32 research outputs found
On the alpha activity of natural tungsten isotopes
The indication for the alpha decay of 180-W with a half-life
T1/2=1.1+0.8-0.4(stat)+-0.3(syst)x10^18 yr has been observed for the first time
with the help of the super-low background 116-CdWO_4 crystal scintillators. In
conservative approach the lower limit on half-life of 180-W has been
established as T1/2>0.7x10^18 yr at 90% C.L. Besides, new T1/2 bounds were set
for alpha decay of 182-W, 183-W, 184-W and 186-W at the level of 10^20 yr.Comment: 16 pages, 8 figures, accepted in Phys. Rev.
Nuclear Half-Lives for Alpha Radioactivity of Elements with 100 Z 130
Theoretical estimates for the half lives of about 1700 isotopes of heavy
elements with Z from 100 to 130 are tabulated using theoretical Q-values. The
quantum mechanical tunneling probabilities are calculated within a WKB
framework using microscopic nuclear potentials. The microscopic nucleus-nucleus
potentials are obtained by folding the densities of interacting nuclei with a
density dependent M3Y (DDM3Y) effective nucleon-nucleon interaction. The
alpha-decay half lives calculated in this formalism using the experimental
Q-values were found to be in good agreement over a wide range of experimental
data spanning about twenty orders of magnitude. The theoretical Q-values used
for the present calculations are extracted from three different mass estimates
viz. Myers-Swiatecki [MS], Muntian-Hofmann-Patyk-Sobiczewski [M] and
Koura-Tachibana-Uno-Yamada [KUTY].Comment: 57 pages, 2 tables, 1 figur
Entanglement and localization of wavefunctions
We review recent works that relate entanglement of random vectors to their
localization properties. In particular, the linear entropy is related by a
simple expression to the inverse participation ratio, while next orders of the
entropy of entanglement contain information about e.g. the multifractal
exponents. Numerical simulations show that these results can account for the
entanglement present in wavefunctions of physical systems.Comment: 6 pages, 4 figures, to appear in the proceedings of the NATO Advanced
Research Workshop 'Recent Advances in Nonlinear Dynamics and Complex System
Physics', Tashkent, Uzbekistan, 200
The analysis of predictability of alpha-decay half-life formulae and the alpha partial half-lives of some exotic nuclei
The predictabilities of the three alpha-decay half-life formulae, the Royer
GLDM, the Viola-Seaborg and the Sobiczewski-Parkhomenko formulae, have been
evaluated by developing a method based on the ansatz of standard experimental
benchmarking. The coefficients of each formula were re-derived using the
reliable data of the alpha-standards nuclei. The modified formulae that
resulted were used to evaluate the accuracies of the formulae towards the
prediction of half-lives of a set of nuclides with well-studied alpha-
spectroscopic data as well as a set of exotic alpha-emitters. Further, a simple
linear optimization of the modified formulae allowed adjustments for the
insufficient statistics of the primary data set without changing the modified
formulae. While the three modified formulae showed equivalent results for all
the medium heavy nuclei except the odd-odd, the modified GLDM showed relatively
the best figures of merit for the odd-odd and superheavy nuclides.Comment: 16 pages, 4 tables, 2 figure
In Vivo MRI Based Prostate Cancer Identification with Random Forests and Auto-context Model
Modelo autologístico espaço-temporal com aplicação à análise de padrões espaciais da leprose-dos-citros Spatial temporal autologistic model with an application to the analysis of spatial patterns of citrus leprosis
O objetivo deste trabalho foi propor estratégias de modelagem aplicadas aos dados de incidência de leprose-dos-citros, por meio do uso de um modelo autologístico espaço-temporal. A adequação do modelo autologístico foi avaliada quanto à: análise de dados provenientes de avaliações feitas em diferentes momentos; detecção de padrões espaciais da doença, pela avaliação de diferentes estruturas de vizinhança; consideração do efeito defasado no tempo de covariáveis de vizinhança; e ao efeito do ácaro transmissor na probabilidade de nova infecção. O modelo autologístico espaço-temporal adotado estendeu o modelo logístico usual, em que a estrutura de vizinhança é descrita por meio da construção de covariáveis, a partir da resposta observada em plantas vizinhas à planta avaliada, na mesma avaliação, ou em avaliações anteriores. Os dados de incidência de leprose nas plantas de citros foram coletados em pontos referenciados no espaço, durante aproximadamente dois anos. Os modelos detectam o efeito da presença do vetor e os padrões espaciais na ocorrência de novas infecções, tanto para covariáveis de vizinhança da mesma avaliação, quanto para covariáveis de vizinhança da avaliação anterior. Além disso, os modelos considerados permitem quantificar as variações na probabilidade de ocorrência da doença de acordo com o estado da doença e com a incidência do ácaro transmissor.<br>The goal of this study was to propose modeling strategies applied to the analysis of citrus leprosis incidence, through the use of a spatial temporal autologistic model. We evaluated the adequacy of autologistic model to consider data collected at different times; to detect spatial-temporal patterns through different neighboring structures; to consider the effect of covariates from previous times; and assessing the effect of the presence of the disease vector in the probability of new infections occurrence. The spatial temporal autologistic model adopted has extended the usual logistic model, in which the neighboring structures is described by means of covariates built from the status of plants nearby, at the same or at previous times. Data regarding the presence of the leprosis on plants were collected at field points referenced in space, over a period of approximately two years. Models detect the presence of spatial patterns on new infections for the studied neighboring structures, at the same or previous time. Additionally, probability estimates of a plant become infected can be obtained from the fitted models, given the occurrence of the disease and vector