Detection and Visualization of Minor Irradiation-Induced Changes in Polytetrafluoroethylene (PTFE) by Raman Spectroscopy.

Exposure of polytetrafluoroethylene (PTFE) to argon plasma results in chemical modification of the polymer near the surface. Interestingly, PTFE modification can be induced by the sub-band gap ultraviolet (UV) irradiation. In the latter case, the changes in the chemical structure are very subtle, and they are practically invisible to conventional experimental techniques.

Crystal Analyzer Based Multispectral Microtomography Using CCD-Sensor.

To solve the problems of spectral tomography, an X-ray optical scheme was proposed, using a crystal analyzer in Laue geometry between the sample and the detector, which allowed for the selection of predetermined pairs of wavelengths from the incident polychromatic radiation to obtain projection images. On a laboratory X-ray microtomography setup, an experiment was carried out for the first time where a mixture of micro-granules of sodium chloride NaCl, silver behenate AgCHO, and lithium niobate LiNbO was used as a test sample to identify their spatial arrangement. The elements were chosen based on the presence of absorption edges in two of the elements in the energy range of the polychromatic spectrum of the probing radiation.

Baseline Search in Raman Spectroscopy by Modified Tikhonov Regularization with Automatic Choice of Both Parameters.

Baseline estimation in vibrational spectroscopy can be done efficiently with Tikhonov regularization. The state-of-the-art approaches, based on asymmetric weighting, require an additional parameter. Besides λ, the penalty for the second derivative, they introduce the asymmetry parameter that sets different weights for the points above and below the baseline.

Pressure dependent half-metallic ferromagnetism in inverse Heusler alloy FeCoAl: a DFT+U calculations.

We report the electronic and magnetic properties along with the Curie temperature ( ) of the inverse full Heusler alloy (HA) FeCoAl obtained by using the first-principles computational method. Our calculations suggests that FeCoAl is a magnetic metal when treated within PBE-GGA under the applied compressive pressures. However, the implementation of electron-electron (U) (, GGA+U) with varying compressive pressure () drastically changes the profile of the electronic structure.

Enhanced Tomographic Sensing Multimodality with a Crystal Analyzer.

This article demonstrates how a combination of well-known tools-a standard 2D detector (CCD (charge-coupled device) camera) and a crystal analyzer-can improve the multimodality of X-ray imaging and tomographic sensing. The use of a crystal analyzer allowed two characteristic lines of the molybdenum anode-Kα and Kβ-to be separated from the polychromatic radiation of the conventional X-ray tube. Thus, as a result of one measurement, three radiographic projections (images) were simultaneously recorded.

Dual-energy crystal-analyzer scheme for spectral tomography.

In the present work, a method for adjusting a crystal analyzer to separate two characteristic lines from the spectrum of a conventional X-ray tube for simultaneous registration of tomographic projections is proposed. The experimental implementation of this method using radiation of a molybdenum anode (α, β lines) and a silicon Si(111) crystal analyzer in Laue geometry is presented. Projection images at different wavelengths are separated in space and can be recorded independently for further processing.

Phonon propagation scale and nanoscale order in vitreous silica from Raman spectroscopy.

For nanoscale systems such as nanoparticles and 3D-bonded networks, the range of spatial coherence is well reflected in the Raman spectral pattern. For confined, or localized, phonons, the range of q-points contributing to the spectrum depends on the phonon confinement length, which makes it possible to derive size information from the spectra. In this work, the Raman spectrum of vitreous silica is described as localized phonons of an SiO network.

Application of Magnetic Force Microscopy for Investigation of Epitaxial Ferro- and Antiferromagnetic Structures.

Growing of epitaxial FeMn/Fe/Mo/R-sapphire films was performed with a new configuration of two in-plane easy axes of Fe(001)-layer magnetization in which application of annealing in a magnetic field forms an unidirectional anisotropy. The microstructures made from these films exhibited an exchange bias 25-35 G along an exchange field generated at antiferromagnet/ferromagnet (AFM/FM) interface. Magnetic force microscopy (MFM) experiments supported by micromagnetic calculations and magneto-resistive measurements allowed interpretation of the magnetic states of the Fe layer in these microstructures.

Macroscopic self-reorientation of interacting two-dimensional crystals.

Microelectromechanical systems, which can be moved or rotated with nanometre precision, already find applications in such fields as radio-frequency electronics, micro-attenuators, sensors and many others. Especially interesting are those which allow fine control over the motion on the atomic scale because of self-alignment mechanisms and forces acting on the atomic level. Such machines can produce well-controlled movements as a reaction to small changes of the external parameters.

Monochromatic computed microtomography using laboratory and synchrotron sources and X-ray fluorescence analysis for comprehensive analysis of structural changes in bones.

A combination of X-ray tomography at different wavelengths and X-ray fluorescence analysis was applied in the study of two types of bone tissue changes: prolonged presence in microgravity conditions and age-related bone growth. The proximal tail vertebrae of geckos were selected for investigation because they do not bear the supporting load in locomotion, which allows them to be considered as an independent indicator of gravitational influence. For the vertebrae of geckos no significant differences were revealed in the elemental composition of the flight samples and the synchronous control samples.

Experimental study of thermal stability of thin nanowires.

Thin (D < 10 nm) nanowires are in principle promising for their application as catalysts and as elements of nanocomputers and quantum devices. To perform these tasks, their structure and properties must be stable at least at standard conditions. Using our technique based on the capture of small particles to the core of quantized vortices in superfluid helium, we synthesized nanowires made of various metals and alloys and investigated their thermal stability.

Structure and Properties of Platinum, Gold and Mercury Nanowires Grown in Superfluid Helium.

Webs consisting of nanowires made of gold, platinum and mercury were produced by the technique based on laser ablation of metals inside superfluid helium. Their morphology and structure as well as their electrical conductivity have been studied. Diameters of gold and platinum nanowires are 4.

The use of surface charging in the SEM for lithium niobate domain structure investigation.

The different lithium niobate crystals with opposite domain structure (ODLN) were studied in the SEM using e-beam negative surface charging. In the ODLN the polarization vector Ps alternates periodically "tail-to-tail" and "head-to-head" and arranges perpendicular to the domain boundaries. In the investigation we have used congruent LiNbO(3) crystals (CLN) and Cr(2)O(3)- and In(2)O(3)-doped LN with the ODLN structure.