微胶囊红磷的制备及在PP中的阻燃应用

以三聚氰胺甲醛预聚体(MFP)与红磷粉末为原料,过硫酸钾(KPS)为催化剂,采用原位聚合法成功制备出具有高热稳定性的微胶囊红磷(MRP)。通过DSC,SEM,FTIR及XPS等分析手段研究了红磷微胶囊化效果。结果表明,KPS的加入有助于提高MFP的反应活性,使三聚氰胺甲醛树脂有效地包覆在红磷颗粒表面,缩短了反应时间,且此时制备的MRP包覆效果最佳,其氧化反应峰温为480℃,较红磷原料要高出很多,可使用范围变宽。采用熔融挤出法制备了多组不同配方的聚丙烯(PP)复合材料。研究发现,MRP或氢氧化镁(MH)单独使用时阻燃效率低,将它们复配使用后能有效地提高材料的阻燃性能。当PP∶MRP∶MH=100分(phr)∶15(phr)∶50(phr)时,MRP/MH/PP复合材料的极限氧指数为26%,垂直燃烧达到UL-94标准的V-0级。此外,还探讨了可能的阻燃机理。     

Polymer microenvironmental effects on the photophysics of cinchonine dication

Photophysical properties of cinchonine dication (C⁺⁺) have been studied in protic and aprotic polymers by monitoring steady state and time resolved measurements. It is found to be sensitive towards the microenvironment of polymers. Edge excitation red shifted emission (EERS) is observed in all polymeric matrices. However, the magnitude of EERS is relatively high in protic as compared to aprotic polymer. Isobestic point in excitation spectra and three decay components in time resolved measurements indicate more than two trapped chemical species in the heterogeneous environment of the polymer. Solute-polymer interactions are found to produce the third decay channel, unlike in solution phase and may be useful to understand the polymer microenvironment.     

Covering homology

We introduce the notion of covering homology of a commutative S-algebra with respect to certain families of coverings of topological spaces. The construction of covering homology is extracted from Bökstedt, Hsiang and Madsen's topological cyclic homology. In fact covering homology with respect to the family of orientation preserving isogenies of the circle is equal to topological cyclic homology. Our basic tool for the analysis of covering homology is a cofibration sequence involving homotopy orbits and a restriction map similar to the restriction map used in Bökstedt, Hsiang and Madsen's construction of topological cyclic homology.Covering homology with respect to families of isogenies of a torus is constructed from iterated topological Hochschild homology. It receives a trace map from iterated algebraic K-theory and there is a hope that the rich structure, and the calculability of covering homology will make it useful in the exploration of J. Rognes' “red shift conjecture”.     

Influence of cooperativity on the frequency shift of the Ar–H stretch vibration in HArF complexes

CH₃Li–FArH–X (X?=?H₂, OC, N₂, P₂, CO₂, CO, BeH₂) trimers have been investigated using quantum chemical calculations at the QCISD/6-311++G(2d,2p) level. The results show that the lithium bonding has a prominent effect on the strength and properties of the hydrogen bonding. The hydrogen-bonding interaction energy is increased by 160–340% due to the presence of lithium bonding. The Ar–H stretch vibration shows a blue shift in the FArH–X (X?=?H₂, OC, N₂, CO₂, CO) dimer, but a red shift in the FArH–X (X?=?P₂, BeH₂) dimer. The red shift is increased in the corresponding trimer, while the blue shift shows a different change. The blue shift is also increased in CH₃Li–FArH–X (X?=?H₂, OC, N₂, CO₂) trimers, but it changes to a red shift in the CH₃Li–FArH–CO trimer. The shift change is consistent with the explanation given by Joseph and Jemmis.     

基于NIR高光谱成像技术的长枣虫眼无损检测

为了研究快速识别虫眼枣与正常枣的有效方法,利用特征波长主成分分析法结合波段比算法进行虫眼枣识别。首先,利用NIR高光谱成像系统采集130个长枣(50个正常、80个虫眼枣)图像,提取并分析不同类型长枣特征区域的平均光谱曲线,对970~1 670 nm范围内的光谱数据进行主成分分析,确定7个特征波长(990,1 028,1 109,1 160,1 231,1 285,1 464 nm)。然后,对长枣图像做主成分分析,选择PC2图像进行虫眼识别,虫眼与正常枣的识别率分别为67.5%、100%。为了进一步提高虫眼枣的识别率,采用波段比(R1231/R1109)对未识别的虫眼枣进行再次识别,识别率提高到90%。结果表明,基于NIR高光谱成像技术的检测方法对虫眼枣识别是可行的,同时也为多光谱成像技术应用于在线检测长枣品质提供了理论依据。     

