3D MR imaging of dental cavities-an in vitro study

A 3D spin-echo (3D SE) pulse sequence was used on a 4.7 T research MRI system to produce images of extracted human first molar tooth placed in CuSO4 water solution. The maximal resolution achieved was 35 x 63 x 300 microm3 in read and two phase directions, respectively. The high-intensity signal from water in solution together with the lack of signal from mineralized tooth tissue produce very good contrast allowing to visualize topography of outer and inner surfaces of the tooth. The 3D MR data were median filtered, binarized and then divided into separate segments corresponding to the inner tooth cavities and the hard tooth tissue. The topography of the root canals was visualized and the canals volume was calculated. The presented technique may be used for quantitative analysis of the root canal cavities shape and volume. The results of such an analysis may be applied for estimation of the quality of the impressional mapping methods in restorative dentistry or as an alternative non-impressional 3D mapping method.     

Reflective and photoacoustic infrared spectroscopic techniques in assessment of binding media in paintings

This study proposes a method to estimate the lipid content in binding media in paintings that can be used at any laboratory equipped with an infrared spectrometer. The lipid content estimator, termed greasiness index (GI), is defined as a ratio of lipid ν(C=O) and protein amide I bands at 1743 and 1635 cm⁻¹, respectively. Three Fourier transform infrared (FTIR) sampling techniques were evaluated for GI determination: reflective attenuated total reflection—ATR, specular reflection microscopy—μSR and photoacoustic—PAS. A set of model painting samples containing three tempera binding media (casein, egg, egg + oil), seven pigments and one varnish type were used in the study. Multivariate analysis was used to evaluate the resulting data. A good reproducibility of GI was obtained by ATR and PAS but not with μSR. The discriminative power of the technique is higher for unvarnished samples, but, generally, the GI estimator can be used for the categorisation of binding media in large populations of painting samples analysed with the same FTIR technique (sampling technique, detection, etc.).     

Two-dimensional imaging of two types of radicals by the CW-EPR method

New EPR resonators were developed by using a ceramic material with a high dielectric constant, epsilon=160. The resonators have a high quality factor, Q=10(3), and enhance the sensitivity of an EPR spectrometer up to 170 times. Some advantages of the new ceramic resonators are: (1) cheaper synthesis and simplified fabricating technology; (2) wider temperature range; and (3) ease of use. The ceramic material is produced with a titanate of complex oxides of rare-earth and alkaline metals, and has a perovskite type structure. The resonators were tested with X-band EPR spectrometers with cylindrical (TE(011)) and rectangular (TE(102)) cavities at 300 and 77K. We discovered that EPR signal strength enhancement depends on the dielectric constant of the material, resonator geometry and the size of the sample. Also, an unusual resonant mode was found in the dielectric resonator-metallic cavity structure. In this mode, the directions of microwave magnetic fields of the coupled resonators are opposite and the resonant frequency of the structure is higher than the frequency of empty metallic cavity.     

Towards the map of quantum gravity

In this paper we point out some possible links between different approaches to quantum gravity and theories of the Planck scale physics. In particular, connections between loop quantum gravity, causal dynamical triangulations, Ho?ava–Lifshitz gravity, asymptotic safety scenario, Quantum Graphity, deformations of relativistic symmetries and nonlinear phase space models are discussed. The main focus is on quantum deformations of the Hypersurface Deformations Algebra and Poincaré algebra, nonlinear structure of phase space, the running dimension of spacetime and nontrivial phase diagram of quantum gravity. We present an attempt to arrange the observed relations in the form of a graph, highlighting different aspects of quantum gravity. The analysis is performed in the spirit of a mind map, which represents the architectural approach to the studied theory, being a natural way to describe the properties of a complex system. We hope that the constructed graphs (maps) will turn out to be helpful in uncovering the global picture of quantum gravity as a particular complex system and serve as a useful guide for the researchers.     

Carpet oscillator: A new megastable nonlinear oscillator with infinite islands of self-excited and hidden attractors

Polarisation of the particle spin can be an important problem for different plasmas. In this article, the contribution of the electron spin on the growth rate of the temperature anisotropy of electromagnetic instabilities has been investigated. Results show that polarisation of the electron spin will restrict the instability growth rate while instability can survive due to the spin-depolarised electrons even when the requested temperature anisotropy is vanished. Instability can reach the damping state exponentially due to the spin-polarised electrons while it can grow linearly due to the spin-depolarised (the semi-classical) electrons.     

Spectroscopic,structural and theoretical studies of 2‐methyl‐4‐nitroaniline (MNA) crystal. Electronic transitions in IR

Polarized FT‐IR, Raman, neutron scattering (IINS), and UV‐Vis‐NIR spectra of 2‐methyl‐4‐nitroaniline (MNA) crystal plates, powder, and solutions were measured in the 10–50 000 cm⁻¹ range. The FT‐IR spectrum of deuterated MNA (DMNA) in KBr pellet, the Raman spectrum of the DMNA powder as well as the EPR spectrum of the MNA powder were also recorded. Complete assignments of bands to normal vibrations have been proposed. Density functional theory (DFT) calculations of wavenumbers and potential energy distribution (PED) have been performed to strengthen the assignments. The analysis of vibrational and electronic spectra has revealed vibronic couplings in MNA molecules in solutions and in crystals. In the polarized FT‐IR spectra of the crystal five unusually large bands are observed in MIR and NIR regions. Their origin is discussed in terms of N H···O, C H···O, C H···H N hydrogen bonds, intermolecular charge transfers, electrostatic interactions, and ion radicals formation in the crystal. The role of a methyl group introduction to 4‐nitroaniline is analyzed. The crystal structure of MNA at the room temperature was re‐investigated. Copyright © 2008 John Wiley & Sons, Ltd.     

Ultrasonic system for accurate distance measurement in the air

This paper presents a system that accurately measures the distance travelled by ultrasound waves through the air. The simple design of the system and its obtained accuracy provide a tool for non-contact distance measurements required in the laser’s optical system that investigates the surface of the eyeball.