Photocatalytic oxidation of cyclohexane over TiO2 nanoparticles by molecular oxygen under mild conditions

The structure, physical characteristics and photocatalytic selective oxidation properties of nanometer‐size TiO₂ particles produced by a sol–gel method were studied by X‐ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), X‐ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR) and photocatalytic selective oxidation measurements. Analysis of the XRD results shows that sol–gel‐produced TiO₂ nanoparticles have the anatase structure at annealing temperatures ≤973 K, that the rutile structure begins to emerge at annealing temperatures ≥973 K and the particles have the pure rutile structure at 1023 K. DRS indicates that the obtained TiO₂ nanoparticles exhibit a blue shift with decreasing crystallite size. Analysis of the XPS results shows that the TiO₂ nanoparticles have a lot of oxygen vacancies. The EPR spectrum of TiO₂ at 77 K is composed of a strong isotropic EPR Surface‐Ti³⁺ signal(I) at g = 1.926 and a weak broad Bulk‐Ti³⁺ signal (II) at g = 1.987. Quantitative EPR indicates that both signals show a size and temperature dependence. Photocatalytic oxidation of cyclohexane into cyclohexanol with high selectivity and activity has been obtained by activation of molecular oxygen over sol–gel‐produced TiO₂ nanoparticles under mild conditions in dry solvent, which reveals that the quantum size effect and surface state effect of nanoparticles are key points for governing the selective photocatalytic reaction. The photocatalytic oxidation mechanism under dry solvent is different from that in aqueous solutions. Copyright © 2003 Society of Chemical Industry     

Tracking, grading, and student motivation: Using group composition and status to predict self-concept and interest in ninth-grade mathematics.

Assigning students to different classes on the basis of their achievement levels (tracking, streaming, or ability grouping) is an extensively used strategy with widely debated consequences. The authors developed a model of the effects of tracking on self-concept and interest that integrates the opposing predictions of "assimilation" and "contrast" effects, which specifies teacher-assigned grades as a major mediating variable, and tested it in 2 settings in which track level is clearly associated with different status-systematic tracking as a function of school type (Study 1, N = 14,341 German 9th-grade students) and separate streams within a comprehensive school system (Study 2, N = 3,243 German 9th-grade students). The results support predictions that students' math self-concept and math interest differ as a function of the achievement of their reference group, their own achievement, and their teacher-assigned grades. No systematic association between track level and math self-concept was found once individual student achievement, school-/stream-average achievement, and teacher-assigned grades were controlled. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Recent advances in image reconstruction, coil sensitivity calibration, and coil array design for SMASH and generalized parallel MRI.

Parallel magnetic resonance imaging (MRI) techniques use spatial information from arrays of radiofrequency (RF) detector coils to accelerate imaging. A number of parallel MRI techniques have been described in recent years, and numerous clinical applications are currently being explored. The advent of practical parallel imaging presents various challenges for image reconstruction and RF system design. Recent advances in tailored SiMultaneous Acquisition of Spatial Harmonics (SMASH) image reconstructions are summarized. These advances enable robust SMASH imaging in arbitrary image planes with a wide range of coil array geometries. A generalized formalism is described which may be used to understand the relations between SMASH and SENSE, to derive typical implementations of each as special cases, and to form hybrid techniques combining some of the advantages of both. Accurate knowledge of coil sensitivities is crucial for parallel MRI, and errors in calibration represent one of the most common and the most pernicious sources of error in parallel image reconstructions. As one example, motion of the patient and/or the coil array between the sensitivity reference scan and the accelerated acquisition can lead to calibration errors and reconstruction artifacts. Self-calibrating parallel MRI approaches that address this problem by eliminating the need for external sensitivity references are reviewed. The ultimate achievable signal-to-noise ratio (SNR) for parallel MRI studies is closely tied to the geometry and sensitivity patterns of the coil arrays used for spatial encoding. Several parallel imaging array designs that depart from the traditional model of overlapped adjacent loop elements are described.     

The role of social and emotional communication skills in leader emergence and effectiveness.

