SummaryTungiasis is caused by the¯ea Tunga penetrans. Growing urbanization, improved housing and use of appropriate footwear presumably have led to an overall reduction of the occurrence of this ectoparasitosis within the last decades. However, it is still highly prevalent where people live in extreme poverty, occurring in many Latin American and African countries. Although the infection has long been known, data on the ectoparasite's biology and the epidemiology of the disease are scant. Methods for treatment, prevention and control have never been evaluated in a scienti®c manner. Tungiasis remains an important public health problem for the very poor, a problem neglected by those who are affected, by the medical profession and by the scienti®c community.

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We show how the squeezed vacuum fields generated in collective fluorescence within a highfinesse cavity can be transformed into squeezed coherent states with high brightness but with the same degree of noise suppression. The transformation is achieved by an injected signal that creates a mean polarization and squeezing in the high rather than the low branch of the optical bistable collective radiation. Analytical expressions are obtained for the limit of weak excitation of the atomic media. Comparisons with results obtained using rigged-reservoir theories and also from a multistage attenuator are made. The limitations of the model are discussed.

We present a theoretical study of the second-harmonic generation from pairs of two-level atoms in solids. The density-matrix formalism is used to obtain the nonlinear polarization governing the process. The second-harmonic polarization depends on the laser frequency, the interaction potential between the atoms, and the laser intensity. The signal line shape may exhibit power broadening and shift of resonances.

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