bluuebunny/crossref_metadata_2025_split huggingface dataset:
Spontaneous mutation in Big Blue® mice from fetus to old age: Tissue‐specific time courses of mutation frequency but similar mutation types
Authors: Hill Kathleen A. , Buettner Victoria L. , Halangoda Asanga , Kunishige Makoto , Moore Stephen R. , Longmate Jeffrey , Scaringe William A. , Sommer Steve S. 
Published: February 2004

AbstractTransgenic mouse mutation detection systems permit rapid determination of the frequency and type of mutations allowing direct examination of mutational markers for aging, neurodegeneration, and cancer. The Big Blue® transgenic mouse mutation detection system was used to determine the frequency and nature of spontaneous mutations versus age in multiple tissue types. Nuclear DNA was extracted from whole fetus at 13.5 days postcoitus (dpc) and from six tissues postbirth (cerebellum, forebrain, thymus, liver, adipose tissue, and male germline) of Big Blue transgenic mice at four ages: 10 days and at 3, 10, and 25 months postbirth. Forty million total plaque‐forming units (pfu) were screened. The time course of mutation frequency with age had a significantly different shape in different tissues (P < 10−6). By 13.5 dpc, the whole fetus mutation frequency had already started increasing from the theoretical zero at conception to a value that was about one‐half the mid‐adulthood (3–10 months) average. From 10 days to 3 months, mutation frequency increased significantly in liver (P = 0.007) and showed an increasing trend in cerebellum, forebrain, and thymus. From 3 to 10 months, there was no significant change in mutation frequency in any tissue examined. From 10 to 25 months, the mutation frequency increased significantly in liver (P < 10−6) and adipose tissue (P = 0.002), but not in the other tissues examined (cerebellum, forebrain, and male germline). It is of interest that the mutation frequency in the male germline is consistently the lowest, remaining essentially unchanged in old age. The spectrum of mutation types was unaltered with age, tissue type and gender, although, as previously reported, tandem GG→TT mutations are tissue specific and show significant increases with age and certain hotspots (Buettner VL et al. [1999]: Environ Mol Mutagen 33:320–324; Hill KA et al. [2003]: Mutat Res 534:173–186). The spectrum of mutation types was generally the same for all tissue types, despite the tissue‐specific increases in mutation frequency with age. These data provide a useful reference for future studies of endogenous and exogenous mutagenesis. Environ. Mol. Mutagen. 43:110–120, 2004. © 2004 Wiley‐Liss, Inc.
Mutagenicity of carbon tetrachloride and chloroform in Salmonella typhimurium TA98, TA100, TA1535, and TA1537, and Escherichia coli WP2uvrA/pKM101 and WP2/pKM101, using a gas exposure method
Authors: Araki Akihiro , Kamigaito Nobuyuki , Sasaki Toshiaki , Matsushima Taijiro 
Published: February 2004

AbstractThe volatile solvents carbon tetrachloride and chloroform are carcinogens that are often reported as nonmutagenic in bacterial mutagenicity assays. In this study, we evaluated the mutagenicity of these compounds in Salmonella typhimurium TA98, TA100, TA1535, and TA1537, and Escherichia coli WP2uvrA/pKM101 and WP2/pKM101, with and without S9 mix, using a gas exposure method. Tests were also conducted with a glutathione‐supplemented S9 mix. Carbon tetrachloride was mutagenic in TA98 without S9 mix, and in WP2/pKM101 and WP2uvrA/pKM101 with and without S9 mix; carbon tetrachloride was not mutagenic in TA100, TA1535 or TA1537. Chloroform was mutagenic in WP2/pKM101, but only in the presence of glutathione‐supplemented S9 mix. Chloroform was not mutagenic in TA98, TA100, TA1535, TA1537, or WP2uvrA/pKM101 with or without S9 mix, and was not mutagenic in TA98, TA100, TA1535, TA1537, or WP2uvrA/pKM101 in the presence of glutathione‐supplemented S9 mix. The data indicate that carbon tetrachloride and chloroform are bacterial mutagens when adequate exposure conditions are employed and suggest that a genotoxic mode of action could contribute to the carcinogenicity of these compounds. Environ. Mol. Mutagen. 43:128–133, 2004. © 2004 Wiley‐Liss, Inc.
Clastogenicity of atrazine assessed with the Allium cepa test
Authors: Bolle Paola , Mastrangelo Sabina , Tucci Paolo , Evandri Maria G. 
Published: February 2004

