共查询到20条相似文献,搜索用时 26 毫秒
1.
The adsorption of fibronectin on a series of different surfaces was investigated with in situ ellipsometry. For silica and methylated silica, the adsorbed amount (Γ), the adsorbed layer thickness (δ el) and the mean adsorbed layer refractive index ( nf) were obtained by a procedure involving studies of the bare substrate at two different ambient refractive indices, as well as four-zone averaging. It was found that the adsorbed amount of fibronectin was the same (1.9 ± 0.1 mg m −2) on both silica and methylated silica surfaces. However, the adsorbed layers formed on methylated silica were more extended and had a lower average protein concentration than those formed on silica. Furthermore, on both silica and methylated silica, an increasing adsorbed amount is achieved both by a denser packing of the fibronectin molecules and by a growth of the adsorbed layer normal to the surface. Furthermore, the adsorption of fibronectin on lipid surfaces was investigated. It was found that the adsorption of fibronectin on phosphatidic acid was quite significant (2.2 ± 0.2 mg m −2), while that on phosphatidylcholine, phosphatidylinositol and phosphatidylserine was much smaller (all 0.1 ± 0.05 mg m −2). These results are correlated to findings on the adsorption of fibrinogen on these surfaces, as well as on the opsonization of lipid-stabilized colloidal particles. 相似文献
2.
A novel copper(II) thiocyanate complex [Cu(im) 2(NCS) 2] 1 (im=imidazole) has been prepared and characterized by spectroscopic analysis and crystallographic method. This supramolecular compound exhibits a three-dimensional solid state structure constituted by N–HS hydrogen bonds and π–π stacking interactions. The compound in DMF solutions has a very strong third-order non-linear optical (NLO) behavior with absorption coefficient and refractive index 2=1.18×10 −11 mw −1, n2=−9.00×10 −16 m 2w −1, respectively, and third-order NLO susceptibility χ (3) of 7.00×10 −10 esu. 相似文献
3.
Density and refractive index measurements in the discotic liquid crystal hexaheptyloxytriphenylene were performed in the hexagonal columnar Col ho and isotropic I phases. The temperature dependence of the density ρ( T) for this compound was obtained by combining small angle X-ray data and capillary methods. The ordinary no extraordinary ne and isotropic liquid ni refractive indices were measured using a modified Abbe refractometer to an accuracy of about 10 -3. To check the consistency of the density and the refractometry experiments we used the Lorentz-Lorenz relation. An anomaly in the empirical relationship at the Col ho-I phase transition, which holds for many uniaxial liquid crystals, was detected. A discrepancy between low birefringence Δ n∼0.109 and a relatively high local electric field anisotropy for hexaheptyloxytriphenylene is discussed. 相似文献
4.
The synthesis, optical properties, electrochemical properties, electronic structures and applications in electroluminescent device of three series of 1,3,4-oxadiazole derivatives, 1,4-bis[(4-methylphenyl)-1,3,4-oxadiazolyl]phenylene (OXD 1), 5,5′-di-(4-methyl)-2,2′- p-(2,5-bisalkoxyphenylene)-bis-1,3,4-oxadiazole (OXD 2–n) and 1,4-bis[(4-alkoxyphenyl)-1,3,4-oxadiazolyl]phenylene (OXD 3–n) are reported. The molecular structures of the oxadiazole compounds were confirmed by FT-IR, 1H NMR spectroscopy and elemental analysis. The optical and electrochemical properties of the compounds were investigated by UV–vis absorption and photoluminescence spectroscopy as well as cyclic voltammetry. The results show that introduction of two alkoxy groups whose electron-donating ability is stronger than that of methyl groups increases the electron density of the conjugated segment of OXD 2–n (with side-on alkoxy substituents) and OXD 3–n (with end-on alkoxy substituents), and thus leads to the absorption maximum bathochromic-shift compared to that of OXD 1. The HOMO and LUMO energy levels of the compounds studied are in the range of −2.78 to −2.89 and −5.75 to −6.20 eV. Calculations on the representative compounds by the Dmol 3 package of MS Modeling 3.0 revealed that the increase of energy levels in both OXD 2–n and OXD 3–n was due to the change of the frontier molecular orbital distribution in the central benzene ring. The light-emitting devices have been fabricated using blends of MEH-PPV and these compounds as emissive layers, among which, maximum brightness up to 11810 cd m −2 (8.5 V) has been observed, which is 40 times brighter than that with MEH-PPV. The result of the devices suggested that oxadiazole derivatives studied function well as electron-transporting materials and can be used in LEDs, and thus to enhance the efficiency of LEDs. 相似文献
5.
