Palladium dichloride whiskers: preparation and properties

Palladium dichloride whiskers can be prepared by reacting palladium with chlorine at temperatures above 500 degrees C. The crystals measure 1 x 100 micrometers and are strong (5 percent elastic deformation). They may be a morphological form of one of the high-temperature polymorphs of PdCl(2).     

Paramagnetic unit in spinach subchloroplast particles: estimation of size

A pulsed ruby laser (wavelength, 694.3 nanometers) was used to measure the dependence on light intensity of light-induced electron paramagnetic resonance (ERR) signal 1 for short flashes of uniform duration (400 microseconds). Approximately 10(18) photons per square centimeter per flash from the unattenuated beam were available to the sample of subchloroplast "system 1" particles from spinach. The experimental dependence of the EPR signal height plotted as a function of the total number of incident photons per flash was exponential. From measurement of the slope at a very low relative photon flux and the saturated EPR signal amplitude, the value for the cross section or "effective size" of the light-induced paramagnetic unit, sigma(EPR), was found to be 300 x 10(-17) square centimeter. This result is compared with a measured optical absorption cross section, sigma(694nm), of 2.5 x 10(-17) square centimeter, for the identical sample at the laser wavelength. The hundredfold difference in size supports the thesis that the paramagnetic state is a property of an aggregate of chlorophyll molecules of the same general size as the photosynthetic unit.     

Sulfates as pollution particulates: catalytic formation on carbon (soot) particles

Experimental evidence (obtained by electron spectroscopy for chemical analysis) is presented which shows that finely divided carbon (soot) particles may play a major role in the catalytic oxidation of sulfur dioxide to sulfate in polluted atmospheres. The results obtained with sulfates produced in the laboratory by the oxidation of sulfur dioxide on graphite particles and combustion-produced soot particles are compared with the properties and behavior of ambient sulfates. The proposed sulfur dioxide oxidation mechanism is qualitatively consistent with field observations.     

Shape identification and particles size distribution from basic shape parameters using ImageJ

Quick and accurate particle size distribution analysis is desirable in various technical fields that handle granular or particulate materials including size reduction. We developed an ImageJ plugin that extracts the dimensions from a digital image of disjoint particles after identifying their shapes and determines their particles size distribution. We established that the major and minor axes of ImageJ fitted ellipse along with the developed correction factors efficiently determined dimensions of particles. This paper describes the plugin development and its application to food grains and ground biomass. Using computer generated geometrical shapes as reference objects, a shape identification strategy that addresses common geometric shapes such as square, inclined square, rectangle, inclined rectangle, circle, ellipse, and inclined ellipse was developed. The strategy used only three newly defined shape parameters to identify objects, such as reciprocal aspect ratio, rectangularity, and feret major axis ratio from the standard outputs generated by ImageJ. Evaluation of effects of the particles shape, size, and orientation on the deviation from the reference particle's length and width indicated that the mean absolute deviations of all these factors were less than 1.3%. Developed plugin was applied successfully to analyze the dimensions and size distribution of food grains and ground Miscanthus particles images. The plugin produced quick and accurate size distribution of particles from digital images and can be applied to variety of particle analysis applications.     

The design and catalytic properties of a simplified ribonuclease P RNA

Ribonuclease P (RNase P) RNA is the catalytic moiety of the ribonucleoprotein enzyme that removes precursor sequences from the 5' ends of pre-transfer RNAs in eubacteria. Phylogenetic variation according to recently proposed secondary structure models was used to identify structural elements of the RNase P RNA that are dispensable for catalysis. A simplified RNase P RNA that consists only of evolutionarily conserved features was designed, synthesized, and characterized. Although the simplified RNA (Min 1 RNA) is only 263 nucleotides in length, in contrast to the 354 to 417 nucleotides of naturally occurring RNase P RNAs, its specificity of pre-tRNA cleavage is identical to that of the native enzymes. Moreover, the catalytic efficiencies of the Min 1 RNA and the native RNA enzymes are similar. These results focus the search for the catalytic elements of RNase P RNAs to their conserved structure.     

硅铝交联膨润土的制备及性能研究

将硅溶胶与钙基膨润土进行羟基硅与羟基铝交联反应制备硅铝交联膨润土。探讨酸度、温度、时间及膨润土与硅酸钠配比对交联土吸附性能的影响。实验表明:膨润土与硅酸钠按10∶1的配比,在40℃、pH=9的条件下搅拌交联2h制得的交联土对阳离子性能最佳。     

基于抗菌活性的氧化锌粒子的制备及其性能研究

为制备具有抗菌活性的氧化锌粒子,以硝酸锌和氢氧化钠为原料,采取水热法制备得到纳米氧化锌,并研究其抗菌性能.采用粒度分析、红外光谱分析、扫描电镜分析和热重分析手段,系统研究了pH、反应温度、反应时间、氢氧化钠浓度对纳米氧化锌粒径的影响,获得了制备纳米氧化锌的最佳条件.研究结果表明,当氢氧化钠浓度为0.2 mol/L、pH...     

