CAN AGRICULTURAL PRODUCTION IN THE MARGINAL LANDS CONTRIBUTE TO IMPROVING FOOD SECURITY IN THE SAHELIAN AFRICAN COUNTRIES: AN EVIDENCE FROM THE BAS-FOND RICE PRODUCTION IN MALI

To improve national food security, successive Mali governments have always focused on expanding and intensifying production in the government-managed irrigation schemes (Office du Niger), which account for about 50% of domestic rice production. Because the cost of expanding and rehabilitating those schemes is high, the government is looking for complementary cost-effective ways to achieve this goal. The government could increase domestic rice supply by investing in improving the farmer-managed inland valley swamps. Although the government has paid little attention to those marginal lands, farmers have been growing rice in these areas using traditional technologies. This paper used data from a survey of 334 bas-fond farmers and secondary data to examine the potential contribution that these undeveloped bas-fonds could make to improve food security and rice exports in Mali. The study found that, if fully developed, the bas-fonds and flooded plains could produce more rice than is currently being supplied by the Office du Niger, or imported through commercial imports or food aid. As expected, rice yields in the bas-fonds are lower than in the Office du Niger. However, bas-fonds rice production is both financially profitable and provides a higher return per day of family labor than the competing upland crops (maize, sorghum/millet and cotton). In addition, the estimated domestic resources cost ratios show that, compared to the Office d u Niger, bas-fond rice production represents a better use of domestic resources, both for producing rice for home consumption and for the market.Crop Production/Industries, Food Security and Poverty, Land Economics/Use,

ON THE USE OF PRODUCTIVITY-INCREASING TECHNOLOGIES IN SUB-SAHARAN AFRICA: THE CASE OF INLAND VALLEY SWAMP RICE FARMING IN SOUTHERN MALI

There is no improved seed-fertilizer technology available that can generate the needed growth in agricultural production in Sub-Saharan Africa to meet food demand by the rapidly increasing population. This paper identifies factors associated with inland valley swamp rice farmers' decisions to adopt "improved" varieties and/or fertilizer. To achieve this objective, input-specific logistic models were estimated using survey-generated data collected from a random sample of 221 rice plots (one per farmer) selected from a purposive sample of 12 Mali-Sud bas-fond villages during the 1995-96 cropping season. The model estimation results show that the farther the village is from the closest market, the lower the probability to adopt the "improved" variety, increasing the size of the rice plot will decrease this probability, and men are more likely to adopt "improved" varieties than women because men have access to credit through CMDT, and more alternative sources of income to finance input purchases than women. For fertilizer, the use of "improved" varieties, the presence of water control infrastructure, and the village experience in cotton production increase the likelihood that a farmer will apply this input. The significance of the village experience in cotton production and women limited access to credit suggests that one of the constrains to a wider use of modern inputs is the absence of a reliable source of these inputs and/or seasonal credits. The significance of village distance to the closest market and the presence of water control the likelihood of using these inputs suggests that there exits some technological payoff associated with well-functioning markets and road improvements because such investments reduce the effective distance between the farm and the market.Crop Production/Industries, Research and Development/Tech Change/Emerging Technologies,

FINANCIAL PROFITABILITY OF MALI-SUD BAS-FOND RICE PRODUCTION SYSTEMS

The high costs of rehabilitating and/or expanding government-managed irrigated schemes in Mali (Office du Niger) has prompted policy-makers and researchers to explore the potential for the underdeveloped farmer-managed bas-fond to contribute to ensure an adequate rice supply and increase rural households' incomes. Because little is known about nas-fond rice production in Mali, this paper analyzes its financial profitability based on data collected from a random sample of 221 farmers. Data analysis revealed that there are numerous rice production systems in the bas-fond. Budget analysis showed that the four most common bas-fond production systems yield higher returns than the opportunity cost of labor and they are more profitable than the main upland crops competing with rice for farmers labor (cotton, sorghum/millet, and maize). Within a given bas-fond system, however, profitability varies considerably across farms.Agricultural Finance, Crop Production/Industries,

Variational Approximations in a Path-Integral Description of Potential Scattering

Using a recent path integral representation for the T-matrix in nonrelativistic potential scattering we investigate new variational approximations in this framework. By means of the Feynman-Jensen variational principle and the most general ansatz quadratic in the velocity variables -- over which one has to integrate functionally -- we obtain variational equations which contain classical elements (trajectories) as well as quantum-mechanical ones (wave spreading).We analyse these equations and solve them numerically by iteration, a procedure best suited at high energy. The first correction to the variational result arising from a cumulant expansion is also evaluated. Comparison is made with exact partial-wave results for scattering from a Gaussian potential and better agreement is found at large scattering angles where the standard eikonal-type approximations fail.Comment: 35 pages, 3 figures, 6 tables, Latex with amsmath, amssymb; v2: 28 pages, EPJ style, misprints corrected, note added about correct treatment of complex Gaussian integrals with the theory of "pencils", matches published versio

