Chemical synthesis and sintering behaviour of highly dispersed W/Cu composite powders

The paper reports the preparation of W/Cu composite powders by a wet process based on the reduction of selected copper precursors in ethylene glycol and in the presence of tungsten powders. Reactions were performed in different conditions of temperature, time and concentration of the copper precursor. Two different Cu compounds, Cu(AcO)₂·H₂O and CuO (coarse or fine) and two W powders (coarse or fine) were used. The reaction yields ranged from 75% to 98%. Dense bodies (up to 97% fractional density) with highly homogeneous microstructure as well as high electrical conductivity (up to 41% IACS) were obtained by sintering W/Cu powders at 1350 °C.     

Adiponectin and Leptin Exert Antagonizing Effects on HUVEC Tube Formation and Migration Modulating the Expression of CXCL1, VEGF,MMP-2 and MMP-9

Adiponectin and leptin are two abundant adipokines with different properties but both described such as potent factors regulating angiogenesis. AdipoRon is a small-molecule that, binding to AdipoRs receptors, acts as an adiponectin agonist. Here, we investigated the effects of AdipoRon and leptin on viability, migration and tube formation on a human in vitro model, the human umbilical vein endothelial cells (HUVEC) focusing on the expression of the main endothelial angiogenic factors: hypoxia-inducible factor 1-alpha (HIF-1α), C-X-C motif chemokine ligand 1 (CXCL1), vascular endothelial growth factor A (VEGF-A), matrix metallopeptidase 2 (MMP-2) and matrix metallopeptidase 9 (MMP-9). Treatments with VEGF-A were used as positive control. Our data revealed that, at 24 h treatment, proliferation of HUVEC endothelial cells was not influenced by AdipoRon or leptin administration; after 48 h longer exposure time, the viability was negatively influenced by AdipoRon while leptin treatment and the combination of AdipoRon+leptin produced no effects. In addition, AdipoRon induced a significant increase in complete tubular structures together with induction of cell migration while, on the contrary, leptin did not induce tube formation and inhibited cell migration; interestingly, the co-treatment with both AdipoRon and leptin determined a significant decrease of the tubular structures and cell migration indicating that leptin antagonizes AdipoRon effects. Finally, we found that the effects induced by AdipoRon administration are accompanied by an increase in the expression of CXCL1, VEGF-A, MMP-2 and MMP-9. In conclusion, our data sustain the active role of adiponectin and leptin in linking adipose tissue with the vascular endothelium encouraging the further deepening of the role of adipokines in new vessel’s formation, to candidate them as therapeutic targets.     

Liquid limit of low- to medium-plasticity soils: comparison between Casagrande cup and cone penetrometer test

For liquid limit determination, the European Standards require the cone penetrometer technique or, alternatively, the Casagrande cup method; but the latter is widely used in practice. As most European soil classification systems are not adapted to the new European Standards, a systematic study was carried out to verify the differences between the two techniques for liquid limit determination, examining clayey soils from various geologic units. Comparison of 100 liquid limit values ranging between 20 and 50% indicates that the liquid limit obtained by the fall cone method is generally 2.2% points higher than that obtained by the hard base Casagrande apparatus. Comparison of data from different sources consistently indicates that the equation proposed in this study may be useful in revising existing soil classification systems, avoiding problems of soil classification due to the technique used for liquid limit determination.     

Sound influence on landscape values

In order to study the influence of the interaction between visual and acoustic stimuli on perception of the environment, 36 sound and image combinations were presented to 75 subjects. The sounds and images used were of natural and semi-natural settings and urban green space. Affective response was measured in terms of pleasure. The results show a rank of preferences running from natural to man-made sounds, with the nuance of a potential alert or alarm-raising component of the sound. The potential for alert or alarm-raising may be related, over and above the information content or meaning, to the characteristics of the sound frequency spectrum, specifically to the existence of frequency bands whose sound levels impose themselves on the acoustic background. The congruence or coherence between sound and image influences preferences. Coherent combinations are rated higher than the mean of the component stimuli. Results suggest that there is a need to identify places or settings where the conservation of the sound environment is essential, because of its salient informational content or due to the drastic impact of the loss of sound quality on observer appreciation, for example, in urban green spaces, natural spaces and cultural landscapes.     

Sol–gel derived 45S5 bioglass: synthesis, microstructural evolution and thermal behaviour

In this work, the 45S5 bioactive glass was synthesized through an aqueous sol-gel method. Characteristic functional groups were evidenced by Fourier transform infrared spectroscopy, the thermal behaviour was investigated by thermogravimetric and differential thermal analysis, crystallization kinetics and phase evolution were followed by X-ray diffraction measurements. The sintering behaviour of the sol-gel derived 45S5 was then studied by dilatometry and the microstructural evolution was followed step-by-step, interrupting the thermal cycle at different temperatures. In vitro dissolution tests were performed in order to assess the degradation behaviour of sol-gel derived 45S5 samples thermally treated at different temperatures. A relevant influence of the calcination conditions (namely, dwelling time and temperature) of the as-prepared powder on the phase appearance and its sintering behaviour as well as on the porosity features, in terms of pore dimension and interconnectivity, of the fired materials was stated.     

Color space transformations for digital photography exploiting information about the illuminant estimation process

The color reproduction accuracy is a key factor to the overall perceived image quality in digital photography. In this framework, both the illuminant estimation process and the color correction matrix concur in the formation of the overall perceived image quality. To the best of our knowledge, the two processes have always been studied separately, thus ignoring the interactions between them. We investigate here these interactions, showing how the color correction transform amplifies the illuminant estimation errors. We demonstrate that incorporating knowledge about the illuminant estimation behavior in the optimization of the color correction matrix makes it possible to alleviate the error amplification. Different strategies to improve color accuracy under both perfect and imperfect white point estimations are investigated, and the experimental results obtained with a digital camera simulator are reported.     

模拟嵌入式FRP条增强钢筋混凝土梁抗剪的三维力学模型

嵌入式FRP增强钢筋混凝土梁抗剪是进行结构修复的新技术,由于嵌入式FRP所具有的一些优势,使其成为较好的外贴加固技术,越来越受到重视。嵌入式FRP主要优势在于材料开发、对结构完整性的保护以及相对较快的适用性。由于FRP条复杂的几何尺寸,粘结后的非线性力学性能,混凝土受拉性能的离散性,使得嵌入式FRP条加固的性能十分复杂,一般通过试验来获得其性能。为更好地掌握表面嵌贴FRP带的性能,提出三维力学模型,用于模拟在相似加载过程中,嵌入式FRP条体系对钢筋混凝土梁抗剪强度的贡献。模型很好地解释了试验结果,并在模型中考虑了粘结滑移力和混凝土破坏之间的相互作用以及相邻FRP条之间的相互作用等复杂现象。