Surface of room temperature ionic liquid [bmim][PF6] studied by polarization- and experimental configuration-dependent sum frequency generation vibrational spectroscopy

Understanding and control of the surface properties such as molecular orientations are of great importance in numerous applications of ionic liquids. However, there remain discrepancies among the previous experimental and theoretical studies on the surface orientation and structures of room temperature ionic liquids(RTIL) systems. In this article, the orientation of 1-butyl-3-methylimidazolium([bmin]) cation at the air/liquid interface of a characteristic RTIL, 1-butyl-3-methylimidazolium hexafluorophosphate([bmim][PF6]), was investigated by the sum frequency generation vibrational spectroscopy(SFG-VS). Detailed polarization and experimental configuration analyses of the SFG-VS spectra showed the possibility of a small spectral splitting in the CH3 symmetric stretching region, which can be further attributed to the probable existence of multiple orientations for the interfacial [bmim] cations. In addition, the(N)–CH3 vibrations were absent, ruling out the prediction by several recent molecular dynamics simulations which state that portions of the [bmim] cations orient with a standing-up(N)–CH3 group at the ionic liquid surface. Hence, new realistic theoretical models have to be developed to reflect the complex nature of the ionic liquid surface.     

Scale-up of bubbling fluidized beds with continuous particle flow based on particle-residence-time distribution

Few studies have investigated scale-up of the residence-time distribution（RTD） of particles in bubbling fluidized beds（BFBs） with continuous particle flow.Two approaches were investigated in this study:first,using well-known scaling laws that require changes in particle properties and gas velocity;second,using a simple approach keeping the same particles and gas velocity for different beds.Our theoretical analysis indicates it is possible to obtain similar RTDs in different BFBs with scaling laws if the plug-flow residence time(t_plug) is changed as m^0.5,where m is the scaling ratio of the bed;however,neither approach can ensure similar RTDs if t_plugis kept invariant.To investigate RTD variations using two approaches without changing t_plug,we performed experiments in three BFBs.The derivatives d?（θ）/dθ（where E（θ） is the dimensionless RTD density function and θ is the dimensionless time） in the early stage of the RTDs always varied with m-1,which was attributed to the fact that the particle movement in the early stage were mainly subject to dispersion.Using the simple approach,we obtained similar RTDs by separately treating the RTDs in the early and post-stages.This approach guarantees RTD similarity and provides basic rules for designing BFBs.     

Enhanced release of the poorly soluble drug itraconazole loaded in ordered mesoporous silica

It is known that the energy of the amorphous state of itraconazole loaded in ordered mesoporous materials is high relative to that of the crystalline state and is responsible for enhanced solubility and dissolution rate. We investigated the effects of particle size(0.7–5μm), mesostructure(2D p6 mm, cubic Ia-3d and cubic Fm-3m) and pore size(2.2–15.4 nm) of mesoporous silicas on the release performance of itraconazole. Results indicated that the release performance was not influenced by the particle sizes tested here, that the release performance increased with increasing pore diameter due to the lower probability of drug molecules colliding to recrystallize in large pores, and that the release performance was decreased in the cage-type pore structure(Fm-3m) compared to that in the cylindrical pore structures(p6mm and Ia-3d) because of the small entrance to the cagelike pores that retards the drug release.     

VIBRATION AND SOUND RADIATION OF AN ASYMMETRIC LAMINATED PLATE IN THERMAL ENVIRONMENTS

Analytical studies on the vibration and sound radiation characteristics of an asymmetric laminated rectangular plate are carried out in this paper. Theoretical formulations, in which the effects of thermal environments are taken into account, are derived for the vibration and sound radiation based on both first-order shear deformation plate theory and Rayleigh integral. It is found that the natural frequencies, the resonant amplitudes of vibration response and the sound pressure level decrease with the temperature rising. The natural frequencies of asymmetric plates are smaller than those of symmetric plates and the velocity responses of asymmetric plates are larger than those of symmetric plates.     

Hemin-histamine-montmorillonite clay conjugate as a model biocatalyst to mimic natural peroxidase

We successfully synthesized the first hemin-montmorillonite bio-conjugate with an amino acid residue to mimic natural peroxidase enzyme. Histamine was intercalated in montmorillonite by cation exchange, then a hemin molecule was loaded onto the histamine-montmorillonite with an adsorption capacity of 7.0 mg g-1. The hemin-histamine-montmorillonite conjugate shows high peroxidase activity as indicated by the oxidation of guaiacol, which is attributed to the activation of hemin by Fe–N complex formation between the imidazole group in histamine and the iron ion in the hemin molecule. Temperature- dependent peroxidase activity for this synthesized biomimetic material indicates that raising the reaction temperature could significantly enhance the activity of the conjugate. The biomimetic catalyst has good reusability; nearly 100% activity can be retained after three cycles. Because montmorillonite clay is widely distributed in the environment, this material offers great potential for in situ and ex situ remediation of many organic contaminants in surface/subsurface soils.     

