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We have developed the Rh‐catalyzed enantioselective [2+2+2] cycloaddition of homopropargyl enamides (tosylamide‐tethered 1,6‐enynes) with alkynes to construct tetrahydroindole skeletons found in natural alkaloids and pharmaceuticals. This cycloaddition proceeds at room temperature in high yields and regio‐ and enantioselectivity with a broad substrate scope. The preparative scale reaction followed by substituent conversion on the nitrogen atom and the diastereoselective [4+2] cycloaddition with singlet O2 affords hexahydroindole‐diols bearing three stereogenic centers and variable substituents on the nitrogen. Mechanistic studies have revealed that the substituents of the enynes change the ratio of intramolecular and intermolecular rhodacycle formation when using terminal alkynes, varying the ee values of the cycloadducts. [ABSTRACT FROM AUTHOR]

We have developed the Rh‐catalyzed enantioselective [2+2+2] cycloaddition of homopropargyl enamides (tosylamide‐tethered 1,6‐enynes) with alkynes to construct tetrahydroindole skeletons found in natural alkaloids and pharmaceuticals. This cycloaddition proceeds at room temperature in high yields and regio‐ and enantioselectivity with a broad substrate scope. The preparative scale reaction followed by substituent conversion on the nitrogen atom and the diastereoselective [4+2] cycloaddition with singlet O2 affords hexahydroindole‐diols bearing three stereogenic centers and variable substituents on the nitrogen. Mechanistic studies have revealed that the substituents of the enynes change the ratio of intramolecular and intermolecular rhodacycle formation when using terminal alkynes, varying the ee values of the cycloadducts. [ABSTRACT FROM AUTHOR]

We have developed the Rh+/H8‐binap‐catalyzed chemo‐, regio‐, diastereo‐, and enantioselective intermolecular [2+2+2] cycloaddition of three unsymmetric 2π components. Thus, two arylacetylenes react with a cis‐enamide to yield a protected chiral cyclohexadienylamine. Moreover, replacing one arylacetylene with a silylacetylene enables the [2+2+2] cycloaddition of three distinct unsymmetric 2π components. These transformations proceed with excellent selectivity (complete regio‐ and diastereoselectivity and up to >99 % yield and >99 % ee). Mechanistic studies suggest the chemo‐ and regioselective formation of a rhodacyclopentadiene intermediate from the two terminal alkynes. [ABSTRACT FROM AUTHOR]

We have developed the Rh+/H8‐binap‐catalyzed chemo‐, regio‐, diastereo‐, and enantioselective intermolecular [2+2+2] cycloaddition of three unsymmetric 2π components. Thus, two arylacetylenes react with a cis‐enamide to yield a protected chiral cyclohexadienylamine. Moreover, replacing one arylacetylene with a silylacetylene enables the [2+2+2] cycloaddition of three distinct unsymmetric 2π components. These transformations proceed with excellent selectivity (complete regio‐ and diastereoselectivity and up to >99 % yield and >99 % ee). Mechanistic studies suggest the chemo‐ and regioselective formation of a rhodacyclopentadiene intermediate from the two terminal alkynes. [ABSTRACT FROM AUTHOR]

In this study, halloysite nanoclay was subjected to sulfuric acid treatment and used as a reinforcing agent in polyvinyl alcohol (PVA). Halloysite is one of the natural substances that is currently recognized as having a nanotubular structure resembling carbon nanotubes. Halloysite nanotubes are 50 nm in diameter, 0.5–1 μm in length and 15 nm in inner diameter. PVA, a synthetic polymer with characteristics such as biodegradability, water solubility, and transparency, was used as the matrix. The PVA/halloysite films were characterized by tensile test, scanning electron microscopy, and optical transmittance. The tensile strength of PVA/untreated-halloysite film was decreased, although Young’s modulus was increased compared with those of neat PVA film. Sulfuric acid treatment was performed on halloysite to improve its interfacial adhesion with PVA. PVA/halloysite films using halloysite treated for a short time (less than 2 h) had improved tensile strength, Young’s modulus and optical transmittance compared with PVA/untreated-halloysite films, however composite films using halloysite treated for longer times had reduced properties. [ABSTRACT FROM PUBLISHER]

