Total Standard Deviation Research Articles

Cognitive decline in the elderly: an analysis of population heterogeneity

studies of cognitive ageing at the group level suggest that age is associated with cognitive decline; however, there may be individual differences such that not all older adults will experience cognitive decline. to evaluate patterns of cognitive decline in a cohort of older adults initially free of dementia. elderly Catholic clergy members participating in the Religious Orders Study were followed for up to 15 years. Cognitive performance was assessed annually. performance on a composite global measure of cognition was analysed using random effects models for baseline performance and change over time. A profile mixture component was used to identify subgroups with different cognitive trajectories over the study period. from a sample of 1,049 participants (mean age 75 years), three subgroups were identified based on the distribution of baseline performance and change over time. The majority (65%) of participants belonged to a slow decline class that did not experience substantial cognitive decline over the observation period [-0.04 baseline total sample standard deviation (SD) units/year]. About 27% experienced moderate decline (-0.19 SD/year), and 8% belonged to a class experiencing rapid decline (-0.57 SD/year). A subsample analysis revealed that when substantial cognitive decline does occur, the magnitude and rate of decline is correlated with neuropathological processes. in this sample, the most common pattern of cognitive decline is extremely slow, perceptible on a time scale measured by decades, not years. While in need of cross validation, these findings suggest that cognitive changes associated with ageing may be minimal and emphasise the importance of understanding the full range of age-related pathologies that may diminish brain function.

Standardized Combined Outcome Index as an Instrument for Monitoring Performance After Pulmonary Resection

Modern healthcare systems demand more transparent and accurate monitoring of clinical performance with the purpose to improve standards of care in a cost-effective way. Outcomes, such as mortality, are still the most widely used quality indicators in our specialty. However, previous studies have shown that mortality alone does not reflect performance accurately in our specialty. Ideally, multiple risk-adjusted outcomes should be used for a more comprehensive assessment. The objective of this analysis was to develop and use an index combining multiple risk-adjusted outcomes to track down the performance of our thoracic surgery unit over time. In all, 511 major lung resections (465 lobectomies, 46 pneumonectomies) performed from January 2005 through September 2010 were analyzed. Four risk-adjusted outcomes were considered: 30 days or in-hospital mortality, cardiopulmonary morbidity, unplanned/emergency intensive care unit admission, and prolonged length of stay (more than 14 days, prolonged hospital stay). Risk adjustment was performed using published regression models. Each indicator was converted into its opposite (ie, mortality rate to survival rate) so that higher scores reflected better performance. Moreover, to account for differences in measurement scales, the standardized outcomes were rescaled according to their mean total standard deviations. Finally, the individual rescaled indicators of each year were summed to generate a combined outcome index. Mean cumulative observed mortality, morbidity, unplanned intensive care unit, and prolonged hospital stay rates were 1.8%, 23%, 6.6%, and 7.4%, respectively. The combined outcome index scores showed a progressive improvement of performance during the study period, progressing from -3.48 in 2005 to 2.87 in 2009. The combined outcome index was also used prospectively in a variable life-adjusted display chart to track down trends of practice variation in the last 6 months. The present analysis is proposed as a methodologic template for developing a risk-adjusted index combining four different outcomes. It aims at overcoming inherent limitations of outcomes when used individually for performance assessment. This or similar combined indexes may be effective instruments of internal clinical audit and could be incorporated along with process indicators in composite performance scores to more comprehensively evaluate the postoperative domain of our practice.

