Large particle effects in chemical/biochemical heap leach processes - A review

The application of heap leach technology to recovery of economically important metals, notably copper, gold, silver, and uranium, is wide-spread in the mining industry. Unique to heap leaching is the relatively coarse particle size, typically 12-25 mm top size for crushed and agglomerated ores and larger for run-of-mine dump leaching operations. Leaching from such large particles is commonly assumed to follow shrinking core type behaviour, although little evidence for the validity of this assumption exists. This review investigates the current state of knowledge with respect to the understanding of the characteristics and mineralogy of large particles and how these influence leaching in a heap context and the tools to characterize these. This includes the study of ore and particle properties, visualization techniques for ore characterization, the connection between comminution and leaching behaviour, as well as particle models within heap leach modelling. We contend that the economics of heap leaching are strongly governed by the trade-off between the slow rate and limited extent of leaching from large particles and the cost of crushing finer. A sound understanding of the underlying large particle effects will therefore greatly inform future technology choices in the area of heap leaching.     

Disgust as a disease-avoidance mechanism.

Many researchers have claimed that the emotion of disgust functions to protect us from disease. Although there have been several discussions of this hypothesis, none have yet reviewed the evidence in its entirety. The authors derive 14 hypotheses from a disease-avoidance account and evaluate the evidence for each, drawing upon research on pathogen avoidance in animals and empirical research on disgust. In all but 1 case, the evidence favors a disease-avoidance account. It is suggested that disgust is evoked by objects/people that possess particular types of prepared features that connote disease. Such simple disgusts are directly disease related, are acquired during childhood, and are able to contaminate other objects/people. The complex disgusts, which emerge later in development, may be mediated by several emotions. In these cases, violations of societal norms that may subserve a disease-avoidance function, notably relating to food and sex, act as reminders of simple disgust elicitors and thus generate disgust and motivate compliance. The authors find strong support for a disease-avoidance account and suggest that it offers a way to bridge the divide between concrete and ideational accounts of disgust. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The impact of family and community violence on children’s depression trajectories: Examining the interactions of violence exposure, family social support, and gender.

This longitudinal study used multilevel modeling to examine the relationships between witnessing intimate partner violence (IPV), community and school violence exposure (CSVE), family social support, gender, and depression over 2 years within a sample of 100 school-aged children. We found significant between-child differences in both the initial levels of depression and the trajectories of depression; depression over time was positively associated with change in witnessing IPV and CSVE and negatively associated with change in support. Two significant 3-way interactions were found: Gender and initial support, as well as gender and initial witnessing IPV, both significantly moderated the effect of change in witnessing IPV on the children’s depression over time. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Focussed Ion Beam

Focussed Ion Beam -“Cutting Edge” Technology of Material Analysis With the focussed ion beam technique it is possible to sputter almost any material with nanometer scale accuracy and directly image or chemically analyze structures below the surface. The major advantage towards conventional cross-section polishing is the high precision which allows to investigate even the smallest local defects. Applications of the focused ion beam even extend to the generation of complex nano structures. This article describes the operational modes, limits and constraints of the method and gives application examples from the field of material analytics.     

Composite chitosan and calcium sulfate scaffold for dual delivery of vancomycin and recombinant human bone morphogenetic protein-2

A biodegradable, composite bone graft, composed of chitosan microspheres embedded in calcium sulfate, was evaluated in vitro for point-of-care loading and delivery of antibiotics and growth factors to prevent infection and stimulate healing in large bone injuries. Microspheres were loaded with rhBMP-2 or vancomycin prior to mixing into calcium sulfate loaded with vancomycin. Composites were evaluated for set time, drug release kinetics, and bacteriostatic/bactericidal activity of released vancomycin, induction of ALP expression by released rhBMP-2, and interaction of drugs on cells. Results showed the composite set in under 36 min and released vancomycin levels that were bactericidal to S. aureus (>MIC 8–16 μg/mL) for 18 days. Composites exhibited a 1 day-delayed release, followed by a continuous release of rhBMP-2 over 6 weeks; ranging from 0.06 to 1.49 ng/mL, and showed a dose dependent release based on initial loading. Released rhBMP-2 levels were, however, too low to induce detectable levels of ALP in W20-17 cells, due to the affinity of rhBMP-2 for calcium-based materials. With stimulating amounts of rhBMP-2 (>50 ng/mL), the ALP response from W-20-17 cells was inhibited when exposed to high vancomycin levels (1,800–3,600 μg/mL). This dual-delivery system is an attractive alternative to single delivery or preloaded systems for bone regeneration since it can simultaneously fight infection and deliver a potent growth factor. Additionally, this composite can accommodate a wide range of therapeutics and thus be customizable for specific patient needs, however, the potential interactive effects of multiple agents must be investigated to ensure that functional activity is not altered.     

Behavior analysis in intellectual and developmental disabilities.

Individuals with intellectual and developmental disabilities (IDD) have deficits in adaptive behavior, slow rates of learning, and behavior disorders that interfere with learning or place them or others at risk. Since the 1960s, researchers and clinicians in the field of applied behavior analysis have used methods based on principles of learning to increase adaptive behavior and decrease the occurrence of behavior disorders of individuals with IDD. This article provides an overview of assessment and treatment strategies used in behavior analysis to effect positive changes in the quality of life for individuals with IDD and presents an illustrative case study. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The social norms of alcohol-related negative consequences.

Social norms for alcohol use are important influences on individual college student drinking. The present study extends social norms research by examining alcohol-related consequences and, in particular, whether similar misperceptions exist regarding the frequency and evaluation of these consequences over time. College student drinkers (N = 624) participating in a longitudinal study completed Web-based surveys assessing alcohol use and related consequences, as well as their beliefs about frequency and evaluation of consequences for the typical college student. Findings suggest that students overestimated how often typical college students experience negative consequences and underestimated how negatively other students evaluated those consequences. Finally, results support a bidirectional model for alcohol-related consequences, possibly indicating a reciprocal, mutually influential feed-forward loop of norms and consequences that promotes maintenance of college student drinking and consequences. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Atomic force microscopy study of the interaction of Fusarium solani pisi cutinase with lipid surfaces

We present an atomic force microscopy (AFM) study of a supported triacylglyceride multilayer phase and its interaction with lipolytic enzyme cutinase from Fusarium solani pisi. The multilayer triacylglyceride phase of coconut oil showed a rippled surface structure in the AFM images. Upon enzymatic degradation of the triacylglyceride phase, the ripple structure vanished rapidly. The apparent catalytic rate constants could be estimated based on the AFM image information. Interestingly, in one sample we observed what we interpret as a recurrent structural collapse of the cavity dug out by the protein. We interpret the cavities seen in the AFM images as molten surfaces or surface holes filled with liquidified phase containing product molecules, which appear transparent during the image recording.