基于钙内标的贝壳元素成分微区LIBS分析方法研究

贝类生物作为海洋生态系统监测的理想标识,以Ca为内标进行元素比例变化的分析,将有可能获知气候演化及贝类生长等有用信息。区别于其他技术,微区激光诱导击穿光谱技术(Micro-LIBS：micro-probe laser induced breakdown spectroscopy)应用于贝类贝壳探测时,Ca的特征发射谱线将分布于整个光谱探测区间,如何选择合适谱线作为内标是Ca内标法用于贝壳成分元素分析的关键。以Ca元素为内标进行贝壳成分元素的Micro-LIBS探测,通过归一化Ca元素全谱谱线、最强离子谱线Ca Ⅱ 393.3 nm和不同强度原子谱线(Ca Ⅰ 422.7 nm/Ca Ⅰ 487.9 nm)为内标情况下Sr/Ca元素比例变化的比较,结果发现相较于Ca离子线Ca Ⅱ 393.3 nm和强度较弱原子线Ca Ⅰ 487.9 nm,以Ca元素全谱强度或最强原子线Ca Ⅰ 422.7 nm为内标时,Sr/Ca分布在贝壳分析区域内变化较小,其浮动分别小于7%和10%,符合贝壳分析区域为同一生长周期的纹理特征,较为准确地反映了贝壳的生长发展;同时,应用Ca全谱强度为内标对贝壳成分元素分析发现,元素比例Li/Ca, K/Ca, Na/Ca相较于Mn/Ca,具有明显的相似特征,说明海水富含轻质元素在贝壳生长分布上具有明显的相似性。研究结果表明,较强Ca原子线或全谱强度比Ca离子线更适合作为内标用于贝壳成分元素的微区LIBS分析,证明了Micro-LIBS用于贝壳分析的可行性。     

P掺杂正交相Ca_2Si电子结构及光学性质的第一性原理计算

采用基于密度泛函理论第一性原理超软贋势平面波方法系统计算了Ca2Si及P掺杂Ca2Si的电子结构、光学性质,分析了P掺杂对Ca2Si的能带结构、电子态密度、光学性质的影响.计算结果表明:掺入P后Ca2Si的能带向低能方向偏移,禁带宽带为0.557 95eV,价带主要由Si的3p,P的3p以及Ca的4s、3d电子构成,导带主要由Ca的3d电子贡献.通过能带结构和态密度分析了P掺杂正交相Ca2Si的复介电函数、折射率、反射谱、吸收谱和能量损失函数,结果表明P掺杂增强了Ca2Si的光利用率,说明掺杂能够有效改变材料电子结构和光电性能,为Ca2Si材料光电性能的开发、应用提供理论依据.     

基于体外消化模型的香蕉果肉中可溶态Ca含量分析

在香蕉果肉可溶态Ca含量分析过程中,引入体外消化模型进行预处理,采用AA700型火焰原子吸收分光光度计测量Ca含量。结果表明:(1)八成熟香蕉果肉中Ca含量为1.479 mg.g-1,平行分析实验结果RSD为4.12%;(2)八成熟香蕉果肉经过体外消化模型处理后,可溶态和不溶态Ca含量分别为1.108和0.412 mg.g-1,Ca溶解率和残留率分别为74.9%和27.8%,Ca主要以可溶态形式存在;(3)Ca溶解率和残留率平行实验结果的RSD分别为2.56%和9.10%,说明体外消化模型的引入并没有对实验方法精密度产生显著影响,且溶解率和残留率之和与理论值的误差仅为2.7%,进一步说明在食品微量元素形态分离分析过程中引入体外消化模型可行;(4)Ca测试方法的精密度和回收实验表明,样品回收率为99.2%,RSD为0.11%(n=9)。     

核子-核子碰撞截面对同位素标度参数α的介质效应

核子能量在40-60 MeV能区范围,对在两对重离子中心碰撞系统40Ca 48Ca和60Ca 48Ca以及112Sn 112Sn和124Sn 124Sn的反应中就同位素标度参数a对于核子.核子碰撞截面σmedNN(αm)的介质效应进行了研究.结果发现,核子一核子碰撞介质效应对同位素标度参数n具有明显的影响.就产生这种介质效应的机理进行了分析和讨论.     

