet transform (WT) methodology is a multiscale discontinuities tracking technique [START_REF] Arneodo | The Science of Disaster[END_REF][START_REF] Nicolay | [END_REF] (for details, see Supplementary material). The main steps involved in detection of jumps were the following. We selected the extrema of the first derivative ′ S of the skew profile S smoothened at large scale (i.e. computed in large windows). The scale 200 kbp was chosen as being just large enough to reduce the contribution of discontinuities associated with transcription (i.e. larger than most human genes (24)), yet as small as possible so as to capture most of the contributions associated with replication. In order to delineate the position corresponding to the jumps in the skew S at smaller scale, we then progressively decreased the size of the analyzing window and followed the positions of the extrema of ′ S across the whole range of scales down to the shortest scale analyzed (the precision was limited by the noisy background fluctuations in the skew profile). As expected, the set of extrema detected by this methodology corresponded to similar numbers of upward and downward jumps. The putative replication origins were then selected among the set of upward jumps on the basis of their ΔS amplitude (see text).

RESULTS AND DISCUSSION

Strand asymmetries associated with replication. We examined the nucleotide strand asymmetries around 9 replication origins experimentally-determined in the human genome (Data and Methods). For most of them, the S skew measured in the regions situated 5' to the origins on the Watson strand (lagging strand) presented negative values that shifted abruptly (over few kbp) to positive values in regions situated 3' to the origins (leading strand), displaying sharp upward transitions with large ΔS amplitudes as observed in bacterial genomes (7-9) (Fig. 1a). This was particularly clear with the cumulated TA and GC skews that presented decreasing (increasing) profiles in regions situated 5' (3') to the origins, displaying characteristic V-shapes pointing to the initiation zones. These profiles could, at least in part, result from transcription, as shown in previous work (6). To measure compositional asymmetries that would result only from replication, we calculated the skews in intergenic regions on both sides of the origins. The mean intergenic skews shifted from negative to positive values when crossing the origins (Fig. 2). This result strongly suggested the existence of mutational pressure associated with replication, leading to the mean compositional biases S TA = 4.0 ± 0.4% and S GC = 3.0 ± 0.5% (note that the value of the skew could vary from one origin to another, possibly reflecting different initiation efficiencies) (Table 1). In transcribed regions, the S bias presented large values when transcription was co-oriented with replication fork progression ((+) genes on the right, (-) genes on the left), and close to zero values in the opposite situation (Fig. 2). In these regions, the biases associated with transcription and replication added to each other when transcription was co-oriented with replication fork progression, giving the skew S Lead ; they subtracted from each other in the opposite situation, giving the skew S lag (Table 1). We could estimate the mean skews associated with transcription by subtracting intergenic skews from S Lead values, giving S TA = 3.6 ± 0.7% and S GC = 3.8 ± 0.9%. These estimations were consistent with those obtained with a large set of human introns S TA = 4.49 ± 0.01% and S GC = 3.29 ± 0.01% in ref. (6), further supporting the existence of replication- coupled strand asymmetries. 1. Strand asymmetries associated with human replication origins. The skews were calculated in the regions flanking the six human replication origins (Fig. 1a) and in the corresponding syntenic regions of the mouse genome. Intergenic sequences were always considered in the direction of replication fork progression (leading strand); they were considered in totality (all) or after elimination of conserved regions (ncr.) between human (H.s.) and mouse (M.m.) (see Data and Methods). To calculate the mean skew in introns, the sequences were considered on the non-transcribed strand:

S

S Lead , the orientation of transcription was the same as the replication fork progression; S lag , opposite situation. The mean values of the skews S TA , S GC and S are given in % (± SEM); l, total sequence length in kbp. represents the distance (kbp) of a sequence window to the corresponding origin; ordinate represents the values of S given in percent; red, (+) genes (coding strand identical to the Watson strand); blue, (-) genes (coding strand opposite to the Watson strand); black, intergenic regions; in (c) genes are not represented.

Could the biases observed in intergenic regions result from the presence of as yet undetected genes? Two reasons argued against this possibility. First, we retained as transcribed regions one of the largest sets of transcripts available, resulting in a stringent definition of intergenic regions. Second, several studies have demonstrated the existence of hitherto unknown transcripts in regions where no protein coding genes had been previously identified (25)[START_REF] Chen | Proc. Natl. Acad. Sci[END_REF][START_REF] Rinn | [END_REF](28). Taking advantage of the set of non-proteincoding RNAs identified in the "H-Inv" database (29), we checked that none of them was present in the intergenic regions studied here. Another possibility was that the skews observed in intergenic regions result from conserved DNA segments. Indeed, comparative analyses have shown the presence of nongenic sequences conserved in human and mouse (30). These could present biased sequences, possibly contributing to the observed intergenic skews. We examined the mouse genome regions syntenic to the six human replication zones (Fig. 1b). Alignment of corresponding intergenic regions revealed the presence of homologous segments, but these accounted for only 5.3 % of all intergenic sequences. Removal of these segments did not change significantly the skew in intergenic regions, therefore eliminating the possibility that intergenic skews are due to conserved sequence elements (Table 1). Fig. 2. Skew S in regions situated on both sides of human replication origins. The mean values of S were calculated in intergenic regions and in intronic regions situated 5' (left) and 3' (right) of the six origins analyzed in Fig. 1a; colors are as in Fig. 1; mean values are in percent ± SEM.

Conservation of replication-coupled strand asymmetries in mammalian genomes. We analyzed the skew profiles in DNA regions of mammalian genomes syntenic to the six human origins (Fig. 1). The human, mouse and dog profiles were strikingly similar to each other, suggesting that in mouse and dog, these regions also corresponded to replication initiation zones (indeed, they were very similar in primate genomes). Examination of mouse intergenic regions showed, as for human, significant skew S values with opposite signs on each side of these putative origins, suggesting the existence of a compositional bias associated with replication S = 5.8 ± 0.5% (Table 1). Human and mouse intergenic sequences situated at these homologous loci presented significant skews, even though they presented almost no conserved sequence elements. This presence of strand asymmetry in regions that strongly diverged from each other during evolution further supported the existence of compositional bias associated with replication in both organisms: in the absence of such process, intergenic sequences would have lost a significant fraction of their strand asymmetry.

Altogether, these results establish, in mammals, the existence of strand asymmetries associated with replication in germ-line cells. They determine that most replication origins experimentally-detected in somatic cells coincide with sharp upward transitions of the skew profiles. The results also imply that for the majority of experimentally-determined origins, the positions of initiation zones are conserved in mammalian genomes (a recent work confirmed the presence of a replication origin in the mouse MYC locus (31)). Among nine human origins examined, three do not present typical V-type cumulated profiles. For the first one (DNMT1), the central part of the V-profile is replaced by a large horizontal plateau (several tens of kbp) possibly reflecting the presence of several origins dispersed over the whole plateau. Dispersed origins have been observed for example in the hamster DHFR initiation zone (32). By contrast, the skew profiles of the LaminB2 and ß-globin origins present no upward transition suggesting that they might be inactive in germ-line cells, or less active than neighboring origins (data not shown).

Detection of putative replication origins. Human experimentally-determined replication origins

coincided with large amplitude upward transitions of skew profiles. The corresponding ΔS ranged between 14% and 38% owing to possible different replication initiation efficiencies and/or different contributions of transcriptional biases (Fig. 1a). Are such discontinuities frequent in human sequences, and can they be considered as diagnostic of replication initiation zones? In particular, can they be distinguished from the transitions associated with transcription only? Indeed, strand asymmetries associated with transcription can generate sharp transitions in the skew profile at both gene extremities. These jumps are of same amplitude and of opposite signs, e.g. upward (downward) jumps at 5' (3') extremities of (+) genes (6). Upward jumps resulting from transcription only, might thus be confused with upward jumps associated with replication origins.

To address these questions, systematic detection of discontinuities in the S profile was performed with the wavelet transform methodology, leading to a set of 2415 upward jumps and, as expected, to a similar number of downward jumps (see Data and Methods). The distributions of the ΔS amplitude of these jumps were then examined, showing strong differences between upward and downward jumps. For large ΔS values, the number of upward jumps exceeded by far the number of downward jumps (Fig. 3). This excess likely resulted from the fact that, contrasting with prokaryotes where downward jumps result from precisely positioned replication termination, in eukaryotes, termination appears not to occur at specific positions but to be randomly distributed (this point will be detailed in the last section) (33,34). Accordingly, the small number of downward jumps with large ΔS resulted from transcription, not replication. These jumps were due to highly biased genes that also generated a small number of large amplitude upward jumps, giving rise to false positive candidate replication origins. The number of large downward jumps was thus taken as an estimation of the number of false positives. In a first step, we retained as acceptable a proportion of 33% of false positives. This value resulted from the selection of upward and downward jumps presenting an amplitude ΔS ≥ 12.5%, corresponding to a ratio of downward jumps over upward jumps r = 0.33. The values of this ratio r were highly variable along the chromosomes (Fig. 3). In G+C-poor regions (G+C < 37%) we observed the smallest r values (r = 0.15). In regions with 37% ≤ G+C ≤ 42%, we obtained r = 0.24, contrasting with r = 0.53 in regions with G+C > 42%. In these latter regions (accounting for about 40% of the genome) with high gene density and small gene length (24), the skew profiles oscillated rapidly with large upward and downward amplitudes (Fig. 5d) resulting in a too large number of false positives (53%). In a final step, we retained as putative origins upward jumps (with ΔS ≥ 12.5%) detected in regions with G+C ≤ 42%. This led to a set of 1012 candidates among which we could estimate the proportion of true replication origins to 79% (r = 0.21, Fig. 3a).

