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1.
The oxidation of Fe(OH)2 in the presence of Cl– or CO
3
2–
ions leads, in the first stage of the reaction, to chloride-containing green rust one (GR1), 3Fe(OH)2· Fe(OH)2Cl·nH2O, or carbonate-containing GR1, 4Fe(OH)2·Fe2(OH)4CO3·nH2O, respectively. These GR1 compounds give the ferric oxyhydroxides by further oxidation. If a hydroxide Ni
x
Fe1–x
(OH)2 is initially precipitated, the reaction leads to a nickelous-ferric compound isomorphous to the ferrous-ferric GR1, but stable with respect to the oxidizing action of air. Similarly, the oxidation of a nickelous-ferrous hydroxide, in the presence of excess OH– ions, leads to a nickelous-ferric GR1, a layered hydroxide with anionic interlayers made of OH– ions and water molecules. The Mössbauer spectra of these nickelousferric GR1 display two ferric doublets, D0 withIS=0.34 mm/s andQS=0.45 mm/s and D1 withIS=0.36 mm/s andQS=0.86 mm/s. The existence of a ferrous-ferric GR1 incorporating OH– ions, a compound never observed so far, is strongly suspected. 相似文献
2.
Lecomte and Ovsienko constructed SL
n+1(R)-equivariant quantization maps Q for symbols of differential operators on -densities on RP
n
. We derive some formulas for the associated graded equivariant star products on the symbol algebra Pol(T* RP
n
). These give some measure of the failure of locality. Our main result expresses (for n odd) the coefficients C
p
(·,·) of when =
in terms of some new SL
n+1(C)-invariant algebraic bidifferential operators Z
p
(·,·) on T* CP
n
and the operators (E + n/2 ± s)–1 where E is the fiberwise Euler vector field and s {1, 2, ..., [p/2]}. 相似文献
3.
M. Smi?anská J. Hladky M. Novák M. Vecko A. N. Aleev V. A. Arefiev V. P. Balandin V. K. Berdyshev V. K. Birulev A. S. Chvyrov et al. 《Czechoslovak Journal of Physics》1990,40(12):1293-1305
We present results of the exclusive diffractive reaction np 0K0p at 0·08 < |t|< 0·53 GeV2/c2 and momenta between 30–70 GeV/c at the Serpukhov neutron beam. Thet-dependence is exp (Bt) withB= 11·4± 2·3 (GeV/c)–2 and it exhibits the diffractive minimum at ¦t¦ 0·28 GeV2/c2 for 0K0 massesM < 1·8 GeV/c2.B decreases with increasingM. Correlation with the beam direction is observed in the rest frame of the 0K0 system: the cross section rises for the forward-going 0. The rise is more pronounced for higherM. The cross section of reaction np 0K0p for 0<|t|< 0·53 GeV2/c2 is 10·3 ± 2·5 ± 2·8 b. 相似文献
4.
Green rust-like compounds (GRs) were discovered as natural minerals in various hydromorphic soils, where anoxic conditions allow their stability. They may control some redox processes in aquifers and participate to the transformation of various pollutants. Since Mg(II) cations are present in the fields where GRs were discovered, a partial substitution of Mg(II) to Fe(II) leading to intermediate compounds between GRs and usual Mg(II)–Fe(III) hydroxysalts is suspected. Mg(II)–Fe(II)–Fe(II) hydroxycarbonates can be obtained as intermediate oxidation products of (Mg, Fe)(OH)2 in carbonate-containing aqueous media obeying to [FeII
4(1–x)MgII
4x
FeIII
2(OH)12]2+
[CO3
2–
nH2O]–2. TMS spectra at 12 K are similar to those of GRs, i.e., two quadrupole doublets, one due to Fe(II) with a large isomer shift =1.29 mms–1 (with respect to -iron at room temperature) and quadrupole splitting E
Q=2.76 mms–1, the other one due to Fe(III) with smaller hyperfine parameters =0.49 mms–1 and E
Q=0.44 mms–1. Fe(II) ions oxidise rapidly into Fe(III) with dissolved O2. The reactivity is similar to that of Fe(II)–Fe(III) hydroxysalts GR, and thus the potential of Mg(II)–Fe(II)–Fe(III) compounds for reducing pollutants. 相似文献
5.
