Yohann Meynadier

AERODYNAMIC TOOL FOR PHONOLOGY OF VOICING

Keywords: voicing, whisper, subglottal pressure, intraoral pressure, glottis, vocal effort, French

The paper addresses the question of the phonetic implementation of phonological voicing in French. It is investigated by means of aerodynamic measures made at the subglottal, glottal and supraglottal stages of the production of fricatives in modal voice and in soft and loud whisper for one speaker. The results show that the [±voice] feature is systematically associated only with the categorical constrictions of the glottis, even without vocal fold vibration.

INTRODUCTION

The voicing contrast meets different phonological feature specifications across languages and theories, e.g. voice, fortis/lenis, tense/lax, aspiration, spread glottis, glottal constriction, see e.g. [START_REF] Fuchs | Articulatory correlates of the voicing contrast in alveolar obstruent production in German[END_REF][START_REF] Keating | Phonetic and phonological representation of stop consonant voicing[END_REF]. The question of their association with identifiable phonetic properties is also largely discussed. Our study deals with some points relative to this large question in French. How is the [±voice] feature phonetically implemented? Is it associated with subglottal, glottal and/or supraglottal components? Is voicing defined by vocal fold vibration?

Aerodynamics provides a powerful tool to study synchronously all components of the speech production system and to test phonological proposals by empirical experiments, e.g. [START_REF] Ladefoged | Investigating phonation types in different languages[END_REF][START_REF] Ohala | Aerodynamics of phonology[END_REF]. Aerodynamic studies globally report that intraoral pressure (Pio) in various languages reflects the [±voice] features of obstruantes, inter alia [START_REF] Butcher | Intraoral pressure as an independent parameter in oral stop contrasts[END_REF][START_REF] Collier | Voicing in intervocalic stops and fricatives in Dutch[END_REF][START_REF] Demolin | Direct and indirect measurements of subglottic pressure[END_REF][START_REF] Fischer-Jørgensen | PTK et BDG français en position intervocalique accentuée[END_REF][START_REF] Malécot | An experimental study of force of articulation[END_REF][START_REF] Meynadier | Aerodynamic and durational cues of phonological voicing in whisper[END_REF][START_REF] Netsell | Subglottal and intraoral air pressures during the intervocalic contrast of /t/ and /d[END_REF][START_REF] Slis | Articulatory measurements on voiced, voiceless and nasal consonants[END_REF], but see e.g. [START_REF] Lisker | Supraglottal Air Pressure in the Production of English Stops[END_REF]. As Pio must be lower than the subglottal pressure (Psg) to reach the mechanical vibration of the folds, Pio is viewed as an essential control parameter of voicing [START_REF] Ohala | Accommodation to the aerodynamic voicing constraint and its phonological relevance[END_REF].

But Pio is a somewhat ambiguous phonetic correlate of voicing, because its value depends on various mechanisms taking place at different levels of the speech production system: (i) at a subglottal level as function of the expiratory effort; (ii) at a glottal level by the laryngeal configuration; (iii) at a surpraglottal level by various articulatory mechanisms [START_REF] Ohala | Accommodation to the aerodynamic voicing constraint and its phonological relevance[END_REF]. Its ambiguity results in different proposals concerning the physical level of the phonetic implementation of the voicing contrast in production. For example, based on laryngectomized speech, Kobayashi [START_REF] Kobayashi | Intraoral air pressure variations for consonantal voicing distinction in speech without larynges[END_REF] thus suggests that Pio is phoneme specific as function of voicing, but not the glottis configuration itself. Conversely, based on Pio during whispered speech in French, Meynadier and Gaydina [START_REF] Meynadier | Aerodynamic and durational cues of phonological voicing in whisper[END_REF] concluded that Pio depends mainly on the glottal configuration directly associated with the voicing feature, as Netsell [START_REF] Netsell | Subglottal and intraoral air pressures during the intervocalic contrast of /t/ and /d[END_REF] and Slis [START_REF] Slis | Articulatory measurements on voiced, voiceless and nasal consonants[END_REF].

To confirm the last proposal, in this study, the aerodynamic production of the voicing contrast in whisper is focused on French. Whispered speech is characterised by an absence of vocal fold adduction, hence of their periodic vibration. Despite this lack, the few studies which have been made report that the perception of voicing contrasts in various languages is quite well preserved in whisper [START_REF] Dannenbring | Perceptual discrimination of whispered phoneme pairs[END_REF][START_REF] Higashikawa | Perceptual, acoustical and aerodynamic study of whispering[END_REF][START_REF] Mills | Speech motor control variables in the production of voicing contrasts and emphatic accent[END_REF][START_REF] Munro | Perception of voicing in whispered stops[END_REF][START_REF] Tartter | What's in a whisper?[END_REF], French included [START_REF] Fux | Vers un système indiquant la distance d'un locuteur par transformation de sa voix[END_REF][START_REF] Meynadier | Duration as perceptual voicing cue in whisper[END_REF][START_REF] Vercherand | Production et perception de la parole chuchotée en français: analyse segmentale et prosodique[END_REF]. Concerning the voicing production in whisper, the Pio results of the few existing studies are equivocal (see §4).

To clear the Pio ambiguity and to assess which manoeuvres at which level of speech production are responsible for the voicing contrast, we record aerodynamic parameters at the successive stages of the air pathway in modal and whispered speech. Therefore the subglottal expiratory force is estimated by Psg, the size of the laryngeal opening by the glottal resistance to lung airflow, the vocal tract adjustments by Pio and the size articulatory constriction by the supraglottal resistance to the phonatory airflow. The fricatives are focused here, because simultaneous aerodynamic measures at all speech production stages are possible.

METHOD

Corpus

One French speaker (the author) read at normal speaking rate a randomized list of 6 isolated nonsense words in modal ('voiced phonation'), whispered ('voiceless phonation at the ear of a listener') and loud whispered ('voiceless phonation to a 2 meter remote listener') voices. Each list was alternatively read 5 times in each phonation mode.

The 6 fricatives /f-v/, /s-z/ and /ʃ-ʒ/ are the target phonemes inside non-sense words with the pattern /eC [α voice] eC [-α voice] e/. The acoustic segmentation of consonants was processed on the oscillogram only. The beginning and the end of the fricatives was located at points of change in the signal waveform during the transition towards and from the vowel.

Aerodynamics

The acoustic signal, the oral airflow (Oaf), the subglottal (Psg) and supraglottal (Pio) pressures were recorded synchronously with the EVA station [START_REF] Ghio | Evaluation of the acoustic and aerodynamic constraints of a pneumotachograph for speech and voice studies[END_REF]. Oaf was captured by a silicon mask covering the mouth. Pio was recorded with a catheter (internal diameter: 2 mm) introduced through the nasal tract to just below the uvula. Psg was measured via a tracheal catheter (i.d.: 1.3 mm) punctured between the cricoïd cartilage and the first tracheal ring. Aerodynamic measurements (in l/s and hPa) were carried out with the free Phonedit software [29].

The airflow and air pressure y values were automatically extracted at the peak of Pio during the fricative, i.e. the Pio maximum and, Psg and Oaf y values at this x time point. The y values were normalized by subtracting the minimum y value reached after the end of each word, that is at the x time point of the first zero-crossing of Psg. The post-calibration allows us to exclude the local upsteps, down-steps or declination of the signals.

From these measures, two aerodynamic parameters (in hPa/l /s ) were computed: (1) the resistance of the glottis to lung airflow; (2) the resistance of the vocal tract constriction to airflow. [START_REF] Butcher | Intraoral pressure as an independent parameter in oral stop contrasts[END_REF] Oaf

Pio Psg Rglo - = (2) Oaf Patm Pio Rsup - =
where Patm equals to 0 as a fixed constant of atmospheric pressure.

The lack of glottal vibration of the whispered fricatives was checked by the EGG signal, synchronously recorded with the aerodynamic data.

Statistics

The statistical analyses were simple linear regressions, two-way ANOVAs and post-hoc Fisher tests on these aerodynamic measures and parameters (N = 3 consonants * 2 positions * 2 voicing * 3 phonation conditions * 5 repetitions = 178; one /f/ and one /v/ excluded).

The C 1 or C 2 position, the place of articulation and the repetitions are random factors. Phonation (modal vs. whisper vs. loud whisper), and Voicing ([+voice] vs. [-voice]) are the independent factors (significant levels: *<.05; **<.01; ***<.0001).

RESULTS

Simple linear regressions were preliminarily carried out to assess the redundancy of measures and parameters.

The aerodynamic measures (Psg, Pio and Oaf), used to compute the two parameters of airflow resistance, appears largely independent of each other. Significant R² values (p<.05 at least) vary from .055 to .289 among the 3 phonation conditions. The high correlation observed between Pio and Psg (.496, pooled conditions) essentially reflects the categorical change in pressure due to the vocal effort increasing from whisper to modal voice to loud whisper. In split conditions, it's lost.

Only poor correlations between the aerodynamic parameters (Psg, Rglo and Rsup) emerge: .079 ≤ R² ≥ .423. The higher correlation between Psg and Rglo seems here to capture a categorical effect of the consonant voicing. When the regression is computed separately for voiced (R²=.197; p=.014) and voiceless (R²=.183; p=.0185) fricatives, it disappears. It could be the sign of the main similar impact of the adduction/abduction of the vocal folds on the amplitude of Psg and of Rglo.

So, the linear regression analyses show that only few partial and weak correlations link the aerodynamic parameters. When some correlations exsit, they reflect in fact more categorical effects relative to the different conditions of phonation, the vocal effort or the consonant voicing. It is rather clear that these aerodynamic parameters are quite independent. Therefore, they capture specific aerodynamic mechanisms involved in the different stages of the production of fricatives: subglottal (Psg) vs. glottal (Rglo) vs. supraglottal (Rsup).

Vocal effort (Psg)

The ANOVAs report a main significant effect of Phonation [F(2,172)=1060.52; p<.0001] and of Voicing [F(1,172)=33.655; p<.0001] on Psg, but no significant Phonation*Voicing interaction. Comparatively, the significant difference due to Voicing is limited to 0.5-1 hPa, as already measured in French [START_REF] Demolin | Direct and indirect measurements of subglottic pressure[END_REF][START_REF] Meynadier | Aerodynamic and durational cues of phonological voicing in whisper[END_REF] or in English [START_REF] Netsell | Subglottal and intraoral air pressures during the intervocalic contrast of /t/ and /d[END_REF], and simulated by Ohala [START_REF] Ohala | A mathematical model of speech aerodynamics[END_REF]. But, it is systematic over the 3 conditions of phonation. With or without vocal fold vibration, Psg is higher for [+voice] than [-voice] fricatives. This fine difference may be a mechanical and passive consequence of a stronger resistance of the closer glottis for [+voice] fricatives. Hence, even if the glottis remains open in whisper, a narrower glottal constriction for /v z Z/ could explain the weak but constant increase of Psg.