The mean amplitude of the jumps associated with the 1012 putative origins was 18%, consistent with the range of values observed for the six origins in Fig. 1. Note that these origins were all found in the detection process. In close vicinity of the 1012 putative origins (± 20kbp) most DNA sequences (55 % of the analyzing windows) are transcribed in the same direction as the progression of the replication fork. By contrast, only 7% of sequences are transcribed in the opposite direction (38% are intergenic).

These results show that the ΔS amplitude at putative origins mostly results from superposition of biases (i) associated with replication and (ii) with transcription of the gene proximal to the origin. Whether transcription is co-oriented with replication at larger distances will require further studies.

We then determined the skews of intergenic regions on both sides of these putative origins. As shown in Fig. 4, the mean skew profile calculated in intergenic windows shift abruptly from negative to positive values when crossing the jump positions. To avoid the skews that could result from incompletely annotated gene extremities (e.g. 5' and 3' UTRs), 10 kbp sequences were removed at both ends of all annotated transcripts. The removal of these intergenic sequences did not significantly modify the skew profiles indicating that the observed values do not result from transcription. On both sides of the jump, we observed a steady decrease of the bias, with some flattening of the profile close to the transition point. Note that, due to (i) the potential presence of signals implicated in replication initiation, and (ii) the possible existence of dispersed origins (32), one might question the meaningfulness of this flattening that leads to a significant underestimate of the jump amplitude. As shown in Fig. 4, extrapolating the linear behavior observed at distance from the jump would lead to a skew of 5.3%, a value consistent with the skew measured in intergenic regions around the six origins (7.0 ± 0.5%, Table 1). Overall, the detection of upward jumps with characteristics similar to those of experimentally-determined replication origins and with no downward counterpart, further support the existence, in human chromosomes, of replication-coupled strand asymmetries, leading to the identification of numerous putative replication origins active in germ-line cells.

Fig. 3. Histograms of the ΔS amplitudes of the jumps in the S profile. Using the wavelet transform, a set of 5101 discontinuities was detected (2415 upward jumps and 2686 downward jumps, Data and Methods). The ΔS amplitude was calculated as in Fig. 1a. (a) ΔS distributions of the jumps presenting G+C < 42%, corresponding to 1647 upward jumps and 1755 downward jumps; the threshold ΔS ≥ 12.5% (vertical line) corresponded to 1012 upward jumps that were retained as putative replication origins, and to 211 downward jumps (r = 0.21). (b) ΔS distributions of the jumps presenting G+C > 42%, ΔS ≥ 12.5% corresponding to 528 upward jumps and 280 downward jumps (r = 0.53). The G+C content was measured in the 100 kbp window surrounding the jump position.

Upward jumps (black); downward jumps (dots); abscissa represents the values of the ΔS amplitudes calculated in percent.

Random replication termination in mammalian cells.

In bacterial genomes, the skew profiles present upward and downward jumps at origin and termination positions, respectively, separated by constant S values (7-9). Contrasting with this step-like shape, the S profiles of intergenic regions surrounding putative origins did not present downward transitions, but decreased progressively in the 5' to 3' direction on both sides of the upward jump (Fig. 4). This pattern was typically found along S profiles of large genome regions showing sharp upward jumps connected to each other by segments of steadily decreasing skew (Fig. 5 a-c). The succession of these segments, presenting variable lengths, displayed a jagged motif reminiscent of the shape of "factory roofs" which was observed around the experimentally-determined human origins (Fig. 5a and data not shown), as well as around a number of putative origins (Fig. 5 b,c). Some of these segments were entirely intergenic (Fig. 5 a,c), clearly illustrating the particular profile of a strand bias resulting solely from replication. In most other cases, we observed the superposition of this replication profile and of the transcription profile of (+) and (-) genes, appearing as upward and downward blocks standing out from the replication pattern (Fig. 5c).

Overall, this jagged pattern could not be explained by transcription only, but was perfectly explained by termination sites more or less homogeneously distributed between successive origins. Although some replication terminations have been found at specific sites in S. pombe (35), they occur randomly between active origins in S. cerevisiae and in Xenopus egg extracts (33,34). Our results indicate that this property can be extended to replication in human germ-line cells. According to our results, we propose a scenario of replication termination relying on the existence of numerous termination sites distributed along the sequence (Fig. 6). For each termination site (used in a small proportion of cell cycles), strand asymmetries associated with replication will generate a skew profile with a downward jump at the position of termination and upward jumps at the positions of the adjacent origins, separated by constant values (as in bacteria). Various termination positions will correspond to elementary skew profiles (Fig. 6, first column). Addition of these profiles will generate the intermediate profile (second column) and further addition of many elementary skews will generate the final profile (third column). In a simple picture, we can suppose that termination occurs with constant probability at any position on the sequence. This can result from the binding of some termination factor at any position between successive origins, leading to a homogeneous distribution of termination sites during successive cell cycles. The final skew profile is then a linear segment decreasing between successive origins (Fig. 6, third column, black line). In a more elaborate scenario, termination would take place when two replication forks collide. This would also lead to various termination sites, but the probability of termination would then be maximum at the middle of the segment separating neighboring origins, and decrease towards extremities. Considering that firing of replication origins occurs during time intervals of the S phase [START_REF] White | Proc. Natl. Acad. Sci. USA[END_REF] could result in some flattening of the skew profile at the origins, as sketched in Fig. 6 (third column, grey curve). In the present state, our results clearly support the hypothesis of random replication termination in mammalian cells, but further analyses will be necessary to determine what scenario is precisely at work.

Importantly, the "factory roof" pattern was not specific to human sequences, but it was also observed in numerous regions of the mouse and dog genomes (e.g. Fig. 5 e,f)) indicating that random replication termination is a common feature of mammalian germ-line cells. Moreover, this pattern was displayed by a set of one thousand upward transitions, each flanked on each side by DNA segments of appriximately 300 kbp (without repeats), which can be roughly estimated to correspond to 20-30% of the human genome. In these regions, characterized by low and medium G+C contents, the skew profiles revealed a portrait of germ-line replication, consisting of putative origins separated by long DNA segments of about 1-2 Mbp long. Although such segments are much larger than could be expected from the classical view of ≈ 50-300 kbp long replicons (37), they are not incompatible with estimations showing that replicon size can reach up to 1 Mbp (38,39) and that replicating units in meiotic chromosomes are much longer than those engaged in somatic cells [START_REF] Callan | Proc. R. Soc. Lond[END_REF]. Finally, it is not unlikely that in G+C-rich (gene-rich) regions, replication origins would be closer to each other than in other regions, further explaining the greater difficulty in detecting origins in these regions. replication termination is more likely to occur at lower rates close to the origins, leading to a flattening of the profile (3 rd column, grey line).

In conclusion, analyses of strand asymmetries demonstrate the existence of mutational pressure acting asymmetrically on the leading and lagging strands during successive replicative cycles of mammalian germ-line cells. Analyses of the sequences of human replication origins show that most of these origins, determined experimentally in somatic cells, are likely to be active also in germ-line cells. In addition, the results reveal that the positions of these origins are conserved in mammalian genomes. Finally, multi-scale studies of skew profiles allow us to identify a large number (1012) of putative replication initiation zones and provide a genome-wide picture of replication initiation and termination in germ-line cells.

Fig. 1 .

 1 Fig.1. TA and GC skew profiles around experimentally-determined human replication origins. (a) The skew profiles were determined in 1 kbp windows in regions surrounding (± 100 kbp without repeats) experimentally-determined human replication origins (Data and Methods). First row, TA and GC cumulated skew profiles Σ TA (thick line) and Σ GC (thin line). Second row, skew S calculated in the same regions. The ΔS amplitude associated with these origins, calculated as the difference of the skews measured in 20 kbp windows on both sides of the origins, are: MCM4 (31%), HSPA4 (29%), TOP1 (18%), MYC (14%), SCA7 (38%), AR (14%). (b) Cumulated skew profiles calculated in the 6 regions of the mouse genome syntenic to the human regions figured in (a). (c) Cumulated skew profiles in the 6 regions of the dog genome syntenic to human regions figured in (a). Abscissa (x) represents the distance (kbp) of a sequence window to the corresponding origin; ordinate represents the values of S given in percent; red, (+) genes (coding strand identical to the Watson strand); blue, (-) genes (coding strand opposite to the Watson strand); black, intergenic regions; in (c) genes are not represented.

Fig. 4 .

 4 Fig.4. Mean skew profile of intergenic regions around putative replication origins. The skew S was calculated in 1 kbp windows (Watson strand) around the position (± 300 kbp without repeats) of the 1012 upward jumps (Fig.3); 5' and 3' transcript extremities were extended by 0.5 and 2 kbp, respectively (full circles) or by 10 kbp at both ends (stars) (Data and Methods). Abscissa represents the distance (kbp) to the corresponding origin; ordinate represents the skews calculated for the windows situated in intergenic regions (mean values for all discontinuities and for ten consecutive 1 kbp window positions); the skews are given in percent (vertical bars, SEM). The lines correspond to linear fits of the values of the skew (stars) for x < -100 kbp and x > 100 kbp.

