Showing papers in "Science China-chemistry in 2005"

Relationships of surface oxygen vacancies with photoluminescence and photocatalytic performance of ZnO nanoparticles

Abstract: The ZnO nanoparticles are prepared by a precipitation process, and also are characterized by means of the modern testing techniques such as XPS, ESR, SPS and PL. The activity of the as-prepared ZnO is evaluated in the photocatalytic oxidation of gas phase n-C7H16. The relationships of surface oxygen vacancies (SOV) with photoluminescence (PL) and photo-catalytic performance are discussed in details. The results show that the smaller the particle size, the larger the SOV content, the stronger the PL signal, the higher the photocatalytic activity, in-dicating that the SOV, PL and photocatalytic activity have inherent relationships. This was because of the reasons that the PL signal is attributed to the free and binding excitons resulting from the SOV, while the SOV is favorable for a photocatalytic oxidation reaction since the SOV can easily capture the photoinduced electrons, and the captured electrons had strong interac-tions with the adsorbed oxygen. In addition, the surface states of ZnO nanoparticles, arising from the SOV and oxygen species, are very abundant.

Seasonal characteristics of biomass burning contribution to Beijing aerosol

Abstract: 110 atmospheric aerosol samples collected from November 1997 to October 1998 at two monitoring sites (Ming Tomb and Temple Heaven) in Beijing were analyzed for the concentration of organic carbon (OC) and water-soluble potassium (K+) Four biomass burning episodes, namely spring farming, summer harvesting, autumn harvesting and leaf falling were identified using the tracer of K+ Biomass burning contribution to the urban aerosol OC concentration in Beijing was estimated by regression analysis of OC and K+ concentration data The slopes of regression analysis are similar at the two monitoring sites, presenting regional characteristics Severe air pollution event occurred during autumn harvesting period in 1998 with substantial secondary OC formed, in which biomass burning was one of the major emission sources Biomass burning is a prominent source of aerosol OC in Beijing and is featured by its seasonality and periodicity It may contribute as much as 30 to 60 percent of the total OC in typical cases

Formation of complexes of Rubisco-Rubisco activase from La3+, Ce3+ treatment spinach

Abstract: The complex of Rubisco and Rubisco activase from LaCl3 ™, CeCl3 ™ treated spinachin vivo is induced. SDS-PAGE result shows that the purified proteins from LaCl3 ™, CeCl3 ™ treated spinach have not only large and small subunits (55 kD, 14.4 kD) of Rubisco, but also two large subunits of 45 kD and 41 kD near the large subunits of Rubisco. Native-PAGE shows that the purified proteins from LaCl3 ™, CeCl3 ™ treated spinach have not only a band of Rubisco (560 kD), but also a band of about 1100 kD, about twice distant from Rubisco, which might be a complex of Rubisco and Rubisco activase. The purified enzyme activities from LaCl3 ™, CeCl3 ™ treated spinach are 1.8 and 2.8 times that of the control, the intensities of absorption and fluorescence are significantly higher than that of the purified Rubisco from the control, and the total sulfhydryl groups and available sulfhydryl groups are 36–39 ™SH per mol enzyme, 14–25 ™SH per mol enzyme more than those of the purified Rubisco from the control, respectively. The CD spectra show that the secondary structure of the purified enzyme from LaCl3 ™, CeCl3 ™ treated spinach is very different from the control. The enzyme activities from LaCl3 ™, CeCl3 ™ treated spinachin vivo are 1.5 and 1.9 times those of the control.

Chemical compositions of precipitation and scavenging of particles in Beijing

Abstract: Totally 23 precipitation samples were collected in Beijing from May to November in 2003. In order to investigate the chemical composition of precipitation samples, pH, conductivity, concentrations of water-soluble ions and organic acids were analyzed. The average pH of precipitations is 6.18, belonging to the neutral range; the average conductivity is 52.23 µS/cm, which indicates that precipitations in Beijing are obviously polluted; SO 4 2− , NO 3 − are the most abundant anions with the average concentrations of 521 and 174 µeq· L-1, respectively; the average SO 4 2− /NO 3 − equivalent ratio is 3.1, which decreases by about 15% compared with the result of 1994; NH 4 + and Ca2+ are the most abundant cations with the average concentrations of 376 and 397µeq· L-1, respectively; formic acid, acetic acid and oxalic acid are the main organic acids with the average concentrations of 4.62, 4.60 and 1.17 µeq· L-1, respectively, accounting for 2% of the overall anions. Obvious differences between concentrations before and after precipitation are also observed by SJAC (Steam Jet Aerosol Collector), which shows the removal of particles from the atmosphere by precipitation.

