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Fluorescent nanodiamonds containing negatively-charged nitrogen-vacancy (NV−) centers are promising for a wide range of applications, such as for sensing, as fluorescence biomarkers, or to hyperpolarize nuclear spins. NV− centers are formed from substitutional nitrogen (P1 centers) defects and vacancies in the diamond lattice. Maximizing the concentration of NVs is most beneficial, which justifies the search for methods with a high yield of conversion from P1 to NV−. We report here the characterization of surface cleaned fluorescent micro- and nanodiamonds, obtained by irradiation of commercial diamond powder with high-energy (10 MeV) electrons and simultaneous annealing at 800 ∘C. Using this technique and increasing the irradiation dose, we demonstrate the creation of NV− with up to 25% conversion yield. Finally, we monitor the creation of irradiation-induced spin-1 defects in microdiamond particles, which we associate with W16 and W33 centers, and investigate the effects of irradiation dose and particle size on the coherence time of NV−., acceptedVersion

In the medical and surgical fields, robotics may be of great interest for safer and more accurate procedures. Space constraints for a robotic assistant are however strict. Therefore, roboticists study non-conventional mechanisms with advantageous size/workspace ratios. The determination of mechanism workspace, and primarily its boundaries, is thus of major importance. This Note builds on boundary equation definition, continuation and automatic differentiation to propose a general, accurate, fast and automated method for the determination of mechanism workspace. The method is illustrated with a planar RRR mechanism and a three-dimensional Orthoglide parallel mechanism.

International audience; Sensitivity analysis is a key tool in the study of the relationships between the input parameters of a model and the output solution. Although sensitivity analysis is extensively addressed in the literature, little attention has been brought to the methodological aspects of the sensitivity of nonlinear parametric solutions computed through a continuation technique. This paper proposes four combinations of sensitivity analysis with continuation and homotopy methods, including sensitivity analysis along solution branches or at a particular point. Theoretical aspects are discussed in the higher order continuation framework Diamant. The sensitivity methods are applied to a thermal ignition problem and some free vibration problems. Remarkable eigenvalue maps are produced for the complex nonlinear eigenvalue problems.

The application of transparent conducting oxides in electronic devices like solar cells or displays is common. By transferring this technology to quantum sensing and computing in the form of microwave conductors, it is possible to benefit from the advantages of these materials. By using indium tin oxide (ITO), it is demonstrated that at an arbitrary position below the conductor, an arbitrary elliptical microwave polarization can be produced by two independent sources. This is independent of the geometry and size of the ITO, whereby a non-resonant microwave approach can be chosen. Using single nitrogen vacancy (NV) centers in diamond in combination with a cross-like ITO structure, each NV center can be addressed with an ideal (clockwise or anticlockwise) microwave polarization. By optimizing the coupling of the microwave field to the NV centers and minimizing the conductor size, the creation of smaller devices compared to common approaches is possible., publishedVersion

African migration is not determined just through misery and danger. Personal ambition is an important catalyst compelling the more intrepid to hit the road. The decision to leave can result in a pressing urge to change lifestyle, to invent new ways of life, to explore far-off lands, real or imaginary. The migratory adventure is not only synonymous with a departure abroad – close or distant; it is also similar to a moral experience which is tightly correlated with risk or intensity of life. After introducing the different promoters of the African migratory adventure, the article will show that more and more African women, in the process of their migration, claim the status of the adventurer for themselves. Then, the times of adventure will enlighten, the beginning, the time of youth, and the end when the migrants come back home. Several outcomes to the migratory adventure are also possible. Upwards, for those who are able to convert their mobility capital and connect themselves to transnational networks. D...

