Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto

About: Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto is a based out in . It is known for research contribution in the topics: Population & Genus. The organization has 2143 authors who have published 3674 publications receiving 71071 citations. The organization is also known as: FFCLRP & FFCLRP-USP.

Tomotherapy dose distribution verification using MAGIC-f polymer gel dosimetry

Abstract: Purpose: This paper presents the application of MAGIC-f gel in a three-dimensional dose distribution measurement and its ability to accurately measure the dose distribution from a tomotherapy unit. Methods: A prostate intensity-modulated radiation therapy (IMRT) irradiation was simulated in the gel phantom and the treatment was delivered by a TomoTherapy equipment. Dose distribution was evaluated by the R2 distribution measured in magnetic resonance imaging. Results: A high similarity was found by overlapping of isodoses of the dose distribution measured with the gel and expected by the treatment planning system (TPS). Another analysis was done by comparing the relative absorbed dose profiles in the measured and in the expected dose distributions extracted along indicated lines of the volume and the results were also in agreement. The gamma index analysis was also applied to the data and a high pass rate was achieved (88.4% for analysis using 3%/3 mm and of 96.5% using 4%/4 mm). The real three-dimensional analysis compared the dose-volume histograms measured for the planning volumes and expected by the treatment planning, being the results also in good agreement by the overlapping of the curves. Conclusions: These results show that MAGIC-f gel is a promise for tridimensional dose distribution measurements.

Extracellular tannase from Emericella nidulans showing hypertolerance to temperature and organic solvents

Abstract: The filamentous fungus Emericella nidulans (=Aspergillus nidulans) produced high levels of extracellular tannase when grown at 30 °C, under agitation (100 rpm), for 24 h in Khanna medium supplemented with tannic acid as carbon source. The enzyme was purified 61-fold, with 30% yield. The molecular mass of the native protein was estimated to be 302 kDa by gel filtration, with a carbohydrate content of 50%. Two protein bands (45.8 and 52 kDa) were observed after 12% SDS–PAGE, suggesting a glycoprotein constituted by three copies of each subunit. The extracellular tannase showed temperature and pH optima of 45 °C and 5.0, respectively, and was fully stable in the temperature range of 22–50 °C, with a half-life (t50) of about 72 h at 90 °C. The enzyme retained around 80% of control activity when maintained for 60 h at pH 4.0 or 5.0. Tannase activity was stimulated by Zn2+, Hg2+, Co2+, and the detergents SDS and Triton X-100. Organic solvents (about 50%, v/v) also increased enzyme activity, particularly isopropanol, acetonitrile, and ethanol. The Km and Vmax values were 14.01 mM and 2.63 U mg−1 protein in the presence of tannic acid; and 4.78 mM and 0.29 U mg−1 protein in the presence of methyl gallate. For propyl gallate, the Vmax was 0.05 U mg−1 protein, with Km of 7.69 mM; for pyrogallol, the Vmax was 7.40 U mg−1 protein and the Km was 16.94 mM.

Excited-state absorption investigation of a cationic porphyrin derivative

Abstract: This work presents a complete investigation on the excited-state absorption of a new porphyrin derivative, the free-base 5,10,15,20-tetrakis (1,3-dimethylimidazolium-2-yl) porphyrin tetraiodide (H 2 -TDMImP), for which the excited singlet and triplet transient absorption spectra were obtained. In order to accomplish this task, we employed the laser flash photolysis (LFP) technique in association with the white-light continuum (WLC) Z-scan measurements. The transient singlet absorption spectrum shows a reverse saturable absorption around the Q-band region (500–650 nm) and a small saturable absorption around 650 nm. From LFP experiments we verified that this porphyrin presents a biexponential decay profile, with a low quantum yield for triplet state formation. Besides, we observed that the reverse saturable absorption also takes place in triplet state.