Molecular dynamics simulation of mechanical properties of TATB/fluorine-polymer PBXs along different surfaces

Abstract: The mechanical properties of PBXs composed of the well-known insensitive explosive TATB (1,3,5-Triamino-2,4,6-trinitrobenzene) crystal and four kinds of typical fluorine-polymers, i.e. poly (vinylidene difluoride) (PVDF), polychlorotrifluoroethylene (PCTFE), fluorine rubber (F 2311 ) and fluorine resin (F2314) individually, have been simulated by molecular dynamics (MD) method. The results show that the mechanical properties of TATB can be effectively improved by blending with a small amount of fluorine-polymers. Different mechanical properties of PBXs are obtained by putting fluorine-polymer binders parallel to different crystalline surfaces. The whole effect of im-proving mechanical properties is found to be (010)≈(100)>(001).

Local and non-local sources of airborne particulate pollution at Beijing

Abstract: A new element tracer technique has firstly been established to estimate the contributions of mineral aerosols from both inside and outside Beijing. The ratio of Mg/Al in aerosol is a feasible element tracer to distinguish between the sources of inside and outside Beijing. Mineral aerosol, inorganic pollution aerosol mainly as sulfate and nitrate, and organic aerosol are the major components of airborne particulates in Beijing, of which mineral aerosol accounted for 32%―67% of total suspended particles (TSP), 10%―70% of fine particles (PM 2.5 ), and as high as 74% and 90% of TSP and PM 2.5 , respectively, in dust storm. The sources from outside Beijing contributed 62% (38%―86%) of the total mineral aerosols in TSP, 69% (52%―90%) in PM 10 , and 76% (59%―93%) in PM 2.5 in spring, and 69% (52%―83%), 79% (52%―93%), and 45% (7%―79%) in TSP, PM 10 , and PM 2.5 , respectively, in winter, while only ~20% in summer and autumn. The sources from outside Beijing contributed as high as 97% during dust storm and were the dominant source of airborne particulates in Beijing. The contributions from outside Beijing in spring and winter are higher than those in summer, indicating clearly that it was related to the various meteorological factors.

Effect of concentration on surfactant micelle shapes —— A molecular dynamics study

Abstract: Many aspects of the behavior of surfactants have not been well understood due to the coupling of many different mechanisms. Computer simulation is, therefore, attractive in the sense that it can explore the effect of different mechanisms separately. In this paper, the shapes, structures and sizes of sodium dodecylbenzenesulfonate (SDBS) micelles under different concentrations in an oil/water mixture were studied via molecular dynamics (MD) simulations using a simplified atomistic model which basically maintains the hydrophile and lipophile properties of the surfactant molecules. Above the critical micellar concentration (cmc), surfactant molecules aggregate spontaneously to form a wide variety of assemblies, from spherical to rodlike, wormlike and bilayer micelles. Changes in their ratios of the principle moments of inertia (g1/g3, g2/g3) indicated the transition of micelle shapes at different concentrations. The aggregation number of micelle is found to have a power-law dependence on surfactant concentration.

A novel method for the formylation of Grignard reagent

Abstract: A facile and efficient method for the formylation of Grignard reagent was reported, and a new approach for the preparation of aldehydes from Grignard reagent and benzimida-zolium salts was provided.