紫外-可见分光光度法研究十八胺对钙、镁络合滴定的影响

研究了浮选剂十八胺(ODA)对Ca2+, Mg2+离子络合滴定的影响,主要进行了两组对比实验：(1) 滴定前将十八胺固体不过滤,直接进行滴定分析。结果表明这种情况下,十八胺对Ca2+和Mg2+离子的络合滴定都有较大影响,Mg2+离子的滴定终点难以判断,Ca2+离子的滴定终点虽然可以判断,但与不含十八胺的相应空白溶液相比有明显的分析误差。对相关溶液的紫外-可见分光光度分析进一步确认了该实验结果。(2) 滴定前将十八胺不溶物过滤掉,然后进行滴定分析。结果表明这种情况下,十八胺对Ca2+和Mg2+离子络合滴定的影响可以被基本消除。光谱扫描和时间扫描结果显示,滴定前将十八胺过滤后,对于Ca2+和Mg2+两种离子,溶液最大吸收的位置及溶液吸光度的变化情况都与无十八胺的空白溶液接近。     

基于激光诱导击穿光谱对长白山黑猪肉部位分类

猪肉内部结构成分复杂,各部位的成分相似,分辨较为困难。结合激光诱导击穿光谱技术,通过光谱分析的方式提高分类精度。以5种不同部位的长白山黑猪肉（里脊肉、梅花肉、后腿肉、前腿肉、五花肉）作为待测样品,通过冷藏、切片等预处理方法,探究激光诱导击穿光谱技术鉴别猪肉脂肪与肌肉及其不同部位的可行性。首先通过采集猪肉脂肪样品与肌肉样品的LIBS谱线信息发现,猪肉中Mg,K,Fe,Cu,Ca和Na等元素较为丰富,并在脂肪样品光谱中发现C-N键,与肌肉样品LIBS谱线信息相比,脂肪样品受其内部水分、有机质成分影响致使其谱线信息背景和噪声信号干扰较大,二者谱线信息存在一定差异,说明LIBS可对脂肪组织与肌肉组织进行鉴别。通过对目标元素Ca,Na,Mg,K和Al其LIBS特征谱线强度进行检测,计算Mg/Ca,Al/Ca,Na/Ca和K/Ca比值,发现与Al/Ca和Mg/Ca相比,Na/Ca和K/Ca各部位元素比值分布差异明显,在此基础上,根据Na/Ca和K/Ca比值,计算猪肉各部位元素分布决策阈值[（1-α）=90%]。发现与Al/Ca和Mg/Ca比值相比,Na/Ca和K/Ca更能明显的反应出各部位元素分布的不同。其比值分布阈值基本可对猪肉各部位进行区分。以前腿肉与后腿肉为例,前腿肉Na/Ca和K/Ca比值分别分布在1.29～1.58和0.31～0.42,后腿肉Na/Ca和K/Ca比值分别分布在0.98～1.18和0.15～0.23。其元素比值分布无明显重叠。最后,为提高LIBS技术对猪肉不同组织分类的可靠性,将光谱元素强度比值数据与主成分分析法相结合,基本可以实现对猪肉各部位的分类,说明元素特征谱线强度比值在对猪肉各部位分类时具有一定的预测精度。该工作证明,使用激光诱导击穿光谱技术对猪肉进行分类识别等定性分析时具有一定可行性,有望适用于其他生物组织检测分析。     

水溶液中Ca(OH)2粒径分布研究

本文利用激光粒度分析仪研究了石灰产地、石灰尺寸和液固质量百分比对石灰水合所得浆液中Ca(OH)2粒径的影响.结果显示,石灰尺寸和液固质量百分比对浆液中Ca(OH)2粒径分布影响较小,而产地对粒径有一定影响.将平均粒径为5μm的分析纯Ca(OH)2粉末制备成浆液,其粒径增大到13μm,表明Ca(OH)2在水中发生团聚.因此,单纯依靠改变制备条件或石灰来源,对于减小Ca(OH)2的粒径作用不大,必须采用其它措施如添加分散剂来减轻团聚并减小粒径.     