AbstractAtrazine is classified as a restricted use pesticide and it is currently included in an international revision program for re‐evaluating the human and ecological (non‐human populations) health risks associated with its release into the environment. The present study was undertaken to add new data on the genotoxic potential of atrazine using the Allium cepa chromosome aberration test. The test concentrations were based on the Maximum Contaminant Levels in water intended for human consumption set by European and US regulations. Atrazine produced a concentration‐related increase in the number of total somatic chromosome aberrations, although this increase was statistically significant (p<0.05) only at the highest test concentration (5 μg/L). Analysis of the categories of structural chromosome damage indicated that breaks were the predominant lesion induced; the percent of cells per bulb with breaks also increased in a concentration‐related manner, and the increase was statistically significant at the two highest test concentrations (1 and 5 μg/L) (p<0.05). The Allium cepa plant assay detected the clastogenicity of atrazine at concentrations that are likely to be encountered in water, a common site of atrazine contamination. Environ. Mol. Mutagen. 43:137–141, 2004. © 2004 Wiley‐Liss, Inc.
Analysis of health outcome time series data in epidemiological studies
Authors: Touloumi Giota , Atkinson Richard , Tertre Alain Le , Samoli Evangelia , Schwartz Joel , Schindler Christian , Vonk Judith M. , Rossi Giuseppe , Saez Marc , Rabszenko Daniel , Katsouyanni Klea 
Published: February 2004

AbstractSeveral recent studies have reported significant health effects of air pollution even at low levels of air pollutants. These studies have been criticized for the statistical methods and for inconsistency in results between cities. An important development in air pollution epidemiology has come from multicenter studies. Within the APHEA‐2 project we have developed a statistical methodology to evaluate short‐term health effects of air pollution using data from 30 cities across Europe. For the analysis, a hierarchical modelling approach was adopted and implemented in two stages: (a) data from each city were analyzed separately to allow for local differences, using generalized additive Poisson regression models; (b) city‐specific effects estimates were regressed on city‐specific covariates to obtain an overall estimate and to explore heterogeneity across cities. In order to illustrate our methodology we present results for PM10 effects. It was found that a 10 μg/m3 increase in PM10 or NO2 concentrations is associated with a 0.67% (95% CI: 0.50 to 0.90) and 0.33% (0.20 to 0.40) increase in total mortality, respectively. After mutual adjustment, the PM10 effect was reduced by 40% and that of NO2 by 20%, but both pooled estimates remained significant. Long‐term mean NO2 concentrations act as an effect modifier for PM10 effects, even after adjustment for NO2 confounding effects. In the second stage we explored two different models for combining the adjusted for NO2, PM10 effects across cities: bivariate, which accounts for within‐city correlation of PM10 and NO2; and univariate, which ignores this correlation. Both models gave broadly the same results. Copyright © 2004 John Wiley & Sons, Ltd.
Optimization of ordered distance sampling
Authors: Nielson Ryan M. , Sugihara Robert T. , Boardman Thomas J. , Engeman Richard M. 
Published: February 2004

AbstractOrdered distance sampling is a point‐to‐object sampling method that can be labor‐efficient for demanding field situations. An extensive simulation study was conducted to find the optimum number, g, of population members to be encountered from each random starting point in ordered distance sampling. Monte Carlo simulations covered 64 combinations of four spatial patterns, four densities and four sample sizes. Values of g from 1 to 10 were considered for each case. Relative root mean squared error (RRMSE) and relative bias were calculated for each level of g, with RRMSE used as the primary assessment criterion for finding the optimum level of g. A non‐parametric confidence interval was derived for the density estimate, and this was included in the simulations to gauge its performance.Superior estimation properties were found for g > 3, but diminishing returns, relative to the potential for increased effort in the field, were found for g > 5. The simulations showed noticeable diminishing returns for more than 20 sampled points. The non‐parametric confidence interval performed well for populations with random, aggregate or double‐clumped spatial patterns, but rarely came close to target coverage for populations that were regularly distributed. The non‐parametric confidence interval presented here is recommended for general use. Copyright © 2004 John Wiley & Sons, Ltd.
Robust principal component analysis and outlier detection with ecological data
Authors: Jackson Donald A. , Chen Yong 
Published: February 2004