Here, the expiratory force doesn't seem to be controlled by the phonological voicing specification of the segment, but to be a means of controlling the global level of the acoustic energy of the voice, as function of phonation modes and planned intensity.

Glottal resistance (Rglo)

Phonation

[F(2,172)=12.018; p<.0001] and interaction Phonation*Voicing [F(2,172)=15.805; p<.0001] have significant effects on Rglo. But, Figure 2 shows clearly that the effects are only due to the specific adduction of vocal folds used to produce the vibration source of [+voice] fricatives in modal voice. Otherwise, the glottal resistance remains similar in whisper whatever the vocal effort. In loud whisper, it isn't mainly supported or controlled by the laryngeal system as glottal tension or configuration, but by the expiratory effort (Psg). As a quite similar Psg was observed as function of Voicing ( §3.1), the aerodynamic resistance of the glottis may decrease with its degree of opening (and/or of the laryngeal constriction). Therefore, the [-voice] specification for voiceless fricatives seems to be phonetically produced with the same glottis opening, whatever the phonation mode and the vocal effort. But mostly, even if the vibration of the vocal folds (by their adduction) is prohibited, as in whispered speech, the phonological [+voice] specification of fricatives seems to lead to a glottal constriction, for both vocal efforts produced. So, this result confirms that the phonological voicing is physiologically produced by different degrees of constriction of the glottis or of the laryngeal sphincter.

Supraglottal resistance (Rsup)

A significant effect on Rsup is only reported for Phonation [F(2,172)=25.414; p<.0001]. The fricatives produced in loud whisper show a greater resistance of articulatory constriction to airflow. This could result from the highest Psg ( §3.1) plus a quite open glottis ( §3.2). Concerning Voicing, no substantial differences can be observed, despite a tenuous increase of Rsup from [+voice] to [-voice] fricatives for all phonation conditions. So, the results may support an absence of a specific control of the [±voice] specification at the articulatory constriction. Concerning the differences between [+voice] and [-voice] fricatives, Pio (Figures 4 and6) and Oaf (Figures 5 and6) seem to be mainly echoes of Rglo.

Pio and Oaf as unstable echoes of voicing

When ΔRglo is high, as in modal voice, Oaf and Pio reflect the voicing contrast. When ΔRglo is low, as in whisper, these echoes are very weak and/or variable. Pio and Oaf may be seen as passive *** ** *** responses to pneumo-phonatory configurations. This interpretation is also supported by the parallel differences of Pio and Psg across the 3 modes of phonation (Figure 6). As a matter of fact, Pio and Oaf are the less consistent aerodynamic correlates of the voicing contrast across the vocal conditions.

DISCUSSION

The summary of the phonological voicing effects on fricatives at the successive stages of speech production (Figure 6) shows that the relationships of aerodynamic parameters along the airway confirm that the implementation of the [±voice] feature states only at the glottis level. It does not seem to take place above or below the larynx in phonation with or without vocal fold vibration. First, as the air pressure control above the vocal folds is essential for voicing, the well-known Aerodynamic Voicing Constraint [START_REF] Ohala | Accommodation to the aerodynamic voicing constraint and its phonological relevance[END_REF] may also be involved in whisper, in French [START_REF] Meynadier | Aerodynamic and durational cues of phonological voicing in whisper[END_REF]. Many mechanisms inside the vocal tract can support or strengthen it, see e.g. [START_REF] Kobayashi | Intraoral air pressure variations for consonantal voicing distinction in speech without larynges[END_REF][START_REF] Ohala | Accommodation to the aerodynamic voicing constraint and its phonological relevance[END_REF]. A main supraglottal control factor of Pio is the size of the articulatory constriction for which the supraglottal resistance to phonatory airflow (Rsup) can be an indirect measure. In our study, non-discriminatory Rsup data rules out the use of the articulatory constriction as a systematic mechanism to support the voicing contrast. The Pio value itself is also a result of other kinds of active or passive supraglottal manoeuvres or adjustments according to voicing. But here again, no consistent variation of Pio data allow us to support such systematic mechanisms in whisper. Pio seems only a variable echo of the glottal and subglottal components. It is confirmed by numerous equivocal findings on Pio values as function of voicing in whisper in Japanese, [START_REF] Higashikawa | Perceptual, acoustical and aerodynamic study of whispering[END_REF] vs. [START_REF] Soda | Intraoral pressure change in Japanese consonants[END_REF], or in English, [START_REF] Klich | Effects of speech level and vowel context on intraoral air pressure in vocal and whispered speech[END_REF] and [START_REF] Netsell | Subglottal and intraoral air pressures during the intervocalic contrast of /t/ and /d[END_REF] vs. [START_REF] Murry | Peak intraoral pressures in whispered stop consonants[END_REF] vs. [START_REF] Weismer | Segmental gestures at the laryngeal level in whispered speech: evidence from an aerodynamic study[END_REF].

The air pressure control below the vocal folds is also essential for voicing. In our study, the small differences of Psg may be understood as only passive mechanical echoes of the degree of glottal opening. This is supported by previous studies on English [START_REF] Netsell | Subglottal and intraoral air pressures during the intervocalic contrast of /t/ and /d[END_REF] and on Dutch [START_REF] Slis | Articulatory measurements on voiced, voiceless and nasal consonants[END_REF] in modal voice and in whisper. So, the expiratory effort doesn't seem to be actively adjusted phoneme by phoneme.

Finally, the alternative proposal considers that the [±voice] contrast is essentially controlled by the states of the glottis alone, e.g. [START_REF] Catford | Fundamental problems in phonetics[END_REF][START_REF] Laver | Principles of phonetics[END_REF], see [START_REF] Mills | Speech motor control variables in the production of voicing contrasts and emphatic accent[END_REF] for a review. The resistance to expiratory airflow is an aerodynamic index of the glottis size. Our Rglo data show clearly that a stronger resistance of the glottis is systematically produced for [+voice] even in whisper, and whatever the pneumo-phonatory effort. Conversely, [-voice] is always realised with nondistinctive Rglo values, hence a stable wide glottal configuration. Even without complete adduction and vibration of the vocal folds, as in whispered speech, the glottis is closer for [+voice] fricatives and wider for [-voice] ones. These results are supported by the similar aerodynamic studies on whisper by Netsell [START_REF] Netsell | Subglottal and intraoral air pressures during the intervocalic contrast of /t/ and /d[END_REF] in English and by Slis [START_REF] Slis | Articulatory measurements on voiced, voiceless and nasal consonants[END_REF] in Dutch. They are also consistent with Malécot and Peebles' single electrophotoglottographic observation [START_REF] Meynadier | Duration as perceptual voicing cue in whisper[END_REF], and the only direct videofibroscopic studies (that I know of) in French by Crevier-Buchman et al. [START_REF] Dannenbring | Perceptual discrimination of whispered phoneme pairs[END_REF] and in English by Mills [START_REF] Mills | Speech motor control variables in the production of voicing contrasts and emphatic accent[END_REF] on whispered speech.

As an outcome on the phonology of French, the [+voice] feature may be associated with a narrow constriction of the glottis, and/or the laryngeal sphincter, to produce the acoustic source, periodic or noisy. Its phonetic correlate, such as the vocal fold vibration, may only be determined by the mode of phonation and not the phonological representation.

Figure 1 :

 1 Figure 1: Psg as function of Phonation/Voicing (confident interval of 95% in bars; * for significant levels for Voicing; idem in the next figures)

Figure 2 :

 2 Figure 2: Rglo as function of Phonation/Voicing

Figure 3 :

 3 Figure 3: Rsup as function of Phonation/Voicing

Phonation

  and Voicing have significant effects on Pio [F(2,172)=95.169; p<.0001 and F(1,172)= 11.405; p=.0009], and on Oaf [F(2,172)=68.86; p<.0001 and F(1,172)= 22.71; p<.0001]. An interaction is reported only for Oaf due to the large increase of airflow from the [+voice] to [-voice] fricatives only in modal voice.

Figure 4 :

 4 Figure 4: Pio as function of Phonation/Voicing

Figure 5 :Figure 6 :

 56 Figure 5: Oaf as function of Phonation/Voicing


Kenneth S Olson¹

Yohann Meynadier²
email: yohann.meynadier@lpl-aix.fr

ON MEDUMBA BILABIAL TRILLS AND VOWELS

Keywords: bilabial trill, vowel posture, lip position, Niger-Congo, Narrow Grassfields

The Medumba consonant inventory includes plain and prenasalized bilabial trills /ʙ, mʙ/, which contrast with bilabial stops. The trills occur most often before the central vowels / ə/, while they are not attested before /u/.

The central vowel / / has a vowel posture that is particularly conducive to trilling of the lips: it does not form a circular opening, the corners of the mouth are drawn slightly apart, the lips are tensed, particularly at the corners of the mouth, and there is a narrow aperture between the lips. This suggests that it is close lip aperture of the following vowelrather than rounding-that provides the most conducive environment for bilabial trill production.

INTRODUCTION

This paper is a preliminary assessment of the articulation and phonology of bilabial trills and vowels in Medumba (ISO 639-3 code byv), a Narrow Grassfields language spoken in and around the town of Bangangte in Cameroon.

Bilabial trills (excluding interjections) are found predominantly in Central Africa, Papua New Guinea, Vanuatu, China, and Brazil [START_REF] Keating | A cross-linguistic overview of bilabial trills[END_REF]. In Narrow Grassfields, they are attested in Babanki, Kom, Kuk, Medumba, Mfumte, Mungaka, Ngwe, and Oku [START_REF] Atchombat | Projet final d'étude phonologique de la langue mambəma[END_REF]4,6,[START_REF] Hyman | How to study a tone language, with exemplification from Oku (Grassfields Bantu, Cameroon)[END_REF][START_REF] Keating | A cross-linguistic overview of bilabial trills[END_REF][START_REF] Mclean | [END_REF][START_REF] Njika | A phonology of Nweh and a proposed orthography[END_REF]19].