肉桂酰辅酶A还原酶(CCR)的底物制备及酶学特性研究

采用原核表达体系和HPLC法,分别获得肉桂酰辅酶A还原酶(CCR)及其反应底物———香豆酰CoA酯,并对CCR酶学特性进行研究分析。结果表明,通过酶学方法和HPLC的分离纯化能够得到较高浓度和纯度的CCR反应底物;重组毛白杨CCR的最适反应温度是37℃,最适pH值为6.25,Km值为5.664μmol/L,Vmax为4.09 nmol/Ls。     

柳橙皮基可降解膜的制备及其性能研究

为探索新型可降解膜材料的制备方法及其性能,以柳橙皮为成膜基材,海藻酸钠和羧甲基纤维素钠为增稠剂,甘油为增塑剂,采用流延法制备柳橙皮膜,并探究了柳橙皮浓度、增稠剂浓度、增塑剂浓度对膜力学性能和阻隔性能的影响。结果表明:柳橙皮浓度为1.5%,海藻酸钠浓度为0.1%,羧甲基纤维素钠浓度为0.2%,甘油浓度为0.2%,此时膜的综合性能最佳。其主要指标:抗拉强度为24.08 MPa,断裂伸长率为15.73%,水蒸气透过系数为1.686×10~(-12)g·cm·cm~(-2)·s~(-1)·Pa~(-1)。研究表明,柳橙皮成膜性较好,且具有良好的力学性能和阻隔性能,是一种具有开发潜力的新型包装材料。     

结构用竹木复合层积材的制备及其力学性能评价

利用竹木复合的方法来提高杨木单板层积材的力学性能,从而使其满足结构用单板层积材的等级要求。分别利用竹束单板和竹席单板与杨木单板浸胶复合制成竹木复合层积材,并测试其力学性能以及单板间的胶合性能。研究表明,竹束杨木复合和竹席杨木复合的层积材强度等级均大大超过杨木单板层积材,分别可达140E优等品、110E优等品。     

醚化海藻酸钠改性吸水树脂的制备和性能研究

对海藻酸钠进行醚化改性，以提高其相容性和化学稳定性，同时采用水溶液聚合法，选择丙烯酸（从）与丙烯酰胺（AM）单体与醚化海藻酸钠（ESA）通过共混、交联方式制备了高吸水材料，对其溶胀性能和热稳定性进行了研究．结果表明，当ESA、AM占总单体质量的20％和10％，交联剂、引发剂占总单体质量的0．6％和0．2％时，ESA-Co-AA-Co-AM吸去离子水倍率最高达411g／g，吸盐水倍率均在65g／g左右．TG-DTG试验表明ESA．Co-AA-Co-AM的起始分解温度在200℃左右．     

含超粒径非均质混合土最大干密度的计算方法

根据含超粒径非均质混合土压实的试验结果,分析了非均质混合土的压实规律,总结出考虑颗粒级配确定非均质混合土最大干密度的拟合公式。所给公式模型清晰,概念明确,可供参考。     

两种方法制备2,5-二苯乙炔基噻吩微胶囊及其性能表征

采用界面聚合法和原位聚合法制备2,5-二苯乙炔基噻吩微胶囊,以解决其无效光降解的问题,探索两种不同的制备方法对微胶囊形貌及其大小的影响,并对微胶囊的红外光谱也进行了研究.结果表明,原位聚合法中,囊壁采用一定量的甲醛和三聚氰胺交联物作囊材,在特定的pH值下可反应得到;界面聚合法中,对二乙烯三胺和异佛尔酮二异氰酸酯(IPDI)三聚体这两种囊材的用量和pH值没有严格的要求.从两种方法的制备过程和结果可以看出,界面聚合法不仅方便快速而且效果好,是理想的制备微胶囊的方法.     

脱蛋白工艺对脱蛋白天然橡胶性能的影响

胶乳蛋白分为结合蛋白和水溶性蛋白,而天然橡胶过敏原主要来自水溶性蛋白。吸附沉淀法和酶解法针对不同类型的蛋白质产生作用。以不同脱蛋白方式得到的脱蛋白橡胶为研究对象,研究不同的蛋白去除方式对天然橡胶的外观特性、门尼粘度、硫化特性、力学性能等影响。结果表明,酶解法水解脱蛋白工艺能有效降低总蛋白质含量,而吸附沉淀法脱蛋白工艺能有效去除水溶性蛋白质,同时兼顾其他非胶物质的纯化,达到降低蛋白水平降低过敏性与纯化橡胶的双重目的。在性能保持方面,吸附沉淀法优于酶法脱蛋白。     