纳米粉末Ba_(0.2)Ca_(0.8)TiO_3∶Pr的合成及XRD研究

文章采用溶胶-凝胶法合成Ba0.2Ca0.8TiO3Pr纳米粉体,分析了溶胶-凝胶法合成稀土发光材料Ba0.2Ca0.8TiO3Pr的反应原理,应用X射线衍射进行结构表征,分析了不同温度下Ba0.2Ca0.8TiO3:Pr的粒径大小以及结构变化。     

速效救心丸中Ca,Mg,Fe,Cu,Zn的测定及Ca/Mg,Cu/Zn比值分析

本文采用火焰原子吸收分光光度法测定了速效救心丸中Ca ,Mg ,Fe,Cu ,Zn五种金属元素的含量 ,并对速效救心丸中Ca/Mg ,Cu/Zn含量比值进行了分析研究。结果表明 ,速效救心丸中含有丰富的Ca,Mg ,Fe ,Cu ,Zn元素 ,元素含量Ca>Fe >Mg >Zn >Cu ,它为探讨速效救心丸中Ca ,Mg ,Fe ,Cu ,Zn与治疗冠心病之间的关系提供了有用的数据。     

单色光激发的轻元素X射线分析

利用同步辐射单色光和质子激发的X射线作为可选择能量的单色光源,对K､Ca.Ti轻元素进行X荧光分析.实验结果表明,它不仅可以降低轫致辐射本底,还可用通过选择合适的激发能量排除某些元素的干扰,从而使K、Ca、Di元素分析灵敏度得到明显的提高.     

Insight into the calcium carboxylate release behavior during Zhundong coal pyrolysis and combustion

In this paper, the dynamic behavior of calcium carboxylate release during Zhundong coal pyrolysis and combustion is studied via reactive molecular dynamics (ReaxFF MD) simulation. The molecular structure model of Zhundong coal is constructed based on the combination of the classic Hatcher coal model and experimental characterizations. Pyrolysis simulations on the coal model are performed at different temperatures ranging from 2000 K to 2800 K. The pyrolysis experiments are also carried out to validate the ReaxFF simulation. The results show that most of the calcium are released into the volatiles by the thermal decomposition of CM-Ca (coal/char matrix with calcium bonded) after releasing CO₂. The distributions of the calcium bonded to gas, tar and inorganics as well as the atomic calcium in the volatiles are quantitatively classified. The thermal cracking of tar fragments are significant at high temperatures leading to the conversion of calcium from tar into the organic gas. Furthermore, the nascent char model is constructed to study the release behavior of calcium in char combustion stage. The calcium is initially released in the form of oxidized calcium and atomic calcium. With increasing temperature, the oxidized calcium trends to convert to the organically bonded calcium. By using the Arrhenius expression, the kinetic parameters for the release of calcium into various species during pyrolysis and char combustion stages are quantitatively determined.     

X射线荧光光谱法快速分析苹果酸·柠檬酸钙中的总钙

文章以粉末压片法制样,顺序式单道X射线荧光光谱仪测定苹果酸·柠檬酸钙中的总钙, 方法快速准确简捷,完成一个样品制备和分析只需10 min;文章还进行了火焰原子吸收光谱法的对比试验, 阐述了两法各自的特点。     

Coherent calcium puff signals driven by intracellular noises

In many cell types, intracellular calcium is released from internal stores through calcium release channels which are distributed in clusters with a few tens of channels. Localized calcium release events, i.e. Ca^{2 +} puffs, are subjected to stochastic channel dynamics and fluctuations of environmental calcium. Driven by the internal channel noise or external calcium noise, the localized calcium puffs show a coherence resonance phenomenon at weak stimulus. Our study indicates that coherent calcium puffs with an enhanced periodicity can be achieved with external calcium noise more easily than with internal channel noise.     

Finding of Optimal Calcium Ion Probes for Fluorescence Lifetime Measurement

We have investigated the fluorescence lifetime properties of 8 calcium ion probes, calcium-green-1, calcium green-2, calcium green-5N, calcium orange, oregon green 488 BAPTA-6F, fluo-3, fluo-4, and fluo-5N. We found that the decay time of calcium green-5N varied more sensitively with calcium concentration than calcium green-1 which was known to be a highly sensitive probe. We have also found that the center of observable range of calcium concentration by fluorescence lifetime measurement is lower than that by fluorescence intensity measurement.     

Chemisorption of oxygen to gold: AES study of catalytic effect of calcium

Surface-segregating calcium impurity is removed from a polycrystalline gold sample by heating, exposing to oxygen, and ion-bombarding over an extended period of time. The rate of oxygen chemisorption is found to decrease drastically from that at the beginning of the purification period where calcium segregation is substantial to that at the end where segregated calcium is nearly undetectable. The effect of calcium appears to involve dissociative chemisorption of molecular oxygen at the calcium sites followed by migration of oxygen atoms to gold sites, in a manner analogous to “hydrogen spillover” occurring on the surface of supported catalysts. It is also found that oxygen previously chemisorbed to a gold surface can promote the surface segregation of calcium even in the absence of gas-phase oxygen. Equations are presented to account for simultaneous catalysis of oxygen chemisorption to gold by calcium, and promotion of calcium surface-segregation by oxygen chemisorbed to gold.     