Direct synthesis of propylene carbonate from propylene and carbon dioxide catalyzed by quaternary ammonium heteropolyphosphatotungstate–TBAB system

In this paper,we have developed a highly efficient method for the direct preparation of propylene carbonate from propylene and carbon dioxide(CO2) using quaternary ammonium heteropolyphosphatotungstate–quaternary ammonium halide catalytic system with anhydrous hydrogen peroxide as an oxidant through one-pot two-step process.The effects of the amount of tetrabutylammonium bromide(TBAB),the concentration of hydrogen peroxide and other reaction conditions were investigated.The catalyst system gave an optimum propylene oxide yield(91%) at75°C in oxidation step and the highest propylene carbonate yield(99%) at 140°C and 3.0 MPa in cycloaddition step.Based on the results,a reaction mechanism has been proposed.     

Preparation,characterization and hydrodesulfurization performances of Co-Ni2P/SBA-15 catalysts

A series of Co-Ni2P/SBA-15 catalysts with various Co contents, Ni2P contents and P/Ni molar ratios were prepared by impregnating nickel nitrate, diammonium hydrogen phosphate, and then cobalt nitrate into SBA-15 support followed by temperature-programmed reduction in a H2 flow. The catalyst structure was characterized by X-ray diffraction(XRD), high resolution-transmission electron microscopy(HR-TEM)and N2adsorption-desorption techniques and their catalytic performance of the hydrodesulfurization(HDS) of dibenzothiophene(DBT) was evaluated. The effects of Co contents, Ni2 P contents and P/Ni molar ratios on the catalyst structure and HDS of DBT over the Co-Ni2P/SBA-15 catalyst were investigated. The results indicated that the mesoporous structure was mainly maintained and the nickel phosphides were well dispersed in all of the characterized catalysts. The 4Co-25Ni2P/SBA-15(P/Ni = 0.8) catalyst with the Co and Ni2 P contents of 4 wt% and25 wt%, respectively, and the P/Ni molar ratio of 0.8 showed the highest catalytic performance for HDS of DBT. Under the reaction conditions of 380?C and 3.0 MPa, the DBT conversion can reach 99.62%. The HDS of DBT proceeded mainly via the direct desulfurization(DDS)pathway with biphenyl(BP) as the dominant product on all of the catalysts and the BP selectivity was slightly enhanced after the introduction of Co promoters.     

Down syndrome and parity

OBJECTIVE: To investigate the effect of parity on Down syndrome (DS). METHODS: The study was conducted on data from Northeast Italy (NEI) (1981-1996) and Sicily (ISMAC) (1991-1996) Congenital Malformation Registries. In these areas, all DS births are recorded and confirmed by chromosomal analysis; the NEI Registry also registers pregnancy terminations (TOPs) after prenatal diagnosis of DS. In order to estimate the effect of parity independently of the mother's age and to reduce the truncation effect, different age classes and three classes of parity (1, 2-4, >4) were defined. RESULTS: The study sample consisted of 1,088 consecutive newborns and 169 consecutive fetuses affected by DS. In both NEI and ISMAC samples, we found a significantly increased risk of having a DS child for multiparas > or =35 years of age. In the NEI sample, the inclusion of TOP data did not seem to modify this finding. In the ISMAC sample, a significantly reduced risk for primiparas was found at all ages. CONCLUSIONS: Our data confirm a higher risk of having a DS child in women with parity >4. As this effect is evident only in women > or =35 years age, its practical impact is null because these women are usually offered prenatal diagnosis in any case. However, the mechanisms involved, if this association is true, are very intriguing and the observation should stimulate scientific studies allowing a better knowledge of the nondisjunction mechanism.     

直流射频等离子体增强化学气相沉积类金刚石碳薄膜的结构及摩擦学性能研究

利用直流射频等离子增强化学气相沉积技术在单晶硅表面制备了类金刚石碳薄膜．采用Raman光谱、红外光谱、x射线光电子能谱和原子力显微镜等研究了薄膜的微观结构和表面形貌,在UMT-2MT型摩擦磨损试验机上考察了薄膜在不同载荷与滑动速度下的摩擦学性能。结果表明：所制备的类金刚石碳薄膜具有典型的类金刚石结构特征,薄膜均匀、致密,表面粗糙度小,硬度较高;薄膜与Si3N4陶瓷球对摩时显示出良好的抗磨减摩性能;随着试验载荷与滑动速度的提高,薄膜的摩擦系数降低,耐磨寿命降低;薄膜的减摩抗磨性能同其在Si3N4陶瓷球偶件磨损表面形成的转移膜相关。