In the race towards high resolution X-ray imaging, the current X-ray windows have shown thermal limitations. The beryllium used in those windows does not provide an efficient spreading of the heat generated in the target. This thesis results from a collaboration between Thales and the french Atomic and Alternative Energies Commission (CEA). It aims at studying, designing and synthesizing innovative diamond for X-Ray tubes. The semi-conducting properties of diamond are used to integrate a built-in flow sensor and to monitor in-line the dose rate of the tube. The transmission windows fabricated in the context of this work are called “smart-windows”. The thermal, mechanical and sensing properties of such windows have been modeled by using a multi-domain approach. Two devices made either of polycrystalline or single crystal diamond were designed. In order to integrate those windows experimentally, a small series must be realized. Hence the experimental conditions have been optimized to increase the growth rate of the film. A new tools has also been developed to monitor in real time and in situ the growth rate and the morphology of the films. Finally the mechanical resistance and the transparency of the devices have been characterized. Several experimental set-ups have been developed to test the detection properties in a tube-like design. Some prototypes of smart-windows have been integrated in an experimental X-Ray tube. This prototype delivers a signal proportional to the dose rate of the tube without disturbing its operation., Dans le domaine de l'imagerie par rayons X, la course à la haute résolution mets aujourd'hui en évidence les limites des tubes actuels. Le béryllium utilisé pour fabriquer les fenêtres des tubes à rayons X ne permet pas de dissiper les densités de puissance mises en jeux. Cette thèse est le fruit d'une collaboration entre Thales et le Commissariat à l'Energie Atomique. Elle vise à étudier, concevoir et synthétiser des fenêtres innovantes en diamant pour les tubes à rayons X. Les propriétés de photoconduction du diamant sont utilisées pour intégrer une fonction de détection en ligne. Les fenêtres en transmission conçus dans le cadre de cette thèse sont appelées smart-window. En utilisant une approche multi-domaines, nous avons modélisé les phénomènes thermiques, mécaniques et de détection. Deux dispositifs différents en diamant polycristallin et monocristallin ont ainsi été conçus et dimensionnés. Pour intégrer ces fenêtres en situation expérimentale, une petite série doit être fabriquée. Ainsi, les conditions de synthèse ont été optimisées afin d'augmenter la vitesse de croissance du diamant. De nouveaux outils ont également été développés afin de suivre in situ la vitesse et la morphologie du film pendant cette croissance. Finalement, la résistance mécaniques et la transparence des fenêtres ont été caractérisées. Plusieurs bancs de test ont été développés pour tester leur fonction de détection en laboratoire. Différents prototypes de smart-windows ont été intégrés dans un tube expérimental. Ce prototype de fenêtre innovante en diamant délivre une mesure proportionnelle au débit de dose généré par le tube sans perturber son utilisation.

The gems and diamonds networks : the end of their parallel trajectories ? The gems and diamonds networks have long followed parallel trajectories. The two markets which have largely been ruled by leading protagonists have sustained and financed many conflicts in some Southern countries which extract gems. In the 1990's, the emergence of new countries specialized in gems meant the end of similaritiesbetween the two networks. As it claimed it was the world leader in diamond production in the 21th century, Canada has deeply transformed the trading network of gems. One of the most unexpected effects of this transformation was undoubtedly the gradualending of many conflicts in the African countries producing gems. At the same moment Madagascar was discovering huge gems deposits. But this discovery did not trigger off the same effects as those linked to the Canadian discovery. This is mainly due to the fact that Madagascar is still incapable of influencing the worldwide economics in order to modify it for its own sake.; Les filières « pierres précieuses » et « diamant » ont longtemps connu des trajectoires parallèles. Les deux marchés, largement phagocytés par des acteurs en position de monopôle, ont entretenu et financé de nombreux conflits dans certains pays du Sud producteurs de gemmes. L'émergence de nouveaux pays producteurs au cours des années 1990 a scellé la fin des similitudes entre les deux filières. En s'annonçant comme le leader mondial de la production de diamant au XXIe siècle, le Canadaa profondément transformé les circuits de commercialisation des brillants. Un des effets les plus inattendus de cette transformation de la filière est sans aucun doute l'arrêt progressif de nombreux conflits dans les pays africains producteurs. Au mêmemoment Madagascar découvrait d'immenses gisements de pierres précieuses. Mais cette découverte n'a pas produit d'effets comparables à ceux liés à la découverte canadienne. Ce constat tient largement au fait que Madagascar reste incapable de peser sur le système économique mondialisé pour le modifier en sa faveur.