Quantification of uncertainty of experimental measurement in leaching test on cement-based materials

When mineral wastes are reused in construction materials, a current practice is to evaluate their environmental impact using standard leaching test. However, due to the uncertainty of the measurement, it is usually quite difficult to estimate the pollutant potential compared to other materials or threshold limits. The aim of this paper is to give a quantitative evaluation of the uncertainty of leachate concentrations of cement-based materials, as a function of the number of test performed. The relative standard deviations and relative confidence intervals are determined using experimental data in order to give a global evaluation of the uncertainty of leachate concentrations (determination of total relative standard deviation). Various combinations were realized in order to point out the origin of large dispersion of the results (determination of relative standard deviation linked to analytical measured and to leaching procedure), generalisation was suggested and the results were compared to literature. An actual example was given about the introduction of residue (meat and bone meal bottom ash – MBM-BA) in mortar, leaching tests were carried out on various samples with and without residue MBM-BA. In conclusion large dispersion were observed and mainly due to heterogeneity of materials. So heightened attention needed to analyse leaching result on cement-based materials and further more other tests (e.g. ecotoxicology) should be performed to evaluate the environmental effect of these materials.

Ground-Motion Simulations for the 1980 M 6.9 Irpinia Earthquake (Southern Italy) and Scenario Events

In this paper, we adopt three ground-motion simulation techniques (the stochastic finite-fault simulation code from Motazedian and Atkinson, 2005; the hybrid deterministic-stochastic approach with approximated Green's functions from Pacor et al., 2005; and the broadband hybrid integral-composite technique with full-wavefield Green's functions from Gallovic and Brokesova, 2007), with the aim of investigating the different performances in near-fault strong-motion modeling andpredictionfrompastandfutureevents.Thetestcaseisthe1980M6.9Irpiniaearth- quake, the strongest event recorded in Italy in the last 30 years. First, we simulate the recorded strong-motion data and validate the model parameters by computing spectral accelerationandpeakamplituderesidualdistributions.Thevalidatedmodelisthenused to investigate the influence of site effects and to compute synthetic ground motions around the fault. Afterward, we simulate the expected ground motions from scenario events on the Irpinia fault, varying the hypocenters, the rupture velocities, and the slip distributions. We compare the median ground motions and related standard deviations from all scenario events with empirical ground-motion prediction equations (GMPEs). The synthetic median values are included in the median 1 standard deviation of the considered GMPEs. Synthetic peak ground accelerations show median values smaller and with a faster decay with distance than the empirical ones. The synthetics total stan- dard deviation is of the same order or smaller than the empirical one, and it shows considerable differences from one simulation technique to another. We decomposed the total standard deviation into its between-scenario and within-scenario components. The larger contribution to the total sigma comes from the latter, while the former is found to be smaller and in good agreement with empirical interevent variability. Online Material: Comparison of observed and simulated waveforms and spectra.

A sub‐1V supply CMOS voltage reference generator

SUMMARYAn integrated sub‐1V voltage reference generator, designed in standard 90‐nm CMOS technology, is presented in this paper. The proposed voltage reference circuit consists of a conventional bandgap core based on the use of p‐n‐p substrate vertical bipolar devices and a voltage‐to‐current converter. The former produces a current with a positive temperature coefficient (TC), whereas the latter translates the emitter‐base voltage of the core p‐n‐p bipolar device to a current with a negative TC. The circuit includes two operational amplifiers with a rail‐to‐rail output stage for enabling stable and robust operation overall process and supply voltage variations while it employs a total resistance of less than 600 K Ω. Detailed analysis is presented to demonstrate that the proposed circuit technique enables die area reduction. The presented voltage reference generator exhibits a PSRR of 52.78 dB and a TC of 23.66ppm/∘C in the range of − 40 and 125∘C at the typical corner case at 1 V. The output reference voltage of 510 mV achieves a total absolute variation of ± 3.3% overall process and supply voltage variations and a total standard deviation, σ, of 4.5 mV, respectively, in the temperature range of − 36 and 125∘C. Copyright © 2011 John Wiley & Sons, Ltd.