Structure, electronic state and energy of Si nC − and Si nC −2 ( n=1–7) anions have been investigated using the density functional theory. Structural optimization and frequency analysis are performed at the level B3LYP/6-311G(d). The charged-induced structural changes in these anions have been discussed. The strong C–C bond is also favored over C–Si bonds in the Si nC −m anions in comparison with corresponding neutral cluster. Among different Si nC − and Si nC −2 ( n=1–7) anions, Si 3C −, Si 5C − and Si 2C −2 are most stable. Their stability has a decreasing tendency with the increase in the size of these clusters. 相似文献
6.
P- tert-butylcalix[ n]arenes ( n=4, 6, 8, abbreviated as CA[4], CA[6], CA[8], respectively) were immobilized on the Au surface of the piezoelectric quartz crystal by the reaction between CA[ n] and the acid chloride terminated mercaptoacetic acid (MAA) self assembled monolayers to form MAA/CA[ n] bilayers. The sensing films were not only immobilized easily and reproducibly, but also used to improve the reversibility of the sensor signal. The response characteristics show the response of CA to organic amine attributes to specific interaction between CA[ n] (host) and organic amines (guest). The frequency shifts of n-butylamine and iso-butylamine are much larger than tert-butylamine and diethylamine because of shape-selection and hydrogen bonding. Compared to CA[6] and CA[4], CA[8] has highest sensitivity to organic amine due to having more flexibility to accommodate guest molecules. A sensor array with three-layer back-propagation neural network was applied to detect the binary mixture of n-butylamine in the range of 7.14–142 μl l −1 and iso-butylamine in the range of 7.14–57 μl l −1. The optimum values of learning rate (0.15) and momentum term (0.8) were determined by experiment. The best epoch of training was 1098. The root mean square error of prediction was 1.69 (μl l −1) for n-butylamine, and 1.42 (μl l −1) for iso-butylamine. 相似文献
7.
When GaAs–Si and GaAs–AlGaAs heterostructures are exposed to γ-quanta, radiation stimulated ordering is observed. However, the gettering efficiency in such systems falls for layer widths more than 1 μm. For this reason we seek effective methods of radiation resistance improvement of materials in which one would expect point radiation defects to be gettered not only at defect boundaries, but also in the active layer volume. S.i.GaAs–s.i.AlxGa1−xAs–nGaAs : Te heterostructures are presented with epitaxial layers (doped with Yb or undoped), obtained by means of LPE (liquid-phase epitaxy). The electron concentration in nGaAs was found to be (1–3)×1018 cm−3 for widths 1–3 μm. The samples were exposed to 60Co γ-quanta with doses of 105–107 rad. Investigations of irradiated samples by means of low-temperature (4.2 K) photoluminescence have shown considerable decrease of exciton halfwidth in the boundary spectra of nGaAs : Te : Yb epitaxial layers in comparison with nGaAs : Te layer spectra. This is caused by background impurity gettering which happens on the s.i.AlxGa1−xAs–nGaAs heteroboundaries as well as in deformed regions in the epitaxial layer volume. Formation of such regions is caused by the difference between the covalent radii of Yb atoms and GaAs lattice atoms. The maximum effect of radiation stimulated gettering of dopants in nGaAs epitaxial layers is observed for Yb concentrations which are equal to 10−4–10−5 atomic fractions in a solution-melt. It is determined that the deformed regions in epitaxial layer volumes and heteroboundaries could be efficient drains for point radiation defects which form under radiation exposure. The investigations carried out showed that the doping of an epitaxial layers by rare-earth impurities provides considerable improvement in forming radiation resistant III–V materials. 相似文献
8.
