title: In situ mixing of organic matter decreases hydraulic conductivity of denitrification walls in sand aquifers

authors: Barkle, Gregory F.

abstract: In a previous study, a denitrification wall was constructed in a sand aquifer using sawdust as the carbon substrate. Ground water bypassed around this sawdust wall due to reduced hydraulic conductivity. We investigated potential reasons for this by testing two new walls and conducting laboratory studies. The first wall was constructed by mixing aquifer material in situ without substrate addition to investigate the effects of the construction technique (mixed wall). A second, biochip wall, was constructed using coarse wood chips to determine the effect of size of the particles in the amendment on hydraulic conductivity. The aquifer hydraulic conductivity was 35.4 m/d, while in the mixed wall it was 2.8 m/d and in the biochip wall 3.4 m/d. This indicated that the mixing of the aquifer sands below the water table allowed the particles to re-sort themselves into a matrix with a significantly lower hydraulic conductivity than the process that originally formed the aquifer. The addition of a coarser substrate in the biochip wall significantly increased total porosity and decreased bulk density, but hydraulic conductivity remained low compared to the aquifer. Laboratory cores of aquifer sand mixed under dry and wet conditions mimicked the reduction in hydraulic conductivity observed in the field within the mixed wall. The addition of sawdust to the laboratory cores resulted in a significantly higher hydraulic conductivity when mixed dry compared to cores mixed wet. This reduction in the hydraulic conductivity of the sand/sawdust cores mixed under saturated conditions repeated what occurred in the field in the original sawdust wall. This indicated that laboratory investigations can be a useful tool to highlight potential reductions in field hydraulic conductivities that may occur when differing materials are mixed under field conditions.

text: In situ mixing of organic matter decreases hydraulic conductivity of denitrification walls in sand aquifers In a previous study, a denitrification wall was constructed in a sand aquifer using sawdust as the carbon substrate. Ground water bypassed around this sawdust wall due to reduced hydraulic conductivity. We investigated potential reasons for this by testing two new walls and conducting laboratory studies. The first wall was constructed by mixing aquifer material in situ without substrate addition to investigate the effects of the construction technique (mixed wall). A second, biochip wall, was constructed using coarse wood chips to determine the effect of size of the particles in the amendment on hydraulic conductivity. The aquifer hydraulic conductivity was 35.4 m/d, while in the mixed wall it was 2.8 m/d and in the biochip wall 3.4 m/d. This indicated that the mixing of the aquifer sands below the water table allowed the particles to re-sort themselves into a matrix with a significantly lower hydraulic conductivity than the process that originally formed the aquifer. The addition of a coarser substrate in the biochip wall significantly increased total porosity and decreased bulk density, but hydraulic conductivity remained low compared to the aquifer. Laboratory cores of aquifer sand mixed under dry and wet conditions mimicked the reduction in hydraulic conductivity observed in the field within the mixed wall. The addition of sawdust to the laboratory cores resulted in a significantly higher hydraulic conductivity when mixed dry compared to cores mixed wet. This reduction in the hydraulic conductivity of the sand/sawdust cores mixed under saturated conditions repeated what occurred in the field in the original sawdust wall. This indicated that laboratory investigations can be a useful tool to highlight potential reductions in field hydraulic conductivities that may occur when differing materials are mixed under field conditions.

year: 2008

title: Anisotropic scaling of magnetohydrodynamic turbulence

authors: Horbury, Timothy S.

subjects: mathematics

abstract: We present a quantitative estimate of the anisotropic power and scaling of magnetic field fluctuations in inertial range magnetohydrodynamic turbulence, using a novel wavelet technique applied to spacecraft measurements in the solar wind. We show for the first time that, when the local magnetic field direction is parallel to the flow, the spacecraft-frame spectrum has a spectral index near 2. This can be interpreted as the signature of a population of fluctuations in field-parallel wavenumbers with a k║-2 spectrum but is also consistent with the presence of a "critical balance" style turbulent cascade. We also find, in common with previous studies, that most of the power is contained in wavevectors at large angles to the local magnetic field and that this component of the turbulence has a spectral index of 5/3.

text: Anisotropic scaling of magnetohydrodynamic turbulence We present a quantitative estimate of the anisotropic power and scaling of magnetic field fluctuations in inertial range magnetohydrodynamic turbulence, using a novel wavelet technique applied to spacecraft measurements in the solar wind. We show for the first time that, when the local magnetic field direction is parallel to the flow, the spacecraft-frame spectrum has a spectral index near 2. This can be interpreted as the signature of a population of fluctuations in field-parallel wavenumbers with a k║-2 spectrum but is also consistent with the presence of a "critical balance" style turbulent cascade. We also find, in common with previous studies, that most of the power is contained in wavevectors at large angles to the local magnetic field and that this component of the turbulence has a spectral index of 5/3.

year: 2008

title: Rising demand for health care: The sustainability of community general practice in the Waikato

authors: Amey, Janet Heather

subjects: General practice

abstract: Community general practice is the cornerstone of New Zealand’s health system, providing first contact health care, care coordination and acting as gatekeeper to expensive hospital services. An ageing population now brings increasing demand for the care provided in general practice, with chronic conditions a major contributing factor. This rising demand, alongside limited workforce capacity will seriously test general practice sustainability. 