Peter Wardman Mark J. Burkitt Kantilal B. Patel Andrew Lawrence Clare M. Jones Steven A. Everett Borivoj Vojnovic 《Journal of fluorescence》2002,12(1):65-68
Lucigenin (LC2+, bis-N-methylacridinium) and 2,7-dichlorofluorescin (DCFH2) are widely used as chemiluminescent or fluorescent probes for cellular oxidative stress, to reflect levels of superoxide (O2
·–) and hydrogen peroxide, respectively. We report mechanistic studies that add to the growing evidence for the unsuitability of either probe except in very well-defined circumstances. The ability for lucigenin to generate superoxide via reduction of LC2+ to LC·+ and redox cycling with oxygen depends on the reduction potential of the LC2+/LC·+ couple. Redox equilibrium between LC·+ and the redox indicator benzyl viologen is established in microseconds after generation of the radicals by pulse radiolysis and indicated E(LC2+/LC·+) –0.28 V vs. NHE. Reaction of LC·+ with O2 to generate O2
·– was also observed directly similarly, occurring in milliseconds, with a rate constant k 3 × 106
M
–1 s–1. Quinones act as redox mediators in LC·+/O2 redox cycling. Oxidation of DCFH2 to fluorescent DCF is not achieved by O2
·– or H2O2, but NO2
·) reacts rapidly: k 1 × 107
M
–1 s–1. Oxidation by H2O2 requires a catalyst: cytochrome c (released into the cytosol in apoptosis) is very effective (even 10 nM). Fluorescence reflects catalyst level as much as O2
·–) production. 相似文献
6.
Results of measurement between 746 and 1231 C of the diffusion coefficient Fe-59 in the Fe-17·6 at.% V alloy, together with Mirani's et al., Lai-Borg's and Hettich's et al. data analysis, are presented. All the data show a marked ferromagnetic effect, i.e. the lnD(T) values measured at the temperaturesT< are distinctly lower than those extrapolated by the linear Arrhenius plot from the paramagnetic range. The results are interpreted in terms of the Heisenberg model, Kirkwood's and Girifalco's statistical theories. The computer fit of an analytical form, derived for the excess activation enthalpyH(T), to experimental data enabled us to calculate the values of the exchange integralJ
0 and the paramagnetic temperatureT
p. The corresponding values for the Fe-17·6% V alloy are:J
0=(315±11)k,k is the Boltzmann constant, andT
p=(1223±±18) K. The activation enthalpy of Fe self-diffusion in a completely ordered ferromagnetic Fe-17·6% V matrix is higher by the value ofH(0)=(55·2±1·9)kJ/mol than the value 236·35 kJ/mol corresponding to a fully paramagnetic state. Applying a three paramagnetic fit to Mirani's, Lai-Borg's and Hettichs data, we have found that the ratio of the vacancy migration enthalpy and of the formation enthalpy in -Fe, in Fe-17·6% and Fe-7·64% Si, may be expressed by the valueH
M/H
F=1·62 ± 0·18. A comparison ofJ
0(-Fe) toJ
0(17·6 %V) and toJ
0(7·64% Si) shows that the magnetic dilution caused by 17·6% of vanadium is negligible withJ
0(17·6% V)/ /J
0(-Fe)=0·999. The dilution brought about by silicium is by about 1·24 times higher, and the ratioJ
0(7·64% Si)/J
0(-Fe)=0·86. The paramagnetic temperatures in the materials under study are given by the relationT
P=(gQ + 137) K, being the respective Curie-temperature. The present analysis makes it possible to calculate the Fe diffusion characteristicsD
0f aH
f in a fully ordered magnetic matrix. 相似文献
7.
