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1.
Amphiphile bilayer films are obtained from 1,2 dipalmitoyl-glycero-3-phosphocholine (DPPC): bilayer lipid membranes (BLM) and Newton black films (NBF), through thinning of the respective thin liquid films, thus allowing for a very precise determination of the moment of their formation. Stability (or rupture) and formation of BLM and NBF are considered from a unified point of view with the microscopic theory of Kashchiev–Exerowa [J. Colloid Interface Sci., 77 (1980) 501–511], based on the formation of nanoscopic holes in them. BLM and NBF are obtained and studied with the microinterferometric method of Scheludko–Exerowa in its contemporary version. The equivalent thickness of both BLM (in benzene solution between two water phases with 0.1 M NaCl) and NBF in aqueous DPPC solution (in the presence of 0.1 M NaCl) is determined as being hw = 7.0 nm for BLM and hw = 7.8 nm for NBF. By means of the dependences: BLM lifetime versus DPPC concentration and probability for BLM formation versus DPPC concentration, it is established that there exist metastable BLM and stable NBF. The good fit between the experimental results of τ( C) dependence and theory in the case of BLM allow to determine the three constants: pre-exponential factor A = 1.5 × 10 −3 s, related to the process kinetics; constant B = 20.2 ± 0.2, related to the specific hole energy γ = 1.7 × 10 −11 J/m and the equilibrium concentration Ce = 6 × 10 −4 ± 7.2 × 10 −6 m/l. The specific hole linear energy γ = 1.7 × 10 −11 J/m determined as well as the binding energy Q between first neighbor molecules in the bilayers Q = 1.48 × 10 −19 J (36 kT) are lower than the ones determined for DPPC foam bilayer in gel state γ = 9.1 × 10 −11 J/m and Q = 55 kT. This means that interaction is weaker in the case of BLM. The critical concentration Cc at which bilayer formation starts is: for BLM Cc = 30 μg/ml and for NBF Cc = 70 μg/ml. This concentration characterizes quantitatively the formation of the amphiphile bilayer and is a very useful parameter that can be used for various purposes. 相似文献
2.
Gas electron diffraction is applied to determine the geometric parameters of the silacyclobutane molecule using a dynamic model where the ring puckering was treated as a large amplitude motion. The structural parameters and the parameters of the potential function were refined taking into account the relaxation of the molecular geometry estimated from ab initio calculations at the MP2/6-311+G(d, p) level of theory. The potential function has been described as V( ) = V0[( / e) 2 − 1] 2 with the following parameters V0 = 0.82 ± 0.60 kcal/mol and e = 33.5 ± 2.7°, where is a puckering angle of the ring. The geometric parameters at the minimum V() (ra in Å, in degrees and uncertainties given as three times the standard deviations including a scale error) are: r(Si–Hax) = 1.467(96), r(Si–Heq) = 1.468(96), r(Si–C) = 1.885(2), r(C–C) = 1.571(3), r(C–H) = 1.100(3), CSiC = 77.2(9), HSiH = 108.3, SiCHeq = 123.5(16), SiCHax = 111.9(16), CC5Heq = 118.4(24), CC5Hax = 112.3(24), HC3H = 107.7, δ(HSiH) = 6.6, δ(HC3H) = 7.0, where the tilts δ, HSiH, and HC3H are estimated from ab initio constraints. The structural parameters are compared with those obtained for related compounds. 相似文献
3.
The molecular structure of trichloronitromethane has been studied in the gas phase using electron diffraction data. The molecules are found to undergo low barrier rotation about the CN bond with a planar CNO 2 moiety in agreement with HF/MP2/B3LYP/6-311G(d,p) calculations. The experimental data are consistent with a dynamic model using a potential function for the torsion of V = ( V6/2)(1 − cos 6 τ). The major geometrical parameters ( rg and ) for the eclipsed form, obtained from least squares analysis of the data are as follows: r(NO 3) = r(NO 4) = 1.213(2) Å, r(CN) = 1.592(6) Å, r(CCl) av = 1.749(1) Å, Cl 5CN/Cl 6CN = 109. 6°/106.3°(2), O 3NC/O 4NC = 117. 6°/114.1°(4), τCl 5C 1N 2O 3 = 0.0°, and V6 = 0.20(25) kcal/mol. 相似文献
4.
