CdSe–Au nanorod networks welded by gold domains: a promising structure for nano-optoelectronic components

LiFePO_4?x F _x /C nanorods were prepared by room-temperature solid-state reaction and microwave heating. The structure and morphology of the as-prepared materials were analyzed by X-ray diffractometry and transmission electron microscopy. The results shows that the LiFePO_4?x F _x /C were well crystallized and consisted of nanoparticles with an average diameter of ten to several tens of nanometers, many round grains constituted solid rod-like structure. The length of the rods can be up to several hundreds of nanometers, and their diameters are around 100?nm. The results of electrochemical testing show that the initial discharge capacity of LiFePO_3.85F_0.15/C is 124.7?mAh?g^?1, with a negligible fading after 50 cycles at a constant current density of 1 C at room temperature. The capacity retention rate is 99.5?%, which is higher than that of LiFePO₄/C prepared by the same method. The doping of F helps improve electrical conductivity and Li⁺ diffusion of LiFePO₄/C. This study may provide new insights and understanding on the effect of F-doping on the electrochemical performance of LiFePO₄/C.     

The use of model probes for assessing in depth modifications induced during laser cleaning of modern paintings

The cleaning of over-paint layers is a usual requirement to be met in the conservation of modern paintings. In most cases, acrylics or other related compounds must be removed without affecting the original painting. The elucidation of the extent of any photochemical or structural modification induced to the substrate following laser irradiation is a crucial challenge for the broader implementation of such laser cleaning strategies into the conservation practice. To achieve this, a methodology based on the use of a sensitive photochemical and photomechanical model system is introduced. A probe consisting of a polymeric material (e.g., Paraloid B72) doped with aromatic photo-sensitizers (e.g., POPOP) of known photochemistry and coated with uniform acrylic layer effectively simulates the real case scenario. Following laser irradiation, a variety of spectroscopic techniques including single or multiphoton laser-induced fluorescence and third-harmonic generation are employed for the assessment of any photochemical and structural modification induced in the bulk material. Practical issues related to the laser parameters employed will be presented, and the potential for a more general applicability of this methodology in the laser cleaning of modern paintings will be discussed.     

Stereoselective synthesis of (3-aminodecahydro-1,4-methanonaphthalen-2-yl)methanols targeted to the C1 domain of protein kinase C

Protein kinase C (PKC) is a widely studied molecular target for the treatment of cancer and other diseases. We have approached the issue of modifying PKC function by targeting the C1 domain in the regulatory region of the enzyme. By using the X-ray crystal structure of the PKCδ C1b domain combined with molecular modeling, we discovered (3-aminodecahydro-1,4-methanonaphthalen-2-yl)methanol as a novel C1 domain ligand. The stereoselective synthesis of this tricyclic γ-amino alcohol was based on two successive Diels-Alder reactions to construct the six continuous stereocenters of the key intermediate.     

Structure of solvent-free grafted nanoparticles: molecular dynamics and density-functional theory

The structure of solvent-free oligomer-grafted nanoparticles has been investigated using molecular dynamics simulations and density-functional theory. At low temperatures and moderate to high oligomer lengths, the qualitative features of the core particle pair probability, structure factor, and the oligomer brush configuration obtained from the simulations can be explained by a density-functional theory that incorporates the configurational entropy of the space-filling oligomers. In particular, the structure factor at small wave numbers attains a value much smaller than the corresponding hard-sphere suspension, the first peak of the pair distribution function is enhanced due to entropic attractions among the particles, and the oligomer brush expands with decreasing particle volume fraction to fill the interstitial space. At higher temperatures, the simulations reveal effects that differ from the theory and are likely caused by steric repulsions of the expanded corona chains.     

Blind single-channel suppression of late reverberation based on perceptual reverberation modeling

A blind method for suppressing late reverberation from speech and audio signals is presented. The proposed technique operates both on the spectral and on the sub-band domains employing a single input channel. At first, a preliminary rough clean signal estimation is required and for this, any standard technique may be applied; however here the estimate is obtained through spectral subtraction. Then, an auditory masking model is employed in sub-bands to extract the reverberation masking index (RMI) which identifies signal regions with perceived alterations due to late reverberation. Utilizing a selective signal processing technique only these regions are suppressed through sub-band temporal envelope filtering based on analytical expressions. Objective and subjective measures indicate that the proposed method achieves significant late reverberation suppression for both speech and music signals over a wide range of reverberation time (RT) scenarios.