A Bayesian analysis of experiments with small numbers of events

Within the framework of Bayesian statistics we derive a distribution for the posterior degree of belief both for the difference and ratio of small numbers of events, when the background mean in each case is known with finite precision.     

Kalman filtering of traffic fluctuations for real-time network management

Discrete- time stochastic models of sequential traffic records in telephone networks are considered. They appear to be well suited for a use of the Kaiman filter. A version of the filtering algorithm is adopted to deal with traffic fluctuations. The overall approach is tested against the real data gathered by the supervisor of the French toll network. The adaptive traffic estimator is inserted into a simulator of a testbed network operated in the urban zone of Paris. The traffic estimations provided by the filter are used to decide an overflow hierarchy.     

Serum beta-carotene deficiency in HIV-infected children

Representative levels of serum micronutrients specifically, beta-carotene and vitamins A and E, were studied in symptomatic human immunodeficiency virus (HIV)-infected children. The nutritional status of 23 symptomatic African-American and Hispanic HIV-infected children were compared with an appropriate control group comprised of 36 uninfected children matched for age and sex, using body mass index. Serum beta-carotene and vitamin A and E levels were randomly determined on 15 of the infected children. Beta-carotene concentration was 4.9-fold reduced in symptomatic HIV-infected children when compared with the control group. There was a 6.5-fold decrease in the serum level for children without acquired immunodeficiency syndrome (AIDS) and a 13-fold reduction in children with AIDS. No differences in the mean values for serum vitamins A and E were observed in the groups studied. Although the nutritional status of the symptomatic HIV-infected children was not different from that of the control population, their serum beta-carotene levels were profoundly deficient. This finding may have immunologic and clinical implications for children with rapidly progressing HIV disease.     

Inference about long run canonical correlations

This article proposes methods for testing the null hypothesis that a number of so‐called long run canonical correlations (LRCCs) are zero. Two test statistics are proposed and their limiting distributions are derived under the null hypothesis. The finite sample properties of the tests are illustrated via a number of simulation studies that reveal the asymptotic theory provides a good guidance to behaviour in moderate or large sized samples. It is shown that the statistics provide a natural way for testing the asymptotic independence of two standardized sums. The usefulness of the tests is illustrated via the following examples: inference about cointegrating vector in a particular cointegration model; inference about break points in a cointegration model; moment estimation; parameter estimation in Generalized Method of Moments estimation.     

Does financial development lower energy intensity?

The growth-induced effects of financial development have been well-established in the empirical literature, as well as the significance of financial development to energy demand behavior. However, the empirical evidence on the relationship between financial development and energy intensity remains sparse in the literature. Given the multifaceted nature of the effects of financial development, the proposed relationship seems a complex one and warrants an empirical investigation. Using the case of Ghana, this study provides an empirical answer to the question: does financial development lower energy intensity? To provide solid grounds for either rejection or acceptance of the null hypothesis, this study performed several robustness checks. Generally, the evidence revealed that financial development lowers energy intensity. Further, the results revealed that the price of energy, trade liberalization and industry structure play significant roles. These results have important implications for the design of macro energy efficiency policies and the creation of a ‘Green Bank’.     

Mobilization and homing of peripheral blood progenitors is related to reversible downregulation of alpha4 beta1 integrin expression and function

Despite the wide use of mobilized peripheral blood (PB) progenitor cells (PBPC) for clinical transplantation the mechanism(s) underlying their mobilization and subsequent engraftment are still unknown. We compared the adhesive phenotype of CD34(+) colony-forming cells (CFC) in bone marrow (BM) and PB of normal donors before and after administration of granulocyte colony-stimulating factor (G-CSF) for 5 d. G-CSF-mobilized PB CFC cells adhered significantly less to BM stroma, fibronectin, and to the alpha4 beta1 binding fibronectin peptide, CS1, because of decreased expression of the alpha4 integrin. Since incubation of BM CD34(+) cells for 4 d with G-CSF at concentrations found in serum of G-CSF- treated individuals did not affect alpha4-dependent adhesion, G-CSF may not be directly responsible for the decreased alpha4-mediated adhesion of PB CFC. Culture of G-CSF-mobilized PB CD34(+) cells with cytokines at concentrations found in BM stromal cultures upregulated alpha4 expression and restored adhesion of mobilized PB CFC to stroma, fibronectin, and CS1. Adhesion of cultured, mobilized PB CFC to stroma and CS1 could not be further upregulated by the beta1 activating antibody, 8A2. This indicates acquisition of a maximally activated alpha4 beta1 integrin once PB CFC have been removed from the in vivo mobilizing milieu. Thus, decreased alpha4 expression on CD34(+) CFC in PB may be responsible for the aberrant circulation of mobilized PB CD34(+) cells. Reexpression of a maximally activated alpha4 beta1 integrin on mobilized PB CFC removed from the mobilizing in vivo milieu may contribute to the early engraftment of mobilized PBPC.     

A mutual assessment of the uncertainties of digital elevation models using the triple collocation technique

This study investigates the uncertainties of digital elevation models (DEMs) using the triple collocation (TC) method. DEMs from satellite missions are important for many geoscience disciplines and for economic benefits and are freely available. Validating DEMs is necessary to select an appropriate model for a given region and application. Provided certain assumptions about the error structure of any three data sets – measuring the same phenomenon – can be made, the TC approach can be used to provide an unbiased and scaled estimate of the error variances of the data sets, without requiring a reference data. We compared the TC approach to the traditional approach of using a reference data set using the Shuttle Radar Topography Mission version 4.1 (SRTM v4.1) DEM, ASTER (the Advanced Spaceborne Thermal Emission and Reflection Radiometer) GDEM (Global DEM) version 2, the 1 arc-minute global relief model (ETOPO1), a DEM compiled by the Survey and Mapping Division of Ghana (SMD DEM), and 545 ground control stations (GCSs). The error estimates for the DEMs via TC were considerably smaller than those obtained from the reference-based approach. As an example, the best performing DEM (SRTM v4.1) recorded a root-mean-square error (RMSE) of 15.601 m using the GCSs as reference, while its TC-derived accuracy was 6.517 m. We note that based on the results of the TC, the estimated error of the GCSs is approximately 14 m. Using a data set with an error of 14 m to validate other data sets is certainly bound to result in unfavorable results. Thus, we have demonstrated in this work that the TC approach is able to provide an unbiased error of DEMs. The approach is important even for regions where GCSs are highly accurate, but more so for regions with low-quality GCSs.