Rapid quantification of cellular flavonoid levels using quercetin and a fluorescent diphenylboric acid 2-amino ethyl ester probe

Flavonoids are abundant in fruits and vegetables and have various biological activities. A rapid, sensitive method for assessing cellular quercetin levels is necessary because cellular levels are often low. A new method for measuring cellular flavonoid levels is proposed using diphenylboric acid 2-aminoethyl ester (DPBA), a fluorescent probe, and quercetin, a representative flavonoid. This spectrofluorometry-based assay is simple and allows rapid quantification of the cellular quercetin content with high sensitivity. CHO-K1 cells were incubated with quercetin for 5 min, and then the cellular quercetin concentration was assayed using DPBA spectrofluorometry. Results, compared with high-performance liquid chromatography (HPLC), thin layer chromatography (TLC), and conventional spectrophotometry measurements, were highly correlated with HPLC data (R>0.99). The method is more sensitive than TLC and conventional spectrophotometry. Spectrofluorometric measurement using DPBA is a simple, rapid, and sensitive method for assessing cellular quercetin levels.     

Precipitation of Second Phases in High-Interstitial-Alloyed Austenitic Steel

The precipitation reaction of an austenitic stainless steel containing N + C was investigated using transmission electron microscopy. The main precipitate formed during isothermal aging at 1123 K (850 °C) was M₂₃C₆ carbide, and its morphology gradually changed in a sequence of intergranular (along grain boundary) → cellular (or discontinuous) → intragranular (within grain interior) form with aging time. Irrespective of different morphologies, the M₂₃C₆ was consistently related to austenite matrix in accordance with the cube-on-cube orientation relationship. Based on the analysis of electron diffraction, two variants of intragranular M₂₃C₆ were identified, and they were related to each other by twin relation. Prolonged aging produced other types of precipitates—the rod-shaped Cr₂N and the coarse irregular intermetallic sigma phase. The similarities and differences in precipitation behavior between N only and N + C alloyed austenitic stainless steels are briefly discussed.     

Interleaver optimization of convolutional turbo code for 802.16 systems

Convolutional turbo code (CTC) has been adopted as an optional channel coding scheme for wireless metropolitan area networks (WMAN) and digital video broadcasting (DVB) owing to its powerful error correction capability and flexibility. In spite of the fact that the internal interleaver of CTC mainly affects the characteristics of the code, interleaving parameters, especially for small and moderate block sizes, have not been fully optimized in terms of performance. In this paper, we investigate structural behavior of interleaving parameters and suggest several optimization methodologies for the CTC interleaver of 802.16 systems. Simulation shows that power gains up to 0.7 dB can be acquired at a target frame error rate of 10^?5 by only substituting the newly optimized parameters for the current ones.     

Toxicological evaluation of the isoflavone puerarin and its glycosides

Puerarin, an isoflavone derived from kudzu roots, has strong biological activities. However, its bioavailability in vivo is often limited by its insolubility. A novel transglycosylase increases the solubility of puerarin >100-fold, by converting it to puerarin glycosides. Since over-consumption of an isoflavone might have toxic effects, therefore, we investigated the potential antimutagenic activity, bone marrow micronucleus test, and a 28-day oral repeated administration test with puerarin and its glycosides. In Ames tests, neither puerarin nor its glycosides exhibited mutagenic effects up to 200 μg/plate. Puerarin and its glycoside, glucosyl-α-(1,6)-puerarin, significantly reduced the mutagenic effect of 4-nitroquinoline-1-oxide by up to 41%. In bone marrow micronucleus tests using ICR mice, neither puerarin nor glucosyl-α-(1,6)-puerarin interfered with erythrocyte production in the bone marrow. Both compounds decreased the prevalence of polychromatic erythrocytes. Sprague–Dawley rats were orally dosed with puerarin and its glycosides daily for 28 days. Neither puerarin nor its glycosides caused significant alterations in histology, and biochemical and hematologic parameters. These results suggest that puerarin and its glycosides do not have significant toxic effects, at least in rodents, either in vitro or in vivo at doses of up to 250 mg/kg per day.     

Isothermal Decomposition of Ferrite in a High-Nitrogen,Nickel-Free Duplex Stainless Steel

