Validation of QSAR models for legislative purposes

OECD principles of validation of Quantitative Structure – Activity Relationships (QSAR) models for legislative purposes are given and explained. Reasons of their origination and development, like system REACH, are described. A basic impulse has come from some OECD countries followed by all (almost) other countries of the world

Toxicity of perfluorinated carboxylic acids for aquatic organisms

Toxicity of perfluorinated carboxylic acids with carbon chain C8 to C12 were tested with oligochaeta Tubifex tubifex. Toxicity was evaluated as the exposure time ET50 from onset of damage of the oligochaeta in saturated aqueous solutions. The ET50 fluctuated between 25 and 257 minutes. No statistically significant difference was found among the C8, C9 and C12 acids (ET50 between 143 and 257 minutes with large standard deviation). The acids with carbon chain C10 and C11 induced the effect significantly quicker (25 to 47 minutes). No acute toxicity measured in the three-minute test was observed in any case

Effect of rubber powder from waste tyre rubbers on mechanical properties of one-component polyurethane putty

ArticleThe utilization of adhesives in technical practice is varied. Adhesives serve for a creation of strength bonds on the one hand, and on the other hand e.g. for cementing. The aim of the research is a modification of one - component polyurethane putty RPS 45 used in automotive industry to increase strength properties in an adhesive bond. An i nteraction between a filler in the form of rubber powder micro - particles and one - component polyurethane adhesive was investigated by means of SEM analysis. Sealing is a primary property of this putty. Sealing putties usually reach very small strength which can be increased by an admixture of the filler. In order to keep elastic properties, micro - particles of the rubber powder gained from tyre recycling process were used as the filler. An aspect of a loading speed of the adhesive bond is essential at the pra ctical application at which the adhesive bond can be failed in adhesive or cohesive layers. The adhesive bond can be perceived in terms of its function as a complex of three layers, i.e. an adhesive bonded material, the interaction between the adhesive and the adhesive bonded material and the adhesive layer itself. There are often states in the practices when the adhesive bonds are exposed to the loading which can be either a static or a dynamic one. That is why the research is focused not only on the evalu ation of the influence of the modification of the one - component polyurethane adhesive, but also on the influence of the loading speed of the adhesive bond. Tested speeds set on a universal testing machine Zwick/Roell Z150 were 2, 50 and 100 mm min - 1 . The r esults of mechanical tests proved a positive influence of the filler on the strength σ m higher by 42.68 ± 6.96% and the elongation at break ε b higher by 12.2 ± 20.95%. On the contrary, the stress at yield σ y was decreased

Research on influence of cyclic degradation process on changes of structural adhesive bonds mechanical properties

ArticleThe paper deals with an influence of a cyclic degradation process on changes of a shear tensile strength of single lap-shear adhesive bonds and their elongation according to ČSN EN ISO 9142. Five one-component structural adhesives used in a construction of car body works were used within the research. The degradation of adhesive bonds is a significant factor which influences a quality and a service life of adhesive bonds exposed to environment. A main requirement in production companies is not only reaching satisfactory initial mechanical properties but namely ensuring a reliability and a safety of adhesive bonds during their usage. These reasons show a great importance of adhesive bonds tests either directly in the operating environment or by a simulation of operating conditions in laboratories. The degradation process of adhesive bonds worsens mechanical properties of not only the bond itself but also of the bonded material. This process is progressing and it is usually permanent and irreversible. It is a change of mechanical and physical properties which can endanger a safety and a reliability of parts, prospectively of the whole equipment. It can leads up to a complete failure of its function in the extreme case. A temperature, a moisture, a direct contact with water and chemicals or an atmospheric corrosion belong among the most serious degradation agents. It is important to take into regard time of the processes influence at the same time which can act either independently or concurrently when their effects grow stronger. From that reason the adhesive bonds were exposed to the cyclic degradation process according to the standard ČSN EN ISO 9142. Subsequently, the adhesive bonds mechanical properties were tested on universal testing machine and by means of SEM analysis (TESCAN MIRA 3). Results of mechanical tests proved a fall of the shear tensile strength of single lap-shear adhesive bonds after 42 cycles of the degradation process of 12.8 to 21.7%. The bond strength fall was gradual and it showed a linear trend at some adhesives. Other adhesives showed a significant fall after the exposition to the degradation process after which the strength fall stabilized

