Precipitate-Accommodated Plasma Nitriding for Aluminum Alloys

Reliable surface treatment has been explored to improve the strength and wear resistance of aluminum alloy parts in automotives. Long duration time as well as long pre-sputtering time are required for plasma nitriding of aluminum or its alloys only, with the thickness or a few micrometers. New plasma inner nitriding is proposed to realize the fast-rate nitriding of aluminum alloys. Al-6Cu alloy is employed as a targeting material in order to demonstrate the effectiveness of this plasma nitriding. Mechanism of fast-rate nitriding process is discussed with consideration of the role of Al2Cu precipitates.     

Dynamic stochastic resonance-based improved logo extraction in discrete cosine transform domain

In this paper, a dynamic stochastic resonance (DSR) technique is used for blind watermark extraction in discrete cosine transform (DCT) domain. The watermark embedding has been done on mid-band DCT coefficients. DSR has been used to improve the robustness of the extraction algorithm by utilizing the degradation introduced during attacks. DSR is an iterative process that tunes the coefficients of the possibly attacked watermarked image so that the effect of noise is suppressed and hidden information is enhanced. Resilience of this technique has been tested in the presence of various attacks. An adaptive optimization procedure has been adopted for the selection of bistable parameters to achieve maximum correlation coefficient under minimum computational complexity. Using the proposed technique, robust extraction of watermark is obtained without trading-off with visual quality of the watermarked image. When compared with the plain DCT-based technique, DSR-based technique has been found to give remarkable performance.     

Repetition rate and center wavelength-tunable optical pulse generation using an optical comb generator and a high-resolution arrayed-waveguide grating

Optical pulse generation using an optical comb generator and a high-resolution arrayed-waveguide grating with 30 integrated phase and amplitude modulators is successfully demonstrated. The repetition rate and the center wavelength of the Gaussian pulse train can be controlled from 9.7 to 10.3 GHz and from 1527 to 1565 nm, respectively.     

Highly Luminescent 2D‐Type Slab Crystals Based on a Molecular Charge‐Transfer Complex as Promising Organic Light‐Emitting Transistor Materials

A new 2:1 donor (D):acceptor (A) mixed‐stacked charge‐transfer (CT) cocrystal comprising isometrically structured dicyanodistyrylbenzene‐based D and A molecules is designed and synthesized. Uniform 2D‐type morphology is manifested by the exquisite interplay of intermolecular interactions. In addition to its appealing structural features, unique optoelectronic properties are unveiled. Exceptionally high photoluminescence quantum yield (Φ _F ≈ 60%) is realized by non‐negligible oscillator strength of the S₁ transition, and rigidified 2D‐type structure. Moreover, this luminescent 2D‐type CT crystal exhibits balanced ambipolar transport (µ _h and µ _e of ≈10^?4 cm² V^?1 s^?1). As a consequence of such unique optoelectronic characteristics, the first CT electroluminescence is demonstrated in a single active‐layered organic light‐emitting transistor (OLET) device. The external quantum efficiency of this OLET is as high as 1.5% to suggest a promising potential of luminescent mixed‐stacked CT cocrystals in OLET applications.     

Measurements of OH radical concentration in combustion environments by wavelength-modulation spectroscopy with a 1.55-microm distributed-feedback diode laser

Wavelength-modulation spectroscopy with a standard commercial 1.55-microm distributed-feedback diode laser was applied to in situ quantitative measurements of OH radical concentration in combustion environments. The second-harmonic (2f) signal was generated from absorption by the P11.5 (nu', nu") = (2, 0) overtone vibrational transition of OH at 6421.354 cm(-1). The absorption occurred in the postflame region of a two-dimensional laminar counterflow burner (Tsuji burner) with a 60-mm line-of-sight path length. The postflame region lies between propane-air premixed twin flames stabilized in the Tsuji burner at various equivalence ratios (phi = 0.65-1.0). The OH concentrations were determined by least-squares fitting of theoretical f line shapes to the experimental counterparts. The measured OH concentrations were in general agreement with adiabatic chemical equilibrium predictions. The lower limit of OH detectivity by multiline deconvolution was limited by ubiquitous unidentified high-temperature H(2)O transitions.     