The monolayer behavior of three mixed systems of dipalmitoyl phosphatidyl choline (DPPC) with sterols; cholesterol (Ch), stigmasterol (Stig), and cholestanol (Chsta) formed at the interface of air/water (phosphate buffer solution at 7.4 with addition of NaCl) was investigated in terms of surface pressure ( π) and molecular occupation surface area ( A) relation. A series of π– A curves at every 0.1 mol fraction of each sterol for the three combinations of mixed systems were obtained at 25.0 °C. On the basis of the π–A curves, the additivity rule in regard to A versus sterol mole fraction (Xst) was examined at discrete surface pressures such as 5, 10, 15, 20, 25, 30 mN m−1, and then from the obtained A–Xst curves the partial molecular areas (PMA) were determined. The A–Xst relation exhibited a marked negative deviation from ideal mixing in the pressure range below 10 mN m−1, i.e. in the expanded liquid film region (below the transition pressure of DPPC). The PMA of Ch at π=5 mN m−1, for example, was found to be conspicuously negative in the range of XCh=0–0.2 (about −0.4 nm2 per molecule) and slightly positive (ca. 0.1 nm2 per molecule) in the range XCh=0.2 to 0.4. Above XCh=0.5, Ch’s PMA was almost the same as the surface area of pure Ch, while DPPC’s PMA was reduced to 60% of that of the pure system. Excess Gibbs energy (ΔG(ex)) as a function of Xst was estimated at different pressures. Applying the regular solution theory to thermodynamic analysis of ΔG(ex), the activity coefficients (f1 and f2) of DPPC and the respective sterols as well as the interaction parameter (Ip) in the mixed film phase were evaluated; the results showed a marked dependence on Xst. Compressibility Cs and elasticity Cs−1 were also examined. These physical parameters directly reflected the mechanical strength of formed monolayer film. Phase diagrams plotting the collapse pressure (πc) against Xst were constructed, and the πc versus Xst curves were examined for the respective mixed systems in comparison with the simulated curves of ideal mixing based on the Joos equation. Comparing the monolayer behavior of the three mixed systems, little remarkable difference was found in regard to various aspects. In common among the three combinations, the mole fraction dependence in monolayer properties was classified into three ranges: 0<Xst<0.2, 0.2<Xst<0.4 and 0.5<Xst<1. How the difference in the chemical structure of the sterols influenced the properties was examined in detail. 相似文献
5.
Anion exchange membrane has been investigated in different electrolyte solutions by chronopotentiometry to explore the influence of co-ion and counterion of the exchange group of the membrane, on the transport phenomena. Chloride, nitrate, sulfate and acetate in sodium salts were used as counterions and sodium, potassium, calcium and ammonium in chloride salts were used as co-ions. The membrane showed a potential drop ( E0) in all these electrolytes when a constant current was applied across it, which remained constant for a period less than τ, called the transition time and rose gradually to a maximum ( Emax) value. The parameters such as τ, E0 and Emax and the potential jump (Δ E) and τ and the inflection zone (Δ t) along the time axis have been measured and compared at an applied current density ( I) of 10 mA cm −2 in 10 mM solutions. The values of τ1/2/ zA[ A0] or τ1/2/ zC[ C0], with
or
, E0 and Δ E with
or
(where rA and rC are the ionic radii of counter and co-ions, respectively) have been correlated. Permselectivity ( P) and transference number
of the membrane with respect to each one of the above electrolytes have been evaluated and discussed. 相似文献
6.
A metal-organic complex, which has the potential property of absorbing gases, [LaCu 6(μ-OH) 3(Gly) 6im 6](ClO 4) 6 was synthesized through the self-assembly of La 3+, Cu 2+, glycine (Gly) and imidazole (Im) in aqueous solution and characterized by IR, element analysis and powder XRD. The molar heat capacity, Cp,m, was measured from T = 80 to 390 K with an automated adiabatic calorimeter. The thermodynamic functions [ HT − H298.15] and [ ST − S298.15] were derived from the heat capacity data with temperature interval of 5 K. The thermal stability of the complex was investigated by differential scanning calorimetry (DSC). 相似文献
7.