Human urine certified reference material CZ 6010: creatinine and toluene metabolites (hippuric acid and o-cresol) and a benzene metabolite (phenol)

A reference material for the biological monitoring of occupational exposure to toluene, benzene and phenol was prepared. O-cresol and hippuric acid (metabolites of toluene) are used for the biological monitoring of occupational exposure to toluene. Phenol, a metabolite of benzene, is used for the biological monitoring of exposure to benzene, but phenol can of course also be used as an indicator of exposure to phenol as well. The reference material (RM) used for the determination of these metabolites was prepared by freeze-drying pooled urine samples obtained from healthy persons occupationally exposed to toluene and those taking part in an inhalation experiment. Tests for homogeneity and stability were performed by determining urine concentrations of o-cresol, hippuric acid, creatinine and phenol. To investigate the stability of the RM, the urinary concentrations of o-cresol and phenol were monitored for eighteen months using GC and HPLC, while those of hippuric acid and creatinine were followed for five and six years, respectively, using HPLC. Analysis of variance showed that the concentrations did not change. The certified concentration values (and their uncertainties) of the substances in this reference material (phenol concentration c=6.46+/-0.58 mg l(-1); o-cresol concentration c=1.17+/-0.15 mg l(-1); hippuric acid concentration c=1328+/-30 mg l(-1); creatinine concentration c=0.82+/-0.10 g l(-1)) were evaluated via the interactive statistical programme IPECA

Functional Structure of Metapodial Bones of Cattle

The supporting part of the metapodium skeleton of the thoracic limb consists of os metacarpale III et IV, developing through the fusion of two initially independent bones (III and IV). In the pelvic limb it is os metatarsale III et IV, developing analogically. In macerated bones of recent cattle at the age of 1-8 years and those from archaeological excavations (medieval, 9th–15th centuries) the length asymmetry of the above bones was studied by means of osteometry and the data obtained were evaluated statistically. In the thoracic limb metapodium, being the major supporting element in unguligrade paraxonic cattle, three possible relations between the lengths of metacarpals III and IV were observed, viz., (1) III longer than IV, (2) IV longer than III, and (3) both bones of the same length. In the metatarsus, i.e. the part of the pelvic limb with a largely locomotive function, bone IV was the longer one in all cases. Osteometric and statistical methods were also applied to the material mentioned above in order to examine the correlation of the width of cavum medullare with the overall width of a bone. While the relative width of the medullar cavity of the metapodium bones was found to be correlated with age, this correlation was negative in both the metacarpus and metatarsus (r =-0.6778 and-0.6294, respectively). The relation between the resorptive and formative processes (R:F) in the bone of unguligrades tends to depend upon the requirements fo

Reliability of Human Subject - Artificial System Interactions

Main problems related to reliability of interaction between human subject and artificial system (namely of the transportation character) are discussed. The paper consists of three mayor parts:The first one is devoted to the theoretical backgrounds of the problem from the both theory of system reliability and neurology/psychology views.Second part presents the discussion of relevant methodologies of the classification and prediction of the reliability decline. The methodology based on EEG pattern analysis is chosen as the appropriate one for the presented task. The key phenomenon of "micro-sleep" is discussed in detail.The last part presents some latest experimental results in context of presented knowledge. Proposals for the future studies are presented at the end of the presented article. The special interest should be devoted to the analysis and in-time prediction of fatal attention decreases and to the design and construction of the respective on-board applicable warning system