X-射线荧光光谱法分析硅质耐火材料的主次成分

采用硅石标准样品作为校准样品,建立了熔融制样X-射线荧光光谱法测定硅质耐火材料中SiO2、Al2O3、CaO、MgO、P2O5、Fe2O3、TiO2、K2O、Na2O的方法.采用熔融法为样品片和校准片的制备方法,选择四硼酸锂-偏硼酸锂(质量比为67∶33)为助熔剂,1.00mL LiBr溶液为脱模剂,熔融温度1100℃...     

X射线荧光光谱法测定化探样品中主、次和痕量组分

采用粉末样品压片制样,用PW2440X射线荧光光谱仪对化探样品中氯、溴、硫、氧化钠、氧化镁、三氧化二铝、二氧化硅、磷、氧化钾、氧化钙、钛、锰、三氧化二铁、钴、铌、锆、钇、锶、铷、铅、钍、锌、铜、镍、钒、铬、钡、镧、铈、钕、钪、镓、砷、铪等34个组分进行测定。讨论了微量元素的背景选择和谱线重叠校正及氯测定的问题。使用经验系数法和康普顿散射线作内标校正基体效应,经标准物质检验,分析结果与标样值吻合,用GBW 07308国家一级标准物质作精密度试验,统计结果RSD（n=12）除砷、钒、镍、铜〈6．0％,溴、硫、铈、铪、钕、钪、氧化钠、镧、铬、钴和钍〈14．0％以外,其余各组分均小于3．0％。     

CAROTENOID PIGMENTS AND THE IN VIVO SPECTRUM OF BACTERIOCHLOROPHYLL

Abstract— The isolation of a mutant, strain PM-9, of Rhodopseudonionus spheroides with an abnormal complement of carotenoid pigments is described.
PM-9 accumulates phytoene, phytofluene, ζ-carotene and neurosporene. Semi-aerobic cultures form more ζ-carotene and neurosporene relative to total carotenoids than do photo-synthetic cultures.
PM-9 is killed on exposure to light and oxygen.
By making use of the effect of oxygen on the nature of the carotenoids in PM-9, we have shown that these pigments do not directly influence the in vivo spectrum of bacteriochlorophyll.
Diphenylamine inhibits the synthesis of coloured carotenoids in Rhodopseudonionos gelatinosa but does not change the bacteriochlorophyll spectrum.     

FLUORESCENCE AND LUMINESCENCE STUDIES OF IN VIVO CHLOROPHYLL WITH A LASER PHOSPHOROSCOPE*

Abstract— A simple apparatus using a He-Ne laser and a rotating sector gives repetitive light pulses with rise and fall times of a few μsec and intensities of up to 0.65 W/cm². Fluorescence during the actinic pulse and luminescence following it (after 20 μsec) may be recorded and compared. Sampling of the suspension of photosynthetic cells or chloroplasts by intermittent flow permits the averaging of 25 such measurements. With Chlorella, the fast (30 μsec) and the medium (30 msec) components of luminescence do not saturate at the same light intensity. The former saturates in the same range as the photochemical fluorescence rise, whereas the latter saturates at higher intensities. Under a variety of conditions, the decay of luminescence intensity is always strongly polyphasic. Analysis of the kinetics discloses a dependency with the log concentration of the hypothetical precursor, suggesting a connection of luminescence with electrochemical phenomena. The shape of the luminescence integral, as well as the light saturation pattern, suggests another kind of interpretation, in terms of several pools, possibly two of equal size. In the presence of hydroxylamine, only one pool is seen. The stimulating effect of preillumination is only observed for the medium component. However, a stimulation of short duration also exists for the fast component. The problems of number of pools, mechanism, and stimulation are briefly discussed.     

POLARIZATION OF FLUORESCENCE FROM BACTERIOCHLOROPHYLL IN CASTOR OIL, IN CHROMATOPHORES AND AS P870 IN PHOTOSYNTHETIC REACTION CENTERS

Abstract— The polarization of fluorescence from isolated photosynthetic reaction centers and from light harvesting chlorophyll in photosynthetic units was measured over a wide range of exciting wavelengths. In addition, the fluorescence polarization of bacteriochlorophyll was measured. The simplest interpretation of the data is that in the bacterial reaction center, the three chlorophyll molecules closely associated with photochemical oxidation do not have their transition moments parallel to one another. Highly polarized fluorescence was also observed from the intact photosynthetic unit.     

