Simulation of resistance and deformability of rocks via discrete elements with cemented particles

O Método dos Elementos Discretos (DEM) aparece como um dos métodos mais atraentes para entender problemas geotécnicos gerais e especificamente o comportamento de rochas devido às suas vantagens únicas em lidar com processos de fraturamento. Neste trabalho, foram feitas modelagens de ensaios de compressão simples e de tração indireta relativos a uma rocha magmática, conhecida como granito Lac du Bonnet, com base em uma abordagem discreta, utilizando o DEM e um modelo específico de contato e de cimentação entre grãos. Concluindo, foi realizada uma análise paramétrica da influência do módulo de Young em algumas propriedades macroscópicas do modelo numérico da rocha, visando gerar contribuições no entendimento do comportamento de resistência e de deformabilidade de rochas duras.The Discrete Element Method (DEM) appears as one of the most attractive methods for understanding general geotechnical problems and specifically the behavior of rocks due to their unique advantages in dealing with fracturing processes. In this work, unconfined compression and indirect tensile tests were performed for a magmatic rock, known as Lac du Bonnet granite, based on a discrete approach using DEM and a specific contact and cementation model between the particles. Concluding, a parametric analysis of the influence of Young's modulus on some macroscopic properties of the rock’s numerical model was carried out, with the objective of generating contributions as to the understanding of the deformability and strength behavior of hard rocks.Peer Reviewe

A Simple Method for Quantifying Functional Selectivity and Agonist Bias

Activation of seven-transmembrane (7TM) receptors by agonists does not always lead to uniform activation of all signaling pathways mediated by a given receptor. Relative to other ligands, many agonists are “biased” toward producing subsets of receptor behaviors. A hallmark of such “functional selectivity” is cell type dependence; this poses a particular problem for the profiling of agonists in whole cell test systems removed from the therapeutic one(s). Such response-specific cell-based variability makes it difficult to guide medicinal chemistry efforts aimed at identifying and optimizing therapeutically meaningful agonist bias. For this reason, we present a scale, based on the Black and Leff operational model, that contains the key elements required to describe 7TM agonism, namely, affinity (KA–1) for the receptor and efficacy (τ) in activating a particular signaling pathway. Utilizing a “transduction coefficient” term, log(τ/KA), this scale can statistically evaluate selective agonist effects in a manner that can theoretically inform structure–activity studies and/or drug candidate selection matrices. The bias of four chemokines for CCR5-mediated inositol phosphate production versus internalization is quantified to illustrate the practical application of this method. The independence of this method with respect to receptor density and the calculation of statistical estimates of confidence of differences are specifically discussed

Crafting urban equality through grassroots critical pedagogies: weave, sentipensar, mobilize, reverberate, emancipate

How do ordinary citizens, activists and urban practitioners learn to become agents of change for a socially just habitat? The paper explores this question through the experiences of eight grassroots schools of popular urbanism working under the umbrella of the Habitat International Coalition (HIC) in Latin America. Building on a process of self-documentation and collective pedagogic reflection driven by the protagonists of these schools, the analysis explores the core pedagogic practices identified across the schools to enact popular urbanism as a collective and intentional praxis: to weave, sentipensar, mobilize, reverberate and emancipate. We argue that, put in motion, these pedagogic practices transgress the rules and boundaries of the formal classroom, taking participants to and through other sites and modes of learning that host significant potential to stimulate collectivizing and alternative ways of seeking change towards urban equality

Feasibility, safety and accuracy of dobutamine/atropine stress echocardiography for the detection of coronary artery disease in renal transplant candidates