La région de Séguéla, au centre-ouest de la Côte-d'Ivoire, est connue pour son champ diamantifère alimenté par des dykes de kimberlite et de lamproïte. Ces dykes, non déformés et non métamorphisés, recoupent les formations du Birimien. Leur orientation N 170° est contrôlée par le contact structuré entre les lithosphères archéenne et paléoprotérozoïque du craton ouest-africain. La découverte d'un diatrème avec les brèches de cheminée et les sédiments du maar préservés sous les colluvions actuelles atteste l'âge géologique relativement récent (Crétacé ?) de l'activité kimberlitique. The Séguéla area in Ivory Coast is known for its diamond-bearing field related to dykes of kimberlite and lamproite. These dykes, devoid of any deformation and metamorphism, crosscut the Birimian formations. Their N 170° orientation is controlled by the tectonized contact between the Archean and the Paleoproterozoic shields of the West-African craton. Discovery of a diatreme, with its pipe breccias and well-preserved maar sediments, below the present-day colluvia, attests for the probable recent geological age (Cretaceous?) of the kimberlitic activity.

- Sierra Leone figures the archetyp of these african countries, particularly well-fitted up of raw materials, where development has failed. The corruption of the government, unable to handle a development and peace process, and numerous international implications for the appropriation of country wealth had moved that small country in the main focus of destabilisation in west Africa., Résumé. - La Sierra Leone illustre l'échec du développement de cette Afrique riche en matières premières qu'on aurait pu croire la mieux dotée aux indépendances. Etat corrompu et tourné vers sa seule perpétuation, sanglants conflits pour l'appropriation de la rente, implications internationales multiples font aujourd'hui de ce petit pays un des principaux foyers de déstabilisation en Afrique de l'ouest., Brunel. Sierra Leone : les difficultés du développement dans une société en armes (Sierra Leone : problems for development in an armed society). In: Bulletin de l'Association de géographes français, 79e année, 2002-2 ( juin). Géopolitiques africaines, sous la direction de Roland Pourtier. pp. 237-250.

Wildcat Exploitation of Gold and Diamonds in Upper Zaire, 1982-1995. For decades, the copper, gold and diamond industries of Zaire were in a dominant position in the country, for example, the companies of Gecamines, Miha, and Okimo. But since the diamond and gold quarries were liberalized in 1982, those great corpo¬ rations have been bypassed by tens of thousands of indépendant miners, who are scattered everywhere in Zaire, especially in the region of Upper Zaire. This has resulted in disastrous environmental problems, like river pollution, the water being polluted because of the mercury and chloride used to process gold ore ; large, bursting communities of settlers who have established themselves in inadequate areas ; and the destruction of protected game with war weapons. All this has happened due so a lack of government control over these new «businessmen» operating in the bush. The two authors deal here with work and hygiene conditions as well as with the appearance of lawlessness, a Far West-like behavior, which may divert rural popu¬ lations from agriculture, cattle raising, and craftmanship, since easy money is to be found no longer at commercial banks, but in gold and diamond quarries in the forest. They question the future benefits of these earnings, compared to the environmental damage and the abandonment of plantations and the falling farm production., Pendant des décennies, les industries du cuivre et du diamant telles que la GECAMINES MIBA et l'OKIMO ont dominé l'économie zaïroise ; Mais depuis la libéralisation de l'exploitation artisanale de l'or et du diamant en 1982, ces géants de l'économie ont été pris de vitesse par des dizaines de milliers d'orpailleurs et de creu-seurs indépendants, éparpillés partout au Zaïre. Dans la région du Haut-Zaïre, on observe le même phénomène. Cette forme d'exploitation a donné lieu à des problèmes d'environnement : pol¬ lution des eaux des sources et des rivières par le mercure et l'acide chlorhydrique utili¬ sés dans le traitement de l'or : formation de grosses bourgades qui poussent comme des champignons sur des sites non appropriés, et exterminationd'animauxprotégésàl'aide-d'armesdeguerre. La carence de contrôle des pouvoirs publics sur ces nouveaux types de mineurs en pleine forêt est, parmi d'autres, l'une des cause de ces dégâts écolo¬ giques Les deux auteurs s'intéressent ici aux conditions de travail et aux conditions d'hygiène, ainsi qu'à l'apparition d'une mentalité de hors-la-loi et de Far West, menta¬ lité qui risque de détourner les ruraux de l'agriculture, de l'élevage et des activités arti¬ sanales, du fait que l'argent a fui l'agriculture, les banques commerciales et les villes en général, à destination des carrières dans la forêt. Ils s'interrogent sur les bienfaits éventuels de l'exploitation artisanale, mise en parallèle avec la destruction de l'envi¬ ronnement et l'abandon des plantations., Indring'i Ade Nyori, Bamuhiga Loni Buga. L'exploitation artisanale de l'or et du diamant dans le Haut-Zaire (1982-1995) : réponse à la crise, conséquences sur l'environnement. In: Cahiers d'outre-mer. N° 202 - 51e année, Avril-juin 1998. pp. 157-170.

