Some algebraic properties of hypergraphs

We consider Stanley-Reisner rings k[x ₁, …, x _n ]/I(H) where I(H) is the edge ideal associated to some particular classes of hypergraphs. For instance, we consider hypergraphs that are natural generalizations of graphs that are lines and cycles, and for these we compute the Betti numbers. We also generalize some known results about chordal graphs and study a weak form of shellability.     

Electromembrane extraction of levamisole from human biological fluids

Electromembrane extraction coupled with high-performance liquid chromatography (HPLC) and ultraviolet (UV) detection was developed for the determination of levamisole in some human biological fluids. Levamisole migrated from 4 mL of different acidized biological matrices, through a thin layer of 2-nitrophenyl octyl ether containing 5% tris-(2-ethylhexyl) phosphate immobilized in the pores of a porous hollow fiber, into a 20-μL acidic aqueous acceptor solution present inside the lumen of the fiber. The parameters influencing electromigration were investigated and optimized. Within 15 min of operation at 200 V, levamisole was extracted from different biological fluid samples with recoveries in the range of 59-65%, which corresponded to preconcentration factors in the range of 118-130. The calibration curves showed linearity in the range of 0.5-10, 0.2-10 and 0.1-10 μg/mL for plasma, urine and saliva, respectively. Limits of detection of 0.1, 0.07 and 0.05 μg/mL and limits of quantification of 0.5, 0.2 and 0.1 μg/mL were obtained for plasma, urine and saliva, respectively. The relative standard deviations of the analysis were found to be in the range of 5.6-9.7% (n = 3). Electromembrane extraction was successfully processed for determination of levamisole in plasma, urine and saliva samples.     

A simple kinetic model for oxidative coupling of methane over La_(0.6)Sr_(0.4)Co_(0.8)Fe_(0.2)O_(3-δ) nanocatalyst

A simplified kinetic model for the oxidative coupling of methane over a La0.6Sr0.4Co0.8Fe0.2O3-δ nanocatalyst is presented. The kinetic model was developed by experimental data in a catalytic micro-reactor covering a wide range of reaction conditions (0.04相似文献   

A new strategy to simultaneous microextraction of acidic and basic compounds

The simultaneous extraction of acidic and basic pollutants from water samples is an interesting and debatable work in sample preparation techniques. A novel and efficient method named ion pair based surfactant assisted microextraction (IP-SAME) was applied for extraction and preconcentration of five selected acidic and basic aromatic species as model compounds in water samples, followed by high performance liquid chromatography-ultraviolet detection. A mixture including 1 mL of ultra-pure water (containing ionic surfactant as emulsifier agent) and 60 μL 1-octanol (as extraction solvent) was rapidly injected using a syringe into a 10.0 mL water sample which formed an emulsified solution. IP-SAME mechanism can be interpreted by two types of molecular mass transfer into the organic solvent (partitioning and ion pairing for non-ionized and ionized compounds, respectively) during emulsification process. The effective parameters on the extraction efficiency such as the extraction solvent type and its volume, type of the surfactant and its concentration, sample pH and ionic strength of the sample were optimized. Under the optimum conditions (60 μL of 1-octanol; 1.5 mmol L(-1) cethyltrimethyl ammonium bromide (CTAB) as emulsifier agent and sample pH 10.0), the preconcentration factors (PFs), detection limits and linear dynamic ranges (LDRs) were obtained in the range of 87-348, 0.07-0.6 μg L(-1) and 0.1-200 μg L(-1) respectively. All of natural water samples were successfully analyzed by the proposed method.     

Adsorption properties of N<Subscript>2</Subscript>O on (6,0), (7,0), (8,0), and Al-doped (6,0) zigzag single-walled carbon nanotubes: a density functional study

Abstract  

The behavior of N₂O adsorbed on the external surface of H-capped (6,0), (7,0), (8,0), and Al-doped (6,0) zigzag single-walled carbon nanotubes was studied by using density functional calculations. Geometry optimizations were carried out at the B3LYP/6-31G* level of theory using the Gaussian 03 suite of programs. We present the nature of the N₂O interaction in selected sites of the nanotubes. Binding energies corresponding to adsorption of the N₂O are calculated to be in the range 4–21 kJ mol⁻¹. More efficient binding energies cannot be achieved by increasing the nanotube diameter. We also provide the effects of N₂O adsorption on the electronic properties of the nanotubes.     

