Phyto-oestrogens and breast cancer chemoprevention

Phytoestrogens are polyphenol compounds of plant origin that exhibit a structural similarity to the mammalian steroid hormone 17β-oestradiol. In Asian nations the staple consumption of phyto-oestrogen-rich foodstuffs correlates with a reduced incidence of breast cancer. Human dietary intervention trials have noted a direct relationship between phyto-oestrogen ingestion and a favourable hormonal profile associated with decreased breast cancer risk. However, these studies failed to ascertain the precise effect of dietary phyto-oestrogens on the proliferation of mammary tissue. Epidemiological and rodent studies crucially suggest that breast cancer chemoprevention by dietary phyto-oestrogen compounds is dependent on ingestion before puberty, when the mammary gland is relatively immature. Phyto-oestrogen supplements are commercially marketed for use by postmenopausal women as natural and safe alternatives to hormone replacement therapy. Of current concern is the effect of phyto-oestrogen compounds on the growth of pre-existing breast tumours. Data are contradictory, with cell culture studies reporting both the oestrogenic stimulation of oestrogen receptor-positive breast cancer cell lines and the antagonism of tamoxifen activity at physiological phyto-oestrogen concentrations. Conversely, phyto-oestrogen ingestion by rodents is associated with the development of less aggressive breast tumours with reduced metastatic potential. Despite the present ambiguity, current data do suggest a potential benefit from use of phyto-oestrogens in breast cancer chemoprevention and therapy. These aspects are discussed

FOCUSED DROPLET BEAM FROM A GOLD LIQUID METAL ION SOURCE

A gold LMIS has been used in the charged droplet emission mode with a single lens focusing column operating at 20 kV beam voltage to achieve a deposit size at the target of 2.3 to 6.0 depending on the exposure time. The net mass deposit rate maximized at 1.5 µm3/s. From the focusing characteristics an energy spread of 50 V and an energy deficit of 350 to 500 V could be inferred for the charged droplet beam

THE EFFECT OF CARBON BEARING GASES AND SECONDARY ELECTRON BOMBARDMENT ON A LIQUID METAL ION SOURCE

Nous montrons que l'influence de l'atmosphère résiduelle sur le bruit et la durée de vie des sources d'ions à métal liquide (LMIS) est significative lorsque des électrons secondaires frappent la surface de l'émetteur. Nous proposons une méthode de suppression des électrons secondaires lors de la conception d'un canon LMIS.The influence of residual gases on the noise and life time of liquid metal ion sources (LMIS) has been found to be significant if secondary electrons impinge upon the emitter surface. A straight forward method of preventing electron bombardment of the LMIS in a ion gun structure is shown

Scaling size of the interplay between quantum confinement and surface related effects in nanostructured silicon

International audienceSi nanocrystals (NCs) embedded in a SiO2 matrix provide an exemplar curved nanostructured interface to evidence the competition between surface states and quantum confinement (QC) effects. The study of the energy band alignment as a function of NCs size (<5 nm) clarifies their interplay and identifies, with subnanometric resolution, three different regimes. Primarily QC affects the conduction band, then surface effects pin the conduction states, and finally QC starts to modify the valence band. A way to study how different nanoscale configurations compete with pure quantum properties is established

3D design of Ag nanocrystals embedded in dielectrics for imaging and spectroscopy of deposits on surfaces

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Plasmon-resonant Raman spectroscopy in metallic nanoparticles: Surface-enhanced scattering by electronic excitations

cited By 7International audienceSince the discovery of surface-enhanced Raman scattering (SERS) 40 years ago, the origin of the "background" that is systematically observed in SERS spectra has remained questionable. To deeply analyze this phenomenon, plasmon-resonant Raman scattering was recorded under specific experimental conditions on a panel of composite multilayer samples containing noble metal (Ag and Au) nanoparticles. Stokes, anti-Stokes, and wide, including very low, frequency ranges have been explored. The effects of temperature, size (in the nm range), embedding medium (SiO2, Si3N4, or TiO2) or ligands have been successively analyzed. Both lattice (Lamb modes and bulk phonons) and electron (plasmon mode and electron-hole excitations) dynamics have been investigated. This work confirms that in Ag-based nanoplasmonics composite layers, only Raman scattering by single-particle electronic excitations accounts for the background. This latter appears as an intrinsic phenomenon independently of the presence of molecules on the metallic surface. Its spectral shape is well described by revisiting a model developed in the 1990s for analyzing electron scattering in dirty metals, and used later in superconductors. The gs factor, that determines the effective mean-free path of free carriers, is evaluated, gsexpt=0.33±0.04, in good agreement with a recent evaluation based on time-dependent local density approximation gstheor=0.32. Confinement and interface roughness effects at the nanometer range thus appear crucial to understand and control SERS enhancement and more generally plasmon-enhanced processes on metallic surfaces

Innovative OxRAM nanomemories with indium oxide nanocrystals fabricated by ultra low energy ion implantation

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