The syntheses and structural determination of Nd III and Er III complexes with nitrilotriacetic acid (nta) were reported in this paper. Their crystal and molecular structures and compositions were determined by single-crystal X-ray structure analyses and elemental analyses, respectively. The crystal of K 3[Nd III(nta) 2(H 2O)]·6H 2O complex belongs to monoclinic crystal system and C2/ c space group. The crystal data are as follows: a=1.5490(11) nm, b=1.3028(9) nm, c=2.6237(18) nm, β=96.803(10)°, V=5.257(6) nm 3, Z=8, M=763.89, Dc=1.930 g cm −3, μ=2.535 mm −1 and F(000)=3048. The final R1 and wR1 are 0.0390 and 0.0703 for 4501 ( I>2σ( I)) unique reflections, R2 and wR2 are 0.0758 and 0.0783 for all 10474 reflections, respectively. The Nd IIIN 2O 7 part in the [Nd III(nta) 2(H 2O)] 3− complex anion has a pseudo-monocapped square antiprismatic nine-coordinate structure in which the eight coordinate atoms (two N and six O) are from the two nta ligands and a water molecule coordinate to the central Nd III ion directly. The crystal of the K 3[Er III(nta) 2(H 2O)]·5H 2O complex also belongs to monoclinic crystal system and C2/ c space group. The crystal data are as follows: a=1.5343(5) nm, b=1.2880(4) nm, c=2.6154(8) nm, b=96.033(5)°, V=5.140(3) nm 3, Z=8, M=768.89, Dc=1.987 g cm −3, μ=3.833 mm −1 and F(000)=3032. The final R1 and wR1 are 0.0321 and 0.0671 for 4445 ( I>2σ( I)) unique reflections, R2 and wR2 are 0.0432 and 0.0699 for all 10207 reflections, respectively. The Er IIIN 2O 7 part in the [Er III(nta) 2(H 2O)] 3− complex anion has the same structure as Nd IIIN 2O 7 part in which the eight coordinate atoms (two N and six O) are from the two nta ligands and a water molecule coordinate to the central Nd III ion directly. 相似文献
8.
The paper presents a new method for predicting the frequency of the b1 mode, which is infrared-inactive, in complexes of the type LM(CO) 5 belonging to C4V point group. The method was based on the relation λ3=λ4+[(1−δ/δ)](λ1−λ2), where δ=(λ1−λ2)/(λ1−λ2+λ3−λ4), λ1, λ2, λ3 and λ4 are the λ parameters of the , , b1 and e modes, respectively. For a large numbers of complexes of the type LM(CO) 5 the average value of δ was found to be 0.80, with a standard deviation of 0.02. With the use of average value of δ, the frequencies of b1 mode were estimated. The result obtained indicated that there exists a rather good fit between observed and calculated frequencies, with a mean error of 2.7 cm −1. In addition, it was shown that the δ parameter can be used as a criterion of the correct band assignment for the complexes understudy. 相似文献
9.
In this study, gelatin blended with arabic gum microcapsules containing camphor oil with added polystyrene were fabricated by a compound coacervation method. The parameters of oil/wall volume ratio, emulsification stirring speed, concentration of cross-linking agent, treated time and oil release properties were investigated. In order to improve the constant release effect of camphor oil, oil-soluble polystyrene (PS) was used as a sustained release agent. The camphor oil release curves were expressed by the exponential equation: ψ( t) = Ceq(1–e −t/τ), where ψ( t) represent the variant of camphor oil concentration in the operation environment, Ceq as the equilibrium state, t as the release time and τ as time constant. Ceq and τ are significant factors pertaining to the camphor oil release properties. The results indicated that, for the microcapsules, the optimal oil/wall volume ratio was 0.75 to achieve the encapsulation efficiency of 99.6 wt.%. The average particle size were 294.7 ± 14.2 μm, 167.2 ± 11.2 μm, 85.7 ± 8.7 μm at the homogenization stirring speed of 500, 1000, and 2000 rpm, respectively. The effect of sustained oil release will increase whereas the stirring speed decreases and the concentration of glutaraldehyde (GA) and treated time increases. Along with the increasing of quantity of polystyrene added, Ceq decreased and τ increased, indicating that the sustained oil release amount and the release rate depend on the quantity of PS considerably. 相似文献
10.