Optical recording characteristics of molybdenum oxide films prepared by pulsed laser deposition method

Molybdenum-oxide (MoO₃)films were deposited on glass substrates (Corning #7059 with an area of 26 × 38 mm²) by pulsed laser deposition using an ArF excimer laser. It was found that after annealing at 340 °C for 10 min, the film thickness became 2.3 times that (approximately 30 nm) of the as-deposited film thickness. The difference in the transmittance, ΔT, between the annealed state and the as-deposited state was about 40% at a wavelength of 400 nm. X-ray diffraction spectra indicated that oxygen was absorbed into the MoO₃ films through the annealing process. From revolution testing of 30 nm-thick MoO₃ films without a protective layer deposited on a polycarbonate DVD-R disk substrate (120 mm?, 0.6 mm thickness), a write peak-power dependence of carrier-to-noise ratio (CNR) (recording on-land, at λ = 406 nm, NA = 0.65) of the 3T signal (58.5 MHz) was measured at a linear velocity of 5 m/s and a read power of 0.6 mW. Consequently, CNR near 50dB was obtained in the wide write-power margin ΔP of 7 mW (at peak powers between 3.5 and 10.5 mW). From SEM observations, it was recognized that bits of 0.25-0.30 μm size, corresponding to a storage capacity of 7-10GB/in² in the case of NA = 0.65, were formed. For the sample structure with an Al₂O₃ protective layer of ~ 20 nm thickness, a CNR near 50dB was obtained in the peak-power margin ΔP of 12 mW (at peak powers between 6.0 and 18.0 mW). Larger values of the CNR can be obtained if the film thickness of each layer including both the active and protective layers is optimized.     

Two-dimensional correlation analysis of polyimide films using attenuated total reflection-based dynamic compression modulation step-scan Fourier transform infrared spectroscopy

Attenuated total reflection (ATR)-based dynamic compression modulation two-dimensional (2D) correlation study of poly(p-phenylene biphenyltetracarboximide) film is carried out in combination with spectral simulation analysis by density functional theory (DFT). The dynamic 2D infrared (IR) correlation spectra in the region of imide I (C=O stretching mode) show three distinct correlation peaks located around 1777, 1725, and 1708 cm(-1). The band at 1708 cm(-1) is the lower wavenumber shift component of 1777 or 1735 cm(-1) peaks and is attributed to the results from intermolecular interactions, according to the DFT analysis. The 1708 cm(-1) band also shows the largest dynamic response, suggesting that these intermolecular interactions may enhance the dynamic response. The dynamic 2D IR correlation spectra in the region of imide II (C-N-C axial stretching mode) vibrations also show three correlation peaks located around 1335, 1355, and 1370 cm(-1), although the imide II band is shown to consist substantially of one component by the DFT analysis. These multiple peaks may be attributed to the compression-induced wavenumber shift of the band in the backbone structures. The sequential analysis of 2D correlation data show that, upon applying the dynamic compression, the response of the backbone regions (imide II) occurs first, followed by that of the side-chain regions (imide I, C=O).     

Porous TiO<Subscript>2</Subscript> nanostructures synthesized from peroxotitanic acid-derived anatase

Abstract  

Titania/titanate nanotubes and nanoplates were prepared by an alkali hydrothermal method using the powder and the sol of peroxotitanic acid-derived anatase, respectively, as precursors. XRD patterns and Raman spectra showed that both nanotubes and nanoplates are of titanate structure with the latter involving a slight part of anatase phase. These nanotubes and nanoplates are highly mesoporous based on nitrogen adsorption measurement. After calcination at 823 K, nanotubes were transformed into nanorods, and nanoplates into spherical particles, both of which are pure anatase-type titania. The nanorod material exhibits an enhanced photocatalytic activity in comparison with the spherical particles.     

Comparison of the sequence-selective DNA binding by peptide dimers with covalent and noncovalent dimerization domains

Sequence-specific DNA binding proteins generally consist of more than two DNA-contacting regions to ensure the selectivity of recognition. The multiple DNA binding modules are connected either through the covalent linker or through the noncovalent dimerization domain. We have compared the DNA binding of peptide dimers with covalent and noncovalent dimerization domains to explore the potential advantage of each linkage on the sequence-specific DNA binding. Three sets of head-to-tail peptide dimers were synthesized by using the same basic region peptide to target the same DNA sequence; one dimer was assembled with a bridged biphenyl derivative as a covalent dimerization domain, and two other dimers were assembled with the cyclodextrin guest noncovalent dimerization domains. One of the noncovalent dimers was a heterodimer that consisted of cyclodextrin and guest peptides, while the other was a homodimer that consisted of peptides bearing both cyclodextrin and the guest molecule within the same chain. Both noncovalent dimers formed the specific DNA complexes within narrower ranges of peptide concentrations and showed higher sequence selectivity than the covalent dimer did. Among the three dimers, the noncovalent homodimer that can form an intramolecular inclusion complex showed the highest sequence selectivity. Because the noncovalent homodimer with the higher stability of the circular intramolecular inclusion complex exhibited the higher sequence selectivity, it was concluded that an equilibrium involving a conformational transition of a monomeric peptide effectively reduced the stability of its nonspecific binding complex, hence increasing the efficacy of cooperative dimer formation at the specific DNA sequence.