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1.
A fast and sensitive liquid chromatography–mass spectrometry method was developed for the determination of ursolic acid (UA)
in rat plasma and tissues. Glycyrrhetinic acid was used as the internal standard (IS). Chromatographic separation was performed
on a 3.5 μm Zorbax SB-C18 column (30 mm × 2.1 mm) with a mobile phase consisting of methanol and aqueous 10 mM ammonium acetate
using gradient elution. Quantification was performed by selected ion monitoring with ( m/ z) − 455 for UA and ( m/ z) − 469 for the IS. The method was validated in the concentration range of 2.5 − 1470 ng mL −1 for plasma samples and 20 − 11760 ng g −1 for tissue homogenates. The intra- and inter-day assay of precision in plasma and tissues ranged from 1.6% to 7.1% and 3.7%
to 9.0%, respectively, and the intra- and inter-day assay accuracy was 84.2 − 106.9% and 82.1 − 108.1%, respectively. Recoveries
in plasma and tissues ranged from 83.2% to 106.2%. The limits of detections were 0.5 ng mL −1 or 4.0 ng g −1. The recoveries for all samples were >90%, except for liver, which indicated that ursolic acid may metabolize in liver. The
main pharmacokinetic parameters obtained were T
max = 0.42 ± 0.11 h, C
max = 1.10 ± 0.31 μg mL −1, AUC = 1.45 ± 0.21 μg h mL −1 and K
a = 5.64 ± 1.89 h −1. The concentrations of UA in rat lung, spleen, liver, heart, and cerebellum were studied for the first time. This method
is validated and could be applicable to the investigation of the pharmacokinetics and tissue distribution of UA in rats. 相似文献
2.
Five chemical compounds, CuMoO 4, Cu 3Mo 2O 9, Cu 2Mo 3O 10, Cu 6Mo 4O 15, and Cu 4?x Mo 3O 12 (0.10 ? x ? 0.40), were identified in the system Cu 2OCuOMoO 3 and characterized by DTA, X-ray powder patterns, ir spectra, and magnetic properties. Cupric molybdates CuMoO 4 and Cu 3Mo 2O 9 are stable in air up to 820 and 855°C, respectively, melting at these temperatures with simultaneous decomposition (oxygen loss). Congruent mp of cuprous molybdates Cu 2Mo 3O 10 and Cu 6Mo 4O 15, in argon, are 532 and 466°C, respectively. Nonstoichiometric phase Cu 4?x Mo 3O 12 = Cu 2+3Cu 01?xMo 6+3O 12, melts in argon between 630 and 650°C depending on the value of x and at 525–530°C undergoes polymorphic transformation. Areas of coexistence of the above-mentioned phases are determined. The μeff of Cu 2+ ions and θ values are: 1.80 B.M. and 28°K for CuMoO 4, 1.71 B.M. and ? 12°K for Cu 3Mo 2O 9, and 1.74 B.M. and ? 93°K for Cu 4?xMo 3O 12. Below 200°K CuMoO 4 becomes antiferromagnetic. Cu 2Mo 3O 10 and Cu 6Mo 4O 15 show weak temperature-independent paramagnetism. 相似文献
3.
Eight S-glycosylated 5,10,15,20-tetrakis(tetrafluorophenyl)porphyrins ( 1a′, 1b′, 1a and 1b ( a: S-glucosylated, b: S-galactosylated)) and their 1,3-dipolar cycloadducts, i.e. chlorins 2a′, 2b′, 2a and 2b were prepared by nucleophilic substitution of the pentafluorophenyl groups with S-glycoside. These photosensitizers were characterized by 1H, 13C and 19F NMR spectroscopies and elemental analysis. The photocytotoxicity of the S-glycosylated photosensitizers and the parent porphyrin ( 1) and chlorin ( 2) was examined in HeLa cells. Photosensitizers 1, 2, 1a′, 1b′, 2a′ and 2b′ showed no significant photocytotoxicity at the concentration of 0.5 μM, while the deprotected photosensitizers 1a, 1b, 2a and 2b were photocytotoxic. The strong inhibition by sodium azide of the photocytotoxicity of these photosensitizers suggested that 1O 2 is the main mediator. The S-glucosylated photosensitizers 1a and 2a showed higher photocytotoxicity than S-galactosylated 1b and 2b, respectively. The cellular uptake of 1a and 2a increased up to 24 h, while that of 1b and 2b was saturated by 12 h. 相似文献
4.