Dynamic behavior of polymer surface and the time dependence of contact angle

Abstract: Time-dependent contact angles were measured by depositing sessile drops of water on the polymer surfaces and monitoring the drop shape as a function of time. It was found that contact angles decreased sharply with contact time and the equilibrium contact angle was finally attained after a certain time. Values of starting ( θ s ) and equilibrium contact angles ( θ e ) obtained by the sessile drop method depend on polymer properties. The Wilhelmy plate technique was used to measure advancing and receding contact angles. The variations of starting ( θ s ) and equilibrium contact angles ( θ e ), advancing ( θ a ) and receding contact angles ( θ r ) have been studied on the oxidized surface of polymers containing polybutadiene block to explore the cause of time-dependence in contact angle measurement and the meaning of θ s and θ e . The results showed the linear relationships between starting ( θ s ) and advancing contact angles ( θ a ), the equilibrium ( θ e ) and receding contact angles ( θ r ). The similar relationship was also established between the contact angle hysteresis ( θ a - θ r ) and differences ( θ s - θ e ) in starting contact angles and equilibrium contact angles. Therefore, time-dependence in contact angle measurement was mainly attributed to the surface reconstruction when water drops were deposited on polymer surfaces. The starting contact angle was contributed by the hydrophobic component on polymer surface and the equilibrium contact angle mainly by the hydrophilic component of polymer. These results not only demonstrated the interdependency between two contact angle measurements, the sessile drop method and the Wilhelmy plate technique, but also provided the experimental evidence to explain the cause of time-dependent contact angle. This may also provide a new method to study dynamic behavior of polymer surface.

Simultaneous determination of nitrophenol isomers at the single-wall carbon nanotube compound conducting polymer film modified electrode

Abstract: Based on the molecular recognition ability of conductive polymer and the peculiar properties of carbon nanotubes, a novel single wall nanotubes (SWNTs) compound poly(4-aminopyridine) modified electrode (SWNTs/POAPE) is prepared at glass carbon electrode (GCE). The electrochemistry response of nitrophenol isomers is studied at the SWNTs/POAPE. The result indicates that o -, m - and p -nitrophenol are separated entirely at the SWNTs/POAPE interface. The electrode present here can be easily used to determine nitrophenol isomers simultaneously with higher sensitivity.

2D/3D-QSAR comparative study on mutagenicity of nitroaromatics

Abstract: Nitroaromatics are typical toxic organic pollutants and are ubiquitous in environment with diverse structures. They are widely used in many industries and formed during many natural and anthropogenic processes. Most of these pollutants are potentially carcinogenic and the assessment and prediction of the mutagenicity of nitroaromatics are of great interest. In this paper the structure-mutagenicity relationships of 219 nitroaromatics are investigated by molecular orbital theory based classic structure-activity relationships and comparative molecular field analysis (CoMFA). A comparison is undertaken in respect of the interpretation of mechanism and predictive ability for these two categories of QSAR approaches and highly predictive QSAR models have been developed.

Treatment of coke plant wastewater by A/O fixed biofilm system

Abstract: Coke plant wastewater was treated by an anaerobic-aerobic (A/O) biofilm system. A lab-scale experiment, during which semi-soft media were packed in both the anaerobic and the aerobic reactors, was carried out. The influence parameters, such as HRT, C/N ratio, OLR, and the recycling flow rate on the performance of the system, were studied. The results showed that a sufficient carbon source was important to the performance of bio-degradation system. The COD removal rate increased from 64.15% to 83.28% by raising C/N in wastewater from 2.5 (no external carbon source) to 5. But the effluent COD concentration was still a little higher than the discharge standard. In order to make it meet the discharge standard, a deep treatment, coagulation, was applied, which was proved as an effective method. Then the effluent COD concentration can be brought to lower than 200 mg·L−1. The NH4-N removal rate in this system was satisfactory, being higher than 99%. In addition, it was almost not affected by both C/N ratio and coagulation treatment. The results show that the system is feasible to treat coke plant wastewater.

Interface and properties of epoxy resin modified by elastomeric nano-particles

Abstract: Study on a new composite of epoxy resin/elastomeric nano-particles (ENP) is reported in this paper, which shows that, in comparison with pure epoxy resin and epoxy toughened with CTBN, the composites of epoxy resin/carboxylic nitrile-butadiene ENP and epoxy resin/styrene butadiene vinyl-pyridine ENP possess both higher toughness and heat resistance. Both ENPs used in the study have an average size of less than 100 nm. Study on the epoxy network’s morphology and interface properties suggests that due to the chemical reaction between ENP and epoxy resin and more hydrogen bonds between nitrile groups of the rubber and hydroxyl groups of the epoxy resin, stronger interaction at the larger interface may lead to the observed excellent properties of the epoxy resin toughened with ENP.

