The influence of core-shell structured modifiers on the toughness of poly (vinyl chloride)

The core-shell structured grafted copolymer particles of polybutadiene grafted polymethyl methacrylate (PB-g-PMMA, MB) were prepared by emulsion polymerization. The MB particles were used to modify poly (vinyl chloride) (PVC) by melt blending. The mechanical properties of the PVC blends were investigated. The micro-morphology of the PVC blends was observed by scanning electron microscopy (SEM). The results indicated that the samples with the best impact strength could be obtained when the core-shell weight ratio of PB to PMMA is lower than 93:7, the mechanical properties correlated well with SEM morphologies, the addition of modifier with the ratio core to shell of 93:7 could reduce the domain size of the dispersed phase. Furthermore, the compatibility and properties of the blends were greatly enhanced and improved. The modifier particles could be well dispersed in the PVC matrix.

The influence of tip performance on scanning probe lithography

Scanning probe lithography (SPL), employing the tip of an atomic force microscope to mechanically pattern various materials in nanoscale region has provided a simple but significant method for making nanostructures. We use this technique for the lithography of several kinds of substrate surfaces. The tip performance has been found to be a crucial factor in the lithographic process. Four types of cantilevers are employed in nanolithography, including standard silicon nitride (DNP), tapping mode(TM) etched silicon (TESP(W)), uncoated silicon cantilever (NSC21/50) and conductive platinum/iridium-coated probe. Results demonstrate that tips with smaller spring constants can not be used for physically scribing and nanomanipulating in our experiment. The possible mechanism of our experiment is discussed.

Reversible B/Z-DNA transition under the low salt condition and non-B-form polydApolydT selectivity by a cubane-like europium-L-aspartic acid complex

We report here that a cubane-like europium-L-aspartic acid complex at physiological pH can discriminate between DNA structures as judged by the comparison of thermal denaturation, binding stoichiometry, temperature-dependent fluorescence enhancement, and circular dichroism and gel electrophoresis studies. This complex can selectively stabilize non-B-form DNA polydApolydT but destabilize polydGdCpolydGdC and polydAdTpolydAdT. Further studies show that this complex can convert B-form polydGdCpolydGdC to Z-form under the low salt condition at physiological temperature 37 degrees C, and the transition is reversible, similar to RNA polymerase, which turns unwound DNA into Z-DNA and converts it back to B-DNA after transcription. The potential uses of a left-handed helix-selective probe in biology are obvious. Z-DNA is a transient structure and does not exist as a stable feature of the double helix. Therefore, probing this transient structure with a metal-amino acid complex under the low salt condition at physiological temperature would provide insights into their transitions in vivo and are of great interest.

Investigation of the influence on conformational transition of DNA induced by cationic lipid vesicles

Recent studies have focused on the structural features of DNA-lipid assemblies. In this paper we take nile blue A (NBA) as a probe molecule to study the influence of the conformational transition of DNA induced by didodecyldimethylammonium bromide (DDAB) cationic vesicles to the interaction between DNA and the probe molecules. We find that upon binding to DNA, a secondary conformational transition of DNA induced by the cationic liposome from the native B-form to the C-form resulted in the change of binding modes of NBA to DNA and different complexes are formed between DNA, DDAB and NBA.

The influence of nucleating agent on crystallization behavior and properties of polypropylene and its copolymer with ethylene

The influences of nucleating agent EDBS on crystallization behavior and properties of polypropylene UP) and its copolymer with a small amount (4. 48 %, molar fraction) of ethylene (CPP) were studied. DSC results indicated that the crystallization temperature of iPP and CPP samples with 0.5 % (mass fraction) EDBS obviously increased and the degree of crystallinity of these samples became higher. In addition, adding small amount of EDBS enhanced the crystallization of the low isotacticity and low molecular weight segments of the CPP. PLM results showed that their spherulite size decreased markedly, and as a result, the transmittance and haze of the films were all improved.

