Search

The Bessel distribution, introduced recently by Yuan and Kalbfleisch (Ann. Inst. Math. Statist., 2000), can be useful in many applications. In particular, this distribution appears in two Bayesian estimation problems, namely, estimation of the noncentrality parameter of a noncentral chi-square distribution and of the parameters of Downton's bivariate exponential distribution. Implementation of Markov chain Monte Carlo algorithms requires generation of observations from the Bessel distribution. In this paper we propose and compare exact simulation schemes generating Bessel variates based on certain properties of the distribution as well as the rejection method.

In this paper a class of goodness-of-fit tests for the Rayleigh distribution is proposed. The tests are based on a weighted integral involving the empirical Laplace transform. The consistency of the tests as well as their asymptotic distribution under the null hypothesis are investigated. As the decay of the weight function tends to infinity the test statistics approach limit values. In a particular case the resulting limit statistic is related to the first nonzero component of Neyman’s smooth test for this distribution. The new tests are compared with other omnibus tests for the Rayleigh distribution.

On the basis of an observation from the binomial distribution with known probability of success p, we construct two classes of admissible estimators of the parameter n∈ { 1,2,… } when the loss function is the squared error. The estimators are either proper Bayes or limits of Bayes estimators.

During the last five years systematic explorations of the Natural History Museum of Crete have added more than 20 Pleistocene fossil localities around Crete to the catalogue of the over 70 already known on the Island. The new localities are distributed in all four prefectures of Crete. The most important of these is the newly discovered site of Koutalas at Cape Drepano in Western Crete. The fossil remains are found in two levels and in red cemented clays of a collapsed cave. In the upper level a rich assemblage of micromammal, bird and large mammal remains has been discovered. The large mammals consist of dwarf hippopotamus (Hippopotamus creutzburgi) and elephants (Elephas sp.). A partly articulated skeleton (vertebral column, mandible and few long bones) of a dwarf hippo has been found next to a deciduous molar of an elephantid, indicating that the two taxa probably coexisted. The micromammal remains belong to the giant Cretan mouse Kritimys catreus. Therefore, the age of the assemblage is dated to the Kritimys catreus zone and thus to the late Middle Pleistocene. In the lower level scattered remains of deers, birds and micromammals have been identified, and their age is most likely younger than that of the upper level.

A rich terrigenous plant assemblage was recently excavated from early Tortonian deposits at Messara basin, southern Crete. The macro-remains are perfectly preserved as impressions or carbonized compressions in poorly lithified and locally laminated, blue-green clays with an age of at least 10.5 Ma and thus can be considered as the oldest plant assemblage found in Crete todate. Gymnosperms are represented by the families of Pinaceae (pine needles and winged seeds), Cupressaceae and Taxodiaceae (leafy twings of Taxodium). Besides, 19 different angiosperm taxa of trees and shrubs have been also determined. Fagaceae is the most diversified with foliage of beech and several deciduous and evergreen oaks, while Myricaceae contribute mainly as abundant leaf remains of Myrica lignitum. Accessory elements of evergreen Lauraceae (Daphnogene polymorpha), sclerophyllus shrubs of Buxaceae (Buxus pliocenica) and various deciduous dicotyledonous such as Populus crenata, Liquidambar europaea, Carya minor and Acer pseudomonspessulanum are well documented. Leguminosae is recorded by a significant number of various small leaflet imprints. Therefore, the recovered remains indicate swampy forest habitats dominated by hygrophilic woody plants of Taxodium and Myrica, while in the surrounding plains and slopes a mixed mesophytic forest with a relatively low proportion of evergreen plants occurred in early-Late Miocene times in Crete depicting a moderately humid, warm-temperate nature for the climate.

In this paper the problem of estimating the ratio of variances, σ, in a bivariate normal distribution with unknown mean is considered from a decision-theoretic point of view. First, the UMVU estimator of σ is derived, and then it is shown to be inadmissible under two specific loss functions, namely, the squared error loss and the entropy loss. The derivation of the results is done by conditioning on an auxiliary negative binomial random variable.

This paper deals with decision theoretic estimation of the middle among three ordered location parameters under an arbitrary strictly convex loss function. Double-shrinkage estimators are produced which use all the available data and improve on single-shrinkage ones. The case of estimation of the middle among three ordered scale parameters with the possible existence of nuisance parameters is also discussed.