METHODOLOGY

For this paper, we worked with one speaker of Medumba, an educated female speaker about 35 years of age. We recorded a list of 120 words spoken in isolation, the ten vowels in isolation /i e ɛ ə a u o ɔ ɒ/, and a few selected phrases. The words were chosen in order to include bilabial trill data, as well as examples of each vowel. Data were collected from two sources [5,[START_REF] Nana | Visual dictionary Bamiléké-M d (French -English)[END_REF], and they were verified by the subject. The words presented to the subject were mostly provided in the orthography developed by CEPOM (Centre d'Étude et de Promotion des Oeuvres Mèhdúmbà), a system with which the subject was familiar.

During the recording, the first author produced the gloss for each word in English, and then the speaker produced the word in Medumba twice.

The entire set of data was recorded in audio at 48k, 24-bit, using a Zoom H2 recorder, and saved as WAV files. A video was made of the bilabial trill data and the vowels in isolation. We used a Canon Vixia HF-M30 HD camcorder, set at 30 fps, progressive scan). Audio was captured during the video recording using an Audio Technica ATR3350 lapel microphone. The recording took place at the C.V. STARR-Middlebury School in Yaoundé.

SAMPLE WORDS

In [START_REF] Anderson | Phonological characteristics of Eastern Grassfields languages[END_REF] we provide a sample of monomorphemic words containing bilabial trills. The data are in the CEPOM orthography [START_REF] Nana | Visual dictionary Bamiléké-M d (French -English)[END_REF] and IPA [START_REF] Ipa | Handbook of the International Phonetic Association[END_REF], the latter transcription based on our recording.

(

PHONEMIC STATUS

We found two minimal pairs between /b/ and /ʙ/ in Medumba, as shown in (2) [START_REF] Voorhoeve | Contes Bamileke[END_REF]: It is possible that the bilabial trill could be interpreted as patterning as a |bw| sequence in the phonology, e.g. as McKee [START_REF] Mckee | The interpretation of consonants with semi-vowel release in Meje (Zaire) stems[END_REF] has done for Mangbetu. Note that in the CEPOM orthography the trill is usually written <bw>. More research on interpretation and contrast is needed.

ARTICULATION

Prenasalization

In Medumba, bilabial trills are initiated by a period of bilabial closure. The closure can be entirely oral (a "plain" ila ial trill), or it can consist of a nasal closure followed by a brief oral closure (a "prenasalized" ila ial trill). The phonological status of the nasal closure is somewhat unclear. Voorhoeve [START_REF] Voorhoeve | Contes Bamileke[END_REF] treats it as a prefix, and marks tone on it (always low in his data). On the other hand, Nana et al. [START_REF] Nana | Visual dictionary Bamiléké-M d (French -English)[END_REF] do not mark tone and make no mention of the nasal closure's status as a prefix. Prenasalization can occur word-medially in syllable-initial position, although this appears to involve cases of compounding.

The Narrow Grassfields languages in general have syllabic nasal prefixes which have been reduced from earlier whole open syllable prefixes [START_REF] Anderson | Phonological characteristics of Eastern Grassfields languages[END_REF]. In some languages (e.g. Limbum), these nasals have lost their syllabicity resulting in prenasalized consonants.

Measurements for seven prenasalized trills and eight plain trills are shown in Table 1. The duration of the oral portion of bilabial closure is given in the first column, and the duration of the period in the trill is given in the second column. Each token has two trill periods.

When the nasal closure is present, the oral closure is short, about 33 ms in duration. When prenasalization is not present, the oral closure is significantly longer, averaging about 156 ms. (This duration may be due to careful speech style.)

Trilling

On average, there are two trill periods following the oral closure. Following Maddieson [START_REF] Maddieson | Aerodynamic constraints on sound change: The case of bilabial trills[END_REF], we define the trill period as starting immediately at the release of the oral closure and ending at the completion of the next short closure, when there is a sudden rise in amplitude. A third partial lip closure is often observed corresponding to a partial reduction in amplitude.

The second column in Table 1 shows the duration of trill periods for /mʙ/ and /ʙ/. The mean duration of the trill period was slightly longer for /mʙ/ than for /ʙ/, i.e. 42.6 ms vs. 38.7 ms. Further work is necessary to determine if this distinction is consistent across speakers of the language.

The voicing bar is present throughout the articulation of the bilabial trill.

In line ith Maddieson's o servations, trilling occasionally fails. Figure 1 shows waveforms and spectrograms for three tokens: [mʙ ə ] 'fire', [bβ ŋə ] 'poverty', and [ ò] 't o'. A trill [ʙ] was expected in the second word, but it was realized as [bβ], with friction heard and aperiodic noise visible in the spectrogram.

PHONOTACTICS

The majority of bilabial trills in Medumba occur before the central vowels / / and /ə/. In our data they also occur before /i/ and /o/, and they have been attested by other researchers before /ɔ/ [5]. We have found no cases of bilabial trills before the other vowels in Medumba. Of interest is its absence before /u/, since this is thought to be the most common environment for the genesis of /ʙ/ [START_REF] Ladefoged | Sounds of the world's languages[END_REF][START_REF] Maddieson | Aerodynamic constraints on sound change: The case of bilabial trills[END_REF].

Figure 2 shows an F1 vs. F2 plot of the ten vowels in Medumba for our speaker. There were four tokens of each vowel, from words where the vowel followed a bilabial consonant, and no nasal consonant was adjacent. The vowels were measured in PRAAT by identifying the midpoint of the steady state of the vowel on a spectrogram, ensuring congruency between the formant bands on the spectrogram and the LPC values, and then extracting the LPC values. The vowel / / is clearly central according to the vowel plot. However, it does not fit standard categories for vowel posture. The lips do not form a circular opening, and the corners of the mouth are not drawn together, as occurs in both protruded and compressed rounding postures.

We asked the speaker to produce the vowel / / in isolation. In her articulation of the sound, she began by manoeuvring the lips in the direction of a protruded lip posture. However, she then pulled the corners of the lips away from each other and brought the upper and lower lips close to each other so that there was only a narrow slit opening between them. The final posture thus involves some labial tension, particularly at the corners of the mouth, and a small amount of protrusion.

Figure 3 compares the positioning of the mouth in the articulation of the vowels /i u/ spoken in isolation at the point of maximal gesture of the lips. Note particularly the close lip aperture of / / in comparison to /i/ and the lack of rounding of / / in comparison to /u/.

DISCUSSION

Ladefoged & Maddieson [START_REF] Ladefoged | Sounds of the world's languages[END_REF] o serve that " ila ial trills in linguistic use are almost always released into high rounded vowels" (which are usually back) and that bilabial trills nearly always arise historically from a sequence such as *mbu.

The Medumba case suggests that these observations may need to be fine-tuned in two respects: backness and rounding. First is the preponderance of bilabial trills before central vowels rather than back ones. In all of the Cameroonian languages mentioned above, most occurrences of bilabial trills are before central vowels. Similar cases occur elsewhere: In both Wari' in Brazil [START_REF] Maceachern | Wari' phonetic structures[END_REF] and Avava in Vanuatu [START_REF] Crowley | The Avava language of Central Malakula (Vanuatu)[END_REF], bilabial trills occur before the central vowel [ ] instead of [u].

Second, many discussions of lip position make a distinction between compressed and protruded vowels, both of which are generally treated as characteristics of lip rounding (e.g. [START_REF] Ladefoged | Sounds of the world's languages[END_REF]). In both cases, the corners of the lips are drawn together. However, as e've noted for the Medumba vowel / /, the corners of the lips are drawn apart instead. As a result, the Medumba / / cannot be construed as rounded, but given the labial tension involved in its articulation, it cannot be construed as involving relaxed lips either.

One possible approach would be to follow Laver [START_REF] Laver | The phonetic description of voice quality[END_REF] in employing three independent lip position parameters: protrusion (involving a forward horizontal gesture of the lips), horizontal expansion or constriction of the interlabial space (i.e. the space between the lips), and vertical expansion or constriction of the interlabial space. In this view, the Medumba / / involves horizontal expansion as the corners of the lips are drawn apart, vertical compression resulting in a close lip aperture, and perhaps a small amount of protrusion. Okada [START_REF] Okada | [END_REF] implicitly takes this approach when he considers the Japanese /u/ to be unrounded and yet have compressed lips.

CONCLUSION

The bilabial trills in Medumba display some characteristics similar to those previously described in the literature: initiation from a closed position, a short oral closure period when prenasalized, an average of two trill periods per token, an average duration for a trill period of about 40 ms, and occasional failure of trilling that results in friction.

The distribution of bilabial trills before vowels in Medumba suggests a refinement in our understanding of what triggers them: a following central vowel with a close lip aperture due to vertical compression (but no rounding) may be a more common environment than previously thought. We suggest that future work on bilabial trills should investigate this environment further.

  attested before /o/, e.g. [mʙ ə ] 'fire' vs. [l m ò] 'lamp'. We have not found contrast between [b] vs. [ʙ] before /i/ or / /, which suggests a partial neutralization of contrast in these environments.

Figure 1 :

 1 Figure 1: Waveforms and spectrograms of [mʙ ə ] 'fire', [ β ŋə ] 'poverty', and [ ò] 't o'.

Figure 2 :

 2 Figure 2: F1 vs. F2 plot of the vowels in Medumba.

Figure 3 :

 3 Figure 3: The vowels /i, , u/ spoken in isolation.

Table 1 :

 1 Duration of initial oral closure and period in trill (two trill periods for each token).

		Duration of	Duration of
		oral closure	period in trill
	mʙ	33.1 (n=7) 42.6 (n=14)
	s.d. 4.5	5.2
	ʙ	156 (n=8)	38.7 (n=16)
	s.d. 14.1	4.6

ACKNOWLEDGMENTS

We wish to thank Dr. Ariane Ngabeu for sharing her language with us, the C.V. STARR-Middlebury School in Yaoundé for recording space, and SIL International for funding.


To build reliable avionic applications, we interconnect Integrated Modular Avionics (IMA) architectures with Time-Triggered Ethernet (TT-Ethernet). These systems have direct impacts on human lives where the failure is unacceptable. Therefore, verification is an important issue to ensure the safety and the performance of the system. The integration of IMA architectures is a very complex and challenging engineering task. To cope with complexity and to perform verification, a model-based approach, which endows engineering teams with a methodology and an adequate tooling is of a paramount importance. To design IMA architectures interconnected with TT-Ethernet, we have proposed an extension of the AADL language in previous works. In this paper, we present a simulation-based verification of our extension and show how it can be simulated using a discrete event simulation environment called DEVS Suite. The main advantage of this technique is to perform cycle-accurate simulation of the complex avionics systems, which cannot be undertaken by model checking techniques. The tool demonstration video is available at: http://youtu.be/hwgN-a-7rzw.

