scholarly journals The impact of stellar jitter on the confirmation of transiting exoplanet candidates around Solar-like stars

2008 ◽  
Vol 4 (S253) ◽  
pp. 506-507
Author(s):  
Brandon Tingley ◽  
Frank Grundahl ◽  
Hans Kjeldsen
Keyword(s):  
Time Series ◽  
Monte Carlo ◽  
Monte Carlo Simulations ◽  
Signal Detection ◽  
Radial Velocity ◽  
Good Description ◽  
Sampling Rate ◽  
Upper Limits ◽  
The Impact

AbstractThe radial velocity technique is commonly used to classify transiting exoplanet candidates. However, stars are intrinsically noisy in radial velocity. No good description of this noise has yet been proffered, although activity in general has been suggested as the source, making it impossible to evaluate its effect on signal detection. In this poster, we propose an activity-based model that incorporates both light and dark stellar spots, capable of producing both photometric and radial velocity time series. We demonstrate its consistency with both SOHO/VIRGO photometry and SOHO/GOLF radial velocities. We then use this model to establish lower and upper limits on the effects of intrinsic stellar noise on the metal lines used to follow up transit candidates, making use of Monte Carlo simulations. Based on these results, we can suggest an optimal observational sampling rate.

A Preliminary Assessment of the Robustness of Signal Detection Theory Estimates Using Monte Carlo Simulations for Human Factors Professionals

2018 ◽  
Vol 62 (1) ◽  
pp. 1301-1305
Author(s):  
Brittany Neilson ◽  
Dmitrii Paniukov ◽  
Martina I. Klein
Keyword(s):  
Monte Carlo ◽  
Human Factors ◽  
Monte Carlo Simulations ◽  
Signal Detection ◽  
Signal Detection Theory ◽  
Detection Theory ◽  
Preliminary Assessment ◽  
Assumption Violations ◽  
Homogeneity Of Variance ◽  
The Impact

Signal detection theory is commonly utilized in the field of human factors. Despite its common use, the assessment of the signal detection theory assumptions is not often cited. The purpose of this research was to provide a preliminary assessment of the impact of assumption violations on estimates of sensitivity commonly used in signal detection theory research. This assessment was performed using Monte Carlo simulations. Our research indicated that violating the homogeneity of variance assumption resulted in estimates of sensitivity varying with changes in the response criterion. However, an unequal number of signal and noise trials, which is common in vigilance research, did not impact the estimates of sensitivity. Based upon our findings, caution should be taken with regard to violations of homogeneity of variance. Future research aims to determine the impact of multiple assumption violations on estimates of sensitivity.

scholarly journals The effect of ionic defect interactions on the hydration of yttrium-doped barium zirconate

2021 ◽  
Author(s):  
Sebastian Eisele ◽  
Fabian M. Draber ◽  
Steffen Grieshammer
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Simulations ◽  
First Principles ◽  
Barium Zirconate ◽  
First Principles Calculations ◽  
Defect Interactions ◽  
The Impact ◽  
Ionic Defect

First principles calculations and Monte Carlo simulations reveal the impact of defect interactions on the hydration of barium-zirconate.

scholarly journals A Monte Carlo Determination of Dose and Range Uncertainties for Preclinical Studies with a Proton Beam

Cancers ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1889
Author(s):  
Arthur Bongrand ◽  
Charbel Koumeir ◽  
Daphnée Villoing ◽  
Arnaud Guertin ◽  
Ferid Haddad ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Simulations ◽  
Proton Beam ◽  
Dose Response ◽  
Small Animal ◽  
Absorbed Dose ◽  
Normal Tissue Damage ◽  
Dose Homogeneity ◽  
And Control ◽  
The Impact

Proton therapy (PRT) is an irradiation technique that aims at limiting normal tissue damage while maintaining the tumor response. To study its specificities, the ARRONAX cyclotron is currently developing a preclinical structure compatible with biological experiments. A prerequisite is to identify and control uncertainties on the ARRONAX beamline, which can lead to significant biases in the observed biological results and dose–response relationships, as for any facility. This paper summarizes and quantifies the impact of uncertainty on proton range, absorbed dose, and dose homogeneity in a preclinical context of cell or small animal irradiation on the Bragg curve, using Monte Carlo simulations. All possible sources of uncertainty were investigated and discussed independently. Those with a significant impact were identified, and protocols were established to reduce their consequences. Overall, the uncertainties evaluated were similar to those from clinical practice and are considered compatible with the performance of radiobiological experiments, as well as the study of dose–response relationships on this proton beam. Another conclusion of this study is that Monte Carlo simulations can be used to help build preclinical lines in other setups.

