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1.
To evaluate the contribution of local pulsed heating of light-absorbing microregions to biochemical activity, irradiation of Escherichia coli was carried out using femtosecond laser pulses (λ = 620 nm, τp=3 × 10−13 s, fp = 0.5 Hz, Ep = 1.1 × 10−3J cm−2, Iav = 5.5 × 10−4 W cm−2, Ip = 109 W cm−2) and continuous wave (CW) laser radiation (λ = 632.8 nm, I = 1.3 W cm−2). The irradiation dose required to produce a similar biological effect (a 160%–190% increase in the clonogenic activity of the irradiated cells compared with the non-irradiated controls) is a factor of about 103 lower for pulsed radiation than for CW radiation (3.3 × 10−1 and 7.8 × 102 J cm−2 respectively). The minimum size of the microregions transiently heated on irradiation with femtosecond laser pulses is estimated to be about 10 Å, which corresponds to the size of the chromophores of hypothetical primary photoacceptors—respiratory chain components.  相似文献   

2.
We have successfully synthesized a high-purity polycrystalline sample of tetragonal Li7La3Zr2O12. Single crystals have been also grown by a flux method. The single-crystal X-ray diffraction analysis verifies that tetragonal Li7La3Zr2O12 has the garnet-related type structure with a space group of I41/acd (no. 142). The lattice constants are a=13.134(4) Å and c=12.663(8) Å. The garnet-type framework structure is composed of two types of dodecahedral LaO8 and octahedral ZrO6. Li atoms occupy three crystallographic sites in the interstices of this framework structure, where Li(1), Li(2), and Li(3) atoms are located at the tetrahedral 8a site and the distorted octahedral 16f and 32g sites, respectively. The structure is also investigated by the Rietveld method with X-ray and neutron powder diffraction data. These diffraction patterns are identified as the tetragonal Li7La3Zr2O12 structure determined from the single-crystal data. The present tetragonal Li7La3Zr2O12 sample exhibits a bulk Li-ion conductivity of σb=1.63×10−6 S cm−1 and grain-boundary Li-ion conductivity of σgb=5.59×10−7 S cm−1 at 300 K. The activation energy is estimated to be Ea=0.54 eV in the temperature range of 300–560 K.  相似文献   

3.
D.F. Zhou  Y.J. Xia  J.X. Zhu  J. Meng   《Solid State Sciences》2009,11(9):1587-1591
Ce6−xDyxMoO15−δ (0.0 ≤ x ≤ 1.8) were synthesized by modified sol–gel method. Structural and electrical properties were investigated by means of X-ray diffraction (XRD), Raman, X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS). The XRD patterns showed that the materials were single phase with a cubic fluorite structure. Impedance spectroscopy measurement in the temperature range between 350 °C and 800 °C indicated a sharp increase in conductivity for the system containing small amount of Dy2O3. The Ce5.6Dy0.4MoO15−δ detected to be the best conducting phase with the highest conductivity (σt = 8.93 × 10−3 S cm−1) is higher than that of Ce5.6Sm0.4MoO15−δ (σt = 2.93 × 10−3 S cm−1) at 800 °C, and the corresponding activation energy of Ce5.6Dy0.4MoO15−δ (0.994 eV) is lower than that of Ce5.6Sm0.4MoO15−δ (1.002 eV).  相似文献   

4.
The structure of Ni0.85Mo6Te8 was refined from single-crystal X-ray diffraction data at room temperature. It is triclinic, space group
; 1619 reflections, 75 refined parameters, R = 0.031. The Mo atoms form distorted octahedral clusters (2.69 Å ≤ dintra[Mo---Mo] ≤ 2.81 Å; 3.58 Å < dinter[Mo---Mo]). The Ni atoms are disordered (site occupancy: 0.423(7); d[Ni---Ni] = 2.586(6) Å), and interact strongly with one Mo6 cluster (d[Ni---Mo] = 2.603(3) and 2.958(3) Å), and weakly with another (d[Ni---Mo] = 2.985(3) Å). The structure transforms at 1057(5) K into a rhombohedral modification (ahex = 10.457(2) Å, chex = 11.866(3) Å at 1073 K). Measurements on powders suggest metallic conductivity (5.1 × 10−4 Ω-cm at 293 K) and weakly temperature-dependent paramagnetism (110 × 10−6 emu/g at 100 K).  相似文献   