Simulation-Based Verification of Avionic Systems

Deployed on IMA Architectures Tiyam Robati * , Amine El Kouhen † , Abdelouahed Gherbi * , John Mullins ‡

I. INTRODUCTION

Avionic systems are safety-critical systems which should meet strict safety, reliability and performance requirements and where no deviation is admissible. To build such systems, the Integrated Modular Avionics (IMA) architecture is an alternative of federated architectures, where each function is designed and deployed to use its exclusive resources. The IMA architectures are distributed using a communication infrastructure, which should also be able to meet the same level of safety and performance requirements.

For this, Time-Triggered Ethernet permeates a system with robust fault detection characteristics across a wide range of fault hypotheses. This is rewarded with the schedule of TT-Ethernet, because all message transmissions must occur according to the schedule, therefore any deviations (e.g. transmission at the incorrect time) are easily detected.

The advantages of this infrastructure are numerous. The combination of IMA and TT-Ethernet enables the error isolation provided at the level of the modules through the partitioning and at the level of the network using different data traffics. Moreover, TT-Ethernet enable the safe integration of data traffics with different performance and reliability requirements.

The focus of this work is on the verification of avionic systems deployed on IMA architectures and inteconnected with TT-Ethernet. These systems are complex and very challenging. In order to control the complexity of such systems, we proposed in [START_REF] Robati | An Extension for AADL to Model Mixed-Criticality Avionic Systems Deployed on IMA architectures with TTEthernet[END_REF], a model-based approach for IMA architectures interconnected with TT-Ethernet, using AADL modeling language.

To verify our models, we chose a simulation-based approach, which is the widely-used technique to ensure the correctness of a system [START_REF] Hessam | EMF-DEVS modeling[END_REF], [START_REF] Bolduc | Generation of DEVS Modeling and Simulation Environment[END_REF]. This approach allows to design the behavior of a dynamic system by describing its reaction to external stimuli, such as the function of time [START_REF] Bolduc | Generation of DEVS Modeling and Simulation Environment[END_REF].

In order to develop a simulation for our systems, one way is to move from an informal conceptual space to an abstract mathematical specifications [START_REF] Hessam | EMF-DEVS modeling[END_REF]. The abstract mathematical specification is supported by a Discrete Event Formalism called (DEVS) [START_REF] Bernard | Theory of Modeling and Simulation[END_REF]. This formalism can guarantee that the network is running according to the TT-Ethernet specifications by ensuring its scheduling properties. Toward this goal, we take advantages of model transformations, by transforming an AADL model which represents an IMA architectures interconnected with TT-Ethernet to a model conformant to DEVS formalism.

II. BACKGROUND

The Integrated Modular Avionics (IMA) architecture is based on resource sharing between functionalities ensuring their isolation in order to prevent any interfaces between them [START_REF] Christopher | Transitioning from federated avionics architectures to integrated modular avionics[END_REF]. Mainly two ARINC standards define IMA systems. The first standard is ARINC 653 [START_REF][END_REF], which focuses on a modular real-time architecture for avionics systems. Each functionality of the system is implemented by one or a set of functions distributed across different modules. A module represents a computing resource hosting many functions. Functions deployed on the same module may have different criticality levels. For safety reasons, the functions must be strictly isolated using partitions. The second standard supports the communication network in IMA. It is defined by either ARINC 664 [START_REF]Aircraft Data Network, Part 7, Avionics[END_REF] or the Time-Triggered Ethernet (TT-Ethernet) [START_REF]Time-Triggered Ethernet[END_REF] depending on the need of predictability.

TT-Ethernet extends the Ethernet IEEE standard 802.3x, in order to support time-triggered services. Therefore, TT-Ethernet establishes a system-wide time base, implemented through a clock synchronisation of the end systems and switches. TT-Ethernet consists of three different types of traffic, which enable supporting distributed avionic applications with different performance and reliability requirements. Namely: Time-Triggered (TT) traffic, Rate-constrained (RC) traffic and Best-Effort (BE) traffic. Each of these traffics has specific characteristics, which are out of the scope of this paper.

AADL is a standard architecture description language (SAE Standard AS5506) [START_REF]Open source aadl tool environment (osatev2)[END_REF]. Which provides an extensible core language with a precise semantics. AADL has been extended to support the modeling of IMA with an Annex for ARINC 653 [START_REF][END_REF]. This extension is one of the reason that we choose AADL as the modeling language in our work. We have presented in previous works an extension for AADL to support the modeling of IMA architectures interconnected using TT-Ethernet. This work supports the networking aspects of IMA architecture, where the conceptual elements ARINC 653 has been presented by ARINC 653 annex [START_REF][END_REF]. In particular, we present a metamodel for the domain of IMA and TT-Ehernet. We provide a concrete textual syntax based on this metamodel, which enables the system engineers to describe a full IMAbased systems using TT-Ethernet.

In order to simulate and analyse an AADL model, some tools have been proposed such as cheddar [17]. This tool cannot support the schedulability of TT-Ethernet nor the specification of specific behaviors of simulated systems. For this, we chose the DEVS formalism [START_REF] Bernard | Multifacetted Modelling and Discrete Event Simulation[END_REF] that provides a rigorous common basis for discrete-event and continuous-time modeling and simulation [START_REF] Nance | The time and state relationships in simulation modeling[END_REF]. It is presented as an extension to Finite State Automata. It allows describing the behavior of system in two levels, which are atomic DEVS and coupled DEVS. The behavior of a discrete-event system is described with atomic DEVS, which uses Finite State Automata to produce output event from the reaction to input event. A coupled DEVS represents overall system as a network of coupled components. These components can be atomic DEVS or coupled DEVS in their own right [START_REF] Bernard | Multifacetted Modelling and Discrete Event Simulation[END_REF].

The metamodel of DEVS is built on top of Eclipse Modeling Framework (EMF) and DEVS formalism [START_REF] Hessam | EMF-DEVS modeling[END_REF]. Knowing that our previous tooling set is also built on top of the Eclipse ecosystem [START_REF]Open source aadl tool environment (osatev2)[END_REF], our motivation to chose DEVS was mainly for interoperability purposes.

DEVS metamodel is divided into structural and behavioral parts where both of them should be defined for atomic and coupled models. The metamodel of DEVS considers formal DEVS models as well as their simulation models developed for given simulator [START_REF] Hessam | EMF-DEVS modeling[END_REF]. DEVS simulation environment is a simulation environment for hierarchical and parallel DEVS models [START_REF]DEVS-Suite Simulator[END_REF].

III. PROPOSED APPROACH

Figure 1 illustrates the overall architecture of our framework. This approach takes advantage of model transformation where a set of target model is automatically generated from a set of source model. In our case, the source model is an AADL model that represents IMA architecture interconnected with TT-Ethernet. This model is conformed to the metamodel of AADL-TTEthernet presented in our previous work [START_REF] Robati | An Extension for AADL to Model Mixed-Criticality Avionic Systems Deployed on IMA architectures with TTEthernet[END_REF]. The metamodel of IMA architecture interconnected by TT-Ethernet captures the main concepts and characteristics of the Time-Triggered Ethernet and describes the structural aspect of a distributed IMA architecture with it. It aims to explain all the concepts specified by this standard. The global information about the network elements and the underlying implementation is described in Figure 2. • Schedulable resources represents all the elements, which uses the network scheduler. These resources can be the partitions hosted by module, the data transferred through the network for example Frames. Partition is a group of time slices in a major frame (MAF) on a module. According to ARINC 653 standard [START_REF][END_REF], each function executes periodically within a partition where it is isolated from all others sharing the core module. Frame is a unit of transmission, a data packet of fixed or variable length, encoded for digital transmission over a communication link.

Considering its order of priority, a frame could be Protocol Control Frame (PCF), Time Triggered (TT) frame, Rate Constraint (RC) frame or Best Effort (BE) frame.

• Processing Resources represents active hardware components in a network. All processing resources have features that can be parameters, access to physical buses or ports (i.e. interfaces for frames inputs and outputs). A processing resource can be Networking Resources such as Switches or Computing Resources such as Modules.

The next step consists of transforming an AADL-TTEthernet model to a DEVS model according to some transformation rules written in the ATL language. The execution environment for ATL is provided by Eclipse framework [START_REF] Jouault | ATL: A model transformation tool[END_REF]. The target model, provided by ATL transformation, is an intermediate model that can be used in the future to perform directly the model simulation realized by DEVS simulation environment.

The target metamodel is the metamodel of DEVS. The simplified version of this metamodel is described in Figure 3. eAtomic and eCoupled are the main classes of DEVS metamodel. The atomic and coupled models perform a simulation model. The simulation models implement abstract models. Every component in the system that includes a behavior is implemented as an atomic model where the Finite State automata of this specific behavior is defined. A coupled DEVS model contains all its sub-components, that can be either atomic or coupled. For the letter, it describes the way of coupling them together. For that, eCoupling classes of DEVS metamodel are used. They support the internal connection between the subcomponents of a coupled model as well as the connectivity of other coupled models. More details about this metamodel can be found in [START_REF] Hessam | EMF-DEVS modeling[END_REF].

Fig. 3. DEVS metamodel

The DEVS model resulted from the transformation step represents an IMA architecture interconnected with TT-Ethernet using AADL that refined with DEVS model formalism. The behaviors of that model is added into its implementation to provide the simulatable model for DEVS simulation environment. We use Acceleo [START_REF]Acceleo[END_REF], to generate the java code from the DEVS model. Acceleo is a pragmatic implementation of the MOF Model to Text Language (MTL) standard [START_REF]Acceleo[END_REF]. Finally, the Java code corresponding to our DEVS model, is loaded and simulated by means of DEVS simulation environment. In the following section we present a case study that demonstrates the feasibility and efficiency of our approach as well as its implementation details. This example is a simplified navigation and guidance system, which is one of the safety-critical function in IMA architecture [START_REF] Lauer | Analyzing end-to-end functional delays on an IMA platform[END_REF]. Figure 4 depicts this example which is composed of four modules and two switches. The Autopilot (AP) module elaborates flight command to reach a defined attitude (the attitude is defined by the next way-point of the flight plan), the Multifunction Control Display Unit (MCDU) presents an interface between the system and crew. The Flight Management (FM) sends periodically to AP the next waypoint(pos) to reach. The Flight Warning (FW) reports to MCDU the equipment status (sens-stat). The last module which is Anemometer (Anemo) computes and broadcasts speed (M) and attitude (Z) to AP.

