Kinetics of dye decolorization in an air–solid system

The photocatalytic decolorization of adsorbed organic dyes (Acid Blue 9, Acid Orange 7, Reactive Black 5 and Reactive Blue 19) in air was examined, applicable to self-cleaning surfaces and catalyst characterization. Dye-coated Degussa P25 titanium dioxide (TiO₂) and dye-coated photo-inert aluminum oxide (Al₂O₃) particles, both of sub-monolayer initial dye coverage, were illuminated with 1.3 mW cm⁻² of near-UV light. Visual evidence of color removal is reported with photographic images. Two methods, Indirect and Direct Analysis, were employed to quantitatively examine the decolorization kinetics of dyes using UV–visible transmission and diffuse reflectance spectroscopy, respectively. A decrease in dye concentration with time was observed with near-UV illumination of dye-coated TiO₂ powders for all dyes. Dyes did not photodegrade significantly on photo-inert Al₂O₃.

UV–visible spectroscopy data was used to model the kinetics of the photocatalytic degradation. Two first-order reactions in series provided the most convincing rate form for the photodegradation of dyes adsorbed to TiO₂, with a first step the conversion of colored dye to colored intermediate, and the second the conversion to colorless product(s). The first rate constant was of similar magnitude for all dyes, averaging k₁ = 0.13 min⁻¹. Similarly, for the second, k₂ = 0.0014 min⁻¹.     

Early Photography in Samoa

Abstract

The history of photography in Samoa, a small group of islands in the Western Pacific, suggests, in microcosm, the history of ‘exotic’ photography throughout the world in the period of imperial expansion. The romantic myths of the South Seas, coupled with the islands' practical significance to their colonizers as coaling stations, navy bases and a source of raw materials and cheap labour, encouraged outside interest and assured a market for the products of many kinds of photographers. As early as the 1880s, amateurs on holiday, scientists in the field, and itinerant professionals had passed through Samoa, taking a wide variety of images away with them. By the 1890s, Apia, Samoa's largest town, was home to three resident photographers. Their work was put to conventional private use there for portraits, wedding pictures and the like, and was widely distributed overseas as novelty carter-de-visite, cabinet-size, and full-plate albumen prints, as souvenir postcards and gravures, and as half-tone illustrations in newspapers and magazines. In addition to documenting a society undergoing great change, early photographs of Samoa are often strikingly beautiful, appealing to our appreciation of the exotic and romantic, much as they were intended to do for their foreign audiences one hundred years ago.     

The Management of Knowledge during Design and Implementation of Process Technologies

Knowledge and learning play a major part in the successful implementation of process technologies. We suggest that managers of implementation projects can improve the initial performance levels of the process in which a new technology resides by ensuring that useful knowledge, present in the organization at the start of the implementation project, is employed to greatest effect during the design of the modified process and that new learning is not lost. This does not necessarily require major investment in computerized systems – merely exploring what potentially useful knowledge is already available within the organization, or can readily be obtained from external contact, may improve the efficiency of technology implementation. Use of available knowledge can also help to speed up the implementation process by reducing the number of, and time required for, the adaptations necessary to get the process to the desired performance level.     

Auditing NT — Part 2

This second article on NT auditing focuses on controlling users: whether or not they use the system, what they can do once they are in, and how to keep a record of what they have done. As with the operating system configuration that we looked at in the last article, you will need administrator access to review many of the security settings, and to review the security log. You will also be using tools supplied in the NT Resource kit to get listings of information that cannot be effectively scanned online.     

Technology learning for renewable energy: Implications for South Africa's long-term mitigation scenarios

Technology learning can make a significant difference to renewable energy as a mitigation option in South Africa's electricity sector. This article considers scenarios implemented in a Markal energy model used for mitigation analysis. It outlines the empirical evidence that unit costs of renewable energy technologies decline, considers the theoretical background and how this can be implemented in modeling. Two scenarios are modelled, assuming 27% and 50% of renewable electricity by 2050, respectively. The results show a dramatic shift in the mitigation costs. In the less ambitious scenario, instead of imposing a cost of Rand 52/t CO₂-eq (at 10% discount rate), reduced costs due to technology learning turn renewables into negative cost option. Our results show that technology learning flips the costs, saving R143. At higher penetration rate, the incremental costs added beyond the base case decline from R92 per ton to R3. Including assumptions about technology learning turns renewable from a higher-cost mitigation option to one close to zero. We conclude that a future world in which global investment in renewables drives down unit costs makes it a much more cost-effective and sustainable mitigation option in South Africa.     

