Panel Cointegration Testing in the Presence of a Time Trend

The purpose of this paper is to propose a new likelihood-based panel cointegration test in the presence of a linear time trend in the data generating process. This new test is an extension of the likelihood ratio (LR) test of Saikkonen & Lütkepohl (2000) for trend-adjusted data to the panel data framework, and is called the panel SL test. The idea is first to take the average of the individual LR (trace) statistics over the cross-sections and then to standardize the test statistic with the appropriate asymptotic moments. Under the null hypothesis, this standardized statistic has a limiting normal distribution as the number of time periods (T) and the number of cross-sections (N) tend to infinity sequentially. In addition to the approximation based on asymptotic moments, a second approximation approach involving the moments from a vector autoregressive process of order one is also introduced. By means of a Monte Carlo study the finite sample size and size-adjusted power properties of the test are investigated. The test presents reasonable size with the increase in T and N, and has high power in small samples.Panel Cointegration Test, Likelihood Ratio, Time Trend, Monte Carlo Study

Asymptotic properties of model selection procedures in linear regression

In regression analysis there is typically a large collection of competing models available from which we want to select an appropriate one. This paper is concerned with asymptotic properties of procedures for selecting linear models, which are based on certain data-dependent criteria such as Mallows´ Cp, cross-validation and the generalized information criterion. We avoid the assumption of an adequate ("correct") model and allow the maximal model dimension to increase with the sample size. General asymptotic concepts are introduced, covering the usual ones of consistency and asymptotic optimality. The focus is on conditions for penalizing the model complexity which are necessary to optain the different optimalities. For example, the consistency of a procedure is decided by the interplay between these penalties, the complexity of the class of model candidates, and some quantity describing the ability to identify "wrong" (pseudo-inadequate) models. Many results known from the literature appear as special cases or are slightly modified

Health Insurance Competition: The Effect of Group Contracts

In countries like the US and the Netherlands health insurance is provided by private firms. These private firms can offer both individual and group contracts. The strategic and welfare implications of such group contracts are not well understood. Using a Dutch data set of about 700 group health insurance contracts over the period 2007-2008, we estimate a model to determine which factors explain the price of group contracts. We find that groups that are located close to an insurers’ home turf pay a higher premium than other groups. This finding is not consistent with the bargaining argument in the literature as it implies that concentrated groups close to an insurer’s home turf should get (if any) a larger discount than other groups. A simple Hotelling model, however, does explain our empirical results.health insurance;health-plan choice;managed competition

On the Existence of the Moments of the Asymptotic Trace Statistic

In this note we establish the existence of the first two moments of the asymptotic trace statistic, which appears as weak limit of the likelihood ratio statistic for testing the cointe- gration rank in a vector autoregressive model and whose moments may be used to develop panel cointegration tests. Moreover, we justify the common practice to approximate these moments by simulating a certain statistic, which converges weakly to the asymptotic trace statistic. To accomplish this we show that the moments of the mentioned statistic converge to those of the asymptotic trace statistic as the time dimension tends to infinity.Cointegration, Trace statistic, Asymptotic moments, Uniform integrability

On the minimax regret estimation of a restricted normal mean, and implications

Consider estimating the mean of a normal distribution with known variance, when that mean is known to lie in a bounded interval. In a decision-theoretic framework we study finite sample properties of a class of nonlinear' estimators. These estimators are based on thresholding techniques which have become very popular in the context of wavelet estimation. Under squared errorloss we show that there exists unique minimax regret solution for the problem of selecting the threshold. For comparison, the behaviour' of linear shrinkers is also investigated. In special cases we illustrate the implications of our results for the problem of estimating the regression function in a nonparametric situation. This is possible since, as usual, a, coordinatewise application of the scalar results leads immediately to results for multivariate (sequence space) problems. Then it is well known that orthogonal transformations can be employed to turn statements about estimation over coefficient bodies in sequence space into statements about estimation over classes of smooth functions in noisy data. The performance of the proposed minimax regret optimal curve estimator is demonstrated by simulated data examples

