Sub-wavelength micromachining of silica glass by irradiation of CO<Subscript>2</Subscript> laser with Fresnel diffraction

We investigated a simple and productive micromachining method of silica glass by ablation using a TEA CO₂ laser (10.6 μm) with a spatial resolution down to sub-wavelength scale. The silica glass was irradiated by the TEA CO₂ laser light through a copper grid mask with square apertures of 20×20 μm² attached to the silica glass surface. After the irradiation, circular holes with a diameter of several μm were formed on the silica glass surface at the centers of the apertures due to the Fresnel diffraction effect. The minimum diameter of the holes was 3.4 μm. The characteristics of the micromachining are discussed based on the electric field distributions of the CO₂ laser light under the mask using a three-dimensional full-wave electromagnetic field simulation.     

Similar dissection of sets

In 1994, Martin Gardner stated a set of questions concerning the dissection of a square or an equilateral triangle in three similar parts. Meanwhile, Gardner’s questions have been generalized and some of them are already solved. In the present paper, we solve more of his questions and treat them in a much more general context. Let \({D\subset \mathbb{R}^d}\) be a given set and let f ₁, . . . , f _k be injective continuous mappings. Does there exist a set X such that \({D = X \cup f_1(X) \cup \cdots \cup f_k(X)}\) is satisfied with a non-overlapping union? We will prove that such a set X exists for certain choices of D and {f ₁, . . . , f _k }. The solutions X will often turn out to be attractors of iterated function systems with condensation in the sense of Barnsley. Coming back to Gardner’s setting, we use our theory to prove that an equilateral triangle can be dissected in three similar copies whose areas have ratio 1 : 1 : a for \({a \ge (3+\sqrt{5})/2}\).     

INTRODUCTION OF CATIONIC GROUPS ONTO CARBON BLACK SURFACE AND THEIR DISPERSIBILITY IN WATER

Imidazoline hydrochlonde groups were successfully introduced onto carbon black surface by the treatment of imidazoline groups, which were introduced by the trapping of 2-(2-imidazolin-2-yl)propane radicals formed by the thermal decomposition of 2,2'-azobis[2-(2-imidazolin-2-yl)propane] (AJP) with hydrochloric acid. In addition, arrridine hydrochlonde groups were introduced onto carbon black surface by the radical trapping of 2-methylpropionamidine dihydrochloride radicals formed by the thermal decomposition of 22'-azobis(2-methylpropionamidine) dihydrochloride (AMPAD). The content of imidazoline hydrochlonde and amidine hydrochlonde groups introduced onto carbon black was determined to be 0.6 mmol/g and 0,7 mmol/g, respectively. The mean particle size of AIP/HCl-lreated and AMPAD-treated carbon black was determined to be 31 nm and 16 nm, respectively, by dynamic light scattering method. It was found that the surface of carbon black turned from hydraphobic to hydrophilic by the introduction of cationic moieties and gave a very stable colloidal dispersion in neutral and acidic water at room temperature.     

An Efficient Synthesis of 3-Cyano-1(3H)-Isobehzofuranones

Reaction of o-formyl-N, N-diethylbenzamides (5) with trimethylsilyl cyanide affords the corresponding (0-trimethylsi-lyl)cyanohydrins (6), which on treatment with acetic acid produce 3-cyanophthalides (7) in 80–90% isolated yields.     

Importance of CH/π hydrogen bonds in recognition of the core motif in proline-recognition domains: an ab initio fragment molecular orbital study

We examined CH/π hydrogen bonds in protein/ligand complexes involving at least one proline residue using the ab initio fragment molecular orbital (FMO) method and the program CHPI. FMO calculations were carried out at the Hartree–Fock (HF)/6‐31G*, HF/6‐31G**, second‐order Møller–Plesset perturbation (MP2)/6‐31G*, and MP2/6‐31G** levels for three Src homology 3 (SH3) domains and five proline‐recognition domains (PRDs) complexed with their corresponding ligand peptides. PRDs use a conserved set of aromatic residues to recognize proline‐rich sequences of specific ligands. Many CH/π hydrogen bonds were identified in these complexes. CH/π hydrogen bonds occurred, in particular, in the central part of the proline‐rich motifs. Our results suggest that CH/π hydrogen bonds are important in the recognition of SH3 and PRDs by their ligand peptides and play a vital role in the signal transduction system. Combined use of the FMO method and CHPI analysis is a valuable tool for the study of protein/protein and protein/ligand interactions and may be useful in rational drug design. © 2011 Wiley Periodicals, Inc. J Comput Chem 2011     

Thermolysis,photolysis, and oxidation of an overcrowded 1,3,2-dithiastannetane derivative

Reactions of a sterically crowded 1,3,2-dithiastannetane derivative bearing 2,4,6-tris[bis(trimethylsilyl)methyl]phenyl (=Tbt) and 2,4,6-triisopropylphenyl (=Tip) groups on the tin atom are described. Both thermolysis and photolysis of the 1,3,2-dithiastannetane [Tbt(Tip)SnS₂CPh₂] resulted in the formation of products derived from the corresponding stannanethione [Tbt(Tip)Sn=S], while the oxidation reaction by m -chloroperbenzoic acid gave a novel tincontaining heterocyclic system, an 1,2,4,5-oxadithiastannolane derivative.     

Cover Picture: Electrochemical Lossy Mode Resonance-based Fiber Optic Sensing for Electroactive Species (Electroanalysis 3/2023)

We present an electrochemical-lossy mode resonance (LMR) sensing method that detects refractive indices and electroactive species. The LMR peaks of indium-tin-oxide in the transmittance-wavelength spectra were significantly shifted as the applied potential between 1.0 and −0.5 V at 209 nm/V. The modulation was exploited for sensing the refractive index and electroactive species (ferrocyanide and methylene blue) in two ways: peak-wavelength tracking and potential scanning. The potential-scanning technique produced clear potential LMR peaks in the transmittance-potential spectra for the first time, which were corresponded to the external refractive index. Meanwhile, the limits of detection of ferrocyanide and methylene blue were 7.5 and 25.3 μM, respectively, in peak-wavelength tracking and 18.2 and 20.8 μM, respectively, in the potential scanning technique.