scholarly journals Exoplanet mass estimation for a sample of targets for the Ariel mission

2021 ◽  
Author(s):  
J. R. Barnes ◽  
C. A. Haswell
Keyword(s):  
Radial Velocity ◽  
Input Parameter ◽  
Noise Sources ◽  
Time Commitment ◽  
Low Mass ◽  
Time Required ◽  
Fixed Input ◽  
The Impact ◽  
Quadrature Sampling

AbstractAriel’s ambitious goal to survey a quarter of known exoplanets will transform our knowledge of planetary atmospheres. Masses measured directly with the radial velocity technique are essential for well determined planetary bulk properties. Radial velocity masses will provide important checks of masses derived from atmospheric fits or alternatively can be treated as a fixed input parameter to reduce possible degeneracies in atmospheric retrievals. We quantify the impact of stellar activity on planet mass recovery for the Ariel mission sample using Sun-like spot models scaled for active stars combined with other noise sources. Planets with necessarily well-determined ephemerides will be selected for characterisation with Ariel. With this prior requirement, we simulate the derived planet mass precision as a function of the number of observations for a prospective sample of Ariel targets. We find that quadrature sampling can significantly reduce the time commitment required for follow-up RVs, and is most effective when the planetary RV signature is larger than the RV noise. For a typical radial velocity instrument operating on a 4 m class telescope and achieving 1 m s−1 precision, between ~17% and ~ 37% of the time commitment is spent on the 7% of planets with mass Mp < 10 M⊕. In many low activity cases, the time required is limited by asteroseismic and photon noise. For low mass or faint systems, we can recover masses with the same precision up to ~3 times more quickly with an instrumental precision of ~10 cm s−1.

The electron transport that occurs within wurtzite zinc oxide and the application of stress

MRS Advances ◽  
2017 ◽  
Vol 2 (48) ◽  
pp. 2627-2632 ◽  
Author(s):  
Poppy Siddiqua ◽  
Michael S. Shur ◽  
Stephen K. O’Leary
Keyword(s):  
Monte Carlo ◽  
Zinc Oxide ◽  
Electron Transport ◽  
Velocity Field ◽  
Monte Carlo Simulations ◽  
Significant Role ◽  
Energy Gap ◽  
Device Application ◽  
The Impact

ABSTRACTWe examine how stress has the potential to shape the character of the electron transport that occurs within ZnO. In order to narrow the scope of this analysis, we focus on a determination of the velocity-field characteristics associated with bulk wurtzite ZnO. Monte Carlo simulations of the electron transport are pursued for the purposes of this analysis. Rather than focusing on the impact of stress in of itself, instead we focus on the changes that occur to the energy gap through the application of stress, i.e., energy gap variations provide a proxy for the amount of stress. Our results demonstrate that stress plays a significant role in shaping the form of the velocity-field characteristics associated with ZnO. This dependence could potentially be exploited for device application purposes.

Comparison of Statistical Models For Estimating Intervention Effects Based On Time-To-Recurrent-Event In Stepped Wedge Cluster Randomized Trial Using Open Cohort Design

2021 ◽  
Author(s):  
Shunsuke Oyamada ◽  
Shih-Wei Chiu ◽  
Takuhiro Yamaguchi
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Simulations ◽  
Statistical Models ◽  
Randomised Trial ◽  
Recurrent Event ◽  
Cluster Randomised Trial ◽  
Stepped Wedge ◽  
Intervention Effects ◽  
Cohort Design

