Growth of Cement Hydration Products on Single-Walled Carbon Nanotubes

Single-walled carbon nanotubes (SWCNT) were distributed on the surface of ordinary Portland cement (OPC) grains. The OPC/SWCNT composite was then hydrated at a 0.5 w/c ratio. The effects of the SWCNT on the early hydration process were studied using isothermal conduction calorimetry, high-resolution scanning electron microscopy and thermogravimetric analysis. The observed behavior of the composite samples was compared with both OPC sonicated without SWCNT and previously published data on as-delivered OPC. The SWCNT were found to accelerate the hydration reaction of the C₃S in the OPC. The morphology of both the initial C₃A and the C₃S hydration products were found to be affected by the presence of the SWCNT. In particular, the nanotubes appeared to act as nucleating sites for the C₃S hydration products, with the nanotubes becoming rapidly coated with C–S–H. The resulting structures remained on the surface of the cement grains while those in the sonicated and as-delivered OPC samples grew out from the grain surfaces to form typical C–S–H clusters. Classical evidence of reinforcing behavior, in the form of fiber pullout of the SWCNT bundles, was observed by 24 h of hydration.     

Nest Liquid Resources of Several Cavity Nesting Bees in the Genus Centris and the Identification of a Preservative, Levulinic Acid

Twig-nesting species of bees in the genus Centris including C. bicornuta, C. analis, C. vittata, and C. nitida, found in the dry forest of Guanacaste Province of Costa Rica, provision their nests with pollen and nectar, rather than pollen and oil as reported for other Centris species. The liquid contents of the nests of these four species were found to contain sugars including 66–75% fructose, 25–33% glucose, and a trace of sucrose. The sugar concentration averaged 47.2%, slightly higher than most flower nectars. No tri-, di-, or monoglycerides, the main components of the flower oil of Byrsonima crassifolia, were detected in the nest provisions. Although these four Centris species are also known to collect oil from B. crassifolia, the oil appears to be used for activities other than nest provisioning. The liquid nest contents did have a slight goat-like odor, suggesting the presence of short-chain fatty acids, and were found to contain a small amount (less than 1%) of three fatty acids. Two of these, butanoic and octanoic acid, were found in trace amounts and are responsible for the goat-like odor. A third was identified as levulinic acid, which made up about 99% of the nest fatty acid contents. This fatty acid had little odor, but may be important as a fungicidal agent. Attempts to determine the source of the fatty acids, were not successful.     

CP3: Robust, Output-sensitive Display of Convex Polyhedra in Scanline Mode

A new technique is developed for displaying disjoint convex polyhedra. The method has the following properties: It is output-sensitive, displays the objects in scanline mode, and it is naturally robust. There is no complex data structure uniting the different polyhedra, so dynamic insertions and deletions are simple. Its robustnes is based on a novel method of comparing depths by representative "axes" of objects instead of surfaces. The method is based on two extensions of the "critical-points" method for polygon scan conversion: One extension allows the efficient display of planar graphs in scanline mode, and another extension is into the third dimension. Test runs indicate that it compares extremely favorably with other methods that operate in scanline mode, as well as with standard software and hardware techniques of medium-level workstations.     

The Relation Between Brain Activity During Memory Tasks and Years of Education in Young and Older Adults.

Higher education is associated with less age-related decline in cognitive function, but the mechanism of this protective effect is unknown. The authors examined the effect of age on the relation between education and brain activity by correlating years of education with activity measured using functional MRI during memory tasks in young and older adults. In young adults, education was negatively correlated with frontal activity, whereas in older adults, education was positively correlated with frontal activity. Medial temporal activity was associated with more education in young adults but less education in older adults. This suggests that the frontal cortex is engaged by older adults, particularly by the highly educated, as an alternative network that may be engaged to aid cognitive function. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Influence of Surface Condition on the Inspection of Steel Bridge Elements Using the Time-of-Flight Diffraction Method