Four neutral bimetallic clusters X 2M 2 (X=Si, Ge, M=Al, Ga) are investigated using density functional theory (DFT) and post-HF methods. The calculated results show that each of four X 2M 2 species has two energetically close stable isomers with rhombic structure ( D2h symmetry) and trapezoidal structure ( C2v symmetry) respectively. For the Ge 2Al 2 species the rhombic ( D2h) isomer is the ground state, whereas for other three species Ge 2Ga 2, Si 2Al 2, and Si 2Ga 2, the trapezoidal ( C2v) isomers are the ground states. The calculated magnetic susceptibility anisotropy ( χanis) and nucleus-independent chemical shift (NICS) indicate that a strong diatropic ring current exists in the two heterocyclic planar isomers, suggesting they are highly aromatic. A detailed molecular orbital analysis further reveals that both heterocyclic isomers possess multiple aromaticity derived from one delocalized π MOs and two delocalized σ MOs. 相似文献
11.
The relative viscosity ηr and, thus, the reduced viscosity η sp/ C of polymer solution could be obtained by recording the flow times of the polymer solution and the pure solvent in a capillary viscometer. Our experimental results indicated that the measurement of the flow time of the pure solvent was unnecessary. In particular, if the recorded flow time of the pure solvent was used to determine the viscosity of polymer solution, the reduced viscosity η sp/ C exhibited either a drastic increase or a significant decrease in an extremely dilute solution, depending upon the properties of the polymer solution investigated. In this research work, a new method for determining the viscosity of polymer solutions is reported. In the proposed method, the flow time of polymer solution at zero concentration, t0*, instead of the measured flow time of the pure solvent, was used to determine the viscosity of polymer solution. The reduced viscosity η sp/ C determined by the new method is proportional to concentration C even in an extremely dilute solution. The relative viscosity ηr vs. C plot also indicated clearly that t0*, instead of the measured flow time of the pure solvent, should be used for determining the viscosity of polymer solution. At low concentrations, the flow time of the polymer solution was proportional to C. As a result, t0* could be determined by extrapolating the flow time of the polymer solution to C=0. 相似文献
12.
电化学阻抗谱可用于诊断多孔电极内电荷转移反应,即界面电荷集聚和电荷传导,以及反应物质输运。本文采用复相量方法,在同态假设条件下,重新推演多孔电极阻抗谱模型,厘清传统多孔电极阻抗谱模型中的模糊性表述。(1) 定义多孔电极表征输入参数,包括电极基体电子电导率 σ1 、电解质离子电导率 σ2、界面电荷传递电导率 gct、单位面积界面电容 C、固相扩散系数 D、速度常数 k、电极厚度 d、特征孔深 Lp 和单位体积表面积 Sc;(2) 解析阻抗谱特征输出参数,包括场扩散常数 K,特征频率 ω0、 ω1、 ω2、 ω3和 ωmax,它们分别相关于界面传导反应、有限场扩散、氧化还原反应、孔内扩散和最小特征孔尺寸,以及分别对应于从传导到扩散和从扩散到饱和的转折频率 fk1 和 fk2;(3) 当参数 X和 Z同时变化时( X = σ1和 Z = d, Sc, Lp, C, gct, D, k),通过阻抗谱特征参数的演变规律,分析了电荷转移反应中 X和 Ζ参数耦合竞争;(4)为深入分析电荷转移反应中参数 X和 Z的耦合竞争,引入了分叉频率 fXZ和 fZX 。 fXZ和 fZX所处位置可以用于表征参数 X和 Z影响电荷转移反应的深度和广度。当分叉频率 fXZ和 fZX不存在时,表明电荷转移反应中参数 X和 Z在全频率范围内存在耦合竞争。总之,借助于特征频率和分叉频率,本文一方面研究了动力学参数和微观结构参数对多孔电极中电荷转移反应的影响,另一方面分析谱图的变化及其背后的阻抗谱特征演化规律。本文研究结果可为阻抗谱的系统仿真和辨识提供理论基础,可为多孔电极内电荷转移反应的竞争分析提供技术支撑,还可为电化学储能系统的优化设计提供诊断工具。 相似文献
13.