5.
The kinetics of the reaction of the CH3CHBr, CHBr2 or CDBr2 radicals, R, with HBr have been investigated in a temperature-controlled tubular reactor coupled to a photoionization mass spectrometer. The CH3CHBr (or CHBr2 or CDBr2) radical was produced homogeneously in the reactor by a pulsed 248 nm exciplex laser photolysis of CH3CHBr2 (or CHBr3 or CDBr3). The decay of R was monitored as a function of HBr concentration under pseudo-first-order conditions to determine the rate constants as a function of temperature. The reactions were studied separately from 253 to 344 K (CH3CHBr + HBr) and from 288 to 477 K (CHBr2 + HBr) and in these temperature ranges the rate constants determined were fitted to an Arrhenius expression (error limits stated are 1σ + Student’s t values, units in cm3 molecule−1 s−1, no error limits for the third reaction): k(CH3CHBr + HBr) = (1.7 ± 1.2) × 10−13 exp[+ (5.1 ± 1.9) kJ mol−1/RT], k(CHBr2 + HBr) = (2.5 ± 1.2) × 10−13 exp[−(4.04 ± 1.14) kJ mol−1/RT] and k(CDBr2 + HBr) = 1.6 × 10−13 exp(−2.1 kJ mol−1/RT). The energy barriers of the reverse reactions were taken from the literature. The enthalpy of formation values of the CH3CHBr and CHBr2 radicals and an experimental entropy value at 298 K for the CH3CHBr radical were obtained using a second-law method. The result for the entropy value for the CH3CHBr radical is 305 ± 9 J K−1 mol−1. The results for the enthalpy of formation values at 298 K are (in kJ mol−1): 133.4 ± 3.4 (CH3CHBr) and 199.1 ± 2.7 (CHBr2), and for α-C–H bond dissociation energies of analogous compounds are (in kJ mol−1): 415.0 ± 2.7 (CH3CH2Br) and 412.6 ± 2.7 (CH2Br2), respectively.  相似文献   

6.
The diffusion of strontium and zirconium in single crystal BaTiO3 was investigated in air at temperatures between 1000 °C and 1250 °C. Thin films of SrTiO3, deposited by spin coating a precursor solution and thin films of zirconium, deposited onto the sample surfaces by sputtering, were used as diffusion sources. The diffusion profiles were measured by SIMS depth profiling on a time-of-flight secondary ion mass spectrometer (ToF-SIMS). The diffusion coefficients of strontium and zirconium were given by DSr = 3.6 × 102.0±4.4 exp[−(543 ± 117) kJ mol−1/(RT)] cm2 s−1 and DZr = 1.1 × 101.0±2.1 exp[−(489 ± 56) kJ mol−1/(RT)] cm2 s−1. The results are discussed in terms of different diffusion mechanisms in the perovskite structure of BaTiO3.  相似文献   

7.
[C4H9)4N]2[Mo2O7] reacts with a variety of organic species containing α-diketone groups to give tetranuclear complexes of general composition [RMo4O15X]3−. The complexes [(C4H9)4N]3[(C9H4O)Mo4O15(OCH3)] (I), [(C4H9)4N]3[(C14H10)Mo4O15(C6H5CO2)] (11) and [(C4H9)4N]3[(C14H8)Mo4O15(OH)] (III) were synthesized from the reactions of dimolybdate with ninhydrin, benzil and phenanthraquinone, respectively. Complex II may also be prepared from dimolybdate and benzoin in acetonitrile-methanol solution, from which it co-crystallizes with the binuclear species [(C4H9)4N]2[Mo2O5(C6H5C(O)C(O)C6H5)2] · CH3CN · CH3OH (IV). Complexes I–III exhibit the tetranuclear core, previously described for the α-glyoxal derivatives [(C4H9)4N]3[(HCCH)Mo4O15X], where X = F or HCO2. The ligands may be formally described as diketals, formed by insertion of ligand carbonyl subunits into molybdenum-oxygen bonds. The structures I–III differ most dramatically in the identity and coordination mode of the anionic ligand X which occupies a position opposite the diketal moiety relative to the [Mo4O11]2+ central cage. Thus, I exhibits a doubly bridging methoxy group in this position, while II possesses a benzoate ligand with an unusual μ3-O,O′coordination mode. Complex III presents a hydroxy-group unsymmetrically bonded to three of the molybdenum centres. The stereochemical consequences of the various coordination modes are discussed. Crystal data: Compound I, monoclinic space group Pc, a = 24.888(2), b = 12.897(3), c = 24.900(3) Å, β = 101.94(2)°, Dcalc = 1.28 g cm−1 for Z = 4. Structure solution and refinement based on 8695 reflections with Fo 6σ(Fo) (Mo-Kα, λ = 0.71073 Å) converged at a conventional discrepancy factor of 0.060. Compound II, orthorhombic space group Pbca, a = 20.426(6), b = 26.916(6), c = 32.147(7) Å, V = 17673.2(20) Å3, Dcalc = 1.33 g cm−3 for Z = 8; 5224 reflections, R = 0.076. Compound III, tetragonal space group I41/a, a = b = 48.129(6), c = 13.057(2) Å, V = 30246.2(12) Å3, Dcalc = 1.35 g cm−3 for Z = 16; 5554 reflections, R = 0.053. Compound IV, orthorhombic space group Pnca, a = 16.097(4), b = 16.755(4), c = 25.986(7) Å, V = 7008.1(13) Å3, Z = 4, Dcalc = 1.18 g cm−3 ; 2944 reflections, R = 0.061.  相似文献   

