Density-dependent interactions and structure of charged colloidal dispersions in the weak screening regime

We determine the structure of charge-stabilized colloidal suspensions at low ionic strength over an extended range of particle volume fractions using a combination of light and small angle neutron scattering experiments. The variation of the structure factor with concentration is analyzed within a one-component model of a colloidal suspension. We show that the observed structural behavior corresponds to a non-monotonic density dependence of the colloid effective charge and the mean interparticle interaction energy. Our findings are corroborated by similar observations from primitive model computer simulations of salt-free colloidal suspensions.Comment: Revised version, accepted to Phys. Rev. Let

Macroscopic evidence of microscopic dynamics in the Fermi-Pasta-Ulam oscillator chain from nonlinear time series analysis

The problem of detecting specific features of microscopic dynamics in the macroscopic behavior of a many-degrees-of-freedom system is investigated by analyzing the position and momentum time series of a heavy impurity embedded in a chain of nearest-neighbor anharmonic Fermi-Pasta-Ulam oscillators. Results obtained in a previous work [M. Romero-Bastida, Phys. Rev. E {\bf69}, 056204 (2004)] suggest that the impurity does not contribute significantly to the dynamics of the chain and can be considered as a probe for the dynamics of the system to which the impurity is coupled. The ($r,\tau$) entropy, which measures the amount of information generated by unit time at different scales $\tau$ of time and $r$ of the observable, is numerically computed by methods of nonlinear time-series analysis using the position and momentum signals of the heavy impurity for various values of the energy density $\epsilon$ (energy per degree of freedom) of the system and some values of the impurity mass $M$. Results obtained from these two time series are compared and discussed.Comment: 7 pages, 5 figures, RevTeX4 PRE format; to be published in Phys. Rev.

Qualidade físico-química e sensorial de cultivares de morango durante o armazenamento refrigerado.

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Infinite-contrast periodic composites with strongly nonlinear behavior: Effective-medium theory versus full-field simulations

This paper presents a combined numerical-theoretical study of the macroscopic behavior and local field distributions in a special class of two-dimensional periodic composites with viscoplastic phases. The emphasis is on strongly nonlinear materials containing pores or rigid inclusions. Full-field numerical simulations are carried out using a Fast-Fourier Transform algorithm [H. Moulinec, P. Suquet, C. R. Acad. Sci. Paris II 318, 1417 (1994)] Moulinec, P. Suquet, C. R. Acad. Sci. Paris II 318, 1417 (1994), while the theoretical results are obtained by means of the `second-order' nonlinear homogenization method [P. Ponte Castaneda, J. Mech. Phys. Solids 50, 737 (2002)]. The effect of nonlinearity and inclusion concentration is investigated in the context of power-law (with strain-rate sensitivity m) behavior for the matrix phase under in-plane shear loadings. Overall, the `second-order' estimates are found to be in good agreement with the numerical simulations, with the best agreement for the rigidly reinforced materials. For the porous systems, as the nonlinearity increases (m decreases), the strain field is found to localize along shear bands passing through the voids (the strain fluctuations becoming unbounded) and the effective stress exhibits a singular behavior in the dilute limit. More specifically, for small porosities and fixed nonlinearity m>0, the effective stress decreases linearly with increasing porosity. However, for ideally plastic behavior (m = 0), the dependence on porosity becomes non-analytic. On the other hand, for rigidly-reinforced composites, the strain field adopts a tile pattern with bounded strain fluctuations, and no singular behavior is observed (to leading order) in the dilute limit.Comment: 28 pages, 28 B&W figures, 2 tables of color maps, to be published in International Journal of Solids and Structures (in press

Testing the relevance of effective interaction potentials between highly charged colloids in suspension

Combining cell and Jellium model mean-field approaches, Monte Carlo together with integral equation techniques, and finally more demanding many-colloid mean-field computations, we investigate the thermodynamic behavior, pressure and compressibility of highly charged colloidal dispersions, and at a more microscopic level, the force distribution acting on the colloids. The Kirkwood-Buff identity provides a useful probe to challenge the self-consistency of an approximate effective screened Coulomb (Yukawa) potential between colloids. Two effective parameter models are put to the test: cell against renormalized Jellium models

Synchronous or collision solid neoplasms and lymphomas: A systematic review of 308 case reports.

