Friction stir welding of API X70 steel incorporating Ti-dioxide

In the present work, the microstructural evolution and hardness of HSLA X70 joined by friction stir welding were investigated. The FSW was applied to HSLA X70 with and without the addition of titanium dioxide (TiO₂) powders. To evaluate the microstructural features and hardness of different weld zones, optical microscopy and Vickers microhardness measurements were applied. The results show that the distribution of TiO₂ powders is strongly dependent on the applied friction stir processing, which in turn changed significantly the microstructure and hardness profile. In this regard, the optimum stirring action resulted in a homogeneous and fine dispersion of particles leading to the domination of an acicular ferrite phase with a hardness of 370 HV. On the other hand, the lower stirring action resulted in coarse particles as well as the development of the polygonal ferrite structure with a hardness of ～185 HV.     

Modeling Transient Heat Conduction and Radiative Transport in Semitransparent Media: A Tool for the Interpretation of Reflectivity Data

In this work the problem of interpretation of reflectivity data for semitransparent materials at high temperatures is addressed. A detailed analysis of the transient thermal response of a participating medium subjected to a pulse of finite energy is performed using a new method developed to solve the general equation of energy transfer for a conductive, absorbing, emitting, and scattering medium. The model, previously presented for a material with constant optical properties (Musella, Tschudi, Int J Thermophys 26:981, 2005), has been upgraded to encompass a much wider scenario where the thermophysical and optical properties are temperature dependent. This allows the study of the transient reflectivity of laser-heated samples where high heating rates and strong temperature gradients occur near the surface. Considerable differences of the reflectivity values for the same surface temperature calculated in the heating and cooling phases, both different from the corresponding values for an isothermal sample, are reported in accordance with experimental results.     

Thickness dependence of the electrical resistivity of epitaxially grown silver films

Silver films were deposited onto (111)-oriented single-crystal silicon substrates under different deposition conditions. The thickness dependence of their electrical resistivity was analysed in terms of the Fuchs-Sondheimer theory. The scattering parameter p was found to vary from +0.8 to -0.8. The results are correlated with film structure. The negative p values are traced back to the predominant contribution of grain boundary scattering in the case of polycrystalline films.     

Short communication: Repeatability of intravenous glucose tolerance test traits in young Holstein-Friesian cattle

Few studies have compared individual variability of an intravenous glucose tolerance test (ivGTT) obtained daily in young cattle. The objective of this study was to evaluate the repeatability of glucose traits and insulin responses derived from ivGTT during 3 consecutive days in Holstein-Friesian cattle (bulls: n = 4, steers: n = 3, heifers: n = 3). Blood collections were performed from min 0 (basal concentrations) to min 63 (last measurement). Additional estimates included maximal concentration for glucose and insulin, glucose half-life time (GHLT), and glucose and insulin area under the curve. Glucose traits showed higher repeatability when compared with insulin responses. On average, the glucose trait and insulin response with the lowest coefficient of variation was GHLT (0.7%) and insulin area under the curve (21.3%), respectively. In addition, a general linear model with repeated measures was used to test for significant differences in glucose and insulin concentrations over time at different trial days. Both glucose and insulin concentrations were influenced by time point but not by trial day or time point × trial day. The results from this study showed that individual insulin responses were more variable than glucose traits. The high repeatability of GHLT evidenced the strict regulatory glucose disposal mechanisms occurring in young Holstein-Friesian cattle, whereas insulin responses showed high variability despite controlled management and nutritional practices.     

Prussian blue analogues of reduced dimensionality

Mixed-valence polycyanides (Prussian Blue analogues) possess a rich palette of properties spanning from room-temperature ferromagnetism to zero thermal expansion, which can be tuned by chemical modifications or the application of external stimuli (temperature, pressure, light irradiation). While molecule-based materials can combine physical and chemical properties associated with molecular-scale building blocks, their successful integration into real devices depends primarily on higher-order properties such as crystal size, shape, morphology, and organization. Herein a study of a new reduced-dimensionality system based on Prussian Blue analogues (PBAs) is presented. The system is built up by means of a modified Langmuir-Blodgett technique, where the PBA is synthesized from precursors in a self-limited reaction on a clay mineral surface. The focus of this work is understanding the magnetic properties of the PBAs in different periodic, low-dimensional arrangements, and the influence of the "on surface" synthesis on the final properties and dimensionality of the system.