Photoinhibition in vivo and in vitro involves weakly coupled chlorophyll-protein complexes

In the present study the analysis of the relation between the excited state population in the photosystem II (PSII) antenna and photoinactivation has been extended from an in vitro system, isolated thylakoids, to an in vivo system, Chlamydomonas reinhardtii cells. The results indicate that the excited state quenching by an added singlet quencher induces maximal protection against photoinhibition of about 30% of that expected on the basis of the observed light intensity-treatment time reciprocity rule. Similar results, obtained previously with thylakoids, have been interpreted in terms of damaged or incorrectly assembled complexes that play an important role in photoinhibition in the thylakoid membranes (Santabarbara, S., K. Neverov, F. M. Garlaschi, G. Zucchelli and R. C. Jennings [2001] Involvement of uncoupled antenna chlorophylls in photoinhibition in thylakoids. FEBS Lett. 491, 109-113.). In an attempt to better define this aspect, the photoinhibition action spectra were determined for mutant barley thylakoids, lacking the chlorophyll (Chl) a-b complexes of the outer antenna, and for its wild type. The results indicate that in both systems the action spectra are significantly blueshifted (2-4 nm) and are broader than the PSII absorption in the membranes. These data are interpreted in terms of a heterogeneous population of outer and inner antenna pigment-protein complexes that contain significant levels of uncoupled Chl.     

Springback compensation in deep drawing applications

This work deals with the problem of springback compensation in sheet metal forming. Satisfactory results can be achieved by performing “die compensation”: the die is modified pretending to obtain a different configuration at the end of the punch stroke, but in order that the final piece coincides with the desired one after the deformation due to springback. Empirical die compensation has nowadays been replaced by numerical simulation, but the inverse problem that needs to be solved is non-trivial since the transformation from the modified geometry of the die and the final piece obtained from it implies a very complex FEM simulation. In this work we set the whole process of springback compensation on solid physical and mathematical grounds. An optimization algorithm based on the Gauss-Newton method is proposed to deliver automatic die compensation and its performance is investigated on some test cases.     

Application of XANES spectroscopy to investigate Sb species in corroded bullets crust material oriented to evaluate the potential toxic effects in the environment

Lead, antimony, and other toxic metals from pellets alloy are dispersed in the soil of the shooting fields. As long as the corroding bullets are present in soil, secondary Pb and Sb phases appear in the weathering crusts being an important source of bioavailable Pb and Sb. Knowledge about the corrosion mechanism of Sb from the bullet is limited, and reports on Sb speciation in crust and soils are still scarce. Considering that Sb species have different toxicological properties in the environment, this work has focused attention in X‐ray Absorption Near Edge Structure measurements at the Sb L‐edges in order to identify its chemical speciation in crust (Sb(0), Sb(III), and Sb(V)). X‐ray Absorption Near Edge Structure measurements were carried out at the D04A Soft X‐ray Spectroscopy beamline at the LNLS. Samples consisted of dust crust taken from physically deformed and strongly corroded metallic bullets retained in soil samples sieving from shooting fields of the North and East region of Córdoba, Argentina. The results showed that the main species found in all samples were Sb(V)(Sb₂O₅) followed by Sb(0) (metallic). Sb(III) was not observed, and it is known that Sb(III) is more toxic than Sb(V). The results suggested that in these environmental conditions, pentavalent Sb was the predominant species after weathering of metallic Sb from corroding bullets.     

Activated carbon obtained from sapelli wood sawdust by microwave heating for o-cresol adsorption

Research on Chemical Intermediates - Activated carbon (AC) was prepared from sapelli wood sawdust using a microwave heating process. The biomass was mixed with inorganic components...     

Synthesis of Some Functionalized Peptomers via Ugi Four-Component Reaction

This article describes the synthesis of new peptomers through a simple and efficient route using a one-pot Ugi four-component reaction. The synthesis started from either carboxylic acids or protected amino acids, primary amines, aldehydes, and isocyanides in anhydrous methanol and proceeded under stirring at room temperature. The reaction produced several functionalized peptomers in good yields (67–80%). These compounds are versatile multifunctional intermediates that can be further unprotected or functionalized to generate new molecules with numerous applications in the field of biomedicine.