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Phylogenetic inference based on language is a vital tool for tracing the dynamics of human population expansions. The timescale of agriculture-based expansions around the world provides an informative amount of linguistic change ideal for reconstructing phylogeographies. Here we investigate the expansion of Arawak, one of the most widely dispersed language families in the Americas, scattered from the Antilles to Argentina. It has been suggested that Northwest Amazonia is the Arawak homeland based on the large number of diverse languages in the region. We generate language trees by coding cognates of basic vocabulary words for 60 Arawak languages and dialects to estimate the phylogenetic relationships among Arawak societies, while simultaneously implementing a relaxed random walk model to infer phylogeographic history. Estimates of the Arawak homeland exclude Northwest Amazonia and are bi-modal, with one potential homeland on the Atlantic seaboard and another more likely origin in Western Amazonia. Bayesian phylogeography better supports a Western Amazonian origin, and consequent dispersal to the Caribbean and across the lowlands. Importantly, the Arawak expansion carried with it not only language but also a number of cultural traits that contrast Arawak societies with other lowland cultures.

nent in the electronic wave function outside a solid surface. This feature is unique to INS among the electron spectroscopies used to determine surface electronic structure.Because the effective neutralization energy of the ion is ~ 2 eV less than the free-space value, 5 we can estimate the distance s m where neutralization occurs. Equating &E n = 2 eV to the principal interaction term, namely the image interaction (3.6 eV A)/s m , we obtain s m~ 1.8 A as the distance of the ion from the image plane. This simple image interaction has been shown to hold with good accuracy to 1.5 A. 11 From the equation s m =(l/a)ln(A/av) given earlier we obtain As m = (l/a)\n(v 2 /v^) as the difference in neutralization distances for ions of velocities v Y and v 2 . The parameter a that specifies the rate of exponential falloff of R t (s) is taken as 2X, where exp(-As) is the rate of decay outside the surface of a p wave function at E -£ vac ~ -7 eV, the principal determinant of where neutralization occurs. From A = (2mE i /n 2 ) 1/2 with E^l eV we obtain a =2.8 A" 1 . This estimate agrees closely with the variation of charge density outside the Si surface calculated by Appelbaum and Hamann. 12 Adding the 2-eV image acceleration to the experimental ion energies we obtain ^2/^t = (f|) 1/2 = l 0 35 and s m~ (1/2.8) xln(1.35)~0.1 A. Hence the relative change in the Hg d orbital components that we see in the U(E) functions of Fig. 2 occurs over a distance increment of ~0.1 A at an ion-surface separation of ~2 A.The observed changes in the Hg d orbital intensity have only relative significance. The absolute magnitude cannot be determined because we do not know a priori either the electron escape probability function or the factor R 2 used in the Strontium titanate and potassium tantalate are incipient ferroelectrics. Their static dielectric constant follows a Curie-Weiss law down to about one-curve method.We conclude that ion-neutralization spectroscopy using our new one-curve debroadening procedure yields information about the relative variation of wave-function components outside a surface, We believe this to be a significant addition to the capabilities of electron spectroscopies because we expect it to help us understand the intensity differences of orbital resonances in chemisorption systems as observed by INS and UPS. This, in turn, should yield information about the wave-function character of particular orbital resonances.We acknowledge with thanks helpful discussions with J. A. Appelbaum and J. E. Rowe, as well as the technical assistance of Philip Petrie. 1 H. D. Hagstrum, Phys. Rev. 150, 495 (1966). 2 J. A. Appelbaum and D. R. Hamann, Phys. Rev. B 12, 5590 (1975).The low-temperature anomaly in the lattice dynamics of SrTi0 3 and KTa0 3 is described as resulting from an anharmonic coupling between an optical and an acoustic branch. The numerical calculations performed for oo TO at the center of the Brillouin zone give an excellent fit to the available data from 4 to 300 K. It is shown that the ferroelectric phase transition i...

Este artigo apresenta um método quantitativo binário para a comparação histórica de línguas, baseado em uma análise léxico- statística. O método mostra uma solução viável para os problemas  ue foram encontrados em trabalhos de características semelhantes realizados previamente. Como aplicação ilustrativa do método, realizou-se uma análise comparativa de línguas das famílias Pano e Tacana, considerando listas de palavras definidas como Proto- ormas. A aplicação do método resultou num fortalecimento da hipótese de relacionamento genético entre as ínguas dessas duas  amílias.

The energy spectrum of the XY model in a transverse field is studied by the spectral density method (SDM), using polar and Gaussian "ansatze". Expressions for the critical temperature and critical transverse field are obtained. It is shown that, within some approximations, the static properties of this model are not modified by including damping effects in the elementary excitations.Unter Benutzung von polaren und Gad-,,AnsatZen" wird das Energiespektrum des XY-Modells in einem transversalen Feld mittels der Spektraldichtemethode (SDM) untersucht. Ausdriicke fur die kritische Temperatur und das kritische transversale Feld werden erhalten. Es wird gezeigt, daB, im Rahmen einiger Naherungen, die statischen Eigenschaften dieses Modells durch EinschluB von Dampfungseinfliissen in den Elementaranregungen ni?ht modifiziort werden.