Role of nonlocal exchange in molecular crystals: The case of two proton‐ordered phases of ice

We present a periodic density functional theory investigation of twoproton‐ordered phases of ice. Their equilibrium lattice parameters,relative stabilities, formation energies, and densities of states havebeen evaluated. Nine exchange‐correlation functionals, representativeof the generalized gradient approximation (GGA), global hybrids,range‐separated hybrids, meta‐GGA, and hybrid meta‐GGA families havebeen taken into account, considering two oxygen basis sets. Althoughthe hydrogen‐bond network of ice is well reproduced at the B3LYP,M06‐L, or LC‐ wPBE levels, formation energies are only correctlyevaluated with the two former functionals. Band gaps on the other handare only quantitatively reproduced at the B3LYP level. These resultsindicate that this last functional, a de facto reference formolecular calculations, gives in average the most accurate results forthe considered ice properties. © 2011 Wiley Periodicals, Inc. J Comput Chem, 2011     

Sensitivity improvement of 1H-15N cross-polarization at high MAS frequency applied to NMR structural characterization of organic solids

(15)N CP/MAS solid state NMR should be a method of choice to obtain essential structural information on organic materials containing nitrogen atoms. However, the technique is generally not selected for the characterization of non-labelled chemical compounds, which represents the most common situation encountered by chemists. Actually, due to the poor sensitivity of (15)N the method is time-consuming and a very fine calibration is often a prerequisite to reach a sufficient signal/noise. The main drawback comes from the weakness of (15)N-(1)H dipolar couplings which leads to a splitting of the static Hartman Hahn condition into very narrow sideband conditions under MAS. Practically, it is more difficult to obtain a high enough CP transfer level on (15)N for the entire spectrum than on other more conventional nuclei like (13)C. An experimental investigation of the CP efficiency using the ramp and adiabatic CP transfer experiments is here proposed. Preliminary adjustments of experimental settings were first made on an (15)N-labeled substituted heterocyclic model system, and then applied to several other organic compounds. Particular attention was paid to the detection of non-protonated nitrogen atoms with a significant chemical shift anisotropy, which represented the least favourable case. It was experimentally demonstrated that, for these atoms, the adiabatic passage provided a much higher transfer level than the more conventional ramp sequence leading to an enhancement factor of up to 3.5 at a MAS frequency of 30 kHz. The resulting sensitivity rendered possible the detection of non-protonated nitrogen atoms at natural abundance with 2.5-mm rotors at 9.4 T.     

Solid lipid nanoparticles comprising internal Compritol 888 ATO, tripalmitin and cacao butter for encapsulating and releasing stavudine, delavirdine and saquinavir

Solid lipid nanoparticles (SLNs) with complex internal phase were fabricated for formulating stavudine (D4T), delavirdine (DLV), and saquinavir (SQV). The lipids including Compritol 888 ATO, tripalmitin, and cacao butter were stabilized by L-α-phospatidylcholine, cholesteryl hemisuccinate, and taurocholate to form SLNs. The results revealed that the morphology of SLNs was spheroidal with shallow surface pits. An increase in the weight percentage of Compritol 888 ATO increased the average diameter of D4T-entrapping SLNs and decreased that of DLV- and SQV-entrapping SLNs. Preservation at 4°C over 6 weeks slightly enhanced the size of SLNs. For a specific drug, an increase in the entrapment efficiency enlarged the nanocarriers. The order of drug in the average particle diameter and in the entrapment efficiency was SQV>DLV>D4T, in general. In addition, the dissolution of the three drugs from SLNs showed the characteristics of sustained release. The order of drug in the cumulative release percentage was D4T>DLV>SQV. SLNs containing Compritol 888 ATO, tripalmitin, and cacao butter are efficient in carrying antiretroviral agents for medicinal application.     

Synthesis of carbon-encapsulated iron nanoparticles via solid state reduction of iron oxide nanoparticles

The encapsulation of iron nanoparticles in protective carbon cages leads to unique hybrid core-shell nanomaterials. Recent literature reports suggest that such nanocomposites can be obtained in a relatively simple process involving the solid state carbothermal reduction of iron oxide nanoparticles. This approach is very attractive because it does not require advanced equipment and consumes less energy in comparison to widely used plasma methods. The presented more-in-depth study shows that the carbothermal approach is sensitive to temperature and the process yield strongly depends on the morphology and crystallinity of the carbon material used as a reductant.     