Business Horticulture in the Windward Islands, Society Archipelago, French Polynasia ; an Industry of the Future. In the Windward Islands, horticulture has thrived as a business since the 1960s. The farms are very small and benefit from the know-how accumulated by past generations. In spite of obvious human and climatic advantages, the environmental and human (joint possession) factors, political economic difficulties, the distant consumption areas, the airfreight cost, all increase dramatically the price of the flowers because of the very aggressive worldwide market conditions at present. The export of tropical flowers is therefore quite difficult. As a consequence, it is also difficult to envisage what the future of this very special industry will be., L'horticulture aux Iles du-Vent (archipel de la Société, Polynésie française) a pris son essor en tant qu'activité commerciale depuis les années 1960. Elle s'inscrit dans des exploitations micro-fundiaires et bénéficie de savoir-faire ancestraux. Si les atouts humains et climatiques sont indéniables, les handicaps naturels, humains (indivision) et politico-économiques, les contraintes liées à l'éloignement des bassins de consommation et au coût du fret pèsent de tout leur poids sur la cherté des fleurs produites, confrontée à un marché mondial des plus concurrentiels. Dans ces conditions, l'exportation de ces fleurs tropicales est ardue et l'avenir de cette «niche» économique semble délicat., Cerveau Marie-Pierre. L'horticulture commerciale dans les Iles du-Vent, archipel de la Société, Polynésie Française : une activité d'avenir ?. In: Cahiers d'outre-mer. N° 202 - 51e année, Avril-juin 1998. pp. 141-156.

The field emission properties of thin, fine-grained diamond films were investigated by measuring emission currents versus electric field curves. The measurements were performed with a spherical electrode attached to a piezoelectric positioning system. The lateral distribution was analyzed by accelerating emitted electrons onto a fluorescent screen. In addition the transient behavior of the emission current was investigated. These characterization techniques were applied to a large number of CVD diamond films deposited by microwave plasma-assisted CVD. The samples were prepared with various methane concentrations (0.5-7%) and deposition temperatures (700-900 degrees C). Undoped as well as boron- and nitrogen-doped samples were studied. Under optimized conditions threshold field strengths as low as 2 V/ mu m were realized, yielding current densities in the range of several mA/cm2 at 5 V/ mu m. The density of emission sites is on the order of 104 sites/cm2

We have deposited epitaxial diamond films with very low angular spread on epitaxial beta-phase silicon carbide layers on silicon (001) substrates. From x-ray rocking curve measurements, half-widths of the angular spread of the crystal orientation as low as 0.6 deg have been determined, which is the smallest value ever reported in heteroepitaxial diamond films and appears to be smaller than those of the beta-phase silicon carbide underlayers. The film surface exhibits a roughness of about 100 run with very few discernible boundaries due to misorientation. The optimization of the bias-enhanced nucleation process and the control of selective growth are the main factors for the improvement of the crystallinity.