Dissociative and nondissociative electron attachment in the electron impact energy range 0–14 eV are reported for SOF 2 SOF 4, SO 2F 2, SF 4, SO 2, and SiF 4 compounds which can be formed by electrical discharges in SF 6. The electron energy dependences of the mass-identified negative ions were determined in a time-of-flight mass spectrometer. The ions studied include F – and SOF
2
–*
from SOF 2; SOF
3
–
and F – from SOF 4; SO 2F
2
–*
, SO 2F –, F
2
–
, and F – from SO 2F 2; SF
4
–*
and F – from SF 4; O –, SO –, and S – from SO 2; and SiF
3
–
and F – from SiF 4. Thermochemical data have been determined from the threshold energies of some of the fragment negative ions. Lifetimes of the anions SOF
2
–*
, SO 2F
2
–*
, and SF
4
–*
are also reported. 相似文献
5.
For 357 subshells of the 53 neutral atoms He through Xe in their ground states, the two-electron intracule (relative motion)
< u
k
>
nl
and extracule (center-of-mass motion) < R
k
>
nl
subshell moments in position space are examined as well as their counterparts < v
k
>
nl
and < P
k
>
nl
in momentum space, where n and l are the principal and azimuthal quantum numbers of the atomic subshell, respectively. It is clarified that between the intracule
and extracule moments the “2
k
-rule” is strictly valid, which means < u
k
>
nl
= 2
k
< R
k
>
nl
and < v
k
>
nl
= 2
k
< P
k
>
nl
for any nl subshell. Theoretical analysis also proves that for a particular case of k = +2, two relations < u
2>
nl
= ( N
nl
−1)< r
2>
nl
and < v
2>
nl
= ( N
nl
−1)< p
2>
nl
hold exactly, where N
nl
(≥2) is the number of electrons in the subshell nl, and < r
k
>
nl
and < p
k
>
nl
are the familiar one-electron subshell moments in position and momentum spaces, respectively. The latter equality establishes
a new and rigorous relation between the second electron-pair moments in momentum space and the total energy of an atom through
the virial theorem. For k=+1, −1, and −2, the numerical Hartree-Fock results for the 357 subshells show that there are approximate but accurate linear
relations between < u
k
>
nl
and < r
k
>
nl
and between < v
k
>
nl
and < p
k
>
nl
, in which the proportionality constant in each space depends on n, l, and k.
Received: 27 April 1998 / Accepted: 29 May 1998 / Published online: 28 August 1998 相似文献
6.
In the copolymerization of monomers M 1 and M 2 which form polymer radicals of chain length n of N 1n with electron on a M 1 type and N 2n with one on a M 2 type, it is assumed that the specific rates of termination between N 1n and N 1n and N 1s, N 1n and N 2s, and N 2n and N 2s are kα( ns) ?a, kβ( ns) ?a, and kγ( ns) ?a, respectively, where kα, kβ, and kγ are the rate constants of reaction between segment radicals in the respective termination, and a is constant. The relation between kinetic chain length n? and polymerization rate Rp is derived as: 1/ n? = 1/ n?0 + const. ( Rp) A(a), where n?0 is the kinetic chain length of the polymer formed by transfer and A ( a) is unity (predominance of transfer) and 1/(1–2 a) (no transfer). In the copolymerization between methyl methacrylate (M 1) and styrene (M 2) at 60°C, when Rp → 0, kr12/ k12 + kr21/ k21 = 5.9× 10 ?5 is obtained, where kr12 and kr21 are the rate constants of transfer of N 1 to M 2 and N 2 to M 1, and k12 and k21 are the rate constants of propagation of N 1 to M 2 and N 2 to M 1. In the absence of transfer, the a value is found to be 0.065 ± 0.008, from the relation between n? and Rp, regardless of the monomer composition. Such a value is also estimated by setting b = 0.72 in a = 0.153 (2 b–1), where b is the constant in the Mark-Houwink equation. Further, the value of kβ is found to be 1.18 × 10 9l./mole-sec, which is comparable with the diffusion-controlled rate of reaction between small molecules. The rate of reaction between segment radicals is fivefold larger than the polymer-polymer termination when transfer predominates. 相似文献
7.