J. Lindén T. Karlemo M. Karppinen T. Katila M. Lippmaa A. Nara L. Niinistö I. Tittonen K. Ullakko H. Yamauchi 《Hyperfine Interactions》1994,93(1):1635-1639
The rare-earth site of samples having the compositions (Fe,Cu)Sr2(Eu,Ce)
n
Cu2O4+2n+z (n=2 and 3) were studied by151Eu Mössbauer spectroscopy. The results obtained are compared with measurements of EuBa2Cu3O7– (123) and Bi2Sr2(Ca1–yEuy)Cu2O8+E
(2212) samples. The full quadrupole Hamiltonian of the 21.5-keV -transition was applied in analyzing the measured spectra. Simultaneous fitting of spectra recorded from crystallites oriented in various directions was used to determine the hyperfine parameters of then= 2 and 3 samples. Two different electric field gradients, not discernible in simple random crystallite measurements, were obtained for then=3 series. 相似文献
8.
George Svetlichny 《Foundations of Physics》1986,16(12):1285-1295
LetA be a quasi-manual with finite operations. Associate to each E = {e
1
,..., en} A the set E of modal formulas: (e
1
··· en), ei (e
1
··· ei–1
ei+1
··· en), i=1,..., n. Set
A
= {E|E A}. We show that supports ofA are in one-to-one correspondence with certain Kripke models of
A
where the supports are given by {x |A x is true}.On leave from the Department of Mathematics, Pontificia Universidade Catolica, Rio de Janeiro, Brazil. 相似文献
9.
X. -Q. Ding E. L. Bominaar E. Bill H. Winkler A. X. Trautwein S. Drüeke PH. Chaudhuri K. Wieghardt 《Hyperfine Interactions》1990,53(1-4):311-315
In this paper, we briefly summarize the main conclusions of the Mössbauer analysis of [L2Fe2(-OH)3] (ClO4)2·2CH3OH·2H2O with L=N,N',N"-trimethyl-1,4,7-triazacyclononane, a novel dimeric iron compound, which possesses a central exchange-coupled delocalized-valence Fe(II/III) unit. The complete delocalization of the excess electron in the dimeric iron center is concluded from the indistinguishability of the two iron sites in Mössbauer spectroscopy. The magnetic Mössbauer spectra imply a system spinS
t=9/2 for the dimer in its ground state. The values for hyperfine and spin-Hamiltonian parameters, obtained from simulations of the Mössbauer spectra, are =0.74 mms–1, E
Q=–2.14 mms–1,A
=–10.6 T,A
=–13.5 T andD=1.8 cm–1. The system spinS
t=9/2 is interpreted to be a consequence of double-exchange coupling. 相似文献
10.
O. Čermáková 《Czechoslovak Journal of Physics》1986,36(9):1058-1062
This contribution presents birefringence spectra for orthorhombic YAlO3Ce single crystal in the region 2–5 eV. The spectra were measured by means of a reflection method of null ellipsometry and were compared with spectra of YAlO3:Nd determined from values measured in the region of lower energies (1·1–2·2 eV). We have found that there are differences between the spectra of YAlO3Nd and YAlO3:Ce which are most pronounced in thea-axis direction.The author is most grateful to Ing. . Viovský CSc. for helpful discussions during the course of this work and to Monokrystaly Turnov for preparation of the samples. 相似文献
11.
Y. Hayasi 《Zeitschrift für Physik B Condensed Matter》1978,32(1):67-73
Using a focussing crystal spectrometer with photoelectric registration theK-emission spectrum of fluorine in solid lithium fluoride (=18.3 Å) was studied. If the spectrum is excited by Co or CuL-radiation or bremsstrahlung of a W-target the satellitesK
3 andK
4 appear with considerable intensity, whereas they appear only faintly ifL-radiation of Fe is used for excitation. In agreement with these observations the calculated threshold energies of the satellites are near the photon energy of FeL
1, 2. The measured energies of the components agree with values obtained from the energies of the singly and doubly ionized F– ion as calculated by means of optical data. The results show that the satellitesK
3 andK
4 in the spectrum of fluorine in solid LiF correspond to transitions in the doubly ionized F–-ion. 相似文献
12.
