Continuous, 8-Paddock, and 16-Paddock Grazing at Two Stocking Rates With Different Breed Types

Last updated: 6/12/200

Data-constrained assessment of ocean circulation changes since the middle Miocene in an Earth system model

Since the middle Miocene (15 Ma, million years ago), the Earth's climate has undergone a long-term cooling trend, characterised by a reduction in ocean temperatures of up to 7–8 ∘C. The causes of this cooling are primarily thought to be due to tectonic plate movements driving changes in large-scale ocean circulation patterns, and hence heat redistribution, in conjunction with a drop in atmospheric greenhouse gas forcing (and attendant ice-sheet growth and feedback). In this study, we assess the potential to constrain the evolving patterns of global ocean circulation and cooling over the last 15 Ma by assimilating a variety of marine sediment proxy data in an Earth system model. We do this by first compiling surface and benthic ocean temperature and benthic carbon-13 (δ13C) data in a series of seven time slices spaced at approximately 2.5 Myr intervals. We then pair this with a corresponding series of tectonic and climate boundary condition reconstructions in the cGENIE (“muffin” release) Earth system model, including alternative possibilities for an open vs. closed Central American Seaway (CAS) from 10 Ma onwards. In the cGENIE model, we explore uncertainty in greenhouse gas forcing and the magnitude of North Pacific to North Atlantic salinity flux adjustment required in the model to create an Atlantic Meridional Overturning Circulation (AMOC) of a specific strength, via a series of 12 (one for each tectonic reconstruction) 2D parameter ensembles. Each ensemble member is then tested against the observed global temperature and benthic δ13C patterns. We identify that a relatively high CO2 equivalent forcing of 1120 ppm is required at 15 Ma in cGENIE to reproduce proxy temperature estimates in the model, noting that this CO2 forcing is dependent on the cGENIE model's climate sensitivity and that it incorporates the effects of all greenhouse gases. We find that reproducing the observed long-term cooling trend requires a progressively declining greenhouse gas forcing in the model. In parallel to this, the strength of the AMOC increases with time despite a reduction in the salinity of the surface North Atlantic over the cooling period, attributable to falling intensity of the hydrological cycle and to lowering polar temperatures, both caused by CO2-driven global cooling. We also find that a closed CAS from 10 Ma to present shows better agreement between benthic δ13C patterns and our particular series of model configurations and data. A final outcome of our analysis is a pronounced ca. 1.5 ‰ decline occurring in atmospheric (and ca. 1 ‰ ocean surface) δ13C that could be used to inform future δ13C-based proxy reconstructions.</p

Improving cost-effectiveness of hypertension management at a community health centre

Objectives. To describe the pattern of prescribing for hypertension at a community health centre (CHC) and to evaluate the impact of introducing treatment guidelines and restricting availability of less cost-effective antihypertensive drugs on prescribing patterns, costs of drug treatment and blood pressure (BP) control.Design. Before/after intervention study.Setting. Medium-sized CHC in the Cape Flats area of Cape Town.Subjects. 1 084 hypertensive patients attending the CHC, who had at least two prescriptions for antihypertensive drugs during a 1-year period starting on 1 January 1992. Interventions. 1. Implementation of stepped-care guidelines for hypertension, specifying treatment with more cost-effective drugs and minimising drug treatment. 2. Reducing availability for routine prescribing by CHC doctors of 10 less cost-effective antihypertensive drugs or drug combinations.Outcome measures. 1. Mean number of drugs prescribed per patient. 2. Proportion of prescriptions for: each major class of antihypertensive drug; restricted availability and freely prescribable drugs; and more and less cost-effective drugs. 3. Mean monthly cost of drugs prescribed per patient. 4. Mean blood pressure and proportion of BP readings controlled (&lt;160/95 mmHg) or uncontrolled (≥160/95 mmHg).Results. A mean of 1.7 active drugs was prescribed per patient per visit. The most frequently prescribed drugs were thiazide-like diuretics (44.8%), centrally acting agents (28.4%) and b-blockers (13.2%). Mean monthly drug costs per patient decreased significantly by R1.99 (24.2%) from R8.24 to R6.25 between the first and last prescription for each patient (exclusive of any reduction due to withdrawal of treatment). This was attributable to reduced prescribing of more expensive drugs withdrawn from routine use and a 51.1% increase in prescribing of the most cost-effective drugs. The overall annual cost-saving of the changes in prescribing for this CHC are estimated at R75 150. Blood pressure control did not change significantly.Conclusion. The pattern of changes in prescribing and drug costs was consistent with a causal effect of the interventions. The study demonstrates the potential forimproving cost-effectiveness of hypertension care in primary care in South Africa and the potential for research in this setting