The presence of a lymphoma associated with a solid synchronous neoplasm or collision neoplasm has been rarely in the literature, and a detailed characterization of these cases is lacking to date. To describe the main clinicopathological features of synchronous/collision tumors. A systematic search in PubMed, Scielo, and Virtual Health Library literature databases for cases or case series of synchronous or collision lymphoma and other solid neoplasms reported up to March 2021 was performed. Three reviewers independently screened the literature, extracted data, and assessed the quality of the included studies. The systematic review was performed following the Preferred Reporting Items for Systematic Meta-Analyses guidelines. Mean age of patients was 62.9 years (52.9% men). A total of 308 cases were included (62% synchronous and 38% collision). The most frequent location of both synchronous and collision tumors was the gastrointestinal tract with the most common solid neoplasm being adenocarcinoma, and the most frequent lymphoma diffuse large B-cell lymphoma (21.7%) and mucosa-associated lymphoid tissue lymphoma (20.4%). Of the total number of mucosa-associated lymphoid tissue lymphomas and gastric adenocarcinomas, the presence of Helicobacter pylori infection was documented in 47.3% of them. Only 2% of all cases had a previous history of lymphoma. Thus, in most cases (98%), lymphoma was discovery incidentally. In addition, nodal lymphoma was associated with metastasis in 29 (9.4%) cases as collision tumor, most commonly (90%) in locoregional lymph nodes of the solid neoplasm. The frequent association of some type of B-cell lymphoma and adenocarcinoma in synchronous/collision tumors of the gastrointestinal tract points to common pathogenic mechanisms in both neoplasia, particularly related to chronic inflammation in this location. In most cases, lymphoma identified in locoregional lymph nodes or distant of a carcinoma seems to represent an incidental finding during the carcinoma diagnostic/therapeutic approach. A synergy between carcinoma and lymphoma (involving inflammation and immunosuppression mechanisms) may favor tumor progression and dissemination. A better understating of the interactions lymphoma/carcinoma in the setting of synchronous/collision tumors may help to improve patient management and prognosis

Boundary conditions: The path integral approach

The path integral approach to quantum mechanics requires a substantial generalisation to describe the dynamics of systems confined to bounded domains. Non-local boundary conditions can be introduced in Feynman's approach by means of boundary amplitude distributions and complex phases to describe the quantum dynamics in terms of the classical trajectories. The different prescriptions involve only trajectories reaching the boundary and correspond to different choices of boundary conditions of selfadjoint extensions of the Hamiltonian. One dimensional particle dynamics is analysed in detail.Comment: 8 page

Generally covariant state-dependent diffusion

Statistical invariance of Wiener increments under SO(n) rotations provides a notion of gauge transformation of state-dependent Brownian motion. We show that the stochastic dynamics of non gauge-invariant systems is not unambiguously defined. They typically do not relax to equilibrium steady states even in the absence of extenal forces. Assuming both coordinate covariance and gauge invariance, we derive a second-order Langevin equation with state-dependent diffusion matrix and vanishing environmental forces. It differs from previous proposals but nevertheless entails the Einstein relation, a Maxwellian conditional steady state for the velocities, and the equipartition theorem. The over-damping limit leads to a stochastic differential equation in state space that cannot be interpreted as a pure differential (Ito, Stratonovich or else). At odds with the latter interpretations, the corresponding Fokker-Planck equation admits an equilibrium steady state; a detailed comparison with other theories of state-dependent diffusion is carried out. We propose this as a theory of diffusion in a heat bath with varying temperature. Besides equilibrium, a crucial experimental signature is the non-uniform steady spatial distribution.Comment: 24 page

Hospital doctors' views and concerns about pharmacovigilance

Purpose: The aim of the study was to evaluate the opinions and concerns of hospital doctors about adverse drug reactions (ADRs) and pharmacovigilance. Methods: A qualitative study was undertaken using focus groups in sessions on pharmacovigilance activities conducted in thirteen clinical services of a tertiary university hospital. A total of 296 physicians participated in these sessions by giving their opinions or expressing their doubts about ADR and pharmacovigilance activities which were recorded by different observers and subsequently analysed. Results: Doctors remarked on: a) the importance, concern, frequency and specific types of ADRs that were observed in clinical practice; b) problems of clinical decision making related to the suspected ADRs; c) methods for improving detection and reporting ADRs; d) monitoring of specific ADRs or ADRs caused by specific drugs; e) and measures to prevent and minimize the risk of ADRs. Physicians expressed doubts related to: a) the basic concepts of ADRs; b) the methods of ADR identification and evaluation; c) the objectives and procedures of pharmacovigilance programmes; d) and the impact of pharmacovigilance activities. Conclusions: Hospital doctors believe that ADRs are a matter for concern in their daily clinical practice, and monitoring ADRs as well as measures for preventing the risk of ADRs are needed. Nevertheless, doctors have doubts about what an ADR is, the accuracy of diagnostic methods, the development of pharmacovigilance activities and their impact on clinical practice. Pharmacovigilance should be better explained through a continuous feedback and close relationship with hospital doctors