The apparent shape of the "Str\"omgren sphere'' around the highest-redshift QSOs with Gunn-Peterson troughs

Although the highest redshift QSOs (z>6.1) are embedded in a significantly neutral background universe (mass-averaged neutral hydrogen fraction >1%) as suggested by the Gunn-Peterson absorption troughs in their spectra, the intergalactic medium in their vicinity is highly ionized. The highly ionized region is generally idealized as spherical and called the Str\"omgren sphere. In this paper, by combining the expected evolution of the Str\"omgren sphere with the rule that the speed of light is finite, we illustrate the apparent shape of the ionization fronts around the highest redshift QSOs and its evolution, which depends on the age, luminosity evolution, and environment of the QSO (e.g., the hydrogen reionization history). The apparent shape may systematically deviate from a spherical shape, unless the QSO age is significantly long compared to the hydrogen recombination process within the ionization front and the QSO luminosity evolution is significantly slow. Effects of anisotropy of QSO emission are also discussed. The apparent shape of the "Str\"omgren sphere'' may be directly mapped by transmitted spectra of background sources behind or inside the ionized regions or by surveys of the hyperfine transition (21cm) line emission of neutral hydrogen.Comment: 7 pages, 5 figures; discussion on effects of anisotropy of QSO emission expanded; ApJ in pres

Dynamiques des Entreprises Agroalimentaires (EAA) du Languedoc-Roussillon : évolutions 1998-2003. Programme de recherche PSDR 2001-2006 financé par l'Inra et la Région Languedoc-Roussillon

It was the title chosen in January 2004 for the 12 pages of the "Agreste" restitution of the primary results obtained through this second investigation, to the partners and interviewed firms, which was intended to question the evolutions of the regional agro-food sphere over 5 years (1998-2003). Let us recall that the survey of 1998 was implemented just after the 1992-1995 crisis, and therefore reflected a certain optimism. The situation is far from being similar in 2003, whereas a new crisis has been hitting the global economy since 2001 and, consequently, the consumer has become more cautious. The principal lessons of this investigation appear to be of three orders: 1. Reduction in the number of establishments and firms. Many establishments disappeared (404 out of the 1.384 listed in 1998), but one should also note many creations (194), confirming a real dynamism of the regional agro-food sector. The sales progression, with total sales now reaching nearly 8 billion d'euros, even if it is not very high, implies a concentration of the offer, which is hardly surprising in times of crisis. The good news, under these conditions, is the total resistance of the total employment still reaching around 25.000 full time equivalents. 2. The driving effect on the regional agriculture is very important (nearly 50% of raw agricultural goods purchases come from the area), and 70% of the interviewed chief executives declare to primarily buy from regional producers and suppliers. The added value created by these companies, which is upstream induced, as much in agriculture as in industrial supplies or as in services, is undoubtedly, except perhaps for the public works and construction sectors, the most important among the regional industries. 3. More and more regional companies are becoming "subcontractors", without real decision-making power concerning their future. This relative `forfeiture' of their independence is initially due to a governance which flees the area: the repurchases of regional companies of average size by larger national or international firms often result in the suppression of any human and decisional structure but for production in the region. The increasing dependence on the discount distribution circuits, the companies `privately owned brands' substitution by `low prices' and `buyers own brands' products, proceed from the same weakening of the regional `governance'. On the basis of the principle that the current markets are saturated and the prices of the `standard' current