FLUORESCENCE QUANTUM YIELDS AND LIFETIMES FOR BACTERIOCHLOROPHYLL c

Abstract— Absorption and emission spectra of bacteriochlorophyll c dissolved in a variety of solvents were measured and fluorescence quantum yields determined from the integrated emission spectra. Values for the emission maxima calculated from the positions and bandwidths of the red absorption band using the Stepanov relationship agreed closely with the experimental values. Fluorescence quantum yields varied between 0.10 in methanol and 0.36 in tetrahydrofuran and in dibutylamine. Fluorescence lifetimes were also determined for bacteriochlorophyll c in four of the solvents, and ranged from 2.7 ns in methanol to 7.6 ns in dimethylsulfoxide.     

PHOTOINDUCED ONE-ELECTRON TRANSFER BETWEEN BACTERIOCHLOROPHYLL AND QUINONE IN ACETONE*

Abstract— Illumination with red light of a degassed solution of bacteriochlorophyll and benzoquinone or ubiquinone in dry acetone at low temperatures (< - 105°C) leads to the formation of the bacteriochlorophyll cation radical and the quinone anion radical, as detected by ESR spectroscopy. At temperatures around - 110°C, the quinone radical signal corresponds to an emission of microwave radiation. These results are interpreted in terms of a one-electron transfer from a spin-polarized bacteriochlorophyll triplet state to the quinone, producing an anion radical which is predominantly in the upper spin state.     

FLUORESCENCE YIELD PROPERTIES OF A FRACTION ENRICHED IN NEWLY SYNTHESIZED BACTERIOCHLOROPHYLL U-PROTEIN COMPLEXES FROM RHODOPSEUDOMONAS SPHAEROIDES

Abstract— A membrane fraction enriched in newly synthesized bacteriochlorophyll a-protein complexes was isolated from Rhodopseudomoms sphaeroides by rate-zone sedimentation. An examination of the fluorescence yield properties showed that the ratio of the maximal fluorescence emission near 910 nm (with all photochemical traps closed) to that of the initial fluorescence rise (with all traps open) was 2.2 compared to 2.9 in chromatophores. The spectrum for the variable portion of the fluorescence emission (the slow rise between the initial and maximal levels) was essentially the same in both fractions, but that observed for the initial rise in the newly synthesized material showed a greater fluorescence yield with a broad peak near 865 nm. This extra emission is thought to arise from the light-harvesting bacteriochlorophyll complex with an absorption maximum at 850 nm and suggests that this component is only partially connected to photosynthetic units. In contrast, the little extra emission observed at the longer wavelengths in this fraction indicated that energy is transferred more efficiently between the 875 nm antenna complex and photochemical reaction centers. The kinetics of the fluorescence rise suggest that photosynthetic units exist at separate sites in newly synthesized membrane regions.     

IN VIVO FLUORESCENCE SPECTROSCOPY OF CHLOROPHYLL IN VARIOUS UNRIPE AND RIPE FRUIT

—Low temperature (77 K) fluorescence emission spectra of slices obtained from the peel and various layers of the pericarp were recorded for fruits which remain green or undergo color break during ripening.
Fluorescence emission peaks characteristic of the photosystem II antennae (λ_F 686 nm) and reaction center (λ_F 696 nm), as well as of the photosystem I antenna (λ_F 730-740 nm), were present in the peel and all parts of the green pericarp of ripe kiwi, avocado and cantaloupe, as well as in ripe tomato and tangerine after color break. The pattern of the fluorescence emission spectra of all samples except that of the kiwi fruit was similar to that obtained from green photosynthetic tissue of leaves, indicating a normal organization of the chlorophyll-containing complexes of thylakoidal membranes. This pattern is characterized by a significantly higher emission at 730-740 nm relative to that of the 696 and 686 nm peaks. In contradistinction, the fluorescence emission at 686 and 696 nm was higher than that at 730 nm in the kiwi fruit, indicating a reduction in the size of the photosystem I antenna chlorophyll. In the innermost yellowish layers of the kiwi pericarp, a further loss of this antenna occurred, as well as disorganization of the photosystem II complex. The above conclusions are suggested also by measurements of variable fluorescence kinetics.
The results presented here indicate that fluorescence spectroscopy might be used as a tool for the study of chlorophyll organization during the growth and ripening periods of fruit.     

