Dec 2020 DOI 10.14302/issn.2639-3166.jar-20-3639
Masoero GiorgioCorresponding author
Accademia di Agricoltura di Torino, Via A. Doria 10, 10123 Torino (Italy).
An experiment on watercress (Lepidium sativum) 42 d days after sowing was set up to evaluate the effect of UVAB radiation on foliar pH and on NIR tomoscopy. The effect of 8 h of UV exposure (about 500 µWcm-2) was clear, causing a reduction in the foliar pH of 6.0%, compared to the contemporary control group (5.22 vs. 5.56). When the treated leaves were returned to white light, their pH rose by 1.7% (5.31), reaching the same level as leaves grown outdoors (5.33). On the basis of the NIR spectra, the leaves of the plants grown outdoors were recognized 100%, that is, more than the control leaves (87%) and the plants treated with UV on the day of measurement (81%). However, the effect of the UV marking on the leaves is not permanent as, after the UV treatment, the leaves returned to white light were classified at 61%, which is a greater value than the 37% of overlapping between the two groups. The foliar pH was highly correlated with the NIR spectra, with R2 0.43. These results corroborate the hypothesis of the influence of the solar cycle on the variation of the pH of leaves in plants, which we believe may have played a major role in past agricultural pandemics. These results call for the introduction of the pH test for the evaluation of resistance to pathogens. From the environmental point of view, the foliar pH could be enlisted as an in vivo long-time indicator of the response of plants to climate changes.
Mar 2020 DOI 10.14302/issn.2689-2855.jan-20-3243
Bendjemil BadisCorresponding author
DGM, FST, University of 8 Mai 1945 of Guelma, 24000 Guelma, Algeria
Cubic boron nitrid (cBN) bonded TiC and alloyed with single walled carbon nanotubes (SWCNTs or NC) ceramics matrix nanocomposites (CMNCs) tools were manufacturated by a field actived sparck plasma sintering processus (FASPS). The effects of cBN-TiC ratio, carbon nanotubes and optimisation of the sintering process on the microstructure, densification in addition mechanical and vibronic properties of NC-cBN-TiC nanocomposites were studied. The results showed that for the nanocomposite cBN-TiC vol. ratio of 8:2 with 0.1 wt% NC, it was found that microhardness incresses significantly with addition of carbon nanotubes exhibited the highest microhardness and fracture toughness. After sintering of the samples at 1800 °C, 10 mn, 75 MPa of cBN–TiC1-x, x=0.8 with and without addition of 0.1 wt% NC were characterized using field emission scanning electron microscopy (FESEM) and X-ray diffraction. The samples exhibited a dense polycrystalline structure. From the resonant Raman scattering we can locate the vibration frequency of the transformation cBN to hexagonal boron nitrid (hBN) and formation of secondary hard phase TiB2to consolid the (CMNCs) tools. The final product is hBN-TiC-TiB2-NC.The best product contained cBNx-TiC1-x (x=0.8)-0.1 wt % NC which was sintered at 1800 °C, 75 MPa for 10 mn. The Vickers hardness of cBN-TiC1-x (x=0.8) incresses with NC incorporation in the matrix The indentation fracture toughness was calculated to be 12.30 MPa m1/2 for cBNx-TiC1-x (x=0.8 -0.1 wt % NC ceramics matrix nanocomposite (CMNCs) tools with excellent wear resistant will be confirmed. The wear of cBN-TiC of the composites tools have shown that this is predominantly a chemical process involving the interaction of the tool with its environment and is restricted by the formation of protective layers on the exposed faces of the tool by the addition of carbon nanotubes (NC). The wear features of tools used in fine cutting tests under identical conditions will be compared and the results will be interpreted in terms of the existing models for the wear of cBN -based nanomaterials by the effects of the additives in the modified tools