ALBERT — All Library Books, journals and Electronic Records Telegrafenberg

1

Electronic Resource

Human Interindividual Variability in Parameters Related to Health Risks (1999)

Hattis, Dale ; Banati, Prerna ; Goble, Rob ; [et al.]

Springer

Risk analysis 19 (1999), S. 711-726

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ISSN: 1539-6924

Keywords: variability ; exposure ; susceptibility ; risk assessment ; pharmacokinetics ; pharmacodynamics

Source: Springer Online Journal Archives 1860-2000

Topics: Energy, Environment Protection, Nuclear Power Engineering

Notes: Abstract This paper reviews existing data on the variability in parameters relevant for health risk analyses. We cover both exposure-related parameters and parameters related to individual susceptibility to toxicity. The toxicity/susceptibility data base under construction is part of a longer term research effort to lay the groundwork for quantitative distributional analyses of non-cancer toxic risks. These data are broken down into a variety of parameter types that encompass different portions of the pathway from external exposure to the production of biological responses. The discrete steps in this pathway, as we now conceive them, are: •Contact Rate (Breathing rates per body weight; fish consumption per body weight) •Uptake or Absorption as a Fraction of Intake or Contact Rate •General Systemic Availability Net of First Pass Elimination and Dilution via Distribution Volume (e.g., initial blood concentration per mg/kg of uptake) •Systemic Elimination (half life or clearance) •Active Site Concentration per Systemic Blood or Plasma Concentration •Physiological Parameter Change per Active Site Concentration (expressed as the dose required to make a given percentage change in different people, or the dose required to achieve some proportion of an individual's maximum response to the drug or toxicant) •Functional Reserve Capacity–Change in Baseline Physiological Parameter Needed to Produce a Biological Response or Pass a Criterion of Abnormal Function Comparison of the amounts of variability observed for the different parameter types suggests that appreciable variability is associated with the final step in the process–differences among people in “functional reserve capacity.” This has the implication that relevant information for estimating effective toxic susceptibility distributions may be gleaned by direct studies of the population distributions of key physiological parameters in people that are not exposed to the environmental and occupational toxicants that are thought to perturb those parameters. This is illustrated with some recent observations of the population distributions of Low Density Lipoprotein Cholesterol from the second and third National Health and Nutrition Examination Surveys.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1007045922532

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2

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Evaluation of the Uncertainty in an Oral Reference Dose for Methylmercury Due to Interindividual Variability in Pharmacokinetics (1999)

Clewell, Harvey J. ; Gearhart, Jeffery M. ; Gentry, P. Robinan ; [et al.]

Springer

Risk analysis 19 (1999), S. 547-558

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ISSN: 1539-6924

Keywords: MeHg ; pharmacokinetics ; PBPK model ; variability ; risk assessment

Source: Springer Online Journal Archives 1860-2000

Topics: Energy, Environment Protection, Nuclear Power Engineering

Notes: Abstract An analysis of the uncertainty in guidelines for the ingestion of methylmercury (MeHg) due to human pharmacokinetic variability was conducted using a physiologically based pharmacokinetic (PBPK) model that describes MeHg kinetics in the pregnant human and fetus. Two alternative derivations of an ingestion guideline for MeHg were considered: the U.S. Environmental Protection Agency reference dose (RfD) of 0.1 μg/kg/day derived from studies of an Iraqi grain poisoning episode, and the Agency for Toxic Substances and Disease Registry chronic oral minimal risk level (MRL) of 0.5 μg/kg/day based on studies of a fish-eating population in the Seychelles Islands. Calculation of an ingestion guideline for MeHg from either of these epidemiological studies requires calculation of a dose conversion factor (DCF) relating a hair mercury concentration to a chronic MeHg ingestion rate. To evaluate the uncertainty in this DCF across the population of U.S. women of child-bearing age, Monte Carlo analyses were performed in which distributions for each of the parameters in the PBPK model were randomly sampled 1000 times. The 1st and 5th percentiles of the resulting distribution of DCFs were a factor of 1.8 and 1.5 below the median, respectively. This estimate of variability is consistent with, but somewhat less than, previous analyses performed with empirical, one-compartment pharmacokinetic models. The use of a consistent factor in both guidelines of 1.5 for pharmacokinetic variability in the DCF, and keeping all other aspects of the derivations unchanged, would result in an RfD of 0.2 μg/kg/day and an MRL of 0.3 μg/kg/day.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1007017116171

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3

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Kinetics and mechanism of MnO2 dissolution in H2SO4 in the presence of pyrite (1999)

Nayak, B. B. ; Mishra, K. G. ; Paramguru, R. K.