The formation and crystallography of second phases during isothermal decomposition of ferrite (α) in a high-nitrogen, nickel-free duplex stainless steel was examined by means of transmission electron microscopy (TEM). At an early stage of aging, the decomposition of α started along the α/γ phase boundaries where sigma (σ) phase and secondary austenite (γ ₂) precipitated in the form of an alternating lamellar structure. The combined analyses based on the simulation of diffraction patterns and stereographic projection have shown that most of the σ phase was related to the γ ₂ by the following relation: (111)_g ||(001)_s (111)_{\gamma } \parallel (001)_{\sigma } and [10[`1]]<sub>g</sub> ||[110]<sub>s</sub> . [10\bar{1}]_{\gamma } \parallel [110]_{\sigma } . The intergranular and intragranular precipitation of Cr<sub>2</sub>N with trigonal structure were identified, and the orientation relationships (ORs) with α and γ matrix could be expressed as ( 110 )<sub>a</sub> ||( 0001 )<sub>\textCr2 \textN</sub> \left( {110} \right)_{\alpha } \parallel \left( {0001} \right)_{{{\text{Cr}}_{2} {\text{N}}}} , [ [`1]11 ]_a ||[[`1]100]<sub>\textCr2 \textN</sub>  ; (111)<sub>g</sub> ||(0001)<sub>\textCr2 \textN</sub> \left[ {\bar{1}11} \right]_{\alpha } \parallel [\bar{1}100]_{{{\text{Cr}}_{2} {\text{N}}}} \,;\,(111)_{\gamma } \parallel (0001)_{{{\text{Cr}}_{2} {\text{N}}}} , and [ [`1]10 ]_g ||[ [`1]100 ]_{\textCr2 \textN} , \left[ {\bar{1}10} \right]_{\gamma } \parallel \left[ {\bar{1}100} \right]_{{{\text{Cr}}_{2} {\text{N}}}} , respectively. The precipitation of intermetallic χ phase was also observed inside the α matrix, and they obeyed the cube-on-cube OR with the α matrix. Prolonged aging changed both the structure of matrix and the distribution of second phases. The γ ₂, formed by decomposition of α, became unstable because of the depletion of mainly N accompanied by the formation of Cr₂N, and it transformed into martensite after subsequent cooling. As a result, the microstructure of the decomposed α region was composed of three kinds of precipitates (intermetallic σ,χ, and Cr₂N) embedded in lath martensite.     

Effect of molybdenum and chromium on hardenability of low-carbon boron-added steels

The hardenability of low-carbon boron-added steels containing molybdenum or chromium was studied using dilatometry, thermodynamic calculations, and secondary ion mass spectroscopy (SIMS). The combined addition of boron and molybdenum was found to be more effective than that of boron and chromium in enhancing the hardenability of boron-added steels. In particular, the addition of 0.5 wt.% molybdenum to the boron-added steel almost completely suppressed the formation of polygonal ferrite even at a slow cooling rate of 0.5°C/s. The synergistic effect of the combined addition of molybdenum and boron is thought to be due to both the suppression of M₂₃(C,B)₆ precipitation resulting from the deterioration of phase stability and the reduction of carbon diffusivity by the molybdenum addition.     

Fatigue crack propagation behavior of friction stir welded 5083-H32 Al alloy

Fatigue crack propagation (FCP) behavior of friction stir welded (FSWed) 5083-H32 Al alloy was examined with the fatigue crack growing either along the dynamically recrystallized zone (DXZ) at variable ΔK or perpendicular to the DXZ at a constant ΔK value of 10, 13, 15, and 17 MPa√m, respectively. The FCP behavior of FSWed 5083-H32 specimen is substantially influenced by the presence of FSW zone, the trend of which is discussed based on residual stress measurement and fractographic observation.     

Crystallographic details of precipitates in Fe-22Cr-21Ni-6Mo-(N) superaustenitic stainless steels aged at 900 °C

Crystallographic features of second phases and the effect of nitrogen addition on the microstructural evolution in superaustenitic Fe-22Cr-21Ni-6Mo-(N) (all in wt pct) stainless steels during isothermal aging at 900 °C were investigated using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Both alloys with and without nitrogen contained sigma phase and M₂₃C₆ carbides in the solution treated condition. While four phases (sigma, M₂₃C₆, M₆C, and chi) of intermetallics and carbides appeared sequentially as a function of aging time in the nitrogen-free alloy, two nitrides (Cr₂N and AlN) were additionally observed after long time aging of the nitrogen-containing alloy. The addition of nitrogen into Fe-22Cr-21Ni-6Mo steel promoted a finer and more uniform distribution of precipitates during isothermal aging. The exact identification and crystallography of various second phases were confirmed from the analyses of selected area diffraction patterns from various orientations, stereographic projection, and energy dispersive spectroscopy. The orientation relationships between the precipitates and austenite matrix can be summarized as follows: (1) two carbides (M₂₃C₆ and M₆C): cube-on-cube orientation relationship; (2) chi phase: Kurdjumov-Sachs (K-S) orientation relationship; (3) two nitrides (Cr₂N and (AlN): (11 0)_nitrides //(211) _γ and [0001]_nitrides //[ 11] _γ ; and (4) sigma phase: (1) ( 11) _γ //(00 ) _σ and [ 0] _γ //[ 0] _σ or (2) ( 10) _γ //( 10) _σ and [ 2] _γ //[113] _σ . For the sigma phase, the former orientation relationship was predominant throughout aging, and the latter orientation relationship was occasionally observed under limited aging conditions.