On the energy-shell contributions of the three-particle~-~ three-hole excitations

The response functions for the extended second and third random phase approximation are compared. A second order perturbation calculation shows that the first-order amplitude for the direct $3p3h$ excitation from the ground state cancels with those that are engendered by the $1p1h$-$3p3h$ coupling. As a consequence nonvanishing $3p3h$ effects to the $1p1h$ response involve off energy shell renormalization only. On shell $3p3h$ processes are absent.Comment: 12 pages text (LaTex) and 1 figure included, to be published in Phys. Rev.

Dynamical model for Pion - Nucleon Bremsstrahlung

A dynamical model based on effective Lagrangians is proposed to describe the bremsstrahlung reaction $\pi N \to \pi N \gamma$ at low energies. The $\Delta(1232)$ degrees of freedom are incorporated in a way consistent with both, electromagnetic gauge invariance and invariance under contact transformations. The model also includes the initial and final state rescattering of hadrons via a T-matrix with off-shell effects. The $\pi N \gamma$ differential cross sections are calculated using three different T-matrix models and the results are compared with the soft photon approximation, and with experimental data. The aim of this analysis is to test the off-shell behavior of the different T-matrices under consideration.Comment: 16 pages, latex, 6 eps figures. Accepted for publication in Physical Review

Linear models of activation cascades: analytical solutions and coarse-graining of delayed signal transduction

Cellular signal transduction usually involves activation cascades, the sequential activation of a series of proteins following the reception of an input signal. Here we study the classic model of weakly activated cascades and obtain analytical solutions for a variety of inputs. We show that in the special but important case of optimal-gain cascades (i.e., when the deactivation rates are identical) the downstream output of the cascade can be represented exactly as a lumped nonlinear module containing an incomplete gamma function with real parameters that depend on the rates and length of the cascade, as well as parameters of the input signal. The expressions obtained can be applied to the non-identical case when the deactivation rates are random to capture the variability in the cascade outputs. We also show that cascades can be rearranged so that blocks with similar rates can be lumped and represented through our nonlinear modules. Our results can be used both to represent cascades in computational models of differential equations and to fit data efficiently, by reducing the number of equations and parameters involved. In particular, the length of the cascade appears as a real-valued parameter and can thus be fitted in the same manner as Hill coefficients. Finally, we show how the obtained nonlinear modules can be used instead of delay differential equations to model delays in signal transduction.Comment: 18 pages, 7 figure

Resistência de genótipos de melancia à mancha aquosa.

O objetivo da pesquisa foi avaliar o nível de resistência de genótipos de melancia pertencentes ao Banco Ativo de Germoplasma de Cucurbitáceas para o Nordeste Brasileiro (BAG) da Embrapa Semiárido, em diferentes estádios de desenvolvimento da planta: sementes (74 genótipos), plântulas e plantas antes da floração (29 genótipos) e plantas durante a floração e frutificação (7 genótipos).Suplemento. Resumo 296. Edição do 45 Congresso Brasileiro de Fitopatologia, 2012, Manaus

First Cytogenetic Study Through Conventional Staining of The Ant Genus Blepharidatta Wheeler, 1915 (Hymenoptera: Formicidae: Attini)

Blepharidatta is a rare Neotropical ant genus in the Attini tribe of the subfamily Myrmicinae. It has only four valid species and among them Blepharidatta delabiei was recently described and there is little knowledge on its biology. This study is the first cytogenetic characterization for the genus Blepharidatta and also presents the biology of B. delabiei. Cytogenetic analyses revealed a karyotype 2n = 28 with acrocentric and metacentric chromosomes and a karyotypic formula (m: metacentric, a: acrocentric): 2K = 16m + 12a. We observed that ants of this species have diurnal habits with higher foraging activity in the afternoon and are possibly omnivorous as they accepted the baits used. The distance between colonies varied from 5 to 7 meters

Selection of watermelon genotypes for resistance to bacterial fruit blotch.

Bacterial fruit blotch, caused by Acidovorax citrulli, is a serious threat to the watermelon crop in Brazil

Radiological Features of Male Breast Neoplasms: How to Improve the Management of a Rare Disease

The primary aim of our study was to assess the main mammographic and ultrasonographic features of invasive male breast malignancies. The secondary aim was to evaluate whether a specific radiological presentation would be associated with a worse receptor profile. Radiological images (mammography and/or ultrasound) of all patients who underwent surgery for male invasive breast cancer in our institution between 2008 and 2023 were retrospectively analyzed by two breast radiologists in consensus. All significant features of radiological presentation known in the literature were re-evaluated. Fifty-six patients were selected. The mean age at surgery of patients was 69 years (range: 35-81); in 82% of cases (46 patients), the histologic outcome was invasive ductal carcinoma. A total of 28 out of 56 (50%) patients had preoperative mammography; in 9/28 cases (32%), we found a mass with microcalcifications on mammography. The mass presented high density in 25 out of 28 patients (89%); the mass showed irregular margins in 15/28 (54%) cases. A total of 46 out of 56 patients had preoperative ultrasounds. The lesion showed a solid mass in 41/46 (89%) cases. In 5/46 patients (11%), the lesion was a mass with a mixed (partly liquid-partly solid) structure. We did not find any statistically significant correlation between major types of radiological presentation and tumor receptor arrangement. Knowledge of the main radiologic presentation patterns of malignant male breast neoplasm can help better manage this type of disease, which is rare but whose incidence is increasing

A non-linear Oscillator with quasi-Harmonic behaviour: two- and nn-dimensional Oscillators

A nonlinear two-dimensional system is studied by making use of both the Lagrangian and the Hamiltonian formalisms. The present model is obtained as a two-dimensional version of a one-dimensional oscillator previously studied at the classical and also at the quantum level. First, it is proved that it is a super-integrable system, and then the nonlinear equations are solved and the solutions are explicitly obtained. All the bounded motions are quasiperiodic oscillations and the unbounded (scattering) motions are represented by hyperbolic functions. In the second part the system is generalized to the case of $n$ degrees of freedom. Finally, the relation of this nonlinear system with the harmonic oscillator on spaces of constant curvature, two-dimensional sphere $S^2$ and hyperbolic plane $H^2$, is discussed.Comment: 30 pages, 4 figures, submitted to Nonlinearit