NAK-12树脂脱除蚕蛹复合氨基酸异味及褐变物质的研究

本文研究了用NAK－12吸附树脂脱除蚕蛹复合氨基酸异味及褐变色素的条件，初步分析了蚕蛹复合氨基酸异味产生的原因，实验结果表明：当流速为3BV／h时，1ml NAK-12吸附树脂能吸附1．75g蚕蛹复合氨基酸中的异味物质；能吸附1．45g蚕蛹复合氨基酸中的褐变物质。甲醇是异味物质和褐变物质的良好洗脱剂，用pH1．0的甲醇以1BV／h流速洗脱，仅用3．5BV的洗脱剂即可完全洗脱异味物质和褐变物质，蚕蛹复合氨基酸异味产生的可能机理是：加热蚕蛹复合氨基酸液时，其苯丙氨酸，蛋氨酸，蛋氨酸，异亮氨酸，亮氨酸，苏氨酸被氧化脱氨，生成挥发性醛，而其褐变则是赖氨酸，精氨酸与还原糖发生Maillard反应生成褐变物质引起的。     

云南青铜防腐显微拉曼光谱和EPMA研究

应用显微激光拉曼光谱和EPMA(电子探针技术),对云南的四件青铜器(两件春秋时期的青铜矛和两面元代的青铜镜)的腐蚀情形和防腐技术进行了分析研究。拉曼实验结果表明,云南青铜器表面腐蚀产物的主要成分有Cu2O和CuCO3.Cu(OH)2。利用电子探针技术,确定了青铜器内部和表面的元素成分。本文初步分析了云南四件青铜器防腐技术的应用和发展,春秋战国时期,人们在青铜矛表面涂上一层锡的氧化物涂层以防腐蚀;元代的人则采用合金表面处理技术防腐。事实证明,锡的氧化物涂层的防腐效果最好。对金属文物的研究,显微激光拉曼光谱是一种原位无损检测的有效方法,但还是有某些局限性,若配合以电子探针等测试方法,可以达到更好的效果。     

Microstructure evolution and dielectric properties of Ba<Subscript>5-x</Subscript>Na<Subscript>2x</Subscript>Nb<Subscript>10</Subscript>O<Subscript>30</Subscript> ceramics with different Ba–Na Ratios

The tetragonal tungsten bronzes of Ba5−xNa_2x Nb₁₀O₃₀ (BNN, 0.5≤ x≤1.3) ceramics were synthesized using the solid state reaction method. The sintering behavior and dielectric characteristics of the BNN ceramics, as a function of the Ba-Na ratio, were examined. Densification of the samples with excess compositions of Ba and Na was higher than that of the stoichiometric BNN sample. The maximum dielectric constant and the Curie temperature showed highest values at the stoichiometric composition and decreased as the composition shifted away from the stoichiometry. in order to obtain a quantitative evaluation of the diffuse phase transition (DPT) behavior of the BNN ceramics, γ and C/κ_max were calculated. The weakest DPT behavior was observed in the stoichiometric composition. An increase in the DPT is in correlation with the increase in the number of ways of cation distribution by the disordered occupation of Ba and Na and the vacancies in the A1 and A2 sites of the tungsten bronze structure.     

Representations of max-stable processes via exponential tilting

The recent contribution (Dieker and Mikosch, 2015) obtained representations of max-stable stationary Brown–Resnick process ${\zeta }_Z\left(t\right),t\in {\mathbb{R}}^d$ with spectral process $Z$ being Gaussian. With motivations from Dieker and Mikosch (2015) we derive for general $Z$, representations for ${\zeta }_Z$ via exponential tilting of $Z$. Our findings concern Dieker–Mikosch representations of max-stable processes, two-sided extensions of stationary max-stable processes, inf-argmax representation of max-stable distributions, and new formulas for generalised Pickands constants. Our applications include conditions for the stationarity of ${\zeta }_Z$, a characterisation of Gaussian distributions and an alternative proof of Kabluchko’s characterisation of Gaussian processes with stationary increments.     

