Kinetics and Mechanism of Metal Nanoparticle Growth via Optical Extinction Spectroscopy and Computational Modeling: The Curious Case of Colloidal Gold

An overarching computational framework unifying several optical theories to describe the temporal evolution of gold nanoparticles (GNPs) during a seeded growth process is presented. To achieve this, we used the inexpensive and widely available optical extinction spectroscopy, to obtain quantitative kinetic data. In situ spectra collected over a wide set of experimental conditions were regressed using the physical model, calculating light extinction by ensembles of GNPs during the growth process. This model provides temporal information on the size, shape, and concentration of the particles and any electromagnetic interactions between them. Consequently, we were able to describe the mechanism of GNP growth and divide the process into distinct genesis periods. We provide explanations for several longstanding mysteries, for example, the phenomena responsible for the purple-greyish hue during the early stages of GNP growth, the complex interactions between nucleation, growth, and aggregation events, and a clear distinction between agglomeration and electromagnetic interactions. The presented theoretical formalism has been developed in a generic fashion so that it can readily be adapted to other nanoparticulate formation scenarios such as the genesis of various metal nanoparticles.Comment: Main text and supplementary information (accompanying MATLAB codes available on the journal webpage

Cerebral aneurysm treatment: modern neurovascular techniques.

Endovascular treatment of cerebral aneurysm continues to evolve with the development of new technologies. This review provides an overview of the recent major innovations in the neurointerventional space in recent years

The acceptability of concrete block construction in low cost housing in the Cape Peninsula

This article presents the findings of a research project examining the acceptabil­ity of concrete block construction for low cost housing in the Cape Peninsula in terms of materials and execution. Data were collected by means of a question­naire survey in which residents of low cost housing were interviewed. In addition, personal and telephonic interviews were conducted with key stakeholders from the construction industry involved in the delivery of low cost housing. The findings indicate that concrete block construction is being used extensively for low cost housing developments in the Cape Peninsula, owing to its defining characteristics such as ease of construction, affordability, durability, speedy delivery and acceptance. End-users are generally satisfied with the construction material used for the wall structure of their current houses. They are, however, dissatisfied with the workmanship of the construction, as they feel that problems such as cracking and damp have arisen because of hurried and incomplete construction. The end­users are aware that the wall structures are not plastered, but only bagged. Even without any formal or technical knowledge of building houses, they state that they should be involved in the planning and construction stages of their new homes with regard to funding and appearance in order to make these homes more affordable and acceptable. Despite a lack of technical knowledge of concrete technology, the respondents felt that the concrete block was the· most accept­able form of construction material available for wall structures because of its per­ceived strength and durability

Interference of coarse and fine particles of different shape in mixed porous beds and filter cakes

In solid–liquid separation the knowledge of solids packing structure is important to control permeability and dewaterability. In particular, cakes formed in filtration are often represented by the composition in coarse and fine particles. In this work cakes were modelled by mixing a bed of coarse (spheres) and fine (kieselguhr of three types and kieselgel) particles with a wide size distribution, in order to obtain beds with different proportions of plate and rod-like particles. Size ratio of glass beads to kieselguhr particles were in the range 23–30. Porosity and permeability were measured for a range of large particle fraction in the mixture from 0 up to 1.0. The fractional porosity of each particle fraction was introduced as a parameter. The approach proposed in this work was also successfully applied to different published filtration data. It was found that (1) the presence of more than 10% of fines in the coarse granular bed significantly reduces the cake permeability; (2) to improve cake permeability the volume fraction of filter aid in suspension must be at least 50–60% of total solid volume; (3) obtained data may be used to control the porosity of a mixture, if the fractional porosity of large and small particles is known or to estimate mixture tortuosity.Fundação para a Ciência e a Tecnologia (FCT) – POCTI/EQU/37500/2001

"It’s your rights, ok?": explaining the right to silence to Aboriginal suspects in the Northern Territory

When a suspect is interviewed by the police, s/he has the right to decline to answer police questions and avoid self-incrimination. This is a fundamental procedural protection, and police are required to inform suspects of the ‘right to silence’, also called the ‘caution’, before beginning the interview. However, the way the caution is stated, both in legal texts and by police officers, is often linguistically and conceptually complex. This makes it less likely that suspects will understand their right to remain silent, especially if they are Aboriginal and speak English as a second language or dialect. Aboriginal people are over-represented in the criminal justice system, and, if they do not understand the right to silence, this may aggravate that disadvantage. In Anunga (1976), the NT Supreme Court attempted to reduce this disadvantage, by requiring police explaining the caution to Aboriginal suspects to obtain evidence of “apparent understanding”. However, this has led to conversations about the caution which are sometimes long and unsuccessful. Difficulties with the caution have long been acknowledged by courts, linguists and others, but regulatory guidance and police language have changed little in 20 years, and there has been no systematic study of the speech event (‘caution conversation’) resulting from the Anunga requirements. The caution originates in a legislated text but police vary its form and content. This thesis examines transcripts in which police explain the caution to Aboriginal suspects and test understanding. It examines what is said and how it is expressed, and what is left unsaid in the caution. It compares the transcripts with translations into Aboriginal languages, and shows that these further vary the caution text, revealing additional meaning. The caution’s meaning is partly about interaction (establishing norms for the interview speech activity) and partly informative (describing the consequences of speaking or not speaking to police). The linguistic analysis takes place at different levels. At the conceptual level, most paraphrases arguably assume knowledge, particularly about rights and evidence. At the conversation level, the caution conversation is a complex speech activity, and the extent to which suspects can understand its purposes and mechanisms is likely to affect understanding of the right to silence. At the discourse level the way police repeat and explain the caution affects its interpretation. Multiple versions of the caution may provide different ways to understand the caution, but unclear discourse relationships between restatements of the caution can also create confusion. At the sentence level, the ambiguous roles of conditional clauses may make versions of the caution harder to understand and relate to each other. At the word-level, police lexical and grammatical choices have different kinds of equivalence in Aboriginal languages, and suspect responses suggest that modality used by police to say that silence is permissible is particularly unclear. Analysis of existing problems in communication and alternative ways of expressing the caution can suggest ways to improve communication to attempt to demystify this aspect of the legal process