Deformed self-dual magnetic monopoles

We develop a deformation method for attaining new magnetic monopole analytical solutions consistent with generalized Yang-Mills-Higgs model introduced recently. The new solutions fulfill the usual radially symmetric ansatz and the boundary conditions suitable to assure finite energy configurations. We verify our prescription by studying some particular cases involving both exactly and partially analytical initial configurations whose deformation leads to new analytic BPS monopoles. The results show consistency among the models, the deformation procedure and the profile of the new solutions.Comment: 7 pages, 3 figure

A reaction-diffusion model for the growth of avascular tumor

A nutrient-limited model for avascular cancer growth including cell proliferation, motility and death is presented. The model qualitatively reproduces commonly observed morphologies for primary tumors, and the simulated patterns are characterized by its gyration radius, total number of cancer cells, and number of cells on tumor periphery. These very distinct morphological patterns follow Gompertz growth curves, but exhibit different scaling laws for their surfaces. Also, the simulated tumors incorporate a spatial structure composed of a central necrotic core, an inner rim of quiescent cells and a narrow outer shell of proliferating cells in agreement with biological data. Finally, our results indicate that the competition for nutrients among normal and cancer cells may be a determinant factor in generating papillary tumor morphology.Comment: 9 pages, 6 figures, to appear in PR

Spin-orbit interaction and the 'metal-insulator' transition observed in two-dimensional hole systems

We present calculations of the spin and phase relaxation rates in GaAs/AlGaAs $p$-type quantum wells. These rates are used to derive the temperature dependence of the weak-localization correction to the conductivity. In $p$-type quantum wells both weak localization and weak anti-localization are present due to the strong spin-orbit interaction. When determining the total conductivity correction one also have to include the term due to hole-hole interaction. The magnitude of the latter depends on the ratio between the thermal energy and the Fermi energy, $k_{\rm B}T/E_{\rm F}$ and whether the system can be considered as ballistic $(k_{\rm B}T \tau_{\rm tr} / \hbar>1)$ or diffusive ($k_{\rm B}T \tau_{\rm tr}/\hbar<1$). We argue that due to the relatively low Fermi energy and the moderate mobilities, in the $p$-type systems in question, the conductivity correction arising from hole-hole interactions is negligible at the highest temperatures accessible in the experiments. Hence the 'metal-insulator' transition observed at these relatively high temperatures could be caused by interference effects. We compare our calculations of the weak anti-localization correction with the experimental results from different independent groups with special emphasis on the experiments by Simmons et al. We find good agreement between predicted and observed transistion density $p_{c}$.Comment: 6 pages, 4 figures. Accepted to PRB (15 June, 2002

Geocronologia com 210Pb na avaliação das taxas de sedimentação e da dinâmica deposicional na Lagoa Itapeva, sul do Brasil

As a result of anthropogenic activities, coastal lakes are potentially threatened by increased sedimentation rates and relative sea-level increases. The present study analyzed the sedimentary-filling conditions of Itapeva Lake by using the 210Pb geochronology method, which is based on 210Pb and 226Ra activity values obtained from three sediment cores. Measurements of sedimentation rates in the core C3 indicate a strong influence of the drainage of the Três Forquilhas River with values of approximately 3.2 mm.a-1. The sampling points in the center (C2) and north (C1) exhibited significantly lower values of 2.4 and 2.9 mm.a-1, respectively. These values are lower than the rates of relative sea-level increase, which indicate a transitional scenario between the stabilization and sedimentary deficit in the lacustrine burial process. The particle size analysis in the core samples indicates the presence of significant hydrodynamic energy in the sedimentation. The silt fraction is the dominant class, with variations in size ranging from medium to coarse in all samples, followed by the occurrence of fraction sand in relation to clay which presented low concentration, not over 9%. However, an increase in mud content has been observed in the core C3 over the last several decades, which suggests changes in the drainage basin of the Três Forquilhas River due to an increase in sediment production. Urbanization and the introduction of agriculture within the last century are the main reasons for this behaviorLagoas costeiras são ambientes potencialmente ameaçados pelo aumento recente das taxas de sedimentação e elevação relativa do nível do mar. Neste trabalho foram analisadas as condições de preenchimento sedimentar da Lagoa Itapeva utilizando o método geocronológico 210Pb, a partir dos valores da atividade do 210Pb e 226Ra obtidos de três testemunhos geológicos. As taxas de sedimentação medidas no testemunho C3 indicam forte influência da drenagem do Rio Três Forquilhas, com valores na ordem de 3,2 mm.a-1. Os pontos de coleta no centro C2 e norte C1 apresentaram valores sensivelmente menores, 2,4 e 2,9 mm.a-1, respectivamente. Tais valores mostram-se inferiores as taxas de elevação relativa do nível do mar, indicando um cenário transicional entre a estabilização e o déficit sedimentar no processo de preenchimento lacustre. A análise granulométrica nos testemunhos indica a presença de significativa energia hidrodinâmica no processo de sedimentação. A fração silte é a classe dominante, com variação entre o tamanho médio a grosso em todas as amostras, seguida pela ocorrência da fração areia em relação à argila que apresentou baixa concentração, não ultrapassando 9%. Entretanto, foi verificado no testemunho C3 um aumento do teor de lamas nas últimas décadas, o que sugere modificações na bacia de drenagem do Rio Três Forquilhas pelo aumento na produção de sedimentos. A urbanização e a introdução da agricultura no último século são as principais variáveis que explicam este comportamento