Fig. 5 .

 5 Fig. 5. S profiles along mammalian genome fragments. (a) Fragment of chr. 20 including the TOP1 origin (red vertical line); (b), (c), chr. 4 and chr. 9 fragments, respectively, with low G+C content (36%); (d) chr. 22 fragment with larger G+C content (48%). In (a) and (b), vertical lines correspond to selected putative origins; yellow lines, linear fits of the S values between successive putative origins. Black, intergenic regions; red, (+) genes; blue, (-) genes; note the fully intergenic regions upstream of TOP1 in (a) and from positions 5290 to 6850 kbp in (c). (e) Fragment of mouse chr. 4 syntenic to the human fragment shown in (c); (f) fragment of dog chr. 5 syntenic to the human fragment shown in (c); in (e) and (f), genes are nor represented.

Fig. 6 .

 6 Fig. 6. Model of replication termination. Schematic representation of the skew profiles associated with three replication origins O 1 , O 2 , O 3 ; we suppose that these are adjacent, bidirectional origins with similar replication efficiency; abscissa represent the sequence position; ordinate represent the S values (arbitrary units); upward (downward) steps correspond to origin (termination) positions; for convenience the termination sites are symmetric relative to O 2 . First column, three different termination positions T i , T j , T k , leading to elementary skew profiles S i , S j , S k ; second column, superposition of these 3 profiles; third column, superposition of a large number of elementary profiles leading to the final "factory roof" pattern. Simple model: termination occurs with equal probability on both sides of the origins leading to the linear profile (3 rd column, thick line). Alternative model:

Figure S1 :

 S1 Figure S1: (top) skew profile of a fragment of human chromosome 12; (middle), WT of S using is coded from black (min) to red (max); three cuts of the WT at constant scale a = a* = 200 kbp, 70 kbp and 20 kbp are superimposed together with five maxima lines identified as pointing to upward jumps in the skew profile; (bottom) WT skeleton defined by the maxima lines in black (resp. red) when corresponding to positive (resp. negative) values of the WT.

Acknowledgements

This work was supported by the ACI IMPBIO 2004, the Centre National de la Recherche Scientifique (CNRS), the French Ministère de l'Education et de la Recherche and the PAI Tournesol. We thank O. Hyrien for very helpful discussions.

Supplementary material

Detection of jumps in skew profiles using the continuous wavelet transform.

For effective detection of jumps or discontinuities, the simple intuitive idea is that these jumps are points of strong variation in the signal that can be detected as maxima of the modulus of the (regularized) first derivative of the signal. In order to avoid confusion between "true" maxima of the modulus and maxima induced by the presence of a noisy background, the rate of signal variation has to be estimated using a sufficiently large number of signal samples. This can be achieved using the continuous wavelet transform (WT) that provides a powerful framework for the estimation of signal variations over different length scales. The WT is a space-scale analysis which consists in expanding signals in terms of wavelets that are constructed from a single function, the analyzing wavelet, by means of dilations and translations [START_REF] Arneodo | The Science of Disaster[END_REF][START_REF] Nicolay | [END_REF]. When using the first derivative of the Gaussian function, namely , with , then the WT of the skew profile S takes the following expression: where x and a (> 0) are the space and scale parameters, respectively. Equation (1) shows that the WT computed with is the derivative of the signal S smoothened by a dilated version of the Gaussian function. This property is at the heart of various applications of the WT microscope as a very efficient multi-scale singularity tracking technique [START_REF] Arneodo | The Science of Disaster[END_REF][START_REF] Nicolay | [END_REF]. The basic principle of the detection of jumps in the skew profiles with the WT is illustrated in Figure S1. From equation (1), it is obvious that at any fixed scale a, a large value of the modulus of the WT coefficient corresponds to a large value of the derivative of the skew profile smoothened at that scale. In particular, jumps manifest as local maxima of the WT modulus as illustrated for three different scales in Figure S1 (middle). The main issue when dealing with noisy signals like the skew profile in Figure S1 (top) is to distinguish between the local WT modulus maxima (WTMM) associated with the jumps and those induced by the noise. In this respect, the freedom in the choice of the smoothing scale a is fundamental, since the noise amplitude is reduced when increasing the smoothing scale, while an isolated jump contributes equally at all scales. As shown in Figure S1 (bottom), our methodology consists in computing the WT skeleton defined by the set of maxima lines obtained by connecting the WTMM across scales. Then, we select a scale a large enough to reduce the effect of the noise, yet small enough to take into account the typical distance between jumps. The maxima lines that exist at that scale are likely to point to jump positions at small scale. The detected jump locations are estimated as the positions at scale 20 kbp of the so-selected maxima lines. According to equation (1), upward (resp. downward) jumps are identified by the maxima lines corresponding to positive (resp. negative) values of the WT as illustrated in Figure S1 (bottom) by the black (resp. red) lines. For the considered fragment of human chromosome 12, we have thus identified 7 upward and 8 downward jumps. The amplitude of the WTMM actually measures the relative importance of the jumps compared to the overall signal. The black dots in Figure S1 (middle) correspond to the 5 WTMM of largest amplitude ( ΔS ≥ 12.5%); it is clear that the associated maxima lines point to the 5 major jumps in the skew profile. Note that these are 5 upward jumps with no downward counterpart and that they have been reported as 5 putative replication origins.


Gabriele Ku ¨hl

Wilson R Lourenc
email: wilson.lourenco@mnhn.fr

Pesciara Von

Monte Bolca

Á Euscorpiidae

Unteres Eoza

Gabriele Ku

A new genus and species of fossil scorpion (?Euscorpiidae) from the Early-Middle Eocene of Pesciara (Bolca, Italy)

Keywords: Pesciara of Bolca, Euscorpiidae, Lower Eocene, Scorpions Pseudoscorpion, ist der hier beschriebene fossile Skorpion erst die zweite beschriebene Arachnidenart, die von der Bolca-Lagersta ¨tte bekannt ist

Fossil scorpions are among the oldest terrestrial arthropods known from the fossil record. They have a worldwide distribution and a rich fossil record, especially for the Paleozoic. Fossil scorpions from Mesozoic and Cenozoic deposits are usually rare (except in amber-deposits). Here, we describe the only fossil scorpion from the Early to Middle Eocene Pesciara Lagersta ¨tte in Italy. Eoeuscorpius ceratoi gen. et sp. nov. is probably a genus and species within the family Euscorpiidae. This may be the first fossil record of the Euscorpiidae, which are so far only known from four extant genera. Eoeuscorpius ceratoi gen. et sp. nov. was found in the ''Lower Part'' of the Pesciara Limestone, which is actually dated Late Ypresian stage (between 49.5 and 49.7 Ma). Besides a possible pseudoscorpion, the here-described fossil scorpion is the second arachnid species known from the Bolca Locality.

Introduction

The Bolca Fossil Lagersta ¨tte is a world-famous Lagersta ¨tte for exceptionally preserved fossils from the Eocene. Several hundred plant and animal species have been described from here. Among the animal species, vertebrates (fishes) are dominant and known worldwide. Invertebrates, such as the herein described scorpion, belong to the so-called minor fauna, maybe less famous but no less spectacular.

Geological and paleobiological background and taphonomy

The Bolca region is located in the eastern part of the Lessini Mountains, which are within the Southern Alps in Northern Italy [START_REF] Papazzoni | The Pesciara-Monte Postale Fossil-Lagersta ¨tte: 1. Biostratigraphy, sedimentology and depositional model[END_REF]. The limestone developed during the Eocene in two phases of uplift of the Tethys Ocean. It is surrounded by volcanic ash, and the limestone deposits are about 19 m thick [START_REF] Tang | Monte bolca: an eocene fishbowl[END_REF]. The limestone (Lessini Shelf) is especially recognized for a rich fossil record of fishes, which are known throughout the world for the excellent preservation. The Lessini shelf is surrounded by deep marine basins and restricted northwards by terrestrial deposits [START_REF] Papazzoni | The Pesciara-Monte Postale Fossil-Lagersta ¨tte: 1. Biostratigraphy, sedimentology and depositional model[END_REF]).

The fossil scorpion described herein [START_REF] Cerato | Cerato. I pescatori del Tempo. San Giovanni Ilarione[END_REF]; Fig. 4a) was discovered in the Pesciara Fossil-Lagersta ¨tte, which contains marine life forms as well as terrestrial organisms [START_REF] Guisberti | The Pesciara-Monte Postale Fossil-Lagersta ¨tte: 4. The ''minor fauna'' of the laminites[END_REF].

The Pesciara Limestone was deposited during the Ypresian stage (Lower Eocene), roughly 49.5 Ma ago. The fossils are found in fine-grained, laminated limestones that were deposited between coarser storm-induced limestone layers [START_REF] Schwark | Organic geochemistry and paleoenvironment of the Early Eocene ''Pesciara di Bolca'' Konservat-Lagersta ¨tte, Italy[END_REF]. The paleoenvironment of the Bolca area is generally regarded as rich in variety. Several ecosystems, reaching from pelagic, as well as shallow marine habitats, and even brackish to fluvial and terrestrial habitats, are evidenced by the deposits. Due to the Eocene climatic conditions, temperatures were tropical to subtropical. The deposits generally prove former advantageous life conditions [START_REF] Tang | Monte bolca: an eocene fishbowl[END_REF], allowing a high degree of biodiversity. However, temporally anoxic and euxinic conditions are assumed by the absence of bottom dwellers [START_REF] Papazzoni | The Pesciara-Monte Postale Fossil-Lagersta ¨tte: 1. Biostratigraphy, sedimentology and depositional model[END_REF]. These events may have let to extinction events that are responsible for the rich fossil fauna.