NON-INVASIVE TECHNIQUE FOR OBTAINING FLUORESCENCE EXCITATION AND EMISSION SPECTRA IN VIVO

An intensified photodiode array forms the heart of a sensitive spectrophotofluorometry system that permits the rapid and non-invasive determination of fluorescence emission spectra in the skin of living, non-anesthetized animals. Using this system, we found it possible to obtain good emission and excitation spectra of the material responsible for the weak red fluorescence that characterizes normal mouse skin, and to follow the biosynthesis and subsequent clearance of protoporphyrin IX in the skin of non-anesthetized mice that had been given various doses of the porphyrin precursor 5-aminolevulinic acid.     

PHOTOTOXICITY FROM BENOXAPROFEN: IN VIVO AND IN VITRO STUDIES

Abstract Benoxaprofen (2-[4-chlorophenyl]-α-methyl-5-benzoxazole acetic acid), a non-steroidal antiinflammatory drug, was found to provoke phototoxicity reactions in humans. Exposure of the skin of benoxaprofen-treated subjects to either solar simulating radiation or a broad UV-A wavelength band produced intense itching and burning sensations, followed by the development of a classical wheal and flare response within 2-4 min. Phototoxicity was related to both the UV radiation fluence and the dose of orally administered benoxaprofen. Wavelengths between 320 and 340nm were active in provoking urticaria. In vitro studies demonstrated that benoxaprofen and UV irradiation produced a dose-dependent lysis of sheep erythrocytes which did not appear to be dependent on the presence of oxygen. Red cells were not lysed by pre-irradiated benoxaprofen arguing against the production of stable lytic photoproducts. Human neutrophils were lysed by benoxaprofen and UV light which resulted in the liberation of both cytoplasmic and lysosomal enzymes. Benoxaprofen failed to induce photolysis of human platelets and photoactivation of complement in human serum. It is suggested that phototoxic urticaria provoked by benoxaprofen may be due to a direct photolytic effect on human dermal mast cells.     

SPECTROSCOPIC ANALYSIS OF BACTERIOCHLOROPHYLLS IN VITRO AND IN VIVO*

Abstract— Chromatophores from Rhodopseudonionas spheroides were treated with potassium iridic chloride so as to destroy the major complement of bacteriochlorophyll (BChl) without harming the photochemically active P870. A band at 802 mμ, attributed to a pigment P800, survived this treatment along with P870. Extraction of such chromatophores with a mixture of acetone and methanol removed the absorption bands of P800 and P870; a corresponding amount of BChl was found in the extract. The yield of BChl was too great to have been derived from either P800 or P870 alone; analysis of extinction cofficients and band areas of these pigments indicates that they are both specialized fornis of BChl, in a molecular ratio of 2P800:1P870. Bleaching of P870, without attenuation of the absorption band of P800, could be effected by adding potassium ferricyanide to the iridic chloride-treated chromatophores. Extraction of chromatophores in this condition gave a reduced yield of BChl, consistent with a 2:1 ratio of P800 to P870 under the assumption that the BChl in the extract was derived in this case from P800 alone. An absorption band at 600 mμ in iridic chloride-treated chromatophores, characteristic of BChl and ascribed to P800 and P870, is partly bleached and shifted to shoiter wavelengths upon illumination. This reversible effect, and a similar one near 375 mμ (corresponding to the Soret band maximum of BChl), has the combined attributes of the blue-shift of P800 and the bleaching of P870 seen in a spectrally resolved form near 800 and 865 mμ respectively. The 600 mμ band is bleached by about 30 per cent, again consistent with a ratio of 2P800:1P870. These data, in conjunction with information published elsewhere, support the view that two molecules of P800 and one of P870 are associated jointly with a photosynthetic reaction center. It was observed that the long wave absorption bands of BChl in vivo are sometimes narrower than the narrowest bands that have been observed for BChl in dilute organic solutions. Sharpness of these bands is most conspicuous in some forms absorbing near 800 mμ.     