The prevention of mindlessness.

We conducted three experiments to assess the hypothesis that mindlessness could be prevented with a simple linguistic variation. Subjects in the first two experiments were either introduced to new objects conditionally (e.g., this could be an X) or unconditionally (e.g., this is an X), and the objects used were either unfamiliar or familiar. In each study a different need was then generated for which the object in question was not explicitly suited but could fulfill. Only those subjects in the conditional-unfamiliar group gave the creative response and met the need. When subjects were asked explicitly to generate novel uses for the target items, they had no difficulty doing so. However, given the way we are traditionally taught, it simply does not occur to us to think creatively unless explicitly instructed to do so. In the third experiment we introduced an unfamiliar item in one of three ways. In addition to the groups used in the earlier experiments, we added a group that was led to believe that the object was identifiable (unconditional) but was currently unknown. We also added a second need to determine whether the original conditional group truly learned conditionally or if they were in search of an absolute understanding of the target object. Significantly more of the subjects in the conditional group gave the creative response to both needs. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The fracture behaviour of two Co-Mo-Cr-Si wear resistant alloys (“Tribaloys”)

The room temperature modulus of rupture (MOR) and the plane strain fracture toughness (K _IC) of two Co-Mo-Cr-Si wear resistant alloys in various microstructure conditions have been determined. The modulus of rupture varied from 304 to 927 MN m^–2 and as such was more structure sensitive thanK _IC, which was in the range 15 to 26 MN m^–3/2 for all conditions of the alloys. The best combination of room-temperature properties was associated with an f c c solid solution whereas h c p solid solution with a Widmanstätten precipitate produced the poorest properties. The industrial significance of these results are discussed.     

Articulatory complexity at item boundaries in serial recall: The case of Welsh and English digit span.

The proposition that the difference in memory span between Welsh digits and English digits is accounted for by the longer articulatory duration of Welsh digits is critically reexamined. Two methods of measuring digit duration are contrasted. One is derived from digits spoken in isolation, the other is based on digits spoken in list format. Duration of Welsh digits was greater only when spoken in lists; with isolated production Welsh digits were significantly shorter than English digits. Also, span was shorter for Welsh digits. The results are interpreted in the light of the different articulatory demands made at the junctures between words in the English and Welsh lists. A supplementary experiment, using English words, illustrated that articulatory complexity at item boundaries increased serial recall error. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of parental separation and divorce on very young children.

Data from the National Institute of Child Health and Human Development Study of Early Child Care were analyzed to explore effects of marital separation on children in the first 3 years of life. The sample included 73 never-married mothers and 97 separated mothers; a comparison group of 170 was conditionally randomly selected from the 2-parent families. Children in 2-parent families performed better than children in 1-parent families on assessments of cognitive and social abilities, problem behavior, attachment security, and behavior with mother. However, controlling for mothers' education and family income reduced these differences, and associations with separated-intact marital status were nonsignificant (the effect size was .01). Thus, children's psychological development was not affected by parental separation per se; it was related to mothers' income, education, ethnicity, childrearing beliefs, depressive symptoms, and behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Mortality salience and the spreading activation of worldview-relevant constructs: Exploring the cognitive architecture of terror management.

Seven experiments assessed the hypothesis derived from terror management theory that reminding people of their mortality would increase accessibility of constructs central to their worldview. Experiment 1 found that mortality primes, relative to control primes, increased accessibility of nationalistic constructs for men but not for women. Experiment 2 replicated this finding and also found that mortality salience increased romantic accessibility for women but not for men. Four subsequent experiments supported the role of unconscious death-related ideation in producing these effects. A final experiment demonstrated that situational primes can increase the accessibility of nationalistic constructs for women after mortality salience. The roles of situational cues and individual differences in the effects of exposure to death-related stimuli on worldview-relevant construct accessibility are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)