Recaltech (Brazil)

Transient upstream mesoscale structures (TUMS) are an important topic in the field of research of the near-Earth environment. These events form upstream of the Earth's bow shock and can perturb regions downstream it, i.e. magnetosheath and magnetopause. They can even affect the magnetosphere and ionosphere causing a range of space weather phenomena during periods without noticeable solar activity. There is still much to learn about the TUMS and the way they interact with the near-Earth environment. We are only beginning to understand how the different types of the TUMS relate to each other. In the past it has been shown that traveling foreshocks may contain foreshock cavitons, spontaneous hot flow anomalies and foreshock compressional boundaries (FCB). Here we present the first evidence, that traveling foreshocks may be bounded on at least one of their edges by hot flow anomalies (HFA) and by events that look like hybrids between HFAs and FCBs. We show two case studies observed by the Cluster and MMS constellations. Such studies enable us to better understand all the ways in which the solar-terrestrial interactions occur.

Dataset and source code for the paper "Correlations in the elastic Landau level of a graphene/NbSe2 van der Waals heterostructure"

A central composite experimental design leading to a set of 16 experiments with different combinations of pH and temperature was performed to attain the optimal activities of xylose reductase (XR) and xylitol dehydrogenase (XDH) enzymes from Candida mogii cell extract. Under optimized conditions (pH 6.5 and 38 degrees C), the XR and XDH activities were found to be 0.48 U/ml and 0.22 U/ml, respectively, resulting in an XR to XDH ratio of 2.2. Stability, cofactor specificity and kinetic parameters of the enzyme XR were also evaluated. XR activity remained stable for 3 h under 4 and 38 degrees C and for 4 months of storage at -18 degrees C. Studies on cofactor specificity showed that only NADPH-dependent XR was obtained under the cultivation conditions employed. The XR present in C. mogii extracts showed a superior Km value for xylose when compared with other yeast strains. Besides, this parameter was not modified after enzyme extraction by aqueous two-phase system.

The enzymatic synthesis of selected low molecular weight esters such as acetate esters by direct esterification using acetic acid as acyl donor usually display low yields. The acetic acid changes the polarity of the reaction medium, which in this turn modifies the partitioning of water between the solid phase (enzyme preparation) and the liquid phase (substrate), resulting in its accumulation on the enzyme solid phase. This may reduce the enzyme´s local pH. Therefore, the enzyme active site is modified and the reaction became nearly impossible. Our previous work showed that there is a negative relationship between enzyme activity and substrate partition coefficient (Ps); that is, the higher the substrate partition coefficient the lower the amount of product formed. This work investigated the feasibility of minimizing this inhibition by replacing the esterification reaction for alcoholysis reaction using several acetate esters. This approach enhanced the reaction yields to 46%, which is about 3 times higher than that one obtained in the esterification route.

Rice straw was used as a lignocellulosic source to provide rich pentose media. By using a well characterized yeast strain,Candida guilliermondii FTI 20037, the hydrolysate obtained was converted to xylitol with an efficiency of 75% and production of 27 g of xylitol per liter in 48 hours. The satisfactory results reported here can be attributed to the low concentrations of toxic components generated throughout the chemical depolymerization of this raw material.