The cluster [Os 3(CO) 10(MeCN) 2] reacts with indazole (C 7H 6N 2) to give two isomeric products [0s 3( μ-H)( μ-C 7H 5N 2)(CO) 10] in which the five-membered ring has been metallated with N-H cleavage to give an N, N-bonded isomer or with C-H cleavage to give a C, N-bonded isomer. These two isomers have very similar X-ray structures but can be clearly distinguished by 1H NMR methods. They are shown to correspond to related clusters derived from pyrazole. Benzotriazole (C 6H 5N 3) also reacts (as shown earlier by others) to give two isomers: an N, N-bonded species [Os 3( μ-H)( μ-C 6H 4N 3)(CO) 10] coordinated only through the five-membered ring and a minor C, N-bonded isomer [Os 3( μ-H)( μ-C 6H 4N 3)(CO) 10], metallated at the C 6 ring and coordinated through both rings. The former isomer reacts with Me 3NO in acetonitrile to give [Os 3( μ-H)( μ-C 6H 4N 3)(CO) 9(MeCN)] which thermally looses MeCN to produce the coupled product [Os 6( μ-H) 2( μ3-C 6H 4N 3) 2(CO) 18] which was shown by X-ray structure determination to have all six nitrogen atoms coordinated to osmium, a novel situation for coordinated benzotriazole. The two Os 3 units are linked together by an OsNNOsNN ring in a boat conformation with the whole cluster adopting C2 symmetry. 相似文献
14.
Two nickel (imidazole) complexes, Ni(im) 6Cl 2·4H 2O (1) and Ni(im) 6(NO 3) 2 (2) (im=imidazole) have been synthesized and characterized by elemental analysis, IR, UV, TG and single crystal X-ray diffraction. 1 crystallizes in the triclinic space group P-1 with a=8.800(6) Å, b=9.081(6) Å, c=10.565(7) Å, =75.058(9)°, β=83.143(8)°, γ=61.722(8)°, V=718.3(8) Å 3, Z=1 and R1 ( wR2)=0.0469 (0.1497). 2 crystallizes in the trigonal space group R-3 with a=12.370(6) Å, b=12.370(6) Å, c=14.782(14) Å, =90.00°, β=90.00°, γ=120.00°, V=1959(2) Å 3, Z=3 and R1 ( wR2)=0.0358 (0.0955). 1 and 2 exhibit different supramolecular network due to their different counter anions and different hydrogen bonding connection. In compound 1, [Ni(im) 6] 2+ cation and counter anions Cl − alternatively array in an ABAB fashion via N–HCl hydrogen bonding. In compound 2, the plane of each NO 32− is almost parallel and each NO 32− connect three different [Ni(im) 6] 2+ cations via N–HO hydrogen bonding. 相似文献
15.
The disruption of lipidic metabolism was considered a good candidate to explain FB1 toxicity mechanism. In the present work we investigated molecular organizational changes induced by FB1–biomembrane interaction possibly involved in mycotoxic effects. FB1 was self-aggregated with a critical micellar concentration of 1.97 mM. FB1 (0–81.4 μM), decreased in a dose-dependent manner, the fluorescence anisotropy of TMA-DPH (from 0.349 ± 0.003 to 0.1720 ± 0.0035) in dpPC bilayers, whilst no differences were registered with DPH. At 5.6 μM in the subphase, FB1 increased the lateral surface pressure (π) of a Langmuir film to an extent that depended on the monolayer composition (ΔπdpPC:DOTAP 3:1 > ΔπdpPC:dpPA3:1 > ΔπdpPC), the molecular packing (Δπ decreased linearly as a function of the initial π) and the subphase pH (ΔπpH 2.6 > ΔπpH 7.4 and maximal π allowing the drug penetration πcut-off was 34.3 and 27.7 mN/m at pH 2.63 and 7.4, respectively). FB1 increased the surface potential of dpPC and dpPC:DOTAP monolayers and decreased that of dpPC:dpPA. This suggested that FB1 acquired different orientations and/or foldings depending on the surface electrostatics and the toxin charge state. Moreover, FB1–lipid interactions were transduced into long-range effects at the mesoscopic level affecting the lipidic self-separated lateral domains shape and density. 相似文献
16.
