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Monte carlo

Thomas R Hurd, James P Gleeson, Sergey Melnik
We introduce a probabilistic framework that represents stylized banking networks with the aim of predicting the size of contagion events. Most previous work on random financial networks assumes independent connections between banks, whereas our framework explicitly allows for (dis)assortative edge probabilities (i.e., a tendency for small banks to link to large banks). We analyze default cascades triggered by shocking the network and find that the cascade can be understood as an explicit iterated mapping on a set of edge probabilities that converges to a fixed point...
2017: PloS One
Mengfei Fan, Zhiguo Zeng, Enrico Zio, Rui Kang, Ying Chen
In this paper, we develop a framework to model and analyze systems that are subject to dependent, competing degradation processes and random shocks. The degradation processes are described by stochastic differential equations, whereas transitions between the system discrete states are triggered by random shocks. The modeling is, then, based on Stochastic Hybrid Systems (SHS), whose state space is comprised of a continuous state determined by stochastic differential equations and a discrete state driven by stochastic transitions and reset maps...
2017: PloS One
Maria C Giannakourou, Nikolaos G Stoforos
Traditionally, for the determination of the kinetic parameters of thermal inactivation of a heat labile substance, an appropriate index is selected and its change is measured over time at a series of constant temperatures. The rate of this change is described through an appropriate primary model and a secondary model is applied to assess the impact of temperature. By this approach, the confidence intervals of the estimates of the rate constants are not taken into account. Consequently, the calculated variability of the secondary model parameters can be significantly lower than the actual variability...
January 12, 2017: Foods (Basel, Switzerland)
Giovanni Marini, Giorgio Guzzetta, Frederic Baldacchino, Daniele Arnoldi, Fabrizio Montarsi, Gioia Capelli, Annapaola Rizzoli, Stefano Merler, Roberto Rosà
BACKGROUND: Aedes albopictus and Culex pipiens larvae reared in the same breeding site compete for resources, with an asymmetrical outcome that disadvantages only the latter species. The impact of these interactions on the overall ecology of these two species has not yet been assessed in the natural environment. In the present study, the temporal patterns of adult female mosquitoes from both species were analysed in north-eastern Italy, and substantial temporal shifts between abundance curves of Cx...
February 23, 2017: Parasites & Vectors
Nathan A Mahynski, Marco A Blanco, Jeffrey R Errington, Vincent K Shen
We present a method for predicting the free energy landscape of fluids at low temperatures from flat-histogram grand canonical Monte Carlo simulations performed at higher ones. We illustrate our approach for both pure and multicomponent systems using two different sampling methods as a demonstration. This allows us to predict the thermodynamic behavior of systems which undergo both first order and continuous phase transitions upon cooling using simulations performed only at higher temperatures. After surveying a variety of different systems, we identify a range of temperature differences over which the extrapolation of high temperature simulations tends to quantitatively predict the thermodynamic properties of fluids at lower ones...
February 21, 2017: Journal of Chemical Physics
Han Luo, Marat Kulakhmetov, Alina Alexeenko
Quasi-classical trajectory (QCT) calculations are used in this work to calculate state-specific N2(X(1)Σ)+O((3)P)→2N((4)S)+O((3)P) dissociation and N2(X(1)Σ)+O((3)P)→NO(X(2)Π)+N((4)S) exchange cross sections and rates based on the 1(3)A″ and 1(3)A' ab initio potential energy surface by Gamallo et al. [J. Chem. Phys. 119, 2545-2556 (2003)]. The calculations consider translational energies up to 23 eV and temperatures between 1000 K and 20 000 K. Vibrational favoring is observed for dissociation reaction at the whole range of collision energies and for exchange reaction around the dissociation limit...
February 21, 2017: Journal of Chemical Physics
Shuai Zhang, Kevin P Driver, François Soubiran, Burkhard Militzer
As one of the simple alkali metals, sodium has been of fundamental interest for shock physics experiments, but knowledge of its equation of state (EOS) in hot, dense regimes is not well known. By combining path integral Monte Carlo (PIMC) results for partially ionized states [B. Militzer and K. P. Driver, Phys. Rev. Lett. 115, 176403 (2015)] at high temperatures and density functional theory molecular dynamics (DFT-MD) results at lower temperatures, we have constructed a coherent equation of state for sodium over a wide density-temperature range of 1...