First, a diverse and abundant fish fauna is represented. The rich fish fauna is interpreted as having been close to coral reefs [START_REF] Papazzoni | The Pesciara-Monte Postale Fossil-Lagersta ¨tte: 1. Biostratigraphy, sedimentology and depositional model[END_REF]. Other vertebrates are represented by two snake specimens, a turtle and several bird remains (for a review, see [START_REF] Carnevale | The Pesciara-Monte Postale Fossil-Lagersta ¨tte: 2. Fishes and other vertebrates[END_REF], but also plants are very abundant, with more than 105 macrofaunal genera being described [START_REF] Wilde | The Pesciara-Monte Postale Fossil-Lagersta ¨tte: 3. Flora. In The Bolca Fossil-Lagersta ¨tten: A window into the Eocene World[END_REF].

The fossil fauna and flora are two-dimensionally preserved and frequently fully articulated. Soft part preservation with organs and cuticles is common among the fossils. Even color preservation has been reported. Microbial fabrics may be related to the fossilization of soft tissues [START_REF] Briggs | The role of experiments in investigating the taphonomy of exceptional preservation[END_REF]. However, the taphonomic process is actually not well known.

Arthropods from Pesciara of Bolca

The scorpion described (Fig. 1) here belongs to the so-called minor fauna of the Pesciara-Lagersta ¨tte, which comprises arthropods, polychaete worms, jellyfishes, mollusks, brachiopods and bryozoans. Among arthropods, insects and crustaceans are most abundant [START_REF] Guisberti | The Pesciara-Monte Postale Fossil-Lagersta ¨tte: 4. The ''minor fauna'' of the laminites[END_REF]. Arachnids, such as the scorpion Eoeuscorpius ceratoi gen. et sp. nov., are only known by two fossils. One is the scorpion described here. The other arachnid is a possible pseudoscorpion from this Lagersta ¨tte [START_REF] Guisberti | The Pesciara-Monte Postale Fossil-Lagersta ¨tte: 4. The ''minor fauna'' of the laminites[END_REF].

In general, the order Scorpiones goes back to the mid Silurian of Scotland (see Dunlop 2010 for review). Scorpions from the early Paleozoic generally differ from subsequent groups by a simple coxo-sternal region and the lack of trichobothria, as the latter structures developed as a consequence of terrestrialization. Beginning with the Devonian, a coxapophyses/stomotheca developed in scorpions, which were then very abundant during the Carboniferous [START_REF] Dunlop | Geological history and phylogeny of Chelicerata[END_REF]. Currently, 136 valid fossil scorpion species have been described, most of them from Paleozoic fossil sites. Mesozoic and Tertiary fossils are comparatively rare, though amber seems to be a good resource for fossil scorpions [START_REF] Dunlop | How many species of fossil arachnids are there?[END_REF][START_REF] Dunlop | A summary list of fossil spiders and their relatives[END_REF][START_REF] Lourenc ¸o | A synopsis on amber scorpions, with special reference to the Baltic fauna[END_REF][START_REF] Lourenc ¸o | A new species of scorpion from Chiapas amber, Mexico (Scorpiones: Buthidae)[END_REF][START_REF] Lourenc ¸o | A Synopsis on amber scorpions with special reference to Burmite species; an extraordinary development of our knowledge in only 20 years[END_REF].

Materials and methods

The description of the Pesciara scorpion is based on a single specimen, which is the property of Mr. Massimo Cerato in Bolca of Vestenanova and was kindly loaned to us for scientific description. The scorpion, collection number CMC1, is currently stored at the Museum of the Cerato Family (via San Giovanni Battista, 50-37030 Bolca di Vestenanova-Verona).

The scorpion was x-rayed with a Phoenix v|tome|x s Micro Tomograph, but this provided no additional information. The scorpion was also photographed using a Nikon D3x. Details were photographed with a Keyence Digital Microscope. A Leica MZ95 was used to produce fluorescent images.

Image editing was carried out with Adobe Photoshop CS6 in addition to Adobe Illustrator CS6. Measurements were done with the help of ImageJ. Each structure was measured in length and width [mm], except some structures that were regarded as highly fragmentary. Length and width were measured along the middle of each segment (see Table 1).

Systematic paleontology

Phylum Arthropoda von Siebold, 1848 Class Arachnida Lamarck, 1801 Order Scorpionida Koch, 1837 Family ?Euscorpiidae Laurie, 1896 Genus Eoeuscorpius gen. nov.

Diagnosis of the genus. Scorpion of small size with a total length of 38 mm. General morphology very similar to that of most extant species of the genus Euscorpius Thorell, 1876; however, both body and pedipalps are more bulky and less flattened. Carapace with a strong anterior emargination. Trichobothrial pattern, most certainly of the type C [START_REF] Vachon | Etude des caracte `res utilise ´s pour classer les familles et les genres de Scorpions (Arachnides). 1. La trichobothriotaxie en arachnologie. Sigles trichobothriaux et types de trichobothriotaxie chez les Scorpions[END_REF]; a number of bothria can be observed: 3 on femur, internal, dorsal and external, 1 dorsal d 1 , 1 internal and a few external on patella; the internal is partially displaced; 4-6 on dorso-external aspect of chela hand and 5 on chela fixed finger. Diagnosis of the species. As for the genus.

Etymology. The name honors Mr. Massimo Cerato, Bolca of Vestenanova, Italy, who allowed us to study the specimen. Description. The scorpion is exposed from its dorsal side, nearly completely preserved and in an excellent state of preservation (Fig. 1a), although the distal segments of the walking legs are not well preserved. The cuticle has a brownish coloration and therefore optically stands out against the paler sediment. The cuticle surface is not completely preserved, as smaller areas of usually less than 1 mm are missing. The cuticle surface of the mesosomal tergites is to some extent transparent, allowing a view to the ventral cuticle. The median eyes are not preserved. In that area the sediment matrix is exposed, indicating the former position of the eyes and eye tubercle. The right carapace half is incomplete but can be reconstructed from the left half. On the cuticle surface, especially of the pedipalps, numerous insertion points of bothria and setae are preserved (Fig. 2a,b).

The body of the fossil scorpion measures ca. 38 mm in length and ca. 20 mm in width (Fig. 1b). Chelicerae are ca. 2 mm long and 1.3 mm wide. With a width of 4.6 mm and a length of ca. 7 mm, the chela-bearing segments of the pedipalps are very strong, and they are the optically dominant structures of the scorpion. The carapace is 4.8 mm long and 2.1 mm on the anterior width and 4.8 mm on the posterior width. In the middle region, the mesosoma is 6.6 mm wide on average. These measurements give an impression of the scorpion size. More detailed measurements are listed in Table 1.

The carapace of the scorpion is sub-quadrangular with a strong convex emargination at the anterior margin. The cuticle of the anterior region is darker than the rest, which may be because of the carapace thickness. Lateral eyes would at best be preserved on the left carapace half, but their number cannot be determined with certainty. As mentioned before, the median eyes are not preserved, but their former position is marked by a heard-like notch on the carapace surface. The median eyes are situated in the middle of the carapace. Posteriorly, a deep furrow separates the carapace in two halves.

At the anterior to the frontal carapace margin, a small (1.3-mm-long and 0.8-mm-wide) laminated structure is exposed (Fig. 1b shaded area, Fig. 3). About 36 laminae are within the oval structure, with an average thickness of 0.02 mm. This structure is interpreted as exposed muscle fibrils.

Although the chelicerae are normally best seen from the ventral side, in the specimen described herein the tibia and tarsus of the chelicerae are also exposed dorsally (Fig. 1a,b). As in most scorpions, the chelicerae are very small (2 mm long/1.3 mm wide for the complete structure). Parts of the more basal segments (e.g., the coxa) are also preserved, but unfortunately not in detail. The tibia is produced into the fixed finger. The inner ventral margin is equipped with a bristlecomb (Fig. 4a,b). On both the fixed and moveable finger (tibia and tarsus), tooth denticles are preserved. Roughly the teeth can be distinguished into distal, subdistal and median teeth [START_REF] Vachon | De l'utilite ´, en syste ´matique, d'une nomenclature des dents des che ´lice `res chez les Scorpions[END_REF][START_REF] Sissom | Systematics, biogeography and paleontology[END_REF]). Again, the preservation is not detailed enough for further descriptions.

The pedipalps of the fossil are comparably short and stout. Especially the patella is considerably large. It has a roundish shape and on the cuticle surface three carinae from anterior to posterior. The two carinae on the right side form a V as they meet at the posterior region of the patella (Fig. 2a,b). On the cuticle surface of the patella, Fig. 3 Laminated structure on the scorpion surface above the carapace margin. Possible remains of muscle fibrils. Scale 0.5 mm several insertion points show the former position of the bothria and other setae. These structures cannot be fully observed. However, some of the insertion points are larger than others. These larger insertion points (filled circles in Fig. 2b) are most certainly the remains of bothria. The trichobothrial pattern can be observed on the doral side on the pedipalps. Three bothria (internal, dorsal, external) are preserved on the femur. On the patella, one dorsal and one internal bothria is preserved, as well as four external bothria. The internal bothria is partially displaced; four to six bothria are preserved on the dorso-external aspect of the chela hand, and five bothria are on the chela fixed finger.