AbstractEcological studies frequently involve large numbers of variables and observations, and these are often subject to various errors. If some data are not representative of the study population, they tend to bias the interpretation and conclusion of an ecological study. Because of the multivariate nature of ecological data, it is very difficult to identify atypical observations using approaches such as univariate or bivariate plots. This difficulty calls for the application of robust statistical methods in identifying atypical observations. Our study provides a comparison of a standard method, based on the Mahalanobis distance, used in multivariate approaches to a robust method based on the minimum volume ellipsoid as a means of determining whether data sets contain outliers or not. We evaluate both methods using simulations varying conditions of the data, and show that the minimum volume ellipsoid approach is superior in detecting outliers where present. We show that, as the sample size parameter, h, used in the robust approach increases in value, there is a decrease in the accuracy and precision of the associated estimate of the number of outliers present, in particular as the number of outliers increases. Conversely, where no outliers are present, large values for the parameter provide the most accurate results. In addition to the simulation results, we demonstrate the use of the robust principal component analysis with a data set of lake‐water chemistry variables to illustrate the additional insight available. We suggest that ecologists consider that their data may contain atypical points. Following checks associated with normality, bivariate linearity and other traditional aspects, we advocate that ecologists examine their data sets using robust multivariate methods. Points identified as being atypical should be carefully evaluated based on background information to determine their suitability for inclusion in further multivariate analyses and whether additional factors explain their unusual characteristics. Copyright © 2004 John Wiley & Sons, Ltd.
Forecasting daily high ozone concentrations by classification trees
Authors: Bruno F. , Cocchi D. , Trivisano C. 
Published: February 2004

AbstractThis article proposes the use of classification trees (CART) as a suitable technique for forecasting the daily exceedance of ozone standards established by Italian law. A model is formulated for predicting, 1 and 2 days beforehand, the most probable class of the maximum daily urban ozone concentration in the city of Bologna. The standard employed is the so‐called ‘warning level’ (180 μg/m3). Meteorological forecasted variables are considered as predictors. Pollution data show a considerable discrepancy between the dimensions of the two classes of events. The first class includes those days when the observed maximum value exceeds the established standard, while the second class contains those when the observed maximum value does not exceed the said standard. Due to this peculiarity, model selection procedures using cross‐validation usually lead to overpruning. We can overcome this drawback by means of techniques which replicate observations, through the modification of their inclusion probabilities in the cross‐validation sets. Copyright © 2004 John Wiley & Sons, Ltd.
Parsimonious modelling, testing and forecasting of long‐range dependence in wind speed
Authors: Hussain S. , Elbergali A. , Al‐Masri A. , Shukur G. 
Published: February 2004

AbstractDetecting and estimating long‐range dependence are important in the analysis of many environmental time series. This article proposes a periodogram roughness (PR) estimator and describes its uses for testing and estimating the dependence structure. Asymptotic critical values are generated for performing the test, and special attention is given to investigating the properties of the PR regarding size and power. The conventional short‐memory models, such as the autoregressive (AR), are shown to be less parsimonious. Forecasting errors of both fractional Gaussian noise (FGN) and fractional autoregressive moving average (FARMA) are investigated by conducting simulation studies. In addition to the PR, maximum likelihood (ML) and semi‐parametric (SP) estimators are used and evaluated. Our results have shown that more accurate forecasted points are obtained when using the fractional forecasting. The methods are illustrated using Swedish wind speed data. Copyright © 2004 John Wiley & Sons, Ltd.
The influence of molecular diffusion on the distributed moments of a scalar PDF
Authors: Sullivan Paul J. 
Published: February 2004