Measuring mesiodistal width of impacted maxillary canines

Precise, three-dimensional localization of impacted maxillary canines is central to their clinical management. Predicting precisely the crown's mesiodistal width is paramount in planning orthodontic treatment. The aim of this study was to verify the exact mesiodistal width of impacted canines via MSCT (multislice spiral computed tomography) examinations. 3D MSCT images from 17 patients with a total of 24 impacted maxillary canines were taken to obtain the largest mesiodistal diameter using mesial and distal contact points. All existing maxillary canines were included in this study. Mesiodistal tooth width was also determined using callipers on a plaster model after canine eruption. Each measurement was taken twice by 3 observers after a 10-day interval. Statistical analysis entailed calculating and comparing the systematic error, intrarater and interrater standard deviations (Deming regression and ANOVA with random effects). Comparison of the different methods revealed good agreement between the pre-eruption and post-eruption values regarding the canine's mesiodistal width. Total standard deviation was 0.16 mm for values obtained from MSCT measurements and 0.12 mm for those taken with callipers. For both methods intrarater measurement error differed by a factor of 2 (repeatability; model versus MSCT: 0.07 mm versus 0.12 mm), while interrater deviation did not differ significantly (reproducibility; model versus MSCT: 0.10 mm versus 0.10 mm). The reproducibility of our measurements whether taken on the model or with CT was below biological variability. The volumetric data from an MSCT system gives highly accurate information on the mesiodistal width of displaced canines.

Effects of postprandial state and mesenteric blood flow on the repeatability of MR elastography in asymptomatic subjects

To determine the repeatability of stiffness measurements in the liver using MR elastography (MRE) during the fasted and fed states. MRE has gained increased recognition as a noninvasive method to quantify fibrotic changes in the liver. It is well known that eating increases splanchnic blood flow, and fasting status of patients has been recognized as a factor that may affect hepatic stiffness measured with MRE. Hepatic MRE stiffness and flow through the superior mesenteric vein (SMV) were measured in 12 healthy subjects in fasted and fed states, and measurements were repeated 5 weeks later. A linear mixed effects model was used to estimate the sources of variability in the data, which included day (exams on different days) and subject. Sources were combined to calculate the overall standard deviation of a single MRE measurement. The total within-subject standard deviation of an MRE exam is 8.5% (standard error [SE] = 1.7%) or 9.0% (SE = 1.8%) for fasted and fed states, respectively. No significant differences between fasted/fed state stiffness and no correlation between hepatic stiffness and SMV flow were observed. As seen in this smaller population, healthy subjects scanned in a known fasted or fed state provide repeatable stiffness estimates with no relationship to SMV flow.

Determination of Ketone Bodies in Blood by Headspace Gas Chromatography-Mass Spectrometry

A gas chromatography-mass spectrometry (GC-MS) method for determination of ketone bodies (β-hydroxybutyrate, acetone, and acetoacetate) in blood is presented. The method is based on enzymatic oxidation of D-β-hydroxybutyrate to acetoacetate, followed by decarboxylation to acetone, which was quantified by the use of headspace GC-MS using acetone-(13)C(3) as an internal standard. The developed method was found to have intra- and total interday relative standard deviations < 10% for acetone+acetoacetate levels (∼25 to 8300 μM) and D-β-hydroxybutyrate levels (∼30 to 16500 μM). Recovery values varied from 98 to 107%, demonstrating the suitability of the method for measuring ketone bodies over a wide concentration range. The method has been applied to cases in which ketoacidosis was suspected as the cause of death in diabetics or chronic alcoholics, as well as to cases in which another cause of death was identified.

Validity and reliability of the ‘good perioperative nursing care scale’ for Turkish patients and nurses

To test the validity and reliability of the Turkish version of Good Perioperative Nursing Care Scale for nurses and patients. The nursing care in operating departments has an important role in modern health care and therefore more research concerning perioperative care quality is needed and the development of a measurement tool is necessary. The study was designed as a cross-sectional survey. The research population was 346 patients who had surgery and 159 operating room nurses who worked at 11 hospitals. The GPNCS contains 32 items. The items on the nurses' form were changed as little as possible to create the form for patients to be able to directly compare them. To determine the tool's language equivalency/adaptation of the questionnaire for both nurses and patients, the tool was translated into Turkish then retranslated, and a pilot study was conducted. The total scale's total mean score and standard deviation for nurses was determined to be 113·23 (SD 2·13) and for patients was 128·23 (SD 1·27). To test the scale's stability over time, a test-retest was conducted and the results showed a strong confirmatory correlation. The GPNCS was determined to be a tool that had indicators of being adequate, reliable and valid for the Turkish population. This study highlighted the importance of comparing the quality and effectiveness of nursing care in different operating departments. It is recommended that it be used to determine the quality of perioperative nursing care in Turkey.

