A study of the charge structure and energy utilisation in a Stirred Media Detritor using DEM-SPH

The Stirred Media Detritor, (SMD), is a grinding device used for fine and ultra-fine grinding applications in mineral processing. The SMD has a vertically orientated shell that supports a shaft, with protruding impeller arms for agitating the charge. There is currently limited understanding of charge structure and motion in the SMD, particularly the interaction of the media and the slurry. Additionally, the number of arms and their arrangement on the shaft, are important aspects of the impeller that determine flow, energy consumption and grinding efficiency. Impeller geometry choices affect these characteristics of the process. This work focuses on studying the flow of grinding media and slurry for the industrial scale SMD 1100- E. This information is used to explore charge dynamics and energy utilisation in the SMD. To investigate the effect of impeller arm configuration on the operational behaviour of the SMD, the commercially available impeller configuration of the industrial scale SMD 335-E is used as the base case. Mill charge dynamics, transport and mixing, patterns of energy absorption on the mill surfaces are examined for the base case and compared to three different impeller arm arrangements. A two-way transient coupled Discrete Element Method (DEM) and Smoothed Particle Hydrodynamics model is used to achieve this. The ceramic grinding media is represented by the DEM component of the model, which is fully resolved, while the slurry (water and fine particles) is represented by the Smoothed Particle Hydrodynamics (SPH) model. The focus is on steady state operation therefore discharge from and feed into the mill are omitted. A nominal media size of 8 mm is used. The rotational action of the impeller forces the charge to the mill wall creating vortex centred on the mill shaft. The vortex is conical with a large diameter at the bottom, which decrease towards the bottom of the mill. Abrasion is found to be the dominant breakage mechanism in the SMD. Mixing behaviour is complex with media transfer past layers of impeller arms being influenced by the fall distance of media between impeller arm encounters

Inter-individual genetic variation in the temperature response of Leptosphaeria species pathogenic on oilseed rape

It is important to understand the likely response of plant pathogens to increased temperatures due to anthropogenic climate change. This includes evolutionary change due to selection on genetically based variation in growth rate with temperature. We attempted to quantify this in two ways. First, radial mycelial growth rates in agar culture were determined for a collection of 44 English isolates of Leptosphaeria maculans and 17 isolates of L. biglobosa, at 14 temperatures. For L. maculans the genetic variances in four parameters were measured: minimum temperature allowing growth, optimum temperature, growth rate at the optimum temperature and growth rate at the highest usable temperature, 31.8°C. The standard deviations were 0.068 °C , 1.28°C, 0.21 mm day-1 and 0.31 mm day 1 °C-1 respectively. For L. biglobosa, these figures were, respectively: immeasurably small, 1.31 °C, 0.053 mm day-1 and 0.53 mm day- °C-1. In addition, the incidence and severity of phoma stem canker in planta over a natural growing cycle at four temperatures (16°C, 20°C, 24°C and 28°C) around the average culture optimum were determined. There was no correlation between in vitro and in planta growth, and the decrease in pathogen measures either side of the optimum temperature was much less for in planta growth than for in vitro growth. We conclude that both pathogens have the capacity to evolve to adapt to changes in environmental conditions, but that predictions of the effect of this adaptation, or estimates of heritability in natural conditions, cannot be made from measurements in vitro

Decolonizing Science and Science Education in a Postcolonial Space (Trinidad, a Developing Caribbean Nation, Illustrates)

The article addresses how remnant or transformed colonialist structures continue to shape science and science education, and how that impact might be mitigated within a postcolonial environment in favor of the development of the particular community being addressed. Though cognizant of, and resistant to, the ongoing colonial impact globally and nationally (and any attempts at subjugation, imperialism, and marginalization), this article is not about anticolonial science. Indeed, it is realized that the postcolonial state of science and science education is not simply defined, and may exist as a mix of the scientific practices of the colonizer and the colonized. The discussion occurs through a generic postcolonial lens and is organized into two main sections. First, the discussion of the postcolonial lens is eased through a consideration of globalization which is held here as the new colonialism. The article then uses this lens to interrogate conceptions of science and science education, and to suggest that the mainstream, standard account of what science is seems to represent a globalized- or arguably a Western, modern, secular-conception of science. This standard account of science can act as a gatekeeper to the indigenous ways of being, knowing, and doing of postcolonial populations. The article goes on to suggest that as a postcolonial response, decolonizing science and science education might be possible through practices that are primarily contextually respectful and responsive. That is, localization is suggested as one possible antidote to the deleterious effects of globalization. Trinidad, a postcolonial developing Caribbean nation, is used as illustration

