On Fractional Evolution Inclusion Coupled with a Time and State Dependent Maximal Monotone Operator

Set-Valued and Variational Analysis - The paper deals with second-order evolution problems driven by time and state dependent maximal monotone operators with non-Lipschitz perturbations. Systems...     

Preparation of open tubular capillary column covalently coated with polystyrene sulfonate with 4,4′-Azobis(4-cyanopentanoyl chloride) as polymerization initiator for electrochromatographic separation of alkaloids,sulfonamides, and peptides

An open tubular capillary electrochromatography column covalently bonded with polystyrene sulfonate was prepared via in situ polymerization using functionalized Azo-initiator 4,4′-Azobis(4-cyanopentanoyl chloride). Scanning electron, fluorescence, and atomic force microscopy techniques showed the formation of a relatively rough layer of polymer. In addition, –CN and C = O stretching vibrations from infrared spectroscopy proved the successful immobilization of the azo-initiator through covalent bonding and X-ray photoelectron spectroscopy confirmed the elemental composition of the formed polymer layer. The prepared column was found to be appropriate for small and medium-sized molecules separation. Compared to bare fused silica capillary column higher selectivity and resolution were obtained for the separation of alkaloids, sulfonamides, and peptides as a result of the electrostatic and pi-pi stacking interactions between the small organic molecules and the coated column without compromising the electroosmotic flow mobility. Separation efficiency was also increased compared to the bare capillary for the separation of alkaloids (about 1.5 times). Moreover, intraday, inter-day, intra-batch, and inter-batch relative standard deviation values of retention time and peak area of peptides were within 2% and 10%, respectively, indicating good repeatability of the column preparation procedure. The developed method for the covalent bonding of polymers through a functionalized azo-initiator could represent a promising stable method for the preparation of an open tubular column.     

On the minimal solution for some variational inequalities

Applying an asymptotic method, the existence of the minimal solution to some variational elliptic inequalities defined on bounded or unbounded domains is established. The minimal solution is obtained as limit of solutions to some classical variational inequalities defined on domains becoming unbounded when some parameter tends to infinity. The considered quasilinear operators are only monotone (not strictly) and noncoercive. Some related comparison principles are also investigated.     

加压毛细管电色谱法高效分离分析葛根多糖中的单糖

葛根多糖具有抗氧化、抗肿瘤等众多生物活性,对葛根多糖进行单糖组成分析对其活性研究具有重要意义。该研究利用响应面分析法考察了超声辅助提取法中液料比、超声温度、超声时间和超声功率对葛根多糖提取率的交互影响,并拟合数据得到多元二次回归方程。同时建立了柱前衍生加压毛细管电色谱检测糖类的方法,对分离8种中性单糖的色谱条件进行了探索与优化,并将此方法应用于两种葛根实际样品的单糖组成测定。响应面分析结果表明,4个试验因素中,超声温度对两种葛根多糖提取率的影响程度最大,其次为液料比,超声时间和超声功率影响程度较小。结合软件预测分析得到的最佳条件及设备实际情况,确定葛根多糖的最佳提取工艺条件为:超声温度90℃,粉葛多糖液料比20 mL/g,柴葛多糖液料比40 mL/g,超声时间30 min,超声功率180 W。优化后的色谱分离条件为:采用Halo-2.7μm核壳型C18填料毛细管色谱柱,以乙腈-50 mmol/L pH 4.1的醋酸铵水溶液(18∶82, v/v)为流动相,在250 nm波长下检测,施加电压-20 kV。在此条件下可以实现24 min内对葡萄糖等8种中性单糖衍生物的快速分离,相比传统液相色谱方法大大提升了分离检测速度和分离柱效。方法学考察表明此方法具有较好的线性关系和良好的重复性。对实际样品分离鉴定表明,粉葛多糖主要由葡萄糖、甘露糖、鼠李糖和岩藻糖组成,4种单糖物质的量之比为1.00∶0.16∶0.14∶0.07;柴葛多糖主要由葡萄糖和甘露糖组成,2种单糖物质的量之比为1.00∶0.70。该研究为单糖化合物快速高效分离检测提供了新方法,并为葛根多糖单糖组成分析提供了参考。     

Positivity and stability for some partial functional differential equations

The aim of this work is to study the stability for some linear partial functional differential equations. We assume that the linear part is non-densely defined and satisfies the Hille-Yosida condition. Using the positiveness, we give nessecary and sufficient conditions independently of the delay to ensure the uniform exponential stability of the solution semigroup. An application is given for a reaction diffusion equation with several delays. RID="h1" ID="h1"This work is supported by the Moroccan Grant PARS MI 36 and TWAS Grant under contract: No. 00-412 RG/MATHS/AF/AC.     

Reduction of PAH and soot precursors in benzene flames by addition of ethanol

A one-dimensional premixed flame model (PREMIX) and schemes resulting from the merging of validated kinetic schemes for the oxidation of the components of the present mixtures (benzene and ethanol) were used to investigate the effect of oxygenated additives on aromatic species, which are known to be soot precursors, in fuel-rich benzene combustion. The specific flames were low-pressure (45 mbar), laminar, premixed flames at an equivalence ratio of 2.0. The blended fuels were formed by incrementally adding 4% wt of oxygen (ethanol) to the neat benzene flame and by keeping the inert mole fraction (argon) and the equivalence ratio constants. Special emphasis was directed toward the causes for the concentration-dependent influence of the blends on the amount of polycyclic aromatic hydrocarbons (PAHs) formed. The effects of oxygenate addition to the benzene base flame were seen to result in interesting differences, especially regarding trends to form PAH. The modeling results indicated that the concentration of acetylene and propargyl radicals, the main PAH precursors, as well as the PAH amounts were lower in the flame of the ethanol-benzene fuel mixture than in the pure benzene flame and that all of the formed PAHs were issued from the phenyl radical. Finally, the modeling results provided evidence that the PAH reduction was a result of simply replacing "sooting" benzene with "nonsooting" ethanol without influencing the combustion chemistry of the benzene.     

Rotationally disordered phase of 1,3‐dibromo‐5‐iodo‐2,4,6‐trimethylbenzene at 293 K

In the crystal state at room temperature, the molecule of dibromoiodomesitylene (1,3‐dibromo‐5‐iodo‐2,4,6‐trimethylbenzene), C₉H₉Br₂I, is prone to strong disorder, apparently involving only the three halogen sites (occupied identically by 66.7% Br and 33.3% I). This disorder, of the rotational type according to previously published NMR measurements, corresponds to fast 2π/3 stochastic in‐plane reorientations of the whole molecule between three discernable locations. This kind of rotational disorder can be revealed for the first time by diffractometry thanks to the C_2v idealized molecular symmetry of the title compound, although it has been indirectly suspected at room temperature in other trihalogenomesitylenes of similar crystal packing but of D_3h molecular symmetry. The average endocyclic angles facing the Br/I sites and the methyl groups are 124.14 (6) and 115.85 (2)°, respectively. The angle between the normal to the aromatic ring and the normal to the (100) plane is 4.1°. TLS analysis indicates that only the aromatic ring and the methyl groups behave as a rigid body with respect to the thermal librations.