Processing of poly(1,3-bis-(p-carboxyphenoxy propane)-co-(sebacic anhydride)) 20:80 (P(CPP:SA)20:80) by matrix-assisted pulsed laser evaporation for drug delivery systems

We have demonstrated successful thin film growth of poly(1,3-bis-(p-carboxyphenoxy, propane)-co-(sebacic anhydride)) (20:80) by matrix-assisted pulsed laser evaporation using a KrF* excimer laser (λ = 248 nm, τ = 25 ns, ν = 10 Hz). The deposited thin films have been investigated by Fourier transform infrared spectroscopy, and atomic force microscopy. We have demonstrated that the main functional groups of poly(1,3-bis-(p-carboxyphenoxy, propane)-co-(sebacic anhydride)) (20:80) are present in the deposited film. The effect of matrix on both thin film structure and surface morphology was also examined. The goal of this work is to explore laser processing of this material to create suitable constructs for drug delivery applications.     

Study of polyethylene nanolayers by evanescent light microscopy

Nanometer polyethylene (PE) thin films were prepared by Matrix Assisted Pulsed Laser Evaporation (MAPLE). Insulating PE thin films of different thicknesses, below 200 nm, were fabricated by varying the deposition conditions. We then used the Differential Evanescent Light Intensity (DELI) microscopy technique for thickness profiles investigation of the PE nanolayers together with AFM measurements for calibration. A phenomenological model for the interaction between the evanescent waves and the deposited material and simulations of the nanofilms evanescent light scattering using the Maxwell equation solver FullWAVE are presented.     

The effect of laser wavelength on the ablation rate of carbon

The ablation of graphite is studied as a function of laser fluence for 355, 532 and 1,064 nm wavelength generated by a nanosecond Nd:YAG laser. It has been found that in the case of lower wavelengths, the transition from the thermal ablation to the phase explosion takes place at lower laser fluences. The change of crater shape due to the effect of deep drilling in the proximity of the phase explosion threshold was observed. The calculations of plasma radiation flux to the target surface were made, and the considerable increase of absorbed energy density was found in the case of 355 nm wavelength.     

Thin films of arylenevinylene oligomers prepared by MAPLE for applications in non-linear optics

This paper discusses two arylenevinylene oligomers with optical nonlinear properties. Their trans molecular structure was confirmed by Fourier Transform Infrared Spectroscopy and Nuclear Magnetic Resonance. Second Harmonic Generation and two-photon fluorescence have been observed on Matrix Assisted Pulsed Laser Evaporation-deposited thin films. We have seen two local maxima in UV-Vis spectra and a red shift of the photoluminescence peak for carbazole-based oligomer, which can be correlated with a higher conformational flexibility and with strong polarization interactions in the solid state. Scanning Electron Microscopy and Atomic Force Microscopy images have revealed a grainy morphology of the film deposited on titanium and a higher roughness for carbazole-based oligomer. Second harmonic measurements have shown nearly equal values of the second-order nonlinear optical coefficient for the triphenylamine and carbazole-based oligomers for P_laser < 100 mW. z-Scan and x-scan representations of the carbazole-based oligomer film have shown strong two-photon fluorescence intensity inside the sample confirming a volume process, and a strong second harmonic at the surface of the sample determined by the surface morphology.     

Spark Discharge Action on a Cathode Surface in Air Atmosphere

New results obtained by electron microscopy investigations of cathode spot parameters are qualitatively and quantitatively analysed to the view of further understanding of the cathode processes in spark discharges.     

Free-running ruby laser annealing of boron implanted silicon

An analytical treatment of the thermal phenomena during free-running ruby laser annealing of boron implanted silicon is presented. The heat equation was solved for a simplified shape of the pulse train consisting of a uniform succession of triangular spikes, identical in energy. During one spike the optical and thermal parameters of the sample were taken constant, but for each new spike, new values of these parameters were calculated taking into account their temperature dependence. Such a model predicts the melting of the top surface before the laser pulse has ended, for energy densities higher than 9×10⁴ J/m². RHEED confirms the presence of recristallization at about the same value of the laser-pulse energy densities.     

