Seeded and unseeded high order parametric down conversion

Spontaneous parametric down conversion (SPDC) has been one of the foremost tools in quantum optics for over five decades. Over that time it has been used to demonstrate some of the curious features that arise from quantum mechanics. Despite the success of SPDC, its higher-order analogues have never been observed, even though it has been suggested that they generate far more unique and exotic states than SPDC. An example of this is the emergence of non-Gaussian states without the need for post-selection. Here we calculate the expected rate of emission for nth-order SPDC with and without external stimulation (seeding). Focusing primarily on third-order parametric down-conversion (TOPDC), we estimate the photon detection rates in a rutile crystal, for both the unseeded and seeded regimes.Comment: 11 pages, 6 figure

Comment mesurer l'impact érosif des dynamiques de l'occupation du sol ? Approche pluridisciplinaire dans la vallée de la Choisille (Indre-et-Loire, France)

International audienceThe Choisille valley, in the north of Tours (37), has been a laboratory for a multidisciplinary experiment which was aimed at measuring the impact of human activities on soil erosion, conducted within the ECLIPSE II program. We propose a synthesis of the acquired knowledge about land use evolution based on archaeological, written and environmental data analyzed within a GIS. This information documents the settlement and landscape dynamics at different time and space scales, and provides a partial explanation to the variation of sediments recording within the Choisille valley.La vallée de la Choisille au nord de Tours (37) a été un laboratoire pour une expérience multidisciplinaire visant à mesurer l'impact des activités anthropiques sur l'érosion des sols, expérience réalisée dans le cadre du programme ECLIPSE II. Nous proposons la synthèse des connaissances acquises sur l'évolution de l'occupation du sol à partir des données archéologiques, écrites, planimétriques et environnementales analysées au sein d'un SIG. Ces informations documentent les dynamiques de l'habitat et du paysage à différentes échelles de temps et d'espace, et permettent en partie d'expliquer les variations de l'enregistrement sédimentaire au sein de la vallée de la Choisille

Travel and activity time allocation: An empirical comparison between eight cities in Europe

A study of daily time allocation to travel and out-of-home activity is conducted across eight European cities over three countries: France (Lyon, Grenoble, Strasbourg and Rennes), Switzerland (Geneva, Bern and Zurich) and Belgium (Brussels), based on individual travel survey data collected between 1997 and 2006. The effects of socio-demographic, spatial context, transport availability and city-specific variables are investigated thanks to the Cox proportional hazard model. The results indicate that socio-demographic characteristics and city (or country) specific effect play a major role while residential density and proximity to high level road or public transport networks have a very limited impact on time budgets for travel and out-of-home activities.Travel ; Activity ; Time allocation ; Cities ; Europe ; Duration model

Exponential decay for the damped wave equation in unbounded domains

We study the decay of the semigroup generated by the damped wave equation in an unbounded domain. We first prove under the natural geometric control condition the exponential decay of the semigroup. Then we prove under a weaker condition the logarithmic decay of the solutions (assuming that the initial data are smoother). As corollaries, we obtain several extensions of previous results of stabilisation and control

Melanin fate in the human epidermis: a re-assessment of how best to detect and analyze histologically

YesMelanin is the predominant pigment responsible for skin colour, and is synthesized by the melanocyte in the basal layer of the epidermis and then transferred to surrounding keratinocytes. Despite its optical properties, melanin is barely detectable in unstained sections of human skin. However, identification and localization of melanin is of importance for the study of skin pigmentation in health and disease. Current methods for the histologic quantification of melanin are suboptimal, and are associated with significant risk of misinterpretation. The aim of this study was to re-assess the existing literature, and to develop a more effective histological method of melanin quantification in human skin. Moreover, we confirm that Warthin-Starry (WS) stain provides a much more sensitive and more specific melanin detection method than the common-place Fontana-Masson (FM) stain. For example, WS staining sensitivity allowed the visualization of melanin even in very pale Caucasian skin that was missed by FM or Von Kossa (VK) stains. From our re-assessment of the histologyrelated literature we conclude that so-called ‘melanin dust’ is most likely an artefact of discoloration due to non-specific silver deposition in the stratum corneum. Unlike FM and VK, WS was not associated with this non-specific stratum corneum darkening, misinterpreted previously as ‘degraded’ or so-called ‘dust’ melanin. Finally, WS melanin particle counts were largely similar to manual counts by transmission electron microscopy, in contrast to both FM and VK. Together these findings allow us to propose a new histology/Image J-informed method for the accurate and precise quantification of epidermal melanin in skin

Occupation du sol et impact érosif dans la vallée de la Choisille (France, Indre-et-Loire). Approches croisées pour la restitution des paysages anciens.