SU‐EE‐A3‐01: Quantifying Anatomical Variability in Regressing Tumors during Active Breath Hold Radiotherapy: A Modal Dominant Deformations Approach

Purpose: To quantify and classify interfraction geometric variability of lung tumors for independent analysis. Method and Materials: 14 research subjects (15 tumors) underwent three weekly repeat breath hold (BH) scans at end of normal inspiration. Images were deformably registered to the planning scan, and the gross tumor volume (GTV), ipsilateral (IL), and contralateral (CL) lungs delineated on the planning scan were propagated to all images. Principal component analysis (PCA) was used to generate two statistical shape models of the structures for each patient: a week to week (W2W) model using only one scan per week and an all scans model using all available images per patient. Principal dominant modes were classified by modal volume and position change and time trend into six discrete classes representing tumor regression (isotropic and anisotropic) or breath hold/lung volume variability. Three novel normalized modal variability indices (mean mode volume, total variances, total dominant variances, concordance variance, and concordance standard deviation) were developed to quantify the BH variability using the W2W and all scans models. Results: The mean BH variability indices were 1.03%, 13.57%, and 7.3%, representing the percentage of mean shape, total variance, and modes concordances respectively, due to BH reproducibility. 46 dominant modes were identified for all patients in total. 23, 8, 4, 4, 1, and 6 modes belonged to classes 1–6, respectively. Classes 1–2 are rigid shifts associated with BH or error, while classes 3–6 represented deformation due to tumor regression. Modal GTV positional shift was found to correlate with CL volume change in 10/15 subjects. Conclusion: BH variability indices were used to quantify BH. A novel modal classification system was developed to classify geometric variability by type. Modal GTV positional shift correlation with CL volume is likely due to altered lung function in the IL.Supported by NIH R01 CA116249.

Molecular Structure of Trichloroethenylgermane, CH2═CH−GeCl3, as Studied by Gas-Phase Electron Diffraction. Experimental Determination of the Barrier of Internal Rotation of the Trichlorogermyl Group Supplemented with Quantum Chemical Calculations on CH2═CH−MX3 (M = C, Si, Ge, Sn, and X = H, Cl)

The molecular structure of trichloroethenylgermane, CH(2)=CH-GeCl(3), has been determined by electron diffraction and supported by quantum chemical calculations on CH(2)=CH-MX(3) (M = C, Si, Ge, Sn and X = H, Cl). An equilibrium syn conformation with C(s) symmetry is obtained both experimentally and theoretically where one of the Ge-Cl bonds eclipses the C=C bond. The barrier of internal rotation about the C-Ge bond is determined to be V(3) = 5.3(7) kJ mol(-1) using a dynamic model to simulate the internal motion. The most important structure parameters (estimated r(e)/A and angle/degree) are: r(C-Ge) = 1.911(5), r(C=C) = 1.345(5), r(Ge-Cl7) = 2.122(2), <C=C-Ge = 120.4(5), <C-Ge-Cl7 = 111.0(2), and <Cl7-Ge-Cl8) = 109.4(5) where the Cl7 atom is in the C=C-Ge plane and the Cl8 atom is out of the C=C-Ge plane. Uncertainties are estimated total standard deviations (sigma(tot)) given as: sigma(tot) = [sigma(2)(scale) + (2sigma(lsq))(2)](1/2) for bond lengths where sigma(scale) = 0.001r and sigma(lsq) is the least-squares standard deviation using a diagonal weight matrix and sigma(tot) = 2sigma(lsq) for the other parameters. The assignment of some of the fundamental frequencies has been discussed. The internal agreement between the calculated molecular geometry obtained from B3LYP and MP2(F) using the cc-pVQZ basis set and to the experimental geometry is not good, whereas the molecular geometry obtained from a CCSD/cc-pVTZ calculation is in very good agreement with experimental geometry. This investigation shows that the gas electron-diffraction method is capable of determining the rotational barrier for small suitable molecules with acceptable accuracy.