Though incompletely preserved, the overall impression of the legs is that they were slender compared to the robust pedipalps. The tibia of the walking legs is broader than the preceding and following leg segments. The basitarsus and tarsus are shorter than the more basal segments. Tarsal claws are not preserved.

The mesosoma consists of seven segments, covered by mesosomal tergites. Tergites are rectangular in shape, with rounded edges. A carina proceeds close beneath the anterior margin of each mesosomal tergite, except on tergite VII (Fig. 1a,b). The width of the dorsal mesosomal tergites varies from 5.8 to 6.5 mm from tergite I to tergite VII. There is more variation in the length (measured from anterior to posterior). The first and second mesosomal tergites are only about 0.9 mm long; the third measures 1.4 mm. The fourth mesosomal tergite is about 1.6 mm long. The following mesosomal tergites show similar lengths of 2.3 and 2.4 mm. The seventh mesosomal tergite differs from the others in being trapezoid. It is roughly 3 mm long. The anterior part is 5 mm wide, whereas the posterior part measures only 3.3 mm.

Two additional ventral plates of mesosomal segments five and six are preserved. Their shape and size are comparable to their dorsal pendants.

The metasoma of the fossil scorpion consists of five segments, plus the telson (Fig. 1a,b). With the exception of segment V, tail segments are approximately of the same size. Segment V is one and half times longer than the preceding ones. On each metasomal segment, two longitudinal carinae are preserved. The cuticle surface is densely covered with granules. The telson aculeus is partly covered by segment V, because it is bent backwards (as in life position). The tip of the aculeus is broken.

Discussion

The scorpion is one individual of the minor fauna (Guisberti et al. 2014), which is the animal non-fish fauna and comprises inter alia a few arthropod genera. The scorpion is originally regarded as terrestrial, so it was deposited allochthonously. As the depositional environment was not far away from the coastline, it was most probable washed in from nearby land.

A definitive phylogenetic position of the scorpion is difficult to determine because of the incompleteness of the specimen. According to the observed characters-the general morphology, shape of pedipalp segments (i.e., femur, patella and chela), presence of a small apophysis on the internal aspect of the patella, and the same numbers and positions of some trichobothria-the specimen is unquestionably a representative of the Chactoidea and can be assigned temporarily to the extant family ?Euscorpiidae (see Lourenc ¸o 2015). However, because of the incompleteness of the specimen and in particular because of the geological horizon (Eocene), the specimen is assigned provisionally to a new genus.

Euscorpiidae were hitherto only known from extant representatives. The family comprises 31 species, belonging to four genera (Lourenc ¸o 2015). Eoeuscorpius ceratoi gen. et sp. nov. would be the fifth genus (comprising one species), probably giving the family Euscorpiidae a fossil record that goes back more than 49 million years.

  Etymology. The generic name refers to the geological position of the new genus within the Eocene, which is intermediate in relation to elements of the family Palaeoeuscorpiidae Lourenc ¸o, 2003 and the extant genus Euscorpius (Lourenc ¸o 2003). Type species. E. ceratoi gen. et sp. nov., from the ''Lower Part'' of Pesciara Limestone, Early Eocene, Ypresian stage. Eoeuscorpius ceratoi gen. et sp. nov. Figure 1a, b. Material. Holotype, CMC1 (Museum of the Cerato family, Verona).

Fig. 1 a

 1 Fig. 1 a Holotype of Eoeuscorpius ceratoi gen. et sp. nov.; the color of the photography is inverted. b Line drawing of the holotype; dashed lines of the trunk and leg indicate indistinct segment (legs) respectively dorsal sternite margins. Densely dashed lines beside and

Fig

  Fig. 2 a, b Right pedipalp chela of Eoeuscorpius ceratoi gen. et sp. nov. br bristles, bt bothria, c carina, mf moveable finger, ti tibia. Scale 1 mm

Fig. 4 a

 4 Fig. 4 a Left and right chelicera of Eoeuscorpius ceratoi gen. et sp. nov., fluorescence illumination. b Line drawing of chelicera. bc bristlecomb, d distal tooth, sd subdistal tooth, m median tooth, mf moveable finger, ti tibia. Scale 1 mm

Table 1

 1 Measurements of Eoeuscorpius ceratoi

		t sting				4.1/	1.8
		ts5				3.4/	2.9
	gen. et sp. nov	Tagma L/W ch pd wl 1 wl 2 wl 3 wl 4 Sternal ms1 ms2 ms3 ms4 ms5 ms6 ms7 ts1 ts2 ts3 ts4	(mm) s	Sternal plates Dorsal carapace, left half (complete wide) 2.5/ 2.5/	6.2 6.2	Tergal plates 4.8/3.2 (6.4) 0.9/ 0.9/ 1.4/ 1.6/ 2.3/ 2.4/ 3.1/ 2.4/ 1.9/ 2.4/ 2.6/	5.1 5.8 6.0 6.6 6.7 6.5 4.8 2.9 2.7 2.3 2.5	cx l	cx r	tr l 1.2/	1.9	tr r 1.8/ 1.1/ Laminated structure (near carapace) 1.3/0.8	2.7 1.2	fe l 3.5/ 3.2/ 2.4/ Eye hole 0.6/0.7	2.0 1.6 1.4	fe r 4.6/ 2.3/ 2.3/?	2.2 1.1	pa l 2.4/ 2.4/ 3.0/	2.0 1.5 1.2	pa r 3.1/ 2.0/ 3.1/	2.2 1.4 1.2	ti l 1.9/ 6.9/ 1.6/ 3.3/ 2.7/	1.3 4.7 0.7 1.6 1.6	ti r 1.9/ 6.9/ 1.6/ 2.7/ 2.7/	1.3 4.5 0.7 1.5 1.2	bt l 1.4/ 1.8/ 1.3/	0.5 0.7 0.8	bt r 1.6/ 1.2/	0.7 0.6	ta l 1.3/? 0.5/ 1.5/ 1.6/	0.4 0.6 0.6	ta r 1.3/? 4.3/ 0.8/ 1.6/	0.9 0.4 0.4	First row is divided into the tagmata from anterior to posterior. First column is divided into appendage segments	l/r left/right, cx coxa, tr trochanter, fe femur, pa patella, ti tibia, bt basitarsus, ta tarsus, ch chelicera, pd pedipalp, wl walking leg, ms mesosomal segment, ts tail segment

Acknowledgements Before all others, we thank Mr. Massimo Cerato (Verona) for access to his fossil scorpion. We also sincerely thank Roberto Zorzin (Verona) for friendly communication, for information on the fossil and helpful comments on the manuscript. Additionally, we thank Torsten Wappler (Bonn) for technical help with pictures and Georg Oleschinski (Bonn) for the high-quality photographs. Additionally, we would like to thank the reviewers (Jason Dunlop and Andrea Rossi) and editors (Joachim Haug and Mike Reich) for helpful comments and constructive suggestions, which helped to improve our manuscript.


The aim of this paper is to compare the vision of the city and its streets in Thai modern short stories. This study is based on the research I am doing for my thesis entitled : "Fiction, ville et société : les signes du changement social en milieu urbain dans les nouvelles thaïes contemporaines" at the Institut National des Langues et Civilisations Orientales (Paris). This research focuses on short stories by four authors who all received the Southeast Asia Write Award : Atsiri Thammachot, Chat Kopchitti, Sila Khomchai and Wanit Charungkit-anan. In my corpus of short stories, I chose six which show different aspects of the street, such as : description, traffic jam, relations between people in the street, vision of the street according to social class, and conflict between tradition and modernity.

Corpus

Besides the fact that the four authors chosen for my corpus have received the Southeast Asia Writer Award, they all belong to the same generation (born between 1947 and 1954) and are all well-known in their country. The four of them were born in the countryside and came to Bangkok to attend university. They retain from their childhood in provincial towns a nostalgia that is apparent in their short stories and novels. By Atsiri Thammachot, I have selected two short stories : " Thoe yang mi chiwit yu yang noy ko nai chai chan " (She is still alive, at least in my heart) and " Thung khra cha ni klai pai chak lam khlong sai nan " ( It is time now to escape far from this khlong). Both are extracted from the collection of short stories entitled "Khunthong chaw cha klap mua fa sang" (Khunthong, you will come back at dawn) for which Atsiri got the SEA Write in 1981.

Born in 1947, Atsiri spent his childhood in Hua Hin where his parents had fisheries. After studying journalism at Chulalongkorn University, he began to work with the Sayam Rat, where he is still working today, writing short stories at the same time. In his literary work, the action is often located in the countryside or in small towns, and the problems of urbanisation, modernisation and social change are recurrent. He also focuses on the return to the village after working in Bangkok, as shown in the short story Sia lew sia pai (What is gone is gone).

