903 research outputs found
Different formulations of 3He and 3H photodisintegration
Different momentum space Faddeev-like equations and their solutions for the
radiative pd-capture and the three-nucleon photodisintegration of 3He are
presented. Applications are based on the AV18 nucleon-nucleon and the Urbana IX
three nucleon forces. Meson exchange currents are included using the Siegert
theorem. A very good agreement has been found in all cases indicating the
reliability of the used numerical methods. Predictions for cross sections and
polarization observables in the pd-capture and the complete three nucleon
breakup of 3He at different incoming deuteron/photon energies are presented.Comment: 18 pages, 9 ps figure
Eccrine porocarcinoma of the head: An important differential diagnosis in the elderly patient
Background: Eccrine porocarcinoma is a rare malignant tumor of the sweat gland, characterized by a broad spectrum of clinicopathologic presentations. Surprisingly, unlike its benign counterpart eccrine poroma, eccrine porocarcinoma is seldom found in areas with a high density of eccrine sweat glands, like the palms or soles. Instead, eccrine porocarcinoma frequently occurs on the lower extremities, trunk and abdomen, but also on the head, resembling various other skin tumors, as illustrated in the patients described herein. Observations: We report 5 cases of eccrine porocarcinoma of the head. All patients were initially diagnosed as having epidermal or melanocytic skin tumors. Only after histopathologic examination were they classified as eccrine porocarcinoma, showing features of epithelial tumors with abortive ductal differentiation. Characteristic clinical, histopathologic and immunohistochemical findings of eccrine porocarcinomas are illustrated. Conclusion: Eccrine porocarcinomas are potentially fatal adnexal malignancies, in which extensive metastatic dissemination may occur. Porocarcinomas are commonly overlooked, or misinterpreted as squamous or basal cell carcinomas as well as other common malignant and even benign skin tumors. Knowledge of the clinical pattern and histologic findings, therefore, is crucial for an early therapeutic intervention, which can reduce the risk of tumor recurrence and serious complications. Copyright (c) 2008 S. Karger AG, Basel
Three-Nucleon Electroweak Capture Reactions
Recent advances in the study of the p-d radiative and mu-3he weak capture
processes are presented and discussed. The three-nucleon bound and scattering
states are obtained using the correlated-hyperspherical-harmonics method, with
realistic Hamiltonians consisting of the Argonne v14 or Argonne v18 two-nucleon
and Tucson-Melbourne or Urbana IX three-nucleon interactions. The
electromagnetic and weak transition operators include one- and two-body
contributions. The theoretical accuracy achieved in these calculations allows
for interesting comparisons with experimental data.Comment: 12 pages, 4 figures, invited talk at the CFIF Fall Workshop: Nuclear
Dynamics, from Quarks to Nuclei, Lisbon, 31st of October - 1st of November
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The Impact of Stratospheric Ozone Recovery on Tropopause Height Trends
The evolution of the tropopause in the past, present, and future climate is examined by analyzing a set of long-term integrations with stratosphere-resolving chemistry climate models (CCMs). These CCMs have high vertical resolution near the tropopause, a model top located in the mesosphere or above, and, most important, fully interactive stratospheric chemistry. Using such CCM integrations, it is found that the tropopause pressure (height) will continue to decrease (increase) in the future, but with a trend weaker than that in the recent past. The reduction in the future tropopause trend is shown to be directly associated with stratospheric ozone recovery. A significant ozone recovery occurs in the Southern Hemisphere lower stratosphere of the CCMs, and this leads to a relative warming there that reduces the tropopause trend in the twenty-first century.
The future tropopause trends predicted by the CCMs are considerably smaller than those predicted by the Intergovernmental Panel on Climate Change Fourth Assessment Report (AR4) models, especially in the southern high latitudes. This difference persists even when the CCMs are compared with the subset of the AR4 model integrations for which stratospheric ozone recovery was prescribed. These results suggest that a realistic representation of the stratospheric processes might be important for a reliable estimate of tropopause trends. The implications of these finding for the Southern Hemisphere climate change are also discussed
The role of the chemical composition of monetite on the synthesis and properties of α-tricalcium phosphate
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