Ground motion scenarios for the 1997 Colfiorito, central Italy, earthquake

In this paper we report the results of several investigations aimed at evaluating ground motion scenarios for the September 26th, 1997 Colfiorito earthquake (Mw 6.0, 09:40 UTC). We model the observed variability of ground motions through synthetic scenarios which simulate an earthquake rupture propagating at constant rupture velocity (2.7 km/s) and the inferred directivity. We discuss the variability of kinematic source parameters, such as the nucleation position and the rupture velocity, and how it influences the predicted ground motions and it does not account for the total standard deviation of the empirical predictive model valid for the region. Finally, we used the results from the scenario studies for the Colfiorito earthquake to integrate the probabilistic and deterministic approaches for seismic hazard assessment.

Assessment of a Measurement System Using Repeat Measurements of Failing Units

ABSTRACT Inspection systems measure every part produced. If the measurement is outside of the inspection limits, then that part is measured again. To assess the quality of these measurement systems, traditionally gauge repeatability and reproducibility (R&R) studies are preformed. Instead of performing a gauge R&R study, we present a method of assessing these measurement systems with operational data from an inspection system. Using the inspection data, we provide a justification for the pooled variance of the measured values for each part that has two measurements. The bias and variance of this analysis of variance (ANOVA) estimator are derived using properties of the truncated normal distribution. We show that the ANOVA estimator has a relatively small bias and high efficiency when compared with the maximum likelihood estimator for most common values of γ or GRR%, which is the measurement system standard deviation divided by total inspection system standard deviation.

Towards consensus on how to measure neutral genetic diversity?

Towards consensus on how to measure neutral genetic diversity?

New and Improved Methods to Characterize Glycemic Variability Using Continuous Glucose Monitoring

Glycemic variability is a possible risk factor for development of complications from diabetes. Numerous methods have been used to characterize glycemic variability. We propose several new methods to characterize glycemic variability. We evaluated these methods empirically and theoretically and compared them with previous methods. We describe (1) extension and generalization of the mean amplitude of glycemic excursion (MAGE), i.e., "within day variability," (2) extension and generalization of the mean of daily differences (MODD), i.e., the "between day-within time points variability," (3) "between daily means variability," (4) "between time points variability" of the glucose profile averaged over several days, (5) "within series variability" for a time segment of any arbitrary length, (6) new measures of the stability of the daily glycemic patterns, (7) new types of graphical displays, including within day variability, between day-within time points variability, and between daily means variability versus total variability, and between daily means variability versus within day variability, and (8) new methods to evaluate whether within series and between day-within time points variability fluctuate systematically by time of day. We examined the new measures in relation to previous measures of glycemic variability using correlation analysis on a clinical dataset for 85 subjects. MAGE, MODD, and continuous overall net glycemic action (CONGA(n)) are directly proportional to total standard deviation (SD). MAGE is highly correlated with both total SD and within day variability but weakly correlated with measures of between day variability. MODD is highly correlated with between day-within time points variability and total SD but weakly correlated with measures of within day variability. We provide a systematic, logical framework to characterize multiple aspects of glycemic variability and have implemented a simple, practical computing format. This approach can help clinical researchers and clinicians identify the major sources of variability for any given patient and monitor responses to interventions.

