Magnitude Of Different Sources Research Articles

Subject specific angular waist of the optic nerve head nerve fiber layer allows follow up detection of local nerve fiber bundle loss

PurposeTo clarify if frontal plane angular Pigment epithelium central limit‐ Inner limit of the retina Minimal Distance (PIMD) measured with OCT has enough specific angular structure for detection of change of specific angular segments of PIMD over time within glaucoma subjects.MethodsA Topcon OCT‐2000 was used for capture of the 3D representations of the ONH. from one eye of each of totally 13 subjects with early stage primary open angle glaucoma. Altogether, 3 volumes were captured at two occasions within 3 months. PIMD was semi‐automatically segmented in each volume in 500 equally spaced angular segments distributed over 2Pi in the frontal plane.ResultsPlots of the angular distribution of PIMD for all subject revealed specific low angular frequency overlaid with higher intermediate angular frequencies specific for each subject. High angular frequencies appeared similar for all subjects. A fast Fourier transform of the angular PIMD revealed a high to low frequency content ratio, 0.12, consistent for all segmentations of PIMD‐2Pi. The rotational displacment of angular PIMD in the frontal plane among segmentations, volumes and occasions was determined with cross‐correlation. Then, all PIMD‐2Pi were phase adjusted over segments, volumes and occasions. Finally, the rotation of PIMD‐2Pi was adjusted to a standard rotation. This allows comparison of angular segments of PIMD‐2Pi between visits. The magnitude of different sources of variation were estimated with analysis of variance.ConclusionsAngular correction in the frontal plane of recordings of angular PIMD of the ONH allows comparison of angular segments of PIMD‐2Pi. This substantially increases the resolution of of an angular segment of PIMD. The resulting precision suggest that detection of an angular segment of PIMD is associated with better resolution than Humphrey visual field MD.

Analyzing uncertainties and estimating priorities of landscape sensitivity based on expert opinions

The aim of this paper was to present an approach to estimate the priorities of landscape sensitivity criteria and to study uncertainties compounding that process. The data are based on expert judgment priorities of visual landscape sensitivity. The uncertainty model utilized was a Bayesian multi-criteria decision analysis (MCDA) model. The sources of uncertainty were classified into two categories: uncertainty caused by inconsistency of judge-specific assessments, and differences between judges in elicited priorities. In particular, we estimated the relative magnitude of different sources of uncertainty and considered the overall reliability of landscape sensitivity modelling. The results showed that the uncertainties in estimation of landscape sensitivity criteria are large. Further analysis of the two uncertainty sources implied that the number of pairwise comparisons used to assess the landscape sensitivity criteria can be reduced to simplify the assessment task. This was the case since the assessment task involved multiple respondents. However, if there would be only one respondent, the inconsistency of the pairwise comparisons can be an important measure of uncertainty that would help decision makers to avoid over interpretation of the reliability of the priority estimates of the landscape sensitivity estimates.

Thermal energy in dry snow avalanches

Abstract. Avalanches can exhibit many different flow regimes from powder clouds to slush flows. Flow regimes are largely controlled by the properties of the snow released and entrained along the path. Recent investigations showed the temperature of the moving snow to be one of the most important factors controlling the mobility of the flow. The temperature of an avalanche is determined by the temperature of the released and entrained snow but also increases by frictional processes with time. For three artificially released avalanches, we conducted snow profiles along the avalanche track and in the deposition area, which allowed quantifying the temperature of the eroded snow layers. This data set allowed to calculate the thermal balance, from release to deposition, and to discuss the magnitudes of different sources of thermal energy of the avalanches. For the investigated dry avalanches, the thermal energy increase due to friction was mainly depending on the effective elevation drop of the mass of the avalanche with a warming of approximately 0.3 °C per 100 vertical metres. Contrarily, the temperature change due to entrainment varied for the individual avalanches, from −0.08 to 0.3 °C, and depended on the temperature of the snow along the path and the erosion depth. Infrared radiation thermography (IRT) was used to assess the surface temperature before, during and just after the avalanche with high spatial resolution. This data set allowed to identify the warmest temperatures to be located in the deposits of the dense core. Future research directions, especially for the application of IRT, in the field of thermal investigations in avalanche dynamics are discussed.