The first short story, Thoe yang mi chiwit yu yang noy ko nai chai chan, is taking place during the events of October 1976. Coming out of his house, a journalist runs into a young woman who is involved in the struggle for democracy. Days later, he receives the list of the people killed in the massacre. The name of the woman is in it. Atsiri shows in this short story how a journalist can see himself as a coward and feel ashamed for not having had the courage to take part directly in the events.

In Thung khra cha ni klai pai chak lam khlong sai nan, the author shows how a woman, living alone with her two children in a hut on a khlong bank, feels so bad about the life and the surroundings she is offering to her children, that she decides to quit the khlong. This short story points out how the city can destroy people.

Chat Kopchitti, born in 1954 in Samut Sakhon, studied art in Bangkok. He had many jobs before he decided to be only a writer. According to Marcel Barang : " He wasn't quite 20 when he decided that creative writing was his life and five years later he turned down a life in business to gamble on a literary career" (Barang, 1994, p.334). Chat got the SEA Write twice : once in 1982, for his novel Khamphiphaksa (The judgement), and again, in 1994, for Wela (Time). In 1983, Raphiporn declared : "Chat Kopchitti avec son roman le Jugement annonce un nouveau défrichement de ce genre littéraire, une composition plus brillante, à laquelle nous, les anciens, n'avions jamais pensé." [START_REF] Fels | Promotion de la littérature en Thaïlande[END_REF]. Chat published a lot of novels and short stories collections, showing the life of people living in marginality (Phan ma ba) or in social rupture (Khamphiphaksa). Some of his short stories, written like tales, like Mit pracham tua and Nakhon mai pen rai, point out the flaws of society and the use of power by the elite. Chat's vision of society is rather pessimistic.

The short story Ruang thamada (An ordinary story) presents the relations between the narrator and an old woman whose daughter is dying of cancer. The narrator is witness and actor at the same time. Beyond the relations between these two characters, it is all the problems encountered by people coming from the countryside which are shown. The conflict between tradition and modernity is evident in this text : traditional healer versus modern doctor ; village customs versus city behaviours ; solidarity versus individuality. All along the story, the narrator speaks to the reader, using khun, to involve him in the action.

Khrop khrua klang thanon (A family in the street), written by Sila Khomchai, is one of the most representative short stories of this corpus because the whole story takes place in the street. Actually, the street is the main character in the story which recounts the life of a middle-class couple. Living in the suburbs of Bangkok, they spend most of their time in their car, stuck in traffic jam, eating, reading, speaking, playing, observing the others.

Sila Khomchai (born in 1952 in the province of Nakhon Si Thammarat) took an active part in the events of 1973-1976 and had to hide in the jungle after the massacre. When he came back to Bangkok in 1981, he became journalist and continued to write fiction. If most of his short stories and novels reflect his political commitment, Khrop khrua klang thanon is more a criticism of urban life and, somehow, of the middle-class. This short story won the SEA Write in 1993.

The second story by Sila Khomchai that I chose is entitled Khop khun ... Krungthep (Thank you Bangkok). In this short story, a taxi driver and his customer, going through Bangkok at night, develop a strange relation : each imagines that the other is going to attack him. During the whole journey, they are anxious, with feelings of fear and mistrust.

The last author I will consider here is Wanit Charungkit-anan. Born in 1949, in the province of Suphan Buri, Wanit studied at Silpakorn University in Bangkok. Editor, columnist, poet, author of numerous novels and short stories, Wanit is a very famous writer. He received many awards, among which the SEA Write in 1984 for his short story Soi diaw kan (The same soi).

The short story I selected, Muang luang (The capital) is quite well-known in Thailand and even abroad, since it has been translated into several languages. This story gives a very different vision of the city than Sila's Khrop khrua klang thanon. The main character is a rather poor worker in Bangkok who describes the street and the people seen from the bus. The description he makes is very pessimistic : tired and desperate workers, inextricable traffic jams, dangerous and hostile city. In the bus, a man from Isan province is singing a folk song that gives the narrator a deep feeling of nostalgia.

Thematic analysis

The usual definition of 'street', as we can find it in dictionaries, is reduced to a minimum. In English dictionaries, as well as in French or Thai dictionaries, the street is defined as a town or village road with houses on one side or both. Beyond the simple description, the aim of this research is to analyse the way the authors see the street and show it in short stories as a social area where all the different communities of the city pass by one another, having or not some contact.

In Bangkok, the life in the street is very rich. Three kinds of 'street' -in the meaning of 'way of communication' -can be distinguished : the large avenues, the soi and the khlong. A fourth kind, reserved to the motor vehicles, is the express highway, created to break up the traffic jams. Highways are now very extensive, forming a second level of road network above the old streets.

The organisation of traffic in the avenues and the soi is rather difficult, especially because many soi are dead ends, making communication between the large roads almost impossible.

Life in avenues is quite different from life in soi. While the large streets seem to be only ways of communication and commercial areas, the soi are where people live, re-creating the village.

Nowadays many khlong, traditional waterways, have been filled in and covered by roads and buildings. If Bangkok is no longer the Asian Venice, khlong still have a role in communication. In Thon Buri, of course, but also in other districts of the town, boats transport people and goods, using the khlong as a street.

Bangkok, and the city generally, is viewed by the authors of my corpus as a terrible place, for the conditions of life (traffic jams, housing far from the centre, difficulties to find a job...) and for the relations between the people. Urban society and the city are often described as monsters devouring the countryside people, leading astray men and women and getting more and more westernised. In his book Aphet kamsuan (Bad omen), Win Liaw-warin gives a dictionary of life for middle-class people in Bangkok. Under 'Krungthep', he writes : "If Krungthep were a woman, she would be a woman of easy virtue fascinated by the cheap Western culture". About the word 'dream', Win says : "There are two kinds of dream : the good one is dreaming that you fall in Hell (and wake up in Krungthep) ; the bad one is that you go to Heaven (and wake up in Krungthep)" [START_REF] Liaw-Warin | Aphet kamsuan[END_REF]. This shows well enough the feelings of the writers, which are shared by a lot of Bangkok inhabitants.

The different themes about the street in the city, which appear in short stories, reveal the importance of the street in the social urban context.

Description

In most of the short stories of my corpus, the descriptive part is not a very important one. Due to the shortness of the text or by choice of the author, the accent is more on the characters and the action than on the description. However, some places are described throughout the story.

The opposition between avenues and soi is quite evident in Chat's story Ruang Thammada.

Leaving in an old wooden house located in a soi, the narrator make the difference between the street where he lives, and the streets around, that he calls "the jungle" and the big avenues, where "one can find all things making civilisation, as luxurious hotel, cinema halls, massage parlours, bowlings, restaurants, bookshop (...) and very smart people. (...) The atmosphere is perfumed and air-conditioned, people look beautiful, there is lifts, escalators and other signs of progress. Coming from the soi is like coming out of the barbarism and emerging in the centre of a fairy tale city, except that it is a real city." Speaking about the city, Chat named it muang neramit, the 'city built by supernatural powers'. The opposition between soi and main street is really evident in this text. Atsiri, in Thoe yang mi chiwit yu..., describes the soi (which is actually called trok) where lives the narrator as "long and narrow as a railroad". The narrator has to walk to join the main road, since there is no buses crossing in his soi.

The khlong as a way of communication is well represented by Atsiri in his short story Thung khra cha ni klai... The mother and her two children are living in a hut under an arch of a bridge that crossed over a dirty khlong, surrounded by big buildings. Just like in a street, vendors are passing in the khlong, paddling in the stream. Even the sex market is present : at night, the family can hear the prostitutes paddling up and down the khlong. Afraid that her little girl could become one of them, the mother will decide to quit the dirty khlong.

During the night, the city changes its appearance. Lights, streets and people are not the same than in daytime. For the narrator of Ruang thamada (Chat), the city at night is a place of pleasure. At the end of the story, after the death of the daughter of his neighbour, the narrator decides to go to the city : "Tonight, I am going to walk around, to sit somewhere having a drink, or even to get a girl in the fairy tale city". In Khop khun...Krungthep, Sila shows a city deserted, crossed by fast cars and illuminated by advertising lights. It is two o'clock in the morning : "[the taxi] goes fast in the dark streets. In the headlights, some closed buildings appear on both side of the streets ; the side-walks are deserted. From time to time, headlights of an other car shine while passing the taxi, in a roar of engine". Arriving on Anusawri Chai : "[the place] is empty and wide. The white shining lights of the street lamps make a warm atmosphere. The advertising billboards pierce the black screen of the night with multicoloured and flashing lights". This description is quite far from the one of the daytime city, crowded, polluted, and congested !

Traffic jam

From the moment that a short story is developed within the context of the city, traffic jam takes a central role in the story. The congested streets are described in a lot of short stories, but in two of which, they are almost the principal characters.

Muang luang, by Wanit, and Khrop khrua klang thanon, by Sila, give two very different visions of the traffic jam in Bangkok. The family of Sila, actually a middle-class couple, is driving in Bangkok, spending most of their time in car. Having an appointment at three o'clock in the afternoon, they decide to leave their house, located in the North suburbs, at nine in the morning. The husband, who is also the narrator, describes the way his wife prepares the car : "She put on the back seat a basket full of food, an icebox with cool drinks (...) She put also some plastic bags for rubbish, a spittoon, a spare suit hanging above the window. Just as if we were going for picnic !" In the car, they eat, play, listen to the radio, and even make love.

