A general all-atom force field for atomistic simulation of common organic molecules, inorganic small molecules, and polymers was developed using state-of-the-art ab initio and empirical parametrization techniques. The valence parameters and atomic partial charges were derived by fitting to ab initio data, and the van der Waals (vdW) parameters were derived by conducting MD simulations of molecular liquids and fitting the simulated cohesive energies and equilibrium densities to experimental data. The combined parametrization procedure significantly improves the quality of a general force field. Validation studies based on large number of isolated molecules, molecular liquids and molecular crystals, representing 28 molecular classes, show that the present force field enables accurate and simultaneous prediction of structural, conformational, vibrational, and thermophysical properties for a broad range of molecules in isolation and in condensed phases. Detailed results of the parametrization and validation f...

COMPASS: An ab Initio Force-Field Optimized for Condensed-Phase ApplicationsOverview with Details on Alkane and Benzene Compounds

NOTE The report of the Committee without its annexes appears as Official Records of the General Assembly, Sixty-third Session, Supplement No. 46. The designations employed and the presentation of material in this publication do not imply the expression of any opinion whatsoever on the part of the Secretariat of the United Nations concerning the legal status of any country, territory, city or area, or of its authorities, or concerning the delimitation of its frontiers or boundaries. The country names used in this document are, in most cases, those that were in use at the time the data were collected or the text prepared. In other cases, however, the names have been updated, where this was possible and appropriate, to reflect political changes. Scientific Annexes Annex A. Medical radiation exposures Annex B. Exposures of the public and workers from various sources of radiation INTROdUCTION 1. In the course of the research and development for and the application of atomic energy and nuclear technologies, a number of radiation accidents have occurred. Some of these accidents have resulted in significant health effects and occasionally in fatal outcomes. The application of technologies that make use of radiation is increasingly widespread around the world. Millions of people have occupations related to the use of radiation, and hundreds of millions of individuals benefit from these uses. Facilities using intense radiation sources for energy production and for purposes such as radiotherapy, sterilization of products, preservation of foodstuffs and gamma radiography require special care in the design and operation of equipment to avoid radiation injury to workers or to the public. Experience has shown that such technology is generally used safely, but on occasion controls have been circumvented and serious radiation accidents have ensued. 2. Reviews of radiation exposures from accidents have been presented in previous UNSCEAR reports. The last report containing an exclusive chapter on exposures from accidents was the UNSCEAR 1993 Report [U6]. 3. This annex is aimed at providing a sound basis for conclusions regarding the number of significant radiation accidents that have occurred, the corresponding levels of radiation exposures and numbers of deaths and injuries, and the general trends for various practices. Its conclusions are to be seen in the context of the Committee's overall evaluations of the levels and effects of exposure to ionizing radiation. 4. The Committee's evaluations of public, occupational and medical diagnostic exposures are mostly concerned with chronic exposures of …

sources and effects of ionizing radiation

PAHs in the Fraser River basin: a critical appraisal of PAH ratios as indicators of PAH source and composition

A review of the biochemistry of heavy metal biosorption by brown algae

Synthetic Principles for Bandgap Control in Linear pi-Conjugated Systems.

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Studies on the Sequence of Uronic Acid Residues in Alginic Acid.

The acrylamide content of heated foodstuffs should be considered to be the net result of complex reactions leading to the formation and elimination/degradation of this compound. The present study, ...

Investigations of factors that influence the acrylamide content of heated foodstuffs.

Monitoring of environmental cancer initiators through hemoglobin adducts by a modified Edman degradation method

The degree of alkylation of proteins was used to determined tissue doses Dt i.e. the concentration of free alkylating agent, integrated over time, in resting male mice exposed for 1–2 h to air containing 1–35 ppm ethylene oxide (EO). The exposure doses were thus 0.03–2% of LD50. The results agree with an absorption of all EO in alveolar ventilation, a rapid distribution to all organs, and a rapid detoxication and excertion (biological half-life about 9 min). Dt is proportional to the exposure dose within the range studied. In most organs, including the testes, the Dt is about 0.5 μM · h per ppm · h of expsoure. The degree of alkylation of DNA agreed with expectation from the doses determined. Expressing genetic risks of environmental chemicals in the frame of reference of radiation hazard will facilitate comparison and summations of risks of various origins. On the basis of dose-effect curves of EO and X-rays in barely, a tissue dose of EO in man of i m M · h may be provisionally set equal to 80 rad of low LET radiation. Allowing for the difference in alveolar ventilation between mouse and man, this would mean that epoxide operators working at 5 ppm EO 40 h/week receive a weeky gonad dose of EO amounting to about 4 “rad-equivalenst”. Various data show that this risk estimate is realistic.

Evaluation of genetic risks of alkylating agents: tissue doses in the mouse from air contaminated with ethylene oxide.

The degree of alkylation of haemoglobin was determined at different times after treatment of mice with one directly active alkylating agent, ethylene oxide, and one agent that requires metabolic activation, dimethylnitrosamine. Because of the random alkylation of red blood cells of various ages and the stability of alkylated haemoglobin, the amount of alkylated amino acids in haemoglobin decreases linearly with time, reaching the value zero after about 40 days, the life-span of erythrocytes in the mouse. This provides a basis for the use of haemoglobin as a monitor for integral doses of genotoxic environmental chemicals.

Lars Ehrenberg

Papers

Studies on the Sequence of Uronic Acid Residues in Alginic Acid.

Investigations of factors that influence the acrylamide content of heated foodstuffs.

Monitoring of environmental cancer initiators through hemoglobin adducts by a modified Edman degradation method

Evaluation of genetic risks of alkylating agents: tissue doses in the mouse from air contaminated with ethylene oxide.

Evaluation of genetic risks of alkylating agents. II. Haemoglobin as a dose monitor.