Home About us Contact
|
Home About us Contact | ||
|
|
||
Little Amount (little + amount)
Selected AbstractsDifferential Pulse Voltammetric Determination of Selenocystine Using Selenium-gold Film Modified ElectrodeELECTROANALYSIS, Issue 17 2005Yan Bai Abstract Differential pulse voltammetric determination of selenocystine (SeC) using selenium-gold film modified glassy carbon electrode ((Se-Au)/GC) is presented. In 0.10,mol,L,1 KNO3 (pH,3.20) solution, SeC yields a sensitive reduction peak at ,740,mV on (Se-Au)/GC electrode. The peak current has a linear relationship with the concentration of SeC in the range of 5.0×10,8,7.0×10,4,mol,L,1, and a 3, detection limit of SeC is 3.0×10,8,mol,L,1. The relative standard deviation of the reduction current at SeC concentration of 10,6,mol,L,1 is 3.88% (n=8) using the same electrode, and 4.19% when using three modified electrodes prepared at different times. The content of SeC in the selenium-enriched yeast and selenium-enriched tea is determined. The total selenium in ordinary or selenium-enriched tea is determined by DAN fluorescence method. The results indicate that in selenium-enriched yeast about 20% of total selenium is present as SeC and in selenium-enriched tea SeC is the major form of selenoamino acids. The total selenium content in selenium-enriched tea soup is 0.09,,gSe/g accounting by 7% compared with that in selenium-enriched tea. Hence, only a little amount of selenium is utilized by drinking tea, and most selenium still stay in tealeaf. Uncertainty are 22.4% and 16.1% for determination of SeC in selenium-enriched yeast and selenium-enriched tea by differential pulse voltammetry (DPV) on (Se-Au)/GC electrode, respectively. [source] Synthesis and Luminescence Properties of Orange,Red-Emitting M2Si5N8:Eu2+ (M=Ca, Sr, Ba) Light-Emitting Diode Conversion Phosphors by a Simple Nitridation of MSi2INTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 4 2009Hui-Li Li Eu2+ -doped M2Si5N8 (M=Ca, Sr, Ba) orange,red phosphors were successfully prepared by a simple, direct, and efficient solid-state reaction using air-stable MSi2, Eu2O3, and ,-Si3N4 as the starting materials under N2,H2 (5%) atmosphere. The influence of the type of the alkaline-earth ion on the phase structure and luminescence properties has been investigated. The results show that the synthesized powders have a single-phase crystal structure of M2Si5N8 for M=Ca, Sr, and a little amount of BaSi7N10 impurity phase for M=Ba. Under the blue light excitation, M2Si5N8:Eu2+ shows a typical broad band emission of Eu2+ ranging from orange to red (585,620 nm) depending on the type of M ion. The emission intensity, conversion efficiency, and thermal stability increase with the sequence of Ca Synergistic effects of , -cyclodextrin containing silicone oligomer on intumescent flame retardant polypropylene systemPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 10 2010Huanfeng Wang Abstract The effects of , -cyclodextrin containing silicone oligomer(CDS), as a synergistic agent, on the flame retardancy and mechanical properties of intumescent flame retardant polypropylene composites were studied by adding different amounts of CDS in intumescent flame retardants. The limiting oxygen index (LOI), UL-94 test, thermogravimetric analysis (TGA), and scanning electron microscopy (SEM) were utilized to evaluate the synergistic effects of CDS in the composites. It was found that after a little amount of CDS partially replaced a charring-foaming agent (CFA) in IFR, LOI values of the composites were enhanced and they obtained a UL-94 V-0 rating. IFR system containing 6.25wt% CDS presented the best flame retardancy in PP. The experimental results obtained from LOI and UL-94, TGA, SEM, and mechanical properties indicated that the combination of CDS and CFA presents synergistic effects in flame retardancy, char formation, and mechanical properties of the composites. This is probably due to different structures of polyhydroxyl macromolecules (CDS and CFA), the existence of dimethyl silicone group in CDS, and the toughness of epoxy silicon chain in CDS. SEM results proved that the interfacial compatibility between IFR and PP was improved by CDS. Copyright © 2009 John Wiley & Sons, Ltd. [source] Role of uric acid in different types of calcium oxalate renal calculiINTERNATIONAL JOURNAL OF UROLOGY, Issue 3 2006FÉLIX GRASES Aim:, The presence of uric acid in the beginning zone of different types of ,pure' calcium oxalate renal calculi was evaluated with the aim of establishing the degree of participation of uric acid crystals in the formation of such calculi. Methods:, The core or fragment of different types of ,pure' calcium oxalate renal calculi was detached, pulverized and uric acid extracted. Uric acid was determined using a high-performance liquid chromatography/mass spectrometry method. Results:, In calcium oxalate monohydrate (COM) papillary calculi with a core constituted by COM crystals and organic matter, 0.030 ± 0.007% uric acid was found in the core. In COM papillary calculi with a core constituted by hydroxyapatite, 0.031 ± 0.008% uric acid was found in the core. In COM unattached calculi (formed in renal cavities) with the core mainly formed by COM crystals and organic matter, 0.24 ± 0.09% uric acid was found in the core. In COM unattached calculi with the core formed by uric acid identifiable by scanning electron microscopy (SEM) coupled to X-ray microanalysis, 20.8 ± 7.8% uric acid was found in the core. In calcium oxalate dihydrate (COD) unattached calculi containing little amounts of organic matter, 0.012 ± 0.004% uric acid was found. In COD unattached calculi containing little amounts of organic matter and hydroxyapatite, 0.0030 ± 0.0004% of uric acid was found. Conclusions:, From these results it can be deduced that uric acid can play an important role as inducer (heterogeneous nucleant) of COM unattached calculi with the core formed by uric acid identifiable by SEM coupled to X-ray microanalysis (these calculi constitute the 1.2% of all calculi) and in COM unattached calculi with the core mainly formed by COM crystals and organic matter (these calculi constitute the 10.8% of all calculi). [source]
| | |||||||||