They think to the new car they want to buy, more spacious. Especially at the end of the story, when the wife announces to her husband that she is pregnant : "My wife is pregnant ! Pregnant in the street ..." the husband wants to yell. For this couple, traffic jam become more or less a way of life : the car is means of transport, house, and office as well.

The hero of Muang luang, by Wanit, has not the same reaction towards the city and traffic jams. Bus user, he feels exhausted and sick of his life in Bangkok. Spending hours packed tightly in the bus stuck in traffic jam, he dreams of the village where he was born, of the girl he left there. At a cross-road, traffic jam is so long that he gets off the bus : "How the cars could go ? Going through this city is so difficult. The traffic lights have no meaning. Cars which get green light can't move because other cars are stuck in the middle of cross-road . (...) Green light become red ; on the other side, red light become green. And all comes to the same thing, cars crawl along and stop". And when the narrator walks in the street, it is even worse : "I was feeling so bad I could die when I was waiting to cross the street in Rachaprasong corner. I was standing on an island, exposed to polluted smokes, almost wanting to spit. (...) I suffocated, almost in blackout".

Relations between people in the street

Reading these short stories give the feeling that the relations between people in Bangkok streets are quite similar to relations encountered in European capitals. The main feeling shown in the texts is indifference towards the others, just as in Paris. The indifference is especially clear in Muang luang (Wanit). The hero, walking in the street to the bus stop, almost received on the head a stone felt from a building under construction. Nobody notices the fact, neither the other pedestrians nor the workers. Arriving at the bus stop, he looks to the people waiting for the bus : "People waiting at the bus stop are as usual. Nobody pays attention to the others".

After the struggle to get in the bus, the narrator try to find a sit in the bus that is full : "Two children and their mother are holding on the back of a seat, standing in the middle of the bus.

A young guy is sitting in front of them, but he does not think to give his seat. I do not blame him ; if I was sitting, I am not sure I would give my seat to someone else".

The indifference is sometimes verging on non-assistance. Chat describes in Ruang thamada how the people walk in the street near a man lying on the side-walk : " (...) quite often, I see somebody lying on the side-walk or on a footbridge. People come and go, but nobody stops, nobody takes care of him, nobody takes time to check if he is still alive, or if he is still breathing. People pass in front of him as if he was a rubbish heap -some of them do not even see him. This is an ordinary story (in our urban society). If someone stops to check or to give assistance, that is extraordinary".

In other cases, people feel contempt for the ones who are acting in an unusual way. When the Isan man begins to sing in Muang luang, some people appreciate it, but most of them laugh with contempt, looking at him as if he was crazy.

With indifference and contempt, a third feeling is shown by the inhabitants of the city : the fear. The fear of each other, even when there is no reason to feel it. The short story of Sila, Khop khun ... Krungthep, illustrated well enough this irrational feeling. The taxi driver, remembering that a friend of him has been attacked one night and that every day, in newspapers, he can read about violence, becomes really frightened by his customer. Tall and strong, the customer wear a thick moustache and has a scar on the cheekbone, under the left eye. He holds tight on his knees a black bag that seems very precious. His odd-looking makes the taxi driver really nervous and anxious. The driver tries several times to start up a conversation with the customer, but this one answers only by few words. Actually, the customer is afraid of the driver, and the driver of the customer. Throughout the story, they feel more and more anxious, suspicious, and frightened, until they arrive to the house where the customer wanted to go. After he left the car, the two of them feel free and thankful. Thankful for each other, and thankful for the city, that is not as bad as they think. That is why the short story is entitled Khop khun ... Krungthep.

Fortunately, the relations between people in the street are not always that pessimistic ! Characters of the short stories encounter sometimes people they like or who give them good feelings.

The hero of Khrop khrua klang thanon takes advantage of being stuck in traffic jams for encountering people who could be useful in his job. Walking around his car stopped, he speaks with men : "We speak about our problems, we criticise politics, we chat about business or sport. We are like neighbours. (...) I work in advertising business (...) I find sometimes some unexpected customers". Later, the narrator meets a strange guy who is planting out some banana trees on the central strip of the road. The guy wants to plant out more and more trees to fight off pollution.

Despite the discouraging feelings shown by the hero of Muang luang, he makes an encounter in the bus which changes his state of mind. When he hears the Isan man singing, the narrator thinks at first that he is dreaming. Listening to the folk song, his mind is transported to his village, with his girlfriend. It makes him feeling better, forgetting his bad situation in Bangkok. At the end of the story, the narrator gets off the bus, following the singer. He asks him : "Excuse-me to ask you that, but are you crazy ?" The singer answers : "No, but I wish I am".

The journalist of Thoe yang mi chiwit yu... (Atsiri) meets a young woman who is running in his soi, frightened by people chasing her. The story takes place during the events of October 1976, and the young woman is carrying some political posters. Although they just speak a brief moment, the journalist feels himself very involved in this encounter. When the girl leaves, she gives him her name, that he writes on a piece of paper. Later on, he find her name on the list of the people killed in massacre. This encounter symbolise the relation between people who were involved in the political events and the ones who did not dare to. There is a lot of emotion in all this short story, and despite the sadness, a kind of hope.

Vision of the street according to social class

As seen before, the vision of the street and of the city is quite different, whether heroes are car users, bus users or pedestrians. And of course, the way of transportation is usually connected to the social class.

In the short stories chosen for this paper, three kinds of people are represented : the middleclass, in Khrop khrua klang thanon, in which the hero is working in advertising and seems quite fashionable, living in modern style, and appreciating the urban life ; the employees, in Ruang thamada or Muang Luang, who have definitely not the same standard of life and who did not really choose to live in Bangkok but have to for economic reasons ; the very poor, in Thung khra cha ni klai... , who have to struggle for life at every moment, living in a slum, having no job, and feeling bad because the children are not living in good conditions.

Even if, sometimes, the narrator of Khrop khrua klang thanon seems to regret the countryside, he appears like a very integrated person in the urban society. Living in the suburbs, he points out a paradox : "If we were poor, we could live in a slum in the heart of the city, as high class people who reside in condominiums (...)". It is actually what is shown in Thung khra cha ni klai ... The poor woman who lives in a hut by the khlong is surrounded by rich buildings and restaurants. The hero of Khrop khrua klang thanon is attached to the signs that prove his social status : the place where he lives, and the car : "Having a car allows us to rise our social position".

On the opposite, the hero of Muang luang endure his life in Bangkok with a lot of difficulty.

He is suffering of the transports, the heat, the loneliness. Forced to come in Bangkok for working and living, he always keeps in mind his province : "If only I could choose ! I should not be in this terrible big city".

The mother in Thung khra cha ni klai... has a vision of the city even worse. She compares the city to a tiger, that pulls her life to pieces. She came also from countryside, with her husband.

He promised her that they will get a better life, jobs and money. But then, he left her with their two children and disappeared in the big city. And her life is worse than before, because of the city and the hard urban life.

Conflict between tradition and modernity

The opposition between tradition and modernity is to be seen in a lot of short stories. Many themes are linked to this conflict, especially the nostalgia for the province. For most of the characters of short stories -and thus, for the authors -the tradition as found in villages is often idealised in opposition to the bad effects of the modern city.

The narrator of Muang luang feels really nostalgic listening to the Isan folk song : "Yes, it is that ! Exactly ! Behind my house, there was some palm trees. I plaid flute, I was an applauded singer of ram wong in the village". Thinking about his girlfriend, he dreams : "To take along my girlfriend in a boat, for fishing together. It is a dream I have, but it is only a dream". But still, he keeps the sense of reality, saying : "I would like to come back in my place, in province. I would like it so much, but what can I do there ? There is no job at all, except to fish or to collect shellfishes. Not enough for living expenses. I could not stand a job of labourer in a rice-processing factory".

Even the narrator of Khrop khrua klang thanon, who seems to like his urban life, think about the traditional way of life : "I know that after we, human beings, have destroyed the nature all around us, our own inner nature has been consumed by urban life, pollution, traffic jams... The family life, that was an hymn to happiness by its rhythm and elements, felt in incoherence and instability".

The characters of Ruang thamada, living in an old house in a soi, are re-creating the village life in their house. The old woman, refusing modern medicine in hospital, calls a traditional healer to cure her daughter. Although she is living in Bangkok, not far from hospitals, she reacts as if she was still inhabiting a village. Traditional healer, astrologer, masseuse are trying to remedy to the cancer, but without success. The narrator tries several times to persuade the mother to take her daughter to hospital, but she refuses, arguing that the modern methods were not efficacious and too expensive. The narrator does not dare to insist, feeling that if the girl dies in hospital, the mother will accuse him. The narrator is really representative of the young employees class in urban society. He is always hesitating between tradition and modernity, solidarity and indifference, commitment in traditional values and fascination for Westernised city. These oppositions are symbolised by the three conditions that determined his choice for a room : "I wanted a room that be cheap, near civilisation and far from crowd".

Conclusion

As seen in this paper, short stories are a very rich material for studying about city and urban society. I tried here to expose only a few themes connected to the street as a social area, but, of course, a lot of other themes can be analysed, especially about how the traditional ways of life are re-created in urban environment and how the urban specifies are taken back to villages.

If the four authors of my corpus have distinct visions of the city and urban culture, they all point out the changes of the Thai society and the transformations of the traditional values in contact with modernisation and Westernisation of the city.