8.
EPR studies are carried out on Cr3+ ions doped in d-gluconic acid monohydrate (C6H12O7·H2O) single crystals at 77 K. From the observed EPR spectra, the spin Hamiltonian parameters g, |D| and |E| are measured to be 1.9919, 349 (×10−4) cm−1 and 113 (×10−4) cm−1, respectively. The optical absorption of the crystal is also studied at room temperature. From the observed band positions, the cubic crystal field splitting parameter Dq (2052 cm−1) and the Racah interelectronic repulsion parameter B (653 cm−1) are evaluated. From the correlation of EPR and optical data the nature of bonding of Cr3+ ion with its ligands is discussed.  相似文献   

9.
Using spectrophotometric methods, the protopysis constant of the 5.ClDMPAP reagent (pKa1 = −0.19; pKa2 = 1.97; pKa3 = 11.98) and the stability constant of its vanadic complex (6.0 ± 0.11) × 1014 were determined. A high-sensitivity spectrophotometric method was developed to determine V(V) using 0.1–1.2 ppm and pH = 3.8. ε586 = 55,300 ± 400 liters · mol−1 · cm−1. A study on the most important interferences and the way to eliminate them was carried out. The method can be applied to the determination of the element in steels and ferrovanadiums.  相似文献   

10.
Isostructural heterotrinuclear complexes (C5H5CrSCMe3)2S · M(CO)5 (II–IV) were isolated from photochemical reactions between the antiferromagnetic complex (C5H5CrSCMe3)2S (I) (with the Cr---Cr bond 2.689 Å long and with the exchange parameter −2J = 430 cm−1) and metal hexacarbonyls, M(CO)6, where M is Cr, Mo, or W. According to the X-ray structural data on III and IV, complex I plays the role of an unusual antiferromagnetic ligand L bound to M through the sulphide bridge (M–S 2.58(2) Å). Its geometry remains practically unaffected by the complex formation (the Cr---Cr bond length in III and IV is 2.73(1) Å). The exchange parameter, −2J (410, 440 and 440 cm−1 in II to IV, respectively), also shifts only insignificantly from that of I, which probably means that indirect exchange via the sulphide bridge in I is of minor importance compared with the direct Cr---Cr exchange. The Cr---Cr bond length may thus be correlated with the observed overall exchange coupling.  相似文献   

11.
The crystal structure of Y2SrFeCuO6.5 was determined from single-crystal X-ray and neutron powder diffraction studies. Mr = 488.81, orthorhombic, Ibam, a = 5.4036(8)[5.4149(1)] Å, b = 10.702(1)[10.7244(1)] Å, c = 20.250(2)[20.2799(2)] Å; values in square brackets are neutron data. V = 1171.0(4), Z = 8, Dx = 5.544 g cm−3, λ = 0.71069 Å, μ = 345.1 cm−1, R = 0.048 for 567 observed reflections. The Fe/Cu atoms occupy randomly the approximate center of oxygen pyramids. The pyramids share the apical oxygen and articulate laterally by corner sharing of oxygen to form a double pyramidal layer perpendicular to c. The pyramidal slabs are separated by double layers of Y that are in 7-fold coordination to oxygen, forming a defect fluorite unit. Mössbauer spectra indicate a unique iron environment and magnetic ordering at about 265 K. The paramagnetic phase coexists with the magnetic phase over an approximate temperature range 300-263 K, characteristic of magnetic ordering in 2-D magnetic structures. The isomer shift, 0.26, and quadrupole splitting, 0.56 mm sec−1, are consistent with Fe3+ in 5-fold coordination and Hint values also indicate classic high spin Fe3+. The average Y---O bond length is 2.331(6) Å and Sr is in a dodecahedral environment in which, however, two oxygen atoms at the corners of the cube are missing. The average Sr---O bond length is 2.793(10) Å. The structure is derived from the Ruddlesden-Popper phase Srn+1TinO3n+1 with n = 2.  相似文献   