The tetrathiomolybdate ion [MoS 4] 2− reacts in DMF solution with Roussin esters Fe 2(SR) 2(NO) 4 (R = Me, Et, n-Pr, i-Pr, n-Bu, t-Bu, n-C 5H 11) to yield the paramagnetic iron nitrosyls [Fe(NO) 2(SR) 2] − (1), [Fe(NO) 2(S 2MoS 2] − (2) and [Fe(NO)(S 2MOS 2) 2] − (3). The new complexes (2) and (3) have been characterized by EPR spectroscopy and the assignment to them of constitutions based respectively upon tetrahedral and square pyramidal iron is supported by EHMO calculations. Fe 2(SPh) 2(NO) 4 with [MoS 4] 2− yields only [Fe(NO) 2(SPh) 2] −, and preformed (3) reacts with PhS − to give firstly EPR-silent species, and then [Fe(NO) 2(SPh) 2] −. The mononitrosyl (3) can also be formed by reaction of [MoS 4] 2− with [Fe 4S 3(NO) 7] −, Fe 4S 4(NO) 4, or Fe 2I 2(NO) 4. 相似文献
9.
The oxidation state, the mobility and the molecular structure of chromium species present on CrO x–Al 2O 3 catalysts have been studied by combined diffuse reflectance spectroscopy, EPR and reduction–extraction by ethane 1,2 diol. CrO 42− species exist on the alumina surface in the form of loosely-interacting species on hydrated surface (species A) and in the form of strongly bonded species on dehydrated Al 2O 3 surface (species B). The CrO 42− species show high mobility and are probably responsible for the formation of CrO x clusters. 相似文献
10.
Fluorescence quantum yields, Y, front photoselected vibrational states in the S 1 manifold of anthracene and of perdeuterated anthracene in planar supersonic jets reveal a large inverse deuterium isotope effect on the non-radiative relaxation from the S 1 origin ( YH/ YD = 5), while for high (1500 cm −1) excess energies above the S 1 origin the inverse isotope effect is eroded ( YH/ YD ≈ 1). Novel information emerges on intermediating states involved in intersystem crossing. 相似文献
11.
A calorimetric study was performed for adducts of general formula CdBr 2· nL ( n=1 and 2; L=ethyleneurea (eu) and propyleneurea (pu)). The standard molar reaction enthalpy in condensed phase: CdBr 2(c)+ nL(c)=CdBr 2· nL(c); Δ rHmθ, were obtained by reaction–solution calorimetry, to give the following values for mono- and bis-adducts: −19.54 and −34.59; −7.77 and −19.05 kJ mol −1 for eu and pu adducts, respectively. Decomposition (Δ DHmθ) and lattice (Δ MHmθ) enthalpies, as well as the mean cadmium---oxygen bond dissociation enthalpy, DCd---O, were calculated for all adducts. 相似文献
12.
Synthesized hydrated lamellar acidic crystalline magadiite (H 2Si 14O 29·2H 2O) nanocompound was used as host for intercalation of polar n-alkylmonoamine molecules of the general formula H 3C(CH 2) nNH 2 ( n = 1–6) in aqueous solution. The original interlayer distance ( d) of 1500 pm, determined by X-ray powder diffraction patterns, increases after intercalation. The values correlated with the number of aliphatic amine carbon ( nc) atoms: d = [(1312 ± 11) + (21 ± 2)] nc. The amount of intercalated amines ( Ns), decreased as nc increased: Ns = [(5.82 ± 0.04) − (0.45 ± 0.01)] nc. The acidic layered nanocompound was calorimetrically titrated with the amines and the thermodynamic data gave exothermic values for all guest molecules, as shown by the correlation: Δ intH = −[(24.45 ± 0.49) − (1.91 ± 0.10)] nc and d = [(1576 ± 16) − (10.8 ± 1.0)]Δ intH. The negative values of the Gibbs energies and the positive entropies also presented the correlations: Δ intG = −[(22.8 ± 0.2) − (0.2 ± 0.1)] nc and Δ intS = [(6 ± 1) + (5 ± 1)] nc, respectively. 相似文献
13.