Measurement of the single-color three-photon resonant ionization spectrum of atomic uranium under the "equivalent wavelength effect laser" interaction

Using Nd: YAG laser (532 nm) pumped mixed-dye laser. we obtained the output of this dye enhanced at the wavelength interval equivalent to that given by the copper vapor laser pumped dye laser. This measure favored is with the measurement of single-color three-photon resonant ionization spectrum of atomic uranium in the range of 562-586 nm,which is otherwise not efficiently covered by Nd: YAG laser pumped dye laser with any single dye. Thus 140 U I energy levels were obtained and the peaks of interest 575.814 nm and 575.836 rim were well resolved and their relative intensity determined.

Conformational analysis of 2,2 '-bithiophene under interaction of external electric field defined by point charges

Conformational analysis of 2,2'-bithiophene (BT) under the influence of an electric field (EF) constructed by point charges has been performed by using semi-empirical Austin Model 1 (AM1) and Parametric model number 3 (PM3) calculations. When the EF perpendicular to the molecular conjugation chain is applied, both AM1 and PM3 calculations show an energy increase of the anti-conformation. AM1 predicts that the global minimum shifts to syn-conformation when the EF strength is larger than a critical value. and PM predicts that the local minimum in anti-conformation vanishes. This kind of EF effect has been ascribed to the EF and dipole moment interaction.

The influence of bond valence on bond covalency in RMn2O5 (R=La, Pr, Nd, Sm, Eu)

The relationship between bond valence and bond covalency in RMn2O5 (R = La, Pr, Nd, Sm, Eu) has been investigated by a semiempirical method. This method is the generalization of the dielectric description theory of Phillips, Van Vechten, Levine and Tanaka scheme. The results indicate that larger valences usually result in higher bond covalencies, in good agreement with the point that the excess charge in the bonding region is the origin of formation of bond covalency. Other factors, such as oxidation state of elements, only make a small contribution to bond covalency.

The influence of muffin-tin approximation on energy band gap

The influence of muffin-tin approximation on energy band gap was studied using LMTO-ASA (Linear Muffin-Tin Orbital-Atomic Sphere Approximation) approach. Since the diverse data are available for LaX(X=N, P, As, Sb), they are presented in our research as an example in order to test the reliability of our results. Four groups of muffin-tin radii were chosen, they were the fitted muffin-tin radii based on the optical properties of the crystals (the first), 1 : 1 for La : X(the second), 1.5 : 1 for La : X(the third), and a group of radii derived by making the charge in the interstitial space to be zero(the fourth). The results show that the fitted muffin-tin radii (the first group) give the best results compared with experimental values, and the predicted energy band gaps are very sensitive to the choice of muffin-tin radius in comparison with the other groups. The second and the third delivered results somewhere in between, while the fourth provided the worst results compared with the other groups. For the same crystal, with the increase of muffin-tin radius of lanthanum, the calculated energy band gaps decreased, going from semi-conductor to semimetal. This again clearly indicated the sensitivity of energy band structure on muffin-tin approximation.

The influence of heat treatment on structures of the aggregated state of polyamide-1010

The structural parameters of the aggregated state of polyamide (PA)-1010 annealed at various temperatures were computed by means of the desmearing intensity from Smalt Angle X-ray Scattering (SAXS) measurements and by using the concept of the distance distribution function. The results indicated that the structural parameters of the aggregated state were strongly dependent upon heat treatment conditions and the maximum values of the structural parameters were obtained for the samples annealed at T = 175 degrees C. The particle size Z annealed at different temperature was ranged between 8.1-12.8nm, and the values of the distance distribution function P-max(Z) were obtained when Z = 4.0-6.8 nm. Using one dimension electron density correlation function (1D EDCF) method long period (L) and thickness of the lamellar (d(0)) were estimated and were found to increase with the increase of the degree of crystallinity.

