The effect of different cementing strategies and adhesive interface aging on microtensile bond strength (μTBS) of lithium disilicate ceramics to dentin

This study evaluated the effect of different cementing strategies and adhesive interface aging on microtensile bond strength (μTBS) of lithium disilicate ceramic (IPS e.max CAD) to dentin. Forty coronal dentin fragments were randomly assigned to four groups according to the cementing strategy used to bond lithium disilicate ceramic to coronal dentin surface (n = 10): U200 (self-adhesive resin cement (RC) RelyX U200®/3 M ESPE), SBU (single-step self-etching adhesive system (AS) Single Bond Universal®/3 M ESPE + RelyX ARC®/3 M ESPE RC), AdperSB (two-step etch-and-rinse AS Single Bond 2®/3 M + RelyX ARC®/3 M ESPE RC) and Scotchbond (three-step etch-and-rinse AS Scotchbond Multi-Purpose®/3 M + RelyX ARC®/3 M RC). After 48 h, the ceramic-tooth blocks were sectioned perpendicular to the adhesive interface in the form of sticks and randomly subdivided into two groups according to when they were to be submitted to μTBS testing: immediately or 6 months after storage in water. Some sticks were kept for analysis of the adhesive interface by scanning electron microscopy (SEM). The μTBS test was performed in a universal testing machine (0.5 mm/min). The data (MPa) were analyzed using split-plot ANOVA and Tukey’s test (α = 0.05). Water storage decreased μTBS in all cementing strategies. The μTBS was greatest in the Scotchbond group and lowest in the U200 group, at both storage times. No signs of interface degradation were detected under SEM after water storage. In conclusion, water storage decreased bond strength, regardless of the adhesive cementation strategy, and that the three-step adhesive system/dual-cure resin cement ultimately performed better in terms of bond strength.     

精密挤出装备的研制与应用

提出精密挤出概念 ,系统分析了影响挤出制品精度的各种因素 ,研制了一台DJ/PE32× 2 8-A型精密挤出实验装置。用该装置对LDPE料进行了初步实验 ,并与普通挤出机的实验结果进行了对比 ,结果表明该精密挤出实验装置对提高挤出制品的尺寸精度是十分有效的。     

Thermodynamic study on glycerol-fuelled intermediate-temperature solid oxide fuel cells (IT-SOFCs) with different electrolytes

In this paper, a thermodynamic analysis was carried out to provide useful information about the operation of intermediate-temperature Solid Oxide Fuel Cells (IT-SOFCs) with direct internal reforming (DIR) fuelled by glycerol. A methodology, based on the principle of minimizing the Gibbs energy of a given system, using spreadsheets and the Microsoft Excel’s Solver function, was described for DIR operation of the SOFC with oxygen ion conducting electrolyte (SOFC-O²⁻) and proton conducting electrolyte (SOFC-H⁺). The effect of temperature, fuel utilization and type of electrolyte on the equilibrium composition of the anode gas mixture as well as on the boundary of carbon formation has been investigated in the temperature range of 773–1073 K. Based on the results of this thermodynamic study, glycerol can be considered an alternative fuel with suitable characteristics for electricity generation in IT-SOFCs. Operating at carbon-free conditions, between 773 and 1073 K, with a fuel utilization of 99.99% in the anode channel outlet, glycerol-fuelled IT-SOFCs systems attain high theoretical efficiencies in the range of 80.7–89.9% (SOFC-O²⁻ case) and 90.3–96.7% (SOFC-H⁺ case). Regarding the maximum values of the average electromotive force (EMF) and efficiency, it was verified that glycerol exhibits very similar potential for power generation with ethanol. Although glycerol fed SOFC-H⁺ is superior to SOFC-O²⁻ in terms of maximum theoretical efficiency, it should be taken into account that the SOFC-H⁺ shows a greater tendency for carbon deposition than does the SOFC-O²⁻ during the operation. Besides, it was found that decreasing temperature increases the efficiency but also favors carbon formation, for both SOFC-O²⁻ and SOFC-H⁺. When the system runs at 70% of its maximum power and the partial pressure of residual hydrogen in the anode outlet is kept equal to 0.1 atm, the highest efficiency (67%) is achieved by operating an SOFC-H⁺ at 823 K.     

基于模式的XML文档关系数据库存储

基于XML的模式定义给出了一种使用关系数据库存储XML文档的方法．谊方法在存储文档的同时，使用元表以保存模式信息，并实现了模式所定义的完整性约束．对查询映射和由于XML的半结构化特性所导致的一些目前难以解决的问题，文章也进行了说明．     

Predicting attention-deficit/hyperactivity disorder and oppositional defiant disorder from preschool diagnostic assessments.