PICOSECOND TIME RESOLVED FLUORESCENCE OF CHLOROPHYLL IN VIVO

Abstract. The published data concerning the fluorescence kinetics of chlorophyll a in various photosynthetic species are reviewed. The effects of singlet-singlet and singlet-triplet annihilation induced by excessively high incident light intensities are discussed and related to the changes produced in the fluorescence lifetimes and quantum yields. We also review the fluorescence lifetimes of Chlorella pyrenoidosa and spinach chloroplast fragments under a variety of experimental conditions; these measurements were performed at single pulse excitation intensities of less than 5 × 10¹³ photons cm^–2 where distortion due to annihilation processes is negligible. Evidence for and against a time dependent rate equation for energy migration will be discussed with reference to the authors' work on in vitro systems.     

IN VIVO CHLOROPHYLL a FLUORESCENCE TRANSIENTS AND THE CIRCADIAN RHYTHM OF PHOTOSYNTHESIS IN GONYAULAX POLYEDRA

Abstract— The intensity of chlorophyll a fluorescence during the early part of fluorescence induction at O , initial fluorescence, and P, peak fluorescence, was higher during the day phase of the circadian cycle than during the night phase in continuous light (LL) conditions and was positively correlated with the rate of oxygen evolution. The circadian rhythm in fluorescence in LL persisted in the presence of 10μM 3–(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), which blocks electron flow from photo-system (PS) II in photosynthesis. The rhythmic changes in fluorescence intensity are consistent with a lower rate constant for radiationless transitions during the day phase than during the night phase of the circadian rhythmicity. The circadian changes in the intensity of fluorescence were abolished at 77K, which may indicate the importance of structural changes in membranes in circadian oscillations.     

POLYPHASIC CHLOROPHYLL a FLUORESCENCE TRANSIENT IN PLANTS AND CYANOBACTERIA*

Abstract— The variable chlorophyll (Chl) a fluorescence yield is known to be related to the photochemical activity of photosystem II (PSII) of oxygen-evolving organisms. The kinetics of the fluorescence rise from the minimum yield, F₀, to the maximum yield, F_m, is a monitor of the accumulation of net reduced primary bound plastoquinone (Q_A) with time in all the PSII centers. Using a shutter-less system (Plant Efficiency Analyzer, Hansatech, UK), which allows data accumulation over several orders of magnitude of time (40 μs to 120 s), we have measured on a logarithmic time scale, for the first time, the complete polyphasic fluorescence rise for a variety of oxygenic plants and cyanobacteria at different light intensities. With increasing light intensity, the fluorescence rise is changed from a typical O-I-P characteristic to curves with two intermediate levels J and I, both of which show saturation at high light intensity but different intensity dependence. Under physiological conditions, Chl a fluorescence transients of all the organisms examined follow the sequence of O-J-I-P. The characteristics of the kinetics with respect to light intensity and temperature suggest that the O-J phase is the photochemical phase, leading to the reduction of Q_A to Q_A^-. The intermediate level I is suggested to be related to a heterogeneity in the filling up of the plastoquinone pool. The P is reached when all the plastoquinone (PQ) molecules are reduced to PQH₂. The addition of 3-(3–4-dichlorophenyl)-1,1-dimethylurea leads to a transformation of the O-J-I-P rise into an O-J rise. The kinetics of O-J-I-P observed here was found to be similar to that of O-I₁-I₂-P, reported by Neubauer and Schreiber (Z. Naturforsch. 42c , 1246–1254, 1987). The biochemical significance of the fluorescence steps O-J-I-P with respect to the filling up of the plastoquinone pool by PSII reactions is discussed.     