Genetic determination of the onset of heat stress on daily milk production in the US Holstein cattle

Existence of individual variation in the onset of heat stress for daily milk yield of dairy cows was assessed. Data included 353,376 test-day records of 38,383 first-parity Holsteins from a random sample of US herds. Three hierarchical models were investigated. Model 1 inferred the value of a temperature-humidity index (THI) at which mean yield began to decline as well as the extent of that decline. Model 2 assumed individual variation in yield decline beyond a common THI threshold. Model 3 additionally assumed individual variation for the onset of heat stress. Deviance information criteria indicated the superiority of model 3 over model 2. For model 2, genetic correlation between milk yield in the absence of heat stress and the THI threshold for heat stress was −0.4 (0.11) [marginal posterior mean (marginal posterior standard deviation)]. For model 3, genetic correlations were −0.53 (0.05) between milk yield and THI threshold and −0.62 (0.08) between milk yield and yield decay beyond the THI threshold. Total standard deviation (sum of additive genetic and permanent environmental standard deviations) for the THI threshold was 3.95 (0.06), and more than half of that variation had an additive genetic origin [56% (5%)]. Because of the high genetic correlation [0.95 (0.03)] between yield decay and THI threshold with model 3, using only one of them as a selection criterion for heat tolerance would modify the other in the desired direction.

An Evaluating Model of Photovoltaic Power Output Variations for an Energy System Planning in an Urban Area

AbstractThis paper presents a mathematical model to evaluate the power output variations from photovoltaic systems (PV) in collaboration with an energy system planning in an urban area, and applied the model to a demonstrating energy system. The evaluating model is developed from per‐floor area PV power output variations on the basis of the past 1 year of actual solar insolation. The evaluation of the power variations is represented in terms of a per‐floor area standard deviation curve. In case of considering two alternatives, battery‐less and battery‐installed PV systems, a correlative coefficient curve is calculated, then a total standard deviation curve representing the total PV power variations can be formulated on the basis of a random variable (RV) model. The model is applied as a tool to evaluate the power variation in an energy system. The energy system planning demonstration approaches the optimal planning by minimizing total cost under CO2 emission reduction and the power variation constraints. The results show the impacts of the constraint of power variation that limit the installation of PV system. The constraint results the increase of the proportion of PV system with battery installation against PV system without battery installation. Consequently, the constraint also degrades the maximum potential of the entire system to reduce CO2 emission corresponding to the decrease of PV system. © 2009 Institute of Electrical Engineers of Japan. Published by John Wiley &amp; Sons, Inc.

A randomized controlled trial of a controlled breathing protocol on heart rate variability following myocardial infarction or coronary artery bypass graft surgery

Objectives: To determine whether a controlled breathing programme increases heart rate variability following an acute myocardial infarction and/or coronary artery bypass graft surgery. Rationale: Heart rate variability is reduced following a myocardial infarction, and low heart rate variability is associated with a high mortality risk. By changing tidal volume and rate of breathing, individuals can alter beat-to-beat heart rate variability. It is hypothesized that heart rate increases with inspiration and decreases with exhalation, and that deep slow breathing enhances respiratory sinus arrhythmia, increasing heart rate variability. Design: Randomized controlled trial. Setting: Cardiac rehabilitation programme at a large academic medical centre in North Texas. Subjects: From 2001 to 2005, 44 patients, age 46—65 years, who had a myocardial infarction and/or undergone coronary artery bypass graft surgery 1—8 weeks previously and were referred to the Cardiac Rehabilitation Program. Intervention: Patients were randomized to either usual cardiac rehabilitation or cardiac rehabilitation with controlled breathing (6 breaths/min for 10 minutes twice daily during the eight-week treatment period). Main measures: Weekly measurements of total power and standard deviation of the mean normal to normal RR interval (SDNN), and fortnightly measurements of respiratory sinus arrhythmia were taken using Biocom Technologies Heart Rhythm Scanner and Tracker software. Results: No significant difference in change were seen between groups in SDNN (P = 0.3984), baseline respiratory sinus arrhythmia (P = 0.6556) or total power (P = 0.6184). Conclusion: Results suggest participation in the controlled breathing programme offered no additional benefit in increasing heart rate variability following myocardial infarction or coronary artery bypass graft surgery. However, 77% of study patients were on heart rate-lowering medications, which may have masked changes in heart rate variability.