New members of the AnBn−1O 3n perovskite-like family (Ba 5KNb 5O 18 and Sr 6Nb 4SnO 18 compounds) with n = 6 have been synthesized and studied by the X-ray powder diffraction. Their crystal structures were found to belong to the Ba 6Nb 4TiO 18-type with a = 0.57840(7) nm, c = 4.2532(5) nm and a = 0.5661(1) nm, c = 4.186(1) nm for Ba 5KNb 5O 18 and Sr 6Nb 4SnO 18, respectively. It was shown that Ba and K ( A-atoms) are completely disordered in the crystal structure of Ba 5KNb 5O 18 compound. But Nb and Sn atoms ( B-atoms) in the crystal structure of the Sr 6Nb 4SnO 18 compound are quite ordered with the preferred Sn +4 and Nb 5+ cations localization in the center of perovskite-like block and on the boundaries of these blocks, respectively. Temperature and frequency dependencies of the real components of electric conductivity σI and dielectric permeability ɛI; specific electric conductivity at the direct current σdc have been obtained by the impedance spectroscopy method for Sr 6Nb 4SnO 18. 相似文献
8.
Biotransformations of the N-phthaloyl derivatives of d- and l-methionine and of d- and l-ethionine by Beauveria bassiana ATCC 7159 or Beauveria caledonica ATCC 64970 produce the corresponding ( SS) sulfoxides in good yield and diastereomeric excess. Pure ( SSSC) diastereomers can be obtained from l-series substrates by crystallisation of the biotransformation extract, and the corresponding ( SSRC) products obtained from d-series substrates by chromatography of the biotransformation extract. Hydrogen peroxide-catalysed oxidation of the N-phthaloyl derivatives of d- and l-methionine and of d- and l-ethionine gives diastereomeric mixtures from which the ( SSSC) and ( RSRC) diastereomers can be obtained by crystallisation, and the ( SSRC) and ( RSSC) diastereomers obtained by chromatography. N-Cbz- and N- t-Boc methionines are also converted to sulfoxides with predominant ( SS) configuration by both B. bassiana and B. caledonica, but the isolated yields and d.e. of products were generally lower than those obtained from the N-phthaloyl substrates.Removal of the N-phthaloyl group from diastereomerically pure methionine and ethionine sulfoxides gave the corresponding amino acid sulfoxides in high yield; removal of N-Cbz and N- t-Boc groups from protected methionine sulfoxides was also achieved without loss of configuration at sulfur. 相似文献
9.
The thermal functions S 0T, -(G 0T-H 0O)/ T and (H 0T-H 0O) have been calculated from structural and spectroscopic data for the gaseous organometallics C 5H 5BeX (X = Cl, Br and BH 4), C 5H 5MX 3 (M = Ti and Ge; X = Cl, Br and I) and CH 3TiX 3 (X = Cl, Br and I). The rotational barriers of the C 5H 5 and CH 3 groups have been evaluated and discussed. 相似文献
10.
