Quantitation of vitamin K in human milk

A quantitative method was developed for the assay of vitamin K in human colostrum and milk. The procedure combines preparative and analytical chromatography on silica gel in a nitrogen atmosphere followed by reversed phase high performance liquid chromatography (HPLC). Two HPLC steps were used: gradient separation with ultraviolet (UV) detection followed by isocratic separation detected electrochemically. Due to co-migrating impurities, UV detection alone is insufficient for identification of vitamin K. Exogenous vitamin K was shown to equilibrate with endogenous vitamin K in the samples. A statistical method was incorporated to control for experimental variability. Vitamin K₁ was analyzed in 16 pooled milk samples from 7 donors and in individual samples from 15 donors at 1 month post-partrum. Vitamin K₁ was present at 2.94±1.94 and 3.15±2.87 ng/mL in pools and in individuals, respectively. Menaquinones, the bacterial form of the vitamin, were not detected. The significance of experimental variation to studies of vitamin K in individuals is discussed.     

玻璃纤维/大麻纤维增强聚丙烯混杂复合材料的力学性能和断裂特征(英文)

目前在土木工程,建筑,汽车等领域里使用的复合材料中,玻璃纤维是用量最大的增强材料。由于保护地球环境的呼声日趋高涨,天然纤维被期待着代替源于石油而且再利用困难的玻璃纤维,成为绿色复合材料的必要材料之一。本文通过注射成型工艺制作了玻璃短纤维,大麻短纤维以及混杂型纤维增强复合材料,并在拉伸实验中应用两种不同频率的声发射技术检测了拉伸断裂特性。实验发现,随着大麻纤维的加入和混杂复合材料绿色度的增加,复合材料的拉伸弹性模量随之线性增大,而拉伸强度基本保持不变。当大麻纤维的含量超过20wt%的时候,拉伸强度开始降低。在不同频率的声发射实验中,混杂型复合材料的声发射事件的产生都比单一纤维增强型复合材料要来的晚,也就是说,纤维的混杂有助于推迟微裂纹的产生。     

Gamma-ray radiation hardened properties of pure silica coresingle-mode fiber and its data link system in radioactive environments

The radiation resistances of pure silica core single-mode optical fiber (Si-SMF) and its data link module at 1.30 μm were investigated. It was found that the induced loss of fibers exposed to γ-rays at a low dose rate was proportional to the 0.54 power of total dose from the result of a low dose rate irradiation test for 3 years, and the induced loss for 40 years aging at 1 R/h was estimated to be 1.8 dB/km. It was ascertained that transmission is achievable at a bit rate of 125 Mb/s even under high dose rate irradiation to a total dose of 10⁸ R, which corresponds to the postulated maximum γ-ray exposure in nuclear power plants     

Hydroxyl group formation caused by hydrogen diffusion into optical glass fibre

Transmission loss increase of optical glass fibre caused by hydrogen diffusion is measured as a function of temperature and partial pressure of hydrogen gas. The activation energy of hydroxyl group formation from the diffused molecular hydrogen was found to be 15.9 kcal/mole. Also the hydroxyl absorption loss increase at 200°C was found to be proportional to the square root of the partial pressure of hydrogen gas.     

PREPARATION OF AMORPHOUS Ti-Pd ALLOYS AND THEIR PHYSICAL PROPERTIES

The amorphous Ti_(l_x)Pd_x alloys within a wider composition range of 0.25相似文献   

NUMERICAL SIMULATION OF FORGING AND SUBSEQUENT HEAT TREATMENT OF A ROD BY A FINITE VOLUME METHOD

1.air-nonAtypicalindustrialmetalcoml,onentwouldoftenbemadeviatheforgingandheattreatm',ntoperationsintilenlarlufacturingstage.IntiledesignOfforgingprocesses,informationisllecesstllysuchasmaterialflowinthedies,levelofdiefill,del'ects,strain,stress,temperaturedistributioninthebarkpiecesaxltlthedies,andforgingforce.InthesubseqUentheattreatmentoperations,illf(,mlationoncolllbinationOfrnicrostructure,residualstressesanddiTocnsionalaccuracyintilel'illalproductalealsoveryimportant.Suchinformationmay…     

Study of fluorine doping during vapour-phase axial deposition sintering process

The fluorine doping process of pure silica soot with various type of fluorine gases in the vapour-phase axial deposition (VAD) sintering process was investigated in detail. This investigation showed that the doping level is proportional to the 1/4 power of the concentration of the fluorine gas, and the achievable reduction of relative refractive index is –0.75% with this process. The kinetic investigation clarified that the fluorine doping process consists of the doping and dissociation reactions; the former reaction obeys the 1/2 power of the SiF₄ partial pressure and the latter the two power of fluorine content [SiO_1.5F], where SiO_1.5F represents a silicon tetrahedron consisting of one fluorine and three bridging oxygen atoms in glass. The fluorine content is proportional to the 1/4 power of the SiF₄ partial pressure at an equilibrium where the doping reaction is in competition with the dissociation reaction.     

Transient sheath voltage characteristics of a crossbonded cable installed within a tunnel

The wave-propagation characteristics of a cable installed within a tunnel has been investigated. The transient characteristic of this cable system differs from that of a cable system in which the cables are buried without tunnels. The transient characteristic is heavily dependent on both the distance from the cable to the tunnel wall and the physical parameters of the tunnel. A modeling method of the cable system installed within a tunnel is proposed based on investigation. A field measurement of transient sheath voltages on a 275 kV crossbonded cable system is made. Numerical results obtained using the proposed model agree well with field test results; thus the accuracy of the modeling method proposed in this paper is confirmed. The effects of the circuit parameters, such as inductance of the sheath bonding wire and the equivalent capacitance of the sheath protection arrester, are studied.     

等规聚丙烯及其共混复合体系的辐射交联

本文研究了等规聚丙烯(i-PP)及其共混复合体系(PP/HDPE,PP/EPDM)辐射交联凝胶生成动力学。对于半结晶结构的i-PP,辐射交联的溶胶分数s随辐照剂量R的变化,符合裂解度正比于辐照剂量R的β次方的假定(β是与高聚物结构相关的参数),即 R(s+s~(1/2))与R~β具有很好的线性关系。对于i-PP共混体系,利于扫描电子显微镜和动态力学粘弹谱仪研究了其相结构特征和组分间的相互作用。结果表明,在一定剂量范围内共混体系的R~β可以修正为:R~β=∑X_iR~(βi)(X_i,β_f分别为共混物中第i组分的重量分数和β值)。用修正后的R~β处理PP/HDPE,PP/EPDM共混体系的凝胶生成数据,结果R(s+s~(1/2))司与R~β之间都具有很好的线性关系。     

Pulsed NMR study on the hydration of poly(acrylic acid) salts

Summary Pulsed NMR was applied to measure the spin-lattice (T₁) and spin-spin (T₂) relaxation times of the equilibrium water absorbed in poly(acrylic acid) lithium salt, sodium salt, and potassium salt. T₁ and T₂ relaxation time curves for the samples of lithium and sodium salts studied showed single phase behavior, but the sample of potassium salt exhibited two-phase behavior, indicating the existence of water fraction of higher mobility.