X-ray radiation hardness and influence on blinking in Si and CdSe quantum dots

We study the effect of X-ray irradiation on the photoluminescence (PL) efficiency and intermittency (blinking) of single Si/SiO2 and CdSe/CdZnS quantum dots (QDs). Our results show that the PL efficiency of Si nanocrystals is not significantly altered up to a cumulative fluence of 1020 photons/m2 (corresponding to $300 kGy of absorbed dose in SiO2), while CdSe particles become completely dark already after a 17 times lower fluence. In both types of QDs, the statistical nature of blinking ON-and OFF-times remains unaltered: mono-exponential for Si and power-law for CdSe QDs. However, the evolution of the blinking parameters with absorbed dose depends on the choice of material. On average, both ON-and OFF-time constants do not vary in Si nanocrystals, highlighting their radiation hardness. Instead, the ON-time exponent increases while the OFF-time exponent decreases with the increasing dose for CdSe

Modulation Techniques for Three-Phase Three-Level NPC Inverters: a Review and a Novel Solution for Switching Losses Reduction and Optimal Neutral-Point Balancing in Photovoltaic Applications

A number of modulation strategies have been proposed in literature in the particular case of three-phase three-level NPC inverter, each one focusing on the optimization of specific aspects and performance of the converter. Nevertheless a comprehensive analysis of state-of-art techniques and their specific features suitable for a photovoltaic (PV) applications is still missing, such a study being highly desirable. Both carrier-based and space vector modulation techniques are analyzed in this paper, highlighting specific features and limitations, especially related to PV applications. Basic issues are considered and compared among modulation strategies, namely: switching losses, low-frequency oscillations of the neutral-point (NP) voltage, total harmonic distortion (THD) and weighted total harmonic distortion (WTHD) of the phase currents and line voltages, dynamic response of the neutral-point voltage control loop under imbalance conditions and modulation algorithm complexity. A hybrid modulation strategy assisted by an optimal neutral-point voltage controller is then proposed aiming at both the reduction of the switching losses with a limited deterioration of the output voltage/current quality and fast dynamics control of the neutral point voltage. Those features allow the development of reduced dc bus capacitance PV inverters with optimized efficiency and quality of the output waveforms. Simulation and experimental results based on a TMS320F28069 DSP controller and a PV inverter are presented to confirm the effectiveness of the proposal

Conservation tillage reduces the negative impact of urbanisation on carabid communities

Urban sprawl has been widely recognised as major cause of biodiversity decline across multiple taxonomic levels. Nevertheless, comprehensive studies investigating the effects of landscape urbanisation and farming practices on arthropod biodiversity in agroecosystems are still scarce. We explored the combined effect of urbanisation in the landscape and tillage management (conservation vs. conventional tillage) on predatory carabid beetle communities (Coleoptera: Carabidae) in 10 pairs of winter cereal fields in the agricultural landscape of Udine province (north-east Italy). Urbanisation (at 750 m scale) strongly decreased carabid activity density, species richness, functional richness and increased functional divergence. We, however, found an interaction between tillage system and the proportion of urban areas in the landscape, i.e., the negative effects of urbanisation on carabid communities were more evident in the fields managed under conventional tillage, while conservation tillage supported more diverse (both taxonomically and ecologically) and abundant beetle communities also in highly urbanised landscapes. We also found that different functional groups differently responded to tillage management. The better local habitat quality provided by conservation tillage may mitigate the negative effects of urbanisation on carabid communities. Our study stresses the importance of considering both local management and landscape composition when planning strategies to support farmland biodiversity

Natural leukocyte interferon alfa for the treatment of chronic viral hepatitis in heart transplant recipients

Background. A more rapid and aggressive course of hepatitis B virus (HBV)-related and hepatitis C virus (HCV)-related infection in organ transplant recipients has been described. Interferon alfa is the most accepted drug for treating HBV and HCV chronic infections. However, the use of interferon alfa-N3 has been contraindicated in heart transplant (HTx) recipients because of the hypothesized greater risk of triggering acute cellular rejection. The aim of this clinical pilot study was to evaluate tolerability, safety, and efficacy of natural leukocyte interferon alfa in the treatment of chronic HBV and HCV in HTx recipients. Methods. Seven HTx recipients were enrolled in the study: two with HBV, four with HCV, and one with combined HBV-HCV chronic infection. The patients had a mean follow-up after heart transplantation of 8.5±3 years, before starting interferon alfa-N3 treatment at a dose of 6 MU three times per week, intramuscularly for 12 months. Results. All patients completed the treatment with no major side effects. No unexpected episodes of acute cellular rejection were observed during the treatment. Mean aminotransferase serum levels were significantly lower than before transplantation at 3 (P<0.03), 6 (P<0.02), and 12 (P<0.02) months of treatment and at the 12-month follow-up (P<0.02). A complete and sustained response was achieved in all subjects with HBV-related chronic hepatitis, whereas sustained virologic response was observed in one of four HCV patients. Conclusions. The preliminary data emerging from our study indicate that natural leukocyte interferon alfa-N3 can be safely administered in HTx recipients with chronic HBV or HCV viral hepatitis. Further studies with larger numbers of patients are needed to assess the efficacy of interferon alfa-N3 on HCV virologic response