Mechanical, Thermal, and Physicochemical Properties of Filaments of Poly (Lactic Acid), Polyhydroxyalkanoates and Their Blend for Additive Manufacturing.

Polymeric blends are employed in the production of filaments for additive manufacturing to balance mechanical and processability properties. The mechanical and thermal properties of polymeric filaments made of poly (lactic acid) (PLA), polyhydroxyalkanoates (PHA), and its blend (PLA-PHA) are investigated herein and correlated to their measured structural and physicochemical properties. PLA exhibits the highest stiffness and tensile strength, but lower toughness. The mechanical properties of the PLA-PHA blend were similar to those of PLA, but with a significantly higher toughness. Despite the lower mechanical properties of neat PHA, incorporating a small amount (12 wt.%) of PHA into PLA significantly enhances toughness (approximately 50%) compared to pure PLA. The synergistic effect is attributed to the spherulitic morphology of blended PHA in PLA, promoting interactions between the amorphous regions of both polymers. Thermal stability is notably improved in the PLA-PHA blend, as determined by thermogravimetric analysis. The blend also exhibits lower cold crystallization and glass transition temperatures as compared to PLA, which is beneficial for additive manufacturing. Following additive manufacturing, X-ray photoelectron spectroscopic showed that the three filaments present an increase in C-C and C=O bonds associated with the loss of C-O bonds. The thermal process induces a slight increase in crystallinity in PHA due to chain reorganization. The study provides insights into the thermal and structural changes occurring during the melting process of additive manufacturing.

Effect of the Melicoccus bijugatus leaf and fruit extracts and acidic solvents on the antimicrobial properties of chitosan-starch films.

AIM: Analysing the antimicrobial activity-against food-borne micro-organisms-of modified chitosan-starch films using formic and acetic acid as chitosan solvents and Melicoccus bijugatus leaves and fruit extracts. METHODS AND RESULTS: The films' antimicrobial activity against mesophilic aerobic bacteria, total coliform and fungi were also analysed, in accordance with the Mexican Official Norms (NOM-092-SSA1-1994, NOM-111-SSA1-1994 and NOM-113-SSA1-1994). The pH values of the films and extracts were measured, and the volatile compounds of the extracts and two films were determined by Gas Chromatography-Mass Spectrometry (GC-MS) considering the relationship among the type of compounds, extracts concentration, films' pH and the antimicrobial activity against bacteria and fungi. The best results are obtained by films with formic acid and 10% (v/v) of leaf and fruit extracts, in comparison with untreated chitosan-starch films. CONCLUSIONS: The extracts' compounds improved the films' antimicrobial capacity and inhibited the growth of micro-organisms with no previous sterilization required. It is correlated to the pH of the media, the combination of solvent/extract used and its concentration. SIGNIFICANCE AND IMPACT OF THE STUDY: This is one of the few researches where the antimicrobial activity of M. bijugatus extracts is studied. It was found that the presence of these extracts is capable of improving the antimicrobial activities of chitosan-starch films. The performance of the modified films suggests their potential application as novel food packaging materials and encourages further research.

Novel Crystalline SiO(2) Nanoparticles via Annelids Bioprocessing of Agro-Industrial Wastes.

The synthesis of nanoparticles silica oxide from rice husk, sugar cane bagasse and coffee husk, by employing vermicompost with annelids (Eisenia foetida) is reported. The product (humus) is calcinated and extracted to recover the crystalline nanoparticles. X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and dynamic light scattering (DLS) show that the biotransformation allows creating specific crystalline phases, since equivalent particles synthesized without biotransformation are bigger and with different crystalline structure.

[Contralateral amaurosis and extraocular muscle palsies after retrobulbar injection]. / Ceguera y parálisis de la musculatura extraocular contralateral tras inyección retrobulbar.

CASE REPORT: We report a rare complication of retrobulbar anesthesia in ophthalmic surgery-amarurosis and extraocular muscle palsies in the contralateral eye. Our patient did not suffer permanent sequelae from the injection. DISCUSSION: Numerous complications resulting from retrobulbar injections in the eye and orbit have been reported. One possible explanation of this case is the inadvertent penetration of the subdural or subarachnoid space surrounding the optic nerve and the injection of anesthetic into that space. The drug then tracks along the ipsilateral optic nerve to the chiasm and then to the contralateral optic nerve. Several methods of decreasing the probability of such a complication are discussed.