We consider the problem of decision-theoretic estimation of the ratio of generalized variances of two matrix normal distributions with unknown means under a general loss function. The inadmissibility of the best affine equivariant estimator is established by exhibiting various improved estimators. In particular, under certain conditions on the loss, two classes of improved procedures based onallthe available data are presented. As a preliminary result of independent interest, an improved estimator of an arbitrary power of the generalized variance of a matrix normal distribution with an unknown mean is derived under a general strictly bowl-shaped loss.

A confidence interval for the generalized variance of a matrix normal distribution with unknown mean is constructed which improves on the usual minimum size (i.e., minimum length or minimum ratio of endpoints) interval based on the sample generalized variance alone in terms of both coverage probability and size. The method is similar to the univariate case treated by Goutis and Casella (Ann. Statist. 19 (1991) 2015–2031).

Background and Aim: The treatment-of-choice for the optimal management of the dyslipidemia of the metabolic syndrome (MetS) is not clearly defined. We compared the efficacy of 4 drug regimes for the management of this dyslipidemia in a mouse model. Materials and Methods: A total of 60 C57B16 mice comprised the study group. The first 10 received standard mouse food for the whole experiment (control group). The remaining 50 mice received atherogenic diet for 14 weeks until the development of the MetS. The mice were then divided into 5 groups: the 1st group continued receiving atherogenic diet, while the other 4 groups received atherogenic diet plus ezetimibe (10 mg/kg per day), fenofibrate (100 mg/kg per day), low-dose atorvastatin (10 mg/kg per day), or high-dose (40 mg/kg per day) atorvastatin, respectively, for another 8 weeks. Results: High-dose atorvastatin treatment achieved the best lipid profile compared with low-dose atorvastatin, ezetimibe, and fibrate therapy. The lipid profile of mice receiving atherogenic diet plus high-dose atorvastatin treatment was similar with mice on regular chow. Conclusions: High-dose atorvastatin treatment resulted in optimization of the lipid profile in the presence of a high-fat atherogenic diet in a mouse model. Our results suggest that high-dose atorvastatin treatment may be the optimal treatment option for the dyslipidemia associated with MetS. Nevertheless, verification of these results in humans is required before any definite conclusions can be drawn.

In the last five years, the discovery of several new localities of fossil Sirenians found in the Neogene sediments of Crete has increased drastically the number of sirenian localities on the island. Some of the most important findings consist of almost complete post cranial skeletons (localities of Stilos, Panassos near Zaros and Tripitos in Agia Fotia near Siteia). Furthermore, the locality Kotsiana near Chania, where in 1973 Symeonidis and Schultz reported the first sirenian findings from Crete, was revisited and several new sites were recorded. The most recent findings not thoroughly studied yet, are situated in three new fossiliferous sites near Panassos village (Ampelouzos, Panasos 2 and Kefala), and in Afrata at Rodopou peninsula. The preliminary morphological and metrical study of the remains from Panassos and Tripitos, and their comparison with other findings from Crete, as well as with Sirenian material from European localities, has shown that all studied individuals belong to the species Metaxytherium cf. medium (Desmarest 1822). The age of the studied Cretan Sirenian material has been determined as Late Miocene (Tortonian) and the presence of Sirenia in Crete indicates the prevalence of shallow and warm marine environments in coastal areas, rich in sea weeds.

Transforming growth factors-beta (TGF-betas) are multifunctional polypeptides with crucial role as regulators of cellular growth and differentiation. It has been reported that TGF-beta1 plays a biphasic action on tumorigenesis thus inducing or inhibiting malignant properties of the epithelial cells.TGF-beta1 expression was analyzed in 56 patients with gastric carcinoma by immunohistochemical methods and compared with the expression of p21, p53, and Ki67, as well as with angiogenesis. The correlation of these markers with clinicopathological parameters was also evaluated.TGF-beta1 expression was detected in 71% of tumors and was more frequent in adenocarcinomas of the intestinal type (p0.001). Positivity of p21WAF1, and p53 was observed in 32% and 51% of the tumors, respectively. A high Ki67 proliferating index was detected in 53.5% of the tumors. TGF-beta1 expression was significantly correlated with p21 expression (p0.001) and was inversely correlated with microvessel density. p21 expression was also higher in tumors with low proliferating index (p0.01). There was no apparent correlation between the expression of these markers and tumor stage, depth of invasion, or lymphnode metastases.The findings show that TGF-beta1 may be involved in the activation of the cdk inhibitor p21WAF1 in gastric adenocarcinomas, suggesting p53-independent induction of p21 in gastric cells. TGF-beta1 does not seem to contribute to the alteration of the angiogenic status of these tumors.