IV. SIMULATION OF THE NAVIGATION & GUIDANCE SYSTEM

We assume that Z and M are two critical parameters in this example and encapsulated in TT frames. They are transmitted in two distinct frames, by V L 1 from Anemo which is the partition of module 1, to AP which is the only partition of module 4, via SW 1 and SW 2 . The AADL-TTEthernet model and its corresponding DEVS model, are depicted in Figure 5. In the next step we produce the corresponding Java code of the target model using Acceleo [START_REF]Acceleo[END_REF]. Then, we add the behavior of IMA architecture interconnected with TT-Ethernet to the generated Java code. Finally, we load it as a model into DEVS simulation environment. Figure 6 demonstrates the simulated model of navigation and guidance example. For the verification purpose, we can define different simulation scenarios based on the system requirements. In our scenarios we are verifying the scheduling properties that, if held true, will guarantee that the network is running according to the TT-Ethernet specifications. The scheduler of TT-Ethernet request specific constraints and properties, which are presented in [START_REF] Steiner | An evaluation of smt-based schedule synthesis for timetriggered multi-hop networks[END_REF]. One of those constraint is the contention-freedom. We assume that the scheduler is produced by the system and we verify it to ensure the satisfaction of this constraint.

To guarantee the contention-freedom, an End-System (ES) dispatches a frame only after the previous frame completely delivered by the receiver ES. For that, we create Job1 and Job2 to check that if job2 is dispatched only after the reception of Job1 by its corresponding destination. Figure 7 demonstrates the output of our case study. As it can be captured from Figure 7, in 10.0, Module1 relays on Job1 that is received by the output of IMA at 40.0. After this reception, module1 in the same time (40.0) relays on Job2 that is received by the output of IMA in 70.0. That means, even that module1 has two Jobs in its schedule to dispatch, but it relays on second one only after reception of first one. As it is requested by contentionfreedom constraint.

V. CONCLUSION

In this demonstration, we have presented an AADL simulation tool using DEVS simulation environment. Our technique has been implemented and successfully tested on an example of IMA architecture interconnected with TT-Ethernet. It is enough mature to be tested on others IMA example, regardless the complexity of example.

The main motivation of this demonstration is to provide a methodology and a tooling set to assist system engineers to verify the designed system. Accordingly, we provide a modeling language that allows to express the system at a convenient level of abstraction and to interface with sophisticated simulation environment to verify the safety and the performance of the system. Practically, engineers can represent the intended system with an AADL model using our extension and then map it to the discrete event formalism with DEVS. This mapping conform to the corresponding metamodels in both sides. The behavior of the system is added to the mapped model in order to assemble the simulation framework of DEVS simulation environment. The simulation results is used to verify the system requirements.

In future work, we aim at providing other verification scenarios for our topic, in order to guarantee the communication network of IMA architecture is running according to the TT-Ethernet specifications.

Fig. 1 .

 1 Fig. 1. Overall Architecture

Fig. 2 .

 2 Fig. 2. Overview of AADL-TTEthernet metamodel

Fig. 4 .

 4 Fig. 4. The Navigation & Guidance system

Fig. 5 .

 5 Fig. 5. TT-Ethernet Model (top) and the corresponding DEVS model (bottom)

Fig. 6 .

 6 Fig. 6. Simulation graph for the navigation & guidance system

Fig. 7 .

 7 Fig. 7. Simulation results


Joëlle Coutaz
email: joelle.coutaz@imag.fr

James L Crowley
email: james.crowley@inria.fr

Learning about End-User Development for Smart Homes by "Eating Our Own Dog Food"

Keywords: End-user programming, end-user development, connected home, smart home, ubiquitous computing. ACM Classification D.2.6. Programming Environments: Interactive environments. H.5.2. User Interfaces

SPOK is an End-User Development Environment that permits people to monitor, control, and configure smart home services and devices. SPOK has been deployed for more than 4 months in the homes of 5 project team members for testing and refinement, prior to longitudinal experiments in the homes of families not involved in the project. This article reports on the lessons learned in this initial deployment.

Introduction

The "Do-It-Yourself" approach to configuring and controlling domestic technology has become increasingly popular. End-User Development Environments (EUDE) have been developed to support this approach. While the Scratch-based programming language [START_REF] Resnik | Scratch: Programming for all[END_REF] used in the ZipaBox and the rule-based IFTTT propose attractive graphical syntax and stylistics, The DomiCube. The DomiCube is a home-made device designed by 5 retired seniors as the result of a 3 hour focus group. It contains an accelerometer and a gyroscope, and is Bluetooth enabled. It sends events when its state changes (e.g., new orientation, top face, and battery level). The DomiCube was built in the Creativity Lab of the EquipEx AmiQual4Home, ANR-11-EQPX-00. these environments provide limited debugging aids for non-specialists. At the same time, seminal work from academic research such as Jigsaw [START_REF] Humble | Playing with the bits" userconfiguration of ubiquitous domestic environments[END_REF], CAMP [START_REF] Truong | CAMP: A Magnetic Poetry Interface for End-User Programming of Capture Applications for the Home[END_REF], and iCAP [START_REF] Dey | iCAP: Interactive prototyping of context-aware applications[END_REF], has not gone beyond proof of concept. Thus, over the last two years, we have developed SPOK (Simple PrOgramming Kit), an EUDE for smart homes. Our goal is to provide a robust, extensible and flexible system that can be used effectively in the home, and that can be evaluated through longitudinal experiments in real life conditions.

In the next section, we explain our technical choice for the baseline middleware for SPOK followed by a presentation of the principal features. In the final section, we summarize the key lessons learned from the initial deployment of SPOK in our own homes.

Beyond Technical Proof-of-Concept

Implementing a EUDE for real world smart homes requires choosing the "appropriate" run time infrastructure from a jungle of middleware. From our experience with the development of an earlier environment KISS [5], "appropriate", in a research context, means: (1) license free and robust, (2) support for dynamic discovery, (re)composition and deployment without human intervention, and (3) low entry cost for developers.

OSGi satisfies the two first requirements but is too lowlevel for non-system developers. OpenHAB [14], which has been chosen by Eclipse as the Eclipse SmartHome, does not, in its current form, support dynamicity. HomeOS is by construction a .net environment, therefore not compatible with iOS and Android platforms. In the absence of a de facto standard middleware for smart homes, we have used ApAM.

ApAM (Application Abstract Machine) is a componentoriented middleware that extends OSGi/iPOJO in two ways: [START_REF] Dey | iCAP: Interactive prototyping of context-aware applications[END_REF] developers describe an application by intention using a dedicated language as opposed to explicitly specifying composition of components and bindings at design time; (2) from the abstract description of the application architecture, a concrete architecture is computed and incrementally updated by resolving the dependencies between the components currently available in the execution environment. Compared to the state-of-the art, the key features of SPOK are thee-fold: Expressive power of the SPOK language along with a pseudo-natural concrete syntax, dynamic adaptation to the arrival/departure of devices and services, and debugging aids.

Expressive power of the SPOK language

The language supports a mix of imperative and rulebased programming paradigms. For example, the Start-Stop-XmasTree program shown in sidebar, is comprised of an imperative section composed of actions Switch off and Blink, and 2 rules. Conditions can be expressed both in terms of states (e.g., if the blue-lamp is on) and events (e.g., each time the blue-lamp is turned on). Home entities can be denoted by using properties and relations (e.g., all lamps located in bedroom).

Parallelism is supported at multiple grains: several programs can be started simultaneously; within a program, several rules can fire simultaneously and a program can start/stop the execution of another one.

Dynamic adaptation

The grammar of the SPOK language is dynamically updated according to the set of services and devices that are currently available in the home. As a result, the Smart Keyboard, which guides end-users in entering program elements, shows options that are both syntactically valid for the current insertion point, and compliant with the current state of the home (see example in sidebar). Similarly, programs that reference devices and services that are no longer available are flagged so that end-users are made aware that running these programs may result in unexpected behavior. In the example of the Start-Stop-XmasTree shown at the top of the sidebar, the triangle at the top left of the figure indicates that the program is running. The lamp referenced by the Blink action has disappeared from the execution environment. Consequently, its reference has been changed to Unknown and the triangle has turned from green to orange to indicate that execution continues but at our own risk.

Debugging aids

Debugging aids come in three complementary forms: history (by the way of time lines), dependency graph (see sidebar next page), and execution indicators in the source code of SPOK programs. For example, the imperative section of Start-Stop-XmasTree has been executed (counters are set to 1) while no rule has been fired so far (counters are equal to 0) and all of them are waiting for their condition to become true (arrows and light blue background indicate waiting points).

Lessons from Using SPOK in Our Own Homes

SPOK has been deployed for a period of 4 months in 5 distinct homes of project team members. The intent was to test the robustness and usability of the system while refining the system on a weekly basis. Beyond typical bugs, the main findings are the following: improvements for the preparation of field experiments, discovery of new concepts and key issues for future research, and confirmation of findings about our own behavior consistent with results from the literature. (This last issue will not be developed any further here.)

Improvements for field experiments

Harnessing the hardware. Wireless sensors and devices are sensitive to physical conditions (e.g., out of range, lack of power). This sensitivity is generally not "visible". For example, sensors powered with solar cells will fail after a few days without sufficient light. Smart plugs, when installed too far from their dongle, appear and disappear in an unpredictable manner. It is necessary to learn how to build relays between them. The same holds for Hue lamps when blocked by concrete walls. For wireless switches, clicking requires energetic press to generate events. The cover of the DomiCube must be opened to access the led that indicates that it is too Start-Stop-XmasTree is being executed.

Start-Stop-XmasTree is being edited. The Smart Keyboard supports feedforward. far from its Bluetooth dongle. All these details cannot be discovered in the lab. Work-arounds to such problems must be documented and explained to subjects.

Taming the technology. As St-Exupéry wrote for the fox: "If you tame me, then we shall need each other." Indeed, in the first week after installation, it was common to not find any interesting uses for the system. However the system progressively became an integral part of the home as experience was gained. For example, we have discovered that the hue lamps can provide a tangible representation for temperature and energy consumption. We opportunistically wrote a to control the lighting of the Christmas tree (as we repeatedly forgot to stop it manually before going to bed). Our conclusion is that the system must be installed in a subject's home for a minimum of one month to report interesting results. In addition, our programs, which emerged from real life needs, can serve as examples for a forum opened to the subjects.