The Ag 2Se-Tl 2Se-Bi 2Se 3 quasi-ternary system (system A) was studied using DTA, X-ray powder diffraction, microstructure examination, and microhardness measurements. TlBiSe 2-AgBiSe 2, AgTlSe-AgBiSe 2, AgTlSe-Bi 2Se 3, and Tl 2Se-AgBiSe 2 polytherms, isothermal sections at 500 and 800 K, and liquidus surface projection of system A were constructed. System A is congruently triangulated into the following subordinate triangles: Tl 2Se-AgTlSe-Tl 9BiSe 6 ( I), AgTlSe-Tl 9BiSe 6-TlBiSe 2 ( II), Ag 2Se-AgTlSe-TlBiSe 2 ( III), Ag 2Se-AgBiSe 2-TlBiSe 2 ( IV), and AgBiSe 2-TlBiSe 2-Bi 2Se 3 ( V). Subsystems I, III, and V are ternary systems with three-phase eutectic equilibrium; system II has a three-phase eutectic, and system IV is characterized by several invariant and monovariant peritectic and eutectic equilibria. Primary crystallization and homogeneity
fields were outlined, and the types and coordinates of invariant and monovariant equilibria in system A were determined. A characteristic feature of the title system is an extensive field of solid solutions between high-temperature
cubic AgBiSe 2 and TlBiSe 2 phases; this field lies as a continuous belt along the AgBiSe 2-TlBiSe 2 quasibinary section and covers about one-fourth of the surface area of the triangular diagram of system A. 相似文献
11.
Alkali and ammonium cobalt and zinc phosphates show extensive polymorphism. Thermal behavior, relative stabilities, and enthalpies of formation of KCoPO 4, RbCoPO 4, NH 4CoPO 4, and NH 4ZnPO 4 polymorphs are studied by differential scanning calorimetry, high-temperature oxide melt solution calorimetry, and acid solution calorimetry. α-KCoPO 4 and γ-KCoPO 4 are very similar in enthalpy. γ-KCoPO 4 slowly transforms to α-KCoPO 4 near 673 K. The high-temperature phase, β-KCoPO 4, is 5-7 kJ mol −1 higher in enthalpy than α-KCoPO 4 and γ-KCoPO 4. HEX phases of NH 4CoPO 4 and NH 4ZnPO 4 are about 3 kJ mol −1 lower in enthalpy than the corresponding ABW phases. There is a strong relationship between enthalpy of formation from oxides and acid-base interaction for cobalt and zinc phosphates and also for aluminosilicates with related frameworks. Cobalt and zinc phosphates exhibit similar trends in enthalpies of formation from oxides as aluminosilicates, but their enthalpies of formation from oxides are more exothermic because of their stronger acid-base interactions. Enthalpies of formation from ammonia and oxides of NH 4CoPO 4 and NH 4ZnPO 4 are similar, reflecting the similar basicity of CoO and ZnO. 相似文献
12.
In the Sc 2O 3---Ga 2O 3---CuO, Sc 2O 3---Ga 2O 3---ZnO, and Sc 2O 3---Al 2O 3---CuO systems, ScGaCuO 4, ScGaZnO 4, and ScAlCuO 4 with the YbFe 2O 4-type structure and Sc 2Ga 2CuO 7 with the Yb 2Fe 3O 7-type structure were obtained. In the In 2O 3--- A2O 3--- BO systems ( A: Fe, Ga, or Al; B: Mg, Mn, Fe, Ni, or Zn), InGaFeO 4, InGaNiO 4, and InFe 3+MgO 4 with the spinel structure, InGaZnO 4, InGaMgO 4, and InAlCuO 4 with the YbFe 2O 4-type structure, and In 2Ga 2MnO 7 and In 2Ga 2ZnO 7 with the Yb 2Fe 3O 7-type structure were obtained. InGaMnO 4 and InFe 2O 4 had both the YbFe 2O 4-type and spinel-type structures. The revised classification for the crystal structures of AB2O 4 compounds is presented, based upon the coordination numbers of constituent A and B cations. 相似文献
13.
