All-optical trion generation in single walled carbon nanotubes

We present evidence of all optical trion generation and emission in undoped single walled carbon nanotubes (SWCNTs). Luminescence spectra, recorded on individual SWCNTs over a large CW excitation intensity range, show trion emission peaks red-shifted with respect to the bright exciton peak. Clear chirality dependence is observed for 22 separate SWCNT species, allowing for determination of electron-hole exchange interaction and trion binding energy contributions. Luminescence data together with ultrafast pump probe experiments on chirality sorted bulk samples suggest that exciton-exciton annihilation processes generate dissociated carriers that allow for trion creation upon a subsequent photon absorption event.Comment: 13 pages, 4 figure

Luminescence of free-standing versus matrix-embedded oxide-passivated silicon nanocrystals: The role of matrix-induced strain:

We collect a large number of experimental data from various sources to demonstrate that free-standing (FS) oxide-passivated silicon nanocrystals (SiNCs) exhibit considerably blueshifted emission, by 200 meV on average, compared to those prepared as matrix-embedded (ME) ones of the same size. This is suggested to arise from compressive strain, exerted on the nanocrystals by their matrix, which plays an important role in the light-emission process; this strain has been neglected up to now as opposed to the impact of quantum confinement or surface passivation. Our conclusion is also supported by the comparison of low-temperature behavior of photoluminescence of matrix-embedded and free-standing silicon nanocrystals

Magnetic and luminescent coordination networks based on imidazolium salts and lanthanides for sensitive ratiometric thermometry

The synthesis and characterization of six new lanthanide networks [Ln(L)(ox)(H2O)] with Ln = Eu3+, Gd3+, Tb3+ , Dy3+ , Ho3+ and Yb3+ is reported. They were synthesized by solvo-ionothermal reaction of lanthanide nitrate Ln(NO3)(3)center dot xH(2)O with the 1,3-bis(carboxymethyl)imidazolium [HE] ligand and oxalic acid (H(2)ox) in a water/ethanol solution. The crystal structure of these compounds has been solved on single crystals and the magnetic and luminescent properties have been investigated relying on intrinsic properties of the lanthanide ions. The synthetic strategy has been extended to mixed lanthanide networks leading to four isostructural networks of formula [Tb1-xEux(L)(ox)(H2O)] with x = 0.01, 0.03, 0.05 and 0.10. These materials were assessed as luminescent ratiometric thermometers based on the emission intensities of ligand, Tb3+ and Eu3+ . The best sensitivities were obtained using the ratio between the emission intensities of Eu3+ (D-5(0) -> F-7(2) transition) and of the ligand as the thermometric parameter. [Tb0.97Eu0.03 (L)(ox)(H2O)] was found to be one of the best thermometers among lanthanide-bearing coordination polymers and metal-organic frameworks, operative in the physiological range with a maximum sensitivity of 1.38%.K-1 at 340 K

Particle Image Velocimetry: Status of Development and Examples of Application in Industrial Test Facilities

For the past few years particle image velocimetry (PIV) has been increasingly used for aerodynamic research and development. This is mainly due to the unique feature of the PIV technique, which allows the recording of a complete velocity field in a plane of the flow within a few microseconds. Thus, PIV provides information about unsteady flow fields, which is difficult to obtain with other experimental techniques. The short acquisition time and fast availability of data reduce the operational time, and hence cost, in large scale test facilities. Technical progress made in the last years allowed the PIV teams of the European research establishments on aeronautics to develop reliable, modular PIV systems for use in industrial wind tunnels. Development, and application of PIV as well as information exchange about PIV with industrial end-users have been considerably supported by EC. This paper will summarize the state-of-the-art of PIV by describing the basic features of a PIV system for application in wind tunnels and will present some results of recent PIV applications within EC funded projects such as EUROPIV 1 and 2, PivNet, APIAN, WAVENC, EUROWAKE, C-Wake, EUROLIFT, and HELIFLOW. Most of these results have been obtained by joint teams of different EREA members, European aeronautical industry and wind tunnels

Investigation of InGaN/GaN quantum wells for polariton laser diodes

III-nitride based microcavities (MCs) appear as one of the most promising candidates for the realization of room temperature (RT) polariton laser diodes. The present work focuses on the properties of low In content InGaN/GaN multiple quantum wells (MQWs) in terms of inhomogeneous broadening, exciton localization energy, and plastic strain relaxation. For a small number of such QWs, an inhomogeneous line broadening of 41 meV is reported, which is compatible with strong coupling regime requirements. By contrast when considering an InGaN/GaN MQW set, a high density of defects is reported, which is ascribed to plastic strain relaxation. From the evolution of the inhomogeneous line broadening as a function of the number of QWs probed by microphotoluminescence measurements, it is concluded that for the realization of polariton light-emitting devices the QW number should not go beyond 30 for MC structures grown on FS-GaN substrate relying on InGaN/GaN QWs with an indium content similar to 12-15% and thicknesses of 1.5-2 nm/3 nm for the wells and the barriers, respectively. (C) 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinhei

Successful Mitigation of Delayed Intestinal Radiation Injury Using Pravastatin is not Associated with Acute Injury Improvement or Tumor Protection

Purpose: To investigate whether pravastatin mitigates delayed radiation-induced enteropathy in rats, by focusing on the effects of pravastatin on acute cell death and fibrosis according to connective tissue growth factor (CTGF) expression and collagen inhibition. Methods and Materials: Mitigation of delayed radiation-induced enteropathy was investigated in rats using pravastatin administered in drinking water (30 mg/kg/day) 3 days before and 14 days after irradiation. The ileum was irradiated locally after surgical exteriorization (X-rays, 19 Gy). Acute apoptosis, acute and late histologic alterations, and late CTGF and collagen deposition were monitored by semiquantitative immunohistochemistry and colorimetric staining (6 h, 3 days, 14 days, 15 weeks, and 26 weeks after irradiation). Pravastatin antitumor action was studied in HT-29, HeLa, and PC-3 cells by clonogenic cell survival assays and tumor growth delay experiments. Results: Pravastatin improved delayed radiation enteropathy in rats, whereas its benefit in acute and subacute injury remained limited (6 h, 3 days, and 14 days after irradiation). Delayed structural improvement was associated with decreased CTGF and collagen deposition but seemed unrelated to acute damage. Indeed, the early apoptotic index increased, and severe subacute structural damage occurred. Pravastatin elicited a differential effect, protecting normal intestine but not tumors from radiation injury. Conclusion: Pravastatin provides effective protection against delayed radiation enteropathy without interfering with the primary antitumor action of radiotherapy, suggesting that clinical transfer is feasible. © 2007 Elsevier Inc. All rights reserved