These evolving and multifaceted challenges are within the context of long-standing health access and outcome inequalities, particularly for Māori (and more recently the Pacific population) compared with Pākehā. The pursuit of equity is inherent in all health sector strategies, but any meaningful improvement will necessitate wide-ranging reform of current planning, funding and service delivery pathways across traditional sector boundaries.

The sustainability of general practice is about the sustainability and efficiency of the entire health system. To better measure the contribution of general practice care to the system, and improve demand projections, an expanded service use measure was developed, combining services of a general practice nature from Emergency Department and Accident & Medical settings with services delivered in community general practice.

Drawing on approaches from demography, epidemiology and health services research, linked demographic and health administrative data were used to undertake a retrospective, observational study of service use for 235,666 people enrolled with the Pinnacle Midlands Health Network in 2013/14. Using the new expanded measure, service use levels at a locality level were established by age, gender, ethnic group, chronic condition status, practice funding model, high needs status, income and geography of residence.

Significant variation was found in annual average consults (1.0 to 13.4 consults in 2013/14). Statistical analysis identified age, chronic conditions and gender as the key demand drivers responsible for such variation, with regional level results masking significant spatial variation. Where the cost of care was lower, people used a higher level of services in the enrolled practice setting and a lower level outside of it, suggesting the importance of affordable care. Māori and Pacific used significantly fewer services than Pākehā although there was substantial sub-regional variation. Using the expanded measure, the vast majority of care was delivered in the enrolled setting, including for those with chronic conditions.

Demand projections, based on the expanded measure of general practice, out to 2038 show the uneven geography of future demand due to disordered cohort flows and sub-regional population contexts. Overall, demand for services is projected to rise by 34 per cent to almost two million consults across the Waikato District Health Board catchment, with this driven predominantly by services for those aged 65+ years (or 45+ years in Hamilton City, Waikato and Waipa Districts).

Models of care are being transformed as general practices and Primary Health Organisations look to the future. Reorganisation of work roles, improved use of health information and use of emerging health technologies will be required to re-configure general practice in preparation for an ageing future, and to eliminate recalcitrant health inequalities. Real and inclusive collaboration across traditional system boundaries is perhaps the greatest challenge to general practice sustainability.

text: Rising demand for health care: The sustainability of community general practice in the Waikato Community general practice is the cornerstone of New Zealand’s health system, providing first contact health care, care coordination and acting as gatekeeper to expensive hospital services. An ageing population now brings increasing demand for the care provided in general practice, with chronic conditions a major contributing factor. This rising demand, alongside limited workforce capacity will seriously test general practice sustainability. 

These evolving and multifaceted challenges are within the context of long-standing health access and outcome inequalities, particularly for Māori (and more recently the Pacific population) compared with Pākehā. The pursuit of equity is inherent in all health sector strategies, but any meaningful improvement will necessitate wide-ranging reform of current planning, funding and service delivery pathways across traditional sector boundaries.

The sustainability of general practice is about the sustainability and efficiency of the entire health system. To better measure the contribution of general practice care to the system, and improve demand projections, an expanded service use measure was developed, combining services of a general practice nature from Emergency Department and Accident & Medical settings with services delivered in community general practice.

Drawing on approaches from demography, epidemiology and health services research, linked demographic and health administrative data were used to undertake a retrospective, observational study of service use for 235,666 people enrolled with the Pinnacle Midlands Health Network in 2013/14. Using the new expanded measure, service use levels at a locality level were established by age, gender, ethnic group, chronic condition status, practice funding model, high needs status, income and geography of residence.

Significant variation was found in annual average consults (1.0 to 13.4 consults in 2013/14). Statistical analysis identified age, chronic conditions and gender as the key demand drivers responsible for such variation, with regional level results masking significant spatial variation. Where the cost of care was lower, people used a higher level of services in the enrolled practice setting and a lower level outside of it, suggesting the importance of affordable care. Māori and Pacific used significantly fewer services than Pākehā although there was substantial sub-regional variation. Using the expanded measure, the vast majority of care was delivered in the enrolled setting, including for those with chronic conditions.

Demand projections, based on the expanded measure of general practice, out to 2038 show the uneven geography of future demand due to disordered cohort flows and sub-regional population contexts. Overall, demand for services is projected to rise by 34 per cent to almost two million consults across the Waikato District Health Board catchment, with this driven predominantly by services for those aged 65+ years (or 45+ years in Hamilton City, Waikato and Waipa Districts).

Models of care are being transformed as general practices and Primary Health Organisations look to the future. Reorganisation of work roles, improved use of health information and use of emerging health technologies will be required to re-configure general practice in preparation for an ageing future, and to eliminate recalcitrant health inequalities. Real and inclusive collaboration across traditional system boundaries is perhaps the greatest challenge to general practice sustainability.

year: 2018