Characterization of 5-nonylsalicylaldoxime production and the effects of modifiers on its extracting/stripping properties

The 5-nonylsalicylaldoxime or 2-hydroxy-5-nonylbenzaldoxime namely aldoxime is a strong copper extractor that is mainly used in the process of copper solvent extractions. In order to characterize the aldoxime production process and to obtain a pure substance for using in the subsequent investigations, this reagent was synthesized and instrumental analysis such as FT-IR, ¹H-NMR, and GC/MS spectra were first taken on the final product. The effects of various modifying reagents were studied on the synthesized aldoxime for improving its extracting and striping properties in the Cu (II) extraction processes. An optimum formulation of organic phase including the aldoxime and some modifier reagents was determined based on the variation of type and the concentration of the modifiers. The obtained experimental data show that the net copper transferring in a mixture of the aldoxime and modifier mainly the aliphatic alcohols (C₁₂ (40 % w/w) and C₁₄ (60 % w/w)) is greater than the aldoxime alone and greater than its other mixture.     

Development of a new and environment friendly hollow fiber-supported liquid phase microextraction using vesicular aggregate-based supramolecular solvent

Hollow fiber-based liquid phase microextraction (HF-LPME) using conventional solvents is limited by their relative instability and high volatility. The use of supramolecular solvents as a liquid membrane phase could overcome these inconveniences due to their negligible vapour pressure and high viscosity. In the present study, a novel and highly flexible method was developed based on supramolecular solvents constructed of vesicles of decanoic acid, which were used for the first time as a solvent in HF-LPME. This solvent is produced from the coacervation of decanoic acid aqueous vesicles by the action of tetrabutylammonium (Bu(4)N(+)). In this work, halogenated anilines as model compounds were extracted from water samples into a supramolecular solvent impregnated in the pores and also filled inside the porous polypropylene hollow fiber membrane. The extracted anilines were separated and determined by high-performance liquid chromatography. The technique requires minimal sample preparation time and toxic organic solvent consumption, and provides a significant advantage over conventional analytical methods. The important parameters influencing the extraction efficiency were studied and optimized utilizing two different optimization methods: one variable at a time and the Box-Behnken design. Under the optimum conditions, the preconcentration factors were in the range of 74 to 203. Linearity of the method was obtained in the range of 1.0-100 μg L(-1) with the correlation coefficients of determination (R(2)) ranging from 0.9901 to 0.9986. The limits of detection for the target anilines were 0.5-1.0 μg L(-1). The relative standard deviations varied from 3.9% to 6.0%. The relative recoveries of the three halogenated anilines from water samples at a spiking level of 20.0 μg L(-1) were in the range of 90.4-107.4%.     

PEG-mediated catalyst-free expeditious synthesis of polysubstituted anilines and benzenes via the reaction of malononitrile and β-ketoester derivatives in the presence of activated acetylenes

Poly(ethylene glycol) (PEG) has been used as a sustainable, non-volatile, and environmentally friendly reaction solvent for synthesis of functionalized anilines and benzenes via the reaction of malononitrile and β-ketoester derivatives in the presence of activated acetylenes at 80° C. No additional solvent and catalyst are required.     

DFT studies of Si- and Al-doping effects on the acetone sensing properties of BC3 graphene

In order to find a novel sensor, reactivity and sensitivity of the intrinsic, Al- and Si-doped BC₃ graphene-like sheets to an acetone molecule were investigated by using B3LYP and ωB97X-D density functional calculations. Adsorption of acetone on the intrinsic, Al- and Si-doped BC₃ sheets releases energies of about 7.2, 36.5 and 24.8 kcal/mol, respectively, using ωB97X-D. The Si-doped sheet presents high sensitivity to acetone compared with the intrinsic and Al-doped sheets indicated by the calculated geometrical structures and electronic properties for these systems. The HOMO/LUMO energy gap of Si-doped BC₃ sheet is significantly decreased from 2.20 to 1.65 eV (B3LYP), which would result in electrical conductance increment. Thus, Si-doped sheet are expected to be a potential candidate for detecting the presence of acetone.     

Decoration of carbon nanotube with size-controlled L10-FePt nanoparticles for storage media

In this work, first multi-wall carbon nanotubes (MWCNTs) with outer diameter about 20–30 nm are synthesized by a CVD method; they have been purified and functionalized with a two-step process. The approach consists of thermal oxidation and subsequent chemical oxidation. Then, monosize FePt nanoparticles along carbon nanotubes surface are synthesized by a Polyol process. The synthesized FePt nanoparticles are about 2.5 nm in size and they have superparamagnetic behavior with fcc structure. The CNTs surfaces as a substrate prevent the coalescence of particles during thermal annealing. Annealing at the temperature higher than 600 ^°C for 2 h under a reducing atmosphere (90 % Ar + 10 % H₂) leads to phase transition from fcc to fct-L1₀ structure. So, the magnetic behavior changes from the superparamagnetic to the ferromagnetic. Furthermore, after the phase transition, the FePt nanoparticles have finite size with an average of about 3.5 nm and the coercivity of particles reaches 5.1 kOe.