Nest-shaped cluster [MoOICu 3S 3(2,2′-bipy) 2] (1) was synthesized by the treatment of (NH 4) 2MoS 4, CuI, ( n-Bu) 4NI, and 2,2′-bipyridine (2,2′-bipy) through a solid-state reaction. It crystallizes in monoclinic space group P2 1/ n, a=9.591(2) Å, b=14.820(3) Å, c=17.951(4) Å, β=91.98(2)°, V=2549.9(10) Å 3, and Z=4. The nest-shaped cluster was obtained for the first time with a neutral skeleton containing 2,2′-bipy ligand. The non-linear optical (NLO) property of [MoOICu 3S 3(2,2′-bipy) 2] in DMF solution was measured by using a Z-scan technique with 15 ns and 532 nm laser pulses. The cluster has large third-order NLO absorption and the third-order NLO refraction, its 2 and n2 values were calculated as 6.2×10 −10 and −3.8×10 −17 m 2 W −1 in a 3.7×10 −4 M DMF solution. 相似文献
14.
High resolution vibration-rotation spectra of 13C 2H 2 were recorded in a number of regions from 2000 to 5200 cm −1 at Doppler or pressure limited resolution. In these spectral ranges cold and hot bands involving the bending-stretching combination levels have been analyzed up to high J values. Anharmonic quartic resonances for the combination levels ν 1 + mν 4 + nν 5, ν 2 + mν 4 + ( n + 2) ν 5 and ν 3 + ( m − 1) ν 4 + ( n + 1) ν 5 have been studied, and the l-type resonances within each polyad have been explicitly taken into account in the analysis of the data. The least-squares refinement provides deperturbed values for band origins and rotational constants, obtained by fitting rotation lines only up to J ≈ 20 with root mean square errors of ≈ 0.0003 cm −1. The band origins allowed us to determine a number of the anharmonicity constants xij0. 相似文献
15.
A thin, gas-tight palladium (Pd) membrane was prepared by the counter-diffusion chemical vapor deposition (CVD) process employing palladium chloride (PdCl 2) vapor and H 2 as Pd precursors. A disk-shaped, two-layer porous ceramic membrane consisting of a fine-pore γ-Al 2O 3 top layer and a coarse-pore -Al 2O 3 substrate was used as Pd membrane support. A 0.5–1 μm thick metallic membrane was deposited in the γ-Al 2O 3 top layer very close to its surface, as verified by XRD and SEM with a backscattered electron detector. The most important parameters that affected the CVD process were reaction temperature, reactants concentrations and top layer quality. Deposition of Pd in the γ-Al 2O 3 top layer resulted in a 100- to 1000-fold reduction in He permeance of the porous substrate. The H 2 permeation flux of these membranes was in the range 0.5–1.0 × 10 −6 mol m −2 s −1 Pa −1 at 350–450°C. The H 2 permeation data suggest that surface reaction steps are rate-limiting for H 2 transport through such thin membranes in the temperature range studied. 相似文献
16.