Discovery for future research and improvement

Privacy issues made real. By analyzing the time lines provided by SPOK, it was striking to discover how much the rhythm of daily life can be discovered from data recorded by the Trace Manager: movements in the home, arrival and departure, meal and bed times, etc. Some devices are more critical than others. In the design of SPOK, we missed the notion of "critical" device. This became clear when we used a smart plug to measure the consumption of our refrigerator, while absent for two days. Such a plug must not fail and cut electricity to the refrigerator -as could possibly through program or user. Similarly, some devices require access control (e.g., TV for kids late at night).

Conclusion

We have two take-away messages. First, longitudinal experiments of a EUDE like SPOK in real-world settings require a middleware that reliably supports dynamic software adaptation and automatic deployment. Secondly, an initial deployment using "our own dog food" in homes of project team members provides highly valuable information for tuning the protocols before the start of field studies, thus improving the quality of the evaluation itself while saving time and discovery for future research.

Extraction of a dependency graph.

The red arrows that converge to Lamp-old-little-desk indicate that the programs Make Energy Visible and Showtemperature-in-livingroom both modify the state of the lamp. This can result in unpredictable behavior if the two programs run concurrently. In this example, Showtemperature-in-livingroom is running (green triangle) while Make Energy Visible is not (green square). In this example, Showtemperature-in-livingroom is running (green triangle) while Make Energy Visible is not (green square).

  Due to the incremental and dynamic (just-in-time) construction and maintenance made possible by ApAM, SPOK is resilient to the opportunistic installation and disappearance of devices and services. The sidebar shows the overall description of the global architecture of SPOK.The Description of SPOKSPOK provides the end-user with the following services:(1) A syntax-oriented program editor that enforces the construction of syntactically-correct programs (see sidebar on next page). (2) A program interpreter and a clock simulator to test program execution in "simulated time". (3) Debugging aids to support the detection and correction of programming errors or system malfunctions along with a Trace Manager. (4) A dashboard to remotely control devices and programs in a centralized and uniform manner.

  Global architecture. The SPOK server runs on top of OSGi/iPOJO augmented with ApAM (right side of the figure). It is structured as two levels of abstraction: (a) The Core World that abstracts away devices such as the Philips Hue lights, homemade DomiCube, physical sensors and actuators supported by a diversity of communication protocols (UPnP, MQTT, EnOcean, BlueTooth), and cloud services (Yahoo! Weather forecast, Google Calendar, gmail); (b) The Extended world whose functional coverage depends on the application domain (e.g., SPOK EUDE). The server runs either on a MiniPC, Raspberry Pi, or a Google Nexus Tablet. Clients (left side of the figure) run a web browser to access SPOK services.

Acknowledgements

This work is supported by the European AppsGate CA110 project. We wish to thank our collaborators: R. Barraquand, M. Bidois, S. Caffiau, J.R. Courtois, A. Demeure, J. Estublier, T. Flury, C. Gérard, C. Lenoir, J. Nascimento, K. Pethoukov, C. Roux, G. Vega.


Laurent Pelliser

Mathieu Manceau

Clotilde Lethiec

Delphine Coursault

Stefano Vezzoli

Godefroy Leménager

Laurent Coolen

Massimo Devittorio

Ferruccio Pisanello

Luigi Carbone

Ferrucciopisanello

Agnes Maitre

Alberto Bramati

Emmanuelle Lacaze

Alignment of Rod-Shaped Single-Photon Emitters Driven by Line Defects in Liquid Crystals

Keywords: liquid crystals, nanorods, fluorescence, self-alignment, oily streaks

come

control on nanocrystals composition and morphology.Rod-shaped nanocrystals showing pronounced polarization, behaving as emitting linear dipoles, have been obtained. [2][3][4] The encapsulation of a spherical core into a rod-like shell [5] resulted in non-blinking inorganic single photon emitters, [6] hereafter referred to as dot-in-rods (DRs). Moreover it has been recently shown that, by increasing the thickness of the shell, it is possible to greatly suppress photoluminescence blinking and to improve DRs overall photo-stability, while keeping a low probability of multi-photon emission. [7] Such features are of primary importance when nanocrystalsare used in applications demanding a control of photons'polarization, such as coupling with complex photonic cavities [8][9] or quantum cryptography. [START_REF] Bennett | Proceedings of IEEE International Conference on Computers, Systems and Signal Processing[END_REF] The control of the polarization of the emitted light also requires the capacity to control the particle orientation. Howevertechnologies aimed at guiding nanocrystal orientation at the single particle level are still poorly discussed in literature.

Alignednanoparticleshave been obtained through mechanical rubbing, [START_REF] Amit | [END_REF] short-range interactions [12][13] or patterned substrates. [14] Liquid crystal-like structures, composed of alarge number of elongated nanocrystalsassembled in multi-layers have also been evidenced on both solid substrates [15][16][17][18] and water films. [18][19][20] Orientation and positional ordering of CdS and CdSenanorods has been obtained through the utilization of a local electric field, exploiting their intrinsic electric dipole moments, [18,[21][22][23] . However, single nanorods are rarely observed once aligned onto the substrate: only average optical properties can be inferred from these experiments. The fluorescence polarization of a number of single DRshas been measured but not for aligned ones. [5,6,24,25] In order to obtain a macroscopic organization and orientation ofsingle nanorods onto a substrate, the use of anisotropic matrices working as hard or soft templatesoffers a promising experimental alternative, as shown for polymer matrices [26][27] , which can be stretched [5,28] ,as for DNA molecules [29] andcarbonnanotubes. [30] An increasing number of works is alsodevoted to the use of anisotropic matrices made ofliquid crystals. [31][32][33][34][35][36] Cholesteric liquid crystals have been used to control the circular polarization of single quantum dots. [37] Nematic liquid crystals have been used to orient single dye molecules, either parallel or perpendicular to the nematic director, depending on the molecular shape. [37,38] In nematic liquid crystals,nanorods can be oriented as well, either parallel or perpendicular to the liquid crystal director,depending on the liquid crystal ability to anchor the nanorod surface, [39,40] with the possible help of magnetic fields. [41,42] However, a serious drawback met in the use of most of thermotropicliquid crystals corresponds to the induced aggregation of thenanorods. [36,[43][44] This aggregation is due to the distortions and disorder induced in the liquid crystal around most of the nanoparticles, which become reduced if the nanoparticles are aggregated. [36,45] In nematic liquid crystals, the best method to prevent aggregation of nanorods is to graft specific ligandsaround the nanorodsin order to allow for a weak anchoring of the liquid crystal molecules. [46,47] Weak anchoring indeed prevents the formation of liquid crystal defects and thus prevents aggregation. For semiconductor nanorods embedded in liquid crystals, average orientations parallel to the nematic director have been evidenced but, to the best of our knowledge, again only ensemble anisotropic emission properties have been studied. [22,46,[48][START_REF] Rodarte | Emerging Liquid Crystal Technologies VII[END_REF] Herein we demonstrate that linear arrays of smecticliquid crystal defects behave as a "smart" matrix to govern the positional and directional ordering of nanorods. Single nanorods can be manipulated and oriented along the defects, along a unique direction for a given substrate. This avoids any liquid crystalinduced aggregation of nanorods, independently of the ligand's nature. We evidence the phenomenon withDRs, single photon emitters,at the single particle level. Statistical analysis of the in-plane orientation of the single DRs leads to a unique orientation with 8° of standard deviation, leading therefore to a fine control of single photon emission polarization.

Although we use core-shell CdSe/CdSDRs as a model system, the technology can be easily extended to a wide class of anisotropic nano-objects. The choice of these particles was dictated by their geometrical properties -a one-dimensional shape used in combination with the linear liquid crystal structures described later on -in order to obtain orientation of the rods; their quantum properties -they behave as single photon emitters [7] -andtheir polarized emission, [6] in order to control the polarization of the emission of single emitters. following. [START_REF] Vion | [END_REF] c) Experimental setup during the polarization measurement.

Colloidal core/shell CdSe/CdSDRs were synthesized by using a seeded growth approach. [18,51] They are constituted of a CdSe core with a diameter of 2.9 nm and surrounded by a rod-like CdS shell (Figure1 a). As confirmed by transmission electron microscopy (TEM) analysis, they present a rod-like shape with an average length l = 23 nm ± 3 nm and a total thickness t ~7nm (figure S2 in Supporting Information).The relatively large thickness is responsible for an increased photo-stability and blinking suppression with respect to thin shell DRs, grown with standard techniques. [7] They are surrounded by organic ligands, namelyTOP (trioctylphosphine) and ODPA (octadecylphosphonic acid).

Solid surfaces consisting of a glass substrate with spin-coated and rubbed polyvinyl alcohol polymer (PVA) of thickness 10nm were used as substrate to realize films of a smectic liquid crystal composed of elongated molecules of 4-n-octyl-4'-cyanobiphenyl (8CB). Drops (40 µL) of a 8CB solution in toluene (2.10 -1 M),containing DRs (10 -13 mol), were spin-coated on top of rubbed PVA-coated substrates at 4,000 rpm during 30 seconds with an acceleration varying between 200 and 300 rpm.s -1 . This results in 8CB films of thickness varying between 100 and 200 nm, where arrays of parallel stripes were visualized by optical microscopy (Figure 2 a).

On PVA rubbed surfaces, a planar anchoring of the liquid crystalline molecules is induced at the interface with the PVA, while a perpendicular (homeotropic) alignment is produced at the air interface.

