Thermodynamics of an Empty Box.

A gas in a box is perhaps the most important model system studied in thermodynamics and statistical mechanics. Usually, studies focus on the gas, whereas the box merely serves as an idealized confinement. The present article focuses on the box as the central object and develops a thermodynamic theory by treating the geometric degrees of freedom of the box as the degrees of freedom of a thermodynamic system. Applying standard mathematical methods to the thermodynamics of an empty box allows equations with the same structure as those of cosmology and classical and quantum mechanics to be derived. The simple model system of an empty box is shown to have interesting connections to classical mechanics, special relativity, and quantum field theory.

Acid leaching technology for post-consumer gypsum purification.

Background: Contaminants and water-soluble salts present in mechanically recycled gypsum from refurbishment and demolition (post-consumer) plasterboard waste limit its use as a secondary raw material in plasterboard manufacturing. This research addresses this limitation, developing a novel acid leaching purification technology combined with an improved mechanical pre-treatment for post-consumer gypsum valorization. Methods: Laboratory-scale acid leaching purification was performed with a borosilicate beaker, hot plate, and overhead stirrer. Stuccos were produced after calcination of gypsum at 150 °C for 3 hours. Samples were characterized through X-ray fluorescence, X-ray diffraction, thermal gravimetric analysis, scanning electron microscopy and particle size analysis. Results: Acid leaching at 90 °C for 1 h using a 5 wt% sulfuric acid solution was revealed to be the optimum purification conditions. Stuccos produced from purified gypsum under optimum conditions had similar initial setting times to that of a commercial stucco but with higher water demand, which could be reduced by optimizing the calcination conditions. A magnesium-rich gypsum was precipitated from the wastewater. Conclusions: Purified post-consumer gypsum with > 96 wt% chemical purity and calcium sulfate dihydrate content was produced. The research recommends acid neutralization prior filtration, use of gypsum particles < 2 mm in size, and stirring speed of 50 rpm to reduce the economic and environmental impacts of the acid leaching purification process at industrial scale. The magnesium-rich gypsum could potentially be marketed as soil fertilizer.

Plasterboard is a construction material constituted by a gypsum core sandwiched between two paper liners. Plasterboard waste generated in refurbishment and demolition projects, which is known as post-consumer plasterboard waste, contains contaminants such as mortar, plastics, foil and wood, and impurities originating from additives introduced during plasterboard manufacturing and from plasterboard finishings, such as paint and wallpaper. These contaminants and impurities cannot be removed with current mechanical treatments used in plasterboard recycling plants, and post-consumer plasterboard waste is disposed of in landfills. A novel acid leaching purification process was developed here and combined with a modified mechanical treatment that produces high purity recycled gypsum from post-consumer plasterboard waste that fulfils the requirements for plasterboard manufacturing. This new plasterboard recycling technology will prevent plasterboard waste landfilling and increase the recycled content in new plasterboards. As a result, mineral gypsum use in new plasterboards will be reduced, which will lower the environmental impact associated to mineral gypsum extraction and transportation.

The source of chemical bonding.

Developments in the application of quantum mechanics to the understanding of the chemical bond are traced with a view to examining the evolving conception of the covalent bond. Beginning with the first quantum mechanical resolution of the apparent paradox in Lewis's conception of a shared electron pair bond by Heitler and London, the ensuing account takes up the challenge molecular orbital theory seemed to pose to the classical conception of the bond. We will see that the threat of delocalisation can be overstated, although it is questionable whether this should be seen as reinstating the issue of the existence of the chemical bond. More salient are some recent developments in a longstanding discussion of how to understand the causal aspects of the bonding interaction--the nature of the force involved in the covalent link--which are taken up in the latter part of the paper.

Postoperative biochemical liver function after major hepatic resection in children.

BACKGROUND/PURPOSE: There are no detailed reports of the profile of biochemical liver function tests (LFTs) after partial hepatectomy in children. The study aims to establish normal profiles of standard LFTs after major liver resection in noncirrhotic children; the effects of preoperative chemotherapy were also analyzed. METHODS: Clinical and biochemical data were collected from a consecutive series of children who had undergone a primary major liver resection for a hepatic tumor. Chemotherapy details were recorded. Children who had more than 4 liver segments resected were compared with those undergoing lesser resections. Those with and without preoperative chemotherapy were also compared. RESULTS: A total of 22 children underwent major liver resection at a median age of 24 months (range, 2 weeks to 16 years). Fifteen received preoperative chemotherapy. Peak derangements in all standard LFTs occurred on day 1 to day 2 postoperatively. Normal plasma levels of bilirubin and albumin were present by day 5, international normalized ratio and alkaline phosphatase by day 7, and alanine aminotransferase by 1 to 2 weeks. Peak alanine aminotransferase and international normalized ratio values tended to be higher in children having more extensive liver resections. Preoperative chemotherapy given up to 3 weeks before surgery had no major effect on LFT recovery profiles. Hypophosphatemia was maximal on day 2. CONCLUSIONS: Postoperative LFTs showed a more rapid resolution than typically seen after partial hepatectomy in adults. Preoperative chemotherapy had no major effects on postresection LFT profiles.

Who makes good use of memory aids? Results of a survey of people with acquired brain injury.

Wilson and Watson (1996) identified several factors that were associated with use of memory aids and strategies in a group of people with acquired brain injury. The present study tested these findings, with the aim of identifying the variables that best predict effective use of memory aids after brain injury. One-hundred and one people with memory problems arising from brain injury and their carers were interviewed to identify the aids/strategies used to compensate for memory impairment, and the efficacy of their use. Information relating to variables previously found, or hypothesized to predict use of memory aids, was collected. Use of memory aids correlated with level of independence. External aids such as calendars, wall charts, and notebooks were the most commonly used memory aids. Electronic organizers were not used by many participants. The variables that best predicted use of memory aids were (1) current age, (2) time since injury, (3) number of aids used premorbidly, and (4) a measure of attentional functioning. The implications for rehabilitation services are discussed.

Chemical substances and intensive properties.

Despite the importance molecular structure has acquired in 20th century chemistry, more traditional macroscopic notions in terms of a continuous concept of matter continue to play a role in chemical theorizing. In the light of the extensive and determined criticism of reductionism in recent philosophy of chemistry, it is of interest to see macroscopic ontology treated autonomously. One aspect of this is developed here, namely, the concept of chemical substance. This is characterized by contrast with phases and solutions. The key conception is that of an intensive property, which is defined by appeal to the mereological structure of parts of the entities bearing substance properties.

Neurological, cognitive and attributional predictors of posttraumatic stress symptoms after traumatic brain injury.

We investigated the relationship between the reporting of symptoms of posttraumatic stress disorder (PTSD) in a community sample of 66 survivors of severe traumatic brain injury (TBI) and measures of injury severity, memory, insight, and index-event attributions. Correlational analyses revealed that reporting of PTSD symptoms was related to level of insight and not associated with the severity of survivors' injury, educational background, premorbid or current IQ, or memory impairment. The severity of PTSD symptoms was also associated with external attributions to others of causality for the event.