Springer

Journal of applied electrochemistry 29 (1999), S. 191-200

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ISSN: 1572-8838

Keywords: cyclic redox reaction ; dissolution ; kinetics ; manganese dioxide ; mechanism ; pyrite

Source: Springer Online Journal Archives 1860-2000

Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology

Notes: Abstract This paper describes a study of the kinetics and mechanism of MnO2 dissolution in H2SO4 in the presence of pyrite through leaching and electrochemical parameters. Manganese(iv) was found to dissolve mainly through reduction by the ferrous ion generated during oxidation of pyrite by the ferric ion. The oxidation which is slower and rate controlling may proceed through two different reactions, one producing S0 and the other SO42−. Manganese dissolution runs at the same rate as that of pyrite oxidation by maintaining ferrous ion concentration at a much lower level than that of ferric. Kinetic equations based on corrosion coupling principles are developed to explain the observed leaching behaviour.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1003490810114

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4

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Effect of ionic interactions on the rates of reduction of Cu(II) with H2O2 in aqueous solutions (1992)

Millero, F. J. ; Johnson, R. L. ; Vega, C. A. ; [et al.]

Springer

Journal of solution chemistry 21 (1992), S. 1271-1287

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ISSN: 1572-8927

Keywords: Cu(II) ; kinetics ; reduction ; temperature dependence ; H2O2, NaCl, NaBr, NaClO4

Source: Springer Online Journal Archives 1860-2000

Topics: Chemistry and Pharmacology

Notes: Abstract The rates of reduction of Cu(II) with H2O2 have been measured in NaCl and NaBr solutions and mixtures with NaClO4 as a function of pH (6 to 9), temperature (5 to 45°C) and ionic composition (0.1 to 6M). The effect of pH on the rates was found to be independent of temperature and ionic composition. The rates increased as a function of [H+] raised to the power of 1.3 to 1.6. Speciation calculations indicate that this pH dependence can be attributed to Cu(OH)2 being the reactive species. The rate constants in NaCl and NaBr and mixtures with NaClO4 were independent of ionic strength, but proportional to the halide concentration raised to the power of 2.0 (0.2 to 2.6M). These results can be attributed to Cu(OH)2Cl 2 2− being the reactive species to reduction with H2O2. The Cu(I) halide complexes formed from the reduction are not easily oxidized with O2 or H2O2. The faster rates in Br− solutions, which form stronger complexes with Cu+, support this contention. Measurements made in NaCl with added NaHCO3, NaB(OH)4 EDTA, NTA and glycine were also made. These measurements indicate that the CuL complexes (L=B(OH) 4 − , CO 3 2− , EDTA, NTA, and glycine) are not very reactive to reduction with H2O2. The addition of Mg2+ or Ca2+ caused the rates to increase due to the formation of MgL or CaL complexes and the resultant release of reactive Cu2+.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00667222

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5

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Factors affecting bioleaching kinetics of sulfide ores using acidophilic micro-organisms (1999)

Das, Trupti ; Ayyappan, Subbanna ; 〉Chaudhury, G.R.

Springer

BioMetals 12 (1999), S. 1-10

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ISSN: 1572-8773

Keywords: acidophilic ; strain ; oxidation ; kinetics

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Chemistry and Pharmacology

Notes: Abstract Recovery of metal values from sulfide ores by use of acidophilic microorganisms is gaining importance. A number of commercial/pilot plants are setup to find out the techno-economic feasibility of the overall process. The main drawback in the process is the slow kinetics of dissolution of metal values from the sulfide ores. To make the technology e attractive the kinetics should be improved considerably. There are various factors which determine the overall kinetics such as bacterial activity and concentration, iron and sulfur oxidation, oxygen consumption, reactor design and nature of ore. A brief review has been made dealing with the above parameters

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1009228210654

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6

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Degradation of Cellulosic Materials Under the Alkaline Conditions of a Cementitious Repository for Low- and Intermediate-Level Radioactive Waste. II. Degradation Kinetics (1999)

Van Loon, L. R. ; Glaus, M. A. ; Laube, A. ; [et al.]

Springer

Journal of polymers and the environment 7 (1999), S. 41-51

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ISSN: 1572-8900

Keywords: Cellulose ; alkaline degradation ; peeling off ; degree of polymerization ; kinetics ; (gluco)isosaccharinic acid

Source: Springer Online Journal Archives 1860-2000

Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Notes: Abstract The degradation of cellulosic materials, differing mainly in the degree of polymerization and the number of reducing end groups, was studied under the alkaline conditions similar to those existing in a cementitious repository for low- and intermediate-level radioactive waste (pH 13.3, T = 25°C). The kinetics of alkaline degradation (peeling-off reaction) were studied and the data analyzed by the model of Haas et al. [13]. The observed kinetic parameters for the propagation reaction and overall stopping reaction were compared with literature data. Although measured under different experimental conditions, literature data and data from this study show a consistent picture. Differences in the extent of degradation observed for the different cellulosic materials could be satisfactorily explained by differences in reducing end group content and, consequently, by differences in the degrees of polymerization. Besides the number of reducing end groups, the degree of amorphousness also plays an important role. The main degradation products formed under the experimental conditions used are α- and β-(gluco)isosaccharinic acid. This is in agreement with many other studies on alkaline degradation of cellulose. The two isomers are formed in roughly equal amounts.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1021894102937

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7

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Sorption Equilibria and Kinetics of Hydrocarbons onto Activated Carbon Samples Having Different Micropore Size Distributions (1999)

Wang, K. ; Do, D.D.

