Deduction of static surface roughness from complex excess attenuation

Data for complex excess attenuation have been used to determine the effective surface admittance and hence characteristic roughness size of a surface comprising a random distribution of semi-cylindrical rods on an acoustically hard plane. The inversion for roughness size is based on a simplified boss model. The technique is shown to be effective to within 4%, up to a threshold roughness packing density of 32%, above which the interaction between scattering elements appears to exceed that allowed by the model.     

Density functional study of platinum polyyne monomer,oligomer, and polymer: Ground state geometrical and electronic structures

Geometries of monomers and oligomers of a platinum polyyne and its free ligands were optimized using density functional theory with B3LYP hybrid functional. The LANL2DZ basis set was used for Pt and the 6‐31G* for other atoms in geometry optimizations. The electronic structures of these compounds were analyzed using Stuttgart/Dresden ECPs (SDD) basis set for metal atoms and 6‐311G* for others. The polymerization has very little effect on the bond lengths and by introducing the metal, the acetylide bond length increases slightly. The strong overlap between metal sp_x orbitals and σp_x orbitals of acetylides results in localized σ bonding. The hybridization between the ligand pπ orbitals and the platinum dπ orbital resulted in the π‐conjugation enhancement. This conjugation enhancement causes some effects such as the highest‐occupied molecular orbital–lowest‐unoccupied molecular orbital gap reduction and charge transfer characteristic of low‐energy vertical transitions. © 2013 Wiley Periodicals, Inc.     

A Künneth formula in tensor triangulated categories

Associated with any t-structure on a tensor triangulated category is a cohomology theory for which a general Künneth formula is proved in this paper.     

Novel poly(amide-imide)s from 2,6-bis(5-amino-1-naphthoxy) pyridine

Reaction of 5-amino-1-naphthol with 2,6-dichloropyridine resulted in preparation of 2,6-bis(5-amino-1-naphthoxy) pyridine (AN). This pyridine-based ether diamine was reacted with two moles of trimellitic anhydride (TMA) to synthesize related diimide-diacid (DIDA). Direct polycondensation reaction of DIDA with different diamines in the presence of triphenyl phosphite (TPP) afforded seven different poly(amide-imide)s. All the polymers were characterized and their physical and thermal properties were studied. The inherent viscosity of the polymers was about 0.44-0.50 dl g⁻¹ and they showed high thermal stability.     

Ab initio study of atropisomers of derivatives of 1,8-di-pyridine 9H-fluorene, dibenzo[b,d]furan, 9H-carbazole and dibenzo[b,d]thiophene

Ab initio calculation at HF/6-31G^* and MP2/6-31G^* levels of theory for geometry optimization of some syn- and anti-1,8-di-pyridine 9H-fluorene, dibenzo[b,d]furan, 9H-carbazole and Dibenzo[b,d]thiophene are reported. The rotational barrier energy, heat of formation and Gibbs energy are determined for the conversion of the anti-(syn) to the syn (anti)-isomers at 25 °C in the gas phase. The models are chosen as isomers of 9H-fluorene, dibenzo[b,d]furan, 9H-carbazole and dibenzo[b,d]thiophene as scaffold with pyridine as module. Results obtained show that (at equilibrium) for most of atropisomers the syn- is favored over the anti-isomer. Moreover, the ground state structures show that the modules are not parallel to each other but are tilted away in order to increase separation and there by minimize electrostatic repulsion. In atropisomers of 9H-carbazole the isomers are showing an attraction due to the presence of nitrogen atom. Influence of the position of nitrogen atom on the magnitude of the rotational barriers in these atropisomers is also studied.     

Model theory of the regularity and reflection schemes

Abstract  This paper develops the model theory of ordered structures that satisfy Keisler’s regularity scheme and its strengthening REF (the reflection scheme) which is an analogue of the reflection principle of Zermelo-Fraenkel set theory. Here is a language with a distinguished linear order <, and REF consists of formulas of the form

用于电催化氧化甲醛的新型Ni(OH)2-X/CPE负载电极的制备

采用一种简易的方法制备了新型Ni(OH)2-X/CPE电极,并将其用于电催化氧化甲醛反应.采用扫描电镜和能量散射谱对所制Ni(OH)2-X/CPE电极进行了表征,并运用循环伏安法、电化学阻抗谱和计时电流法考察了该电极的电化学性能.结果表明,该Ni(OH)2-X/CPE电极对甲醛氧化表现出高电催化活性,这归功于X具有纳米孔结构和大的比表面积.电子传递系数和催化反应速率常数分别为0.7和6.1×104 cm3/(mol·s).该电极对甲醛氧化具有高而稳定的电催化活性,且制备重复性高,有望应用于燃料电池中.     