Crystal chemical and dielectric study of niobochromates with the tungsten bronze structure

Abstract

A crystal chemical study has allowed us to identify new niobochromates crystallizing with the tungsten bronze structure: Ba₂LnNb₄CrO₁₅ (Ln = Bi, La), La₂ANb₄CrO₁₅ (A = Li, Na, K) and Ba₂Na_1-x La _x Nb_5-x Cr _x O₁₅ (0 ? x ? 1). A dielectric study has shown that the T _c (x) curve goes through a minimum at x ? 0.5 along the solid solution Ba₂Na_1-x La _x Nb_5-x Cr _x O₁₅, while the ferroelastic transition T_c changes very slightly in the same range of composition.     

Morphological alterations in salivary glands of Rhipicephalus sanguineus ticks (Acari: Ixodidae) exposed to neem seed oil with known azadirachtin concentration

Neem (Azadirachta indica) has attracted the attention of researchers worldwide due to its repellent properties and recognized effects on the morphology and physiology of arthropods, including ticks. Therefore, this study aimed to demonstrate the effects of neem seed oil enriched with azadirachtin on salivary glands of Rhipicephalus sanguineus ticks, targets of great veterinary interest because of their ability to transmit pathogens to dogs. For this, R. sanguineus semi-engorged females were subjected to treatment with neem seed oil, with known azadirachtin concentrations (200, 400 and 600 ppm). After dissection, salivary glands were collected and evaluated through morphological techniques in light microscopy, confocal scanning laser microscopy and transmission electron microscopy, so that the possible relation between neem action and further impairment in these ectoparasites feed performance could be established. Neem oil demonstrated a clear dose-dependent effect in the analyzed samples. The agranular (type I) and granular acini (types II and III) showed, particularly in individuals treated with the highest concentrations of the product, cells with irregular shape, intense cytoplasmic disorganization and vacuolation, dilation of rough endoplasmic reticulum lumen, besides alterations in mitochondrial intermembrane space. These morphological damages may indicate modifications in salivary glands physiology, demonstrating the harmful effects of compounds present in neem oil on ticks. These results reinforce the potential of neem as an alternative method for controlling R. sanguineus ticks, instead of synthetic acaricides.     

On transitive algebras containing a standard finite von Neumann subalgebra

Let M be a finite von Neumann algebra acting on a Hilbert space H and A be a transitive algebra containing M^′. In this paper we prove that if A is 2-fold transitive, then A is strongly dense in B(H). This implies that if a transitive algebra containing a standard finite von Neumann algebra (in the sense of [U. Haagerup, The standard form of von Neumann algebras, Math. Scand. 37 (1975) 271-283]) is 2-fold transitive, then A is strongly dense in B(H). Non-selfadjoint algebras related to free products of finite von Neumann algebras, e.g., LFn and , are studied. Brown measures of certain operators in are explicitly computed.     

稀土钨青铜K0.71Nd0.028WO3的制备及其电性能

Tetragonal tungsten bronze K_0.71Nd_0.028WO₃ was synthesized by rare earth co-permeation method using Keggin type POMs of α-K₁₀[SiCu₃(OH₂)W₉O₃₇]·6H₂O (abbreviated as SiW₉Cu₃) as precursor. XRD, XPS, XRF, TG-DTA were used to characterize the resulting material. The XPS results indicate that Nd has permeated and diffused into the body of the sample and exists in tungsten bronze in the form of K_0.71Nd_0.028WO₃. The results of TG-DTA show that K_0.71Nd_0.028WO₃ begins to decompose at 320 ℃. The consequence of DC four-probe shows that the conductivity of the sample permeated by rare earth is 10³ times higher than that of the sample only permeated by methanol at room temperature. The conductivity of the sample only permeated by methanol is only 10^-3 S·cm^-1 but the conductivity of the sample permeated by rare earth is 1.65 S·cm^-1.