Springer

Adsorption 5 (1999), S. 25-37

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ISSN: 1572-8757

Keywords: micropore size distribution ; activated carbon ; adsorption ; desorption ; equilibrium ; kinetics

Source: Springer Online Journal Archives 1860-2000

Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology

Notes: Abstract This paper deals with the prediction of adsorption equilibrium and kinetics of hydrocarbons onto activated carbon samples having different micropore size distribution (MPSD). The microporous structure of activated carbon is characterised by the distribution of slit-shaped micropores, which is assumed to be the sole source of surface heterogeneity. The interaction between adsorbate molecule and pore walls is described by the Lennard-Jones potential theory. Different adsorbates have access to different pore size range of activated carbon due to the size exclusion, a phenomenon could have a significant influence on both multicomponent equilibria and kinetics. Activated carbons with three different MPSDs are studied with ethane and propane as the two model adsorbates. The Heterogeneous Macropore Surface Diffusion model (HMSD) is employed to simulate adsorption kinetics. The simulation results show that the MPSD is an important factor affecting both the multicomponent equilibria and kinetics.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1026481704926

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8

Electronic Resource

Furfural hydrogenation over carbon‐supported copper (1999)

Rao, Rajeev S. ; Baker, R. Terry K. ; Vannice, M. Albert

Springer

Catalysis letters 60 (1999), S. 51-57

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ISSN: 1572-879X

Keywords: furfural hydrogenation ; Cu/carbon catalysts ; kinetics

Source: Springer Online Journal Archives 1860-2000

Topics: Chemistry and Pharmacology

Notes: Abstract Furfural hydrogenation over copper dispersed on three forms of carbon – activated carbon, diamond and graphitized fibers – were studied. Only hydrogenation of the C=O bond to form either furfuryl alcohol or 2‐methyl furan occurred at temperatures from 473 to 573 K. Reduction at 573 K gave the most active catalysts, all three catalysts had activation energies of 16 kcal/mol, and turnover frequencies were 0.018–0.032 s-1 based on the number of Cu0 + Cu+ sites, which were counted by N2O adsorption at 363 K and CO adsorption at 300 K, respectively. The Cu/activated carbon catalyst showed no deactivation during 10 h on stream, in contrast to the other two catalysts. A simple Langmuir–Hinshelwood model invoking two types of sites was able to fit all kinetic data quite satisfactorily, thus it was consistent with the presence of both Cu0 and Cu+ sites.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1019090520407

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9

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Study of the ammonia decomposition over iron catalysts (1999)

Arabczyk, Walerian ; Zamlynny, Jacek

Springer

Catalysis letters 60 (1999), S. 167-171

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ISSN: 1572-879X

Keywords: ammonia decomposition ; iron catalyst ; kinetics

Source: Springer Online Journal Archives 1860-2000

Topics: Chemistry and Pharmacology

Notes: Abstract The decomposition of ammonia is a reaction associated with the process of the nitriding of metals. The kinetics of the ammonia decomposition on iron catalysts has been studied using a differential reactor with internal mixing. The balance between the inlet and outlet ammonia quantity has been used to determine the degree of conversion. The rate of ammonia decomposition could be described by the following expression: r = k0 exp (Ea/RT)pNH3. The activation energy of the ammonia decomposition process has been found for samples with potassium as E a= 96 kJ/mol, for samples without potassium as E a= 87 kJ/mol.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1019007024041

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10

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Pure and Binary Gas Adsorption Equilibria and Kinetics of Methane and Nitrogen on 4A Zeolite by Isotope Exchange Technique (1999)

Mohr, R.J. ; Vorkapic, D. ; Rao, M.B. ; [et al.]

Springer

Adsorption 5 (1999), S. 145-158

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ISSN: 1572-8757

Keywords: kinetics ; isotope-exchange ; nitrogen ; adsorption ; methane ; zeolite ; equilibria

Source: Springer Online Journal Archives 1860-2000

Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology

Notes: Abstract The Isotope Exchange Technique (IET) was used to simultaneously measure pure and binary gas adsorption equilibria and kinetics (self-diffusivities) of CH4 and N2 on pelletized 4A zeolite. The experiment was carried out isothermally without disturbing the adsorbed phase. CH4 was selectively adsorbed over N2 by the zeolite because of its higher polarizability. The multi-site Langmuir model described the pure gas and binary adsorption equilibria fairly well at three different temperatures. The selectivity of adsorption of CH4 over N2 increased with increasing pressure at constant gas phase composition and temperature. This curious behavior was caused by the differences in the sizes of the adsorbates. The diffusion of CH4 and N2 into the zeolite was an activated process and the Fickian diffusion model described the uptake of both pure gases and their mixtures. The self-diffusivity of N2 was an order of magnitude larger than that for CH4. The pure gas self-diffusivities for both components were constants over a large range of surface coverages (0 〈 θ 〈 0.5). The self-diffusivities of CH4 and N2 from their binary mixtures were not affected by the presence of each other, compared to their pure gas self-diffusivities at identical surface coverages.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1008917308002

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