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21.
New boracites containing nitrato- or fluoroanions that appear to be true low-pressure phases have been synthesized at superatmospheric pressures. The M3B7O13NO3 compounds (M = Co, Ni, Cu, Zn, Cd) transform rapidly and reversibly in the temperature region 300–500°C between probable orthorhombic and face centered cubic symmetry, while the M3B7O13F compounds (M = Mg, Mn, Fe, Co, Zn) appear to maintain rhombohedral symmetry up to their decomposition temperatures of 800–900°C. True high-pressure boracite-like phases containing F and Cr, Mn, Fe, or Co that decompose upon heating to M3B7O13F have also been isolated. 相似文献
22.
23.
With the use of the tritium monitoring network the samples of river water, air humidity and precipitation are collected and analysed for HTO in the vicinity of Temelín nuclear power plant. 相似文献
24.
K.D. Franz H. Tom Dieck U. Krynitz I.W. Renk 《Journal of organometallic chemistry》1973,64(3):361-366
Glyoxal- and diacetyl-bis(imine)metal tetracarbonyls (RNCR′CR′NR)M(CO)4 (M = Cr, Mo, W) are reduced with potassium in DME to give paramagnetic mono-anions. Their high-resolutior, ESR spectra show the hyperfine splittings of the magnetically active ligand atoms as well as the satellites of the metal isotopes 53Cr,95,97Mo and 183W. The coupling constants are discussed with respect to π-bonding mechanisms. 相似文献
25.
The flavonoid composition of broccoli inflorescences has been studied by LC/UV-DAD/ESI-MSn. A large number of hydroxycinnamic acid esters of kaempferol and quercetin glucosides has been characterised. The structures of the flavonoid glycosides were analysed after alkaline hydrolysis, and were identified as 3-sophoroside/sophorotrioside-7-glucoside/sophoroside of kaempferol, quercetin and isorhamnetin (this last found in trace amount). These complex quercetin and isorhamnetin glucosides have not been previously characterised in nature. In addition, several less complex glucosides based on the same aglycones have been identified. The effect of sugar substitution and acylation on chromatographic mobility and ESI ionisation and fragmentation are discussed. 相似文献
26.
A simple, sensitive, selective, fast and inexpensive assay for the determination of diquat is proposed. The method is based on the reduction of the herbicide to a strongly fluorescent monocation radical with sodium dithionite. The initial rate of this reaction is directly proportional to the diquat concentration. The stopped-flow mixing technique was used because the kinetic data can be obtained in only 7 s, meaning that the method can be automated. The calibration graph is linear over the range 5-500 ng ml-1 and the precision (RSD) is close to 1.2%. The applicability of the method was demonstrated by determining the herbicide in different kinds of samples. 相似文献
27.
A.R. László Bursics Martin Murray F. Gordon A. Stone 《Journal of organometallic chemistry》1976,111(1):31-42
Bis(cyclopentadienyl)mercury readily undergoes Diels—Alder reactions with RCCR (R = CO2Me or CF3), CF3CFCFCF3, CF3CFCF2, (CF3)2CC(CN)2, C2(CN)4 and PhO to give stable adducts characterised by1H, 19F and 13C NMR, spectroscopy. Similar reactions of CF3CCCF3 and CF3CFCFCF3 with the cyclopentadiene derivatives Me3MC5H5 and (Me3M)2C5H4 (M = Si, Sn) are also described. 相似文献
28.
Strictly localized or resonance Shockley surface states have been found on the (111), (010) and (110) faces of paramagnetic bcc iron for
,¯M and ¯N points in the corresponding surface Brillouin zones. Energy, character of wave function and its damping for these states are reported. Emphasis is laid on implications of surface states in photoemission, field-electron and -ion emission, electron energy-loss or disappearance potential spectroscopy, Auger electron spectroscopy, work function, magnetic properties, electric conductivity, as well as chemisorption and catalysis. 相似文献
29.
Doug Bruce John Biggins Tom Steiner Mike Thewalt 《Photochemistry and photobiology》1986,44(4):519-525
Excitation spectra of chlorophyll- a (Chl- a ) fluorescence in intact cells of Cryptomonas ovata, Chroomonas pauciplastida and Chroomonas salina were determined at 77 K. For all species the excitation spectra for emission from Chl- a associated with photosystem II (PSII) showed increased contributions by a carotenoid (493 nm) and phycobiliproteins, and decreased contributions by carotenoid (417 nm, 505 nm) and Chl- a (445 nm) as compared to excitation spectra for emission from Chl- a associated with photosystem I (PSI). Excitation spectra of C. salina and C. ovata showed an increased contribution by Chl- c 2 to PSII Chl- a fluorescence emission. In all three species the absorbance band positions of Chl- a , as determined from the excitation spectra, were similar to those previously described in green plants. green algae and phycobilisome-containing organisms. Time-resolved 77 K fluorescence emission spectra of C. ovata and C. salina showed successive emission from both phycoerythrin and Chl- c 2 , PSII Chl- a , and PSI Chl- a. C. pauciplastida showed successive emission from phycocyanin, PSII Chl- a , and PSI Chl- a. Spectral red-shifts with time were observed for the phycobiliprotein peaks in all three species. The fluorescence decay of phycoerythrin in C. ovata and C. salina was faster than that of phycocyanin in C. pauciplastida. The results are discussed in relation to the organization of the antenna pigments of PSII and PSI in the cryptophyte algae. 相似文献
30.
The nuclear magnetic moment of103Ru has been determined using the technique of low-temperature nuclear orientation on103Ru as a dilute impurity in Fe. The Fe lattice was cooled to 1.7 mK using a PrNi5 enhanced nuclear demagnetisation stage precooled with a3He–4He dilution refrigerator. The103RuFe system was observed to have a long nuclear spin-lattice relaxation time, but analysis of the relaxation indicates that the103Ru nuclei are close to thermal equilibrium with the Fe lattice at times>200 min after demagnetising. From the near thermal equilibrium anisotropy of the 497 keV -ray in103Rh we have deduced the nuclear magnetic moment as |(103Ru)|=0.18(2)N. This value is almost independent of the choice of spinI=3/2 or 5/2 for the nucleus, but is only consistent with systematics ifI(103Ru)=3/2 and <0. UsingI=3/2 we obtain the E2/M1 mixing ratio of the 497 keV -ray as =–0.42(4). The sign of the anisotropy of the 610 keV -ray from the 650 keV level in103Rh is only consistent with an allowed -decay to the state ifI(650 keV,103Rh)=5/2. The E2/M1 mixing ratio of the 610 keV -ray is then =+0.15(3) or +60(
–40
+
), <–80. From the initial rise in -ray anisotropy following demagnetisation we determine the Korringa constant for103RuFe to beC=5.7(5) K·s. 相似文献