温度对β胡萝卜素结构有序的影响

本文测量了全反式β胡萝卜素在二甲基亚砜中81–25 ℃ 范围的紫外–可见吸收和拉曼光谱. 结果表明, 随温度降低, 紫外–可见吸收光谱、拉曼光谱都发生红移, 拉曼光谱线型变窄, 散射截面增加这些现象的发生是由于随温度降低, β胡萝卜素分子的热无序降低、分子结构有序性增加、π电子离域扩展, 有效共轭长度增加, 分子的电子能隙变窄. 另外, 随着温度的降低, 溶剂密度增加, 由Lorentz-Lorenz 关系得知相伴的折射率增加, 从而引起吸收光谱的红移. CC键键长增加, 使CC 键拉曼光谱红移; 振动弛豫时间变长, 各CC 键之间的键长差减小, 线宽变窄; 但由于声子, π电子耦合加强使CC键拉曼线型不对称程度增加, 低频端"肩"扩展, CC键的弱阻尼相干振动增加, 使拉曼散射截面增加. 关键词： β胡萝卜素 分子结构有序 红移 拉曼散射截面     

Antibacterial cotton fabrics with in situ generated silver and copper bimetallic nanoparticles using red sanders powder extract as reducing agent

Using aqueous extraction of red sanders powder as a reducing agent, silver and copper bimetallic nanoparticles were in situ generated in cotton fabrics. Silver and copper nanoparticles were also generated separately for comparison. The resulted nanocomposite cotton fabrics (NCFs) were characterized by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and antibacterial tests. SEM analysis indicated the generation of more number of nanoparticles when bimetallic source solutions were used. Further, the size range of the generated bimetallic nanoparticles was found to be lower than when individual metal nanoparticles were generated in NCFs. XRD analysis confirmed the in situ generation of silver and copper nanoparticles when equimolar bimetallic salt source solutions were utilized. The NCFs with bimetallic nanoparticles exhibited higher antibacterial activity against both Gram-negative and Gram-positive bacteria and hence can be considered for applications as antibacterial bed and dressing materials.     

Scalable Biosynthesis of the Seaweed Neurochemical,Kainic Acid

Kainic acid, the flagship member of the kainoid family of natural neurochemicals, is a widely used neuropharmacological agent that helped unravel the key role of ionotropic glutamate receptors, including the kainate receptor, in the central nervous system. Worldwide shortages of this seaweed natural product in the year 2000 prompted numerous chemical syntheses, including scalable preparations with as few as six‐steps. Herein we report the discovery and characterization of the concise two‐enzyme biosynthetic pathway to kainic acid from l ‐glutamic acid and dimethylallyl pyrophosphate in red macroalgae and show that the biosynthetic genes are co‐clustered in genomes of Digenea simplex and Palmaria palmata. Moreover, we applied a key biosynthetic α‐ketoglutarate‐dependent dioxygenase enzyme in a biotransformation methodology to efficiently construct kainic acid on the gram scale. This study establishes both the feasibility of mining seaweed genomes for their biotechnological prowess.     

Enhancement of ultrasonically induced cell damage by phthalocyanines in vitro

In this work, erythrocytes from carp were used as a nucleated cell model to test the hypothesis that the phthalocyanines (zinc - ZnPc and chloroaluminium -AlClPc) enhance ultrasonically induced damage in vitro. In order to confirm and complete our earlier investigation, the influence of ultrasound (US) and phthalocyanines (Pcs) on unresearched cellular components, was studied. Red blood cells were exposed to 1 MHz continuous ultrasound wave (0.61 and/or 2.44 W/cm²) in the presence or absence of phthalocyanines (3 μM). To identify target cell damage, we studied hemolysis, membrane fluidity and morphology of erythrocytes. To demonstrate the changes in the fluidity of plasma membrane we used the spectrofluorimetric methods using two fluorescence probes: 1-[4-(trimethylamino)phenyl]-6-phenyl-1,3,5,-hexatriene (TMA-DPH) and 1,6-diphenyl-1,3,5-hexatriene (DPH). The effect of US and Pcs on nucleated erythrocytes morphology was estimated on the basis of microscopic observation.The enhancement of ultrasonically induced membrane damage by both phthalocyanines was observed in case of hemolysis, and membrane surface fluidity, in comparison to ultrasound. The authors also observed changes in the morphology of erythrocytes. The obtained results support the hypothesis that the Pcs enhance ultrasonically induced cell damage in vitro.Furthermore, the influence of ultrasound on phthalocyanines (Pcs) in medium and in cells was tested. The authors observed changes in the phthalocyanines absorption spectra in the medium and the increase in the intensity of phthalocyanines fluorescence in the cells. These data can suggest changes in the structure of phthalocyanines after ultrasound action.     

Luminescence of samarium-activated cubic boron nitride

Under high pressure conditions, we have obtained samples of samarium-activated cubic boron nitride in the form of micropowders, ceramic samples, and polycrystals having high-intensity discrete photoluminescence in the red region of the spectrum that is stable in the temperature range 6 K to 300 K and is assigned to internal f-f electronic transitions in the Sm³⁺ ions. The materials obtained on the basis of cBN are intended for use as phosphors and light emitters (sources of red light) having thermal and chemical stability. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 1, pp. 88–93, January–February, 2008.