Original Article

The pancreas taken from the frog (Rana nigromaculata) was fixed in 1% OsO_4 and sliced into ultrathin sections for electron microscopic studies. The following observations were made: 1. A great \u27number of minute granules found in the cytoplasm of a pancreatic cell were called the microsomes, which were divided into two types, the C-microsome and S-microsome. 2. Electron microsopic studies of the ergastoplasm showed that it is composed of the microsome granules and A-substance. The microsomes were seen embedded in the A-substance which was either filamentous or membranous. The membranous structure, which was called the Am-membrane, was seen to form a sac, with a cavity of varying sizes, or to form a lamella. 3. The Am-membrane has close similarity to α-cytomembrane of Sjostrand, except that the latter is rough-surfaced. It was deduced that the Am-membrane, which is smooth-surfaced, might turn into the rough-surfaced α-cytomembrane. 4. There was the Golgi apparatus in the supranuclear region of a pancreatic cell. It consisted of the Golgi membrane, Golgi vacuole and. Golgi vesicle. 5. The mitochondria of a pancreatic cell appeared like long filaments, and some of them were seen to ramify. 6. The membrane of mitochondria, i. e. the limiting membrane, consisted of the Ammembrane. The mitochondria contained a lot of A-substances, as well as the C-microsomes and S-microsomes. When the mitochondria came into being, there appeared inside them chains of granules, which appeared like strips of beads, as the outgrowths of the A-substance and the microsome granules attached to the Am-membrane. They are the so-called cristae mitochondriales. 7. The secretory granules originate in the microsomes. They came into being when the microsomes gradually thickened and grew in size as various substances became adhered to them. Some of the secretory granules were covered with a membrane and appeared like what they have called the intracisternal granule of Palade.It seemed that this was a phenomenon attendant upon the dissolution and liqutefaction of the secretory granule. 8. Comparative studies were made of the ergastoplasm of the pancreatic cells from the frogs in hibernation, the frogs artificially hungered, the frogs which were given food after a certain period of fasting, the frogs to which pilocarpine was given subcutaneously, and the very young, immature frogs. The studies revealed that the ergastoplasm of the pancreatic cells greatly varied in form with the difference in nutritive condition and with different developmental stages of the cell. The change in form and structure occured as a result of transformation of the microsomes and A-substance. The ergastoplasm, even after it has come into being, might easily be inactivated if nutrition is defective. The ergastoplasm is concerned in the secretory mechanism, which is different from the secretory phenomenon of the secretory granules. It would seem that structurally the mitochondria have no direct relation to this mechanism

Currículo e Relações Étnico-Raciais: o Estado da Arte

Este artigo apresenta a sistematização e a análise dos 38 artigos, 13 teses e 50 dissertações da Categoria Currículo. Inicialmente, demonstraremos os resultados do exame das teses e das dissertações. Em seguida, refletiremos acerca dos artigos. Para a leitura e análise dos artigos e da produção discente, utilizamos como subsídio os referenciais da análise de conteúdo, por meio da análise categorial (BARDIN, 2008). Ao final, apresentaremos os caminhos abertos para pesquisas futuras e as recomendações da produção investigada para a implementação da Lei nº 10.639/2003

Reasons for inpatients not to seek clarity at Dr George Mukhari Academic Hospital, Pretoria

Background: Healthcare practitioners should provide patients with information regarding their clinical conditions. Patients should also feel free to seek clarity on information provided. However, not all patients seek this clarity. Objectives: To explore the reasons inpatients gave for not seeking clarity on information that was received but not understood. Methods: This was a qualitative arm of a larger study, titled ‘Are inpatients aware of the admission reasons and management plans of their clinical conditions? A survey at a tertiary hospital in South Africa’, conducted in 2010. Of the 264 inpatients who participated in the larger study, we extracted the unstructured responses from those participants (n = 152) who had indicated in the questionnaire that there was information they had not understood during their encounter with healthcare practitioners, but that they had nonetheless not sought clarity.Data were analysed thematically. Results: Themes that emerged were that inpatients did not ask for clarity as they perceived healthcare practitioners to be ‘too busy’, aloof, non-communicators and sometimes uncertain about patients’ conditions. Some inpatients had unquestioning trust in healthcare practitioners,whilst others had experiences of bad treatment. Inpatients had poor self-esteem, incapacitating clinical conditions, fear of bad news and prior knowledge of their clinical conditions. Some inpatients stated that they had no reason for not seeking clarity. Conclusion: The reasons for not seeking clarity were based on patients’ experiences with the healthcare practitioners and their perceptions of the latter and of themselves. A programme should be developed in order to educate inpatients on effective communication with their healthcare practitioners