Precise measurement of Γ(K→e ν(γ))/Γ(K→μ ν(γ)) and study of K→e ν γ

We present a precise measurement of the ratio R _K =Γ(K→e ν(γ))/Γ(K→μ ν(γ)) and a study of the radiative process K→e ν γ, performed with the KLOE detector. The results are based on data collected at the Frascati e ⁺ e ^? collider DAΦNE for an integrated luminosity of 2.2 fb^?1. We find R _K =(2.493±0.025_stat±0.019_syst)×10^?5, in agreement with the Standard Model expectation. This result is used to improve constraints on parameters of the Minimal Supersymmetric Standard Model with lepton flavor violation. We also measured the differential decay rate dΓ(K→e ν γ)/dE _γ for photon energies 10<E _γ < 250 MeV. Results are compared with predictions from theory.     

Pulse EPR Methods for Studying Chemical and Biological Samples Containing Transition Metals

This review discusses the application of pulse EPR to the characterization of disordered systems, with an emphasis on samples containing transition metals. Electron nuclear double‐resonance (ENDOR), electron‐spin‐echo envelope‐modulation (ESEEM), and double electron–electron resonance (DEER) methodologies are outlined. The theory of field modulation is outlined, and its application is illustrated with DEER experiments. The simulation of powder spectra in EPR is discussed, and strategies for optimization are given. The implementation of this armory of techniques is demonstrated on a rich variety of chemical systems: several porphyrin derivatives that are found in proteins and used as model systems, otherwise highly reactive aminyl radicals stabilized with electron‐rich transition metals, and nitroxide–copper–nitroxide clusters. These examples show that multi‐frequency continuous‐wave (CW) and pulse EPR provides detailed information about disordered systems.     

Measurement of turbidity parameters (AMA-MILANO 93 first results)

Summary In this paper we propose to show some sun photometry results obtained by the MILANO 93 experiment of the AMA (Aree Metropolitane ed Ambiente) Strategic Project of the Italian National Research Council (CNR). The experiment was carried out between the 8th and the 20th of February 1993. The aerosol optical thickness is compared with similar results obtained at Modena (a town in the Po Valley); the meteorological situation is also considered. The measurements were taken at seven different locations across the metropolitan area of Milan, beginning at the Monza racetrack, about 20 km North of Milan, and finishing at Lacchiarella, a rural village about 20 km South of Milan.     

Micro-Raman analysis of titanium oxide/carbon nanotubes-based nanocomposites for hydrogen sensing applications

Titanium oxide/carbon nanotubes-based nanocomposites (TiO₂/CNTs, prepared by sol-gel method, and 2%Pt/TiO₂/CNTs, obtained by wetness impregnation of the TiO₂/CNTs base material with a solution of platinum acetylacetonate) have been recently used as active layer in hydrogen sensing devices at near room temperature, obtaining quite different responsiveness. The microstructure of these hybrid materials is here systematically investigated by micro-Raman spectroscopy at 2.41 eV. The results show that regardless of the nominal C/Ti molar ratio (3.6 or 17.0) only the anatase phase of titania is formed. Theoretical calculations demonstrate that phonon confinement is fully responsible for the large blue-shift (∼10 cm⁻¹) and broadening (∼20 cm⁻¹) of the lowest-frequency Raman mode with respect to bulk anatase. The average size (4.3-5.0 nm) of TiO₂ crystallites, resulting from Raman spectra fitting, is in excellent agreement with those inferred from transmission electron microscopy and X-ray diffraction measurements.     

Statistics of some synthetic parameters of vertical profiles of pressure and temperature obtained by one year of ECMWF's analysis over Europe

Summary In this paper monthly distributions of synthetic parameters of vertical profiles of temperature and pressure over Europe are shown. The data have been obtained by fits of one-year data analysis of the ECMWF model. In particular, distributions of lapse rates, distributions of heights of the layers and distributions of temperature and dry-air pressure of the lower level are reported. Within the precision of the input data and by disregarding the boundary layer, a finer subdivision of a layered troposphere and lower stratosphere has been obtained. Paper presented at the IX Congresso del Gruppo Nazionale per la Fisica dell'Atmosfera e dell'Oceano, June 8–10, 1992, Rome.     

«Buckingham» approximants to physical laws

Summary The typical problem is addressed of system and process modelling depending on a large number of variables. Demonstration is given that the number of independent variables can be dramatically reduced, by a modified application of Buckingham's theorem of dimensional analysis, resulting in a simplified formulation of the problem in terms of a limited number of dimensionless arguments. This simplified formulation eventually leads, by interpolation of numerical data, to the derivation of practical approximants to the physical laws governing the system or process. This approach is demonstrated, in case of electron scattering, through a general layer in the elastic regime, as modelled by Monte Carlo methods. In particular, a single dimensionless quality factor is introduced, allowing remarkable simplification both in forward and backward scattering analysis. Hence, Buckingam approximants are derived, effectively describing the scattering by universal laws, applicable to all elements of the periodic table and all variations of electron energy and layer thickness, in the ranges 5 to 150 keV and 1 to 3000 nm. The proposed method may be considered as a physical approximation, compared to purely mathematical methods, such as for example Padé approximants. As a consequence, the method is understandably highly effective, and may be extensively applied to all systems and processes susceptible to being described by mathematical modelling.     

Surface temperature and emissivity from NOAA images

Summary A procedure to determine the surface temperature from images taken by AVHRR (advanced very high resolution radiometer) on board NOAA11 satellite is described in this paper. The importance of the emissivity parameter to estimate the surface temperature and the possibility to compute both temperature and emissivity maps from the two thermal infrared channels of the AVHRR is shown. Due to the relevance of its scientific content, this paper has been given priority by the Journal Direction.