Bush Encroachment Control and Risk Management in Semi-Arid Rangelands

We study the role of bush encroachment control for a farmer's income and income risk in a stochastic ecological-economic model of grazing management in semiarid rangelands. In particular, we study debushing as an instrument of risk management that complements the choice of an adaptive grazing management strategy for that sake. We show that debushing, while being a good practice for increasing the mean pasture productivity and thus expected income, also increases the farmer's income risk. The optimal extent of debushing for a risk-averse farmer is thus determined from balancing the positive and negative consequences of debushing on intertemporal and stochastic farm income

Vegetation Responses to Climate Variability in the Northern Arid to Sub-Humid Zones of Sub-Saharan Africa

In water limited environments precipitation is often considered the key factor influencing vegetation growth and rates of development. However; other climate variables including temperature; humidity; the frequency and intensity of precipitation events are also known to affect productivity; either directly by changing photosynthesis and transpiration rates or indirectly by influencing water availability and plant physiology. The aim here is to quantify the spatiotemporal patterns of vegetation responses to precipitation and to additional; relevant; meteorological variables. First; an empirical; statistical analysis of the relationship between precipitation and the additional meteorological variables and a proxy of vegetation productivity (the Normalized Difference Vegetation Index; NDVI) is reported and; second; a process-oriented modeling approach to explore the hydrologic and biophysical mechanisms to which the significant empirical relationships might be attributed. The analysis was conducted in Sub-Saharan Africa; between 5 and 18°N; for a 25-year period 1982–2006; and used a new quasi-daily Advanced Very High Resolution Radiometer (AVHRR) dataset. The results suggest that vegetation; particularly in the wetter areas; does not always respond directly and proportionately to precipitation variation; either because of the non-linearity of soil moisture recharge in response to increases in precipitation; or because variations in temperature and humidity attenuate the vegetation responses to changes in water availability. We also find that productivity; independent of changes in total precipitation; is responsive to intra-annual precipitation variation. A significant consequence is that the degree of correlation of all the meteorological variables with productivity varies geographically; so no one formulation is adequate for the entire region. Put together; these results demonstrate that vegetation responses to meteorological variation are more complex than an equilibrium relationship between precipitation and productivity. In addition to their intrinsic interest; the findings have important implications for detection of anthropogenic dryland degradation (desertification); for which the effects of natural fluctuations in meteorological variables must be controlled in order to reveal non-meteorological; including anthropogenic; degradation

Beyond Hyperkalemia: β-Blocker–Induced Cardiac Arrest for Normothermic Cardiac Operations

Background. Four experimental protocols were carried out to assess the ability of esmolol to induce and maintain reversible cardiac arrest under continuous normothermic (37°C) perfusion. Methods and Results. In the first protocol, 8 perfused rat hearts were subjected to 20, 60, 90, and 120 minutes of esmolol arrest, after which positive and negative first derivative of pressure, heart rate, left ventricular developed pressure, and left ventricular end-diastolic pressure were evaluated. Arrest was achieved 45 to 60 seconds after beginning the infusion of esmolol. Mechanical arrest was achieved before electrical arrest. In the second protocol, dose-response curves were obtained using isolated (Langendorff) rat and rabbit (n = 6) hearts. The concentrations of esmolol varied from 0.084 to 6.7 mmol/L and from 0.12 to 1.45 mmol/L in the rat and rabbit heart experiments, respectively. In the third protocol, the effects of 20 minutes of normothermic (37°C) ischemia on the function of isolated rat hearts perfused with esmolol-containing Krebs solution were compared with those using high-potassium (25 mmol/L) Krebs solution. Group A subjects (n = 9) received the ischemic injury after being perfused (and arrested) for 20 minutes with either esmolol or potassium (KCl, 25 mmol/L). Group B subjects (n = 10) received the same ischemic insult before being perfused with either esmolol or potassium. Esmolol-treated hearts showed better recovery than those receiving potassium, in terms of ±dP/dt ( p < 0.01), left ventricular systolic pressure ( p < 0.01), and left ventricular developed pressure ( p < 0.009). Finally, the fourth protocol was done to evaluate the effects of esmolol in a clinically relevant experimental model. Pigs were divided into esmolol (n = 6) and potassium (n = 5) groups and subjected to normothermic cardiopulmonary bypass and a 1-hour period of cardiac arrest. Twenty minutes after stopping infusion of the cardioplegic agents, all animals were weaned off bypass. There were no statistically significant differences between the groups. Conclusions. Esmolol hydrochloride can be used as effectively as potassium for inducing and maintaining predictable and reversible cardiac arrest during normothermic cardiac operations

Beyond hyperkalemia: beta-blocker-induced cardiac arrest for normothermic cardiac operations

NRC publication: Ye

Hanging donor lungs give good short‐, mid‐ and long‐term results in lung transplantation

International audienceAbstract Background Hanging donors are considered as marginal donors and frequently unsuitable for lung transplantation. However, there is no evidence of higher lung transplantation (LTx) morbidity‐mortality with lungs providing by hanging donor. Methods Between January 2010 and July 2015, we performed a retrospective study at Foch hospital. We aimed to assess whether hanging donor grafts are suitable for lung transplantation. Results A total of 299 LTx were performed. Subjects were allocated to a hanging group (HG) (n = 20) and a control group (CG) (n = 279). Donor and recipient characteristics did not differ. Primary graft dysfunction (PGD) at 72 hours was comparable in both groups ( P = .75). The median duration of postoperative mechanical ventilation (1 [range, 0‐84] vs 1 [range, 0‐410] day, P = .35), the hospital length of stay (31 days [20‐84] vs 32 days [12‐435], P = .36) did not differ between the two groups. No statistically significant difference was found in 1‐year and 5‐year survival between the HG (83% and 78%) and the CG (86% and 75%), P = .85. Conclusion We believe that hanging donors should be considered as conventional donors with particular caution in the final evaluation of the graft and in perioperative management