February 21, 2017: Journal of Chemical Physics
S Morato, B Juste, R Miro, G Verdu, S Diez, S Morato, B Juste, R Miro, G Verdu, S Diez, B Juste, S Diez, R Miro, S Morato, G Verdu
This work presents a Monte Carlo simulation using the last version of MCNP, v. 6.1.1, of a Varian CLinAc emitting a 15MeV photon beam. The main objective of the work is to estimate the photoneutron production and activated products inside the medical linear accelerator head. To that, the Varian LinAc head was modelled in detail using the manufacturer information, and the model was generated with a CAD software and exported as a mesh to be included in the particle transport simulation. The model includes the transport of photoneutrons generated by primary photons and the (n, γ) reactions which can result in activation products...
August 2016: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
Yuncheng Du, Dongping Du, Yuncheng Du, Dongping Du, Dongping Du, Yuncheng Du
Cardiac potassium (K+) channel plays an important role in cardiac electrical signaling. Mathematical models have been widely used to investigate the effects of K+ channels on cardiac functions. However, the model of K+ channel involves parametric uncertainties, which can be induced by fitting the model's parameters that best capture experimental data. Since the prediction of cardiac functions are highly parameter-dependent, it is critical to quantify the influence of parametric uncertainty on the model responses to provide the more reliable predictions...
August 2016: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
Andrea Duggento, Marco Giannelli, Carlo Tessa, Simona Lanzafame, Maria Guerrisi, Nicola Toschi, Andrea Duggento, Marco Giannelli, Carlo Tessa, Simona Lanzafame, Maria Guerrisi, Nicola Toschi, Nicola Toschi, Maria Guerrisi, Marco Giannelli, Carlo Tessa, Simona Lanzafame, Andrea Duggento
Diffusion tensor imaging (DTI) provides exquisite sensitivity to structural and microstructural characteristics of brain tissue, and is routinely employed in advanced neuroimaging applications. DTI is commonly performed using intrinsically noisy echo-planar imaging techniques and poses high demands both on scanner performance and on in-scanner subject time, which in turn is directly related to the number of diffusion-weighting direction one requires. While DTI-derived indices such as fractional anisotropy (FA), diffusion tensor trace and anisotropy mode have proven extremely useful in characterizing disease-related aberrations, their estimation is commonly performed using fitting routines that do not properly take into account MRI noise distribution...
August 2016: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
Trieu H Pham, Pubudu N Pathirana, Trieu H Pham, Pubudu N Pathirana, Trieu H Pham, Pubudu N Pathirana
Describing the flexibility of the hand using the reachable space concept has drawn the attention of many researchers in recent years. Existing approaches involving numerical techniques to obtain the reachable space are generally computationally expensive. In this study, we propose a resource-friendly approach to determine and quantify the bidimensional reachable space of the finger. The fundamental idea of the approach connects to a set of arc formulae for the boundary of the reachable space. These formulae of the boundary result a unique description to calculate the area of the reachable space using Green's theorem...
August 2016: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
Brian S Robinson, Theodore W Berger, Dong Song, Brian S Robinson, Theodore W Berger, Dong Song, Brian S Robinson, Dong Song, Theodore W Berger
As increasingly complex non-stationary models become possible to be identified from neural data, rigorous validation approaches must be developed to rule out overfitting and the potential to identify features by chance. Specifically, identification of spike-timing-dependent plasticity (STDP) from recorded spontaneous in vivo spike timing is a potentially powerful tool to quantify activity-dependent plasticity. In previous work, we presented a methodology to perform this STDP identification from spike timing alone and successfully identified a generative model...
August 2016: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
Jeffrey J Cies, Keri N Fugarolas, Wayne S Moore, Robert W Mason, Ogechukwu R Menkiti
STUDY OBJECTIVE: To describe the population pharmacokinetics and pharmacodynamic target attainment of ampicillin in neonates with hypoxic-ischemic encephalopathy (HIE) undergoing controlled hypothermia (CH). DESIGN: Prospective, open-label pharmacokinetic study. SETTING: 189-bed, freestanding children's tertiary care teaching hospital. PATIENTS: Thirteen neonates (three females, 10 males) with HIE encephalopathy receiving CH and ampicillin 100 mg/kg/dose intravenously every 8 hours who were admitted to the neonatal intensive care unit between May 2013 and June 2014...
