Determination of optical properties of a corn starch biofilm

In this work, the optical properties of a corn starch-based film were correlated with its structural properties. Scanning electron microscopy was performed to determine if incorporation of starch into the matrix gives a homogenous and smooth surface. X-ray diffraction was performed to identify the relative degree of crystallinity. The optical properties of the film in the range 300 to 2500 nm were studied, showing diffuse total transmissivity and total absorption coefficients comparable with that of low-density polyethylene films. The process used in this research is carried out in an aqueous solvent, without using any toxic raw material, and prepared by casting. The process allows for the use of different additives. This processing of the starch film represents a great advantage also because it takes a maximum of 10 h, four times less than other processes, and no special equipment is needed. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47111.     

Sintered electrospun poly(ɛ-caprolactone)–poly(ethylene terephthalate) for drug delivery

Electrospinning has the inherent advantage of being able to achieve molecular mixing of polymers having substantially different melting points. Electrospun poly(ɛ-caprolactone)–poly(ethylene terephthalate) (PCL:PET) capsules are densified by sintering to enable drug encapsulation. Proton and diffusive nuclear magnetic resonance, as well as a selective dissolution, suggest an absence of reaction between the two polymers. Sintering at 100 °C successfully densifies 88.89:11.11 and 75:25 PCL:PET blends. Following sintering, the otherwise dense 75:25 composition retains electrospun features and exhibits some “memory” of its previous state. Sintering increases UTS approximately eightfold versus as-spun values for 88.89:11.11 and 75:25. Elongation increases sixfold and twofold and modulus 44- and 69-fold for the 75:25 and 88.89:11.11 samples, respectively. Differential scanning calorimetry suggests a postsintering structure of nanoscale PET dispersed in PCL along the original fiber directions. Selective PCL removal from dense blends shows that fibrous characteristics remain. An internal shish–kebab-like structure is also present in as-spun 75:25 PCL:PET. Water absorption of hydrophobic oil-containing capsules is approximately zero after 49 days. In contrast, hydrophilic (HPI) oils allow substantial water uptake. Unsurprisingly, there is no release of a model drug from the hydrophobic carrier. HPI oil provides linear (zero-order) release inversely proportional to PET from the 88.89:11.11 and 75:25 ratios. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47731.     

On the effective conductivity and the apparent viscosity of a thin rough polymer interface using PGD-based separated representations

Composite manufacturing processes usually proceed from preimpregnated preforms that are consolidated by simultaneously applying heat and pressure, so as to ensure a perfect contact compulsory for making molecular diffusion possible. However, in practice, the contact is rarely perfect. This results in a rough interface where air could remain entrapped, thus affecting the effective thermal conductivity. Moreover, the interfacial melted polymer is squeezed flowing in the rough gap created by the fibers located on the prepreg surfaces. Because of the typical dimensions of a composite prepreg, with thickness orders of magnitude smaller than its other in-plane dimensions, and its surface roughness having a characteristic size orders of magnitude smaller than the prepreg thickness, high-fidelity numerical simulations for elucidating the impact of surface and interface roughness remain today, despite the impressive advances in computational availabilities, unattainable. This work aims at elucidating roughness impact on heat conduction and the effective viscosity of the interfacial polymer squeeze flow by using an advanced numerical strategy able to reach resolutions never attained until now, a sort of numerical microscope able to attain the scale of the smallest geometrical detail.     

Residual stress effect on the fracture toughness of lithium disilicate glass-ceramics

In glass-ceramics (GCs), on cooling from the crystallization temperature, internal residual stresses are generated due to the difference between the thermal expansion coefficient (TEC) of the crystal phase(s) and the residual glass. These stresses could degrade or promote their mechanical properties. In this work, we varied the magnitude of the residual stresses in lithium silicate GCs by designing their microstructures. The level of internal stresses was measured using (Synchrotron) X-ray diffraction. The effects of anisotropy of thermal expansion, crystal shape, and intensity of the residual stresses were analyzed and compared using theoretical models. We extended the Hsueh-Becher model to include the thermal expansion anisotropy of the orthorhombic lithium disilicate (LS2) crystals. We found that the average residual stresses within the LS2 crystals are compressive or null (−100 to ~0) and highly anisotropic. Most importantly, within the limits of this study, we found no evidence for the influence of (compressive or null) residual stresses on the fracture toughness of the studied GCs. Within the crystal size range from 1 to 5 μm, a highly crystallized volume fraction coupled to relatively large crystals (5 μm) of high elastic modulus improved the glass-ceramic fracture toughness. This result can guide the microstructural design of novel tough GCs.     