Prior studies on the time-of-flight diffraction (TOFD) method have focused primarily on ground smooth, clean surfaces of steel. In practice, however, the surface of an existing bridge element will be covered with rust or have several layers of paint. The main objective of this study was to evaluate the influence of the surface condition of steel elements (i.e., painted or rusted) on the ability of the method to accurately detect and size flaws. These objectives were met by performing a number of tests on plates with saw cuts or implanted fatigue cracks with different surface conditions. These included ground smooth and polished, rusted, and painted surfaces. The data show that rusted surfaces will reduce the amplitude of the ultrasonic signals, but they will not impair the ability of the TOFD method to detect and accurately size flaws. A painted surface will also cause a reduction in signal amplitude. More important, however, is the appearance of additional wave signals that could be interpreted as false indications. While these additional signals do not obscure the presence of actual flaws or affect the accuracy of the TOFD method to size the flaws, they make flaw detection more difficult. Based on the results of this study, recommendations for field inspection on rusted or painted surfaces using the TOFD method are provided.     

Sexuality on the Internet: From sexual exploration to pathological expression.

A growing number of clients are presenting in therapy with problems related to their on-line sexual habits. Adults who had used the Internet for sexual pursuits at least once (N?=?9,177) completed a 59-item on-line survey. Men and women generally behaved differently, and most (92%) indicated their on-line sexual behaviors were not problematic. Heavy users (8%) reported significant problems typically associated with compulsive disorders. Problems were highly correlated with time spent on-line for sex. Results are discussed in terms of their research and practice implications, including diagnosis and treatment. Recommendations are made for outreach prevention programs and future policies. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Recovery of Rotorua geothermal field, New Zealand: Progress, issues and consequences

Recovery of most surface features in many parts of the Rotorua geothermal field (RGF) has continued as water levels rose and pressures increased following bore closures that began in 1986. However, the pattern of recovery of features is very variable, even within a relatively small area, with no apparent consistency as to location or type of feature. Most features in the Whakarewarewa Thermal Area that were affected by the pre-1986 pressure drawdown have recovered, but some have not. More puzzling is the behaviour of a few features (such as Waikorohihi and Mahanga geysers) that initially showed recovery, but later ceased activity. Chemical data indicate that for some features there has been an increase in the amounts of deep fluid reaching the surface, but in others there has been no change. Examination of seismic records suggests that the unusual behaviour is not related to local seismic activity. The recovery of many thermal features has been beneficial from a tourist and environmental viewpoint. However, there have been some detrimental occurrences. Following the decline and disappearance of thermal features before the bore closures, the vents of some features were inadvertently filled in and the land around them reclaimed and used for buildings or services. As water levels recovered after the closures, discharge to the surface recommenced, causing damage to buildings and associated services, resulting in several houses being damaged or forced to be relocated. In all cases, however, the discharges were from historically active vents. The data suggest that while most natural thermal features may recover from the effects of geothermal exploitation some may not, and in the case of Rotorua there does not appear to be any pattern or explanation for such non-recovery.     

Introduction to the special section on multicultural and community psychology: Clinical psychology in context.

Human behavior occurs in the contexts of culture and community. Yet, clinical psychology has traditionally focused on the individual, neglecting the individual's context. The purpose of this Special Section is to address the underlying conceptual issues in integrating multicultural and community psychology within a common framework. The integration of etic and emic approaches distinguishes the research programs in these articles from others that have solely focused on universal or culture-specific approaches. Issues facing ethnic minority populations are addressed, including identification of risk and protective factors, obstacles to mental health service use, and optimal treatment effectiveness. The integration of culture and community contexts into clinical psychology is necessary for it to remain relevant in an increasingly diverse 21st century. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

便携式手持设备的LED背光和装饰光

在手机、寻呼机和PDA等便携式手持设备中,传统上采用电致发光(EL)或LED驱动电路为屏幕和键盘提供背光,主要是为了在低照明度情况下方便阅读屏幕和进行键盘操纵.因此亮度是最关键的要求,颜色则不是那么重要,因为显示屏通常是单色的LCD.因此只要显示屏的亮度足够并且能够容易地分辨出按键,电致发光(EL)或彩色LED的色调是完全可以接受的.