The fast sequential multi-element determination of Ca, Mg, K, Cu, Fe, Mn and Zn in plant tissues by high-resolution continuum source flame atomic absorption spectrometry is proposed. For this, the main lines for Cu (324.754 nm), Fe (248.327 nm), Mn (279.482 nm) and Zn (213.857 nm) were selected, and the secondary lines for Ca (239.856 nm), Mg (202.582 nm) and K (404.414 nm) were evaluated. The side pixel registration approach was studied to reduce sensitivity and extend the linear working range for Mg by measuring at wings (202.576 nm; 202.577 nm; 202.578 nm; 202.580 nm; 202.585 nm; 202.586 nm; 202.587 nm; 202.588 nm) of the secondary line. The interference caused by NO bands on Zn at 213.857 nm was removed using the least-squares background correction. Using the main lines for Cu, Fe, Mn and Zn, secondary lines for Ca and K, and line wing at 202.588 nm for Mg, and 5 mL min − 1 sample flow-rate, calibration curves in the 0.1–0.5 mg L − 1 Cu, 0.5–4.0 mg L − 1 Fe, 0.5–4.0 mg L − 1 Mn, 0.2–1.0 mg L − 1 Zn, 10.0–100.0 mg L − 1 Ca, 5.0–40.0 mg L − 1 Mg and 50.0–250.0 mg L − 1 K ranges were consistently obtained. Accuracy and precision were evaluated after analysis of five plant standard reference materials. Results were in agreement at a 95% confidence level (paired t-test) with certified values. The proposed method was applied to digests of sugar-cane leaves and results were close to those obtained by line-source flame atomic absorption spectrometry. Recoveries of Ca, Mg, K, Cu, Fe, Mn and Zn in the 89–103%, 84–107%, 87–103%, 85–105%, 92–106%, 91–114%, 96–114% intervals, respectively, were obtained. The limits of detection were 0.6 mg L − 1 Ca, 0.4 mg L − 1 Mg, 0.4 mg L − 1 K, 7.7 µg L − 1 Cu, 7.7 µg L − 1 Fe, 1.5 µg L − 1 Mn and 5.9 µg L − 1 Zn. 相似文献
14.
Phase equilibria in the Nb-Nb 5Si 3-NbB region were studied in the melting (crystallization) range by means of light microscopy, XRD, SEM and EMPA on alloys after arc-melting and annealing at 1800°C and at subsolidus temperatures. Phase transition and melting temperatures were determined by DTA and pyrometric Pirani-Alterthum technique resulting in a solidus projection and two isopleths, Nb 77Si 23-Nb 77B 23 and Nb 99Si 1-Nb 5Si 2B. The T2-phase Nb 5Si 3−xB x (0? x?2, Cr 5B 3-type) was found to form equilibria with (Nb), NbB, Nb 3Si, and with the T1-phase (Mn 5Si 3 derivative type). The T2-phase melts incongruently (Nb 5Si 1.8B 1.2 at 2245°C) and forms a quasibinary eutectic with the niobium solid solution on a minimum tie-line at ∼1880°C. 相似文献
15.
We have measured the densities of aqueous solutions of isoleucine, threonine, and equimolal solutions of these two amino acids with HCl and with NaOH at temperatures 278.15 ⩽ T/K ⩽ 368.15, at molalities 0.01 ⩽ m/mol · kg −1 ⩽ 1.0, and at the pressure 0.35 MPa using a vibrating tube densimeter. We have also measured the heat capacities of these solutions at 278.15 ⩽ T/K ⩽ 393.15 and at the same m and p using a twin fixed-cell differential temperature-scanning calorimeter. We used the densities to calculate apparent molar volumes Vϕ and the heat capacities to calculate apparent molar heat capacities Cp,ϕ for these solutions. We used our results and values from the literature for Vϕ( T, m) and Cp,ϕ( T, m) for HCl(aq), NaOH(aq), and NaCl(aq) and the molar heat capacity change Δ rCp,m( T, m) for ionization of water to calculate parameters for Δ rCp,m( T, m) for the two proton dissociations from each of the protonated aqueous cationic amino acids. We used Young’s Rule and integrated these results iteratively to account for the effects of equilibrium speciation and chemical relaxation on Vϕ( T, m) and Cp,ϕ( T, m). This procedure gave parameters for Vϕ( T, m) and Cp,ϕ( T, m) for threoninium and isoleucinium chloride and for sodium threoninate and isoleucinate which modeled our observed results within experimental uncertainties. We report values for Δ rCp,m, Δ rHm, pQa, Δ rSm, and Δ rVm for the first and second proton dissociations from protonated aqueous threonine and isoleucine as functions of T and m. 相似文献
16.