12.
A sensitive spectrophotometric method for the determination of copper(II) based on a ternary complex with chromal blue G, a triphenylmethane reagent in the presence of cetyltrimethylammonium chloride, is described. The sensitivity of color reaction between copper and chromal blue G has been greatly increased by the sensitizing action of cetyltrimethylammonium chloride, a cationic surfactant. The color development of the ternary complex can be utilized in the highly sensitive spectrophotometric determination of copper. The molar absorptivity of the binary complex between copper and chromal blue G ε630nm = 9.56 × 103liters · mol−1 · cm−1 is enchanced on ternary complex formation to ε542 nm = 4.78 × 104liters · mol−1 · cm−1. The ternary complex gave a maximal absorbance at 542 nm in the pH range 9.8–11. Beer's law is obeyed up to at least 1.2 ppm of copper. The maximal absorbance of the ternary complex was found to develop within 5 min and then it remains constant for several hours. The formation constant of the ternary complex is calculated to be 8.6 × 1010 under these conditions.  相似文献   

13.
Pulse radiolysis transient UV–visible absorption spectroscopy was used to study the UV–visible absorption spectrum (225–575 nm) of the phenyl radical, C6H5(), and kinetics of its reaction with NO. Phenyl radicals have a strong broad featureless absorption in the region of 225–340 nm. In the presence of NO phenyl radicals are converted into nitrosobenzene. The phenyl radical spectrum was measured relative to that of nitrosobenzene. Based upon σ(C6H5NO)270 nm=3.82×10−17 cm2 molecule−1 we derive an absorption cross-section for phenyl radicals at 250 nm, σ(C6H5())250 nm=(2.75±0.58)×10−17 cm2 molecule−1. At 295 K in 200–1000 mbar of Ar diluent k(C6H5()+NO)=(2.09±0.15)×10−11 cm3 molecule−1 s−1.  相似文献   

14.
The crystal structure of K2Cu3(As2O6)2 was determined from single-crystal X-ray data by a direct method strategy and Fourier summations [a = 10.359(4) Å, B = 5.388(2)Å, C = 11.234(4) Å, β = 110.48(2)°; space group C2/m; Z = 2; Rw = 0.025 for 1199 reflections up to sin /λ = 0.81 Å−1]. In detail, the structure consists of As(V)O4 tetrahedra and As(III)O3 pyramids linked by a common O corner atom to [As(V)As(III)O6]4− groups with symmetry m. The bridging bonds As(V)---O [1.749(3) Å] and As(III)---O [1.838(2) Å] are definitely longer than the other As(V)---O bonds [mean 1.669 Å] and As(III)---O bonds [1.764(2) Å, 2×]. The angle As(V)---O---As(III) is 123.0(1)°. The Cu atoms are [4 + 2]- and [4 + 1]-, and the K atom is [9]-coordinated to oxygen atoms. The As2O6 groups and the Cu coordination polyhedra are linked to sheets parallel to (001). These sheets are connected by the K atoms. Single crystals of K2Cu3(As2O6)2 suitable for X-ray work were synthesized under hydrothermal conditions.  相似文献   

15.
Recombination rate coefficients of protonated and deuterated ions KrH+, KrD+, XeH+ and XeD+ were measured using Flowing Afterglow with Langmuir Probe (FALP). Helium at 1600 Pa and at temperature 250 K was used as a buffer gas in the experiments. Kr, Xe, H2 and D2 were introduced to a flow tube to form the desired ions. Because of small differences in proton affinities of Kr, D2 and H2 mixtures of ions, KrD+/D3+ and KrH+/H3+ are formed in the afterglow plasma, influencing the plasma decay. To obtain a recombination rate coefficient for a particular ion, the dependencies on partial pressures of gases used in the ion formation were measured. The obtained rate coefficients, αKrD+(250 K) = (0.9 ± 0.3) × 10−8 cm3 s−1 and αXeD+(250 K) = (8 ± 2) × 10−8 cm3 s−1 are compared with αKrH+(250 K) = (2.0 ± 0.6) × 10−8 cm3 s−1 and αXeH+(250 K) = (8 ± 2) × 10−8 cm3 s−1.  相似文献   