Unstable directions and fractal dimension for skew products with overlaps in fibers

A unique feature of smooth hyperbolic non-invertible maps is that of having different unstable directions corresponding to different prehistories of the same point. In this paper we construct a new class of examples of non-invertible hyperbolic skew products with thick fibers for which we prove that there exist uncountably many points in the locally maximal invariant set ?? (actually a Cantor set in each fiber), having different unstable directions corresponding to different prehistories; also we estimate the angle between such unstable directions. We discuss then the Hausdorff dimension of the fibers of ?? for these maps by employing the thickness of Cantor sets, the inverse pressure, and also by use of continuous bounds for the preimage counting function. We prove that in certain examples, there are uncountably many points in ?? with two preimages belonging to ??, as well as uncountably many points having only one preimage in ??. In the end we give examples which, also from the point of view of Hausdorff dimension, are far from being homeomorphisms on ??, as well as far from being constant-to-1 maps on ??.     

Fine-structure splitting calculation in the Ar III ion: comparison of perturbative (Breit-Pauli) and non-perturbative (MCDF-EAL) predictions

We have calculated fine structure splitting in the Ar III ion using the R-matrix method. Two independent atomic structure calculations have been performed. Results from the Breit-Pauli ?C and the Dirac-Atomic ?C R-matrix relativistic calculations are analysed comparatively. Cross sections and collision strengths are provided for selected weak and intercombination transitions, allowing explicitly for resonance effects. Convergence of the partial wave expansion is ensured by examining the partial collision strengths at collision energies up to 20 Ry. Radiative data are also reported here. We discuss all these results and compare them, when possible. For the allowed transitions, for which the resonance structure is not dominant, the two calculations are nearly identical.     

Biocompatible and bioactive nanostructured glass coatings synthesized by pulsed laser deposition: In vitro biological tests

We report on the synthesis by pulsed laser deposition with a KrF* excimer laser source (λ = 248 nm, τ = 25 ns) of bioglass thin films of 6P57 and 6P61 types. Physiology, viability, and proliferation of human osteoblast cells were determined by quantitative in vitro tests performed by flow cytometry on primary osteoblasts cultured on pulsed laser deposited bioglasses. Both types of glass films proved to be appropriate mediums for cell survival and proliferation. In a parallel investigation, cell morphology and adhesion to the surface was studied by fluorescence microscopy and scanning electron microscopy. Strong bonds between the materials and cells were found in both cases, as osteoblast pseudopodes penetrated deep into the material. According to our observations, the 6P57 glass films were superior with respect to viability and proliferation performances.     

AlN:Cr thin films synthesized by pulsed laser deposition: Studies by X-ray diffraction and spectroscopic ellipsometry

The structure and optical properties of AlN thin films doped with Cr atoms were studied by X-ray diffractometry, Fourier transform infrared spectroscopy and spectroscopic ellipsometry analyses. The films were synthesized by pulsed laser deposition from an AlN:Cr (10% Cr) target onto Si(1 0 0) wafers in vacuum at residual pressure of 10⁻³ Pa or in nitrogen at a dynamic pressure of 0.1 Pa. The study of the XRD patterns revealed that both phases co-existed in the synthesized films and that the amorphous one was prevalent. Two different amorphous matrices, i.e. two types of chemical bond arrangements, were found in films deposited at 0.1 Pa N₂. By difference, deposition in vacuum resulted in the coexistence of hexagonal and cubic crystallites embedded into an amorphous matrix. The introduction of Cr atoms into the AlN lattice causes a broadening of the IR spectrum along with the shift toward higher wavenumbers of the characteristic Al-N bands at 2351 cm⁻¹ and 665 cm⁻¹, respectively. This was related to the generation of a compressive stress inside films. In comparison to the optical constants of pure AlN films, the synthesized AlN:Cr films exhibited a smaller refractive index and showed a weak absorption throughout the 300-800 nm spectral region, characteristic to amorphous AlN structure.