Hypertension care at a Cape Town community health centre

Objectives. To describe the demographic profile of hypertensive patients and the quality of care for hypertension at a Cape Town community health centre (CHC).Design. Prospective, descriptive study.Setting and subjects. Medium-sized CHC, attended by 1098 hypertensive patients during a 1-year period from 1 January 1992.Outcome measures. Default rate - proportion of due visits not attended. Loss to follow-up - proportion of patients persistently defaulting or not responding to recall. Frequency of blood pressure measurement - per 12 due visits. Compliance - proportion of patients collecting ≥ 75% of antihypertensive drugs. Blood pressure control - mean blood pressure of aggregated readings; and proportion controlled (&lt;160/95 mmHg) on the basis of all blood pressure readings and mean blood pressures of individual patients with two or more readings during the study period.Results. More than half (51.6%) of the hypertensive patients were aged ≥ 65 years; 81.7% were female. The default rate was between 11.9% and 19.4%. Compliance was high (76.9%). Loss to follow-up was 8.1 %. Blood pressure was recorded a mean of 4.0 times per 12 due visits. There were no significant gender differences with regard to these measures. Mean blood pressure was 158.3/89.6 mmHg. Over half (56.7%) of all individual readings over the year were uncontrolled and 51.4% of patients were found to be uncontrolled when categorised by their mean blood pressure. Control was significantly poorer among women ≥ 65 years.Conclusion. We found better compliance, more frequent blood pressure measurement, and lower defaulting and loss to follow-up compared with previous South African studies in similar settings. Despite this, blood pressure control was mediocre. Possible explanations for this are discussed. The low proportion of male hypertensives attending the CHC suggests that the accessibility or acceptability of care is poor for this group. The study illustrates the potential for research in this setting and for the use of computers to monitor the quality of primary care.

Quantifying the Effect of the Drake Passage Opening on the Eocene Ocean

The opening of the Drake Passage (DP) during the Cenozoic is a tectonic event of paramount importance for the development of modern ocean characteristics. Notably, it has been suggested that it exerts a primary role in the onset of the Antarctic Circumpolar Current (ACC) formation, in the cooling of high- latitude South Atlantic waters and in the initiation of North Atlantic Deep Water (NADW) formation. Several model studies have aimed to assess the impacts of DP opening on climate, but most of them focused on surface climate, and only few used realistic Eocene boundary conditions. Here, we revisit the impact of the DP opening on ocean circulation with the IPSL- CM5A2 Earth System Model. Using appropriate middle Eocene (40 Ma) boundary conditions, we perform and analyze simulations with different depths of the DP (0, 100, 1,000, and 2,500 m) and compare results to existing geochemical data. Our experiments show that DP opening has a strong effect on Eocene ocean structure and dynamics even for shallow depths. The DP opening notably allows the formation of a proto- ACC and induces deep ocean cooling of 1.5°C to 2.5°C in most of the Southern Hemisphere. There is no NADW formation in our simulations regardless of the depth of the DP, suggesting that the DP on its own is not a primary control of deepwater formation in the North Atlantic. This study elucidates how and to what extent the opening of the DP contributed to the establishment of the modern global thermohaline circulation.Key PointsA shallow opening of the Drake Passage induces strong changes in ocean properties and dynamicsA proto- ACC is able to form during the Eocene under high levels of pCO2, but a strong ACC requires supplementary geographical changesNorth Atlantic Deep Water is probably not able to form before the separation of the Arctic and Atlantic OceansPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/156423/3/palo20904-sup-0001-2020PA003889-SI.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/156423/2/palo20904.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/156423/1/palo20904_am.pd