16.
SmTe1.84was synthesized and the crystal structure was studied by the single-crystal technique. The substructure was isostructural with LaTe2−x, where corrugated rock salt LaTe slabs alternate with planar tellurium square lattices. The substructure of SmTe1.84is tetragonal anti-Cu2Sb type and the superstructure is √5×√5 of the tetragonal subcell. The superstructure is tetragonal, withP42/nsymmetry,a=9.709(1) Å andc=18.007(7) Å. There are both ordered and disordered defects in the Te sheet. The superstructure obtained consists of the three possible stable solutions suggested by Lee and Foran, and all three solutions were found in a single crystal. The resistivity dependence on temperature indicates that SmTe1.84is semiconducting, which seems due to structural modulation. The structural stability of the other phases of SmTen(n=1–2) is discussed in terms of temperature and ionic radius ratio.  相似文献   

17.
The new compounds K12Ta6Se35 and KTaTe3 have been synthesized through the reaction of Ta metal with a K2Qn(Q = Se, Te) flux. K12Ta6Se35, crystallizes with 4 formula units in space group Pbcn of the orthorhombic system in a cell of dimensions a = 8.3390(17) Å, b = 13.259(3) Å, c = 56.023(11) Å (t = −120 °C). KTaTe3 crystallizes with 20 formula units (or 4 formula units of K5Ta5Te15) in the monoclinic space group P21/c in a cell of dimension a = 7.7177(15) Å, b= 13.826(3) Å, c = 30.981(6) Å, and β = 90.11(3)° (t = −120 °C). Each structure consists of infinite anionic chains of Ta-containing polyhedra well separated by K+ cations. In K12Ta6Se35 there are Ta2Se11 units formed by the face sharing of two TaSe7 elongated bipyramids. These Ta2Se11 units are in turn interconnected by Se2 and Se3 units to form α1[Ta6Se3Se3512−]infinite chains. In KTaTe3, the α1[TaTe3] infinite chains arise from the face sharing of distorted TaTe6 octahedra.  相似文献   

18.
The phase relations in the system In2O3–TiO2–MgO at 1100 and 1350°C are determined by a classical quenching method. In this system, there are four pseudobinary compounds, In2TiO5, MgTi2O5 (pseudobrookite type), MgTiO3 (ilmenite type), and Mg2TiO4 (spinel type) at 1100°C. At 1350°C, in addition to these compounds there exist a spinel-type solid solution Mg2−xIn2xTi1−xO4 (0≤x≤1) and a compound In6Ti6MgO22 with lattice constants a=5.9236(7) Å, b=3.3862(4) Å, c=6.3609(7) Å, β=108.15(1)°, and q=0.369, which is isostructural with the monoclinic In3Ti2FeO10 in the system In2O3–TiO2–MgO. The relation between the lattice constants of the spinel phase and the composition nearly satisfies Vegard's law. In6Ti6MgO22 extends a solid solution range to In20Ti17Mg3O67 with lattice constants of a=5.9230(5) Å, b=3.3823(3) Å, c=6.3698(6) Å, β=108.10(5)°, and q=0.360. The distributions of constituent cations in the solid solutions are discussed in terms of their ionic radius and site preference effect.  相似文献   

19.
In the present work, blends of poly(ethylene oxide) (PEO), poly(acrylonitrile-co-methyl acrylate) (PANMA) and poly(4-vinylphenol-co-2-hydroxyethyl methacrylate) (PVPh-HEM) were studied by DSC, FTIR and electrochemical impedance spectroscopy (EIS). PEO/PANMA blends were found to be immiscible, while PEO/PVPh-HEM blends are miscible and PVPh-HEM/PANMA exhibits partial miscibility behaviour. The ternary PEO/PANMA/PVPh-HEM blends exhibited miscible compositions for PVPh-HEM and PEO-rich systems. The miscibility observed is a direct consequence of the hydrogen bond interactions among the polymer chains, in which the phenol groups in PVPh-HEM interact with both PEO and PANMA chains. The proton conductivity of a selected membrane based on the ternary blend containing 60% PEO and doped with H3PO4 aqueous solution reached 8 × 10−3 Ω−1 cm−1 at room temperature and 3 × 10−2 Ω−1 cm−1 at 80 °C.  相似文献   

20.
The electrical conductivity of the crystallized polyphosphates Li3Ba2(PO3)7, LiPb2(PO3)5, LiCs(PO3)2, and αLiK(PO3)2 has been determined at different temperatures by impedance spectroscopy. The conductivity, σ, spreads within a range of 1.59 × 10−8 to 1.79 × 10−7 S cm−1 at 573 K, and from 1.71 × 10−5 to 9.86 × 10−4 S cm−1 at 773 K. The transport should be assumed in the majority by the lithium ions with regard to the structural characteristics of these polyphosphates. The results are discussed and compared to the conductivity properties of other lithium ion conductors.  相似文献   

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