M. S. Sakr A. A. El-Shazly M. M. Mostafa H. A. El-Sayed A. A. Mohamed 《Czechoslovak Journal of Physics》1988,38(11):1255-1259
Transient creep of Cd-2 wt. % Zn and Cd-17·4 wt. % Zn alloys has been studied under different constant stresses ranging from 6·4 MPa to 12·7 MPa near the transformation temperature. The results of both compositions showed two transient deformation regions, the low temperature region (below 483 K) and the high temperature region (above 483 K). From the transient creep described by the equation
tr=Bt
n, where
tr andt are the transient creep strain and time. The parametersB andn were calculated. The parameterB was found to change with the applied stress from 0·3×10–4 to 3×10–4 and from 0·6×10–4 to 18×10–4 for Cd-2 wt. % Zn and Cd-17·4 wt. % Zn, respectively. The exponentn was found to change from 0·8 to 0·95 for both alloys. The parameterB was related to the steady state creep rate
through the equation
, the exponent was found to be 0·5 for Cd-2 wt. % Zn and 0·6 for the eutectic composition. The activation energies of transient creep in the vicinity of the transformation regions (above 483 K) were found to be 50·2 kJ/mole for Cd-2 wt. % Zn and 104·7 kJ/mole for the eutectic composition characterizing the mechanisms of grain boundary diffusion and volume diffusion in Cd, respectively. 相似文献
13.
We present the application of a continuous-wave ultra-violet tuneable light source for detection of the hydroxyl radical (OH) using cavity-enhanced absorption spectroscopy of the Q11(2) and Q21(2) absorption lines in the A2+(v=0)23/2(v=0) band at ca. 308 nm. A tuneable infra-red diode laser operating at 835 nm and either an Ar+ laser or a single frequency continuous-wave intracavity frequency-doubled diode laser, both operating at ca. 488 nm, were used to produce 0.1–0.5 W of tuneable radiation at ca. 308 nm by sum frequency generation in a BaB2O4 crystal. Cavity enhanced absorption spectroscopy was used to detect OH generated by UV photolysis of water vapour in argon, nitrogen, neon and helium at atmospheric pressure. A noise-equivalent (1) absorption sensitivity of 2.1×10-7 cm-1Hz-1/2 measured over 128 scans in a time of 1.16 s was demonstrated with mirrors of reflectivity 0.9963 in a cavity of length 58.5 cm for a 2 cm-1 scanning range at a UV power of 0.5 W. An OH detection limit (1) of 3.84×109 moleculecm-3 was estimated in argon at atmospheric pressure. OH collisional broadening in humidified N2, Ar, Ne and He was determined at atmospheric pressure . PACS 39.30.+w; 42.55.Px; 42.62.Fi; 42.68.Ca 相似文献
14.
Microbial Reduction of Lepidocrocite γ-FeOOH by Shewanella putrefaciens; The Formation of Green Rust
Ona-Nguema G. Abdelmoula M. Jorand F. Benali O. Géhin A. Block J.-C. Génin J.-M. R. 《Hyperfine Interactions》2002,139(1-4):231-237
Dissimilatory iron-reducing bacteria (DIRB) couple the oxidation of organic matter or H2 to the reduction of iron oxides. The bacterial reduction of a most common well-crystallised ferric oxyhydroxide, -FeOOH was investigated using DIRB Shewanella putrefaciens, strain CIP 8040. Experiments were conducted in the presence of neither organic buffer nor phosphate, with formate as electron donor, bicarbonate, and anthraquinone-2,6-disulfonate (AQDS, a humic acid analogue) that influenced the extent of ferric oxide bioreduction. The production of Fe2+ was followed with time. The solid phases obtained after bacterial iron reduction were analysed by transmission Mössbauer spectroscopy (TMS) and X-ray diffraction (XRD). Biogenic formation of green rust 1 compound, which contains carbonate anions, [FeII
2FeIII
2(OH)8]2+[CO3
2–]2– was observed. TMS was used to follow the evolution of the green rust abundance during the bacterial culture. 相似文献
15.