NCN-pincer Ru-complexes containing bis(oxazolinyl)phenyl ligands serve as suitable catalysts in the direct conjugate additions of α,β-unsaturated carbonyl compounds, including ketones, esters, and amides, as well as vinylphosphonates, giving various β-alkynyl carbonyl and phosphonate compounds. A bis(oxazolinyl)phenyl (phebox)-Ru complex also catalyzes the asymmetric conjugate addition of an alkyne with a β-substituted, α,β-unsaturated ketone to produce a chiral β-alkynyl ketone. [ABSTRACT FROM AUTHOR]

Describes an improved large-signal model for predicting the intermodulation distortion power characteristic of MESFET in switching applications. Model of the voltage-dependent drain current and its derivatives such as gate-source and gate-drain capacitors; Symmetric equivalent circuit for switching MESFET.

This paper shows that a pulsed I-V measurement technique is the key to the extraction of large-signal model parameters for a GaAs MESFET operating at microwave frequency. It also shows that the conventional drain current models which have been developed for modeling DC I-V curves do not fit pulsed I-V measurement results accurately. In order to solve this problem, a specially designed drain current model which describes accurately pulsed I-V measurements is presented. The accuracy of the proposed drain current model is verified by comparison between measurements and the modeled characteristics of pulsed I-V data. The comparison reveals that the pulsed I-V measurements are similar to I-V characteristics in microwave operation. The proposed model applies to MMIC power amplifier analysis and verifies the accuracy of the non-linear circuit analysis. © 1998 Scripta Technica. Electron Comm Jpn Pt 2, 80(7): 27–36, 1997 [ABSTRACT FROM AUTHOR]

Reports on extensive measurements of a drain breakdown current as a function of device bias. Proposal of two modeling function and an equivalent circuit controlled by two voltages; Improvement of accuracy of simulation; Nonlinear model; Metal-semiconductor field-effect transistors (MESFET).

A chiral NCN-pincer Ru-complex serves as suitable catalyst in the conjugate addition of alkynes with α,β-unsaturated ketones, esters, and amides, as well as vinylphosphonates. [ABSTRACT FROM AUTHOR]

This paper presents the design and development of highly linear, wide bandwidth mixers. We propose a linearization technique that combines the optimum drain bias condition and multiple-gated transistors for resistive mixers. An on-chip three-line edge-coupled Marchand balun is designed to have low phase and amplitude imbalance for canceling out the even order intermodulation products. Two mixer prototypes: a single-balanced (SB) mixer and a double-balanced (DB) mixer are designed to prove the concepts. The experimental results demonstrate that the SB prototype mixer has a measured conversion loss of less than 11 dB and third-order input intercept point (IIP3) range of 27–33 dBm at 15-dBm LO drive from 7 to 34 GHz. The DB mixer exhibits a conversion loss of less than 11 dB and IIP3 range of 31–35 dBm from 7–26 GHz at 17-dBm LO drive. Both prototypes achieve a high port-to-port isolation of over 30 dB within the operation bandwidth. To the best of our knowledge, the mixers have the highest linearity over the widest bandwidth ever reported. [ABSTRACT FROM PUBLISHER]

Presents a study which described a six-port based wave-correlator which is operated as a two-channel wave receiver. Calibration theory; Structure for wave-correlator; Experimental validation.

In theory, the chip shape distribution changes with the wearing of a grinding wheel in both sur-face and cylindrical grinding processes. However, the relationship between the chip shape distri- bution and wear has not been verified experimentally and quantitatively under any of the grinding techniques. To this end, in this work, chips from repeated cylindrical grinding processes are col-lected. It is noted that the workpiece surface becomes rougher with each repetition. The images of the individual chips, obtained using a particle tracking system are analyzed, and the results indicate that the proportion of small chips and slender chips, respectively known as melted and flow chips, increases when the grinding wheel is worn, which is in contrast to the implications of the established theory. • Focusing on chips to estimate grinding wheel wear. • Developing a device to collect chips during grinding procedure. • Measuring perimeter and area of an enormous number of chips by optical method. • Relationship between chip size and wheel wear revealed here differs from prevailing knowledge. [ABSTRACT FROM AUTHOR]

Focuses on the automatic method for self-calibrating six-port reflectometers. Measurement of the microwaveguides; Use of the impedance synthesis systems; Application of the reflection coefficients.