Microdrilling and micromachining with diode-pumped solid-state lasers

The trend of the ever-continuing miniaturization requires fast and flexible processing tools. Lasers are flexible tools which have proven their reliability in manufacturing of macrofeatures for many years already. However, to process small features the requirements of the laser source, e.g. in regard to the beam profile, are very high. Innovative laser sources which meet these requirements, such as diode-pumped solid-state lasers, and the progress in processing technology, have made microfeature processing commercially viable during recent years. Examples of industrial applications are laser-drilled micro-injection nozzles for highly efficient automobile engines or manufacturing of complex spinnerets for production of synthetic fibers. The unique advantages of laser-based techniques stem from their ability to produce high-aspect-ratio holes, while yielding small heat-affected zones with exceptional surface quality, roundness and taper tolerances. Additionally, the ability to drill blind holes and slots in very hard materials such as diamond, silicon, sapphire, ceramics and steel is of great interest for many applications in the microelectronics, semiconductor and automotive industries. This kind of high-quality, high-aspect-ratio micromachining requires high peak powers and short pulse durations. PACS 42.55.Xi; 42.62.Cf; 81.40.-z     

UV absorption and fluorescence properties of fused aromatic hydrocarbons having trimethylsilyl, trimethylgermyl, and trimethylstannyl groups

Effects of trimethylsilyl, trimethylgermyl, and trimethylstannyl substituents attached to fused aromatic hydrocarbons such as pyrene, anthracene, phenanthrene, and naphthalene were studied in terms of UV absorption and fluorescence properties in aerated cyclohexane solutions. Absorption maxima of trimethylsilyl-, trimethylgermyl-, and trimethylstannyl-substituted aromatic hydrocarbons shifted to longer wavelengths than those of unsubstituted ones. Absorption maxima of mono-, bis-, tris-, and tetrakis(trimethylsilyl)pyrenes shifted to longer wavelength consecutively at intervals of 10 nm. Fluorescence intensities and fluorescence lifetimes of trimethylsilyl-substituted aromatic hydrocarbons were larger and longer than those of unsubstituted ones, and they decreased in the order of Me₃SiAr > Me₃GeAr > Me₃SnAr. Fluorescence intensity of 1,3,6,8-tetrakis(trimethylsilyl)pyrene was largest among those of a series of mono-, bis-, tris-, and tetrakis(trimethylsilyl)pyrenes under aerated conditions.     

Granulation of core particles suitable for film coating by agitation fluidized bed I. Optimum formulation for core particles and development of a novel friability test method

To prepare powdered medicines without bitter taste, film coating is required to cover the surface of core particles. In this study, effect of formulation and operating conditions of agitation fluidized bed on the core particle properties was investigated. In order to prevent breakage of the core particles during coating process, which sometimes causes variation of drug dissolution rate, addition of maltose syrup powder during the formulation process of the core particles was investigated. Also, a method for friability test in which the core particles were subjected to strong impact was proposed to evaluate strength of the core particles. The friability of the core particles determined by this test method correlated well with the actual friability of the particles during the coating process. Based on this result, we confirmed this novel friability test method could predict the core particle endurance during the coating process.     

An efficient novel synthesis of beta-(azuleno[1,2-b]benzothienyl)- and beta-(azuleno[2,1-b]benzothienyl)-alpha,beta-unsaturated ketones by the tropylium ion-mediated intramolecular furan ring-opening reaction and X-ray investigation of methyl ketone derivative

Intramolecular reaction of 2-tropylio-3-(5-substituted 2-furyl)benzothiophenes (3), prepared from the corresponding 2-cycloheptatrienyl-3-(5-substituted 2-furyl)benzothiophenes (2), afforded the beta-(azuleno[1,2-b]benzothienyl)-alpha,beta-unsaturated ketones (4), which are otherwise difficult to obtain, in moderate yields. The reaction involves a ring-opening process of the furan ring by intramolecular attack of the tropylium ion onto the 2-position of the furan ring. Similarly, beta-(azuleno[2,1-b]benzothienyl)-alpha,beta-unsaturated ketones (8) were obtained from the corresponding 3-tropylio-2-(5-substituted 2-furyl)benzothiophenes (7) albeit in lower yields. The molecular and crystal structures of the methyl ketone derivative, 8a, are discussed on the basis of X-ray structure analysis.     

