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AbstractThe optical energy‐loss function (ELF) of Au and Al, obtained from experiments, is extended to finite wavenumber k using three different widely used models, namely, with the Mermin type ELFs with generalized oscillator strengths (MELF‐GOS) model, the extended Drude model and the Penn model. The resulting ELFs show important differences but the MELF‐GOS model gives more realistic results when compared with the available experimental ELFs for finite k. These differences affect calculations of important parameters in projectile‐solid interaction. The calculated stopping power and energy‐loss straggling of Au and Al for H projectiles as well as the corresponding inelastic mean free path (IMFP) of electrons in Au and Al clearly show that the results depend on the model used for the ELF description. Comparison with experimental data gives support to the MELF‐GOS model, especially in a material with a complex energy‐loss spectrum such as Au. Copyright © 2008 John Wiley & Sons, Ltd.

Efficient discrete force control of cylinders may be realised by having multi-chambered cylinders, where the pressure of the chambers are shifted between fixed pressure levels of a secondary controlled system. However, the pressure shifting on a volume where the dynamics of pressure propagation is negligible have been be proven to have an unavoidable minimum loss due to the compressibility of the fluid. This paper investigates the effect of the pressure propagation in the connection and concludes that except more complex shifting schemes are introduced, the minimum loss remains unchanged. The paper analysis however also demonstrates and suggests, that with a clever valve control and shifting scheme, increased efficiency of a shift is obtainable by utilising the pipeline inductance.

Experiment and theory are combined to study the interaction of low energy electrons with microhydrated uracil and its halogenated analogues 5-fluorouracil and 5-bromouracil. We report electron ionization (EI) and electron attachment (EA) mass spectra for the uracils with different degrees of hydration. Both EI and EA lead to evaporation of water molecules. The number of evaporated molecules serves as a measure of the energy transferred to the solvent. Upon EI, the amount of energy transferred to neighboring water molecules is similar for all three studied species. On the other hand, the energy transferred upon EA rises significantly from uracil to 5-fluorouracil and 5-bromouracil. 5-Bromouracil is the only studied molecule that undergoes dissociative electron attachment after hydration at the studied energy of 1.2 eV. Theoretical modeling of the energetics for the electron attachment process allows for setting the energy transferred to the solvent on the absolute scale. We discuss the importance of this energy for the radiosensitization.

The smallest charging times required by fully discharged conventional batteries are some tens of minutes. This is an important limitation for mobile robot platforms. A previous paper already validated the possibility of integrating ultracapacitors and batteries in the same system. However, it has some significant limitations: 1) It works with an ultracapacitors module or a battery, but it does not work with both devices at the same time; 2) It requires an external dedicated charging station; 3) It is not possible to take profit from a part - which is non-negligible - of the energy previously stored in the ultracapacitors. This paper presents a new power supply system for mobile robot platforms that has been developed in order to overcome these limitations. Its main goals are evaluating the feasibility of: 1) Fully integrating batteries and ultracapacitors, working simultaneously as energy-storing devices, with the aim of enabling a mobile robot platform to achieve a reasonable autonomy after a very reduced charging time and considerable autonomy when there are no charging time constraints; 2) Installing all the system in the mobile robot platform, avoiding the use of an external dedicated charging station; 3) Extracting almost all the energy previously stored in the ultracapacitors. Both simulation results and experimental results are presented.

AbstractThe rotational spectra of two isotopologues of the 1:1 complex formed between acetone and ethanol have been recorded and analyzed by using Fourier‐transform microwave spectroscopy. One rotamer was detected, in which ethanol adopts the gauche form. The two subunits are linked by a conventional O−H⋅⋅⋅O and a weak C−H⋅⋅⋅O hydrogen bond, forming a six‐membered ring. Each rotational transition is split into five component lines due to the internal rotations of two nonequivalent acetone methyl groups. The V3 barriers to internal rotation of the two CH3 tops of acetone were determined to be 252(4) and 220(1) cm−1, which are noticeably lower than the value for the monomer (266 cm−1).

We have clearly evidenced the contribution of true surface states, in the range 1.8-2.5 eV, to the optical anisotropy of the GaAs(001)2×4 surface grown in situ by molecular beam epitaxy. These spectral features are well below the photon energy (2.9 eV) where bulklike anisotropies appear in coincidence with the E1 bulk critical point. The surface character is established by studying the evolution of the reflectance anisotropy spectroscopy spectra versus oxygen exposure. The interpretation is strengthened by comparison with high-resolution electron-energy-loss spectra measured on the same surface and by first-principles density-functional theory calculations.

We would like to thank the Spanish Direccion General de Investigacion Cientifica y Tecnica (projects PB95-0689 and PB96-1118) for financial support, the Instituto de Cooperacion Iberoamericana for a grant to CDD, and the Conselleria d'Educacio i Ciencia de la Generalitat Valenciana for a visiting professor fellowship to NRA under the program PROPIO.

Thin film technology has reached a maturity to achieve conversion efficiencies of the order of 22%. Among thin films, CdTe-based photovoltaic modules represent 80% of the total production. Nonetheless, some issues concerning back-contact are still open. In industrial process a chemical etching is required in order to make the CdTe film surface rich in Te. The Te-excess is fundamental in order to form a stable telluride compound with copper and to obtain an ohmic, low-resistance back-contact. Moreover, the Te-excess hinders the fast diffusion of copper in CdTe and its achievement of the junction region, preventing the destruction of the device. In this paper we study a ZnTe:Cu buffer layer deposited onto a CdTe film, characterized by a naturally Te-rich surface obtained with a particular chlorine heat treatment without any chemical etching. Copper diffusion and the CdTe/ZnTe:Cu interface were studied by x-ray photoemission spectroscopy (SIPS) and time-of-flight secondary ion mass spectrometry (ToF- SIMS) to deeply analyze the intermixing phenomena and copper behavior inside polycrystalline CdTe film.