The generality of a two-electron reduction process involving an
mechanism has been established for M 3(CO) 12 and M 3(CO) 12− n(PPh 3) n (M = Ru, Os) clusters in all solvents. Detailed coulometric and spectral studies in CH 2Cl 2 provide strong evidence for the formation of an ‘opened’ M 3(CO) 122− species the triangulo radical anions M 3(CO) 12−· having a half-life of < 10 −6 s in CH 2Cl 2. However, the electrochemical response is sensitive to the presence of water and is concentration dependent. An electrochemical response for “opened” M 3(CO) 122− is only detected at low concentrations < 5 × 10 −4 mol dm −3 and under drybox conditions. The electroactive species ground at higher concentrations and in the presence of water M 3(CO) 112− and M 6(CO) 182− were confirmed by a study of the electrochemistry of these anions in CH 2Cl 2; HM 3(CO) 11− is not a product. The couple [M 6(CO) 18] −/2− is chemically reversible under certain conditions but oxidation of HM 3(CO) 11− is chemically irreversible. Different electrochemical behaviour for Ru 3(CO) 12 is found when [PPN][X] (X = OAc −, Cl −) salts are supporting electrolytes. In these solutions formation of the ultimate electroactive species [μ-C(O)XRu 3(CO) 10] − at the electrode is stopped under CO or at low temperatures but Ru 3(CO) 12−· is still trapped by reversible attack by X presumably as [η 1-C(O)XRu 3(CO) 11] −. It is shown that electrode-initiated electron catalysed substitution of M 3(CO) 12 only takes place on the electrochemical timescale when M = Ru, but it is slow, inefficient and non-selective, whereas BPK-initiated nucleophilic substitution of Ru 3(CO) 12 is only specific and fast in ether solvents particulary THF. Metal---metal bond cleavage is the most important influence on the rate and specificity of catalytic substitution by electron or [PPN]-initiation. The redox chemistry of M 3(CO) 12 clusters (M = Fe, Ru, Os) is a consequence of the relative rates of metal---metal bond dissociation, metal-metal bond strength and ligand dissociation and in many aspects resembles their photochemistry. 相似文献
18.
Polyvinylalcohol was activated with 2-fluoro-1-methylpyridiniumtoluene-4-sulphonate and urease (EC.3.5.1.5) was covalently linked to the activated matrix. PVA-urease was then immobilized on the surface of a pH glass electrode with gelatine gel and it was cross-linked using glutaraldehyde. This potentiometric membrane electrode provides a linearity to urea in the 8.910 −5 to 1.110 −3 M concentration range, but by changing the buffer concentration can be studied in the range of 10 −4 to 10 −2 M urea concentration. Reproducibility experiments ( n:20) were carried out with the urease enzyme electrode and with photometric methods for pooled serum sample. Average values for the two methods were 5.96 and 5.86 mM, variation coefficients were 2.5 and 3.5% respectively. 相似文献
19.
The influence of temperature on the optical and structural properties of three samples of polypropylene fibres (having different deniers) has been studied over the temperature range (28–67 oC). A hot-stage attached with the Pluta microscope has been modified for this purpose. The effect of temperature on the refractive indices ( n, n), the mean polarizabilities per unit volume ( Pll, P) and the optical orientation function f(θ) have been investigated for each sample. The thermal coefficients of the refractive indices were determined. The refractive index profiles are also provided at different temperatures for each of the three tested samples. Microinterferograms are given for illustration. 相似文献
20.
The influence of succinylation on the interfacial behaviour and emulsifying properties of the main storage protein (legumin) from faba beans was studied. Results of surface tension measurements and surface shear rheometry and properties of n-decane-water emulsions indicate an increased interfacial activity by succinylation whereby the 65% succinylated legumin was the most active derivative. The equilibrium surface pressure Πe increased from 16.6 to 20.21 mN m−1 and the critical association concentration, i.e. the subphase concentration at which the plateau of Πe was reached, strongly decreased with succinylation from 76.6 × 10−6 to 0.84 × 10−6 g ml−1. Spread and adsorbed films of legumin exhibited purely viscous behaviour under shear stress whereby the viscosity strongly increased with succinylation (from 7.93 to 93.36 μN s m−1). The droplet size of legumin-stabilized emulsions decreased and the coalescence stability increased with succinylation. The comparison with acetylated legumin supports the view that the dissociated but rather globular subunit is the most interfacially active component of acylated legumin. 相似文献
|