Preparation,crystal structure,and spectroscopic,chemical, and electrochemical properties of (2E,4E)-1,4-di(3-guaiazulenyl)-1,3-butadiene compared with those of (E)-1,2-di(3-guaiazulenyl)ethylene

Wittig reaction of (E)-3-(3-guaiazulenyl)propenal (11) with (3-guaiazulenylmethyl)triphenylphosphonium bromide (9) in ethanol containing NaOEt at 25 °C for 24 h under argon gives the title new (2E,4E)-1,3-butadiene derivative 4, in 33% isolated yield, which upon treatment with hexafluorophosphoric acid (i.e., 65% HPF₆ aqueous solution) in tetrahydrofuran (=THF) at 25 °C for 1 h under aerobic conditions affords a new air (two-electron) oxidation product (E)-ethylene-1,2-bis(3-guaiazulenylmethylium) bis(hexafluorophosphate) (14), quantitatively, and further, zinc-reduction of 14 in trifluoroacetic acid (=CF₃COOH) at 0 °C for 1 h under argon reverts 4, quantitatively. Along with the above interesting results, our discovered another preparation method, spectroscopic properties, crystal structure, and electrochemical behavior of 4, which serves as a strong two-electron donor and acceptor, compared with those of the previously reported (E)-1,2-di(3-guaiazulenyl)ethylene (3) are documented in detail.     

Stellatolide H,a cytotoxic peptide lactone from a deep-sea sponge Discodermia sp.

Stellatolide H (1) was isolated from a deep-sea sponge Discodermia sp. as the cytotoxic constituent. The planar structure of 1 was elucidated on the basis of the NMR spectroscopic and mass spectrometric data. The absolute configurations of the constituent amino acid residues were determined by the Marfey’s method. Stellatolide H (1) is a peptide lactone of the callipeltin class with its N-terminus blocked by 3-hydroxy-6,8-dimethyldeca-(4Z,6E)-dienoic acid (Hdda).     

Phosphine‐Catalyzed anti‐Carboboration of Alkynoates with 9‐BBN‐Based 1,1‐Diborylalkanes: Synthesis and Use of Multisubstituted γ‐Borylallylboranes

Trialkylphosphine organocatalysis has enabled the regioselective anti‐carboboration of alkynoates with 9‐BBN‐based 1,1‐diborylalkanes to produce secondary allylboranes with β‐alkoxycarbonyl and γ‐boryl substituents. The utility of the densely functionalized allylboranes was demonstrated by the highly diastereoselective allylation of N‐(trimethylsilyl)aldimines to produce homoallylamines containing tertiary allylborane and acrylate moieties.     

GPU-accelerated molecular dynamics simulation for study of liquid crystalline flows

We have developed a GPU-based molecular dynamics simulation for the study of flows of fluids with anisotropic molecules such as liquid crystals. An application of the simulation to the study of macroscopic flow (backflow) generation by molecular reorientation in a nematic liquid crystal under the application of an electric field is presented. The computations of intermolecular force and torque are parallelized on the GPU using the cell-list method, and an efficient algorithm to update the cell lists was proposed. Some important issues in the implementation of computations that involve a large number of arithmetic operations and data on the GPU that has limited high-speed memory resources are addressed extensively. Despite the relatively low GPU occupancy in the calculation of intermolecular force and torque, the computation on a recent GPU is about 50 times faster than that on a single core of a recent CPU, thus simulations involving a large number of molecules using a personal computer are possible. The GPU-based simulation should allow an extensive investigation of the molecular-level mechanisms underlying various macroscopic flow phenomena in fluids with anisotropic molecules.