Expanding production regions of α-form and β-form glycine using an antisolvent crystallization method assisted by N2 fine bubbles

To develop a crystallization technique that can enhance the production of metastable α-form and unstable β-form glycine, we studied the antisolvent crystallization of glycine using the gas–liquid interfaces around N₂ fine bubbles as novel crystallization fields. In the regions near the gas–liquid interfaces, local supersaturation is generated because of the accumulation of glycine and alcohol as an antisolvent as a result of the negative electric charge on the fine bubble surface. Hence, the produced glycine polymorphs change from the stable γ-form to a α-form or β-form glycine. Additionally, local supersaturation at the gas–liquid interfaces can be expected to change via modification of the accumulation of the glycine and alcohol molecules and the interaction of glycine-water-alcohol with the different alcohol additives. At a solution temperature of 303?K, methanol (MeOH), ethanol (EtOH), or isopropanol (IPA) as an antisolvent were rapidly mixed into the saturated glycine solution. While mixing MeOH, EtOH, or IPA with the saturated glycine solution, N₂ fine bubbles with an average size of 10?µm were continuously supplied to the mixed solution using a self-supporting bubble generator and a glycine polymorph was crystallized within 5?min. For comparison, an antisolvent crystallization free of N₂ fine bubbles was conducted using a propeller type mixer. During antisolvent crystallization with/without fine bubble injection, the additional alcohol volume was varied to control the generation rate of the supersaturation in the bulk solution (r_C/CS). Consequently, the production regions of the α-form and β-form glycine were broadened to lower r_C/CS via N₂ fine bubble injection. The expansion behavior for α-form or β-form glycine significantly increased because of the enhancement of local supersaturation at the regions near the gas–liquid interfaces of the N₂ fine bubbles owing to the decreasing carbon number in the alcohol.     

Combustion synthesis of α-Si3N4 assisted by molten salt additives

Combustion synthesis (CS) of silicon nitride (Si₃N₄), assisted by molten salt additives under high N₂ pressure, is reported. The effect of salt additives (NaCl, MgCl₂, and MgCl₂?6H₂O) on the reaction temperature and the final α-Si₃N₄ content is studied. The maximum reaction temperature (T_max) decreased with an increase in the amount of the salt additives. NaCl is found to be the most suitable as it results in 57.8% α-Si₃N₄ at 30 mass% concentration. MgCl₂ is strongly hygroscopic, and MgCl₂?6H₂O decomposes at very low temperature. Therefore, they absorb heat at low temperatures, which makes it difficult to reach the ignition temperature, thereby hindering the reaction propagation. Si₃N₄ is necessary as a diluent for creating pores in the raw materials to allow effective penetration and contact of N₂ gas with the Si particles.     

Characterization of Three Fungal Isomaltases Belonging to Glycoside Hydrolase Family 13 That Do not Show Transglycosylation Activity

α-1,6-Glucosidase (isomaltase) belongs to glycoside hydrolase (GH) families 13 and 31. Genes encoding 3 isomaltases belonging to GH family 13 were cloned from filamentous fungi, Aspergillus oryzae (agl1), A. niger (agdC),and Fusarium oxysporum (foagl1), and expressed in Escherichia coli. The enzymes hydrolyzed isomaltose and α-glucosides preferentially at a neutral pH, but did not recognize maltose, trehalose, and dextran. The activity of AgdC and Agl1 was inhibited in the presence of 1 % glucose, while Foagl1 was more tolerant to glucose than the other two enzymes were. The three fungal isomaltases did not show transglycosylation when isomaltose was used as the substrate and a similar result was observed for AgdC and Agl1 when p-nitrophenyl-α-glucoside was used as the substrate.     

Low-voltage charge pump circuit with double boost technique

In recent years, interest in IoT (Internet of Things) has been increasing, and energy harvesting has attracted attention. However, the power and voltage that can be harvested are very small. Therefore, a power supply circuit is required to solve this problem. In this paper, we have realized a boost circuit that does not require a coil with the aim of integrating all the circuits required for sensing on one chip.     

Harmonic-structured copper: performance and proof of fabrication concept based on severe plastic deformation of powders

Pure copper (Cu) having bimodal ‘harmonic structure’ (HS) was fabricated by a technique based on severe plastic deformation of powders, which involved tailored mechanical milling and spark plasma sintering. The harmonic-structured Cu demonstrates a unique combination of high strength and large elongation superior to its homogeneous as well as bimodal heterogeneous counterparts. Specific features of harmonic structure, i.e. continuous network of ultra-fine grained (UFG) regions encompassing coarse-grained areas, lead to the extension of uniform elongation. The optimum combination of properties in pure Cu is found to be in the harmonic-structured material having 40 % UFG fraction.     

Metal‐Free Regioselective β‐Alkylation of Pyrroles with Carbonyl Compounds and Hydrosilanes: Use of a Brønsted Acid as a Catalyst

A Brønsted acid, trifluoromethanesulfonimide [HN(SO₂CF₃)₂], was found to catalyze reductive β‐alkylation of pyrroles with carbonyl compounds and hydrosilanes. This metal‐free process features lower catalyst loadings compared to the original indium variant and exclusive generation of β‐alkylpyrroles.

     

Modifying the thermal and mechanical properties of poly(lactic acid) by adding lithium trifluoromethanesulfonate

The effect of the addition of lithium trifluoromethanesulfonate (LiCF₃SO₃) on the linear viscoelastic properties, crystallization behavior, and mechanical properties of poly(lactic acid) (PLA) was studied. The glass transition temperature (T_g) was enhanced by adding LiCF₃SO₃, without any loss of transparency of the PLA. This was attributed to the ion-dipole interaction between the lithium cation and oxygen atom in the PLA carbonyl group. The interaction weakened at higher temperature. Consequently, the rheological terminal region was clearly detected, which suggested that the system possessed good melt-processability. The Young’s modulus and yield stress at room temperature were also enhanced by the addition of LiCF₃SO₃, although the toughness was reduced due to the brittle failure. Finally, the presence of LiCF₃SO₃ retarded the crystallization of PLA, because the segmental motion of the PLA chains was reduced.