Study on patterns and chemical features of NO effect on marine phytoplankton growth

Abstract: This article discusses the patterns of NO effect on marine phytoplankton growth from chemical perspective. The experimental results of four algae, which are Platymonas halgolandica var. tsingtaoensis, Platymonas subcordiformis, Skeletonema costatum and Nitzschia closterium farma minutissima, are as follows: (i) In f/2 medium or f/50 medium, the growth of these four algae was obviously promoted or inhibited when nitric oxide of different concentrations was added once or twice each day during the cultivation; (ii) The NO effects on the growth of marine phytoplankton are in normal distribution. Different phytoplankton has different optimum NO concentration, which is consistent with the influence of NO on the growth of high plants; (iii) The effect of NO on Platymonas halgolandica var. tsingtaoensi, which is a food alga, is different from that on the red tide algae Skeletonema costatum and Nitzschia closterium farma minutissima. The authors put forward a new opinion that every alga has its own NO threshold concentration. All the above results may provide new clues to understand the formation of red tide.

Status of study on biological and toxicological effects of nanoscale materials

Abstract: Because the physical and chemical properties of nanosized materials mostly differ from the existing microsized materials, their potential impacts on human health and the environment will be topics under the serious discussions in press and in a number of international scientific journals. We analyze and summarize the existing data of the experimental study on the biological activities and adverse effects of nanoscale materials/particles including single wall carbon nanotubes, multi wall carbon nanotubes, titanium oxide and iron powders. Though some biological behaviors of nanoscale materials observed cannot be understood on the basis of the current knowledge, as the existing data are mostly preliminary, it is too early to make some exclusive conclusions on biological activities (or the toxicity) of any of nanoscale materials. The experimental techniques, the current topics, and the future research directions for this new research field are also discussed.

Surface effects of monolayer-protected gold nanoparticles on the redox reactions between ferricyanide and thiosulfate

Abstract: Electron transfer through the self-assembled monolayers (SAMs) on gold nanoparticles is investigated by using the monolayer protected gold nanoclusters (MPCs) as electron-transfer mediators. 3-Mercaptopropionic acid (MPA) and 11-meraptoundecanoic acid (MUA) MPCs were employed to catalyze the redox reaction between potassium ferricyanide and sodium thiosulfate. The catalytic mechanism was proposed that the MPCs act as diffusing electron-mediators and electron transfers to and from the MPCs surface. Therefore the electron transfer rate through the capping layers would be proportional to the MPCs catalyzed reaction rate, which was monitored by the UV absorbance of ferricyanide. The calculated apparent rate constant was orders of magnitude smaller than that of the maximum of tunneling current, which was attributed to the splited energy level of the nanoscale particles.

Fe 3 O 4 /Au composite nano-particles and their optical properties

Abstract: Fe 3 O 4 /Au composite particles with core/shell structure were prepared by reduction of Au 3+ with hydroxylamine in the presence of an excess of Fe3O4 as seeds. The resultant colloids, with an average diameter of less than 100 nm, were obtained; the remaining non-reacted Fe 3 O 4 seeds can be removed by treatment with diluted HCl solution. The Fe 3 O 4 /Au colloids exhibit a characteristic peak of UV-visible spectra, which largely depend on the size of the particle and the suspension medium. The localized surface plasmon resonance peaks red shift and broaden with increased nanoparticle diameter or increased solvent ionic strength. The optical property is very important in the establishment of means for the detection of biomolecules.

Absorption, fluorescence and resonance Rayleigh scattering spectral characteristics of interaction of gold nanoparticle with safranine T

Abstract: The interaction between gold nanoparticle and safranine T (ST) has been studied with resonance Rayleigh scattering (RRS) spectra, absorption and fluorescence spectra. In the pH 5 solution, citrate [(H2L)2−] self-assembles on the surface of positively-charged gold nanoparticle, which results in the [(Au) n (H2L) m ] x− complex. In other words, one of carboxylate oxygens in (H2L)2− moves inward and combines with gold nanoparticle. The other carboxylate oxygens moves outward to form a supermolecular complex anion with x negative charges. Then by virtue of electrostatic attraction, hydrophobic force and charge transfer action, the complex anion binds with ST cation to form a new ion-association complex. Here (H2L)2- acts as a bridge. The formation of the complex results in the significant enhancement of RRS intensity, the appearance of new RRS spectrum, the red shift of plasma absorption band of gold nanoparticle as well as the decrease in the absorbance and fluorescence quenching for safranine T. In this work, the interaction between gold nanoparticle and ST on the RRS, absorption and fluorescence spectra has been investigated. The reason why RRS intensity increases greatly and the reaction mechanism have been inquired. The results show that RRS spectra can not only be used to study nanoparticle and reaction product, but also are a sensitive means to characterize and detect nanoparticles.