AbstractSimple, physically based, approximations are used to obtain solutions to the exact, but intractable, equations that describe the evolution of the moments of the probability density function of a scalar (contaminant) released in a turbulent (environmental) flow. The effects of molecular diffusivity are assessed by comparing these solutions with the known results for the non‐physical case of zero molecular diffusivity. The results are also compared with experimental results from a steady source in wind tunnel, grid, turbulence. Copyright © 2004 John Wiley & Sons, Ltd.
Experimental study of the charring rate of tropical hardwoods
Authors: Njankouo Jacques Michel , Dotreppe Jean‐Claude , Franssen Jean‐Marc 
Published: February 2004

AbstractThis paper describes an experimental investigation of the charring rates of timber. An experimental procedure was designed for assessing the charring rate of 20 specimens exposed to fire in a single test, with one‐dimensional heat transfer conditions.Each test specimen was manufactured by gluing seven laminates together. Four thermocouples were inserted at different depths in four different laminates located in the middle of the test specimen. The test was conducted using a gas‐fired furnace and specimens were exposed to the standard ISO 834 fire.In order to evaluate the fire performance of tropical hardwoods, seven different species with densities ranging from 500 to 1000 kg/m3 were used. For the purpose of verifying the experimental procedure against existing data, two softwood species (spruce and fir) and one European hardwood species (oak) were also examined.Experimental results indicate that the test method and procedure can be used for assessing the charring rate of timber both for softwood and for hardwood species. They also show that the density of wood significantly affects the charring rate and that the values recommended in Eurocode 5 for high densities are somewhat too conservative. Copyright © 2004 John Wiley & Sons, Ltd.
Flame retardant performance of various UL94 classified materials exposed to external ignition sources
Authors: Hong Sanghyun , Yang Jaeho , Ahn Sunghee , Mun Yongik , Lee Gyucheol 
Published: February 2004

AbstractThe flammability of eight halogen‐free styrene resins and one halogen‐containing styrene resin was characterized by UL 94 VB, LOI and cone calorimeter tests. Their burning behaviour was also measured when exposed to three external ignition sources (methenamine tablet, candle, paper ball). Five resins were used for 19″ monitor housings and the others for 25″ TV. The LOI values of UL 94 V‐2, V‐1 and V‐0 rated resins were higher than that of HB. The heat release rate decreased as the UL 94 ratings increased from HB to V‐0. When these resins were exposed to three external ignition sources, UL 94 V‐1 and V‐0 rated resins showed a self‐extinguishing property after removal of the fire and did not cause fire growth in either 19″ monitor or the 25″ TV housings in all cases. However, UL 94 V‐2 and HB rated resins were easily ignited and spread fire by dripping burning trickles. The burning rate of V‐2 resin was slower than that of HB. Copyright © 2004 John Wiley & Sons, Ltd.
Mechanical impact tests of some selected polymers in high pressure liquid oxygen environments
Authors: Hshieh Fu‐Yu , Hirsch David B. , Beeson Harold D. 
Published: February 2004

AbstractThe threshold impact energies of the liquid oxygen mechanical impact test were determined for eight polymers at 6.9 MPa (1000 psi) oxygen pressure. The results show that there was no correlation between the threshold impact energy and the autoignition temperature of the polymers in high pressure oxygen environments. A violent explosion was observed in some of the tests when nylon 6/6, nitrile rubber and polyurethane rubber were impacted in high pressure liquid oxygen. Copyright © 2004 John Wiley & Sons, Ltd.
Surface temperature measurements on burning materials using an infrared pyrometer: accounting for emissivity and reflection of external radiation
Authors: Urbas Joe , Parker William J. , Luebbers Gerald E. 
Published: February 2004