Abstract Background: There are currently no methodological studies on the performance of the statistical models for estimating intervention effects based on the time-to-recurrent-event (TTRE) in stepped wedge cluster randomised trial (SWCRT) using an open cohort design. This study aims to address this by evaluating the performance of these statistical models using an open cohort design with the Monte Carlo simulation in various settings and their application using an actual example.Methods: Using Monte Carlo simulations, we evaluated the performance of the existing extended Cox proportional hazard models, i.e., the Andersen-Gill (AG), Prentice-Williams-Peterson Total-Time (PWP-TT), and Prentice-Williams-Peterson Gap-time (PWP-GT) models, using the settings of several event generation models and true intervention effects, with and without stratification by clusters. Unidirectional switching in SWCRT was represented using time-dependent covariates.Results: Using Monte Carlo simulations with the various described settings, the PWP-GT model with stratification by clusters showed the best performance in most settings and reasonable performance in the others. The only situation in which the performance of the PWP-TT model with stratification by clusters was not inferior to that of the PWP-GT model with stratification by clusters was when there was a certain amount of follow-up period, and the timing of the trial entry was random within the trial period, including the follow-up period. The AG model performed well only in a specific setting. By analysing actual examples, it was found that almost all the statistical models suggested that the risk of events during the intervention condition may be somewhat higher than in the control, although the difference was not statistically significant.Conclusions: The PWP-GT model with stratification by clusters had the most reasonable performance when estimating intervention effects based on the TTRE in SWCRT in various settings using an open cohort design.

scholarly journals Impact of thyroglobulin and thyroglobulin antibody assay performance on the differential classification of DTC patients

2021 ◽  
Author(s):  
Lise Schoonen ◽  
Marjolein Neele ◽  
Hans van Toor ◽  
Caroline M J van Kinschot ◽  
Charlotte van Noord ◽  
...  
Keyword(s):  
Poor Correlation ◽  
Antibody Assay ◽  
Thyroglobulin Antibody ◽  
Assay Performance ◽  
Upper Limits ◽  
Antibody Assays ◽  
The Impact ◽  
Storage Temperatures

Abstract Context Measurements of thyroglobulin (Tg) and Tg antibodies are crucial in the follow-up of treated differentiated thyroid cancer (DTC) patients. Inter-assay differences may significantly impact follow-up. Objective The aim of this multicenter study was to explore the impact of Tg and Tg antibody assay performance on the differential classification of DTC patients, as described in national and international guidelines. Design Four commonly used Tg and Tg antibody assays were technically compared to reflect possible effects on patients with DTC follow-up. Storage stability at different storage temperatures was also investigated for LIAISON® and Kryptor assays, as this is an underexposed topic in current literature. Results B.R.A.H.M.S. assays yield approximately 50% lower Tg values over the whole range compared to the DiaSorin and Roche assays investigated. These differences between assays may result in potential misclassification in up to 7% of patients if fixed cut-offs (e.g. 1 ng/mL) are applied. Poor correlation was also observed between the Tg antibody assays, when the method-specific upper limits of normal are used as cut-offs. Storage of Tg and Tg antibodies was possible for three to four weeks at -20 °C and -80 °C. Calibration of the assays, however, was found to be crucial for stable results over time. Conclusions Technical aspects of Tg and Tg antibody assays, including inter-assay differences, calibration and standardization, and cut-off values, may have a significant clinical impact on the follow-up of DTC patients.

Robustness of the a b Signal Detection Theory Model of Decision Making

2007 ◽  
Vol 51 (18) ◽  
pp. 1263-1267
Author(s):  
Ernesto A. Bustamante ◽  
Brittany L. Anderson ◽  
Amy R. Thompson ◽  
James P. Bliss ◽  
Mark W. Scerbo
Keyword(s):  
Decision Making ◽  
Monte Carlo ◽  
Monte Carlo Simulations ◽  
Signal Detection ◽  
Signal Detection Theory ◽  
Classical Model ◽  
Empirical Evaluation ◽  
Detection Theory ◽  
Theory Model ◽  
Extreme Responses

Bustamante, Fallon, and Bliss (2006) showed that the a b Signal Detection Theory (SDT) model was more parsimonious, generalizable, and applicable than the classical SDT model. Additionally, they demonstrated that both models provided statistically equivalent and uncorrelated measures of sensitivity and bias under ideal conditions. The purpose of this research was to show the robustness of the a b model for handling extreme responses. We conducted an empirical evaluation of operators' decision-making and two Monte Carlo simulations. Results from the empirical study showed that the a b model provided equivalent yet independent measures of decision-making accuracy and bias, whereas the classical model failed to provide independent measures in the presence of extreme responses. The Monte Carlo simulations showed a similar trend for the superiority of the a b model. Results from this research provide evidence to support the use of the a b model instead of the classical model.

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