The dynamics of a low-order coupled ocean-atmosphere model

A system of five ordinary differential equations is studied which combines the Lorenz-84 model for the atmosphere and a box model for the ocean. The behaviour of this system is studied as a function of the coupling parameters. For most parameter values, the dynamics of the atmosphere model is dominant. For a range of parameter values, competing attractors exist. The Kaplan-Yorke dimension and the correlation dimension of the chaotic attractor are numerically calculated and compared to the values found in the uncoupled Lorenz model. In the transition from periodic behaviour to chaos intermittency is observed. The intermittent behaviour occurs near a Neimark-Sacker bifurcation at which a periodic solution loses its stability. The length of the periodic intervals is governed by the time scale of the ocean component. Thus, in this regime the ocean model has a considerable influence on the dynamics of the coupled system.Comment: 20 pages, 15 figures, uses AmsTex, Amssymb and epsfig package. Submitted to the Journal of Nonlinear Scienc

The dynamics of a low-order coupled ocean-atmosphere model

A system of ve ordinary dierential equations is studied which combines the Lorenz model for the atmosphere and a box model for the ocean The behaviour of this system is studied as a function of the coupling parameters For most parameter values the dynamics of the atmosphere model is dominant Stable equilibria are found as well as periodic solutions and chaotic attractors For a range of parameter values competing attractors exist The KaplanYorke dimension and the correlation dimension of the chaotic attractor are numerically calculated and compared to the values found in the uncoupled Lorenz model The correlation dimension diers much less than te KaplanYorke dimension indicating that there is little variability in the ocean model In the transition from periodic behaviour to chaos intermittency is observed This is explained by means of bifurcation analysis The intermittent behaviour occurs near a NeimarkSacker bifurcation at which a periodic solution loses its stability The average length of a periodic interval in the intermittent regime l is studied as a function of the bifurcation parameter Near the bifurcation point it shows a power law scaling It diverges as l where and is the distance from the bifurcation point in reasonable agreement with the results of Pomeau and Manneville Commun Math Phys The intermittent behaviour persists beyond the point where the unstable periodic solution disappears in a saddle node bifurcation The length of the periodic intervals is governed by the time scale of the ocean component Thus in this regime the ocean model has a considerable inuence on the dynamics of the coupled syste

Seroprevalence of Toxoplasma gondii in pregnant women and livestock in the mainland of China : a systematic review and hierarchical meta-analysis

Primary Toxoplasma gondii infection in pregnant women may result in abortion, stillbirth, or lifelong disabilities of the unborn child. One of the main transmission routes to humans is consumption of raw or undercooked meat containing T. gondii tissue cysts. We aim to determine and compare the regional distribution of T. gondii seroprevalence in pregnant women and meat-producing livestock in China through a systematic literature review. A total of 272 eligible publications were identified from Medline, Scopus, Embase and China National Knowledge Infrastructure. Apparent and true seroprevalence were analysed by region using a novel Bayesian hierarchical model that allowed incorporating sensitivity and specificity of the applied serological assays. The true seroprevalence of T. gondii in pregnant women was 5.0% or less in seven regions of China. The median of the regional true seroprevalences in pigs (24%) was significantly higher than in cattle (9.5%), but it was not significantly higher than in chickens (20%) and small ruminants (20%). This study represents the first use of a Bayesian hierarchical model to obtain regional true seroprevalence. These results, in combination with meat consumption data, can be used to better understand the contribution of meat-producing animals to human T. gondii infection in China

An initial intercomparison of atmospheric and oceanic climatology for the ICE-5G and ICE-4G models of LGM paleotopography

This paper investigates the impact of the new ICE-5G paleotopography dataset for Last Glacial Maximum (LGM) conditions on a coupled model simulation of the thermal and dynamical state of the glacial atmosphere and on both land surface and sea surface conditions. The study is based upon coupled climate simulations performed with the ocean–atmosphere–sea ice model of intermediate-complexity Climate de Bilt-coupled large-scale ice–ocean (ECBilt-Clio) model. Four simulations focusing on the Last Glacial Maximum [21 000 calendar years before present (BP)] have been analyzed: a first simulation (LGM-4G) that employed the original ICE-4G ice sheet topography and albedo, and a second simulation (LGM-5G) that employed the newly constructed ice sheet topography, denoted ICE-5G, and its respective albedo. Intercomparison of the results obtained in these experiments demonstrates that the LGM-5G simulation delivers significantly enhanced cooling over Canada compared to the LGM-4G simulation whereas positive temperature anomalies are simulated over southern North America and the northern Atlantic. Moreover, introduction of the ICE-5G topography is shown to lead to a deceleration of the subtropical westerlies and to the development of an intensified ridge over North America, which has a profound effect upon the hydrological cycle. Additionally, two flat ice sheet experiments were carried out to investigate the impact of the ice sheet albedo on global climate. By comparing these experiments with the full LGM simulations, it becomes evident that the climate anomalies between LGM-5G and LGM-4G are mainly driven by changes of the earth’s topography

Determinants of Return to Work in Patients with Hand Disorders and Hand Injuries

Introduction Return to work (RTW) in patients with hand disorders and hand injuries is determined by several determinants not directly related to the physical situation. Besides biomedical determinants, work-related and psychosocial determinants may influence RTW as well. This study is conducted to investigate the influence of these potential determinants on RTW in patients with hand disorders and hand injuries. Methods Included 91 patients who were operatively treated for a hand disorder or a hand injury, and who were employed prior to surgery. Patients answered several questionnaires on the aforementioned categories. Potential determinants significantly related to RTW in a univariate analysis were entered in a logistic regression for the total group and the acutely injured patients separately. Results Pain, accident location, job independence and symptoms of post-traumatic stress disorder (PTSD) were univariately associated with RTW. Pain was a determinant for late RTW in the total group and accident location and symptoms of PTSD in the acutely injured group. Conclusion Pain, accident location and symptoms of PTSD were most important in resuming work in hand injured patients or in patients with a hand disorder. These findings may indicate that attention should be paid to the treatment of pain, and to the development of symptoms of PTSD during rehabilitation. It may be necessary to make extra efforts aimed at RTW in patients who sustained their injury on the job

Consumers' preferences for freezing of meat to prevent toxoplasmosis- A stated preference approach.

Consumption of raw or undercooked meat increases the risk of infection with Toxoplasma gondii. Freezing meat products can eliminate this risk. Freezing of meat may affect consumers' valuation of meat products in two different ways: it may be valued positively because of increased food safety or valued negatively because of (perceived) loss of quality. In a Discrete Choice Experiment on four different meat products we studied the difference in willingness to pay for frozen and non-frozen meat products in the Netherlands. Analyses revealed that most Dutch consumer groups prefer non-frozen meat. Price was important in consumer decisions, whereas the meat being frozen appeared to play a minor role in the decision to purchase meat products. Even though it may seem obvious that people would prefer safe food to unsafe food, in a context where consumers presume food being safe, many consumers appear unwilling to pay for freezing of meat as additional measure to reduce the risk of food borne infections such as toxoplasmosis