Bound electron nonlinearity beyond the ionization threshold

Although high field laser-induced ionization is a fundamental process underlying many applications, there have been no absolute measurements of the nonlinear polarizability of atoms and molecules in the presence of ionization. Such information is crucial, for example, for understanding the propagation of high intensity ultrashort pulses in matter. Here, we present absolute space- and time-resolved measurements of the ultrafast laser-driven nonlinear polarizability in argon, krypton, xenon, nitrogen, and oxygen up to an ionization fraction of a few percent. These measurements enable determination of the non-perturbative bound electron nonlinearity well beyond the ionization threshold, where it is found to be approximately linear in intensity

Subnational Taxes in Developing Countries: The Way Forward

Both theory and experience in a variety of circumstances around the world suggest strongly that if fiscal decentralization is to produce sustainable net benefits in developing countries, subnational governments require much more real taxing power than they now have. Students of public finance have studied the subject, and practitioners in developing countries have installed many different versions of subnational government tax. In most developing countries there are potentially sound and productive taxes that subnational governments could use: personal income tax surcharges, property taxes, taxes on the use of motor vehicles, payroll taxes, and even subnational value-added taxes and local ‘‘business value’’ taxes may all be viable options in particular countries. Still, there is no general consensus about what works and what does not. In this review paper, we try and pull together enough evidence to suggest the way forward. We also develop the argument that given political realities one cannot usually decentralize significant revenues to subnational governments without having in place an intergovernmental transfer system to offset at least some of the disequalizing effects that would otherwise occur. Nor does it make sense to think of decentralizing exactly the same package of tax choices to all subnational governments regardless of their scale and scope of operations

Decentralization and Infrastructure: Principles and Practice

This paper reviews the theoretical and practical issues surrounding the decentralization of responsibility for the provision of infrastructure to local governments in low income countries. The focus is on structural rather than management issues. There is plenty of evidence that following the theory can lead to efficient outcomes under decentralization, but also plenty of evidence that the theory and the practice often diverge widely. Seven policy rules that could support a successful decentralization of appropriate infrastructure services are drawn out of this review

Tax Policy in Developing Countries: Looking Back—and Forward

We review the changing nature of tax policy in developing countries over the last 30 years and consider what factors determining the level and structure of tax revenues in such countries may have changed recently and how such changes may affect future developments

Taxing Sugary Drinks

Countries everywhere are considering the increasing evidence on the possible health benefits from reducing the consumption of sugary drinks – often called sugar-sweetened beverages (SSB). This paper examines the rationale for taxing sugary drinks as a way to reduce sugar consumption and considers the experience to date. That excess consumption of sugar has serious adverse health consequences and that taxing sugar-sweetened beverages (SSB) may reduce the consumption of sugar are both largely supported by the evidence. What is less clear is whether SSB taxes can adequately address the problems arising from the excess consumption of sugar. If so, the question becomes how taxes might best be structured to do the job. The principal argument for a tax on SSB is to counter the harm that consumers may do to themselves by consuming too many sugary drinks. External costs are a much smaller part of the story. In any case, one may accept the basic public health case for discouraging the excess consumption of sugar without concluding that SSB taxes are the most effective and equitable way to achieve that objective. An excise tax on sugar-sweetened beverages is attractive because of its simplicity and its relatively low compliance and administrative costs. However, it covers less than half the consumption of added sugar, designing an appropriate tax is not an easy task, especially in the context of most developing countries, and the tax rate required to have a major impact on obesity may well higher than most countries are likely to accept. A better way to combat obesity might be a tax on sugar itself combined with such policies as more transparent labelling and measures that will encourage heathier lifestyles and diets

Typhoid and paratyphoid fever

Typhoid fever is estimated to have caused 21·6 million illnesses and 216 500 deaths globally in 2000, affecting all ages. There is also one case of paratyphoid fever for every four of typhoid. The global emergence of multidrug-resistant strains and of strains with reduced susceptibility to fluoroquinolones is of great concern. We discuss the occurrence of poor clinical response to fluoroquinolones despite disc sensitivity. Developments are being made in our understanding of the molecular pathogenesis, and genomic and proteomic studies reveal the possibility of new targets for diagnosis and treatment. Further, we review guidelines for use of diagnostic tests and for selection of antimicrobials in varying clinical situations. The importance of safe water, sanitation, and immunisation in the presence of increasing antibiotic resistance is paramount. Routine immunisation of school-age children with Vi or Ty21a vaccine is recommended for countries endemic for typhoid. Vi vaccine should be used for 2-5 year-old children in highly endemic settings