The present study examined the power of measures of early preschool behavior to predict later diagnoses of attention-deficit/hyperactivity disorder (ADHD) and oppositional defiant disorder (ODD)/conduct disorder (CD). Participants were 168 children with behavior problems at age 3 who underwent a multimethod assessment of ADHD and ODD symptoms and were followed annually for 3 years. Fifty-eight percent of 3-year-old children with behavior problems met criteria for ADHD and/or ODD/CD 3 years later. Using a diagnostic interview and rating scales at age 3, the authors could accurately predict later diagnostic status for 3/4 of children for ADHD and for 2/3 of children for ODD/CD. Predictive power of the best models did not increase significantly at age 4 and age 5 compared with age 3. Results provide support for the validity of early diagnoses of ADHD, although caution is needed in making diagnoses because a significant minority of children with early hyperactivity and inattention do outgrow their problems. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Catalyst Design by NH4OH Treatment of USY Zeolite

Hierarchical zeolites are a class of superior catalysts which couples the intrinsic zeolitic properties to enhanced accessibility and intracrystalline mass transport to and from the active sites. The design of hierarchical USY (Ultra‐Stable Y) catalysts is achieved using a sustainable postsynthetic room temperature treatment with mildly alkaline NH₄OH (0.02 m ) solutions. Starting from a commercial dealuminated USY zeolite (Si/Al = 47), a hierarchical material is obtained by selective and tuneable creation of interconnected and accessible small mesopores (2–6 nm). In addition, the treatment immediately yields the NH₄⁺ form without the need for additional ion exchange. After NH₄OH modification, the crystal morphology is retained, whereas the microporosity and relative crystallinity are decreased. The gradual formation of dense amorphous phases throughout the crystal without significant framework atom leaching rationalizes the very high material yields (>90%). The superior catalytic performance of the developed hierarchical zeolites is demonstrated in the acid‐catalyzed isomerization of α‐pinene and the metal‐catalyzed conjugation of safflower oil. Significant improvements in activity and selectivity are attained, as well as a lowered susceptibility to deactivation. The catalytic performance is intimately related to the introduced mesopores, hence enhanced mass transport capacity, and the retained intrinsic zeolitic properties.     

Stabilization and Encapsulation of Gold Nanostars Mediated by Dithiols

Surface chemistry plays a pivotal role in regulating the morphology of nanoparticles, maintaining colloidal stability, and mediating the interaction with target analytes toward practical applications such as surface‐enhanced Raman scattering (SERS)‐based sensing and imaging. The use of a binary ligand mixture composed of 1,4‐benzenedithiol (BDT) and hexadecyltrimethylammonium chloride (CTAC) to provide gold nanostars with long‐term stability is reported. This is despite BDT being a bifunctional ligand, which usually leads to bridging and loss of colloidal stability. It is found however that neither BDT nor CTAC alone are able to provide sufficient colloidal and chemical stability. BDT‐coated Au nanostars are additionally used as seeds to direct the encapsulation with a gold outer shell, leading to the formation of unusual nanostructures including semishell‐coated gold nanostars, which are characterized by high‐resolution electron microscopy and electron tomography. Finally, BDT is exploited as a probe to reveal the enhanced local electric fields in the different nanostructures, showing that the semishell configuration provides significantly high SERS signals as compared to other core–shell configurations obtained during seeded growth, including full shells.     

FinFET for high sensitivity ion and biological sensing applications

A double-gate (DG) fin field effect transistor (FinFET) is discussed as new label-free ion and biological sensor. Simulations as function of channel doping, geometrical dimensions, operation point and materials investigated the device response to an external potential difference which provides a body threshold voltage modulation. The simulation results presented in this work clearly state the key features for an ultrasensitive FET based sensor: an enhancement low doped and partially gated transistor operating in weak-moderate inversion regime. The optimized sensitivity, obtained when the width of the fin is equal to the gate height (w_NW ∼ h_g), reaches a value of 85% for an extraction current, I_d, of 0.1 μA. These results pave the way for the fabrication process of an innovative CMOS compatible sensing system.     

Torque‐rheometry investigation of model transreactions involving condensation polymers. I. Polyesters

The chemical transformations taking place when poly(ethylene terephthalate) (PET) or poly(ethylene naphthalate) (PEN) are blended in the melt with different low molar mass substances containing hydroxyl, carboxyl, or amine functional groups have been investigated as models of the transreactions, undergone by the polyesters in reactive blending operations. The polyester molecular weight changes caused by the alcoholysis, acidolysis, aminolysis, and esterolysis reactions have been monitored by torque‐rheometry, using a Brabender Plasticorder static mixer. The degradation of the polyesters by hydrolysis was also studied, under similar conditions, by the addition of a water‐releasing substance (wet polyamide‐6), and was shown to occur quite rapidly, although most of the added water was lost by flash vaporization caused by the high temperature of the polyester melt. It has been shown that the rate constants of the reactions leading to breakage of the inner ester bonds of the polyester macromolecules decrease in the following order: aminolysis (with aliphatic amines, either primary and secondary) > alcoholysis (with aliphatic alcohols) ≈ hydrolysis > acidolysis (with aromatic acids) ≥ acidolysis (with aliphatic acids) ? aminolysis (with aromatic amines) > alcoholysis (with phenols) ? esterolysis. POLYM. ENG. SCI. 46:139–152, 2006. © 2005 Society of Plastics Engineers