Host-guest complexes of cucubit[8]uril with phenanthrolines and some methyl derivatives

Abstract: The host-guest relationship between cucurbit[8]uril, phenanthrolines and some methyl substituted 1,10-phenanthrolines has been investigated by using 1H NMR spectroscopy and fluorescence spectroscopy. The results showed that phenanthrolines as molecular guests bind in the cavity and portal of cucurbit[8]uril in a ratio of 2:1 (guest to host). The phenanthroline isomers 1,10-,1,7- and 4,7- showed red shifts between 47 and 108 nm and pronounced increases in fluorescent intensity. These same isomers produced inclusion complexes with cucur-bit[8]uril which had moderate to fast exchange rates on the 1H NMR time scale. The methyl substituted 1,10-phenanthrolines studied gave stable inclusion complexes in a ratio of 2:1 which showed slow exchange rates. These guests formed п-п stacked pairs which were cavity bound but also partly protruded from only one portal forming unsymmetrical host-guest complexes. In addition, these п-п stacked pairs formed orientation isomers within the confines of the cucur-bit[8]uril cavity.

Studies on photo-electro-chemical catalytic degradation of acid scarlet 3R dye

Abstract: A new type of photo-electro-chemical catalytic reactor was designed. Cathode and anode of the new reactor were made of high-purity graphite and titanium dioxide electrode respectively. A saturated calomel electrode (SCE) was used as the reference electrode. Under the condition of ultraviolet radiation and anodic bias-voltage, acid scarlet 3R was degraded by the process of photoelectrocatalysis with titanium dioxide electrode in anodic compartment, while it was degraded by electrogenerated Fenton’s reagent and hydrogen peroxide through reducing dissolved oxygen with graphite electrode in catholyte. The new reactor made the best use of photogenerated holes and photogenerated charge on the anode of the new reactor, which achieved the purpose of degrading acid scarlet 3R in the cathodic and anodic compartments simultaneously, i.e. “two electrodes and double effect”. The experimental results showed that, compared with other photoelectrocatalysis reactors (“two electrodes and single effect” reactor), the new reactor has obviously enhanced the degradation of acid scarlet 3R dye. With the concentration of the dye being 30 mg · L−1 in water, under the operating conditions that when the inert supporting electrolyte concentration was 0.02 mol · L−1 sodium sulfate, initial solution pH = 3, and cathodic potential −E c = 0.66 V, the highest decolorizing efficiency of 92% was accomplished in cathodic compartment, and that of 60% in anodic compartment.

Distinguishing malignant from normal stomach tissues and its in vivo, in situ measurement in operating process using FTIR Fiber-Optic techniques

Abstract: Gastric tissue samples were studied using mid-IR fiber-optic attenuated total reflectance (ATR) spectroscopy. FTIR spectra of 90 tissue samples from 48 patients, including 32 normal and 58 malignant tissue samples, were chosen as examples. Malignancy was usually characterized by the absence of CH and C=O bands, a weak amide II band near 1545 cm-1, a shift of the amide I band to lower wave number, a decrease in the ∼1450 cm-1 peak to less than the ∼ 1400 cm-1 peak. Subtraction spectra indicate that the amide I and amide II bands of normal and malignant tissues have larger differences in peak positions and relative intensities. The statistical analysis results confirm this conclusion. The results indicate that FTIR fiber optic techniques provide important information about cancerous tissue of the stomach, which can be used to differentiate the malignant tissue from the normal tissue. Based on the above results we successfully realize the detection of the tumor tissues of digestive tract in vivo and in situ. And the results of detection cancer near operating room and in vivo and in situ in the operating room are consistent with the conclusions for the samples stored in liquid N2, which is the basis for the clinical application.