The Impact of Prostate and Seminal Vesicle Motion during Prostate Cancer Radiotherapy on Planning Margins

The seminal vesicles (SVs) form part of the target in the radiotherapy (RT) treatment of prostate cancer, either because of their significant risk of involvement in locally advanced disease or because of overt clinical invasion. While prostate motion and appropriate margins have been documented, there is little information on SV motion. Movement of the SVs compared to the prostate, if uncorrected, can lead to geometrical target miss. The aim of this prospective study was to assess and compare SV motion with respect to prostate motion to ascertain the appropriate margins for each target. The study population consisted of 10 patients with locally advanced prostate cancer and considered to be at risk of SV invasion or with clinically T3b disease. The average age was 71 years, with average PSA and median Gleason scores of 10 μg/L and 8, respectively, and T stages from T2a to T3b. Following consent, 5 gold seeds were inserted trans-rectally into each patient. Of the 5 seeds, 3 were inserted into the prostate (right base, left mid gland, right apex), and 1 into each of the left and right SVs. All patients were treated to a dose of 78 Gy in 39 fractions with IMRT. Daily orthogonal 2D Electronic Portal Images (EPIs) were taken of each patient in treatment position prior to RT. Elekta I-View GT template matching software was used to verify EPIs with the reference image (CT-derived Digitally Reconstructed Radiograph). Online verification was performed for each fraction using the 3 prostate seeds. Matches of the left and right SV seeds were performed offline for each of the 39 fractions of all 10 patients. The total standard deviation (SD) of systematic errors (∑tot) and SD of random errors (σtot) were calculated, and the CTV-PTV margins for both the prostate and SVs were generated using a previously published formula (2.5∑tot + 0.7σtot). The average correctional shifts (with ranges) for the prostate and SVs in mm were: Prostate: Right-Left (RL) 0.9 (−4.6 to 6.5), Superior-Inferior (SI) −0.3 (−9.8 to 6.3), Anterior-Posterior (AP) −0.3 (−8.6 to 9.1) Left SV: RL 0.9 (−10.5 to 10.4), SI -1.4 (−10.8 to 8.8), AP -2.2 (−16.6 to 8.3) Right SV: RL 0.1 (−9.0 to 5.3), SI -1.1 (−9.4 to 6.3), AP -2.1 (−13.2 to 10.9). Required CTV-PTV margins in mm in the RL, SI and AP planes were: Prostate: 4.2, 6.1, 3.3 Left SV: 9.1, 5.4, 6.9 Right SV: 5.5, 5.4, 6.7. Positional variation of the prostate and SVs was observed during RT. We have found that SV motion is greater in the RL and AP directions than prostate motion. Consequently, the calculated PTV margins for the SVs were greater than the prostate margins, indicating that differential margins may be warranted.

Evaluating methods for estimating process and observation error variances in statistical catch-at-age analysis

Statistical catch-at-age analysis (SCAA) allows analysts to explicitly account for process and observation errors in their stock assessment models. The variances associated with these errors are important because they weight the different data and error sources during the model fitting process. Misspecification of the error variances can lead to biased estimates of key management quantities. Values for the error variances commonly are obtained separately from SCAA and treated as known in the subsequent analysis. The advantages of estimating the error variances within SCAA include that all of the data available to the analysis can be synthesized to obtain the variance estimates and, with some methods, uncertainty surrounding the variance estimates can be quantified. We evaluated alternative approaches for estimating log catchability (process error) and log total catch (observation error) standard deviations within SCAA using Monte Carlo simulations: an ad hoc approach that tunes the model predicted log total catch standard deviation to match a prior value, and a Bayesian approach using either strongly or weakly informative priors for log catchability standard deviation. The Bayesian approach using strongly informative priors outperformed the other approaches in estimating the log total catch and log catchability standard deviations, as well as estimating biomass in the last year of analysis. The ad hoc approach produced misleading results which could indicate that total variance (i.e., process error variance plus observation error variance) was well estimated when, in fact, total variance was underestimated.