Iodine-mediated cyclization of (Z)- and (E)-{=D}-ribohept-2-enonates and gave exclusively the β-ribofuranose and α-ribofuranose derivatives and , respectively. Cyclization of the (Z)- and (E)-2-heptene-1-ol derivatives and gave ribofuranose products ( and ) and a ribopyranose ( ), respectively. 相似文献
17.
A rate constant is generally derived by using Fick's equation corresponding to the spherical interdiffusion of particles. By using this rate constant, chain and primary radical termination rate constants can be approximated to rate constants for the bimolecular reactions between two radical chain ends, and primary radical and radical chain end, respectively. The former is given by ks = 8π NLDsLs exp { ? Ls/ Rs} × 10 ?3 1./mole-sec. The latter is given by ksi = 4π NL( Ds + Di) Lsi exp { ? Lsi/ Rsi} × 10 ?3 1./mole-sec. Here, NL is Avogadro's number; Ds and Di are the diffusion constants of radical chain end and primary radical, respectively; Ls and Lsi are, respectively, the distances between two radical chain ends and between a primary radical and a radical chain end at a thermal energy equal to the coulombic energy of interaction of the net charges; and Rs and Rsi are, respectively, the average distances between two radical chain ends and primary radical on a collision. 相似文献
18.
>为获得综合性能更好的锂离子二次电池正极材料, 分析了Co掺杂对Li xNiO 2电化学性能的影响. 采用密度泛函DFT理论对Li xNiO 2和Li xNi 0.5Co 0.5O 2的平均放电电压和态密度进行了计算. 同时, 用共沉淀法制备了Li xNiO 2和Li xNi 0.5Co 0.5O 2锂离子二次电池正极材料, 并对其进行了XRD结构分析和恒流充放电测试. 实验和计算结果表明: 随锂离子嵌入正极(电池放电), 电池的电压逐渐降低, 材料的态密度峰向低能量方向移动; 与Li xNiO 2相比, Li xNi 0.5Co 0.5O 2的电压平台相对较高(当0.25≤ x≤0.5), 而且在Li +嵌/脱时, Li xNi 0.5Co 0.5O 2的结构变化相对较小; Co离子的掺入, 减小了NiO 6八面体的畸变度, 使材料的电化学稳定性得以提高. 在钴掺杂镍酸锂体系中, NiO 6和CoO 6具有相互的稳定作用. 相似文献
19.
Binary As–Se glasses with different amounts of As content have been prepared and scanned with different heating rates (3 ≤ ψ ≤ 48 K min−1) over temperatures ranging from 300 to 450 K. Both the glass transition temperature (Tgl) and the temperature peak of crystallization (Tpc) increase as a function of As and/or the ψ values. A good correlation between Tgl and Tpc has been investigated. The observed increase in Tgl and Tpc by increasing the ψ values or as a function of As is well discussed in accordance with Lasocka’s relationship and using the average coordination number Acn, the viscosity at glass transition μ(Tgl) and the overall mean bond energy E. The glass transition Egl and crystallization activation energies (Egl and Epc) were determined based on the changes in Tgl and Tpc values due to the heating rate (ψ). The increase in the values of Egl and Epc with increasing the As content is expected due to the increase in Tgl and Tpc values. The kinetic exponent n and the crystal dimensionality m have been determined. 相似文献
20.
Low-temperature heat capacities of the compound Na(C 4H 7O 5)·H 2O(s) have been measured with an automated adiabatic calorimeter. A solid-solid phase transition and dehydration occur at 290-318 K and 367-373 K, respectively. The enthalpy and entropy of the solid-solid transition are Δ transHm = (5.75 ± 0.01) kJ mol −1 and Δ transSm = (18.47 ± 0.02) J K −1 mol −1. The enthalpy and entropy of the dehydration are Δ dHm = (15.35 ± 0.03) kJ mol −1 and Δ dSm = (41.35 ± 0.08) J K −1 mol −1. Experimental values of heat capacities for the solids (I and II) and the solid-liquid mixture (III) have been fitted to polynomial equations. 相似文献
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