乌鲁木齐市土壤磁学特征及其与粒度的关系

【目的】分析乌鲁木齐市市区、郊区表层土壤磁性和粒径分布特征的差异性,揭示土壤粒度与矿物磁性特征的关系,测试土壤磁性参数作为粒径代用指标的可行性,为未来运用磁学方法监测城市土壤污染提供参考。【方法】采集乌鲁木齐市市区建设用地及郊区农用地和未利用地表层(0~10cm)土壤样品45个,采用磁测和激光衍射粒度仪测量土壤磁性参数和粒度,利用Pearson相关性分析和GIS技术计算磁性参数低频质量磁化率(χLF)、高频质量磁化率(χHF)、百分频率磁化率(χFD)、硬剩磁(HIRM)、软剩磁(SOFTIRM)和饱和等温剩磁(SIRM)与粒径含量的相关系数,并绘制空间分布图。【结果】除χFD外,市区建设用地土壤磁性参数均值均高于郊区农用地和未利用地,多畴粗颗粒亚铁磁性矿物主导了土壤样品的磁学性质;市区表土黏土含量低于郊区,粉砂、砂粒含量略高于郊区;研究区土壤粒度组成以粉砂为主,其次为黏土和砂;通过比较市区表土磁性参数与不同粒径含量间的相关系数绝对值发现,χLF与2~8μm粒级,HIRM与8~16μm、63μm粒级,χFD与16~32μm、32~63μm粒级含量的相关性最强。郊区农用地、未利用地土样的磁性参数与粒级含量无显著相关性;黏土和极细粉砂含量与χLF和SOFTIRM、SIRM、HIRM在西部、东北、中部和南部区域空间上存在正相关,与χFD的相关区域位于市区中部。细粉砂与SIRM和HIRM在西北部、东北部以及东南部存在正相关,与χFD在空间上分布一致性较少。中粉砂、粗粉砂和砂含量与χFD在西部、东北部和中部偏西南区域存在正相关。【结论】乌鲁木齐市市区、郊区表土磁性和粒径分布特征不同。市区建设用地表土的χLF、HIRM和χFD分别可作为2~8μm粒级、细粉砂和砂粒级、中粉砂和粗粉砂含量的代用指标。在圈定的西部、东北、中部、南部、西北、东北、东南和西南区域,χLF、HIRM和χFD能更准确地反映粒级含量的高低。     

石榴皮粉粒径对其理化及抗氧化特性的影响

【目的】研究石榴皮粒径对其理化及抗氧化特性的影响,为后续石榴皮粉功能食品的开发和工业化生产提供理论基础。【方法】制备不同粒径(150μm,≥150μm～280μm,≥280μm～450μm,≥450μm～850μm)的石榴皮粉,测定其基础理化指标、持水性、持油性、密度、流动性、色泽以及总黄酮、总酚含量,并以DPPH、ABTS自由基清除能力和总还原能力为指标对其抗氧化活性进行综合评价,最后结合场发射扫描电子显微镜(SEM)对石榴皮粉表面特征进行分析。【结果】当粒径从≥450μm～850μm降低到150μm时,石榴皮粉的色泽逐渐变深,其黄度值从46.84增加到60.84,而白度值从85.03降低到79.46;石榴皮粉的松装密度、振实密度均显著降低,其松装密度从645.32 kg/m~3降至329.01 kg/m~3,振实密度从673.33 kg/m~3降低至493.33 kg/m~3,且流动性变差;石榴皮粉的持水性从4.89 g/g降低到2.28 g/g,而持油性从1.48 g/g增至1.70 g/g。随着粒径的减小石榴皮粉的总黄酮、总酚含量增加,自由基清除能力以及总还原力增强。SEM分析表明,破碎可以影响石榴皮粉末的微观结构以及表面特征。【结论】石榴皮粉的粒径可以显著影响其理化及抗氧化特性,粒径280μm的石榴皮粉具有更佳的理化性质以及更高的总酚、总黄酮含量和更强的抗氧化活性,可以用作食品加工中的功能改善剂和抗氧化剂。     

长白猪体尺性状与繁殖性状的典型相关分析

对长白母猪的7个体尺性状和5个繁殖性状进行了典型相关分析.结果表明,体尺性状与繁殖性状间的第1和第2典型相关系数均达极显著水平(P<0.01),其典型相关系数分别为0.913和0.881,占总相关信息的91.2%.分析还表明:母猪的体尺性状与繁殖性状存在相关关系;母猪的体重、腹围、乳头数和体高对产活仔数、初生个体重和断奶个体重起主要作用,对母猪的早期选择应侧重于这几个性状的表现.     

不同粒度的砂土对HT200磨损性能的试验研究

在磨料磨损试验机上,考察了不同粒度的土壤对灰铸铁HT200磨损性能的影响,用扫描电子显微镜观察HT200试样磨痕表面的形貌,分析磨痕形成机理.结果表明:随着土壤粒度的增大,HT200材料磨损量随之增大;显微观察发现HT200磨损表面形成隆起与凹谷,还有少量沟槽;土壤对HT200的磨损主要是脆化剥落形成的,塑性变形较轻.     

Methyl radicals: preparation and stabilization

Methyl radicals were prepared by photolysis of methyl iodide in porous glass and were stabilized for days at room temperature. Their reactivity was investigated.