Low‐Dose Irradiation Can be Used as a Phytosanitary Treatment for Fresh Table Grapes

Grapes (Vitis vinifera var. Sugraone and Vitis labrusca var. Crimson Seedless) were treated with 400, 600, and 800 Gy and the effects on physicochemical factors were measured alongside sensory testing during 3 wk of storage. Significant changes in texture and color with irradiation and age were measured but little visual difference was seen between control and irradiated grapes. However, age had a greater effect on firmness than irradiation for Sugraone grapes. Irradiation did not significantly (P ≤ 0.05) affect the SSC/TA ratio, which increased during storage. The trained panel detected significant changes in the berry texture and rachis color but rated sweetness and flavor significantly higher (P ≤ 0.05) for irradiated Sugraone as compared to the control. Consumers liked both the untreated and 800 Gy treated Sugraone grapes, but liked the untreated grapes more for texture (P ≤ 0.05). However, there was no difference in liking between irradiated (600 Gy or 800 Gy) and control samples of Crimson Seedless for any attribute. The results show that there are varietal differences in response to irradiation but the overall maintenance in quality of irradiated grapes during 3 wk of storage indicates that irradiation can serve as a viable phytosanitary treatment.     

Effects of electrode materials on performance measures of electrical discharge micro-machining

The main objective of this study is to investigate the effects of various electrode materials and their influences on electrical discharge micro-machining performance attributes. The performance attributes are determined in terms of tool wear rate (TWR), material removal rate (MRR), taper angle, overcut, and surface roughness by drilling micro-holes on SS 316?L material. It is noticed that, for high discharge energy the MRR, TWR, taper angle, and overcut are more and also when the thermal conductivity, boiling point, and melting point of the electrode material are high, the TWR is low. The surface finish is good at low discharge energy and low spindle speed. If the tool electrode is rotating at minimum speed during machining, a centrifugal effect is created on the dielectric so that debris at the inter-electrode gap is evacuated efficiently. If the tool is stationary, then the machining conditions are unstable due to improper flushing of debris.     

Microcracking of high zirconia refractories after t → m phase transition during cooling: An EBSD study

High zirconia refractories are composed of a zirconia skeleton surrounded by an intergranular glassy phase. In these materials, zirconia undergoes up to two successive phase transitions during the manufacturing process, c → t then t → m. This leads, after complete cooling, to the formation of microcracks.Preliminary observations have enabled to identify the mechanism mostly responsible for the observed microcracking. In particular, SEM imaging emphasizes the link between the positions of cracks and the presence of distinct crystallographic domains.Thus, our work focuses on the arrangement of the monoclinic and tetragonal domains in zirconia dendrites. The assessment by XRD of the thermal expansion coefficients of zirconia at the lattice scale and the analysis of EBSD maps show that cracking is produced by the thermal expansion mismatch between groups of crystallographic variants. The further reconstruction of both cubic and tetragonal - in the case of a presence of monoclinic zirconia at room temperature - parent grains enables to determine the impact of each transition on the final microstructure and the generated microcracking.     

Physicochemical driving forces behind exfoliation process of a synthetic montmorillonite in PDMS polymers

The conditions under which exfoliation of organo-montmorillonite in Poly(dimethylsiloxane) elastomers may occur were investigated via a three approaches: determination of the inter-platelet distance (as measured by WAXS), the surface energy evaluation (via inverse gas chromatography) of the polymer matrix and the clays, and measurement of heat of interaction (using a flow microcalorimeter in heptane) between polymers and the clay. The exfoliation efficiency is estimated by performing dynamic mechanical measurements. The results indicate that compatibilization and geometrical considerations are not sufficient requirements to transform clay particles into platelets. It evidences the determinant role of specific interactions between the reactive polymer end-groups and the filler surface. Polymer conformation on the clay surface and heat of adsorption associating “dispersive or London” forces and hydrogen bonding of respectively trimethyl- and hydroxyl-terminated polymer are evaluated.     

Biofilms: The Stronghold of Legionella pneumophila

Legionellosis is mostly caused by Legionella pneumophila and is defined as a severe respiratory illness with a case fatality rate ranging from 5% to 80%. L. pneumophila is ubiquitous in natural and anthropogenic water systems. L. pneumophila is transmitted by inhalation of contaminated aerosols produced by a variety of devices. While L. pneumophila replicates within environmental protozoa, colonization and persistence in its natural environment are also mediated by biofilm formation and colonization within multispecies microbial communities. There is now evidence that some legionellosis outbreaks are correlated with the presence of biofilms. Thus, preventing biofilm formation appears as one of the strategies to reduce water system contamination. However, we lack information about the chemical and biophysical conditions, as well as the molecular mechanisms that allow the production of biofilms by L. pneumophila. Here, we discuss the molecular basis of biofilm formation by L. pneumophila and the roles of other microbial species in L. pneumophila biofilm colonization. In addition, we discuss the protective roles of biofilms against current L. pneumophila sanitation strategies along with the initial data available on the regulation of L. pneumophila biofilm formation.     

Inclusion Complexes of Free Fatty Acids with Amylose

Spherocrystallite formation was observed when maize starch was gelatinized at temperatures greater than 120°C and the resultant paste stored at 75 – 95°C for defined time periods. Although the spherocrystals were of similar dimensions to native maize starch granules, and exhibited birefringent properties, Electron Microscope studies indicated quite different texture and morphology. Further evidence showed that the particles were formed from inclusion complexes of naturally occurring free fatty acids with the linear component of maize starch. Similar observations were made when the starch gelatinization was carried out at about 95°C in the presence of a specific α-amylase enzyme followed by similar storage conditions.