Synthesis and Structure of Novel Double Flexible Spacer Bridged Biscalix[4]arenes

25, 25′, 27, 27′‐Bis(1,3‐dioxypropane)‐bis(5, 11, 17, 23‐tetra‐tert‐butylcalix[4]arene‐26,28‐diol) (4) and 25, 25′, 27, 27′‐bis(1, 4‐dioxybutane)‐bis (5, 11, 17, 23‐tetra‐tert‐butylcalix‐[4]arene‐26, 28‐diol) (5) were synthesized by the reaction of p‐tert‐butylcalix[4]arene (1) with preorganized 25, 27‐bis(3‐bromoproxyl)calix[4]arene‐26, 27‐diol (2) and 25, 27‐bis(3‐bromobutoxyl)calix[4]arene‐26, 27‐diol (3) in the presence of K₂CO₃ and KI. Compounds 4 and 5 were characterized with X‐ray analysis and the selectivity of 4 and 5 toward K⁺ over other alkali metal ions, alkaline metal ions as well as NH₄⁺ were investigated with an ion‐selective electrode.     

磁场对铁氰化钾与抗坏血酸反应速率的影响

科学实验表明,磁场能改变水系及非水体系的许多物理化学性质,这不仅导致越来越多的科学的工作者对相关的理论问题进行了广泛和深入的研究^[1-4],而且还产生了一系列磁应用技术。从60年代至今,磁场及磁处理技术已在工业、农业、石油开采、混凝土、生物等领域得到了广泛应用^[5-8]。因磁场能改变水及水系的物理化学性质,如果对水系中进行的同一反应,磁场能改变其溶剂效应,则必然引进化学反应速率的改变。基于这种思想,前文^[9,10]曾采用磁处理反应液及磁场直接作用反应体系的方法对水溶液中进行的乙酸乙酯皂化反应体系的方法对水溶液中进行的乙酸乙酯皂化反应的速率常数进行了研究。结果表明,在最佳磁处理和最佳磁场条件下,该反应的速率常数都明显增大。铁氰化钾被抗坏血酸还原也是一个在水溶液中进行的而且其机理研究也较为成熟的反应。本文将采用磁场直接作用于反应体系的方法,研究不同的磁场条件对该反应速率常数的影响。     

钾原子4S-6S双光子共振的实验研究

利用YAG激光抽运的染料激光器将钾原子由基态 4S双光子共振激发到 6S态 ,研究了钾原子 4S 6S双光子共振三光子电离的电离谱与温度、激光强度的关系 ,发现电离流的强度随着温度的升高而增强 ,当温度在 370℃附近时达到最大值 ,此时温度继续升高电离流强度减弱。在温度不变的情况下 ,电离流强度随着激光能量的增强而增强 ,当激光强度为 4 5× 10 5W /mm2 时到达最大值 ,继续增加激光强度 ,电离流强度趋于饱和。实验中观测到对应于 6S 4P的自发辐射     

高锰酸钾-甲醛化学发光体系测定甲氧氯普胺

基于在甲醛的作用下,高锰酸钾对甲氧氯普胺的氧化作用而产生化学发光的现象,建立了一种新的用流动注射-化学发光法测定甲氧氯普胺含量的方法.该方法测定甲氧氯普胺的线性范围为0.2~100 mg/L,检出限为0.1 mg/L.对于8 mg/L的甲氧氯普胺标准溶液连续11次测定的相对偏差为1.2%.该方法可用于对制药废水、片剂和针剂中甲氧氯普胺含量的测定.     

A study of primary nucleation of calcium oxalate monohydrate: II. Effect of urinary species

Kidney stones consist of various organic and inorganic compounds. Calcium oxalate monohydrate (COM) is the main inorganic constituent of kidney stones. However, the mechanisms for the formation of calcium oxalate kidney stones are not well understood. In this regard, there are several hypotheses including nucleation, crystal growth and/or aggregation of formed COM crystals. The effect of some urinary species such as oxalate, calcium, citrate, and protein on nucleation and crystallization characteristics of COM is determined by measuring the weight of formed crystals and their size distributions under different chemical conditions, which simulate the urinary environment. Statistical experimental designs are used to determine the interaction effects among various factors. The data clearly show that oxalate and calcium promote nucleation and crystallization of COM. This is attributed to formation of a thermodynamically stable calcium oxalate monohydrate resulting from supersaturation. Citrate, however, inhibits nucleation and further crystal growth. These results are explained on the basis of the high affinity of citrate to combine with calcium to form soluble calcium citrate complexes. Thus, citrate competes with oxalate ion for binding to calcium cations. These conditions decrease the amount of free calcium ions available to form calcium oxalate crystals. In case of protein (mucin), however, the results suggest that no significant effect could be measured of mucin on nucleation and crystal growth. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Influence of crystallization conditions on the mechanism and rate of crystal growth of potassium sulphate

Growth rate of potassium sulfate crystals was studied in a fluidized bed crystallizer. Higher growth rates were observed at larger bed heights. Larger crystals grow faster than smaller size crystals due to the changed fluid dynamics. The growth rate was found to be very sensitive to the pH value of the solution. The growth rate increases with increasing the pH value and the increase of growth in the acidic medium is faster than in the basic medium. The presence of small amounts of Cr³⁺ ions reduces the growth rate of potassium sulfate dramatically. The presence of Cr³⁺ ions lowers the saturation temperature and increases the width of the metastable zone, i.e. shifts the metastability of the solution to be at lower level of supersaturation.     