The Benefits of Using XML Technologies in Astronomical Data Retrieval and Interpretation

This paper describes a solution found during recent research that could provide improvements in the efficiency, reliability and cost of retrieving stored astronomical data. This solution uses XML Technologies in showing that when querying a variety of astronomical data sources a standardised data structure can be output into an XML query results Document. This paper shows the astronomical XMLSchema that has been partially developed in conjunction with simple custom supporting system software. It also discusses briefly possible future implications

Membrane-Water Partition Coefficients to Aid Risk Assessment of Perfluoroalkyl Anions and Alkyl Sulfates

This study determined the sorption affinity to artificial phospholipid membranes (K MW ) for series of perfluorinated carboxylates (PFCAs), perfluorinated sulfonates (PFSAs), alkyl sulfates (C x SO 4 ), and 1-alkanesulfonates (C x SO 3 ). A sorbent dilution assay with solid supported lipid membranes (SSLM) showed consistent CF 2 unit increments of 0.59, and CH 2 unit increments of 0.53, for the log K MW of perfluorinated and hydrogenated anions, respectively. PFSAs sorbed 0.90 log units stronger than analogue PFCAs; C x SO 4 sorbed 0.75 log units stronger than analogue C x SO 3 anions. The log K MW values for the octyl analogues increase in the order H(CH 2 ) 8 SO 3 - (1.74) &lt; H(CH 2 ) 8 SO 4 - (2.58) &lt; F(CF 2 ) 8 CO 2 - (PFNA, 4.04) &lt; F(CF 2 ) 8 SO 3 - (PFOS, 4.88). Intrinsic partition ratios determined on a phospholipid coated HPLC column (IAM-HPLC) closely aligned with SSLM K MW values. COSMO-RS based molecular calculations of K MW aligned with SSLM K MW values for hydrogenated anions with C 8 -C 14 alkyl chains but strongly underestimated CF 2 and CH 2 unit increments for C 4 -C 8 based anions. Dividing the critical narcotic membrane burden of 100 mmol/kg by the experimental K MW predicts lethal baseline toxicity concentrations (LC 50,narc ). The LC 50,narc coincides with the lowest reported acute LC 50 values for several anionic surfactants but were on average about an order of magnitude lower. </p

Culturing muscle fibres in hanging drop: A novel approach to solve an old problem

Background Information. The satellite cells (SCs) associated with muscle fibres play a key role in postnatal growth and regeneration of skeletal muscle. Commonly used methods of isolation and in vitro culture of SCs lead to the mixture of their subpopulations that exist within muscle. To solve this problem, we used the well established technique, the hanging drop system, to culture SCs in a three-dimensional environment and thus, to monitor them in their original niche. Results. Using hanging drop technique, we were able to culture SCs associated with the fibre at least for 9 days with one transfer of fibres to the fresh drops. In comparison, in the classical method of myofibres culture, that is, on the dishes coated with Matrigel, SCs leave the fibres within 3 days after the isolation. Cells cultured in both systems differed in expression of Pax7 and MyoD. While almost all cells cultured in adhesion system expressed MyoD before the fifth day of the culture, the majority of SCs cultured in hanging drop still maintained expression of Pax7 and were not characterised by the presence of MyoD. Among the cells cultured with single myofibre for up to 9 days, we identified two different subclones of SCs: low proliferative clone and high proliferative clone, which differed in proliferation rate and membrane potential. Conclusions. The hanging drop enables the myofibres to be kept in suspension for at least 9 days, and thus, allows SCs and their niche to interact each other for prolonged time. In a consequence, SCs cultured in hanging drop maintain expression of Pax7 while those cultured in a traditional adhesion culture, that is, devoid of signals from the original niche, activate and preferentially undergo differentiation as manifested by expression of MyoD. Thus, the innovative method of SCs culturing in the hanging drop system may serve as a useful tool to study the fate of different subpopulations of these cells in their anatomical location and to determine reciprocal interactions between them and their niche

Bench-to-bedside review : targeting antioxidants to mitochondria in sepsis

Peer reviewedPublisher PD