products can only continue to drop, it thus remains the most difficult to achieve: finding new markets and/or finding new products or services. With the current stagnation coming to an end (at least if one believes in these last months economic indicators), an agro-food dynamic and durable revival in Languedoc Roussillon can, according to our understanding, only come from the reinforcement of three strategic orientations in the near future: to innovate more, to better defend its private brands and to export more. The articles presented in this 'research journal' explore these orientations, put forward managing implications resulting from the observed results and propose some directions for future research. ...French Abstract : Tel fut le titre choisi en janvier 2004 pour le 12 pages de restitution "Agreste", auprès des partenaires et entreprises, des premiers résultats obtenus par cette deuxième enquête destinée à sonder l'évolution sur 5 ans (1998-2003) de la sphère agroalimentaire régionale. Rappelons que l'enquête de 1998 se situait en 'sortie' de la crise de 1992-1995 et reflétait un certain optimisme. Il n'en est pas de même en 2003, alors qu'une nouvelle crise rend l'économie globale plutôt atone depuis 2001, et, par voie de conséquence, le consommateur plus frileux. Les principales leçons de l'enquête nous semblent être de trois ordres : 1. Diminution du nombre d'établissements et d'entreprises. Beaucoup d'établissements ont disparu (404 sur les 1 384 recensés en 1998), mais on constate aussi de nombreuses créations (194), confirmant un réel dynamisme de l'agroalimentaire régional. La progression du CA à près de 8 milliards d'euros, même si elle n'est pas très forte, implique un phénomène de concentration de l'offre, qui n'est guère surprenant en temps de crise. La bonne nouvelle, dans ces conditions, c'est le maintien global de l'emploi dans ces entreprises autour de 25 000 équivalents temps plein. 2. L'effet d'entraînement sur l'agriculture régionale est très important (près de 50% des achats de matières premières agricoles proviennent de la région) et 70% des chefs d'entreprise déclarent s'approvisionner auprès de producteurs et fournisseurs régionaux. La valeur ajoutée créée par les entreprises, et celle qui est induite en amont, tant dans l'agriculture que dans l'agro-industrie ou les services est sans doute, à l'exception peut-être du secteur des travaux publics et de la construction, la plus importante de l'industrie régionale. 3. Toujours plus d'entreprises régionales deviennent des " sous-traitants ", sans réel pouvoir de décision concernant leur devenir. Cette relative 'déchéance' de leur libre arbitre tient d'abord à une gouvernance qui fuit la région : les rachats d'entreprises régionales de taille moyenne par des firmes de plus grande taille se traduit souvent par la suppression de toute structure humaine et décisionnelle autre que de production en région. La dépendance croissante envers les circuits de discount, la substitution des 'marques propres' des entreprises par des produits 'premiers prix' et 'sous marque de distributeur', procède du même affaiblissement de la gouvernance régionale. Partant de ce principe que les marchés actuels sont saturés et que les prix des produits 'standards' actuels ne peuvent que continuer de baisser, il reste donc le plus difficile à accomplir : trouver de nouveaux débouchés et/ou trouver de nouveaux produits ou services. A l'aube d'une sortie de l'actuel marasme (du moins si l'on en croit les indicateurs économiques de ces derniers mois), une relance durable de la dynamique agroalimentaire du Languedoc Roussillon ne peut donc, à notre sens, provenir que du renforcement de trois orientations stratégiques porteuses d'avenir : innover plus, mieux défendre ses marques et exporter plus. Les articles présentés dans ce cahier de recherche explorent ces orientations, mettent en exergue les implications managériales issues des résultats observés et présentent les pistes de recherche future.CORPORATE STRATEGY; INNOVATION; SME; FOOD INDUSTRY; BRAND; FINANCING; GROWTH; PERFORMANCE; QUALITY; TERROIR; GOVERNANCE; WINE PROCESSING INDUSTRY; NICT; LANGUEDOC ROUSSILLON