X射线荧光光谱法分析玻璃纤维中主、次量元素成分

采用粉末压片-波长色散X射线荧光光谱法分析了中碱及无碱玻璃纤维中硅、铝、钙、镁、铁、钛、钾、钠、砷、氟等10种主、次量元素成分含量。以6个标准样品并结合两个参考样品建立校准曲线,采用DeJongh模式方程有效校正玻璃基体中元素间的吸收增强效应和重叠效应。该方法测定10个元素的精密度和准确度均较好,其相对标准偏差在0．35％～2．86％之间,对实际样品的分析结果与化学法相吻合,可应用于玻璃纤维中多元素成分的快速分析。     

RELATIONS BETWEEN PHOTOCHEMISTRY AND FLUORESCENCE IN CELLS AND EXTRACTS OF PHOTOSYNTHETIC BACTERIA*

Abstract— Light-induced changes in the yield of bacteriochlorophyll fluorescence have been measured in cells and chromatophores of photosynthetic bacteria, and coordinated with light-induced absorbancy changes. Comparisons were drawn during transitions between dark and light steady states and also between steady states established at different light intensities. Aerobic cell suspensions of Rhodospirillum rubrum, Rhodopseudomonas spheroides, Chromatium and Rhodopseudomonas sp. NHTC 133 showed a strict correspondence between changes in the fluorescence yield and the bleaching of P870 (P985 in Rps. sp. NHTC 133), as reported by Vredenberg and Duysens for R. rubrum cells. The relationship shows that singlet excitation energy in bacteriochlorophyll is quenched by P870 at a rate proportional to the concentration of unbleached P870. This implies that the photosynthetic units are not independent with respect to energy transfer. In anaerobic cell suspensions the change in fluorescence did not follow the bleaching of P870 in the manner described by Vredenberg and Duysens. Here a change in fluorescence may have resulted from the reduction of a primary photochemical electron acceptor as well as from the oxidation (bleaching) of P870. In chromatophore preparations there were further deviations from the Vredenberg and Duysens relationship which could be attributed to changes in the rate constants for quenching of singlet excitation energy. Finally there was a light-induced increase in the fluorescence yield which was related to a band shift of bacteriochlorophyll and not to the bleaching of P870. Aerobic cell suspensions presented a limiting case in which these complications were absent. No change in the fluorescence was associated uniquely with the oxidation of cytochrome or band shifts of carotenoid pigments. These results, when coordinated with earlier findings about the fluorescence of bacteriochlorophyll and P870, indicate that the singlet excitation quantum is the only energy carrier linking the absorption of light with the initiation of photochemistry in bacterial photosynthesis.     

ACTION SPECTRA OF PHYTOCHROME IN VIVO*

Abstract— A method is described to determine spectral properties of phytochrome in vivo. For photochrome in 7-day-old dark-grown Cucurbita pepo L. seedlings the mole fraction of the far-red-absorbing form (P_fr) present at photoequilibrium at 664 nm was found to be 0.76 ± 0.02 in vivo. Based on reflectance measurements, the photon fluence rate just below the surface of the cotyledons was calculated. Local rates of photoconversion for known local fluence rates were measured across cotyledons after non-saturating irradiations with wavelengths between 544 and 781 nm and in situ molar photoconversion coefficients were obtained. In contrast to purified oat phytochrome, the in situ molar photoconversion coefficients for P_fr show a strong shoulder between 660 and 700 nm. The maximum of P_fr absorption is at 726 nm. An isosbestic point of phytochrome is found at 686 nm. The mole fraction of P_fr present at photoequilibrium with 686 nm light is 0.58. The ratio of photoconversion quantum yields (that for P_r→ P_fr divided by that for P_fr→ P_r) is 1.38 ± 0.06.     

ICP-AES法测定高温质子导体中的五种元素

研究用ICP-AES法测定高温质子导体中的钡、铈、锶、钇和镱，选定了适宜的溶解方法及分析条件，在溶解酸中加入盐酸羟胺，获得了较为满意的分析结果，相对标准差小于10%。