Estimation methodology for amplitude of second-order harmonic in nonlinear surface acoustic wave measured by optical diffraction method

An estimation methodology for amplitude from the fundamental to fourth-order harmonic composed of nonlinear surface acoustic waves on a LiNbO₃ substrate with a 128° Y-X propagation axis was demonstrated. First, equations for estimation of amplitudes from diffracted light intensity were shown and then numerical simulations of main factors were carried out. Normalized diffraction light intensities due to components of nonlinear surface acoustic waves were measured and their amplitudes were obtained from measured values. Finally, the amplitude of the second harmonic propagating on a gold thin film of about 50 nm thickness was estimated. It was found that the amplitude of the second harmonic increased continuously from 0.8 to 2.0 Å with propagation distance in the thin film.     

Comparison between blue and green stimulated luminescence of Al2O3:C

This paper presents a systematic comparison of OSL signals from Al₂O₃:C when stimulated with blue and green light. Al₂O₃:C detectors were irradiated with various doses and submitted to various bleaching regimes using yellow, green and blue light. Most of the investigations were carried out using Luxel?-type detectors used in the commercial Luxel? and InLight? dosimetry systems (Landauer Inc.). Al₂O₃:C single crystals and Al₂O₃:C powder were also used to complement the investigations. The results show that, although blue stimulation provides faster readout times (OSL curves that decayed faster) and higher initial OSL intensity than green stimulation, blue stimulation introduced complicating factors. These include incomplete bleaching of the dosimetric trap when the Al₂O₃:C detectors are bleached with yellow or green light and the OSL is recorded with blue light stimulation, and an increased residual level due to stimulation of charge carriers from deep traps. The results warrant caution when using blue stimulation to measure the OSL signal from Al₂O₃:C detectors, particularly if the doses involved are low and the detectors have been previously exposed to high doses.     

Effect of TiO2 addition on the chemical durability of Bi2O3–SiO2–ZnO–B2O3 glass system

The effect of the substitution of ZnO for TiO₂ on the chemical durability of Bi₂O₃–SiO₂–ZnO–B₂O₃ glass coatings in hot acidic medium (0.1 N H₂SO₄ at 80 °C) for different times was studied. The thick films produced by a screen-printing method and heat treated at 700 °C/5 min were analyzed by X-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy. The glass from the Bi₂O₃–SiO₂–ZnO–B₂O₃ system developed Zn₂SiO₄ and a glassy phase that were readily attacked by hot 0.1 N sulfuric acid, whereas the heat treated coating from the Bi₂O₃–SiO₂–TiO₂–ZnO–B₂O₃ system presented a finer microstructure with thin interconnected Bi₄Ti₃O₁₂ crystals and a glassy phase more resistant to hot 0.1 N sulfuric acid attack etching.     

Cationic and Anionic Effects on the Glass Transition Temperature for Aqueous Electrolyte Solutions

Glass-forming composition regions of aqueous CH₃COOM (M = Li, Na, K, Rb, Cs, and Tl), CF₃COOM (M = Li, Na, K, Rb, and Cs), and Et₄NX (Et₄ = C₂H₅, X = OH, CH₃COO, Cl, Br, NO₃, and SCN) solutions are reported as a function of water concentration R (R = moles of water per moles of salt). Glass transition temperatures (T _g) were measured by a simple differential thermal analysis (DTA) method with a cooling rate of about 600 K-min^–1. The T _g of all solutions decrease with increasing R (decreasing salt concentration). It is found that T _g at the same R value decrease in the order Na⁺ > Li⁺ > K⁺ > Rb⁺ > Cs⁺ in all glass-forming composition regions of the alkali acetate salt and alkali trifluoroacetate salt solutions. T _g for Et₄NX solutions decrease in the order CH₃COO^– ~OH^– > Cl^– > Br^– > NO ₃ ^– > SCN^–. The effects of the cation and anion on the glass-forming behavior in these aqueous solutions are discussed.     

A Soluble C60 Graphite Segment

At the limits of analytical investigation one finds the nanodimensional C₆₀ graphite segment 1 , which, thanks to its long-chain alkyl substituents, is soluble. Monolayers of 1 on graphite can be characterized by scanning tunneling microscopy.     

Design,Synthesis and Biological Evaluation of Simplified Analogues of the Major Corn Strigolactones,Zealactone and Zeapyranolactone

Strigolactones are one of the phytohormones, which have multiple activities on plant growth and development. Since these strigolactone activities are highly associated with crop yield, use of strigolactone could be a promising technology in modern sustainable agriculture. The major strigolactones in corn root exudates have been identified as zealactone 1a/b and zeapyranolactone. We recently disclosed the first total synthesis of zealactone 1a/b together with its biological activity in corn. Herein, we describe the design and synthesis of simplified analogues of both corn-derived strigolactones with their bioavailability in soil and their biological activities. These compounds would be potential leads for the development of synthetic strigolactones for the agronomical use in a more sustainable crop production.     

In situ Raman and optical microscopy of the relaxation behavior of amorphous ices under pressure

The transformation of low‐density amorphous (LDA) ice produced from high‐density amorphous (HDA) ice was studied up to 400 MPa as a function of temperature by in situ Raman spectroscopy and optical microscopy. Changes in these amorphous states of H₂O were directly tracked without using emulsions to just above the crystallization temperature T_x. The spectra show significant changes occurring above ∼125 K. The results are compared with data reported for the relaxation behavior of HDA, to form what we call relaxed HDA, or rHDA. We find a close connection with expanded HDA (eHDA), which is reported to exist as another metastable form in this P–T region. The observation of this temperature‐induced LDA transition under pressure complements the previously observed pressure‐induced reversible transition between LDA and HDA at 120–140 K. Copyright © 2009 John Wiley & Sons, Ltd.     

Application of alkoxy-λ6-sulfanenitriles as strong alkylating reagents

Alkoxy-λ⁶-sulfanenitriles were found to be versatile alkylating reagents toward various nucleophiles bearing at least one proton such as methanol, phenol, thiophenols, carboxylic acids, p-toluenesulfonic acid, hydrochloric acid, and primary and secondary amines. Reactivity of the alkoxy group of the λ⁶-sulfanenitriles showed an opposite trend to the usual S_N2 character, i.e. Me ( 1a ), Pr ( 1b ), and Bu ( 1d ) ≪ i-Pr ( 1c ). In the presence of p-TsOH, alkyl tosylates were predominantly formed instead of the alkylation products of nucleophiles. In addition, even a sterically hindered substrate, neopentyloxy-λ⁶-sulfanenitrile, was found to undergo an S_N2 reaction toward thiophenol without any rearrangement product to give neopentyl phenyl sulfide in good yield. © 2004 Wiley Periodicals, Inc. Heteroatom Chem 15:193–198, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20006