OBJECTIVE: To evaluate the feasibility, safety and accuracy of dobutamine/atropine stress echocardiography (DASE) for the detection of coronary artery desease (CAD) in renal transplant candidates. METHODS: Patients candidates to renal transplant were submitted consecutively to DASE and coronary angiography. The adopted angiographic criteria for CAD were an obstructive lesion of > 50% and > 70%. RESULTS: 148 patients underwent the DASE and the coronary angiography. Mean age was 52 ± 9 years, 69% of the patients were males; 27% had diabetic nephropathy and 73% had LVH; 63% were asymptomatic; 36% and 22% presented coronary obstructions > 50% and 70%, respectively. The DASE performance was 91% and major complication rate was 2.7%. The sensibility, specificity and accuracy for the diagnosis of coronary obstruction > 50% were 53% (CI:45-61), 87% (CI:81-93), and 75% (CI:63-83) respectively. For coronary obstruction > 70% these values were, respectively, 71% (CI:64-92), 85% (CI:79-91) and 81% (CI:75-87). The sensibility to detect univessel and multivessel disease was 41% (CI:19-63) and 78% (CI:64-92), respectively. CONCLUSION: The DASE was practical and safe; however, it presented a poor result for the detection of CAD regarding obstructions > 50%. It can be a useful screening for the detection of CAD in candidates with obstructions > 70% and multivessel disease.OBJETIVO: Avaliar a exeqüibilidade, a segurança e a acurácia diagnóstica do ecocardiograma sob estresse (EEDA) com dobutamina/atropina em candidatos a transplante renal. MÉTODOS: Pacientes candidatos a transplante renal com e sem nefropatia diabética realizaram EEDA e cineangiocoronariografia. Consideraram-se dois pontos de corte para doença arterial coronariana (DAC): > 50% e > 70% de obstrução de uma artéria epicárdica. RESULTADOS: Cento e quarenta e oito pacientes realizaram o EEDA e a angiografia coronariana. A média de idade foi de 52±9 anos, 69% eram do sexo masculino, 27% tinham nefropatia diabética, e 73%, HVE; 63% estavam assintomáticos, 36% e 22% apresentaram obstruções coronarianas > 50% e > 70%, respectivamente. A exeqüibilidade foi de 91% e houve 2,7% de complicações maiores. Obtiveram-se as seguintes médias de sensibilidade, especificidade e acurácia, considerando obstrução coronariana > 50%: 53% (IC:45-61), 87% (IC:81-93), e 75% (IC:63-83), respectivamente. Para obstrução >70%, 71% (IC:64-92), 85% (IC:79-91) e 81% (IC:75-87). A sensibilidade para diagnosticar doença uniarterial foi 41% (IC:19-63) e doença multiarterial, 78% (IC:64-92). CONCLUSÃO: O EEDA foi exeqüível e seguro; entretanto, foi ineficiente para rastreamento de DAC, considerando obstruções > 50%, mas pode ser útil para detecção de DAC em pacientes com obstruções > 70% e doença multiarterial.Universidade Federal de São Paulo (UNIFESP) Escola Paulista de Medicina Hospital do Rim e HipertensãoUniversidade Federal de São Paulo (UNIFESP) Escola Paulista de Medicina Hospital São PauloUNIFESP, EPM, Hospital do Rim e HipertensãoUNIFESP, EPM, Hospital São PauloSciEL

The clustering of ultra-high energy cosmic rays and their sources

The sky distribution of cosmic rays with energies above the 'GZK cutoff' holds important clues to their origin. The AGASA data, although consistent with isotropy, shows evidence for small-angle clustering, and it has been argued that such clusters are aligned with BL Lacertae objects, implicating these as sources. It has also been suggested that clusters can arise if the cosmic rays come from the decays of very massive relic particles in the Galactic halo, due to the expected clumping of cold dark matter. We examine these claims and show that both are in fact not justified.Comment: 13 pages, 8 figures, version in press at Phys. Rev.

Cross-Correlation between UHECR Arrival Distribution and Large-Scale Structure

We investigate correlation between the arrival directions of ultra-high-energy cosmic rays (UHECRs) and the large-scale structure (LSS) of the Universe by using statistical quantities which can find the angular scale of the correlation. The Infrared Astronomical Satellite Point Source Redshift Survey (IRAS PSCz) catalog of galaxies is adopted for LSS. We find a positive correlation of the highest energy events detected by the Pierre Auger Observatory (PAO) with the IRAS galaxies inside $z=0.018$ within the angular scale of $\sim 15^{\circ}$. This positive correlation observed in the southern sky implies that a significant fraction of the highest energy events comes from nearby extragalactic objects. We also analyze the data of the Akeno Giant Air Shower Array (AGASA) which observed the northern hemisphere, but the obvious signals of positive correlation with the galaxy distribution are not found. Since the exposure of the AGASA is smaller than the PAO, the cross-correlation in the northern sky should be tested using a larger number of events detected in the future. We also discuss the correlation using the all-sky combined data sets of both the PAO and AGASA, and find a significant correlation within $\sim 8^{\circ}$. These angular scales can constrain several models of intergalactic magnetic field. These cross-correlation signals can be well reproduced by a source model in which the distribution of UHECR sources is related to the IRAS galaxies.Comment: 21 pages,7 figure