Cooperative performance measurement proposal (a test with the cooperfic© tool for wine cooperatives in Languedoc-Roussillon)

Purpose: French wine cooperatives show differences of corporate objectives, but also common ones with private wine merchants, as they face a common economic environment. The traditional controlling and financial models do not seem adequate to measure ‘sustainable social economy’ performances advocated by the cooperatives’ philosophy. The main difficulty is that their specific corporate governance introduces competition between short term maximum payments to their grape suppliers-patrons and long term investment potentials. How, therefore, facing this “cooperative dilemma”, should they balance these conflicting objectives, and which performance measurement specificities should wine cooperatives adopt? Design/methodology: In order to try and answer this question, the design of an adapted data base appears to be necessary. It should take into account the apparent antinomy of the cooperatives’ short term and long term objectives, in the context of an economically sustainable development. An original economic and financial measurement model is proposed, and we test it with COOPERFIC?, a decision-aid tool for wine cooperatives, based upon a specially constructed data base in Languedoc-Roussillon. Findings: The exploratory results obtained from the test of an original performance measurement model on an ad hoc sample of wine cooperatives lead to new insights into cooperative performance and to some useful guidelines in terms of cooperative governance. Results show how the conflict between their short term and long term performances could be balanced, in order for this specific type of firm to reach its economic and social objectives Practical implications: A conjoint short and long term economic indicators approach illustrates the necessary balance in the cooperative governance, and constitutes a performance measurement model answering some of these wine cooperatives’ Board and management questions ...French Abstract : Propos: Les caves coopératives françaises font apparaître des points de divergence, mais aussi de convergence avec les négociants en vin, en matière d’objectifs d’entreprise, dans la mesure où elles font face au même environnement économique. Toutefois, les modèles traditionnels financiers et de contrôle de gestion ne semblent pas adaptés à la mesure des performances d’une économie sociale durable, dont les valeurs sont portées par la philosophie coopérative. La principale difficulté réside dans le fait que leur mode de gouvernance spécifique entraîne un conflit permanent entre la rémunération maximale à court terme des vignerons coopérateurs et les capacités d’investissement à long terme. Aussi, face à ce « dilemme coopératif », comment les entreprises coopératives viticoles doivent-elles concilier ces objectifs conflictuels et quels types de mesures de performance spécifiques devraient-elles adopter ? Design/méthodologie: Afin d’arriver à répondre à cette double question, la conception d’une base de données spécifique apparaît nécessaire. Elle se doit de prendre en compte l’apparente antinomie des objectifs à court terme et à long terme des coopératives, dans le cadre d’un développement économique durable. Un modèle de mesure de performance économique et financière est ici proposé et testé à l’aide de l’outil d’aide à la décision COOPERFIC?, spécifique aux caves coopératives du Languedoc-Roussillon. Résultats: Les résultats exploratoires provenant du test d’un modèle original de mesure de la performance sur un échantillon ad hoc de caves coopératives conduit à de nouvelles perspectives en matière de performance coopérative, ainsi qu’à des conseils utiles ayant trait à la gouvernance. Ces résultats montrent la façon dont le conflit entre performances à court terme et à long terme pourrait être maîtrisé en vue d’atteindre les objectifs économiques et sociaux de ce type particulier d’entreprise. Implications managériales: Une approche conjointe des indicateurs économiques à court et long terme illustre le nécessaire équilibre à trouver en matière de gouvernance coopérative et constitue un modèle de mesure de la performance répondant à un certain nombre de questions relatives au conseil d’administration et au management général des coopératives.WINE COOPERATIVES; GOVERNANCE; PERFORMANCE MEASUREMENT; INDICATORS; LANGUEDOC ROUSSILLON; FRANCE

Self-cleaning on a higher order mode in ytterbium-doped multimode fiber with parabolic profile

We experimentally demonstrate polarization-dependent Kerr spatial beam self-cleaning into the LP11 mode of an Ytterbium-doped multimode optical fiber with parabolic gain and refractive index profiles

Interplay of Kerr and Raman beam cleaning with a multimode microstructure fiber

We experimentally study the competition between Kerr beam self-cleaning and Raman beam cleanup in a multimode air-silica microstructure optical fiber. Kerr beam self-cleaning of the pump is observed for a certain range of input powers only. Raman Stokes beam generation and cleanup lead to both depletion and degradation of beam quality for the pump. The interplay of modal four-wave mixing and Raman scattering in the infrared domain lead to the generation of a multimode supercontinuum ranging from 500 nm up to 1800 nm

Spatiotemporal Characterization of Supercontinuum Extending from the Visible to the Mid-Infrared in Multimode Graded-Index Optical Fiber

We experimentally demonstrate that pumping a graded-index multimode fiber with sub-ns pulses from a microchip Nd:YAG laser leads to spectrally flat supercontinuum generation with a uniform bell-shaped spatial beam profile extending from the visible to the mid-infrared at 2500\,nm. We study the development of the supercontinuum along the multimode fiber by the cut-back method, which permits us to analyze the competition between the Kerr-induced geometric parametric instability and stimulated Raman scattering. We also performed a spectrally resolved temporal analysis of the supercontinuum emission.Comment: 5 pages 7 figure

Control of near-infrared supercontinuum bandwidth by adjusting pump pulse duration

We experimentally and numerically investigated the impact of input pump pulse duration on the near-infrared bandwidth of supercontinuum generation in a photonic crystal fiber. We continuously stretched the temporal duration of the input pump laser (centered at 1030 nm) pulses from 500 fs up to 10 ps, while keeping fixed the pump peak power. We observed that the long-wavelength edge of the supercontinuum spectrum is increased by 200 nm as the pump pulse duration grows from 500 fs to 10 ps. We provide a quantitative fit of the experimental results by means of numerical simulations. Moreover, we have explained the observed spectral broadening enhancement induced by pump pulse energy by developing an approximate yet fully analytical model for soliton energy exchange through a series of collisions in the presence of stimulated Raman scattering