title: Mechanism for grain refinement of magnesium alloys by superheating

authors: Cao, Peng

subjects: Magnesium alloys

abstract: The mechanisms for grain refinement of magnesium alloys by superheating have remained ambiguous since 1931. A model has been proposed on the basis of the recent understanding of the grain refinement of both high purity and commercial purity Mg–Al alloys. The model explains most of the experimental observations about superheating. Analysis of the grain size data obtained from different Mg–Al alloys as a function of the growth restriction factor with and without superheating provides good support to the model.

text: Mechanism for grain refinement of magnesium alloys by superheating The mechanisms for grain refinement of magnesium alloys by superheating have remained ambiguous since 1931. A model has been proposed on the basis of the recent understanding of the grain refinement of both high purity and commercial purity Mg–Al alloys. The model explains most of the experimental observations about superheating. Analysis of the grain size data obtained from different Mg–Al alloys as a function of the growth restriction factor with and without superheating provides good support to the model.

year: 2007-04

title: The role of intratidal oscillations in sediment resuspension in a diurnal, partially mixed estuary

authors: O’Callaghan, J.M.

subjects: diurnal tides

abstract: Using detailed observations of the mean and turbulent properties of flow, salinity and turbidity that spanned 2001/02, we examined the physical mechanisms underpinning sediment resuspension in the low-energy Swan River estuary, Western Australia. In this diurnal tidally-dominated estuary, the presence of intratidal oscillations, a tidal inequality lasting 2 to 3 hours on the flood tide, generated by interactions of the four main diurnal and semidiurnal astronomical constituents, K₁, O₁, M₂, and S₂, played a major role in modifying vertical stratification and mixing. These intratidal oscillations are controlled by phase differences between the tropic and synodic months rather than being temporally-fixed by bed friction, as occurs in semidiurnal estuaries. Intratidal oscillations are largest, at around 0.1 m, near to the Austral solstice when the lunar and solar declination are in-phase. Despite the seemingly small change in water level, shear-induced interfacial mixing caused destratification of the water column with the top-to-bottom salinity (ΔS) difference of 3.5 present early in the flood tide eroded to less than 0.3 by the end of the intratidal oscillation. High turbidity peaks, of 250 nephelometric turbidity units, coincided with these intratidal oscillations and could not be explained by bed friction since shear stress from mean flow did not exceed threshold criteria. High Reynolds stresses of ∼1 Nm⁻² did, however, exceed τcr and together with negative Reynolds fluxes indicate a net downward transport of material. Destratification of the water column induced by shear instabilities resulted in large overturns capable of moving in situ material towards the bed during intratidal oscillations and these turbidities were ∼10 times greater than those from bed-generated resuspension observed later during the flood tide.

text: The role of intratidal oscillations in sediment resuspension in a diurnal, partially mixed estuary Using detailed observations of the mean and turbulent properties of flow, salinity and turbidity that spanned 2001/02, we examined the physical mechanisms underpinning sediment resuspension in the low-energy Swan River estuary, Western Australia. In this diurnal tidally-dominated estuary, the presence of intratidal oscillations, a tidal inequality lasting 2 to 3 hours on the flood tide, generated by interactions of the four main diurnal and semidiurnal astronomical constituents, K₁, O₁, M₂, and S₂, played a major role in modifying vertical stratification and mixing. These intratidal oscillations are controlled by phase differences between the tropic and synodic months rather than being temporally-fixed by bed friction, as occurs in semidiurnal estuaries. Intratidal oscillations are largest, at around 0.1 m, near to the Austral solstice when the lunar and solar declination are in-phase. Despite the seemingly small change in water level, shear-induced interfacial mixing caused destratification of the water column with the top-to-bottom salinity (ΔS) difference of 3.5 present early in the flood tide eroded to less than 0.3 by the end of the intratidal oscillation. High turbidity peaks, of 250 nephelometric turbidity units, coincided with these intratidal oscillations and could not be explained by bed friction since shear stress from mean flow did not exceed threshold criteria. High Reynolds stresses of ∼1 Nm⁻² did, however, exceed τcr and together with negative Reynolds fluxes indicate a net downward transport of material. Destratification of the water column induced by shear instabilities resulted in large overturns capable of moving in situ material towards the bed during intratidal oscillations and these turbidities were ∼10 times greater than those from bed-generated resuspension observed later during the flood tide.

year: 2010

title: Medications and meanings in Maori households with chronic illnesses

authors: Carlson, Teah

subjects: medications

abstract: Domestic spaces have always featured as sites for health care. The home is increasingly referred to as a new therapeutic space within which chronic illnesses are managed within everyday life. This research explores the meanings and use of medications within four Māori households containing at least one chronically ill householder. A broad ethnographic approach was used to capture popular understandings and medication use in daily life. Multiple methods were used, including group discussions with household members, individual interviews, household mapping, and photographic and diary elicitation tasks. Findings shed light on the sources and uses of medications, householder knowledge of medications, communal practices of sharing, caring, rationalising use, grappling with side-effects and the management of illness. I consider what it means for householders to take medications themselves or give these to others, and the care-giving practices that feature in the everyday consumption of medicines. The research is based on the premise that medications are material objects with therapeutic uses that enter into and take on meaning within people’s lives. Medications become culturally embedded phenomena that carry meanings and shape social relationships and practices with Māori households. As such, medications were used in a way that reflected the cultural values and bonds within the households. Within household relationships, medications were invested within meaning to show aroha, support and care. Within a Māori whānau context, the values of maanakitanga, rangatiratanga, and whanaungatanga were recognised as having an integral role in understanding the social practices with medications in each household.

text: Medications and meanings in Maori households with chronic illnesses Domestic spaces have always featured as sites for health care. The home is increasingly referred to as a new therapeutic space within which chronic illnesses are managed within everyday life. This research explores the meanings and use of medications within four Māori households containing at least one chronically ill householder. A broad ethnographic approach was used to capture popular understandings and medication use in daily life. Multiple methods were used, including group discussions with household members, individual interviews, household mapping, and photographic and diary elicitation tasks. Findings shed light on the sources and uses of medications, householder knowledge of medications, communal practices of sharing, caring, rationalising use, grappling with side-effects and the management of illness. I consider what it means for householders to take medications themselves or give these to others, and the care-giving practices that feature in the everyday consumption of medicines. The research is based on the premise that medications are material objects with therapeutic uses that enter into and take on meaning within people’s lives. Medications become culturally embedded phenomena that carry meanings and shape social relationships and practices with Māori households. As such, medications were used in a way that reflected the cultural values and bonds within the households. Within household relationships, medications were invested within meaning to show aroha, support and care. Within a Māori whānau context, the values of maanakitanga, rangatiratanga, and whanaungatanga were recognised as having an integral role in understanding the social practices with medications in each household.

year: 2010