Influence of superalloy substrate roughness on adhesion and oxidation behavior of magnetron-sputtered NiCoCrAlY coatings

The present study has been conducted in order to determine the influence of superalloy substrate roughness on adhesion and oxidation behavior of magnetron-sputtered NiCoCrAlY coatings. Six types of coating samples with different substrate roughness were tested. The surface roughness and real surface area of both the substrates and coatings were studied by atomic force microscopy (AFM) techniques. The scratch tests performed at progressive loads were employed to evaluate the adhesion of the coatings. Cyclic oxidation tests were performed at 1100 °C in air for 50 cycles, each cycle consisting of 1 h heating in the tube furnace followed by 15 min cooling in the open air. The AFM measurements exhibit that the surface roughness of the sputtered NiCoCrAlY coating increases with the increasing of the superalloy substrate roughness. The NiCoCrAlY coatings present slightly lower roughness than the corresponding superalloy substrate. The scratch adhesion tests indicate that the coatings on substrates with a smoother surface possess better adhesion than on those with a rougher surface. Both the real surface area and oxidation weight gain of the coatings decrease with the decreasing of the superalloy substrate roughness. The NiCoCrAlY coating sputtered on the superalloy substrate with lower roughness provides relatively higher antioxidant protection than that provided by the coating with rougher substrate.     

Self-organized critical model for protein folding

The major factor that drives a protein toward collapse and folding is the hydrophobic effect. At the folding process a hydrophobic core is shielded by the solvent-accessible surface area of the protein. We study the fractal behavior of 5526 protein structures present in the Brookhaven Protein Data Bank. Power laws of protein mass, volume and solvent-accessible surface area are measured independently. The present findings indicate that self-organized criticality is an alternative explanation for the protein folding. Also we note that the protein packing is an independent and constant value because the self-similar behavior of the volumes and protein masses have the same fractal dimension. This power law guarantees that a protein is a complex system. From the analyzed data, q-Gaussian distributions seem to fit well this class of systems.     

Assessment of pulmonary artery stiffness using velocity-encoding magnetic resonance imaging: evaluation of techniques

The loss of pulmonary artery (PA) compliance has significant pathophysiological effect on the right ventricle. Noninvasive and reliable assessment of PA wall stiffness would be an essential determiner of right heart load and a clinically useful factor to assess cardiovascular risk. Two MRI techniques have been proposed for assessing PA stiffness by measuring pulse wave velocity (PWV): transit time (TT) and flow area (QA). However, no data are available that compares the two techniques and evaluates their performance, especially over a wide range of PWV values or at 3.0-T, which is the purpose of the present study. Thirty-three patients with different heart conditions were imaged using optimized high-temporal resolution and high-spatial resolution velocity-encoding MRI sequences. Statistical analysis was conducted to study intermethod, interobserver and intraobserver variabilities. The PWV measurements using TT and QA techniques showed good agreement (P>0.1). The Bland-Altman analysis showed negligible differences between the two methods (mean±S.D.=0.11±0.35 m/s, correlation coefficient r=0.94). The repeated measurements showed low interobserver and intraobserver variabilities, although the S.D. of the differences was larger in the QA technique. The mean±S.D. of the TT/QA measurement differences were −0.05±0.2/0.0±0.36 m/s and 0.02±0.26/0.02±0.39 m/s for the interobserver and intraobserver differences, respectively. In conclusion, each technique has its own advantages and disadvantages. The two techniques result in similar measurements, although the QA method is more subjective due to its dependency on operator intervention.     

Area integral functions for sectorial operators on L spaces

Area integral functions are introduced for sectorial operators on L^p-spaces. We establish the equivalence between the square and area integral functions for sectorial operators on L^p spaces. This follows that the results of Cowling, Doust, McIntosh, Yagi, and Le Merdy on H^infin functional calculus of sectorial operators on L^p-spaces hold true when the square functions are replaced by the area integral functions.     

