Exact asymptotic distribution of change-point mle for change in the mean of Gaussian sequences

We derive exact computable expressions for the asymptotic distribution of the change-point mle when a change in the mean occurred at an unknown point of a sequence of time-ordered independent Gaussian random variables. The derivation, which assumes that nuisance parameters such as the amount of change and variance are known, is based on ladder heights of Gaussian random walks hitting the half-line. We then show that the exact distribution easily extends to the distribution of the change-point mle when a change occurs in the mean vector of a multivariate Gaussian process. We perform simulations to examine the accuracy of the derived distribution when nuisance parameters have to be estimated as well as robustness of the derived distribution to deviations from Gaussianity. Through simulations, we also compare it with the well-known conditional distribution of the mle, which may be interpreted as a Bayesian solution to the change-point problem. Finally, we apply the derived methodology to monthly averages of water discharges of the Nacetinsky creek, Germany.Comment: Published in at http://dx.doi.org/10.1214/09-AOAS294 the Annals of Applied Statistics (http://www.imstat.org/aoas/) by the Institute of Mathematical Statistics (http://www.imstat.org

On the Conditional Variance for Scale Mixtures of Normal Distributions

For a scale mixture of normal vector, X = A1/2G, where X G ∈ Rnand A is a positive variable, independent of the normal vector G, we obtain that the conditional variance covariance, Cov(X2 X1), is always finite a,s for m ≥ 2, where X1∈ Rnand m < n, and remains a.s. finite even for m = 1, if and only if the square root moment of the scale factor is finite. It is shown that the variance is not degenerate as in the Gaussian case, but depends upon a function SA,m(.) for which various properties are derived. Application to a uniform and stable scale of normal distributions are also give

Assessing Change-Points in Surface Air Temperature Over Alaska

An understanding of low frequency climatic variations is important for climatologists and planning by the public for informed climate mitigation and adaptation. This study applies recent advances in statistical change-point methodology to the variability of temperatures from seven stations in Alaska and the Pacific Decadal Oscillation (PDO) climate index for the past decades. We allow for the presence of multiple change-points in any given data series and provide confidence intervals for the identified change-points. We analyze the multiple station data based on season and temperature means and extremes. Physical processes responsible for specific identified temperature changes have been explored through geopotential height field and sea level pressure (SLP) maps. Predominantly, temperature and PDO shifts were observed during winter and spring in the 1940s and the 1970s. The study also identifies anomalous changes in summer that have occurred either in 1960s or in the 1980s. This is a significant deviation from the changes found in the 1970s for winter and spring. Except for a change in the 1940s at King Salmon Airport (KSA) and one in the 1970s at Homer Airport (HA), no other changes were found in fall. Also, there is lack of clear low frequency cyclic variability in the northern North Pacific region. Due to strong interactions and feedbacks, Alaskan sea surface temperature changes identified in this study can have lasting impact upon a number of factors including sea ice, arctic snow cover, atmospheric heat transport, clouds, and others

Case Report Neuroendocrine Cell Carcinoma of Unknown Primary Arising in Long Standing History of Multiple Sclerosis

Multiple sclerosis (MS) is a chronic autoimmune disease that targets myelinated axons in the central nervous system (CNS). Cancer of unknown primary site (CUP) is a well-recognised clinical disorder, accounting for 3-5% of all malignant epithelial tumors. CUP is clinically characterised as an aggressive disease with early dissemination. Studies of cancer risk in MS patients have shown inconsistent findings. An increased risk of malignancy in patients with MS has been suggested, but recently serious questions have been raised regarding this association. Use of disease-modifying therapies might contribute to an increased cancer risk in selected MS patients. The concurrence of MS and CUP is exceptionally rare. Here we describe the case of a neuroendocrine carcinoma of unknown primary diagnosed in a male patient with a nine-year history of MS. The discussion includes data from all available population-based register studies with estimates of certain malignancies in patients with MS

The Refugee Issue in the Greek, German, and British Press During the Covid-19 Pandemic

The media hold an essential role in circulating information, disseminating knowledge, constructing representations, shaping ideologies, and influencing contemporary societies. Since the outburst of the coronavirus (Covid-19) pandemic, their attention has been mostly paid to the protection and the health situation of citizens worldwide. Although millions of refugees are also exposed to a new risk with their vulnerable position being deteriorated, the refugee issue in the context of the Covid-19 pandemic seems to have been downgraded. In this regard, the current article explores to what extent the refugee issue was salient in the Greek, German, and British press during the pandemic. At the same time, it looks at how the media outlets in all three countries addressed it, focusing on the key topics reported and the interpretive schemata of the pertinent coverage. We use a qualitative content analysis, examining a sample of newspaper articles that were published between 1 January 2021 and 1 May 2021. The results presented by this article suggest that the epidemiological developments or other health aspects related to local populations seem to overshadow the situation of refugees. Yet, media outlets mostly perceive refugees as victims of the pandemic, underlining their vulnerability and marginalisation in health, economic, and education terms. The findings seek to feed the public discussion, providing a fruitful approach to the media narratives and representations of refugees during the Covid-19 crisis