Prospects of research about literature and city, are obviously wide and numerous. Since the city is in perpetual change and development, we can imagine that literature will follow the same way. How the financial crisis -that makes the city changing too -will be perceived and shown by Thai writers should be a very interesting point to study.

Loved and hated, Bangkok makes everybody concerned : inhabitants, writers, researchers and even tourists... In his dictionary, Win Liaw-warin writes : "If Krungthep were a cocktail, it would be composed of : 10% of natural sweetness ; 40% of synthetic sweetness ; 30% of lead essence ; 20% of dirty sediments". Let us hope that the natural sweetness will grow up.

Selected bibliography

Corpus

Atsiri Thammachot


Professor Juan Faus Payá

Julve Miguel
email: miguel.julve@uv.es

Lloret Francesc

Verdaguer Michel

Journal of Coordination Chemistry celebrating his retirement from the University of Valencia. The three authors have very close and friendly long-lasting relations with Professor Faus even in different contexts. Two of us (FL, MJ) received their chemical education from him and became his close co-workers, whereas the third one (MV) developed a tight Spanish-French collaboration between the team of Professor Faus in Valencia and the laboratory of Olivier Kahn at Orsay in the 1980s and then with his group in Paris in the 1990s. Professor Faus is a scholar with a wide and deep culture. Even if his well-

The teacher

Professor Faus was appointed as an Assistant Professor in 1968 at the Department of Inorganic Chemistry of the University of Valencia. He became Full Professor at the same Institution in 1980. He held this position until his retirement in 2017, after almost 50 years of continuous dedication to the University. Amazingly, he decided to continue to work in the old Inorganic Chemistry building of the university, even when the new and more functional buildings of the Institute of Molecular Chemistry (ICMol) became available. His passion for teaching induced him to stay closer to the students by remaining in the old building. Professor Faus was, and remains, a great teacher. He taught many generations of students. His lectures, perfectly clear, organized and documented, the care brought to help the students are unanimously appreciated and recognized by his students and colleagues. In this respect, M. Julve, one of his former students, can testify that the students were so delighted with Professor Faus's classes that they asked him to extend them after the end of the academic year, which he did with pleasure. He was accustomed to receive the students between his classes to answer kindly their questions. He had a special ability to listen, to instil confidence, to push everyone to reach her/his full potential, and to recognize in each her/his individual skills. His present co-workers are indebted to him for such confidence and permanent support.

Figure 1. Juan Faus, going for a lunch at the Albufera, after a working session in the university. From left to right: J. Faus, M. Julve, F. Lloret, and M. Verdaguer.

The researcher and group leader

Prof. Faus and his former PhD, Prof. José María Moratal, created the research group of Coordination Chemistry at the Department of Inorganic Chemistry of the University of Valencia in 1976. Before this date, his first publication appeared in "Quimica Analitica". It concerned analytical chemistry, the identification of alkaline cations by paper chromatography using the reaction of dihydrogen sulfide with alkali metal violurates. It is cosigned by the Head of Inorganic Chemistry in Valencia at that time. In the mid-1970s, Spain knew a sudden burst of changes and hopes in many aspects of the social life. It is significant that the new group was born at this time. Juan Faus and his first students (Moratal, Lloret, Julve, and Garcia-España) first focused on the determination of stability constants of metal complexes in solution with violurate (a very strong field ligand), catechol, porphyrins, and Schiff base ligands. The techniques used were potentiometry and spectrophotometry. A few years later, a Spanish governmental program allowed talented young Spanish scientists to visit abroad as postdoctoral fellows. With the support of Professor Faus, Miguel Julve was the first to seize this opportunity and he spent two years in France in the laboratory of Prof. Oliver Kahn at Orsay where he worked closely with M. Verdaguer. Others (Moratal, Garcia-España) visited the groups of Bertini and Paoletti in Florence (toward bioinorganic chemistry and supramolecular chemistry) and found their own way. This national and European opening-up transformed deeply Faus's group and beyond, the Inorganic Chemistry Department. It brought new blood, modernized and diversified the themes, and opened the way to publications in European and American journals. From then, the programmed postdoctoral stays of members of Faus's group in France (Orsay) (M. Julve then F. Lloret working with Y. Journaux and later, J. A. Real working with J. Zarembowitch on spin cross-over) and their reincorporation in the mother group in Valencia allowed achievement of a solid background in solidstate coordination chemistry, in structural studies and in magnetism. Furthermore, some of the systems investigated by Professor Faus underwent spin changes [complexes of Co(II) and Fe(II) with violurate and its alkyl derivatives] and led him to be interested in Molecular Magnetism. New equipment, a variable-temperature Faraday balance permitted to carry out this new research avenue at home, always keeping and reinforcing the collaboration with foreign teams. Along the years, the scientific partnership transformed into reciprocal esteem and friendship. The group is located nowadays in the premises of the Institute of Molecular Science of Valencia and is constituted by two Full Professors (Miguel Julve and Francesc Lloret), one Assistant Professor (Isabel Castro), a lecturer (Salah Eddine-Stiriba), two permanent researchers (Joan Cano and Rafael Ruiz), four hired researchers [Emilio Pardo and F. José Martínez (Ramón and Cajal positions), Marta Viciano (Juan de la Cierva position), and Luminita Toma (Marie Skłodowska-Curie, H2020, position] and one technician (F. Nicolás Moliner). Professor Faus supervised a good number of Ph.D. Theses. Most of his doctoral students occupy permanent positions in public institutions, beyond the coordination chemistry group itself: Enrique García-España and Miguel Mollar are Full Professors at the University of Valencia and Universidad Politécnica de Valencia, respectively; Hermás Jiménez is an Assistant Professor at the University of Valencia; Maria Luisa Calatayud is Full Professor in a secondary public school; abroad, Raúl Chiozzone, Ricardo González, and Alicia Cuevas are Assistant Professors at the Universidad de la República, Montevideo, Uruguay. Professor Faus promoted international collaborations of his team with national and foreign Institutions. The international exchange was especially strong and fruitful in the framework of the European Union where the Coordination Chemistry group was involved as a partner in several bilateral Spanish-French "Picasso" integrated actions (1990,1991,1993) with teams in France (Paris and Orsay) and in Spain (Valencia and Barcelona) and then in European networks. This collaboration, led at the beginning by Professors Faus and M. Verdaguer and then by their co-workers, followed the initial interest of Professor Faus for combined solution and solid-state studies and was dedicated to metal complexes with oxalate, oximes, functionalized oxamate/oxamidate derivatives, 2,2′-bipyrimidine, squarate, and croconate as ligands. The choice of these ligands was mainly based on both their great versatility as bridges between transition metals and their potential ability to mediate exchange interactions between the bridged paramagnetic centers. This management and scientific strategy had many positive consequences: (i) beautiful scientific results (about 150 articles) on original chemical systems published in prestigious journals (J. Am. Chem. Soc., Angewandte Chemie, Inorg. Chem., Dalton Transactions, etc.); (ii) a long-term exchange program for training of doctoral and postdoctoral fellows in the 1990s and later (I. Castro is now Assistant Professor in Valencia and R. Lescouëzec is Full Professor in Paris); (iii) close association of the Coordination Chemistry group in the European networks launched in the frame of 4th-6th PCRD. Other very fruitful international collaborations were established later (from 1999), on another Professor Faus's favorite topic, the chemistry and the magnetic properties of rhenium(IV), a paramagnetic and highly anisotropic metal ion. The collaboration involved Prof. Carlos Kremer and his co-workers from the Universidad de la República (Uruguay) and also the Italian group of Professors G. De Munno and D. Armentano. One can state that Professor Faus, after the studies first published by the Polish and Russian schools on halogenorhenates(IV), established in a very creative way a new coordination chemistry of Re(IV) to exploit the

remarkable magnetic anisotropy of this ion. Three PhD co-shared theses issued from the Uruguayan collaboration on Re(IV) together with 37 published articles with Professor Faus as co-author. The intensity and the quality of this research, up to a recent Nature Communications paper, pushed the Valencia group to the first world rank for research on Re(IV) coordination chemistry. These achievements were summarized in a recent review. Professor Faus was distinguished with the Gascó Oliag Medal on 14 November 2009 by the Colegio de Químicos de la Comunitat Valenciana for his brilliant teaching and high-level research as well as his continuous collaboration with the Colegio de Químicos.

The man and the friend

We would like to conclude this tribute to evoke more personal memories. Juan Faus is a quiet, modest, and friendly man, always ready, after work, to enjoy life with friends (Figure 2). We cannot remember him in the university dressed without his clean white over-garment and his friendly teasing smile. Juan Faus is a man who is always ready to face adversity and find the right solutions. He enjoys life, likes his town (Valencia), its paella, and quiet boat cruises on the Albufera. He liked to share his lunch in the university restaurant with colleagues and friends and, open-minded, he was not the last to participate in vivid discussions where the world is passionately rebuilt every day on firmer and more rational bases. We are sure that all his collaborators and colleagues join us in thanking Prof. Faus for his invaluable contributions to the development of Coordination Chemistry in Spain and worldwide. We wish him all the best for his retirement.

To conclude, we are convinced that this special issue will contribute to the recognition of his scientific legacy and his high-quality work which exerts a strong influence not only on the past generations of chemists, but also on the present and future ones.