Avaliação Da Produção De Látex Em Mangabeiras Do Cerrado Goiano

The mangabeira latex, plant native from Cerrado, shows biotechnological potential for the development of new drugs. Little is known about the latex productivity and bleeding methods in mangabeira, which is usually utilized in extractive way for fruit production. Aiming to broaden our knowledge about mangabeira latex production we evaluate the productivity associated with bleeding methods; environmental conditions; anatomical aspects from the bark and seasonal properties. As results we observed that the bleeding method commonly used in rubber tree is not appropriated to mangabeira; the most productive bleeding method was using a knife in stalk region. The bark thickness and lactiferous vessels number are associated with latex production. Anatomical analysis showed that the bark in mangabeira is thick and the lactiferous vessels are deeply localized, in this way some superficial bleeding methods are not able to reach the vessels. It was also observed that the increase in environmental temperature has a positive influence on the productivity of latex and that during the fruiting time the latex production is significantly lower. This probably occurs because the plant uses part of the secondary metabolites for fruit formation, which reduced the availability of these metabolites to latex production. © 2016, Universidade Federal de Santa Maria. All rights reserved.26393994

High field high frequency EPR spectroscopy on synthetic melanin On the origin of carbon centered radicals

Among all the pigments found in nature, melanin has drawn considerable attention for bioelectronics applications as it contains a set of physicochemical properties such as antioxidant activity, metal chelation, biocompatibility, broad band absorbance throughout the UV visible region, hydration dependent conductivity and intrinsic and extrinsic free radical character. A better understanding of these properties is a matter of significant importance to improve melanin based organic devices efficiently. Therefore, the origin of melanin free radicals was studied using continuous wave electron paramagnetic resonance EPR spectroscopy at 263 GHz for standard non functionalized and sulfonated derivatives. Our results indicated that more than one radical species should be evoked to study the free radical nature of standard and sulfonated melanin. Additionally, we also confirm that the free radical system of sulfonated melanin is similar to non functionalized melanin. Based on the g anisotropy analysis, we propose which potential units could be responsible for carbon centered radical

Spin Dependent Photoconductivity In Hydrogenated Amorphous Silicon Germanium Alloys

We use spin-dependent photo-conductivity (SDPC) to study the recombination process of photo-excited carriers in hydrogenated amorphous silicon germanium alloys (a-SiχGe1-χ:H). The incorporation of Ge is marked by a sudden change in the SDPC signal (-Δσ/σ) from (a-Si:H)-like to (a-Ge:H)-like. The Ge atoms create new states which dominate transport and recombination of photo-created free carriers. In particular, the SDPC lineshape analysis indicates that the a-Si:H conduction band tail is affected by alloying with small concentrations of germanium. © 1993.164-166PART 11518Aljishi, Smith, Wagner, (1988) Amorphous Silicon and Related Materials, p. 887. , H. Fritzsche, World Scientific, SingaporeNebel, Schubert, Weller, Bauer, Bloss, (1988) Proc. 8th EC PVSEC, p. 919. , Reidel, DordrechtStutzmann, Street, Tsai, Boyce, Ready, (1989) J. Appl. Phys., 66 (2), p. 569Dersch, Schweitzer, Stuke, (1983) Phys. Rev. B, 28, p. 4678Movaghar, Ries, Schweitzer, Theory of the resonant and non-resonant luminescence changes in amorphous silicon (1980) Philosophical Magazine Part B, 41, p. 141Movaghar, Ries, Schweitzer, Theory of the resonant and non-resonant photoconductivity changes in amorphous silicon (1980) Philosophical Magazine Part B, 41, p. 159de O. Graeff, Santos, Marcano, Chambouleyron, (1990) Proc 21th IEEE PVSC, p. 1564. , IEEE, New YorkStutzmann, Biegelsen, (1983) Phys. Rev. B, 28, p. 6256C.F.O. Graeff, M.S. Brandt, and M. Stutzmann, unpublishedStreet, Tsai, Stutzmann, Kakalios, (1987) Phil. Mag. B, 56, p. 28

Hirsch's index: a case study conducted at the Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo

An analysis of scientific bibliographic productivity using the Hirsch h-index, information from the Institute of Scientific Information database and the Curriculum Lattes (CNPq, Brazil) was performed at the Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo (FFCLRP-USP) that has four departments in natural, biological and social sciences. Bibliometric evaluations of undergraduate programs showed a better performance of the departments of Chemistry (P < 0.001) and Biology (P < 0.001) when compared to the departments of Physics and Mathematics and Psychology and Education. We also analyzed the scientific output of the six graduate programs of FFCLRP: Psychology, Psychobiology, Chemistry, Physics Applied to Medicine and Biology, Comparative Biology, and Entomology. The graduate program in Psychology presented a lower h-index (P < 0.001) and had fewer papers indexed by the ISI web of science (P < 0.001) when compared to the other graduate programs. The poorer performance of the Psychology program may be associated with the limited coverage by the Thompson Institute of Scientific Information database

