Isotope shift in the neon ground state by extreme-ultraviolet laser spectroscopy at 74 nm

Xenopus laevis oocytes underwent meiotic maturation in response to progesterone or insulin stimulation. However, the kinetics of the oocytes' response to the steroid was much faster than the response induced by insulin even under saturating hormone concentrations. This time differential was seen in oocytes that were stimulated with either hormone shortly after they were isolated from the animal. On the contrary, if oocytes were first cultured in MBS medium for 12-14 hours and then treated with either hormone, the oocytes responded to insulin and progesterone with similar kinetics. This result was not due to the ionic strength, potassium concentration or pH of the medium. The effect of storage in MBS was ligand specific for insulin. The extra 12-14 hours in MBS medium had no effect on the oocytes' response to progesterone.     

Study of erbium (III) doped titanium dioxide nanoparticles by photoacoustic spectroscopy

Nanocrystalline titania as photocatalyst has attracted considerable attention for its potential use in environmental cleaning. Recently, lanthanide ions doped titania samples have been shown to increase the photocatalytic efficiency of selected reactions. In this work, TiO₂ nanoparticles doped with Er³⁺ were prepared via an ultrasonic assisted sol-gel method. The optical properties of the samples were determined by photoacoustic (PA) spectroscopy. It was found that the absorption edge shifted to lower wavelength when the particle size fell into nanometer range, which is the evidence of a quantum size effect. The nature of ligand bonding to Er³⁺ and the structural properties were investigated with the PA absorptions of the f-f transitions of Er³⁺, which are sensitive to the local environment. The results showed that TiO₂ gel heated at 70 °C still contained abundant trapped water and ethanol, and the environment around Er³⁺ was similar to the one in the aqueous ion. The “degree of covalency” for Er³⁺ bonding increased continuously during the gel-to-anatase transition. For the sample calcined at 1100 °C, however, the f-f transitions of Er³⁺ showed blue shifts and the intensity of the hypersensitive transition decreased, indicating an increase of ionicity in the Er³⁺ bonding. This can be attributed to the segregation of Er³⁺ ions to the external surface, forming Er₂Ti₂O₇ during the anatase-to-rutile transition, which was confirmed with XRD and TEM measurements.     

X射线荧光光谱法测定硝酸铒溶液中铒

铒在核反应堆中常做为可燃毒物,该类可燃毒物在制造过程中需对铒进行精确测量,即对工艺过程中的硝酸铒溶液中铒进行测量。实验建立了X射线荧光光谱法(XRF)测定硝酸铒溶液中铒含量的分析方法。结果表明,当选择LiF200晶体时,铒的角度扫描图峰形比较完整;当选择准直器150μm时,铒的峰背比最为好;当选择功率为40kV×40mA时,仪器的综合性能和计数率比较好。铒的质量浓度在1~15mg/mL范围内与其特征线ErLα的强度呈线性,校准曲线的相关系数为0.993 6。对硝酸铒标准溶液和硝酸铒实际样品溶液进行测定,并与电感耦合等离子体原子发射光谱(ICP-AES)的测定结果进行比对,两种方法的测定结果一致,实验方法测定结果的相对标准偏差(RSD,n=6)低于0.7%。     

Circular dichroism spectroscopy of Lucina I hemoglobin

The monomeric hemoglobin from the mollusc Lucina pectinata (HbI) represents an interesting model system for the study of heme-related circular dichroic (CD) bands in view of the highly asymmetric distribution of aromatic residues around the heme pocket revealed by the X-ray crystal structure. The CD spectra of both ferrous and ferric HbI derivatives exhibit negative CD bands in the Soret and ultraviolet region with an enhanced ellipticity of the heme N and L bands in the near-UV region. In contrast, the magnitude of the Cotton effect in the visible and Soret regions is comparable to that observed in other hemoproteins. The spectrum of the carbon monoxide derivative shows a surprising similarity with that observed for the soybean leghemoglobin carbon monoxide adduct. A common structural feature in the two proteins is the presence in the distal pocket of two Phe residues (B9 and B10) the aromatic rings of which are perpendicular to the heme plane.     

Electrochemical behaviour of erbium and preparation of Mg-Li-Er alloys by codeposition

The electrodeposition of erbium on molybdenum electrodes and the formation of Mg-Li-Er alloys were investigated in LiCl-KCl molten salts. At a molybdenum electrode, the electroreduction of Er (III) proceeded in a one-step process involving three electrons. The diffu-sion coefficient of erbium ions in the melts was determined by cyclic voltammetry, chronopotentiometry and chronoamperometry respectively. Cyclic voltammograms (CVs) showed that the underpotential deposition (UPD) of lithium on pre-deposited Mg-Er alloy led to the formation of a Mg-Li-Er alloy. X-ray diffraction (XRD) indicated that Er5Mg24 phase was formed via potentiostatic electrolysis. Scanning electron microscopy (SEM) showed that Er atoms mainly concentrated at the grain boundaries while Mg element evenly located in the alloy.     

Time-resolved fluorescence and absorption spectroscopy of photosystem I

Picosecond fluorescence and femtosecond transient absorption spectroscopy have been used to investigate the primary energy transfer and trapping processes in a photosystem II deletion mutant from the cyanobacterium Synechocystis sp. PCC 6803, which contains active photosystem I reaction centers with approximately 100 chlorophylls per P700. In all experiments, low levels of excitation were used which avoid annihilation processes. Following 590-nm excitation, at room temperature, spectral equilibration is observed in both fluorescence and absorption measurements and is characterized by a time constant of 4-6 ps. The shape of the spectra associated with the equilibration process indicates that long wavelength pigments (pigments with absorption maxima at longer wavelength than that of the primary electron donor, P700) are present and functional at physiological temperatures in this preparation. The overall decay of excitations in the antenna is characterized by a time constant of 24-28 ps, in both fluorescence and absorption measurements. The 24-28-ps process results in the appearance of absorption changes associated with only P700+ formation. Absorption changes associated with the reduction of the primary electron acceptor were not resolved under the experimental conditions used here.