Constrained Triangulations, Volumes of Polytopes, and Unit Equations

Given a polytope P in R^d and a subset U of its vertices, is there a triangulation of P using d-simplices that all contain U? We answer this question by proving an equivalent and easy-to-check combinatorial criterion for the facets of P. Our proof relates triangulations of P to triangulations of its "shadow", a projection to a lower-dimensional space determined by U. In particular, we obtain a formula relating the volume of P with the volume of its shadow. This leads to an exact formula for the volume of a polytope arising in the theory of unit equations

The Dynamics of Male and Female Street Prostitution in Manchester, England

This article examines male street prostitution in Manchester, England, and draws some comparisons to its female counterpart in this city. While the two sectors have some important similarities, we also find significant differences in the physical and social ecology of the places in which they work, in their behavior patterns, and in individuals’ demographics and work experiences. We find that ecological differences between the male and female markets have a major impact on participants’ work practices, opportunities, and integration into the local community. The data also indicate that it is incorrect to speak of a monolithic male street market or sector in Manchester because sellers shift between settings (street, bar, and escorting), unlike the female street sector. We also find that the males demonstrate more diversity in their repertoires for earning money. The findings have implications for local government policy and for outreach workers who work with these populations. </jats:p

Magnetic impurity resonance states and symmetry of the superconducting order parameter in iron-based superconductors

We investigate the effect of magnetic impurities on the local quasiparticle density of states (LDOS) in iron-based superconductors. Employing the two-orbital model where 3$d$ electron and hole conduction bands are hybridizing with the localized $f$-orbital of the impurity spin, we investigate how various symmetries of the superconducting gap and its nodal structure influence the quasiparticle excitations and impurity bound states. We show that the bound states behave qualitatively different for each symmetry. Most importantly we find that the impurity-induced bound states can be used to identify the nodal structure of the extended s-wave symmetry ($S^{\pm}$) that is actively discussed in ferropnictides.Comment: 7 pages, 5 figures, theory part is extended, figures are replace

Determination of the crystal structure of CuSnTi by full profile Rietveld analysis

The crystal structure of the new ternary phase CuSnTi is determined by full profile Rietveld analysis of the powder diffractogram. 104 reflections were refined to a final RBragg value of 5.60%. CuSnTi crystallizes with the spacegroup P63/mmc and is isostructural to InNi2. The lattice parameters are a=0.439 555(5) nm and c=0.601 505(9) n

Why prostitution policy (usually) fails and what to do about it?

This article describes and discusses the results of two comparative studies of prostitution policy in Europe that are complementary in their design and methodology. One is a comparison of 21 countries using a most different systems design; the other an in-depth comparison of Austria and The Netherlands, using a most similar systems design. The two studies found a remarkable continuity in the inherent approach to the regulation of prostitution and its effects. Despite differences in political regime, administrative organization, and national cultures, since the middle of the 19th century, the purpose of prostitution policy has been to impose strict controls on sex workers and to a lesser extent their work sites. The effects of this approach have been disappointing: despite rhetorical claims to the contrary the control of sex workers has no discernable effect on the prevalence of prostitution in society. The effects of policies aimed at control are mostly negative in that they corrode the human and labor rights of sex workers. The article discusses several challenges to the regulation of prostitution (such as its deeply moral nature and the lack of precise and reliable data) as well a number of other important outcomes (such as the importance of local policy implementation for the effects of regulation). The article concludes with the empirically substantiated suggestion that a form of collaborative governance in which sex worker advocacy organizations participate in the design and implementation of prostitution policy offers real prospects for an effective and humane prostitution policy

The effect of sex work regulation on health and well-being of sex workers: Evidence from Senegal.

Senegal is the only African country where sex work is legal and regulated by a health policy. Senegalese female sex workers (FSWs) are required to register with a health facility and to attend monthly routine health checks aimed at testing and treating sexually transmitted infections (STIs). Compliance to those routine visits is recorded on a registration card that must be carried by FSWs in order to avoid sanctions in case of police arrests. Although this policy was first introduced in 1969 to limit the spread of STIs, there is no evidence so far of its impact on FSWs' health and well-being. The paper aims to fill this gap by exploiting a unique data set of registered and unregistered Senegalese FSWs. Using propensity score matching, we find that registration has a positive effect on FSWs' health. However, we find that registration reduces FSWs' subjective well-being. This finding is explained by the fact that registered FSWs are found to engage in more sex acts, in riskier sex acts, have less social support from their peers, and are more likely to experience violence from clients and police officers. We prove that those results are robust to the violation of the conditional independence assumption, to misspecification of the propensity score model, and that covariate balance is achieved. The results suggest that more efforts should be deployed to reduce the stigma associated with registration and to address the poor well-being of FSWs, which is counterproductive to HIV prevention efforts