Such an anchoring antagonism leads to distortions of the smecticfilms (Figure 2b and2c), commonly named smectic "oily streaks" for film thicknesses in the range 100 ~300 nm. [52 -54] The smectic layersare curved between the air and PVA interfaces, stacking on top of each other to form flattened hemicylinders of axis parallel to the substrate and perpendicular to the anchoring orientation, the latter being defined by the PVA rubbing direction (Figure 2a and2 b). The corresponding hemicylinders' periodicity and orientation can be determined by optical microscopy since they are associated with straight linear stripes in the pictures (Figure 2 a). Oily streaks are associated with several highly distorted areas underlined in red in Figure 2 b: -1-the curvature walls, W, between neighboring hemicylinders. [52] -2-the area around the rotation axis C (Figure 2 b andc). This area has been shown on MoS 2 crystalline substrates [55] and rubbed PVA polymer [54] to be formed by a rotating grain boundary, to remove the most curved smectic layers. -3-the region connecting the flattened hemicylinders to the substrate with a straight grain boundary. [54] These grain boundaries connecting different number of smectic layers from each side, they may be composed of a number of straight dislocations parallel to the hemicylinder axis. [54][55][56] Smectic dislocations are linear topological defects,made of elastically deformed smectic layers around a linear core defect with a diameter of the order of the smectic layer width, i.e. ~ 3nm for 8CB. [START_REF] Kleman | Points, lines, and walls: In liquid crystals, magnetic systems, and various ordered media[END_REF] The linear cores are expected to behave as efficient traps for nanoparticles. It has been shownthat gold nanoparticles and quantum dotscan be trapped in oily streaks, leading to the formation of straight chains of nanoparticles, parallel to the dislocation. [START_REF] Coursault | [END_REF] A confocal fluorescence microscopy setup (Figure1 c)was used with either a mercury lamp source or a laserdiode source to excite single DRs.The emitted light was collected by avalanche photodiodes or a CCD camera. To first observe the liquid crystal on the substrate as well as to locate the DRs, amercury lamp with a filter selecting the 436 nm linewas used to illuminate the sample. The light reflected at the interface between the liquid crystal and the glass substrate confirms the presence of the oily streaks (Figure 2 a). To locate the DRs themselves, we used a high-pass filter with a 570 nm cut-off in the detection path, eliminating the reflection from the liquid crystal while allowing the photoluminescence signal from the DRs to get through (wavelength between 575 and 650 nm). is shown in side view for films of thickness around 150 nm, [54] with the areas withsmectic dislocations parallel to the OX axis, being highlighted with the red crosses.

Acircularly polarized pico-second pulsed laser diode (λ=404 nm, repetition rate 2.5MHz) was then focused on each single DRembedded in the liquid crystal (average optical index 1.57) through a high numerical aperture air objective (NA=0.95). As light absorption efficiency of a DR depends on the polarization of the excitation light [39,59] , the chosen circular polarization ensures a comparable excitation for DRs with potentially different orientations, allowing similar emission intensities for all particles.

Low excitation power below the DR absorption saturation levelwas used in order to limit multi exciton emission and blinking. [7] In a first step, intensity second-order auto-correlation at zero delay measurements (g²(0)) were performed with a Hanbury-Brown and Twiss setup consisting of a 50/50 beam-splitter, separating the photon flow to two avalanche photodiodes and measuring the coincidence counts. The corresponding antibunchingis shown in Figure1 b, with the8CB background fluorescence independently measured and substracted as explained in Ref. 50 (see Supporting Information S1). The peak at zero delay, although not fully absent (probably due to weak multiexciton emission), is much lower than the other peaks, which indicates that we are observing a single isolated DR. It allowsto establish that all the measured DRs are single photon emitters and select the isolated ones for further measurements. In a second step, a rotating linear polarizer made of a half-wave plate (HWP) and a polarizing beam splitter (PBS) wasplaced before the 50/50 beam splitter (Figure1c).The rotation of the half-wave plate allowed the analysisof the polarized component of the beam emitted by each isolatedDR. 90s-long time traces wereregistered with the half-wave plate rotating at a constant speed of 1°.s -1 .Representative results of this measurement are reported in Figure3c for typical raw data.

By virtue of their peculiar emission diagram [6] and the generally high level of emitted linear polarization, measured both in ensemble and single particle spectroscopy, [5,24,25,60,61] DRs are commonly associated with one dimensional linear dipoles. [7,25,[START_REF] Vion | [END_REF] In spherical coordinates with z-axis referred as the microscope optical axis (axis perpendicular to the substrate), the orientation of a dipole can be marked out by its in-plane Φ and out-of plane θ angles (Figure 1 a). Itsemission intensity as a function of the analysis angle α is expressed as: [62] I(α)=I min + (I max -I min ) cos²(Φ-α) (1), where I max (resp. I min ) corresponds to the maximum (resp. minimum) intensity when α is varied. They depend on the out-of-plane angle θ, on the numerical aperture of the collecting objective and on the environment of the dipole.The angle αitself is the polarization rotation angle caused by the λ/2 plate (rotated by an angle /2). Its origin has been calibrated by measuring the signal received when the emitted light is replaced by a known polarized signal. The 0° has been defined by the maximum of intensity for a polarization parallel to theOx axis of the optical microscopy pictures (see Figure 3 a-b).

The detected intensity is maximum when α equals to the in-plane angle of the dipole Φ ± π. Thereby, Equation (1) allows the assessment of Φ, giving thorough knowledge of the in-plane orientation of each individual DR dipole. Two different experimental approaches have been used for rubbing the PVA-coated substrates. The firstmethod consisted in rubbing the substrates through a hand-operated procedure, in our case by using cotton sticks, achieving aligned zones, parallel from each other, but extended over small-scale areas only (of the order of several dozens of micrometers -see Figure 3a). These areas are separated by disordered zones, without preferred liquid crystal orientation and thus without oriented oily streaks. The second method uses a rubbing machine providing almost nodisordered zones, essentially showing regular stripes (Figure 3b) aligned along a single direction over the whole sample surface, this direction being perpendicular to the rubbing direction. In Figure 3c, we plot the fluorescence intensity I(α) emitted by three individual DRs, as a function of the polarization analysis angle α, for the manually-rubbed sample covered with a layer approximately 100 nm thick. For each DR, the measured intensity shows the typical cos²(α-Φ) dependence of eq. ( 1), as shown from the comparison between raw data and a cos²(α-Φ) fit. If we compare two DRs localized on two oriented areas (DRs B and C on Figure 3a), we obtain a similar phase of I(α), moreover with an intensity maximum at α = 0°, corresponding to the stripes orientation (Figure 3a). If we compare them with one DR on a disordered area (DR A on Figure 3a), different I(α) phases are obtained. It brings the conclusion that the fluorescencepolarization is maximum in a welldefined directionparallel to the stripes, only when the DRs are localized in oriented oily streaks.The same result isobtained for the I() curves of the DRs of the homogeneously rubbed sample (red circles in Figure 3b). On Figure 3d, the histogram of the angle values corresponding to the fluorescence maximum for the 20 DRs of Figure 3b is presented. A common phase value for the different DRs appears clearly, with an average ofΦ = 29.9° and a standard deviation of 5.6°. This average value is the same than the stripes orientation, visible on optical microscopy (Figure 3b), with a measurement uncertainty of ±1°. If now we consider a larger number of single DRs located in two different samples of similar 8CB thickness of the order of 100nm (52 DRs), we find again a well-defined value for the fluorescence anisotropy, corresponding to the stripes orientation, with a standard deviation of 8°.This demonstrates that, not only the DRsfluorescence share a common orientation, but also that this orientation is the one of the oily streaks defects.

The hypothesis of an influence of the liquid crystal birefringence on the fluorescence polarization anisotropy of the DRs can be ruled out for two reasons. First it has been shown recently that theexcitation anisotropy of DRs is mainly affected by the nature of the ligandsdirectly around the DRs. [25] Second,several ensemble measurements of polarization anisotropy have been conducted within nematic liquid crystals. [22,46,[48][START_REF] Rodarte | Emerging Liquid Crystal Technologies VII[END_REF]63] This led to a maximum fluorescence parallel to the nematic director (extraordinary index) in contrast with the present case.In smecticoily streaks, Figure 3 shows that the fluorescence is maximum for a polarization along the stripes, in other words perpendicular to the smectic direction and corresponding to the ordinary index of the 8CB. The fluorescence is minimum for a polarization perpendicular to the stripes, corresponding to a combination between ordinary and extraordinary index.For bothnematicand smecticliquid crystals, the fluorescence anisotropy canbe attributed to an in-plane orientation of the DRdipole, imposed by the liquid crystal and not to an optical birefringence effect. In nematic liquid crystals the fluorescence polarization anisotropyis related to an orientation of the nanorodsparallel to the liquid crystal director, as it is most often the case due to the liquid crystal anchoring at the nanorods surface. [22, 39-40, 46, 48-49, 63] In smectic oily streaks, the in-plane projection of the DRs dipole is oriented parallel to the oily streaks stripes (scheme of the dipoles on Figure 3). It thus parallel to the linear defects, and, perpendicular to the liquid crystal director (Figure 2). This suggests a different physical mechanism for the aligning phenomenon in smectic oily streaks compared to orientednematic liquid crystals.

The dipole orientation with respect to the smectic texture is confirmed bya defocused microscopy technique, [6,48] already used toassessDRs dipole orientation. [6,59] It has been employed by means of an oil immersion microscope objectivewith high numerical aperture (NA1.4)positioned 500 nm away from the focal point. As shown in Figure 4, bright and dark arcsappear around each original focused spot, confirming the dipolar nature of theemission. [6,[START_REF] Rodarte | Emerging Liquid Crystal Technologies VII[END_REF]59,62,[64][65] These defocusing patterns giveinformation on both in-plane and out-of-plane dipole orientation, [62,[64][65] if it is taken into account that they are influenced by several other parameters such as NA of the objective, dielectric environment (liquid crystal and air interface) and that they are significantly dependent on the distance between the objective focal planeand the sample [START_REF] Rodarte | Emerging Liquid Crystal Technologies VII[END_REF][51][52] For linear dipoles, defocused images displaying lobe patterns with a single symmetry axis correspond to dipoles neither horizontal nor vertical, but rather tilted with respect to the substrate.By connecting the two minima of the internal arcs,the dipole in-plane component orientation can be assessed:as shown in the upper-left inset of Figure 4, it is parallel to the oily streaks axis, highlighted in the bottom-right inset.Thisconfirms the result gained from Figure 3. Importantly, again, this specific orientation is common to the majority of the isolated DRswithin the rubbed area (See Figure S3). On Figure 4, the asymmetry of the defocusing spots shows a tilt of the DRs dipoles out of the substrate plane. In order to supplement these defocusing measurements, we have considered the degree of linear polarization δ for the emitted light of the single DRsin the liquid crystal matrix: δ = (I max -I min )/(I max +I min ). I max and I min are obtained from polarization analysis curves as in Figure 3c, after careful backgroundsubstraction. For DRsapproximated by linear dipoles, [7,28,59] δ can be theoretically calculated taking into account the dielectric nature of the environment of the dipole. [62] The theoretical curve of the degree of polarization δ as a function of the dipole out-of plane tilt, θ, with respect to the microscope optical axis (normal to the substrate), is shown on Figure 5a for a linear dipole located in a 1.5 index medium, whose emission is collected by a 0.95 NA air objective. [62] δ ≈1 for θ =90°, which is a horizontal dipoleand δ = 0 for θ =0°, which is a vertical dipole.

