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Sesto Fiorentino, Italy

Sassoli C.,University of Florence | Pini A.,University of Florence | Mazzanti B.,University of Florence | Quercioli F.,National Institute of Optics | And 5 more authors.
Journal of Molecular and Cellular Cardiology | Year: 2011

The possibility to induce myocardial regeneration by the activation of resident cardiac stem cells (CSCs) has raised great interest. However, to propose endogenous CSCs as therapeutic options, a better understanding of the complex mechanisms controlling heart morphogenesis is needed, including the cellular and molecular interactions that cardiomyocyte precursors establish with cells of the stromal compartment. In the present study, we co-cultured immature cardiomyocytes from neonatal mouse hearts with mouse bone marrow-derived mesenchymal stromal cells (MSCs) to investigate whether these cells could influence cardiomyocyte growth in vitro. We found that cardiomyocyte proliferation was enhanced by direct co-culture with MSCs compared with the single cultures. We also showed that the proliferative response of the neonatal cardiomyocytes involved the activation of Notch-1 receptor by its ligand Jagged-1 expressed by the adjacent MSCs. In fact, the cardiomyocytes in contact with MSCs revealed a stronger immunoreactivity for the activated Notch-intracellular domain (Notch-ICD) as compared with those cultured alone and this response was significantly attenuated when MSCs were silenced for Jagged-1. The presence of various cardiotropic cytokines and growth factors in the conditioned medium of MSCs underscored the contribution of paracrine mechanisms to Notch-1 up-regulation by the cardiomyocytes. In conclusions these findings unveil a previously unrecognized function of MSCs in regulating cardiomyocyte proliferation through Notch-1/Jagged-1 pathway and suggest that stromal-myocardial cell juxtacrine and paracrine interactions may contribute to the development of new and more efficient cell-based myocardial repair strategies. © 2011 Elsevier Ltd. Source

Toncian T.,Heinrich Heine University Dusseldorf | Amin M.,Heinrich Heine University Dusseldorf | Borghesi M.,Queens University of Belfast | Cecchetti C.A.,Queens University of Belfast | And 9 more authors.
AIP Advances | Year: 2011

This paper investigates the characteristic properties of a laser triggered micro-lens for focusing and energy selection of laser generated MeV proton and ion beams. Both experimental and computational studies that have been carried out leading to the understanding of the physical processes driving the micro-lens. After a one side irradiation of a hollow metallic cylinder a radial electric field develops inside the cylinder. Hot electrons generated by the interaction between laser pulse and cylinder wall spread inside the cylinder generating a plasma at the wall. This plasma expands into vacuum and sustains an electric field that acts as a collecting lens for proton or ion beams propagating axially through the cylinder. Various measurements including the reduction of the intrinsic beam divergence, the focusing quality, the energy selection and temporal response were carried out which contribute to the understanding of the lens properties. In addition, proton imaging was employed to study the electron transport inside the cylinder, revealing a transport along the wall surface. Each aspect studied experimentally is interpreted using 2D PIC and ray tracing simulations. A very good consistency between experimental and computational data was found. © 2011 Author(s). Source

Paci M.,Prato Hospital | Matulli G.,Centro Of Riabilitazione Sestese | Megna N.,University of Florence | Megna N.,National Institute of Optics | And 2 more authors.
Neuropsychological Rehabilitation | Year: 2011

Pusher behaviour (PB) reflects some misrepresentation of verticality. However, its neural mechanisms are still unclear. The aim of this pilot study is to assess the perception of the subjective visual vertical in patients with PB using an orientation discrimination task relying on a psychophysical forced-choice procedure. A sample of eight patients with post-stroke hemiplegia, three of whom with (PB+ group) and five without (PB-group) a clear PB, and 10 matched healthy subjects, was selected. All participants were assessed with an orientation discrimination task based on the objective Two-Alternatives Forced Choice (2AFC) procedure, in which observers are forced to report whether an oriented stimulus that was tilted off-vertical by a varying amount (but never vertical) was tilted clockwise or counterclockwise from vertical. Participants' ability in detecting the visual vertical was estimated by calculation of bias and threshold, which represent deviations of the subjective vertical from the physical vertical and the sensitivity to orientation offsets away from vertical, respectively. While there were no significant differences between groups in terms of bias, statistical analysis showed a significantly higher threshold in the PB+ group compared to both PB-and control groups. Results suggest that vertical misrepresentation might be due to the presence, in patients with PB, of a lower signal-to-noise ratio in coding systems. Implications for clinical practice are discussed. © 2011 Psychology Press, an imprint of the Taylor & Francis Group, an Informa business. Source

Megna N.,University of Florence | Megna N.,National Institute of Optics | Rocchi F.,University of Nottingham | Baldassi S.,University of Florence
Vision Research | Year: 2012

Visual attention is captured by transient signals in the periphery of the visual field, allowing enhanced perceptual representations in spatial tasks. However, it has been reported that the same cues impair performance in temporal tasks (e.g., Yeshurun, 2004; Yeshurun & Levy, 2003). This findings suggest that transient attention enhances the activity of slow, high-resolution channels, like parvocellular neurons, and/or shuts off faster channels better sensitive to low spatial frequencies, such as the ones of the magnocellular system. To test this idea, we have measured the spatio-temporal perceptive fields for transiently cued signals at various eccentricities using the classification images (CI) technique. At near eccentricities transient attention caused the perceptual templates to be sharper in space and characterized by much stronger high spatial frequency components. At the same time, they show a consistently larger temporal integration window. These effects of attention on perceptual filters are strongly reduced at far eccentricities and disappear when using longer target-cue lags. These data provide evidence in support of the parvocellular model of transient, exogenous attention, showing that in the presence of a well timed spatial cue observers rely on noisy evidence lasting longer and with finer spatial configurations. © 2011 Elsevier Ltd. Source

News Article | November 18, 2015
Site: http://phys.org/nanotech-news/

Noise is an issue in optical telecommunications. And findings means of controlling noise is key to physicists investigating light-emitting diodes or lasers. Now, an Italo-Iraqi team has worked on a particular type of light source, called the quantum dot light-emitting diode (QDLED). In a study published in the European Physical Journal D, Kais Al Namee from the National Institute of Optics, in Florence, Italy and colleagues, demonstrate that modulating bias current of the QDLED could lead to countering the noise. This, in turn, leads to stabilising such light sources, making them better suited for optical telecommunications.

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