On-line electrochemically controlled in-tube solid phase microextraction of inorganic selenium followed by hydride generation atomic absorption spectrometry

In this work, for the first time, a rapid, simple and sensitive microextraction procedure is demonstrated for the matrix separation, preconcentration and determination of inorganic selenium species in water samples using an electrochemically controlled in-tube solid phase microextraction (EC-in-tube SPME) followed by hydride generation atomic absorption spectrometry (HG-AAS). In this approach, in which EC-in-tube SPME and HG-AAS system were combined, the total analysis time, was decreased and the accuracy, repeatability and sensitivity were increased. In addition, to increases extraction efficiency, a novel nanostructured composite coating consisting of polypyrrole (PPy) doped with ethyleneglycol dimethacrylate (EGDMA) was prepared on the inner surface of a stainless-steel tube by a facile electrodeposition method. To evaluate the offered setup and the new PPy-EGDMA coating, it was used to extract inorganic selenium species in water samples. Extraction of inorganic selenium species was carried out by applying a positive potential through the inner surface of coated in-tube under flow conditions. Under the optimized conditions, selenium was detected in amounts as small as 4.0 parts per trillion. The method showed good linearity in the range of 0.012–200 ng mL⁻¹, with coefficients of determination better than 0.9996. The intra- and inter-assay precisions (RSD%, n = 5) were in the range of 2.0–2.5% and 2.7–3.2%, respectively. The validated method was successfully applied for the analysis of inorganic selenium species in some water samples and satisfactory results were obtained.     

Soluble and thermally stable polyamides bearing 1,1′-thiobis(2-naphthoxy) groups

A new-type of sulfide containing diacid (1,1′-thiobis(2-naphthoxy acetic acid)) was synthesized from 2-naphthol in three steps. Reaction of 2-naphthol with sulfur dichloride afforded 1,1′-thiobis(2-naphthol) (TBN). 1,1′-Thiobis(2-naphthoxy acetic ester) (TBNAE) was successfully synthesized by refluxing the TBN with methylcholoroacetate in the presence of potassium carbonate. The related diacid was synthesized by basic solution reduction of TBNAE. The obtained diacid was fully characterized and used to prepare novel thermally stable poly(sulfide ether amide)s via polyphosphorylation reaction with different aromatic diamines. The properties of these new polyamides were investigated and compared with similar polyamides. These polyamides showed inherent viscosities in the range of 0.39-0.87 dL g⁻¹ in N,N-dimethylacetamide (DMAc) at 30 °C and at a concentration of 0.5 g dL⁻¹. All the polyamides were readily soluble in a variety of polar solvents such as DMAc and tetrahydrofuran (THF). These polyamides showed glass transition temperature (T_g) between 241-268 °C. Thermogravimetric analysis measurement revealed the decomposition temperature at 10% weight loss (T₁₀) ranging from 441- 479 °C in argon atmosphere.     

Ionic liquid-modified silica-coated magnetic nanoparticles; promising anion-exchange sorbent for extraction of Cr(VI)

In the present study, ionic liquid-modified silica-coated magnetic nanoparticles (MNPs) were synthesised and applied as a new anion-exchange sorbent for extraction and determination of Cr(VI) followed by inductively coupled plasma atomic emission spectrometry. The characterisation of MNPs was carried out by scanning electron microscope, Fourier transform infrared and vibrating sample magnetometer. Experimental design and response surface methodology were used for optimisation of different parameters which affect extraction efficiency of Cr(VI). Under the optimised conditions, extraction recoveries within the range of 25–33% with relative standard deviations (RSD%, n = 4) within the range of 3.0–5.0% were obtained. The limit of detection was found to be 0.1 µg L^?1. The linearity was studied in the range of 0.5-200 µg L^?1 with the determination coefficient of 0.9958. Also, calculated Errors% for determination of Cr(VI) in the range of 5-15 depict that the method offers acceptable accuracy for analysis of Cr(VI). The method was successfully applied for extraction and determination of Cr(VI) selectively in some tannery waste water samples.