Gas hydrate fast nucleation from melting ice and quiescent growth along vertical heat transfer tube

Abstract: During the observation of HCFC141b gas hydrate growth processes outside a vertical heat transfer tube, two exciting phenomena were found: fast nucleation of gas hydrate from melting ice, and the spontaneous permeation of water into the guest phases along the surface of heat transfer tube to form gas hydrate continuously. These two phenomena were explained with Zhou & Sloan’s hypothesis and the theory of surface free energy respectively, and a novel method of gas hydrate formation was presented—gas hydrate fast nucleation from melting ice and quiescent growth along heat transfer tube. There is no mechanic stirring in this method, the formed gas hydrates are compact, the ratio of unreacted interstitial water is little, which overcome the drawback of high energy cost and high ratio of unreacted interstitial water among the formed gas hydrates in the system with mechanic stirring. This finding will benefit the gas hydrate application technologies such as natural gas storage technology or cool storage technology with gas hydrate.

Adsorption behavior of hexadecyltrimethylammonium bromide (CTAB) to mica substrates as observed by atomic force microscopy

Abstract: Atomic force microscopy is employed to study the adsorption behavior of CTAB to mica surfaces. Results show that conformational transitions from globular micelles?→ cylindrical micelles?→ flat films are observed in the process of the adsorption of CTAB to mica at twice the bulk critical concentration. However, in 0.5 cmc CTAB solution, the adsorbed CTAB molecules to mica form the layered film structures, and apparent conformational transitions do not appear. Meanwhile, the phenomena of the adsorption of CTAB to mica and the dissociation of mica surfaces are periodically observed.

Studies of poly-L-lysine-starch nanoparticle preparation and its application as gene carrier

Abstract: Anion starch nanoparticle (StNP) with a diameter of 50 nm was prepared in wa- ter-in-oil microemulsion, with soluble starch as raw materials and POCl3 as crosslinking agent. PLL-StNP was prepared by linking poly-L-lysine (PLL) on the surface of StNP. At the same time, the size of PLL-StNP and its stability in aqueous solution were checked by AFM. The analysis of plasmid DNA binding, DNase I enzymatic degradation, toxicity and transfection were done. We discovered that PLL-StNP may be used as non-virus nanoparticle gene carrier. And we devel- oped the method of preparing PLL-StNP gene carrier and used it in cell transfection. As non-virus gene carrier, PLL-StNP has some advantages, such as large load of DNA, high transfection effi- ciency, low cell toxicity and biodegradability.

Theory on the molecular characteristic contour (II) —— Molecular intrinsic characteristic contours of several typical organic molecules

Abstract: The molecular intrinsic characteristic contour (MlCC) is defined based on the classical turning point of electron movement in a molecule. Three typical organic molecules, i.e. methane, methanol and formic acid, were employed as examples for detailed introduction of our method. Investigations on the cross-sections of MlCC provide important information about atomic size changing in the process of forming molecules. The electron density distributions on the MlCCs of these molecules were calculated and shown for the first time. Results showed that the electron density distribution on the MlCC correlates closely with molecular chemical properties, and it provides a new insight into molecular boundary.

Stochastic bi-resonance induced by external noise for Ca 2+ signaling in hepatocytes

Abstract: The influence of external noise on intracellular Ca 2+ oscillations dynamics in a single cell of rat hepatocytes is studied. The coherence of noise-induced intracellular Ca 2+ oscillations reached two maxima for multiple external noise intensity, indicating the occurrence of external noise stochastic bi-resonance (SBR). This phenomenon is compared with our previous result that was induced by internal noise. Additionally, the deterministic bifurcation character of the system was also discussed.