Electrochemical studies of lipophilic ion transport through BLM. The influence of sterols on its transport

Cyclic voltammetry was employed to study the influence of sterols on the lipophilic ion transport through the BLM. The mole fraction of the sterols (cholesterol, oxidized cholesterol). as referred to total lipid, was varied in a range of 0-0.8. Data demonstrate that a thin-layer model is suitable to this BLM system. By this model, the number of charges transported per lipophilic ion, the concentration of the ion in the membrane bulk phase and the aqueous/membrane phase partition coefficient could be calculated. These parameters proved that sterols had an obvious influence on the lipophilic ion transport. Cholesterol had a stronger influence on the ion transport than oxidized cholesterol. Its incorporation into egg lecithin membranes increased the partition coefficient beta of the ion up to more than 3-fold. Yet, oxidized cholesterol incorporated into egg lecithin membranes only increased the beta up to less than 2-fold, and the beta had no great variation at different oxidized cholesterol mole fractions. The higher beta obtained was partly due to the trace amount of solvent existing in the core of the lipid bilayers. At the different sterol mole fractions, combining the change of beta with the change of peak current, we also concluded that sterols had somewhat inhibiting effect on the ion transport at the higher sterols mole fraction (>0.4). These results are explained in terms of the possible change of dipole potential of the membrane produced by sterols and the decrease of the membrane fluidity caused by the condensation effect of sterols and the thinning effect caused by sterols. The substituting group (in the oxidized cholesterol) had some inhibiting effects on the ion transport at higher mole fractions (oxidized cholesterol mole fraction >0.4).

THE INFLUENCE OF GAMMA-RADIATION ON POLYAMIDE-1010 AGGREGATE STRUCTURES

The influence of gamma-radiation on polyamide 1010 aggregate structures and crystal damage were examined by using wide angle X-ray diffraction (WAXD) and small angle X-ray scattering (SAXS) techniques. The results revealed that some structural parameters of the aggregated state, the density differences and the degree of crystallinity W-c,W-x, essentially decreased with increasing radiation dose, but the specific surface O-s increased. Crosslinking and scission of irradiated polyamide 1010 samples occurred mainly in amorphous and interphase regions, and crystal damage and amorphization induced by gamma-radiation spread from the interphase and extended into the crystal phase with increasing radiation dose. This result also indicated that the (010) reflection with the hydrogen bond was more susceptible to the action of radiation.

SYNTHESIS AND PHASE-BEHAVIOR STUDIES OF 2 NEW CHIRAL LIQUID-CRYSTALS OF SCHIFF-BASE - THE INFLUENCE OF INTRAMOLECULAR HYDROGEN-BOND ON THE PHASE-BEHAVIOR

Two new chiral liquid crystals of schiff-base type have been synthesized. This series of compounds contain a-chloro acidic ester chain prepared from commercially available L-valine. Both of the compounds exhibit tilted smectic phases; their phase transitions were studied using DSC and polarized optical microscopy; the influence of intramolecular hydrogen bonds on the phase behavior was studied as well.

STUDIES ON THE COORDINATION OF TB(III) AND CA(III) WITH AMINO-ACID UNDER THE PHYSIOLOGICAL CONDITION

Tb(Ca)-glycine, Tb(Ca)-alanine, Tb(Ca)-glycine-alanine systems were studied by potentiometry (37%, I = 0.15 mol/L NaCl). The stability constants of complexes and distribution of species in ternary system were obtained. The results show Cathe stability of binary complexes, Ca>Tb for the ternary complexes. The species convert each other with changing pH values.

STUDIES ON THE PEROVSKITE-TYPE MIXED CATALYSTS OF TITANIUM SYSTEM FOR OXIDATIVE COUPLING OF METHANE - THE INFLUENCE OF CALCINATION TEMPERATURE

The correlations of the calcination temperature, structure and catalytic activity for the oxidative coupling of methane on the LiLa0.5Ti0.5O2+lambda catalysts whose main phase and major active phase is Perovskite-type ternary complex oxide LaTi1-yLiyO3-lambda have been studied. The surface and bulk structures of the catalysts were characterized by means of XRD, XPS, IR, BET and so on, The results cleary indicated that the effect of calcination temperature on the activity for the oxidative coupling of methane is twofold. On one hand, it is favorable for Li+ substitution for Ti3+ to enter into the lattice of LaTiO3 and produce more oxygen vacancies in which active oxygens are formed; however, excessively high calcination temperature make the amount of Li+ substitution for Ti3+ lower, due to a little change of structure or phases for the catalyst. On the other hand, the conversion of CH4 drops because of the decrease of surface area, when the calcination temperature is raised.