Atmospheric Composition Change: Climate-Chemistry Interactions

Chemically active climate compounds are either primary compounds such as methane (CH4), removed by oxidation in the atmosphere, or secondary compounds such as ozone (O3), sulfate and organic aerosols, formed and removed in the atmosphere. Man-induced climate-chemistry interaction is a two-way process: Emissions of pollutants change the atmospheric composition contributing to climate change through the aforementioned climate components, and climate change, through changes in temperature, dynamics, the hydrological cycle, atmospheric stability, and biosphere-atmosphere interactions, affects the atmospheric composition and oxidation processes in the troposphere. Here we present progress in our understanding of processes of importance for climate-chemistry interactions, and their contributions to changes in atmospheric composition and climate forcing. A key factor is the oxidation potential involving compounds such as O3 and the hydroxyl radical (OH). Reported studies represent both current and future changes. Reported results include new estimates of radiative forcing based on extensive model studies of chemically active climate compounds such as O3, and of particles inducing both direct and indirect effects. Through EU projects such as ACCENT, QUANTIFY, and the AEROCOM project, extensive studies on regional and sector-wise differences in the impact on atmospheric distribution are performed. Studies have shown that land-based emissions have a different effect on climate than ship and aircraft emissions, and different measures are needed to reduce the climate impact. Several areas where climate change can affect the tropospheric oxidation process and the chemical composition are identified. This can take place through enhanced stratospheric-tropospheric exchange of ozone, more frequent periods with stable conditions favouring pollution build up over industrial areas, enhanced temperature-induced biogenic emissions, methane releases from permafrost thawing, and enhanced concentration through reduced biospheric uptake. During the last 510 years, new observational data have been made available and used for model validation and the study of atmospheric processes. Although there are significant uncertainties in the modelling of composition changes, access to new observational data has improved modelling capability. Emission scenarios for the coming decades have a large uncertainty range, in particular with respect to regional trends, leading to a significant uncertainty range in estimated regional composition changes and climate impact

Casimir effect for a dilute dielectric ball at finite temperature

The Casimir effect at finite temperature is investigated for a dilute dielectric ball; i.e., the relevant internal and free energies are calculated. The starting point in this study is a rigorous general expression for the internal energy of a system of noninteracting oscillators in terms of the sum over the Matsubara frequencies. Summation over the angular momentum values is accomplished in a closed form by making use of the addition theorem for the relevant Bessel functions. For removing the divergences the renormalization procedure is applied that has been developed in the calculation of the corresponding Casimir energy at zero temperature. The behavior of the thermodynamic characteristics in the low and high temperature limits is investigated.Comment: 15 pages, REVTeX, no figures, no tables; editor corrections are introduced, version published in Phys. Rev. D 1

Why Are Outcomes Different for Registry Patients Enrolled Prospectively and Retrospectively? Insights from the Global Anticoagulant Registry in the FIELD-Atrial Fibrillation (GARFIELD-AF).

Background: Retrospective and prospective observational studies are designed to reflect real-world evidence on clinical practice, but can yield conflicting results. The GARFIELD-AF Registry includes both methods of enrolment and allows analysis of differences in patient characteristics and outcomes that may result. Methods and Results: Patients with atrial fibrillation (AF) and ≥1 risk factor for stroke at diagnosis of AF were recruited either retrospectively (n = 5069) or prospectively (n = 5501) from 19 countries and then followed prospectively. The retrospectively enrolled cohort comprised patients with established AF (for a least 6, and up to 24 months before enrolment), who were identified retrospectively (and baseline and partial follow-up data were collected from the emedical records) and then followed prospectively between 0-18 months (such that the total time of follow-up was 24 months; data collection Dec-2009 and Oct-2010). In the prospectively enrolled cohort, patients with newly diagnosed AF (≤6 weeks after diagnosis) were recruited between Mar-2010 and Oct-2011 and were followed for 24 months after enrolment. Differences between the cohorts were observed in clinical characteristics, including type of AF, stroke prevention strategies, and event rates. More patients in the retrospectively identified cohort received vitamin K antagonists (62.1% vs. 53.2%) and fewer received non-vitamin K oral anticoagulants (1.8% vs . 4.2%). All-cause mortality rates per 100 person-years during the prospective follow-up (starting the first study visit up to 1 year) were significantly lower in the retrospective than prospectively identified cohort (3.04 [95% CI 2.51 to 3.67] vs . 4.05 [95% CI 3.53 to 4.63]; p = 0.016). Conclusions: Interpretations of data from registries that aim to evaluate the characteristics and outcomes of patients with AF must take account of differences in registry design and the impact of recall bias and survivorship bias that is incurred with retrospective enrolment. Clinical Trial Registration: - URL: http://www.clinicaltrials.gov . Unique identifier for GARFIELD-AF (NCT01090362)

Improved risk stratification of patients with atrial fibrillation: an integrated GARFIELD-AF tool for the prediction of mortality, stroke and bleed in patients with and without anticoagulation.