February 22, 2017: Pharmacotherapy
Hilary L Byrne, Yaser Gholami, Zdenka Kuncic
The addition of gold nanoparticles within target tissue (i.e. a tumour) to enhance the delivered radiation dose is a well studied radiotherapy treatment strategy, despite not yet having been translated into standard clinical practice. While several studies have used Monte Carlo simulations to investigate radiation dose enhancement by Auger electrons emitted from irradiated gold nanoparticles, none have yet considered the effects due to escaping fluorescence photons. Geant4 was used to simulate a water phantom containing 10 mg/mL uniformly dispersed gold (1% by mass) at 5cm depth...
February 22, 2017: Physics in Medicine and Biology
John M McBride, Carlos Avendaño
We investigate the phase behaviour and self-assembly of convex spherical caps using Monte Carlo simulations. This model is used to represent the main features observed in experimental colloidal particles with mushroom-cap shape [Riley et al., Langmuir, 2010, 26, 1648]. The geometry of this non-centrosymmetric convex model is fully characterized by the aspect ratio χ* defined as the spherical cap height to diameter ratio. We use NPT Monte Carlo simulations combined with free energy calculations to determine the most stable crystal structures and the phase behaviour of convex spherical caps with different aspect ratios...
February 22, 2017: Soft Matter
Dong-Hwan Lee, Yong Kyun Kim, Kyubok Jin, Myoung Joo Kang, Young-Don Joo, Yang Wook Kim, Young Soo Moon, Jae-Gook Shin, Sungmin Kiem
We investigated population pharmacokinetics (PK) of doripenem in Korean patients with acute infections, and determined an appropriate dosing regimen using a Monte-Carlo simulation for predicting pharmacodynamics (PD). Patients (n = 37) with a creatinine clearance (CLCR) of 20∼50 mL/min or >50 mL/min who received a 250-mg or 500-mg dose of doripenem over the course of one hour every eight hours, respectively, were included in this study. Blood samples were taken pre-dose and 0 h, 0.5 h, and 4-6 h after the fourth infusion...
February 21, 2017: Antimicrobial Agents and Chemotherapy
Ahmed A Abokifa, Pratim Biswas
Partial replacement of lead service lines (LSLs) often results in the excessive long-term release of lead particulates due to the disturbance of pipe scale and galvanic corrosion. In this study, a modeling approach to simulate the release and transport of particulate and dissolved lead from full and partially replaced LSLs is developed. A mass transfer model is coupled with a stochastic residential water demand generator to investigate the effect of normal household usage (NHU) flow patterns on lead exposure...
February 21, 2017: Environmental Science & Technology
Yang Liu, John R Buck, Vasiliki N Ikonomidou
This paper proposes a new design strategy for optimizing MRI pulse sequences for T1 relaxometry. The design strategy optimizes the pulse sequence parameters to minimize the maximum variance of unbiased T1 estimates over a range of T1 values using the Cramér-Rao bound. In contrast to prior sequences optimized for a single nominal T1 value, the optimized sequence using our bound-based strategy achieves improved precision and accuracy for a broad range of T1 estimates within a clinically feasible scan time. The optimization combines the downhill simplex method with a simulated annealing process...
2017: PloS One
A N Ø Schultz, N Høiby, X C Nielsen, T Pressler, K Dalhoff, M Duno, A Buchard, H K Johansen, H Wang, C S Dalbøge
Ciprofloxacin (CIP) is frequently used when treating cystic fibrose (CF) patients with intermittent Pseudomonas aeruginosa (P. aeruginosa) lung colonization. However, approximately 20% of the patients progress to chronic infection despite early intervention. The aim of this study, was to investigate the pharmacokinetics of CIP, to evaluate if CYP3A4-related metabolism is involved and to find the optimal dose needed to eradicate intermittently colonizing bacteria in the lungs of CF patients. Methods An open-label, prospective pharmacokinetic study was performed...
March 2017: Pediatric Pulmonology
Gray Lu, Steven Marsh, Jerome Damet, Pierre Carbonez, John Laban, Christopher Bateman, Anthony Butler, Phil Butler
Spectral computed tomography (CT) is an up and coming imaging modality which shows great promise in revealing unique diagnostic information. Because this imaging modality is based on X-ray CT, it is of utmost importance to study the radiation dose aspects of its use. This study reports on the implementation and evaluation of a Monte Carlo simulation tool using TOPAS for estimating dose in a pre-clinical spectral CT scanner known as the MARS scanner. Simulated estimates were compared with measurements from an ionization chamber...
February 20, 2017: Australasian Physical & Engineering Sciences in Medicine
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