抗坏血酸有机锗倍半氧化物的合成及抗癌活性研究

通过三氯锗仿与抗坏血酸分子的加成反应,合成了一种新型有机锗倍半氧化物,产物的结构通过元素分析、IR及UV光谱等方法进行了表征．生物活性实验表明合成物对小鼠S-180肿瘤生长具有显著的抑制作用．     

Effects of masker-spectral variability and masker fringes in children and adults

This study examined the degree to which masker-spectral variability contributes to children's susceptibility to informational masking. Listeners were younger children (5-7 years), older children (8-10 years), and adults (19-34 years). Masked thresholds were measured using a 2IFC, adaptive procedure for a 300-ms, 1000-Hz signal presented simultaneously with (1) broadband noise, (2) a random-frequency ten-tone complex, or (3) a fixed-frequency ten-tone complex. Maskers were presented at an overall level of 60 dB SPL. Thresholds were similar across age for the noise condition. Thresholds for most children were higher than for most adults, however, for both ten-tone conditions. The average difference in threshold between random and fixed ten-tone conditions was comparable across age, suggesting a similar effect of reducing masker-spectral variability in children and adults. Children appear more likely to be susceptible to informational masking than adults, however, both with and in the absence of masker-spectral variability. The addition of a masker fringe (delayed onset of signal relative to masker) provided a release from masking for fixed and random ten-tone conditions in all age groups, suggesting at least part of the masking observed for both ten-tone maskers was informational.     

Investigation of the quantitative properties of the quadrupole orthogonal acceleration time-of-flight mass spectrometer with electrospray ionisation using 3,4-methylenedioxymethamphetamine

This paper describes the investigation of the potential of a quadrupole orthogonal acceleration time-of-flight mass spectrometer (Q-TOF) equipped with an atmospheric pressure ionisation interface for quantitative measurements of small molecules separated by reversed phase liquid chromatography. To this end, the detection limits and linear dynamic range in particular were studied in an LC/MS/MS experiment using 3,4-methylenedioxymethamphetamine standards and 3,4-methylenedioxyethylamphetamine for internal standardisation. In a second phase, the experiment was repeated with real biological extracts (whole blood, serum, and vitreous humour). A calibration for 3,4-methylenedioxymethamphetamine and its metabolite 3,4-methylenedioxyamphetamine was prepared in each of these matrices again using 3,4-methylenedioxyethylamphetamine as internal standard. The resulting quantitative data were compared with those obtained by liquid chromatography with fluorescence detection for the same extracts. The Q-TOF results revealed excellent sensitivity and a linear dynamic range of nearly four decades (2-10 000 pg on-column, r(2) = 0.9998, 1/x weighting). Furthermore, all the calibration curves prepared in biological material were superimposable, LC/MS/MS and LC-fluorescence, and the quantitative results for actual samples compared very favourably. It was concluded that the Q-TOF achieves a linear dynamic range for quantitative LC/MS/MS work exceeding that of fluorescence detection and at much better absolute sensitivity. Copyright 1999 John Wiley & Sons, Ltd.     

Observation of picosecond modulated electron beams from the plasma focus

The electron beam emitted from the plasma focus was investigated by means of a ?erenkov detector streak camera equipment. The electron beam is measured to be strongly modulated with periods of about 25 ps.     

Structure of the Hoyle state in 12C

The first excited 0(+) state in 12C (Hoyle state) has been predicted to be a dilute self-bound gas of bosonic alpha particles, similar to a Bose-Einstein condensate. To clarify this conjecture, precise electron scattering data on form factors of the ground state and the transition to the Hoyle state are compared with results of the fermionic molecular dynamics model, a microscopic alpha-cluster model, and an alpha-cluster model with reduced degrees of freedom (in the spirit of a Bose-Einstein condensed state). The data indicate clearly a dilute density with a large spatial extension of the Hoyle state. A closer inspection of the model calculations, which reproduce the experimental findings, reveals that the term Bose-Einstein condensation of three alpha particles must not be taken too literally.     

Universality of Short-Range Nucleon-Nucleon Correlations in Nuclei

We investigate the short-range correlations in light nuclei. The highly correlated many-body states are obtained with an explicitly correlated basis which enables us to get a precise solution of a many-body Schrödinger equation for a realistic interaction. We show two-body density distributions for the different spin-isospin channels calculated from three- and four-body states to investigate the short-range correlations between nucleon pairs. At distances below 1 fm a universal behavior is found which does not depend on the many-body states. The universality is also seen in high momentum components of the two-body momentum distributions.     

An in situ corrosion study of Middle Ages wrought iron bar chains in the Amiens Cathedral

The corrosion behaviour of Middle Ages wrought iron bar chains exposed to indoor atmospheric corrosion for hundred of years in the Notre Dame Cathedral of Amiens (France) has been evaluated by means of Electrochemical Impedance Spectroscopy (EIS), a well-established electrochemical technique extensively used for testing anticorrosive properties of metal coatings. The measurements have been performed in situ with a portable EIS instrument designed to work as a standalone device, in six different areas of the wrought iron bar chains characterized by different aesthetical appearance. Moreover, a properly designed electrochemical cell has been employed to carry out the impedance measurements without affecting the artefacts surfaces. The wrought iron bar chains, as evidenced by μ-Raman and microscopic analyses, are covered by corrosion products constituted by iron oxides and oxyhydroxides, such as goethite, lepidocrocite, maghemite, akaganeite, organized in complex layered structures. In situ EIS allows one to investigate the phenomena involved at the electrochemical interfaces among the various corrosion products and to assess and predict their corrosion behaviour. From the analysis of the experimental findings of this monitoring campaign, EIS measurements can be proposed to restorers/conservators as a reliable indicator of dangerous situations on which they must act for the preservation of the iron artefacts.