We measured the degrees of polarization of 52DRs dispersed in two similar samples of liquid crystal thickness around 100 nm, including the one of Figure 3b. We removed, for this measurement, the signal of theDRsnot aligned within 6° to the liquid crystal stripesandmost probably corresponding to nanoparticles of different shapes (see TEM image displayed in figure S2). [25] The obtained histogram of degree of polarization,for the 42 remaining DRs,is shown on Figure 5b. A well-defined peak is evidenced between 0.6 and 0.7. As shown by Figure 5a, this limited value of polarization is consistent with theout-of plane tilt of the emitter dipolesevidenced on the defocalization results of Figure 4. It may also be associated with DRsnot fully polarized, as shown in a number of ensemble measurements, [5,[24][25] in particularforCdSe/CdSDRs of similar ratio core diameter over DR diameter, the role of this last parameter being recently underlined. [46] The broad distribution of degrees of polarization observed on Figure 5b may be related to the dispersion of size and shape of the DRs (see figure S2), to the distribution of core shape, [24][25][60][61] together with possible distribution of dipole out-of plane orientation. In a similar geometry of single polarization measurements performed on the same kinds of DRs deposited on glass, with, in addition, an AFM mounted on an inverted microscope to probe the single DRs orientation, it has been recentlyevidenced that the maximum of fluorescence was obtained for a polarization parallel to the single DRsaxis. [24] Together with our observation of in-plane dipoles parallel to the oily streaks stripes visible by optical microscopy, this suggests thattheDRsaxis is itselforiented parallel to the stripes.DRs are thus perpendicular to the 8CB anchoring direction, but parallel to the 8CB hemicylinder axis and thus parallel to the expected dislocations of oily streaks. the evidence of nanorod trapping, allowing for nanorods orientation as well, may confirm the presence of aligned dislocations in the oily streaks structure.Smectic dislocations are characterized by a disordered linear core of high energy with a diameter of the order of a fewnanometers. [START_REF] Kleman | Points, lines, and walls: In liquid crystals, magnetic systems, and various ordered media[END_REF] The DRs width (with a total of 7nm) matches the one of the smectic dislocation cores. In addition to their elongated shape, this size matching promotes their trapping inside the line defects, in agreement with the previously evidenced phenomenon of nanospheres trapping by topological LC defects, [66][67][68][69] . The induced orientation of the DRs, parallel to the dislocation cores (Figure 3), may correspond to a precise localization of the DRs within the disordered cores. This localization of DRswithin and parallel to the dislocation coreindeed maximizes the volume of disordered liquid crystal expelled by the DRs and thus decreases the disorder energy of the smectic liquid crystal film in the presence of dislocations. If we consider elementary smecticdislocations, their energy per unit of length has been measured in free standing smectic filmsto be 0.5kT.Å -1 . [70] Asingle DR of length l = 23 nm, trapped in the dislocation core and parallel to its axis, allows todecrease the liquid crystal disorder energy by115kT, leading to a significant advantage for the liquid crystal film. TheDRs, once trapped in smecticdislocations, may be particularlywell-stabilized.

Only motion of the DRs along the dislocations cores may occur, in agreement with experimental observations. Our results may consequently correspond toDRs, trapped within the liquid crystal dislocations, parallel to the substrate and parallel to the 8CB linear stripes.

The origin of this nanorod induced orientation is obviously different from the one induced in nematics, this latter being driven by the anchoring of liquid crystal molecules at the DRsurface, usually leading to DRsoriented parallel to the nematic director. [39][40] In contrast, in smectic oily streaks, the induced orientation is parallel to the dislocations, thus perpendicular to the liquid crystal director. Generally speaking, if the nanorod diameter is small enough to avoid, outside the dislocations core, a newsmectic distortion/disorder energy larger than the energy advantage associated with the nanorod presence in the dislocation core, we expect no liquid crystal-induced aggregation. As a consequence, contrary to the nematic case, the liquid crystal anchoring at the DR surface is also expected to have almost no influence and the DRsmay be efficiently oriented by the dislocation, independently of the liquid crystal anchoring at their surface. This appears in agreement with the fact that nanospheres surrounded by different ligands, alkylthiols, aresimilarly linearly oriented, since they formchains parallel to the dislocations in the 8CB oily streaks. [START_REF] Coursault | [END_REF] Ifthe DR axis isparallel to the smectic dislocations, an out-of plane tilt of the DR dipole corresponds to an emitting dipole tilted by an angle  (see Figure 1a) from the horizontal nanorodaxis, in agreement with ref [59]. In presence of a  angle between the fixed DRaxis and the dipolewe anticipatea free rotation of the dipole around the DR [59] . In contrast, Figure 3 and 4 suggest that the dipoles remain all oriented in the plane defined by the rod and the normal to the substrate.The origin of such a strictly induced out-of-plane dipole orientation is not clear. Surface charges may exist on these DRs, related either to the crystallographic orientation of the nanorodsurface [71] and/or to dangling bonds unsaturated by the surface ligands. [72] A symmetry breaking in the smectic phase at the DR interfacemay occur, due to the charges at the DR surface, which may orient all neighbouring 8CB molecular dipoles. [71][72] Strong electric dipolar interactions between the 8CB molecular dipoles (4.9 D) and the DR dipoles [71] maythus favour DR dipole orientationin the plane parallel to the 8CB stripes and perpendicular to the substrate. This outstanding property of the smectic oily streaks evidences a good control of single emitters since, with our smectic liquid crystal/DRs composites, we create a dispersion of single photons emitters of controlled polarization phase, oriented along a unique direction for one given sample. It opens the way to macroscopic nanoemitter lines, sources of well polarized single-photon emission.Generally speaking, the ability to orient nanorodsshows a high potential of thesmectic oily streaks for the control of nanoparticles'optical properties. This goes well beyond semi-conducting nanoparticles, being, for example, well adaptedfor inducing anisotropicplasmonic extinction of metallic nanorods.

In conclusion, we showed that the oily streak structure created by a liquid crystal deposited on a rubbed polymer induces an alignment along a unique direction of the dot-in-rods (DRs) diluted in the liquid crystal matrix,leading to fixed orientation for the emitting in-plane dipoles. This has been shown at the single particle levelthanks to the evidence of the intensity second-order autocorrelation function of each DR.Over a collection of DRs, we found the fluorescence polarization orientations to be along the liquid crystal stripes within a 8° standard deviation. The dipoles of the DRs used in this study thus behave as individual polarized single photon emitters. This orientation along the oily streaks axis is likely due to the trapping of the DRs within the smectic dislocation cores, oriented along a single direction, together with electric dipole-dipole interactions between the DRsdipoles and the liquid crystal molecules. This leads to an orientation of the DRs without aggregation, a priori independently of the ligand's nature around the DRs. This work thus shows the feasibility of a large-scale orientation of anisotropic emitters without the stringent requirements shown in previous studies (control of the ligand's nature, continuity of the sample, particles in direct contact with each other or under the influence of an external electric field). The experiment demonstrates the trapping efficiency of smecticdislocations which not only trap but also align elongated nano-objects, along a single direction for a given sample, thanks to the use of rubbed polymer substrates. These results open the way for not only orienting dot-inrods but also for creating chains of oriented dot-in-rods emitting polarized light.

In order to take into account the contribution from the background, we used the procedure described in the appendix of [START_REF] Vion | [END_REF] . This procedure has already demonstrated its ability to describe experimental data with great accuracy (see fig. 2 of [50]). Let us summarize this procedure used here for the 8CB-nanorod system, keeping the notations of Ref. [50].

(a) We measure independently the fluorescence of a portion of 8CB without nanorod and we measure the 8CB fluorescence decay rate: Gamma_p = 0.12 ns -1 (b) From the file used to plot the nanorodantibunching curve, which contains the arrival time of each photon individual, we can plot the detected intensity as a function of time. The detected intensity is a sum of the respective intensities of the fluctuating nanorod emission (I_NC(t)), the 8CB emission (B_P), and the photodiode dark counts (B_0). Because of some residual blinking, this curve shows some brief time intervals when the nanorod is not emitting: the detected intensity is then the background intensity B_0 + B_P = 2000 counts per second (cps). By substracting this background contribution, we can calculate the average nanorod intensity <I_NC(t)> = 14.6 kcps and the average squared intensity <I_NC²(t)> = 4.3 10 8 cps².

(c) Finally, from the same measured file, it is possible to plot the decay curve, which has a constant component (the dark counts, which are not correlated to the excitation laser pulses) and a decay component (sum of the nanorod and 8CB decays, which can be distinguished as the nanorod decay is much slower than the 8CB decay). The constant component of the decay curve yields the dark counts rate: B_0 = 410 cps. The slow decay component yields the nanorod decay rate: Gamma = 0.046 ns -1 .

We have measured all the experimental constants necessary to describe the antibunching curve following the model of ref. [50]. The antibunching curve is an intensity autocorrelation curve, thus a sum of the background and nanorod autocorrelations and the background-nanorod correlation. On Fig. 1, in order to plot only the nanorod autocorrelation, we plot the experimental antibunching curve from which we substract the theoretical background autocorrelation (Eq. 19 of ref. [50]) and background nanorod correlation (eq. 20 of ref. [50]). S2: Pictures of the CdSe:CdS dot-in-rod particles taken with a Transmission Electron Microscope.

Figure 1 .

 1 Figure 1. a)Schematic of the DRs with the angle between the DR axis and the dipole indicated,

Figure 2 .

 2 Figure 2. a) Oily streaks observed by optical microscopy on a sample 120 nm thick, viewed from the

Figure 3 .

 3 Figure 3. a) Superposition of the pictures obtained in optical microscopy (oily streaks) and fluorescence

Figure 4 .

 4 Figure 4. (Main) Photoluminescence of DRs illuminated with the 436 nm band of a Hg lamp in

Figure 5 .

 5 Figure 5. (a) Degree of polarization of a linear dipole located in a 1.50 refractive index medium, whose

Acknowledgements

The authors would like to thank Dominique Demaille and Francis Breton.For financial support, they also would like to thank the AgenceNationale de la Recherche (P3N Delight, JCJC Ponimi and PNanoNanodiellipso), the programsC'nanoNanoPlasmAA and C'Nano Sophopol, the PUF program of the French Embassy in the United States of America.