The issue of collapsing categories of a contingency table's classification variables is well known and has been dealt with in the framework of classical models such as models of independence and association, canonical correlation and logistic regression. The most often used criterion is based on the homogeneity of the corresponding categories which was connected to association and correlation models by Goodman (1981 a,b) and Gilula (1986), respectively. In this paper we relate homogeneity to a class of generalized association models, based on the f-divergence. The main issue raised in this paper is that the homogeneity and the structural criteria can not be contradictory. It is proved that collapsing among homogeneous categories does not affect the underlying structure of the table. Statistics

Confidence intervals for the ratio of scale parameters are constructed in general families of distributions with nuisance (location) parameters. Each of these intervals has coverage probability at least as large as that of the standard minimum size (i.e., minimum ratio of endpoints) interval and, in addition, smaller size. Then analogous improved confidence intervals for the scale parameters subject to order restriction are derived. The method of construction is similar to that in Goutis and Casella [5], [6]. Examples are given and include the normal and exponential distributions as well as the inverse Gaussian distribution which is not a purely location–scale model. Applications to interval estimation of the error variance in variance components models are also discussed.

Η εργασία αυτή αποτελεί μια πλήρη καταγραφή των πιο σημαντικών γεωτόπων της Κρήτης που βασίστηκε στην αποδελτίωση της υπάρχουσας βιβλιογραφίας και προηγούμενων προσπαθειών και στη συλλογή στοιχείων υπαίθρου. Ακολούθως δημιουργήθηκε μια βάση δεδομένων με την τεκμηρίωση των γεωτόπων στην οποία και στηρίχθηκε η προσπάθεια αξιολόγησης τους. Κατά το στάδιο αυτό χρησιμοποιήθηκαν διεθνώς αποδεκτές μεθοδολογίες ώστε για κάθε γεώτοπο να καθοριστεί η σπουδαιότητα, η αξία, οι ενδεχόμενες απειλές και η μελλοντική συνεισφορά τους στην ανάπτυξη της επιστήμης και των τοπικών κοινωνιών. Έτσι αναγνωρίστηκαν περίπου 132 γεώτοποι εθνικής ή περιφερειακής σπουδαιότητας, που είτε αντιπροσωπεύουν χαρακτηριστικές θέσεις για τη γεωλογία της Κρήτης, είτε έχουν μεγάλη αξία για οικοσυστήματα ή τον πολιτισμό. Η αξία των περισσότερων από αυτούς είναι κυρίως επιστημονική/ εκπαιδευτική ή αισθητική, ενώ δεν αναγνωρίστηκαν σημαντικές απειλές για την πλειονότητα τους, εκτός από την επίδραση του τουρισμού σε μερικούς σπήλαια. Τα αποτελέσματα της προσπάθειας αυτής σε συνδυασμό με μια αλλαγή στάσης σε εθνικό επίπεδο μπορεί να αποτελέσουν την απαρχή για τη διατήρηση και την ανάδειξη της γεωλογικής κληρονομιάς της Κρήτης, This study presents the first complete list of the most important geological features and landforms of Crete. Identification of geo topes and collection of data were based on earlier publications and similar efforts, search in existing scientific literature and field observations. A database was formed containing the overall documentation of each geotope, on which evaluation was afterwards implemented. Worldwide tested methodologies were used for the recognition of the importance and value for each geotope, as well as, the identification of possible threats and future perspectives for local economic and scientific development. About 132 geotopes were recognized for their national or regional importance, their representativeness for the interpretation of Cretan geology and impact on natural ecosystems and local culture. The majority of these geotopes are of high scientific and aesthetic value serving in our days tourist and scientific/educational purposes. Generally no serious threats or dangers have been recognized, except of few caves where the impact of massive tourism is serious. These results set a minimum base for the conservation and enhancement of Cretan earth heritage, that should be followed by nationally based actions for further recognition and legal protection of our geodiversity

We consider estimation of the ratio of arbitrary powers of two normal generalized variances based on two correlated random samples. First, the result of Iliopoulos [Decision theoretic estimation of the ratio of variances in a bivariate normal distribution, Ann. Inst. Statist. Math. 53 (2001) 436–446] on UMVU estimation of the ratio of variances in a bivariate normal distribution is extended to the case of the ratio of any powers of the two variances. Motivated by these estimators’ forms we derive the UMVU estimator in the multivariate case. We show that it is proportional to the ratio of the corresponding powers of the two sample generalized variances multiplied by a function of the sample canonical correlations. The mean squared errors of the derived UMVU estimator and the maximum likelihood estimator are compared via simulation for some special cases.