Spin waves and local magnetizations on the Penrose tiling

We consider a Heisenberg antiferromagnet on the Penrose tiling, a quasiperiodic system having an inhomogeneous Neel-ordered ground state. Spin wave energies and wavefunctions are studied in the linear spin wave approximation. A linear dispersion law is found at low energies, as in other bipartite antiferromagnets, with an effective spin wave velocity lower than in the square lattice. Spatial properties of eigenmodes are characterized in several different ways. At low energies, eigenstates are relatively extended, and show multifractal scaling. At higher energies, states are more localized, and, depending on the energy, confined to sites of a specified coordination number. The ground state energy of this antiferromagnet, and local staggered magnetizations are calculated. Perpendicular space projections are presented in order to show the underlying simplicity of this "complex" ground state. A simple analytical model, the two-tier Heisenberg star, is presented to explain the staggered magnetization distribution in this antiferromagnetic system.Comment: 14 pages, 21 figure

Dynamics of nanoscale droplets on moving surfaces

We use molecular dynamics (MD) simulations to investigate the dynamic wetting of nanoscale water droplets on moving surfaces. The density and hydrogen bonding profiles along the direction normal to the surface are reported, and the width of the water depletion layer is evaluated first for droplets on three different static surfaces: silicon, graphite, and a fictitious superhydrophobic surface. The advancing and receding contact angles, and contact angle hysteresis, are then measured as a function of capillary number on smooth moving silicon and graphite surfaces. Our results for the silicon surface show that molecular displacements at the contact line are influenced greatly by interactions with the solid surface and partly by viscous dissipation effects induced through the movement of the surface. For the graphite surface, however, both the advancing and receding contact angles values are close to the static contact angle value and are independent of the capillary number; i.e., viscous dissipation effects are negligible. This finding is in contrast with the wetting dynamics of macroscale water droplets, which show significant dependence on the capillary number

Simpósio de Geoarqueologia: temas abordados e resultados

Resumo: o Simpósio de Geoarqueologia da VI TAAS, coordenado por Rosiclér Theodoro da Silva e Michelle Mayumi Tizuka contou com a apresentação de nove trabalhos de pesquisadores do Brasil, Argentina e Colômbia. Este artigo trata de uma síntese dos temas abordados incluídos em: arqueologia e eventos climáticos, arqueologia e regiões costeiras, arqueologia da paisagem, arqueoestratigrafia, geoarqueologia de sistemas fluviais, arqueologia e vulcanismo. Seu objetivo principal é divulgar os resultados do simpósio e fortalecer a abordagem geoarqueológica nas pesquisas arqueológicas tanto em território nacional como no exterior. Palavras-chave: Geoarqueologia. Teoria Arqueológica. América do Sul

Arqueologia e história indígena no Pantanal

O artigo apresenta uma síntese dos dados arqueológicos sobre o Pantanal e o seu entorno, principalmente em Mato Grosso e Mato Grosso do Sul. Elaborado com base na noção de arqueologia como história indígena de longa duração, o artigo considera as trajetórias de estabelecimento e consolidação territorial da ocupação indígena regional, os processos de formação da configuração etnográfica encontrada pelos europeus e os impactos do colonialismo. O principal objetivo consiste em mostrar que a diversidade cultural característica do cenário etnográfico pantaneiro está associada à dinâmica histórica e cultural da ocupação indígena desde períodos anteriores à chegada dos conquistadores e colonizadores de origem europeia.The article presents an overview of the archaeological data on the Pantanal and its surrounding areas, mainly in Mato Grosso and Mato Grosso do Sul. Prepared based on the notion of archeology as long term indigenous history, the article considers the trajectories of territorial establishment and consolidation of the regional indigenous occupation, the formation processes of ethnographic setting found by Europeans and the impact of colonialism. The main objective is to show that cultural diversity characteristic of the Pantanal ethnographic scenario is associated with historical and cultural dynamics of indigenous occupation from periods prior to the arrival of the conquistadors and settlers of European origin