Polycrystalline diamond films were prepared by Microwave plasma assisted chemical vapour deposition from CH4-H2 mixtures. For p-type doping with boron, trimethylborate was added at concentrations between 50 ppb and 500 ppm referred to the total gas phase. The boron concentration in the film, as determined by secondary ion mass spectrometry, varied between 1.1 x 10(exp18) cm(exp-3) and 2.1 X 10(exp20) cm(exp-3). A linear increase in the boron content in the film was observed for boron concentrations in the reactant gas up to 10 ppm. The boron incorporation saturates for gas phase concentrations of more than 50 ppm. For non-contact characterization of the doped films. Raman and Fourier transform spectroscopy were applied. With increasing boron concentration, the Raman spectra show an increasing asymmetry in the lineshape of the 1332 cm(exp-1) zone centre optical phonon which is attributed to a Fano interference effect with the electronic continuum. Strong IR absorption around 3000 cm (ex p-1) due to acceptor ionization was observed and related to the boron concentration. Temperature dependent electrical measurements were taken to obtain information on the resistivity, mobility, activation energy and carrier concentration. Nitrogen is an omnipresent impurity in diamond and, as a deep donor, is able to Compensate acceptors. In order to study the influence of nitrogen contamination, a series of diamond films with constant boron content and various nitrogen concentrations was prepared and characterized. The data reveal the strong influence of nitrogen on the properties of boron-doped diamond films. In particular, the conductivity is decreased by one order of magnitude, highlighting the compensating character of nitrogen in p-type doped diamond.

Heteroepitaxial diamond growth has been attempted on mirror-polished monocrystalline (001), (111), and (110) silicon substrates by microwave plasma CVD. The surface morphology and the crystallographic properties of the films were characterized by means of scanning electron microscopy (SEM), Raman spectroscopy, x-ray diffraction, and x-ray and Raman pole-figure analyses. The results demonstrate epitaxial growth of diamond on both (001) and (111) oriented silicon substrates. Preliminary results give strong evidence for substrate-induced orientation of the diamond crystallites also on (110) oriented silicon substrate. The heteroepitaxy can be assigned to the oriented covalent bonding across the interface between diamond and silicon.

The surface reaction of thermal atomic hydrogen with polycrystalline diamond films, prepared by hot-filament assisted chemical vapour deposition has been investigated. Atomic beam techniques in combination with mass spectroscopic detection of the formed product molecules, have been used to study hydrogen-induced erosion. When compared with a-C:H films, the reaction of H 0 with diamond films is negligible. The yield is orders of magnitude smaller and reaches maximum values below 10 -4 around 500 K. After starting the atomic hydrogen exposure, a transient behaviour is observed with 10 times higher yield, probably due to a reaction with remaining amorphous carbon.

Structure and morphology of polycrystalline diamond films prepared by chemical vapor deposition (CVD) have been studied using x-ray texture analysis, angle-resolved optical reflection, and scanning electron microscopy. The films under investigation exhibit a pronounced 100 fiber texture, i.e., a preferential alignment of (110) planes perpendicular to the growth direction. By thinning a 180-Mym-thick CVD diamond film in an oxygen discharge the dependence of the degree of 110 texture on the film thickness has been investigated. It was found that the crystals formed at the beginning of the film growth are randomly oriented, and that a preferential orientation of (110) planes develops with increasing film thickness. Computer simulations show that this behavior can be explained by evolutionary selection, i.e., competing growth of differently oriented crystals, which implies that (110) is the direction of fastest growth. In addition, angle-resolved optical reflection and scanning electron mi crographs show that the surface of the diamond films consists of (111) face. Possible explanations for these findings are discussed.

