Reduction properties of phases in the system La0.5Sr0.5MO3 (M=Fe, Co)

Phases formed by the reduction of compounds of the type La_0.5Sr_0.5MO₃ (M=Fe, Co) have been characterized by means of temperature programmed reduction, X-ray powder diffraction, ⁵⁷Fe Mössbauer spectroscopy and Fe K-, Co K-, Sr K-, and La L_III-edge X-ray absorption spectroscopy. The results show that treatment of the material of composition La_0.5Sr_0.5FeO₃ (which contains 50% Fe⁴⁺ and 50% Fe³⁺) at 650 °C in a flowing 90% hydrogen/10% nitrogen atmosphere results in the formation of an oxygen-deficient perovskite-related phase containing only trivalent iron. Further heating in the gaseous reducing environment at 1150 °C results in the formation of the Fe³⁺-containing phase SrLaFeO₄, which has a K₂NiF₄-type structure, and metallic iron. The material of composition La_0.5Sr_0.5CoO₃ is more susceptible to reduction than the compound La_0.5Sr_0.5FeO₃ since, after heating at 520 °C in the hydrogen/nitrogen mixture, all the Co⁴⁺ and Co³⁺ are reduced to metallic cobalt with the concomitant formation of strontium- and lanthanum-oxides.     

Synthesis and photophysical behaviors of temperature/pH-sensitive polymeric materials. I. Vinyl monomer bearing 9-aminoacridine and polymers

A novel acrylic monomer bearing acridinyl group, acridine-9-N-acrylamide (Ac-9AA) was synthesized from 9-aminoacridine (9AA) and acryloyl chloride in the presence of triethylamine in dry dichloromethane (CCl₂) at room temperature. The synthesized Ac-9AA was identified by IR, MS and ¹H NMR spectra. Homopolymer of Ac-9AA was obtained using AIBN as a thermal initiator in THF under 65-70 °C and the average molecular weights (M_w) of poly(Ac-9AA) obtained was very low, being in the order of ca. 10³. Copolymer of Ac-9AA and acrylamide was synthesized with thermal initiator and poly(Ac-9AA-co-AM) was characterized by the method of IR, UV-vis and DSC. The photophysical behaviors of Ac-9AA and its polymers were explored by recording the fluorescence spectra in solution, solid and film. In addition, the pH and temperature dependence on fluorescence of the water-soluble poly(Ac-9AA-co-AM) were investigated in detail. The results showed that the relative fluorescence intensity of poly(Ac-9AA-co-AM) had an excellent linear response to temperature in the range of 0-60 °C. Moreover, the fluorescence intensity increased continuously from low pH to high pH while the excitation maxima at 388 nm and emission maxima at 400 nm had redshift after the addition of HCl or NaOH, which results from the fact that the predominance of tautomeric forms of Ac-9AA changed at different medium. This investigation may provide a convenient way to prepared multifunctional macromolecule biomaterial bearing aminoacridine to probe pH and temperature in biological system.     

四氢萘热解中间产物及其反应机理的进一步研究

在四氢萘热解实验中,我们曾注意到,某些热解产物如甲基茚(?)和正丁基苯有进一步的反应.对这些中间产物做热解实验,无疑将为更全面了解四氢萘热解反应机理提供新的信息.对四氢萘热解反应,我们曾提出了自由基反应机理,在四氢萘中加入一些自由基引发剂,将会为自由基反应机理的假设提供一些实验上的旁证.     

Source tracing of chromium-, manganese-, nickel- and zinc-containing particles (PM<Subscript>10</Subscript>) by micro-PIXE spectrum

Due to the interesting anti-proliferative properties of gallium-thiosemicarbazone complexes, the production of [⁶⁷Ga]labeled 2-acetylpyridine 4,4-dimethyl thiosemicarbazone (APTSM₂) was investigated. The freshly prepared [⁶⁷Ga]GaCl₃ was mixed with 2-acetylpyridine 4,4-dimethyl thiosemicarbazone for 60 minutes at 90 °C to yield [⁶⁷Ga]APTSM₂ with a radiochemical yield of more than 98%. Radio-thin-layer-chromatography (RTLC) showed a radiochemical purity of more than 99%. A specific activity of about 370–740 MBq/mmol (10–20 Ci/mmol) was obtained. The stability of the final product was checked in the absence and presence of human serum at 37 °C. The partition coefficient of the final complex was also determined. The biodistribution of the labeled compound in normal rats was compared with that of free Ga³⁺ cation up to 22 hours.     

