The simulation of a wave propagation in a bcc iron crystal with a crack

We present a large-scale molecular dynamic simulations of a wave propagation in a bcc iron based on a N-body potential model which gives a good description of an anisotropic elasticity. A crack is embedded in a bcc iron crystal having a basic cubic orientation. We consider a central pre-existing Griffith (through) crack. The crystal is loaded on its front face and the response is detected on its opposite face. The acquired results are very important for the new NDT nano scale methods

Combining nanolime and calcium carbonate polymorphs in the consolidation of porous stone: a small angle neutron scattering and synchrotron X-ray computed microtomography study

Sound Maastricht limestone, a calcarenite stone with high porosity, mostly employed as construction material in Belgium and Netherlands, was chosen for consolidation treatments with novel agents containing nanolime suspension and polymorphs of calcium carbonate (CaCO3) particles. The alteration of microstructure after consolidation treatment was investigated, for the first time, using the combination of small angle neutron scattering (SANS) and synchrotron X-ray computed microtomography (μ-CT). Good compatibility between nanolime, CaCO3 particles and limestone matrix was observed under the scanning electron microscope. SANS measurement exhibited two scattering regimes, corresponding to pores with smooth surface and rough fractal surface. After the consolidation treatment, mainly pores in region ranging from 30 to 300 nm were reduced and complexity of the pore surface was increased. μ-CT results revealed a high number of pores up to 400 μm highly connected, and many fossils with mostly closed pores (see Fig. 1). The decrease in total porosity after the consolidation treatment was around 3 % - quite a high decrease considering that the amount of consolidating material that was applied was very low; the external volume of the samples (usually the one with an accumulation of consolidating agent) was excluded from the calculation of porosity, and the μ-CT technique detected both open (as in case of mercury intrusion porosimetry) and closed porosity, that cannot be affected with consolidation treatment. The tested system, represents a new possibility of consolidation treatment that preserves the chemical compatibility of the agent with the limestone and performs better than the same treatments with nanolime alone. The advantage of the usage of SANS and μ-CT is their non-invasive approach and possibility of detecting nano-/microstructural changes in very small specimens, which are usually needed when real samples from cultural heritage objects are tested

Nuclear orientation of152,154Tb in gadolinium

The anisotropy in the directional distribution of gamma-rays from the decay of152,154Tb oriented in a gadolinium matrix at low temperatures, has been measured at the angles of 0 and π/2 with respect to the applied magnetic field direction at temperature of (15±1) mK. Unambiguous values of spin have been deduced for several levels in152Gd. Multipole mixing ratios of many gamma-ray transitions occurring in152Gd have been found and results are compared with the similar transitions in150,154,156Gd and they are discussed in terms of the rotational-vibrational model and dynamic deformation theory based on the Strutinsky method. Our results confirm the spin value of 0 for 21·4 h isomer in154Tb and they establish the spin value of 3 for the 2277·0 and 2336·1 keV levels and the spin value of 4 for the 2416·3 keV level in154Gd. © 1981 Academia, Publishing House of the Czechoslovak Academy of Sciences