Sol-gel preparation and spectroscopic study of the pyro-phanite MnTiO 3 nanoparticles

Abstract: The nanosized xerogel of titanium dioxide (TiO 2 ) and manganese oxides (MnO 2 , Mn 2 O 3 , Mn 3 O 4 ) was prepared by the sol-gel method using manganese chloride (MnCl 2 ·4H 2 O) and titanium isopropoxide (Ti(O-iPr)4) as precursors in cetyltrimethylammonium bromide (CTAB)/ ethanol/H 2 O/HCl micelle solutions, following the calcinations of the produced powders at differ-ence temperatures. The nanostructure and phase composition of these nanoparticles were characterized with X-ray powder diffraction (XRD), transmission electron microscopy (TEM), en-ergy dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS). The spectroscopic characterizations of these nanoparticles were also done with UV-Vis spectroscopy and laser Raman spectroscopy (LRS). XRD patterns show that the pyrophanite MnTiO 3 phase was formed at the calcinations temperature of 900℃. The TEM images show that the nanoparti-cles are almost spherical or slight ellipose and the sizes are 50 nm on average. The UV-Vis spectra show that the nanosized MnTiO 3 have significant absorption bands in the visible region. There are new absorption peaks of MnTiO 3 nanoparticles in LRS compared with the pure TiO 2 powder.

Effects of modified kaolin on the crystallization property of PP/Kaolin nanocomposites

Abstract: Modified kaolin-filled polypropylene was prepared by blending different kinds of modified kaolin intercalated master batches with polypropylene. The microstructure of PP/ Kaolin was studied with X-ray diffraction (XRD) patterns and transmission electron microscopy (TEM) photos. The effects of the organic kaolin master batches on the crystallization property of polypropylene were investigated by means of non-isothermal differential scanning calorimetry analysis (DSC) and polarized light microscopy (PLM). Non-isothermal crystallization kinetics of polypropylene was studied by the use of modified Avrami Equation improved by Jeziorny. The results indicate that some organic kaolin can be exfoliated by polypropylene, proved by an invisible 001 peak on XRD pattern and individual layer on transmission electron microscopy (TEM) photos, and the heterogeneous nucleus increased with the addition of modified kaolin, proved by the PLM photos. The filled polypropylene crystallizes fastest at 395 K. The results also show that organic kaolin master batches not only can effectively accelerate the heterogeneous nucleation of polypropylene but also can increase the rate of crystallizing point and the temperature of crystallization. However, the rate constant of crystallization remains unchanged.

The two steps thermal decomposition of titanium hydride and two steps foaming of Al alloy

Abstract: Two steps foaming (TSF) technique was proposed to prepare shaped Al alloy foam. Based on the thermal decomposition kinetics equation of titanium hydride, the relationship between two steps thermal decomposition kinetics of titanium hydride and two steps foaming Al alloy melt was studied. Two steps thermal decomposition curve of titanium hydride under increasing and constant temperature was calculated respectively. The hydrogen mass needed in the second foaming step was also calculated. Results showed that the hydrogen mass of the second thermal decomposition of titanium hydride is enough for the second foaming step in the condition of as-received Al melt foaming. Experimental and theoretical results indicate that two steps foaming technique can be used to prepare Al alloy foam with high porosity, shaped components and sandwich with Al alloy foam core.

Molecular modeling of the inhibitory mechanism of copper(II) on aggregation of amyloid β-peptide

Abstract: Aggregation of amyloid β-peptide (Aβ) into insoluble fibrils is a key pathological event in Alzheimer’s disease (AD). Under certain conditions, Cu(II) exhibits strong inhibitory effect on the Zn(II)-induced aggregation, which occurs significantly even at nearly physiological concen-trations of zinc ion in vitro . Cu(II) is considered as a potential factor in the normal brain preventing Aβ from aggregating. The possible mechanism of the inhibitory effect of Cu(II) is investigated for the first time by molecular modeling method. In the mono-ring mode, the Y10 residue promotes typical quasi-helix conformations of Aβ. Specially, [Cu-H13(Nπ)-Y10(OH)] complex forms a local 3.0 10 helix conformation. In the multi-ring mode, the side chains of Q15 and E11 residues collaborate harmoniously with other chelating ligands producing markedly low energies and quasi-helix conformations. [Cu-3N-Q15(O)-E11(O1)] and [Cu-H13(Nπ)-Y10(OH)] complex with quasi-helix conformations may prefer soluble forms in solution. In addition, hydro-gen-bond interactions may be the main driving force for Aβ aggregation. All the results will pro-vide helpful clues for an improved understanding of the role of Cu(II) in the pathogenesis of AD and contribute to the development of an “anti-amyloid” therapeutic strategy.