Modelling and solving spare parts supply chain network design problems

Spare parts are key operational assets in order to minimise unexpected equipment downtimes that may significantly impact a company’s results. The spare parts supply chain network supports the entire spare parts operations management and it is essential to achieve the planned goals. However, most of the traditional literature on spare parts management has not focused on the underlying supply chain network. Thus, this paper studies the integration of supply chain network design and control with traditional spare parts management. In particular, a generic network optimisation modelling structure is proposed, with simultaneous optimisation of warehouse locations and inventory control decisions, allowing minimising the total costs associated with the spare parts supply chain network. The generic model is specified based on three inventory control policies widely employed in the industry, which are suitable for managing a great variety of spare parts, i.e. (s, Q), (R, s, S) and (S-1, S). Furthermore, a solution approach is proposed based on Generalised Benders Decomposition. Finally, numerical results from a real-world application case in the process industry are shown and discussed.     

Effect of simulated acidic and salty fermentation conditions on kinetic growth parameters and probiotic potential of Lactobacillus acidipiscis and Lactobacillus pentosus

The technological stress during food processing may alter the beneficial interactions of food-associated Lactobacillus on the host. The effect of initial combined acidic (pH 5.0) and osmotic stress (NaCl 5 %, w/v with or without CaCl₂ 0.02 %, w/v) typically present in vegetable fermentations and cheesemaking were investigated. The growth kinetics prediction, hydrophobicity, auto-aggregation, in vitro survival and adhesion were determined in Lactobacillus acidipiscis and Lactobacillus pentosus isolated from a Mexican salty cheese. The growth was modelled with the modified Gompertz equation (R > 0.99; RMSE < 0.01). The lag phase increased (>10 h), and auto-aggregation was reduced. Hydrophobicity and S-layer total proteins varied. Gut survival reduced >4 log 10 units compared to the initial intake. Nevertheless, adhesion remained the same. Hence, combined stress affected the technological and physiological properties of both strains negatively. Further research is needed to identify the effect of the combined stress on the potential bioactivity of the strains.     

Effect of EDTA,sodium, and calcium hypochlorite on the inorganic component of root canal dentin: A SEM analysis

This study evaluated the influence of canal irrigation protocols with 5.25% calcium hypochlorite [Ca(OCl)₂], 5.25% sodium hypochlorite (NaOCl) and 17% EDTA solution on the inorganic component of root canal dentin. Sixty roots were randomly divided into six groups (n = 10): Saline solution (SS) (control); Saline solution (SSE) +17% EDTA; CH ? 5.25% Ca(OCl)₂; CHE ? 5.25% Ca(OCl)₂ + 17% EDTA; SH ? 5.25% NaOCl; SHE ? 5.25% NaOCl +17% EDTA. After canal irrigation, the specimens were longitudinally split and analyzed by scanning electron microscopy (SEM). Dentinal tubules were observed in transverse (middle and apical thirds) direction. The images were classified in scores, according to smear layer removal and peritubular dentin alteration, and data were analyzed by Kruskal–Wallis's test, followed by Dunn's test (α = 0.05). In the middle third, all groups with EDTA presented better removal of the smear layer with higher peritubular dentin alteration (p < .05). In the apical third, this happened only in SHE (p < .05). Ca(OCl)₂ and NaOCl exhibit similar performance to remove smear layer and alteration of the inorganic component in the middle third. In the apical third, NaOCl associated with EDTA showed better performance in smear layer removal.