Thin Films Of Synthetic Melanin

We have developed a new synthetic route to melanin, using different organic solvents, namely dimethyl sulfoxide and N,N-dimethyl formamide. Contrary to conventional water based melanin thin films can be made with organic solvents. Thin films were made either by room temperature solvent evaporation (casting) or using spin coating. X-ray diffraction, thermogravimetry, infrared transmission spectroscopy, UV-VIS transmission spectroscopy, electron spin resonance, atomic force microscopy (AFM) and temperature dependent conductivity have been used to characterize the material obtained. The new synthetic material is found to be similar to melanin made in water, however with an increase in thermal stability. AFM results shows that the thin films are made of graphitic-like planar structures, with root mean square roughness of ~0.3 nm, separated by steps ranging from 1 to 3 nm in height. These sheets have lateral extensions of several microns, which make this new material potentially interesting as a 2D organic polymer. © 2004 Elsevier B.V. All rights reserved.338-3401 SPEC. ISS.634638Prota, G., (1992) Melanins and Melagenesis, , San Diego: AcademicZajac, G.W., Gallas, J.M., Cheng, J., Eisner, M., Moss, S.C., Alvarado-Swaisgood, A.E., (1994) Biochim. Biophys. Acta, 1199, p. 271Nofsinger, J.B., Forest, S.E., Eibest, L.M., Gold, K.A., Simon, J.D., (2000) Pig. Cell Res., 13, p. 179Clancy, C.M.R., Simon, J.D., (2001) Biochemistry, 40, p. 13353Gonçalves, P.J., Brunello, C.A., Graeff, C.F.O., (2002) Molec. Cryst. Liq. Cryst., 374, p. 39Oliveira, H.P., Graeff, C.F.O., Zanta, C.L.P.S., Galina, A.C., Gonçalves, P.J., (2000) J. Mater. Chem., 10, p. 371Bernier, P., Lefrante, S., Bidan, G., (1999) Advances in Synthetic Metals: Twenty Years of Progress in Science and Technology, , Lausanne: ElsevierJastrzebska, M., Kocot, A., Tayber, L., (2002) J. Photochem. Photobiol. B, 66, p. 20

Abnormal resistive switching in electrodeposited Prussian White thin films

Prussian White (PW) layers were deposited on Au/Cr/Si substrates by electrodeposition and characterized by different techniques. Scanning electron microscopy (SEM) images and Raman mapping reveal a uniform and homogeneous deposit while scanning transmission electron microscopy (STEM) images disclose the grain boundary pattern and the thickness of 300 nm of the PW layer. Resistive switching (RS) effect with an ON/OFF ratio of about 102 was observed. The RS mechanism was investigated from the log-log currentvoltage plots. Ionic conduction was observed with an activation energy of 0.4 eV that could be associated with potassium ions as possible charge carriers at the grain boundaries. The endurance characteristics were investigated and a stable abnormal RS was observed for consecutive 500 cycles. Moreover, the retention was also evaluated and the high resistive state (HRS) and low resistive state (LRS) were stable up to 1000 s.The authors acknowledge TESCAN, Zeiss, and WITec for assis-tance during electron microscopy and Raman imaging of the samples and LCME/UFSC for the EDS measurements (LCME-MAT-2021) . We thank D. Hildebrand for his technical assistance. This research was supported by the funding agencies: CNPQ, FINEP, CAPES (finance code 001) , DAAD (project 249302) , FAPESP (process 2013/07296, 2017/20809-0, 2020/04721-8) , and the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding Contract UIDB/04650/2020

Synthesis of Main-Chain Poly(fullerene)s from a Sterically Controlled Azomethine Ylide Cycloaddition Polymerization

International audienceFullerene is used as a monomer in this simple method to prepare soluble, well-defined polymers. The sterically controlled azomethine ylide cycloaddition polymerization of fullerene (SACAP) yields macromolecules with molecular weights of around 25 000 g mol-1. Importantly, cumbersome comonomers are employed to restrict cross-linking. Extensive characterizations, with the help of modeling studies, indicate that the polymers are regio-irregular with a majority of trans-3 isomers. Of particular interest is the exceptional ease of preparing polymers with zero metal content. © 2016 American Chemical Society

Increased thermal stabilization of polymer photovoltaic cells with oligomeric PCBM

International audienceThe first oligomerisation of phenyl-C61-butyric acid methyl ester (PCBM) using a facile atom transfer radical addition polymerization (ATRAP) and its exploitation for organic photovoltaic devices is described. Oligo\(phenyl-C61-butyric acid methyl ester)-alt-[1,4-bis(bromomethyl)-2,5-bis(octyloxy)benzene]\ (OPCBMMB) shows opto-electronic properties equivalent to those of PCBM but has a higher glass transition temperature. When mixed with various band gap semiconducting polymers, OPCBMMB delivers performances similar to PCBM but with an enhanced stabilization of the bulk heterojunction in photovoltaic devices on plastic substrates under thermal stress, regardless of the degree of crystallinity of the polymer and without changing opto-electronic properties. © 2016 The Royal Society of Chemistry