Czochralski growth and constitutional studies on single crystals of potassium lithium niobate (KLN)

The ferroelectric phase of potassium lithium niobate K₃Li_2−xNb_5+xO₁₅ (KLN) is a very promising material for the conversion of infrared light to light in the visible region. However, growing of single crystals is known to be complicated due to the considerable anisotropy of the growth rate and the thermal expansion behaviour. The single crystals of KLN, Mg²⁺‐doped KLN, as well as the mixed crystals of potassium lithium tantalate niobate K₃Li₂(Nb_1−xTa_x)₅O₁₅ (KLTN) were grown by the Czochralski technique. The chemical analyses of the samples were performed by atomic absorption spectroscopy (AAS) and X‐ray fluorescence analysis (XRF). The element concentrations along the single crystals were measured by the electron microprobe analysis (EMPA) to clarify the segregation phenomena in the grown crystals. The elements distribution coefficients were also calculated. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

总氮测定过程中空白吸光值偏高的原因分析

使用HJ 636-2012测定水质总氮时,空白吸光值往往偏高。为了寻找最佳的实验条件,使用多元线性回归模型定性评价过硫酸钾和氢氧化钠的纯度、实验用水、碱性过硫酸钾溶液的存放时间、消解条件、冷却时间、消解器皿等因素对空白吸光值的重要性。结果表明:过硫酸钾纯度对空白吸光值影响最显著。为了保证总氮空白吸光值小于0.030,测定总氮时应优先使用经过2~3次重结晶的过硫酸钾以及优级纯的氢氧化钠,碱性过硫酸钾溶液应现配现用;建议消解时间30 min,消解温度123℃,自然冷却时间1.5 h;实验应优先使用超纯水或无氨水;使用哈希消解管代替25 mL比色管。     

酸性氯酸钾处理-水浴加热全自动凯氏定氮仪测定土壤矿物中的固定态铵

固定态铵作为一种重要的潜在氮源,准确测定其含量,对于认识土壤肥力的形成机理、生态系统氮循环和保障国家粮食安全具有十分重要的意义。固定态铵最常用的方法是Silva-Bremner法,但该方法试剂配制要求严苛,前处理过程操作繁琐、费时。为了实现快速、准确、安全地测定土壤固定态铵的含量,对前处理过程进行了研究,用酸性氯酸钾溶液处理土壤样品,用水浴代替震荡,并与Silva-Bremner法的结果进行了对比。试验了自动凯氏定氮仪工作参数、酸性氯酸钾的浓度和用量、水浴加热的温度和时间,确定了测定土壤固定态铵的最佳条件。结果表明,称取1克样品加入20毫升氯酸钾-盐酸混合溶液（3％-10％）预处理,用0.5mol/L氯化钾溶液交换、洗涤,残渣加入加5mL氢氟酸-盐酸溶液（5mol/L-1mol/L）,在沸水浴加热1.5-2h,用自动凯氏定氮仪蒸馏滴定。对5种类型土壤固定态铵7次测定的结果进行了数据分析,相对标准偏差（RSD）均小于3.87%,最大G值1.49,最大F检验值4.12,最大t检验值0.72,均小于临界值,两种方法测定结果无显著差异。该方法的操作安全性和分析效率得到大幅提高,方法的精密度、准确度满足要求。     

Nutraceutical Content and Genetic Diversity Share a Common Pattern in New Pomegranate Genotypes

The nutraceutical value of pomegranate in the treatment of many diseases is well-documented and is linked to its richness in phenolic compounds. This study aims to evaluate the nutraceutical and genetic diversity of novel pomegranate genotypes (G1–G5) in comparison to leading commercial pomegranate varieties, i.e., ‘Wonderful’, ‘Primosole’, ‘Dente di Cavallo’ and ‘Valenciana’. Morphometric measurements were carried out on fruits, accompanied by chemical characterization (total phenolic content, antioxidant activity, carbohydrates and minerals) and the development of four new polymorphic SSR markers involved in the flavonoid pathway. The cultivars displayed a marked variability in the weight and shape of the fruits, as well as in the weight of the arils and juice yield. The highest level of total phenolic content and antioxidant activity was found in ‘Wonderful’ and G4, while the lowest was in ‘Dente di Cavallo’. Furthermore, the results showed that pomegranate juice is an excellent source of minerals, especially potassium, which plays a key role in organ functioning. The new flavonoid-related markers effectively differentiated the cultivars with the same diversity pattern as morpho-chemical characterization, so the SSRs developed in the present study can be used as a rapid tool for the identification of pomegranate cultivars with relevant nutraceutical traits, such as the new genotypes investigated.