The submitted contribution describes the development of breeding in the Czech Republic from the first half of the 19th century to the present. Political and agronomical factors affecting barley breeding are briefly characterized. Attention is devoted mainly to the malting barley varieties that were bred during the followed period. The varieties Proskowetz Hana Pedigree, Kneifl9s barley, Valtický and Diamant became donors of the malting quality for many other Czech and foreign varieties of malting barley.(In Czech, English summary only)

The intrinsic decay dynamics of pair excitations involving a deep donor and a shallow acceptor in chemical-vapor-deposited diamond is studied by time-resolved photoluminescence. Appropriate excitation conditions result in a distinctive decay behavior of individual donor-acceptor pair excitations, with extremely short radiative decay times in the picosecond-to-nanosecond regime.

Properties of crystalline materials may vary to a considerable extent depending on their growth histories and growth conditions. This fact forms the basis on which a distinction between natural and synthetic gem materials is made. The differences do not appear on an atomic or a lattice scale, but can be detected on a larger scale in which changes occurred during growth processes are reflected. The latter includes external morphology of crystals, surface microtopography of crystal faces, growth bandings, sector structures, inclusions, dislocations, planar defects, like stacking faults and micro-twins, etc. Since growth mechanisms are different among crystals grown from different phases, and the environmental conditions are different among crystals grown from similar phases, the differences between natural and synthetic gem materials of different origins will be visualized if appropriate methods of detection are applied. To demonstrate this, lattice images of natural and synthetic emeralds, X-ray topography and surface microtopography of natural and synthetic diamonds and emeralds are compared., Les propriétés des matériaux cristallisés peuvent varier d'une manière considérable en fonction de leurs histoires et conditions de croissance. Ceci est à l'origine de la distinction entre matériaux gemmes naturels et synthétiques. Ces différences n'apparaissent pas à l'échelle atomique ou à celle du réseau, mais se manifestent à plus grande échelle lors de modifications des processus de croissance. Ces différences touchent la morphologie externe des cristaux, la microtopographie des faces cristallines, les zones de croissance, la sectorisation, les inclusions, les dislocations, etc. Les mécanismes de croissance étant différents pour des cristaux crûs à partir de phases dissemblables et aussi pour des cristaux obtenus à partir de phases semblables mais dans des conditions différentes, les distinctions entre matériaux gemmes naturels et synthétiques d'origines variées seront visualisées si des méthodes de détection appropriées sont utilisées. Afin de démontrer ceci, des images de réseau d'émeraudes naturelles et synthétiques, la topographie aux rayons X et la microtopographie de surface de diamants et émeraudes naturelles et synthétiques sont discutées à fins de comparaisons., Sunagawa Ichiro. Natural and synthetic gem materials, a comparison. In: Bulletin de Minéralogie, volume 104, 2-3, 1981. 12e assemblée générale de l'I.M.A. - Orléans – Juillet 1980. Première partie : croissance cristalline / Physique des minéraux / Microscopie électronique.

Transmission electron microscopy samples have been prepared from high quality, thick (> 100 mu m) CVD diamond films in order to undertake a detailed study of the regions adjacent to the columnar grain boundaries. Using both weak beam and strong matrix diffracted beams and also twin reflections in carefully chosen crystal orientations, it has been possible to show that the boundaries that appear defect-free at first sight are in fact associated with considerable defect densities of characteristic types. These defects have been analysed and the results are presented. An attempt is made to correlate these observations with the anisotropy and temperature dependence of the thermal conductivity of the films and also with their field-emission properties.

A mechanical mixture composed of carbon monofluoride and copper has given rise to diamond when one has exploded it in a closed tube by applying a shock wave from without. The pressure and the duration of this shock amounted to 0.6 mega-bars and 10⁻¹² seconds, respectively. Diamond prepared here has been detected crystallographically by means of electron diffraction., On a obtenu du diamant en provoquant, au moyen d'une onde de choc externe, l'explosion d'un mélange mécanique de monofluorure de carbone et de cuivre contenu dans un tube fermé. La pression produite par cette onde de choc est de 0,6 . 10⁶ bars pendant 10⁻¹² secondes. Le diamant ainsi synthétisé a été caractérisé cristallographiquement par diffraction des rayons X., Yamaguchi Shigeto, Setaka Nobuo. Essai de synthèse du diamant. In: Bulletin de Minéralogie, volume 103, 1, 1980. pp. 120-121.