固体热载体热解霍林河褐煤实验研究

在处理量为10kg/h的粉煤-固体热载体移动床实验装置上,以循环灰为热载体对其进行了热解特性评价实验.考察了热解温度(460℃~610℃)、反应时间(6min~8min)及煤粒粒径对热解产物产率和组成的影响.结果表明,随着热解温度的升高,气体产率增大;焦油产率在520℃时达到最大值4.94%.热解煤气的热值为19.80...     

两相溶剂萃取黄连木籽油制备生物柴油

以黄连木籽为原料,采用乙醇/异己烷两相不互溶溶剂对其进行萃取处理.考察了乙醇／异己烷体积比、萃取温度和萃取时间对萃取过程的影响.通过实验确定最佳的萃取条件为,黄连木仁粉50 g,乙醇异己烷总体积300 mL,乙醇/异己烷体积比为50∶50,萃取温度40℃,萃取时间30 min.在此条件下,黄连木籽油出油率达到99.5％...     

具有不同活性中心的固体催化剂的失活模式

 An approach is suggested to distinguish different types of active sites responsible for different reactions on bifunctional catalysts. The model assumes a non-uniform vulnerability of active sites that depends on their location. Problems on the relationship between the dispersion of the active phase and selectivity are discussed. The effect of coke formation on the activity change of different sites is analyzed.     

多级孔WO3/ZrO2固体酸催化剂的制备与表征

采用复合模板表面活性剂辅助水热法一步合成了WO3/ZrO2多级孔固体酸催化剂,并应用X射线衍射、低温N2吸附-脱附、拉曼光谱及NH3程序升温脱附对催化剂进行了表征.结果表明,WO3的引入使得WO3/ZrO2催化剂的比表面积增大,表面的酸中心明显增加.在乙酸和正丁醇的酯化反应中,WO3/ZrO2多级孔固体酸催化剂表现出较...     

Composition dependence of the photocatalytic activities of BiOCl(1-x)Br(x) solid solutions under visible light

We prepared BiOCl(1-x)Br(x) (x=0-1) solid solutions and characterized their structures, morphologies, and photocatalytic properties by X-ray diffraction, diffuse reflectance spectroscopy, scanning electron microscopy, Raman spectroscopy, photocurrent and photocatalytic activity measurements and also by density functional theory calculations for BiOCl, BiOBr, BiOCl(0.5)Br(0.5). Under visible-light irradiation BiOCl(1-x)Br(x) exhibits a stronger photocatalytic activity than do BiOCl and BiOBr, with the activity reaching the maximum at x=0.5 and decreasing gradually as x is increased toward 1 or decreased toward 0. This trend is closely mimicked by the photogenerated current of BiOCl(1-x)Br(x) , indicating that the enhanced photocatalytic activity of BiOCl(1-x)Br(x) with respect to those of BiOCl and BiOBr originates from the trapping of photogenerated carriers. Our electronic structure calculations for BiOCl(0.5)Br(0.5) with the anion (O(2-), Cl(-), Br(-)) and cation (Bi(3+)) vacancies suggest that the trapping of photogenerated carriers is caused most likely by Bi(3+) cation vacancies, which generate hole states above the conduction band maximum.     

Towards a fully synthetic MUC1-based anticancer vaccine: efficient conjugation of glycopeptides with mono-, di-, and tetravalent lipopeptides using click chemistry

The membrane‐bound tumor‐associated glycoprotein MUC1 is aberrantly glycosylated in cancer cells compared with normal cells, and is therefore considered an attractive target for cancer immunotherapy. However, tumor‐associated glycopeptides from MUC1 do not elicit a sufficiently robust immune response. Therefore, antitumor vaccines were developed, which consist of MUC1 glycopeptides as the B epitopes and immune‐stimulating toll‐like receptor 2 (TLR 2) lipopeptide ligands. These fully synthetic vaccine candidates were prepared by solid‐phase synthesis of the MUC1 glycopeptides. The Pam₃Cys lipopeptide, also synthesized on solid‐phase, was C‐terminally coupled to oligovalent lysine cores, which N‐terminally incorporate O‐propargyl oligoethylene glycol acyl side chains. The MUC1 glycopeptides and lipopeptide lysine constructs were then conjugated by click chemistry to give oligovalent synthetic vaccines. Oligovalent glycopeptide–lipopeptide conjugates are considered more immunogenic than their monovalent analogues.