Variability in Abundance of Temperate Reef Fishes Estimated by Visual Census

Identifying sources of sampling variation and quantifying their magnitude is critical to the interpretation of ecological field data. Yet, most monitoring programs of reef fish populations based on underwater visual censuses (UVC) consider only a few of the factors that may influence fish counts, such as the diver or census methodology. Recent studies, however, have drawn attention to a broader range of processes that introduce variability at different temporal scales. This study analyzes the magnitude of different sources of variation in UVCs of temperate reef fishes off Patagonia (Argentina). The variability associated with time-of-day, tidal state, and time elapsed between censuses (minutes, days, weeks and months) was quantified for censuses conducted on the five most conspicuous and common species: Pinguipes brasilianus, Pseudopercis semifasciata, Sebastes oculatus, Acanthistius patachonicus and Nemadactylus bergi. Variance components corresponding to spatial heterogeneity and to the different temporal scales were estimated using nested random models. The levels of variability estimated for the different species were related to their life history attributes and behavior. Neither time-of-day nor tidal state had a significant effect on counts, except for the influence of tide on P. brasilianus. Spatial heterogeneity was the dominant source of variance in all but one species. Among the temporal scales, the intra-annual variation was the highest component for most species due to marked seasonal fluctuations in abundance, followed by the weekly and the instantaneous variation; the daily component was not significant. The variability between censuses conducted at different tidal levels and time-of-day was similar in magnitude to the instantaneous variation, reinforcing the conclusion that stochastic variation at very short time scales is non-negligible and should be taken into account in the design of monitoring programs and experiments. The present study provides baseline information to design and interpret results from visual census programs in temperate reefs.

FDI, Trade, and Product Innovation: Theory and Evidence

This article investigates the relationship between foreign direct investment (FDI, including outward FDI and inward FDI), imports and exports, and product innovation. Our theoretical model predicts that inward FDI, outward FDI, imports, and exports have positive influences on firm innovative activities, which would evaluate the effects of the relative magnitude of different sources on innovation. The empirical results based on the 2003 First Taiwan Technological Innovation Survey confirm three of the proposed hypotheses for the entire sample. However, when focusing on the manufacturing sector, outward FDI, inward FDI, imports, and exports all exhibit strongly positive effects on the determination of conducting product innovation (i.e., the four hypotheses are verified). A consistent trend is that outward FDI has the largest effect on innovation, regardless of the measurement of product innovation and the division of the entire sample, which may imply that in Taiwan a positive effect of “deindustrialization” is to innovate more.

Influence of instantaneous variation on estimates of coral reef fish populations and communities

The magnitude of different sources of variation in coral reef fish abundance data needs to be known if temporal changes in population and community data are to be correctly estimated. A particularly important missing component of the variability is the 'instantaneous' change in fish, largely caused by the interaction between fish movement and observer recognition. This variation occurs at a time scale less than that influenced by the focus of previous studies, including time of day, tides, migration, or birth and death processes. Without this measure of variance, estimates of temporal change are confounded. To determine the magnitude of this instantaneous variance, belt-transect visual counts of damselfish, surgeonfish, and parrotfish were conducted during a short interval at midday during neap tides over consecutive days in the calm season and compared to similar samples in 1992 and 2003. Within-site, or our estimate of instantaneous variation, was the greatest source of variability for the whole assemblage and for the surgeonfish/parrotfish group but not for damselfish. Direct between-year comparisons produced estimates of population change over time that were twice as high as those derived by an indirect method where the instantaneous spatial component was subtracted from the total variation. Because the inherent spatial component of variability makes it difficult to detect site change over time, we recommend sampling designs that use random sampling and have greater statistical power to detect change. Furthermore, aggregate metrics, such as numbers of species or density at the family, community, or the functional group, will have greater potential to detect change for sample sizes typical of coral reef studies. Otherwise, when life history traits and species level change are important, high replication will be required.