腙型双冠醚对碱金属的配位性能

本文报道了五个腙型双冠醚的合成。电导测定结果表明含苯并-15-冠-5单元的双冠醚与四苯基硼酸钾、铷、铯,含苯并-18-冠-6单元的双冠醚与四苯基硼酸铯生成2:1夹心型配合物(冠醚单元:金属离子)。并用这些双冠醚的氯仿溶液萃取苦味酸碱金属盐水溶液,测定了萃取百分率和计算了萃取平衡常数,结果表明腙型双冠醚的萃取能力及选择性优于相应的单冠醚。     

Molecular activation analysis for chemical species studies

Molecular activation analysis (MAA) refers to an activation analysis method that is able to provide information on the chemical species of elements in systems of interest, though its exact definition has yet to be assigned. Its development is strongly stimulated by the urgent need to know the chemical species of elements, because knowledge of bulk contents or concentrations is often insufficient to judge biological, environmental or geochemical effects of elements. The features, methodology and limitations of MAA are outlined, as well as the up-to-date MAA progress in our laboratory. Received: 14 August 1998 / Revised: 30 November 1998 / Accepted: 1 December 1998     

Organelle Tracking in a Living Cell with Microsecond Time Resolution and Nanometer Spatial Precision

The study of cellular processes such as organelle transport often demands particle tracking with microsecond time‐resolution and nanometer spatial precision, posing significant challenges to existing tracking methods. Here, we have developed a novel strategy for two‐dimensional tracking of gold nanoparticles (GNPs) with 25 μs time resolution and ～1.5 nm spatial precision, by using a quadrant photodiode to record the positions of GNPs in an objective‐type dark‐field microscope. In combination with a feedback loop, this technique records long, high time‐resolution and spatial precision trajectories of endocytosed GNPs transported by the molecular motors kinesin and dynein in a living cell. In the full range of organelle velocities (0–8 μm s^?1), we clearly resolve the individual 8 nm steps of cargoes carried by kinesin, and the 8, 12, 16, 20, and 24 nm steps of those carried by dynein. These experiments yield new information about molecular motor stepping in living cells.     

Information Geometry of the Exponential Family of Distributions with Progressive Type-II Censoring

In geometry and topology, a family of probability distributions can be analyzed as the points on a manifold, known as statistical manifold, with intrinsic coordinates corresponding to the parameters of the distribution. Consider the exponential family of distributions with progressive Type-II censoring as the manifold of a statistical model, we use the information geometry methods to investigate the geometric quantities such as the tangent space, the Fisher metric tensors, the affine connection and the α-connection of the manifold. As an application of the geometric quantities, the asymptotic expansions of the posterior density function and the posterior Bayesian predictive density function of the manifold are discussed. The results show that the asymptotic expansions are related to the coefficients of the α-connections and metric tensors, and the predictive density function is the estimated density function in an asymptotic sense. The main results are illustrated by considering the Rayleigh distribution.     

Non-isothermal crystallization kinetics and melting behavior of EAA with different acrylic acid content

Non-isothermal crystallization kinetics and subsequent melting behavior for three kinds of ethylene-acrylic acid copolymer (EAA) are investigated via differential scanning calorimetry (DSC). From the Jeziorny method, the crystallization rate of the primary stage is significantly influenced by the competitive mobility of chains. While the crystallization rate in the secondary stage decreases in order of acrylic acid (AA) content in copolymers. Mo’s method can also provide a good fitting. Difference between the Jeziorny method and Mo’s method analysis is because of a higher effect of non-crystallizable chain ends. The effective activation energy is also determined via Kissinger’s method.