AbstractThis paper demonstrates the successful use of an infrared pyrometer, operating in the 8–10 µm wavelength band, to measure the surface temperature of combustible specimens in a heat release calorimeter. The temperature histories of ten different materials were measured in the ICAL (intermediate scale calorimeter). The set of materials comprised four wood products, gypsum board, polyisocyanurate foam, PVC floor tile, PMMA and two non‐combustible boards. A small‐diameter bare thermocouple was installed on each specimen in order to determine an accurate temperature for comparison.The spectral emissivity and the spectral flux reflected from the surface were measured simultaneously and used to correct the apparent temperature measured by the pyrometer. The spectral emissivity and reflected spectral flux were both constant prior to ignition for all the combustible materials. During the burning phase all the combustible materials had a spectral emissivity very close to unity. The agreement between the temperatures measured with the pyrometer and thermocouple was not affected by the flame. The wood products, the polyisocyanurate foam and the calcium silicate board required no correction for reflected spectral flux over the whole temperature range. Copyright © 2004 John Wiley & Sons, Ltd.
A two‐dimensional vertical non‐hydrostatic σ model with an implicit method for free‐surface flows
Authors: Yuan Hengliang , Wu Chin H. 
Published: February 2004

AbstractAn implicit finite difference model in the σ co‐ordinate system is developed for non‐hydrostatic, two‐dimensional vertical plane free‐surface flows. To accurately simulate interaction of free‐surface flows with uneven bottoms, the unsteady Navier–Stokes equations and the free‐surface boundary condition are solved simultaneously in a regular transformed σ domain using a fully implicit method in two steps. First, the vertical velocity and pressure are expressed as functions of horizontal velocity. Second, substituting these relationship into the horizontal momentum equation provides a block tri‐diagonal matrix system with the unknown of horizontal velocity, which can be solved by a direct matrix solver without iteration. A new treatment of non‐hydrostatic pressure condition at the top‐layer cell is developed and found to be important for resolving the phase of wave propagation. Additional terms introduced by the σ co‐ordinate transformation are discretized appropriately in order to obtain accurate and stable numerical results. The developed model has been validated by several tests involving free‐surface flows with strong vertical accelerations and non‐linear waves interacting with uneven bottoms. Comparisons among numerical results, analytical solutions and experimental data show the capability of the model to simulate free‐surface flow problems. Copyright © 2004 John Wiley & Sons, Ltd.
Review of numerical special relativistic hydrodynamics
Authors: van Odyck D. E. A. 
Published: February 2004

AbstractThis paper gives an overview of numerical methods for special relativistic hydrodynamics (SRHD). First, a short summary of special relativity is given. Next, the SRHD equations are introduced. The exact solution for the SRHD Riemann problem is described. This solution is used in a Godunov scheme to compute solutions for two test problems. A third test problem is used to show non‐convergent behaviour of the numerical solution at the location of the contact discontinuity. Finally, a short description of numerical methods used so far in SRHD is given. Copyright © 2004 John Wiley & Sons, Ltd.
Unexpected embryonic stem (ES) cell mutations represent a concern in gene targeting: Lessons from “fierce” mice
Authors: Kumar Ravinesh A. , Chan Ka Ling , Wong Ambrose H.W. , Little Ken Q. , Rajcan‐Separovic Evica , Abrahams Brett S. , Simpson Elizabeth M. 
Published: February 2004

AbstractThe exceptional value of gene targeting technology to generate mouse models of human disease exists under the shadow of potential genetic errors. We previously observed an unexpected brain‐behavior phenotype that resulted from a gene‐targeting experiment designed to delete the Zfa gene. Given that the transcription of Zfa is restricted to the germ cell lineage of adult testis, it was both a surprise and a concern when the resulting mice had a phenotype present in both sexes that included abnormal brains and violent behavior. We hypothesized that an unrelated mutation may have been responsible for the unexpected phenotype. Here we show that the single gene mutation, Nr2e1frc (fierce), which was responsible for the brain‐behavior phenotype, existed in the embryonic stem (ES) cell even before the derivation of the Zfa knockout mice. Our work thus highlights a concern in gene targeting, namely, that ES cells can harbor unexpected mutations, which can lead to genotype‐phenotype misattribution. Based on our findings, we caution the gene‐targeting community to use low‐passage ES cells, to characterize mice derived from more than one independently targeted ES cell clone, and to backcross mice to allow for segregation of distant but linked mutations. genesis 38:51–57, 2004. © 2004 Wiley‐Liss, Inc.