The United States and the Gulf States: Uncertain Partners in a Changing Region

Evaluates the relationship between the United States and the Gulf states as they face democratic transitions in the Arab world as well as security challenges in the Gulf

The Methodology of Positive Policy Analysis

Policy analyses frequently clash. Their disagreements stem from many sources, such as models, empirical estimates, values, who should have standing, and weighting of different criteria. We provide a simple taxonomy of disagreement, identifying distinct categories within both the positive and value domains. Using disagreements in climate policy to illustrate, we demonstrate how illuminating the structure of disagreement can help to clarify the way forward. We conclude by suggesting a structure for new policy analysis that can facilitate assessment, comparison, and debate by making clear the likely sources of disagreement

La librairie Marcel Rivière, entre science, économie et politique

Les textes socialistes ont une histoire. Cette assertion, pour évidente qu'elle puisse paraître, engage un certain nombre de choix et de précautions méthodologiques. Elle implique tout d'abord une rupture franche avec une tradition scientifique encore vivace qui tend à réduire l'histoire politique soit à l'histoire des élections, des institutions ou des grands hommes soit encore à une histoire des idées et courants politiques, conçus comme des significations intemporelles, des formes pures ap..

Occurrence and environmental distribution of 5 UV filters during the 1 summer season in different water bodies

International audienceOrganic UV filters are used worldwide in various personal care products as well as textiles, paints, plastic, food and adhesives. They are main ingredients in sunscreen lotions that are used heavily by beachgoers in the summer season. There is thus an increasing concern regarding the fate of organic UV filters in the environment and their impact on living organisms. Many of the UV filters in use are hydrophobic and are expected to accumulate in the sediment phase in aquatic systems, but this has yet to be validated in situ. We targeted the UV filters benzophenone 3 (BP3), butyl Methoxydibenzoylmethane (BMDBM), diethylhexyl butamido triazone (DBT), bis-ethylhexyloxyphenol methoxyphenyl triazine (BEMT) and methylene bis-benzotriazolyl tetramethylbutylphenol (MBBT) in a freshwater lake and in a coastal bay in order to understand their distribution during summer 2016. Further, we examined their environmental partitioning by collecting samples from the surface water, the sediment phase and water surface microlayer (SML). We show for the first time the presence of DBT, BEMT and MBBT in environmental matrices (water, SML, and sediment). Notably, these UV filters were detected at low amounts in surface waters with maximum concentrations of 9.9 ng/L for DBT, 18.4 ng/L for BEMT and below detection limits for MBBT, and somewhat higher concentrations in the SML, with maximum concentrations of 43.3 ng/L for DBT, 5625.4 ng/L for BEMT and 45.6 ng/L for MBBT. These filters were detected at even greater concentrations in the sediments, with maximum concentrations of 652.6 ng/g for DBT, 115.0 ng/g for BEMT and 75.2 ng/g for MBBT (dry weight sediment). We also performed controlled laboratory experiments to determine their partitioning behavior and we verified the actual solubility of many of the filters. This will help in determining the environmental fate and finally lead to a better risk assessment of these compounds. Together, these results corroborate the hypothesis that hydrophobic UV filters accumulate in the sediment phase and highlight the importance of discerning whether these UV filters impact the benthic community and their potential for bioaccumulation

A momentum trading strategy based on the low frequency component of the exchange rate

Authors' draft published as working paper; version August 2008. Final version published in Journal of Banking & Finance. Available online at http://www.sciencedirect.com/In this paper, we develop a momentum trading strategy based on the low frequency trend component of the spot exchange rate. Using kernel regression and the high-pass filter of Hodrick and Prescott [Hodrick, R., Prescott, E., 1997. Post-war US business cycles: An empirical investigation. Journal of Money, Credit and Banking 29, 1-16], we recover the non-linear trend in the monthly exchange rate and use short-term momentum in this to generate buy and sell signals. The low frequency momentum trading strategy offers greater directional accuracy, higher returns and Sharpe ratios, lower maximum drawdown and less frequent trading than traditional moving average rules. Moreover, unlike traditional moving average rules, the performance of the low frequency momentum trading strategy is relatively robust across different time periods. The low frequency momentum trading strategy is also robust to the choice of smoothing parameter (in the case of the HP filter) and the distribution and bandwidth parameter (in the case of kernel regression) over a wide range of values. (C) 2009 Elsevier B.V. All rights reserved

What causes the inverse relationship between primary production and export efficiency in the Southern Ocean?

