On outflow boundary conditions for CT-based computation of FFR: Examination using PET images

CT-based computations of fractional flow reserve (FFR) have been widely utilized for evaluating functional severity of a coronary artery stenosis. Whilst this approach has been successful clinically, assumptions involved in the analysis still need to be investigated for further improvement in predictive accuracy. To better understand the sensitivity of computational FFRs on outflow boundary condition – typically reflecting patient's own physiology only through anatomical features – FFR computations for 10 patients with different degree of stenosis was conducted. The computations were based on 3D anatomical model reconstructed from CT images and patient-specific in/outflow boundary conditions (BC). Two outflow BCs were considered: (1) conventional morphology-based and (2) PET perfusion-based conditions. The results showed that the FFRs derived from the two boundary conditions agree in general. It was also found that the FFRs computed with the morphology-based BC tend to estimate higher functional severity, especially in patients with reduced vasodilatory response under hyperaemia – an essential physiological condition in FFR measurement. Further investigation was made by varying hyperaemic resistances (30%-90% of the baseline) in the morphology-based BC. The variation of FFR for the varied resistances was narrow for patients with mild stenosis and wider for those who have severe stenosis. This latter approach confirmed that variability of FFR due to outflow condition tends to come from overestimation of vasodilatory response, especially those who have abnormal myocardial perfusion. The results suggest that outflow conditions that are more representative of each patient could be an effective way to improve CT-based FFR computation

Trust transitivity in social networks

Non-centralized recommendation-based decision making is a central feature of several social and technological processes, such as market dynamics, peer-to-peer file-sharing and the web of trust of digital certification. We investigate the properties of trust propagation on networks, based on a simple metric of trust transitivity. We investigate analytically the percolation properties of trust transitivity in random networks with arbitrary degree distribution, and compare with numerical realizations. We find that the existence of a non-zero fraction of absolute trust (i.e. entirely confident trust) is a requirement for the viability of global trust propagation in large systems: The average pair-wise trust is marked by a discontinuous transition at a specific fraction of absolute trust, below which it vanishes. Furthermore, we perform an extensive analysis of the Pretty Good Privacy (PGP) web of trust, in view of the concepts introduced. We compare different scenarios of trust distribution: community- and authority-centered. We find that these scenarios lead to sharply different patterns of trust propagation, due to the segregation of authority hubs and densely-connected communities. While the authority-centered scenario is more efficient, and leads to higher average trust values, it favours weakly-connected "fringe" nodes, which are directly trusted by authorities. The community-centered scheme, on the other hand, favours nodes with intermediate degrees, in detriment of the authorities and its "fringe" peers.Comment: 11 pages, 9 figures (with minor corrections

Measurement of the top quark mass using the matrix element technique in dilepton final states

We present a measurement of the top quark mass in pp¯ collisions at a center-of-mass energy of 1.96 TeV at the Fermilab Tevatron collider. The data were collected by the D0 experiment corresponding to an integrated luminosity of 9.7  fb−1. The matrix element technique is applied to tt¯ events in the final state containing leptons (electrons or muons) with high transverse momenta and at least two jets. The calibration of the jet energy scale determined in the lepton+jets final state of tt¯ decays is applied to jet energies. This correction provides a substantial reduction in systematic uncertainties. We obtain a top quark mass of mt=173.93±1.84  GeV

Electroporation increases antitumoral efficacy of the bcl-2 antisense G3139 and chemotherapy in a human melanoma xenograft

<p>Abstract</p> <p>Background</p> <p>Nucleic acids designed to modulate the expression of target proteins remain a promising therapeutic strategy in several diseases, including cancer. However, clinical success is limited by the lack of efficient intracellular delivery. In this study we evaluated whether electroporation could increase the delivery of antisense oligodeoxynucleotides against bcl-2 (G3139) as well as the efficacy of combination chemotherapy in human melanoma xenografts.</p> <p>Methods</p> <p>Melanoma-bearing nude mice were treated i.v. with G3139 and/or cisplatin (DDP) followed by the application of trains of electric pulses to tumors. Western blot, immunohistochemistry and real-time PCR were performed to analyze protein and mRNA expression. The effect of electroporation on muscles was determined by histology, while tumor apoptosis and the proliferation index were analyzed by immunohistochemistry. Antisense oligodeoxynucleotides tumor accumulation was measured by FACS and confocal microscopy.</p> <p>Results</p> <p>The G3139/Electroporation combined therapy produced a significant inhibition of tumor growth (TWI, more than 50%) accompanied by a marked tumor re-growth delay (TRD, about 20 days). The efficacy of this treatment was due to the higher G3139 uptake in tumor cells which led to a marked down-regulation of bcl-2 protein expression. Moreover, the G3139/EP combination treatment resulted in an enhanced apoptotic index and a decreased proliferation rate of tumors. Finally, an increased tumor response was observed after treatment with the triple combination G3139/DDP/EP, showing a TWI of about 75% and TRD of 30 days.</p> <p>Conclusions</p> <p>These results demonstrate that electroporation is an effective strategy to improve the delivery of antisense oligodeoxynucleotides within tumor cells <it>in vivo </it>and it may be instrumental in optimizing the response of melanoma to chemotherapy. The high response rate observed in this study suggest to apply this strategy for the treatment of melanoma patients.</p

Mesenchymal cell survival in airway and interstitial pulmonary fibrosis

Fibrotic reactions in the airways of the lung or the pulmonary interstitium are a common pathologic outcome after exposure to a wide variety of toxic agents, including metals, particles or fibers. The survival of mesenchymal cells (fibroblasts and myofibroblasts) is a key factor in determining whether a fibroproliferative response that occurs after toxic injury to the lung will ultimately resolve or progress to a pathologic state. Several polypeptide growth factors, including members of the platelet-derived growth factor (PDGF) family and the epidermal growth factor (EGF) family, are prosurvival factors that stimulate a replicative and migratory mesenchymal cell phenotype during the early stages of lung fibrogenesis. This replicative phenotype can progress to a matrix synthetic phenotype in the presence of transforming growth factor-β1 (TGF-β1). The resolution of a fibrotic response requires growth arrest and apoptosis of mesenchymal cells, whereas progressive chronic fibrosis has been associated with mesenchymal cell resistance to apoptosis. Mesenchymal cell survival or apoptosis is further influenced by cytokines secreted during Th1 inflammation (e.g., IFN-γ) or Th2 inflammation (e.g., IL-13) that modulate the expression of growth factor activity through the STAT family of transcription factors. Understanding the mechanisms that regulate the survival or death of mesenchymal cells is central to ultimately developing therapeutic strategies for lung fibrosis