Effect of discontinuity size on the energy absorption of structural steel beam profiles

The effect of size discontinuities on the energy absorption performance of squared steel profiles is reported. Finite element simulations of the compression strength of profiles with discontinuities, placed at mid span of the steel profiles in two opposite walls, were carried out. Circular and elliptical forms of the discontinuities were evaluated. Energy absorption capabilities were increased up to 12.54% and the peak load value was decreased to 10.52% with respect to the same structure without discontinuities. A buckling effect is observed in structures with discontinuities, which contributes to reducing the peak value while the energy absorbing characteristics decrease.     

Possible causes for the instability in the H2 production from cheese whey in a CSTR

A CSTR reactor was operated for 30 days. It was fed with raw cheese whey with an organic loading rate of 30 gCOD/Ld. Hydrogen production varied significantly with a maximum of 0.9 LH₂/Ld and decreased after 17 days of operation. The causes of production instability were analysed using different microbiological tools. It was concluded that this decrease was not due to the incapacity to select hydrogen-producing organisms, as shown by the persistence of the Fe-hydrogenase genes in the reactor. Using a molar balance, it was estimated that more than 30% of the acetic production can be due to the homoacetogenesis pathway, although genes from homoacetogenic microorganisms were detected at a very low concentration. The different effects of enhancement and inhibition of hydrogen production by the lactic acid bacteria and their high abundance variation could explain the instability of hydrogen production in this reactor.     

Effects of genetic polymorphisms CYP1A1, GSTM1, GSTT1 and GSTP1 on urinary 1-hydroxypyrene levels in sugarcane workers

Sugarcane workers in Brazil are exposed to various genotoxic compounds, including polycyclic aromatic hydrocarbons (PAHs), derived from an incomplete combustion process of burnt sugarcane fields. The effects of the occupational exposure to sugarcane fields burning were measured in urine samples of sugarcane workers from the northwest of the State of S?o Paulo when exposed (harvesting) and when non-exposed (non-harvesting). The urinary levels of 1-hydroxypyrene (1-OHP) and the influence of the genetic polymorphisms CYP1A1, GSTM1, GSTT1 and GSTP1 were evaluated. Our results showed that the 1-OHP levels were significantly higher (P<0.0000) in the exposed sugarcane workers (0.318 mumol mol(-1) creatinine) than in the non-exposed workers (0.035 mumol mol(-1) creatinine). In an unvaried analysis, no influence regarding the polymorphisms was observed. However, multivariate regression analysis showed that the CYP1A1()4 polymorphism in the exposed group, and age and the GSTP1 polymorphism in the non-exposed group significantly influenced urinary 1-OHP excretion levels (P<0.10). The same group of sugarcane workers was significantly more exposed to PAHs during the harvesting period than during the non-harvesting period.