The distribution of McKay's approximation for the coefficient of variation

McKay's approximation for the coefficient of variation is type II noncentral beta distributed and asymptotically normal with mean n - 1 and variance smaller than 2(n - 1)

A resampling test for principal component analysis of genotype-by-environment interaction

In crop science, genotype-by-environment interaction is oftenexplored using the "genotype main effects and genotype-by-environmentinteraction effects" (GGE) model. Using this model, a singularvalue decomposition is performed on the matrix of residuals from a fit ofa linear model with main effects of environments. Provided that errorsare independent, normally distributed and homoscedastic, the significanceof the multiplicative terms of the GGE model can be tested usingresampling methods. The GGE method is closely related to principalcomponent analysis (PCA). The present paper describes i) the GGEmodel, ii) the simple parametric bootstrap method for testing multiplicativegenotype-by-environment interaction terms, and iii) how thisresampling method can also be used for testing principal components inPC

The 22 GHz radio-aeronomy receiver at Onsala Space Observatory

We present a radiometer system for regular long-term measurements of water vapour in the middle atmosphere. To be able to do continuous and long-term measurements a simple, robust, reliable and automatic system is needed. Our system therefore is based on a stable, uncooled, HEMT amplifier frontend and on a digital spectrometer backend. In order to minimise reflections in the frontend transmission line, which distort the signal due to standing waves, we have designed a corrugated receiver horn, which combines good characteristics (low return loss and sidelobes) and narrow beamwidth to simplify the receiver optics. In order to make the radiometer system as simple as possible, we use the sky as the calibration cold load. This is possible since we use the observed brightness temperatures of an already existing broadband dual-channel 21.0/31.4-GHz radiometer, at the observation site, to estimate the brightness temperature of the sky at . However, we have developed a calibration method, which makes it possible to estimate the sky brightness temperature even if we cannot use the dual-channel radiometer. Despite new measurements, which became available in recent years, the determination of middle atmospheric water vapour distribution still remains a challenge due to the fact that there is a large dispersion among the different measurement methods and data sets, which are obtained on a sparse and sporadic basis. This is the reason why several instruments similar to ours currently are developed in Europe

Longest continous ground-based measurements of mesospheric CO

The longest continuous series of ground-based measurements of mesospheric CO is presented. The continuous data cover the period September 2000 to September 2002. Sporadic measurements from 1988 and 1989 are also reported. The results show a large CO accumulation in the winter mesosphere, which is consistent with generally accepted ideas about the seasonally-varying mean meridional circulation. Comparison of the observations with simulations by the Whole Atmosphere Community Climate Model (WACCM) indicate that the model can reproduce the observed seasonal cycle as well as much of its variability, although calculated columns amounts are smaller than the largest values seen in the data

Hvor mange kompromiser har økologien råd til? Ægproduktion som eksempel

Mens konventionelt landbrug blot forpligter sig til at producere, hvad efterspørgslen dikterer, påtager økologisk landbrug sig et etisk ansvar for at producere i overensstemmelse med standarder, der er afledt af økologiens egne værdier og prioriteringer. Dette forhold er formentlig forklaringen på den bredt udtrykte sympati, der hersker for økologien. Men det gør også økologien sårbar i de tilfælde, hvor produktionen ikke synes at leve op til økologiens egne værdier. Gennem en analyse af økologiens værdier identificeres en fundamental prioritering i økologien, nemlig at miljø, dyrevelfærd og menneskelig sundhed skal tjenes gennem et ’sundt’ økosystem, snarere end gennem isoleret behandling af symptomer. Det følger heraf, at hvis dyr, mennesker eller miljøet vedholdende fungerer dårligt i økosystemet, så skal løsningen søges i at få økosystemet til arbejde ’sundere’. Nogle af de velfærdsproblemer, som findes hos økologiske æglæggende høner, ville ifølge økologiens ideer løses ved små flokstørrelser, men denne løsning realiseres ikke på grund af økonomiske hensyn. For andre problemer mangler der ideer til løsning. Denne case er måske ikke i sig selv repræsentativ for al økologisk produktion, men den rejser alligevel et principielt spørgsmål om, i hvilket omfang økonomiske hensyn tillader økologien at gå på kompromis i forhold til egne værdier – et spørgsmål, som det er relevant for økologien at overveje i lyset af, at nye markedsandele ofte vil være betinget af, at merprisen i forhold til konventionelle produkter må være beskeden. Artiklen peger på to mulige strategier: den pragmatiske, hvor man indrømmer, at det kan være nødvendigt at gå på kompromis, og den idealistiske, hvor man afviser alvorlige kompromiser på bekostning af, at visse former for produktion ikke vil være realisable

Optimal calibration in immunoassay and inference on the coefficient of variation

This thesis examines and develops statistical methods for design and analysis with applications in immunoassay and other analytical techniques. In immunoassay, concentrations of components in clinical samples are measured using antibodies. The responses obtained are related to the concentrations in the samples. The relationship between response and concentration is established by fitting a calibration curve to responses of samples with known concentrations, called calibrators or standards. The concentrations in the clinical samples are estimated, through the calibration curve, by inverse prediction. The optimal choice of calibrator concentrations is dependent on the true relationship between response and concentration. A locally optimal design is conditioned on a given true relationship. This thesis presents a novel method that accounts for the variation in the true relationships by considering unconditional variances and expected values. For immunoassay, it is suggested that the average coefficient of variation in inverse predictions be minimised. In immunoassay, the coefficient of variation is the most common measure of variability. Several clinical samples or calibrators may share the same coefficient of variation, although they have different expected values. It is shown here that this phenomenon can be a consequence of a random variation in the dispensed volumes, and that inverse regression is appropriate when the random variation is in concentration rather than in response. An estimator of a common coefficient of variation that is shared by several clinical samples is proposed, and inferential methods are developed for common coefficients of variation in normally distributed data. These methods are based on McKay's chi-square approximation for the coefficient of variation. This study proves that McKay's approximation is noncentral beta distributed, and that it is asymptotically normal with mean n - 1 and variance slightly smaller than 2(n - 1)

The photochemistry of carbon monoxide in the stratosphere and mesosphere evaluated from observations by the Microwave Limb Sounder on the Aura satellite

The photochemical production and loss rates for carbon monoxide (CO) in the stratosphere and mesosphere are evaluated using measurements from the Aura Microwave Limb Sounder (MLS) and the Atmospheric Chemistry Experiment-Fourier Transform Spectrometer (ACE-FTS). The distributions of reactive trace gases involved in the photochemistry of CO, including OH, CH4, O(D-1), Cl, as well as temperatures for calculating reaction rates, are either directly observed or constrained from observations. We map the CO net production and loss as a function of pressure (10-0.02 hPa, about 30-75 km altitude), latitude (approximately +/- 70 degrees), and season. The results indicate that photochemical loss dominates over production for nearly all conditions considered here. A minimum photochemical loss lifetime of about 10 days occurs near the 2 hPa pressure level, and it follows the region of maximum sunlight exposure. At high latitudes during winter, the CO lifetime is generally longer than 30 days. Time scales become much shorter in spring, however, when CO lifetimes can be 15-20 days poleward of 60 degrees latitude in the upper stratosphere. On the basis of these results, CO is a suitable tracer during autumn to spring above the 0.1 hPa pressure level but not in the upper stratosphere near 1 hPa.</p