The ocean contributes to regulating atmospheric CO2 levels, partly via variability in the fraction of primary production (PP) which is exported out of the surface layer (i.e. the e-ratio). Southern Ocean studies have found that, contrary to global scale analyses, an inverse relationship exists between e-ratio and PP. This relationship remains unexplained, with potential hypotheses being i) large export of dissolved organic carbon (DOC) in high PP areas, ii) strong surface microbial recycling in high PP regions and/ or iii) grazing mediated export varies inversely with PP. We find that the export of DOC has a limited influence in setting the negative e-ratio/PP relationship. However, we observed that at sites with low PP and high e-ratios, zooplankton mediated export is large and surface microbial abundance low suggesting that both are important drivers of the magnitude of the e-ratio in the Southern Ocean

Application of an acoustofluidic perfusion bioreactor for cartilage tissue engineering

Cartilage grafts generated using conventional static tissue engineering strategies are characterised by low cell viability, suboptimal hyaline cartilage formation and, critically, inferior mechanical competency, which limit their application for resurfacing articular cartilage defects. To address the limitations of conventional static cartilage bioengineering strategies and generate robust, scaffold-free neocartilage grafts of human articular chondrocytes, the present study utilised custom-built microfluidic perfusion bioreactors with integrated ultrasound standing wave traps. The system employed sweeping acoustic drive frequencies over the range of 890 to 910 kHz and continuous perfusion of the chondrogenic culture medium at a low-shear flow rate to promote the generation of three-dimensional agglomerates of human articular chondrocytes, and enhance cartilage formation by cells of the agglomerates via improved mechanical stimulation and mass transfer rates. Histological examination and assessment of micromechanical properties using indentation-type atomic force microscopy confirmed that the neocartilage grafts were analogous to native hyaline cartilage. Furthermore, in the ex vivo organ culture partial thickness cartilage defect model, implantation of the neocartilage grafts into defects for 16 weeks resulted in the formation of hyaline cartilage-like repair tissue that adhered to the host cartilage and contributed to significant improvements to the tissue architecture within the defects, compared to the empty defects. The study has demonstrated the first successful application of the acoustofluidic perfusion bioreactors to bioengineer scaffold-free neocartilage grafts of human articular chondrocytes that have the potential for subsequent use in second generation autologous chondrocyte implantation procedures for the repair of partial thickness cartilage defects

Investigation of HIV Incidence Rates in a High-Risk, High-Prevalence Kenyan Population: Potential Lessons for Intervention Trials and Programmatic Strategies

Abstract Cost-effective HIV prevention programs should target persons at high risk of HIV acquisition. We conducted an observational HIV incidence cohort study in Kisumu, Kenya, where HIV prevalence is triple that of the national rate. We used referral and venue-sampling approaches to enroll HIV-negative persons for a 12-month observational cohort, August 2010 to September 2011, collected data using computer-assisted interviews, and performed HIV testing quarterly. Among 1292 eligible persons, 648 (50%) were excluded for HIV positivity and other reasons. Of the 644 enrollees, 52% were women who were significantly older than men (P < .01). In all, 7 persons seroconverted (incidence rate [IR] per 100 person-years ¼ 1.11; 95% confidence interval [CI] 0.45-2.30), 6 were women; 5 (IR ¼ 3.14; 95% CI 1.02-7.34) of whom were 25 years. Most new infections occurred in young women, an observation consistent with other findings in sub-Saharan Africa that women aged 25 years are an important population for HIV intervention trials in Africa

The Future of Agent-Based Modeling

In this paper, I elaborate on the role of agent-based (AB) modeling for macroeconomic research. My main tenet is that the full potential of the AB approach has not been realized yet. This potential lies in the modular nature of the models, which is bought by abandoning the straitjacket of rational expectations and embracing an evolutionary perspective. I envisage the foundation of a Modular Macroeconomic Science, where new models with heterogeneous interacting agents, endowed with partial information and limited computational ability, can be created by recombining and extending existing models in a unified computational framework