Terahertz processes in carbon nanotubes

Copyright 2010 Society of Photo-Optical Instrumentation Engineers. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.We investigated several proposals utilizing the unique electronic properties of carbon nanotubes (CNTs) for a broad range of applications to THz optoelectronics, including THz generation by Cerenkov-type emitters based on carbon nanotubes and by hot electrons in quasimetallic nanotubes, frequency multiplication in chiral-nanotube-based superlattices controlled by a transverse electric field, and THz radiation detection and emission by armchair nanotubes in a strong magnetic field. Dispersion equations of the electron beam instability and the threshold conditions of the stimulated emission have been derived and analyzed, demonstrating realizability of the nanotube-based nanoFEL at realistic parameters of nanotubes and electronic beams

Pre-meal tomato (Lycopersicon esculentum) intake can have anti-obesity effects in young women?

The effect of pre-meal tomato intake in the anthropometric indices and blood levels of triglycerides, cholesterol, glucose, and uric acid of a young women population (n = 35, 19.6 ± 1.3 years) was evaluated. During 4 weeks, daily, participants ingested a raw ripe tomato (∼90 g) before lunch. Their anthropometric and biochemical parameters were measured repeatedly during the follow-up time. At the end of the 4 weeks, significant reductions were observed on body weight (−1.09 ± 0.12 kg on average), % fat (−1.54 ± 0.52%), fasting blood glucose (−5.29 ± 0.80 mg/dl), triglycerides (−8.31 ± 1.34 mg/dl), cholesterol (−10.17 ± 1.21 mg/dl), and uric acid (−0.16 ± 0.04 mg/dl) of the participants. The tomato pre-meal ingestion seemed to interfere positively in body weight, fat percentage, and blood levels of glucose, triglycerides, cholesterol, and uric acid of the young adult women that participated in this study.info:eu-repo/semantics/publishedVersio

Multi-frequency multimode modulated technology as a clean, fast, and sustainable process to recover antioxidants from a coffee by-product

Coffee chaff is a major coffee roasting by-product that could be valued as a source of antioxidants. In the present work, we compared classic, but optimized, solid-liquid extraction conditions with a new concept, namely, the Multi-frequency Multimode Modulated (MMM) vibration technique. The extracts obtained by both methods were analysed and compared in relation to several parameters, namely, phenolics profile (by HPLC/DAD), 5-caffeoylquinic acid content, total phenolics content, and Ferric Reducing Antioxidant Power. Compared to an optimized solid-liquid extraction (using a hydroethanolic solvent (1:1) at 40 °C for 60 min), the acoustic probe allowed a higher recovery of antioxidants in only 10 min and using only water as extraction solvent. Moreover, the effects that arise from the acoustic cavitation in the medium allowed the suppression of the sample preparation step (grinding). These results show that this type of technology can be of high interest to recover antioxidants from natural matrices, in a green, fast and very efficient way.info:eu-repo/semantics/publishedVersio

Nutritional, chemical and antioxidant/pro-oxidant profiles of silverskin, a coffee roasting by-product

Coffee silverskin (a coffee roasting by-product) contains high amounts of dietary fibre (49% insoluble and 7% soluble) and protein (19%). Potassium (∼5 g/100 g), magnesium (2 g/100 g) and calcium (0.6 g/100 g) are the major macrominerals. The vitamin E profile of silverskin comprises α-tocopherol, β-tocopherol, ɣ-tocopherol, δ-tocopherol, β-tocotrienol, ɣ-tocotrienol, and δ-tocotrienol. The fatty acid profile is mainly saturated (C16:0 and C22:0), but the total amount of fat is low (2.4%). Caffeine (1.25 g/100 g), chlorogenic acid (246 mg/100 g), and 5-hydroxymethylfurfural (5.68 mg/100 g) are also present in silverskin. Total phenolics and flavonoids are partially responsible for the in vitro antioxidant activity. Silverskin extracts protected erythrocytes from oxidative AAPH- and H2O2-induced hemolysis, but at high concentrations a pro-oxidant effect on erythrocyte morphology was observed.info:eu-repo/semantics/publishedVersio

Cosmic Microwave Background Anisotropies from Scaling Seeds: Global Defect Models

We investigate the global texture model of structure formation in cosmogonies with non-zero cosmological constant for different values of the Hubble parameter. We find that the absence of significant acoustic peaks and little power on large scales are robust predictions of these models. However, from a careful comparison with data we conclude that at present we cannot safely reject the model on the grounds of present CMB data. Exclusion by means of galaxy correlation data requires assumptions on biasing and statistics. New, very stringent constraints come from peculiar velocities. Investigating the large-N limit, we argue that our main conclusions apply to all global O(N) models of structure formation.Comment: LaTeX file with RevTex, 27 pages, 23 eps figs., submitted to Phys. Rev. D. A version with higher quality images can be found at http://mykonos.unige.ch/~kunz/download/lam.tar.gz for the LaTeX archive and at http://mykonos.unige.ch/~kunz/download/lam.ps.gz for the compiled PostScript fil

Study of Tau-pair Production in Photon-Photon Collisions at LEP and Limits on the Anomalous Electromagnetic Moments of the Tau Lepton

Tau-pair production in the process e+e- -> e+e-tau+tau- was studied using data collected by the DELPHI experiment at LEP2 during the years 1997 - 2000. The corresponding integrated luminosity is 650 pb^{-1}. The values of the cross-section obtained are found to be in agreement with QED predictions. Limits on the anomalous magnetic and electric dipole moments of the tau lepton are deduced.Comment: 20 pages, 9 figures, Accepted by Eur. Phys. J.

Evidence for an Excess of Soft Photons in Hadronic Decays of Z^0

Soft photons inside hadronic jets converted in front of the DELPHI main tracker (TPC) in events of qqbar disintegrations of the Z^0 were studied in the kinematic range 0.2 < E_gamma < 1 GeV and transverse momentum with respect to the closest jet direction p_T < 80 MeV/c. A clear excess of photons in the experimental data as compared to the Monte Carlo predictions is observed. This excess (uncorrected for the photon detection efficiency) is (1.17 +/- 0.06 +/- 0.27) x 10^{-3} gamma/jet in the specified kinematic region, while the expected level of the inner hadronic bremsstrahlung (which is not included in the Monte Carlo) is (0.340 +/- 0.001 +/- 0.038) x 10^{-3} gamma/jet. The ratio of the excess to the predicted bremsstrahlung rate is then (3.4 +/- 0.2 +/- 0.8), which is similar in strength to the anomalous soft photon signal observed in fixed target experiments with hadronic beams.Comment: 37 pages, 9 figures, Accepted by Eur. Phys. J.