Calcium imaging using fluorescence lifetimes and long-wavelength probes

We describe imaging of calcium concentrations using the long-wavelength Ca²⁺ indicators, Calcium Green, Orange, and Crimson. The lifetimes of these probes were measured using the frequency-domain method and were found to increase from 50% to severalfold in response to calcium. The two-dimensional images of the calcium concentration were obtained using a new apparatus for fluorescence lifetime imaging (FLIM). We also describe procedures to correct for the position-dependent frequency response of the gain-modulated image intensifier used in the FLIM apparatus. Importantly, the FLIM method does not require the probe to display shifts in the excitation or emission spectra. Using the FLIM method, calcium imaging is possible using probes which display changes in lifetime in response to calcium. Consequently, calcium imaging is possible with excitation wavelengths ranging from 488 to as long as 620 nm, where autofluorescence and/or photochemical damage is minimal. These probes are also suitable for calcium measurements of single cells using lifetime-based flow cytometry.     

基于红外光谱分析研究矿化剂对铝酸钙粉制备的影响

研究了矿化剂对中低品位铝矾土对所制备铝酸钙粉的结构及其光谱性能的影响。以中低品位铝钒土和碳酸钙为主要原料,矿化剂CaF₂为添加剂,三者经充分混合、 高温煅烧和粉磨后,生产出的铝酸钙粉可直接用于制备聚合氯化铝、 聚合硫酸铝、 铝酸钠等水处理剂。通过调整原料中铝矾土和碳酸钙的质量比和矿化剂CaF₂投加量的方法优化铝酸钙粉的制备工艺,采用红外光谱分析对铝酸钙粉和铝矾土进行表征,并对矿化剂的矿化机理进行研究。红外光谱分析结果表明：加入矿化剂CaF₂,可促进铝矾土中硬水铝石、 三水铝石和高岭石的分解转化,使碳酸钙的分解完全,使原料中的铝矾土与碳酸钙进行更加充分的反应,不仅有助于碳酸钙中的Ca与铝矾土中的Si结合,还有助于促进铝矾土中的Si—O,Si—O—Al及Al—Si键的断裂,使铝矾土中的Al充分溶出,从而提高Al₂O₃的溶出率;矿化剂CaF₂的投加量(质量比)为3%时,可有效促进Al₂O₃的溶出;矿化剂CaF₂的投加量为1.5%时,不足以起到充分的矿化作用;中低品位铝矾土较高品位铝矾土更易于烧结制备铝酸钙粉;在1 250 ℃下制备铝酸钙粉的最佳物料配比是：原料中铝矾土与碳酸钙的质量比为1∶0.6,矿化剂CaF₂的投加量为3%。     

Effect of calcium ions on the irradiation induced inactivation of cellulase

Abstract The activity of cellulase irradiated at various temperatures was examined as a function of irradiation dose. The effect of calcium ions in radiation inactivation of cellulase at irradiation temperature of 30°C was studied by using calcium sulfate. The calcium ions have a protective ability against radiation caused inactivation of cellulase by scavenging species such as OH(-) formed by irradiation of cellulase aqueous solution, in which the effective concentration range of the calcium ions was ～ 10(-3) M. The calcium ions do not act for the heat inactivation of the enzyme and the enzyme hydrolysis of filter paper or chaff as an activator because the calcium ions do not associate with the enzyme to form a calcium ion-enzyme complex.     

Optimal intracellular calcium signaling

In many cell types, calcium is released from internal stores through calcium release channels upon external stimulation (e.g., pressure or receptor binding). These channels are clustered with a typical cluster size of about 20 channels, generating stochastic calcium puffs. We find that the clustering of the release channels in small clusters increases the sensitivity of the calcium response, allowing for coherent calcium responses at signals to which homogeneously distributed channels would not respond.     

人体胆结石红外光谱的比较分析

用红外光谱法测量了系列胆结石成分的红外光谱。比较标准化合物的红外光谱,分析人体胆结石的成分。按胆结石的红外光谱特征进行分类,获得胆固醇、胆红素钙、硬酯酸钙、碳酸钙、羟基碳酸磷灰石和混合物等六种类型的光谱图。提出相应地将胆结石分为六种类型：如果根据是否含钙,则分为胆固醇和钙盐型两种类型。