Reactions between cerium trifluoride and elemental fluorine have been examined by means of the kinetic and crystallographic method. The reactions were performed at 503–573 K under fluorine pressures of 6.7–26.7 kPa for reaction time up to 3 h. Two kinds of CeF 4 were synthesized by controlling the reaction condition. One is the metastable CeF 4-I synthesized at 523–538 K which returns to CeF 3 to release elemental fluorine, and the other is the stable CeF 4-II obtained at temperatures higher than ca. 540 K, which never returns to CeF 3. X-ray diffraction–Rietveld analysis revealed that the structure of CeF 4-I and CeF 4-II were monoclinic structure ( C12/ c1, Z=12, CeF 4-I/CeF 4-II: a0, 1.26 nm/1.25; b0, 1.06/1.05; c0, 0.82/0.82; β, 126.1/126.3°; cell volume, 8.91×10 −28/8.78×10 −28 m 3) and the cell volume of the CeF 4-I was 1.4% larger than that of the CeF 4-II. Bond lengths between Ce and F in CeF 4-I were somewhat longer than those in CeF 4-II. When CeF 4 and NaCl were put separately in the reaction container, CeF 4-I changed to CeF 3 with converting NaCl to NaF, however, CeF 4-II never reacted with NaCl. 相似文献
17.
A new 1.75 μm infrared emission transition of Y 2O 3:Er 3+ is assigned to the 4S 3/2 → 4I 9/2 transition of Er 3+ ions situated at the C2 sites of cubic RE 2O 3 (RE = Y, Gd, Lu). The intensities of features in the 1.54 μm 4I 15/2– 4I 13/2 absorption transition due to Er 3+ at S6 and C2 sites are consistent with the site occupation ratio and the relative magnetic dipole–electric dipole intensity contributions of Er 3+ at the different sites. The 1.54 μm emission lines are predominantly from Er 3+ ions at C2 sites. The different behaviours of the emission intensities 1.75 and 1.54 μm groups with change in Er 3+ dopant ion concentration, preparation technique, Yb 3+ co-doping, temperature change and different excitation line are rationalized. 相似文献
18.
Ab initio molecular orbital theory was used to determine the equilibrium structure and vibrational frequencies of Fe 2Cl 6 and FeAlCl 6. The equilibrium structure the Fe 2Cl 6 dimer has D2h symmetry with a planar arrangement of the four membered {FeCl brFeCl br} ring, similar to the Al 2Cl 6 dimer. The calculated bond distances and vibrational frequencies are in good agreement with experiment. The potential energy surface for the puckering of the {FeCl brFeCl br} ring is extremely flat. This prevents an unambiguous assignment of either D2h or C2v symmetry to the Fe 2Cl 6 structure in electron diffraction measurements. The FeAlCl 6 molecule is found to have a C2v structure similar to Fe 2Cl 6 with vibrational frequencies in good agreement with experiment. 相似文献
19.
The complexes formed by dimethylsulphide (DMS) and dimethyldisulphide (DMDS) with two isomers of nitrous acid have been observed, and characterised in argon and nitrogen matrices. The ν1 OH stretching vibration of the perturbed trans-HONO monomer is 425 and 294 cm −1 red shifted, respectively, for the DMS and DMDS complex in solid argon, and 441 and 301 cm −1 in solid nitrogen. A large blue shift is also observed for the ν3 NOH in-plane deformation mode: 101 and 80 cm −1 for DMS–HONO- trans in argon and nitrogen matrices and 46 cm −1 for DMDS–HONO- trans in nitrogen matrix. The results indicate formation of strong hydrogen bonds in the studied DMS–HONO and DMDS–HONO systems. The origin of the complicated shape of the ν1 OH absorption is discussed. Similarities and differences between argon and nitrogen matrices are considered. 相似文献
20.
CaRg n+ (Rg=He, Ne, Ar) complexes with n=1–4, are investigated by performing using the B3LYP/6-311+G (3df) density functional theory calculations. The CaHe n+ ( n=1–4) complexes are found to be stable. In the case of CaNe n+ and CaAr n+, stable structures and stationary point were found only for n=1 and 2. For n=3 in the C3V and the D3h point group as well as for n=4 in the Td (tetrahedral) point group a saddle point (imaginary frequency) is observed and global minimum could be obtained along the potential energy surface. 相似文献
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