International audienceThe Choisille catchment, a tributary of the Loire in the north of Tours, is used since 2003 as a common geographical framework for investigation of geologists and archaeologists teams with the aim of studying the main steps of land use of this space in the long term and the impact of human activities on soil erosion and sedimentation in wetlands during the Holocene. Archaeological fieldwalking surveys, analysis of medieval and modern written sources and sedimentological and palynological cores-drillings have been made. The comparison of these works highlights an anthropogenic forcing on sediment fluxes since the Bronze Age, with an increasing intensity since the Middle Ages, but also raises questions about discrepancies between the different types of sources. The limits of each discipline and the "blind spots" between them stress their complementarities and the necessity to cross them to approach the ancient realities.Le bassin-versant de la Choisille, affluent de la Loire au nord de Tours, sert depuis 2003 de cadre géographique commun d'investigation pour les équipes de géologues et d'archéologues dont le but est de mesurer, dans la longue durée, les principales phases d'occupation humaine de l'espace et l'impact des activités anthropiques sur l'érosion des sols et la sédimentation dans les zones humides durant l'Holocène. Des prospections archéologiques de surface, le dépouillement des sources écrites médiévales et modernes et des carottages sédimentologiques et palynologiques ont été réalisés. Le croisement de ces travaux met en lumière un forçage anthropique sur les flux sédimentaires dès l'Âge du Bronze, avec une intensité plus forte depuis le Moyen Âge, mais amène également à s'interroger sur les discordances observées entre les différents types de sources. Les limites propres à chaque discipline et les " angles morts " entre elles soulignent leur complémentarité et la nécessité de les multiplier pour approcher les réalités anciennes

"Hormone-refractory" prostate cancer : a putative new mechanism: the upside-down response to androgens

En aquest article volem revisar la diversitat dels mecanismes moleculars suposadament responsables del creixement independent d'andrògens del càncer de pròstata. Es demostra que alguns càncers de pròstata que escapen de la teràpia endocrinològica estan compostos per cèllules sensibles als andrògens. Ens centraremen els resultats del nostre laboratori i en els d'altres grups de recerca que suggereixen el mateix concepte nou: el comportament del càncer de pròstata refractari als andrògens està associat a una resposta invertida de les cèll. ules als andrògens. Hem observat un alentiment paradoxal en el creixement de diverses línies cell. ulars induït pels andrògens. Aquestes línies cell. ulars provenen de les cèll. ules LNCaP, ja sigui per evolució espontània o per cultiu crònic en un medi sense andrògens. La línia ARCaP (androgen-reverted carcinoma of the prostate) va ser establerta a partir de l'ascitis d'un pacient amb càncer de pròstata avançat. Els tumors que varen créixer a partir d'aquestes cèll. ules reverteixen, encara que transitòriament, en el tractament androgènic. Volem suggerir que la castració podria permetre la proliferació de les cèll. ules que eren paradoxalment alentides pels andrògens i que aquesta reacció invertida als andrògens podria ser el possible mecanisme pel qual el càncer de pròstata deixa de respondre a la teràpia hormonal. Aquests resultats aportarien unes bases racionals per a comprendre el tractament antiandrogènic intermitent.In this paper we survey the diversity of the molecular mechanisms suspected to be responsible for the androgen-independent growth of prostate cancer. It has been shown that some prostate cancers, which escape endocrine therapy, are composed of androgen-sensitive cells. We focus on the results from our laboratory and from a few others that suggest a new concept: that the androgen-refractory behavior of prostate cancer may be associated with an inverted response to androgens by cells. The proliferation of several cell lines was paradoxically slowed by androgens. In the afore-mentioned studies, a series of these cell lines arose from the LNCaP cell line, either spontaneously or after culturing them chronically in androgen-poor culture medium. The ARCaP (androgen-reverted carcinoma of the prostate) was established from the ascites of a patient with advanced prostate cancer. Usually, tumors grown from such cells regress, albeit transiently, under androgen treatment. It has been suggested that castration could allow the proliferation of cells that are paradoxically slowed by androgens and that the inverted response to androgens could possibly be a mechanism, by which prostate cancer escapes from endocrine therapy. These results provide the rationale for intermittent treatment