Regulating khat - Dilemmas and opportunities for the international drug control system

Background: The regulation of khat, one of the most recent psychoactive drugs to become a globally traded commodity, remains hotly contested within different producer and consumer countries. As regimes vary, it has been possible to compare khat policies in Africa, Europe and North America from different disciplinary perspectives. Methods: Field research was conducted in East Africa and Europe, using a combination of semistructured interviews, participant observation and the analysis of trade statistics. Results: The research established the significance of khat for rural producers, regional economies, as a tax base and source of foreign exchange. At the same time, khat as a psychoactive substance is associated with health and public safety problems that in turn are met with often ill-informed legislative responses. Bans have in turn lead to the criminalisation of users and sellers and illegal drug markets. Conclusion: The empirical work from Africa provides a strong argument for promoting evidence-based approaches to khat regulation, harnessing the positive aspects of the khat economy to develop a control model that incorporates the voices and respects the needs of rural producers. Ultimately, the framework for khat may provide both a model and an opportunity for revising the international treaties governing the control of other plant psychoactive-based substances

Reversed propagation dynamics of Laguerre-Gaussian beams in left-handed materials

On the basis of angular spectrum representation, the reversed propagation dynamics of Laguerre-Gaussian beam in left-handed materials (LHMs) is presented. We show that negative phase velocity gives rise to a reversed screw of wave-front, and ultimately leads to a reversed rotation of optical vortex. Furthermore, negative Gouy-phase shift causes an inverse spiral of Poynting vector. It is found that the Laguerre-Gaussian beam in LHMs will present the same propagation characteristics as the counterpart with opposite topological charges in regular right-handed materials (RHMs). The momentum conservation theorem insures that the tangential component of the wave momentum at the RHM-LHM boundary is conserved. It is shown that although the linear momentum reverses its direction, the angular momentum remains unchanged.Comment: 7 pages, 4 figure

Multilocus sequence and microsatellite identification of intra-specific hybrids and ancestor-like donors among natural Ethiopian isolates of Leishmania donovani.

Protozoan parasites of the genus Leishmania (Kinetoplastida: Trypanosomatidae) cause widespread and devastating human diseases. Visceral leishmaniasis is endemic in Ethiopia where it has also been responsible for fatal epidemics. It is postulated that genetic exchange in Leishmania has implications for heterosis (hybrid vigour), spread of virulent strains, resistance to chemotherapeutics, and exploitation of different hosts and vectors. Here we analyse 11 natural Ethiopian Leishmania donovani isolates consisting of four putative hybrids, seven parent-like isolates and over 90 derived biological clones. We apply a novel combination of high resolution multilocus microsatellite typing (five loci) and multilocus sequence typing (four loci) that together distinguish parent-like and hybrid L. donovani strains. Results indicate that the four isolates (and their associated biological clones) are genetic hybrids, not the results of mixed infections, each possessing heterozygous markers consistent with inheritance of divergent alleles from genetically distinct Ethiopian L. donovani lineages. The allelic profiles of the putative hybrids may have arisen from a single hybridisation event followed by inbreeding or gene conversion, or alternatively from two or more hybridisation events. Mitochondrial sequencing showed uniparental maxicircle inheritance for all of the hybrids, each possessing a single mitochondrial genotype. Fluorescence activated cell sorting analysis of DNA content demonstrated that all hybrids and their associated clones were diploid. Together the data imply that intra-specific genetic exchange is a recurrent feature of natural L. donovani populations, with substantial implications for the phyloepidemiology of Leishmania

Fluctuations, line tensions, and correlation times of nanoscale islands on surfaces

We analyze in detail the fluctuations and correlations of the (spatial) Fourier modes of nano-scale single-layer islands on (111) fcc crystal surfaces. We analytically show that the Fourier modes of the fluctuations couple due to the anisotropy of the crystal, changing the power spectrum of the fluctuations, and that the actual eigenmodes of the fluctuations are the appropriate linear combinations of the Fourier modes. Using kinetic Monte Carlo simulations with bond-counting parameters that best match realistic energy barriers for hopping rates, we deduce absolute line tensions as a function of azimuthal orientation from the analyses of the fluctuation of each individual mode. The autocorrelation functions of these modes give the scaling of the correlation times with wavelength, providing us with the rate-limiting kinetics driving the fluctuations, here step-edge diffusion. The results for the energetic parameters are in reasonable agreement with available experimental data for Pb(111) surfaces, and we compare the correlation times of island-edge fluctuations to relaxation times of quenched Pb crystallites.Comment: 11 pages, 8 figures; to appear in PRB 70, xxx (15 Dec 2004), changes in MC and its implication

Duality Cascade in Brane Inflation

We show that brane inflation is very sensitive to tiny sharp features in extra dimensions, including those in the potential and in the warp factor. This can show up as observational signatures in the power spectrum and/or non-Gaussianities of the cosmic microwave background radiation (CMBR). One general example of such sharp features is a succession of small steps in a warped throat, caused by Seiberg duality cascade using gauge/gravity duality. We study the cosmological observational consequences of these steps in brane inflation. Since the steps come in a series, the prediction of other steps and their properties can be tested by future data and analysis. It is also possible that the steps are too close to be resolved in the power spectrum, in which case they may show up only in the non-Gaussianity of the CMB temperature fluctuations and/or EE polarization. We study two cases. In the slow-roll scenario where steps appear in the inflaton potential, the sensitivity of brane inflation to the height and width of the steps is increased by several orders of magnitude comparing to that in previously studied large field models. In the IR DBI scenario where steps appear in the warp factor, we find that the glitches in the power spectrum caused by these sharp features are generally small or even unobservable, but associated distinctive non-Gaussianity can be large. Together with its large negative running of the power spectrum index, this scenario clearly illustrates how rich and different a brane inflationary scenario can be when compared to generic slow-roll inflation. Such distinctive stringy features may provide a powerful probe of superstring theory.Comment: Corrections in Eq.(5.47), Eq (5.48), Eq(5.49) and Fig

Optimal bispectrum constraints on single-field models of inflation

We use WMAP 9-year bispectrum data to constrain the free parameters of an 'effective field theory' describing fluctuations in single-field inflation. The Lagrangian of the theory contains a finite number of operators associated with unknown mass scales. Each operator produces a fixed bispectrum shape, which we decompose into partial waves in order to construct a likelihood function. Based on this likelihood we are able to constrain four linearly independent combinations of the mass scales. As an example of our framework we specialize our results to the case of 'Dirac-Born-Infeld' and 'ghost' inflation and obtain the posterior probability for each model, which in Bayesian schemes is a useful tool for model comparison. Our results suggest that DBI-like models with two or more free parameters are disfavoured by the data by comparison with single parameter models in the same class

Ecology of Feral Pigeons: Population Monitoring, Resource Selection, and Management Practices

Feral pigeons (Columba livia) are typically ignored by ornithologists but can be found roosting in the thousands within cities across the world. Pigeons have been known to spread zoonoses, through ectoparasites and excrement they produce. Along with disease, feral pigeons have an economic impact due to the cost of cleanup and maintenance of human infrastructure. Many organizations have tried to decrease pigeon abundances through euthanasia or use of chemicals that decrease reproductive output. However, killing pigeons has been unsuccessful in decreasing abundance, and chemical inhibition can be expensive and must be used throughout the year. A case study at Texas Tech University has found that populations fluctuate throughout the year, making it difficult to manage numbers. To successfully decrease populations, it is important to have a multifaceted approach that includes removing necessary resources (i. e. nest sites and roosting areas) and decreasing the number of offspring through humane techniques