Three studies explored the role that basic social/communication skills play in leader emergence and effectiveness. In Study 1, 218 undergraduate students were administered self-report measures of social/communication skills and extraversion, worked in small groups on a problem-solving task, and elected leaders at task midpoint. Coders measured leaders' verbal communication. Groups elected leaders who spoke most and were extraverted but were not more socially skilled. In Study 2, leaders were selected on the basis of their possession of communication skills and led small groups in 2 tasks. More skilled communicators were rated as more effective leaders, but they did not lead more productive groups. Study 3 examined fire service leaders. Social skills were related to satisfaction with the leader but related to leader performance only for higher level leaders. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cognitive processes in story understanding.

The major goal of the author's research has been to discover how readers overcome the limited capacity of working memory to discover the rich pattern of causal relationships found in even the simplest stories. The specific purpose of the series of experiments presented in this article is to discover what happens when the goals and actions are widely separated in the text, and when the actions are not associated with a coherence break. The results suggest that some readers retrieve the goal from long-term memory while others do not. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Characterization of the Coffee Mucilage Fermentation Process Using Chemical Indicators: A Field Study in Nicaragua

ABSTRACT: The recent "crisis" brought about by the collapse of the worldwide commodity coffee market has caused severe economic conditions for coffee producers in developing countries, including those of Central America. As a result, many coffee producers desire to improve the quality and consistency of their product to enter the specialty market. With the ultimate aim of assisting coffee producers in their quality control efforts, this study was designed to determine the feasibility of simple chemical measurements of the fermentation process on remote farms and to assess the potential of these measurements for assisting the producers in control and optimization efforts. Temperature, pH, and the concentrations of glucose, ethanol, and lactic acid were measured throughout the course of 7 coffee mucilage fermentation batches on 4 farms. In each batch, a pattern was observed in which the pH was initially in the range 5.5 to 5.7 and decreased sharply to about 4.6 as fermentation neared completion. Glucose concentration was seen to drop throughout the course of most batches, whereas either ethanol or lactic acid increased sharply near completion. The pH profile may prove useful in predicting the time of fermentation completion and in preventing over-fermentation of coffee mucilage.     

The use of a specific function to estimate maximum methane production in a batch‐fed anaerobic reactor

A readily biodegradable substrate was used to assess the value of using a mathematical function of y = y_maxexp^m/x as a simplified method of determining the maximum methane production (G_max) in a batch anaerobic reactor. Experimental results to test the method used three different initial substrate loadings in pre‐acclimatised completely mixed anaerobic reactors. Gas production was found to follow a typical trend that has previously been described by first order reaction kinetics; for the purpose of fitting the linearisation, it requires a value for maximum cumulative methane production. Use of the modified specific function to yield the equation G = G_maxexp^m/t showed that the experimental gas production curve could be estimated with a high degree of similarity. This was confirmed by a statistical analysis using the method of residuals which gave a correlation coefficient (R²) greater than 0.97 between experimental and estimated values. Using a graphical linearisation of the specific function produced a simplified method of predicting G_max. The value obtained was then used in a first order kinetic model to derive the specific coefficient rate (K_o), which was in agreement with other methods used for its determination. Copyright © 2004 Society of Chemical Industry     

Preschoolers' understanding of mental and bodily reactions to contamination: What you don't know can hurt you, but cannot sadden you.

Evidence of the operation of a biological theory might be found in children's distinction between mental (emotional) and bodily (illness) reactions to contamination. Study 1 explored whether children see emotions as voluntary but illness as outside of intentional control. Three- and 5-yr-olds judged that simple volitions were insufficient to alter either outcome. Study 2 suggested that children distinguish reactions mediated by representations from those mediated by physical interactions. Children indicated that knowledge determines mental reactions to contamination, but physical contact determines bodily reactions. Study 3 explored knowledge about particulars of emotional and illness reactions. Most preschoolers did not realize that illness takes time to develop. These data suggest that preschoolers do distinguish between physical and mental reactions to contamination but have a poor understanding of the actual bodily processes involved. (PsycINFO Database Record (c) 2010 APA, all rights reserved)