OBJECTIVES: To provide an accurate, web-based tool for stratifying patients with atrial fibrillation to facilitate decisions on the potential benefits/risks of anticoagulation, based on mortality, stroke and bleeding risks. DESIGN: The new tool was developed, using stepwise regression, for all and then applied to lower risk patients. C-statistics were compared with CHA2DS2-VASc using 30-fold cross-validation to control for overfitting. External validation was undertaken in an independent dataset, Outcome Registry for Better Informed Treatment of Atrial Fibrillation (ORBIT-AF). PARTICIPANTS: Data from 39 898 patients enrolled in the prospective GARFIELD-AF registry provided the basis for deriving and validating an integrated risk tool to predict stroke risk, mortality and bleeding risk. RESULTS: The discriminatory value of the GARFIELD-AF risk model was superior to CHA2DS2-VASc for patients with or without anticoagulation. C-statistics (95% CI) for all-cause mortality, ischaemic stroke/systemic embolism and haemorrhagic stroke/major bleeding (treated patients) were: 0.77 (0.76 to 0.78), 0.69 (0.67 to 0.71) and 0.66 (0.62 to 0.69), respectively, for the GARFIELD-AF risk models, and 0.66 (0.64-0.67), 0.64 (0.61-0.66) and 0.64 (0.61-0.68), respectively, for CHA2DS2-VASc (or HAS-BLED for bleeding). In very low to low risk patients (CHA2DS2-VASc 0 or 1 (men) and 1 or 2 (women)), the CHA2DS2-VASc and HAS-BLED (for bleeding) scores offered weak discriminatory value for mortality, stroke/systemic embolism and major bleeding. C-statistics for the GARFIELD-AF risk tool were 0.69 (0.64 to 0.75), 0.65 (0.56 to 0.73) and 0.60 (0.47 to 0.73) for each end point, respectively, versus 0.50 (0.45 to 0.55), 0.59 (0.50 to 0.67) and 0.55 (0.53 to 0.56) for CHA2DS2-VASc (or HAS-BLED for bleeding). Upon validation in the ORBIT-AF population, C-statistics showed that the GARFIELD-AF risk tool was effective for predicting 1-year all-cause mortality using the full and simplified model for all-cause mortality: C-statistics 0.75 (0.73 to 0.77) and 0.75 (0.73 to 0.77), respectively, and for predicting for any stroke or systemic embolism over 1 year, C-statistics 0.68 (0.62 to 0.74). CONCLUSIONS: Performance of the GARFIELD-AF risk tool was superior to CHA2DS2-VASc in predicting stroke and mortality and superior to HAS-BLED for bleeding, overall and in lower risk patients. The GARFIELD-AF tool has the potential for incorporation in routine electronic systems, and for the first time, permits simultaneous evaluation of ischaemic stroke, mortality and bleeding risks. CLINICAL TRIAL REGISTRATION: URL: http://www.clinicaltrials.gov. Unique identifier for GARFIELD-AF (NCT01090362) and for ORBIT-AF (NCT01165710)

Two-year outcomes of patients with newly diagnosed atrial fibrillation: results from GARFIELD-AF.

AIMS: The relationship between outcomes and time after diagnosis for patients with non-valvular atrial fibrillation (NVAF) is poorly defined, especially beyond the first year. METHODS AND RESULTS: GARFIELD-AF is an ongoing, global observational study of adults with newly diagnosed NVAF. Two-year outcomes of 17 162 patients prospectively enrolled in GARFIELD-AF were analysed in light of baseline characteristics, risk profiles for stroke/systemic embolism (SE), and antithrombotic therapy. The mean (standard deviation) age was 69.8 (11.4) years, 43.8% were women, and the mean CHA2DS2-VASc score was 3.3 (1.6); 60.8% of patients were prescribed anticoagulant therapy with/without antiplatelet (AP) therapy, 27.4% AP monotherapy, and 11.8% no antithrombotic therapy. At 2-year follow-up, all-cause mortality, stroke/SE, and major bleeding had occurred at a rate (95% confidence interval) of 3.83 (3.62; 4.05), 1.25 (1.13; 1.38), and 0.70 (0.62; 0.81) per 100 person-years, respectively. Rates for all three major events were highest during the first 4 months. Congestive heart failure, acute coronary syndromes, sudden/unwitnessed death, malignancy, respiratory failure, and infection/sepsis accounted for 65% of all known causes of death and strokes for <10%. Anticoagulant treatment was associated with a 35% lower risk of death. CONCLUSION: The most frequent of the three major outcome measures was death, whose most common causes are not known to be significantly influenced by anticoagulation. This suggests that a more comprehensive approach to the management of NVAF may be needed to improve outcome. This could include, in addition to anticoagulation, interventions targeting modifiable, cause-specific risk factors for death. CLINICAL TRIAL REGISTRATION: http://www.clinicaltrials.gov. Unique identifier: NCT01090362