Pseudomamma On The Foot: An Unusual Presentation Of Supernumerary Breast Tissue

A 22-year-old woman sought medical care for a lesion in the plantar region of her left foot, a well-formed nipple surrounded by areola and hair. Microscopic examination of the dermis showed hair follicles, eccrine glands, and sebaceous glands. Fat tissue was noted at the base of the lesion. Clinical and histopathologic findings were consistent with the diagnosis of supernumerary breast tissue, also known as pseudomamma. To our knowledge, this is the first report of supernumerary breast tissue on the foot. © 2006 Dermatology Online Journal.124Dixon, J.M., Mansel, R.E., ABC of breast diseases. Congenital problems and aberrations of normal breast development and involution (1994) BMJ, 309, pp. 797-800Grossl, N.A., Supernumerary breast tissue: Historical perspectives and clinical features (2000) South Med J, 93, pp. 29-32Bhatnagar, K.P., Ramsaroop, L., Bhatnagar, K.P., Satyapal, K.S., Singh, B., Dorsal scapular breast in a woman (2003) Plast Reconstr Surg, 112, pp. 571-574Schewach-Millet, M., Fisher, B.K., Supernumerary nipple on the shoulder (1976) Cutis, 17, pp. 384-385Koltuksuz, U., Aydin, E., Supernumerary breast tissue: A case of pseudomamma on the face (1997) J Pediatr Surg, 32, pp. 1377-1378Boivin, S., Segard, M., Delaporte, E., Cotten, H., Piette, F., Thomas, P., Complete supernumerary breast on the thigh in a male patient (2001) Ann Dermatol Venereol, 128, pp. 144-146Shin, S., Sheikh, S., Allenby, A., Rosen, P., Invasive secretory (juvenile) carcinoma arising in ectopic breast tissue of the axilla (2001) Arch Pathol Lab Med, 125, pp. 1372-1374Gendler, L.S., Joseph, K.A., Breast cancer of an accessory nipple (2005) N Engl J Med, 353, p. 1835Conde, D.M., Torresan, R.Z., Kashimoto, E., Carvalho, L.E.C., Cardo Filho, C., Fibroadenoma in axillary supernumerary breast: Case report (2005) Sao Paulo Med J, 123, pp. 253-255Kajava, Y., The proportions of supernumerary nipples in the Finnish population (1915) Duodecim, 1, pp. 143-170Newman, M., Supernumerary nipples (1988) Am Fam Physician, 38, pp. 183-188Pellegrini, J.R., Wagner Jr., R.F., Polythelia and associated conditions (1983) Am Fam Physician, 28, pp. 129-132Urbani, C.E., Betti, R., Accessory mammary tissue associated with congenital and hereditary nephrourinary malformations (1996) Int J Dermatol, 35, pp. 349-352Brown, J., Schwartz, R.A., Supernumerary nipples and renal malformations: A family study (2004) J Cutan Med Surg, 8, pp. 170-172Grotto, I., Browner-Elhanan, K., Mimouni, D., Varsano, I., Cohen, H.A., Mimouni, M., Occurrence of supernumerary nipples in children with kidney and urinary tract malformations (2001) Pediatr Dermatol, 18, pp. 291-294Cohen, P.R., Kurzrock, R., Miscellaneous genodermatoses: Beckwith-Wiedemann syndrome, Birt-Hogg-Dube syndrome, familial atypical multiple mole melanoma syndrome, hereditary tylosis, incontinentia pigmenti, and supernumerary nipples (1995) Dermatol Clin, 13, pp. 211-229Aslan, D., Gursel, T., Kaya, Z., Supernumerary nipples in children with hematologic disorders (2004) Pediatr Hematol Oncol, 21, pp. 461-46

Modification of deeply buried hydrophobic interfaces by ionic surfactants

Hydrophobicity, the spontaneous segregation of oil and water, can be modified by surfactants. The way this modification occurs is studied at the oil–water interface for a range of alkanes and two ionic surfactants. A liquid interfacial monolayer, consisting of a mixture of alkane molecules and surfactant tails, is found. Upon cooling, it freezes at Ts, well above the alkane’s bulk freezing temperature, Tb. The monolayer’s phase diagram, derived by surface tensiometry, is accounted for by a mixtures-based theory. The monolayer’s structure is measured by high-energy X-ray reflectivity above and below Ts. A solid–solid transition in the frozen monolayer, occurring approximately 3 °C below Ts, is discovered and tentatively suggested to be a rotator-to-crystal transition