Generalized area operators on L^p（R^n）

We introduce the generalized area operators by using nonnegative measures defined on upper half-spaces R＋^n＋1. The characterization of the boundedness and compactness of the generalized area operator from LP（]Rn） to Lq（IRn） is investigated in terms of s-Carleson measures with 1 〈 p, q 〈 ＋∞. In the case of p = q = 1, the weak type estimate is also obtained.     

Commutators of Littlewood-Paley Operators on Herz Spaces with Variable Exponent

Let ? ∈ L~2(S~(n-1)) be homogeneous function of degree zero and b be BMO functions. In this paper, we obtain some boundedness of the Littlewood-Paley Operators and their higher-order commutators on Herz spaces with variable exponent.     

Preparation and characterization of carbon aerogel microspheres by an inverse emulsion polymerization

Carbon aerogel (CA) microspheres have been successfully synthesized by an inverse emulsion polymerization and characterized by scanning electron microscopy (SEM), N₂ sorption isotherm and X-ray diffraction (XRD). The results show that the size and pore characteristics of carbon microsphere obviously depend on stirring speed and concentration of surfactant in the emulsion polymerization process. The resultant CA microspheres are amorphous carbon structure with the size ranging from about 2 to 50 μm by changing the stirring speed. CA microspheres with S_BET of 414-603 m² g^− 1 and V_meso of 0.028-0.432 cm³ g^− 1 are synthesized using different SPAN80 concentrations. The results of cyclic voltammetry indicate that the CA microspheres prepared at a stirring speed of 480 rpm and at V_s/V_h = 0.01 have ideal supercapacitive behavior in 6 M KOH electrolyte, the maximum specific capacitance of the electrode reaches 180 F g^− 1.     

Adsorption of Methylene Blue on Montmorillonite

ABSTRACT

Adsorption of Methylene Blue ( MB) on Na-, Fe- and Al-montmorillonite suspensions at 298.15 K were studied. The effect of different exchangeable cation on the adsorption amount of MB was determined. The results show that methylene blue cations( MB⁺ ) replace Na? more easily than they do Fe³⁺ and Al^{3 +} The adsorption isotherms on the three montraorillonites were all of Langmuir type, except that the isouHerm of MB on Na-montmorillonite presents nonmonotonic curve at low surface coverage. The specific surface areas in suspension were calculated by( MB ^{3 +} )method, and Na^? is more effective to determine the specific surface area by MB method in suspension than Fe^{3 +} and A^{3 +} The discrepancy of the specific surface area measured by MB and BET method was discussed.     

Methods to Study Naphthenate Formation in w/o Emulsions by the Use of a Tetraacid Model Compound

Precipitation of naphthenate salts is normally a problem in the processing of acidic crude oils. In this study, the goal was to find suitable methods to investigate the interfacial reaction between tetraacid and calcium under emulsified conditions. Two different systems have been studied depending on composition and applied shear. The influence of inhibitors has been investigated and the same inhibitor was found to be the most effective one regardless of the system. Depletion of tetraacid in the oil phase was analyzed with UV-vis and HPLC. Interfacial area and droplet size in the emulsions were measured with fluorescence microscope and pulse-field gradient NMR. Since this reaction takes place over the interface, the investigation clearly documents, the importance of the total interfacial area of the emulsified system.     

华南沿海黄色粉土沉积的激光粒度分析及其成因讨论

在华南沿海地区的低矮丘陵及台地上，广泛发育一套黄色粉土堆积。对该区7个典型剖面进行系统的激光粒度分析，并与典型黄土以及研究区常见的海、河相沉积进行对比。结果表明，华南沿海各黄色粉土剖面均以10～50 μm的粗粉砂为众数粒组，<5 μm的粘粒为次众粒组，分别对应风成黄土的“基本粒组”和“挟持粒组”，岩性均属于粘土质粉砂。样品的粒度参数、粒度散点图、频率分布曲线、粒度指数特征均显示为典型的风成成因。粒度判别分析结果为负值，同样证实了黄色粉土的风成特性。华南沿海黄色粉土的各项粒度特征指标及其所反映的沉积类型、沉积环境均与我国典型黄土具有较好的可比性，而与研究区的海、河相沉积截然不同。