The influence of instantaneous variation on estimates of coral reef fish populations and communities

The magnitude of different sources of variation in coral reef fish abundance data needs to be known if temporal changes in population and community data are to be correctly estimated. A particularly important missing component of the variability is the 'instantaneous' change in fish, largely caused by the interaction between fish movement and observer recognition. This variation occurs at a time scale less than that influenced by the focus of previous studies, including time of day, tides, migration, or birth and death processes. Without this measure of variance, estimates of temporal change are confounded. To determine the magnitude of this instantaneous variance, belt-transect visual counts of damselfish, surgeonfish, and parrotfish were conducted during a short interval at midday during neap tides over consecutive days in the calm season and compared to similar samples in 1992 and 2003. Within-site, or our estimate of instantaneous variation, was the greatest source of variability for the whole assemblage and for the surgeonfish/parrotfish group but not for damselfish. Direct between-year comparisons produced estimates of population change over time that were twice as high as those derived by an indirect method where the instantaneous spatial component was subtracted from the total variation. Because the inherent spatial component of variability makes it difficult to detect site change over time, we recommend sampling designs that use random sampling and have greater statistical power to detect change. Furthermore, aggregate metrics, such as numbers of species or density at the family, community, or the functional group, will have greater potential to detect change for sample sizes typical of coral reef studies. Otherwise, when life history traits and species level change are important, high replication will be required.

Sources of variation in Affymetrix microarray experiments

BackgroundA typical microarray experiment has many sources of variation which can be attributed to biological and technical causes. Identifying sources of variation and assessing their magnitude, among other factors, are important for optimal experimental design. The objectives of this study were: (1) to estimate relative magnitudes of different sources of variation and (2) to evaluate agreement between biological and technical replicates.ResultsWe performed a microarray experiment using a total of 24 Affymetrix GeneChip® arrays. The study included 4th mammary gland samples from eight 21-day-old Sprague Dawley CD female rats exposed to genistein (soy isoflavone). RNA samples from each rat were split to assess variation arising at labeling and hybridization steps. A general linear model was used to estimate variance components. Pearson correlations were computed to evaluate agreement between technical and biological replicates.ConclusionThe greatest source of variation was biological variation, followed by residual error, and finally variation due to labeling when *.cel files were processed with dChip and RMA image processing algorithms. When MAS 5.0 or GCRMA-EB were used, the greatest source of variation was residual error, followed by biology and labeling. Correlations between technical replicates were consistently higher than between biological replicates.

Measurement of aortic blood flow by Doppler echocardiography: Temporal, technician, and reader variability in normal subjects and the application of generalizability theory in clinical research

Although Doppler echocardiographic measurements of aortic flow have been found to correlate with stroke volume, the reliability of this technique is unknown. The purpose of this study was to measure the reliability of Doppler estimates of cardiac output by identifying and estimating the magnitude of different sources of error. We measured the reliability of Doppler estimates of cardiac output by identifying the magnitude of sources of error in 11 subjects with studies performed by two technicians and read by two readers. Analysis with generalizability theory demonstrated that the largest portion of the total variance was from differences among patients, with a smaller contribution due to day-to-day variability. Variability due to technician was low for continuous wave Doppler (2.0%), but high for pulsed wave (23.2%). Thus continuous wave, but not pulsed wave Doppler measurements, can be used to detect serial changes in cardiac output due to an intervention.

Peripheral Arterial Occlusive Disease in General Practice: The Reproducibility of the Ankle-Arm Systolic Pressure Ratio

One of the non-invasive techniques used in the diagnosis of patients with peripheral arterial occlusive disease is the measurement of the Ankle-Arm Systolic Pressure Ratio ("AA-Ratio"). The magnitude of different sources of measurement variation, relevant to clinical practice as well as multi-observer studies, was estimated from a random effects analysis of variance model. Thirty-five GPs and 24 practice assistants performed 503 AA-Ratio measurements on nine patients over a period of nine weeks, using pocket Doppler devices. When the AA-Ratio is used for diagnostic purposes, a 95% prediction interval consisting of the measured value +/- 15-20% AA-Ratio has to be taken into account. Furthermore, when the AA-Ratio is used in the follow-up of a patient with vascular disease, the difference between two subsequent measurements has to be at least 15.6-19.0% AA-Ratio to have an 80% certainty that this difference is not due to (intra-observer) measurement error.