Cultivo de Saccharomyces cerevisiae adaptada em D-xilulose sob condições aeróbias e anaeróbias

O desenvolvimento de um processo para produção de etanol com uma alta produtividade a partir de D-xilulose é de grande interesse econômico. Esse processo pode agregar maior valor aos resíduos lignocelulósicos, além de promover um aproveitamento completo da biomassa, utilizando-se suas frações celulósica e hemicelulósica para a obtenção de etanol. O objetivo do presente trabalho foi estudar a assimilação de D-xilulose, o crescimento e a produção de etanol e xilitol em cultivo de levedura de panificação de Saccharomyces cerevisiae em condições aeróbias e anaeróbis. Os experimentos foram conduzidos em biorreator de bancada de 2L, utilizando meio mínimo contendo a mistura xilose-xilulose. Os cultivos foram realizados com colônia de levedura previamente selecionada a partir de experimentos de screening com mais de 20 colônias de isoladas de levedura comercial que apresentaram crescimento em meio mínimo contendo a mistura xilose-xilulose em condições anaeróbias. A fermentação da D-xilulose pela levedura na ausência de oxigênio resultou na produção de 4,2 g/L de etanol e 3,7 de xilitol. Já o crescimento da levedura em condições aeróbias forneceu como produto principal a biomassa, com formação de 8 g/L e como subproduto o xilitol, com concentração máxima de 2,0 g/L

Insulator-Superfluid transition of spin-1 bosons in an optical lattice in magnetic field

We study the insulator-superfluid transition of spin-1 bosons in an optical lattice in a uniform magnetic field. Based on a mean-field approximation we obtained a zero-temperature phase diagram. We found that depending on the particle number the transition for bosons with antiferromagnetic interaction may occur into different superfluid phases with spins aligned along or opposite to the field direction. This is qualitatively different from the field-free transition for which the mean-field theory predicts a unique (polar) superfluid state for any particle number.Comment: 10 pages, 2 eps figure

Theoretical description of deformed proton emitters: nonadiabatic coupled-channel method

The newly developed nonadiabatic method based on the coupled-channel Schroedinger equation with Gamow states is used to study the phenomenon of proton radioactivity. The new method, adopting the weak coupling regime of the particle-plus-rotor model, allows for the inclusion of excitations in the daughter nucleus. This can lead to rather different predictions for lifetimes and branching ratios as compared to the standard adiabatic approximation corresponding to the strong coupling scheme. Calculations are performed for several experimentally seen, non-spherical nuclei beyond the proton dripline. By comparing theory and experiment, we are able to characterize the angular momentum content of the observed narrow resonance.Comment: 12 pages including 10 figure

Genome-wide linkage analysis of 972 bipolar pedigrees using single-nucleotide polymorphisms.

Because of the high costs associated with ascertainment of families, most linkage studies of Bipolar I disorder (BPI) have used relatively small samples. Moreover, the genetic information content reported in most studies has been less than 0.6. Although microsatellite markers spaced every 10 cM typically extract most of the genetic information content for larger multiplex families, they can be less informative for smaller pedigrees especially for affected sib pair kindreds. For these reasons we collaborated to pool family resources and carried out higher density genotyping. Approximately 1100 pedigrees of European ancestry were initially selected for study and were genotyped by the Center for Inherited Disease Research using the Illumina Linkage Panel 12 set of 6090 single-nucleotide polymorphisms. Of the ~1100 families, 972 were informative for further analyses, and mean information content was 0.86 after pruning for linkage disequilibrium. The 972 kindreds include 2284 cases of BPI disorder, 498 individuals with bipolar II disorder (BPII) and 702 subjects with recurrent major depression. Three affection status models (ASMs) were considered: ASM1 (BPI and schizoaffective disorder, BP cases (SABP) only), ASM2 (ASM1 cases plus BPII) and ASM3 (ASM2 cases plus recurrent major depression). Both parametric and non-parametric linkage methods were carried out. The strongest findings occurred at 6q21 (non-parametric pairs LOD 3.4 for rs1046943 at 119 cM) and 9q21 (non-parametric pairs logarithm of odds (LOD) 3.4 for rs722642 at 78 cM) using only BPI and schizoaffective (SA), BP cases. Both results met genome-wide significant criteria, although neither was significant after correction for multiple analyses. We also inspected parametric scores for the larger multiplex families to identify possible rare susceptibility loci. In this analysis, we observed 59 parametric LODs of 2 or greater, many of which are likely to be close to maximum possible scores. Although some linkage findings may be false positives, the results could help prioritize the search for rare variants using whole exome or genome sequencing