IceHEP High Energy Physics at the South Pole

With the solar and SN87 neutrino observations as proofs of concepts, the kilometer-scale neutrino experiment IceCube will scrutinize its data for new particle physics. In this paper we review the prospects for the realization of such a program. We begin with a short overview of the detector response and discuss the reach of ``beam'' luminosity. After that we discuss the potential of IceCube to probe deviations of neutrino-nucleon cross sections from the Standard Model predictions at center-of-mass energies well beyond those accessible in man-made accelerators. Then we review the prospects for extremely long-baseline analyses and discuss the sensitivity to measure tiny deviations of the flavor mixing angle, expected to be induced by quantum gravity effects. Finally we discuss the potential to uncover annihilation of dark matter particles gravitationally trapped at the center of the Sun, as well as processes occurring in the early Universe at energies close to the Grand Unification scale.Comment: Typos corrected and references added. Version with high resolution figures available at http://www.hep.physics.neu.edu/staff/doqui/icehep_rev6.p

Ras-mediated Loss of the Pro-apoptotic Response Protein Par-4 Is Mediated by DNA Hypermethylation through Raf-independent and Raf-dependent Signaling Cascades in Epithelial Cells

The apoptosis-promoting protein Par-4 has been shown to be down-regulated in Ras-transformed NIH 3T3 fibroblasts through the Raf/MEK/ERK MAPK pathway. Because mutations of the ras gene are most often found in tumors of epithelial origin, we explored the signaling pathways utilized by oncogenic Ras to down-regulate Par-4 in RIE-1 and rat ovarian surface epithelial (ROSE) cells. We determined that constitutive activation of the Raf, phosphatidylinositol 3-kinase, or Ral guanine nucleotide exchange factor effector pathway alone was not sufficient to down-regulate Par-4 in RIE-1 or ROSE cells. However, treatment of Ras-transformed RIE-1 or ROSE cells with the MEK inhibitors U0126 and PD98059 increased Par-4 protein expression. Thus, although oncogenic Ras utilizes the Raf/MEK/ERK pathway to down-regulate Par-4 in both fibroblasts and epithelial cells, Ras activation of an additional signaling pathway(s) is required to achieve the same outcome in epithelial cells. Methylation-specific PCR showed that the par-4 promoter is methylated in Ras-transformed cells through a MEK-dependent pathway and that treatment with the DNA methyltransferase inhibitor azadeoxycytidine restored Par-4 mRNA transcript and protein levels, suggesting that the mechanism for Ras-mediated down-regulation of Par-4 is by promoter methylation. Support for this possibility is provided by our observation that Ras transformation was associated with up-regulation of Dnmt1 and Dnmt3 DNA methyltransferase expression. Finally, ectopic Par-4 expression significantly reduced Ras-mediated growth in soft agar, but not morphological transformation, highlighting the importance of Par-4 down-regulation in specific aspects of Ras-mediated transformation of epithelial cells

Images of very high energy cosmic ray sources in the Galaxy: I. A source towards the Galactic Centre

Recent analyses of the anisotropy of cosmic rays at $10^{18}$ eV (the AGASA and SUGAR data) show significant excesses from regions close to the Galactic Centre and Cygnus. Our aim is to check whether such anisotropies can be caused by single sources of charged particles. We investigate propagation of protons in two models of the Galactic regular magnetic field (with the irregular component included) assuming that the particles are injected by a short lived discrete source lying in the direction of the Galactic Centre. We show that apart from a prompt image of the source, the regular magnetic field may cause delayed images at quite large angular distances from the actual source direction. The image is strongly dependent on the time elapsed after ejection of particles and it is also very sensitive to their energy. For the most favourable conditions for particle acceleration by a young pulsar the predicted fluxes are two to four order of magnitudes higher than that observed. The particular numbers depend strongly on the Galactic magnetic field model adopted but it looks that a single pulsar in the Galactic Centre could be responsible for the observed excess.Comment: 20 pages, 7 figures, accepted to J. Phys.

Cosmic Rays from the Knee to the Highest Energies

This review summarizes recent developments in the understanding of high-energy cosmic rays. It focuses on galactic and presumably extragalactic particles in the energy range from the knee (10^15 eV) up to the highest energies observed (>10^20 eV). Emphasis is put on observational results, their interpretation, and the global picture of cosmic rays that has emerged during the last decade.Comment: Invited review, submitted to Progress in Particle and Nuclear Physic