The experimental results obtained with the chalcogenide glass Ge15Te81S2As2 with imposed overall pressure up to 700 MPa are presented. The material exhibits the switching effect and the memory effect. It is shown that the overall pressure changes remarkably d.c. electrical conductivity of the amorphous semiconductor. It is assumed that the changes in conductivity are caused by changes in activation energy. The changes in activation energy within the range of considered pressures are, as follows from our measurements, E/p–10·95×10–5 eV/MPa +p × 10·41 W 10–7 eV/MPa2. The assumption of the activation energy dependence on pressurep are confirmed also by measurements of dependence In vs. 1/T at various pressures. 相似文献
16.
Ground state energies of doubly even nuclei which are assumed to be composed of rigid and structureless alpha-particles are calculated. The alpha-particles are assumed to be interacting through a potential composed of a hard core followed by a square well potential in one set of calculations and a Gaussian potential in another set of calculations. Our calculations support the existence of the hard core in the alpha-alpha potential, and suggest the existence of the alphaclustering in doubly even light nuclei.From the graph betweenE
0/N and we find thatE
0/N is minimum at =2·57×1037 particles cm–3. This means that in the surface region an assembly of alpha-particles with = = 2·57×1037 particles cm–3 is the most stable one.We are greatly indebted to Professors R. Tamagaki, M. Harada and F. Iwamote for making very useful suggestions and for making a few points clear to us. Thanks are also due to Professors P. C. Sood, S. Duttamazumdar and M. K. Pal for many helpful discussinos, and to the Indian National Science Academy, New Delhi for giving financial assistance. Thanks are also due to Shri A. N. Phukan for drawing the graphs. 相似文献
17.
H. J. Heinze H. Micklitz F. J. Litterst E. Baggio-Saitovitch V. Moshchalkov L. Leonjuk 《Zeitschrift für Physik B Condensed Matter》1993,91(2):139-143
57Fe Mössbauer effect measurements have been performed on single crystals of57Fe doped GdBa2Cu3O7- at various c-axis orientations and temperatures. The analysis of the data yields information on the sign and direction of Vzz, the direction of Bhf with respect to Vzz and the anisotropy of the f-factor for the individual observed three quadrupole doublets. From these data we conclude that the quadrupole doublet with EQ 1.9 mm/s is due to Fe on a regular Cu(1)-site (4-fold oxygen coordination) with distorted local symmetry (Vzz isnot parallel to the c-axis), while the other quadrupole doublets have higher oxygen coordinations (higher Lamb-Mössbauer-factor). 相似文献
18.
E. Hiyama 《Few-Body Systems》2004,34(1-3):79-84
From the viewpoint of critical stability, we discuss the three- and four-body structure of 6He, 7He, 4He, and 4H. With the + + N three-body model, 6He is found to have a three-layer structure of the matter distribution: core, a skin and neutron halo. Also the level structure of 7He with the three-body model of 5He + n + n is predicted. This stimulates a new study of neutron-rich and proton-rich hypernuclei. By performing a four-body calculation with both NNN and NNN channels and with both NN and NNN channels, we show that the N-N and -N couplings are very important in critical stability of few-body hypernuclear systems. 相似文献
19.
The conversion coefficient
K=1·48±0·07 and the total conversion coefficient = =8·05±0·2 have been determined by means of the 4 scintillation counter.The authors are obliged to Mrs.Boukalov, Mrs.Vladykov and MissStíteská for the assistance in the elaboration of this paper. 相似文献
20.
M. B. Kotlyarevskii A. N. Georgobiani I. V. Rogozin A. V. Marakhovskii 《Journal of Applied Spectroscopy》2003,70(1):95-98
Using a unique method of radical-beam heteroepitaxy (RBHE) based on annealing of the crystals of the II–VI (ZnSe) compounds in a flow of radicals of a metalloid component — oxygen O — ZnO layers with a superstoichiometric content of oxygen were obtained. The conductivity of the layers = 102 ·cm, the mobility of the holes = 23 cm2/V·sec, and the concentration N
A = 1015 cm–3. The luminescence spectra of pure ZnO single crystals and those doped with Li and Na, both treated by the RBHE method, are studied at helium temperatures. The luminescence centers associated with the intrinsic defects (V
Zn) are identified. 相似文献