Sediments accretion at Guarapiranga reservoir,metropolitan region of São Paulo,Brazil, by the 210Pb chronological method

Journal of Radioanalytical and Nuclear Chemistry - The Constant Flux: Constant Sedimentation (CF:CS) and Constant Rate of Supply (CRS) of unsupported/excess 210Pb models have been applied to a...     

Evidence for the quantum birth of our universe

We present evidence for a nonsingular origin of the Universe with intial conditions determined by quantum physics and relativistic gravity. In particular, we establish that the present temperature of the microwave background and the present density of the Universe agree well with our predictions from these intial conditions, after evolution to the present age using the Einstein-Friedmann equation. Remarkably, the quantum origin for the Universe naturally allows its evolution at exactly the critical density. We also discuss the consequences of these results to some fundamental aspects of quantum physics in the early Universe.     

Thermal investigation of oil and biodiesel from <Emphasis Type="Italic">Jatropha curcas</Emphasis> L.

Biodiesel is susceptible to autoxidation if exposed to air, light and temperature, during its storage. Physic nut (Jatropha curcas L.) seeds show potential application for biodiesel production since its oil yields high quality biodiesel. This work aims to evaluate the thermal behavior of the physic nut oil and biodiesel, from several Brazilian crops, by means of thermoanalytical techniques. Thermogravimetry (TG) and pressurized-differential scanning calorimetry (PDSC) were used in order to determine the applicability of physic nut biodiesel as fuel. Results suggest that physic nut biodiesel is a practical alternative as renewable and biodegradable fuel able to be used in diesel motors.     

Study of the conformation of γ-zeins in purified maize protein bodies by FTIR and NMR spectroscopy

The γ-zeins are a mixture of 16, 27, and 50-kDa polypeptides which are important in the formation and stabilization of protein bodies (PB). These organelles are used for deposition of zeins, the water-insoluble storage proteins in maize. The nature of the physical interaction between proteins in the assembly and stabilization of PB are fairly well known. It is suggested the repeated hexapeptide sequence (PPPVHL)₈ in the N-terminus is responsible for aggregation of the γ-zeins on the PB surface. Despite this importance, there is little information about the native conformation of γ-zeins. In this work, we have analyzed the secondary structures of γ-zeins in purified protein bodies from two maize cultivars, in the solid state, by FTIR and NMR spectroscopy. The results revealed that γ-zeins in their physiological state are comprise similar proportions of α-helix and β-sheet, 33 and 31% as determined by FTIR. It was not possible to state if the polyproline II (PPII) conformation is present in the solid-state structure of γ-zeins, as has been demonstrated for the hexapeptide in solution. Because of the similarity of the solid-state NMR spectra of γ and α-zeins in the α carbon region we attributed their contributions to the β-sheet structures rather than to the PPII conformation or a mixture of these extended structures.     

Influence of the storage on the thermo-oxidative stability of methyl and ethyl esters by PDSC

Biodiesel oxidation is a complex process widely influenced by the chemical composition of the biofuel and storage conditions. Several oxidation products can be formed from these processes, depending on type and amount of the unsaturated fatty acid esters. In this work, fatty acid methyl and ethyl esters were obtained by base-catalyzed transesterification of soybean oil and physicochemically characterized according to standards from ASTM, EN, and ABNT. The thermal and oxidative stabilities of biodiesel samples were investigated during the storage process by pressure differential scanning calorimetry (PDSC) and by viscosity measurements. Absolute viscosities of biodiesels after accelerated aging were also determined. The viscosity increased as the aging temperature and time were raised. The results showed that oxidation induction can occur during storage, decreasing the biodiesel stability. PDSC analysis showed that during storage under climate simulation the values of high-pressure oxidative induction times (HPOIT) were reduced for both FAEE and FAME.     

Research on mathematics education

This study addresses aspects that should be considered in every investigation concerning the reality of the subject being investigated, which in turn provide the basis for the procedures adopted to carry out the research. It speaks about the analysis of the procedures chosen to carry out the research. It is assumed that this care should be taken by the researcher at the moment the research procedures are being defined and made explicit. It is argued that the consonance between the ontological and epistemological dimensions of “what” and “how” to investigate the subject of investigation confers a degree of confidence to the research findings. The search for that confidence transcends analyses based only on calculations and explanations of methodological procedures, regardless of how well founded they are. This study addresses mathematics education specifically, adopting a phenomenological perspective. It is focused on the constitution of mathematical idealities and of mathematics as a science under the perspective of the Husserlian phenomenological conception of reality and knowledge. Characteristics of a phenomenological pedagogy are presented, which is carried out through work that is always intentional, with the educator taking account of what occurs with himself/herself, with the life world of the school, and with the student. The student is seen as a person and as being with others, his/her classmates, and the theme is addressed in the context of the field of inquiry under focus, with the teacher and with his/her “surroundings”.     

Thermo-oxidative stability and cold flow properties of babassu biodiesel by PDSC and TMDSC techniques

The babassu (Orbignya Phalerata Mart.) biodiesel has lauric esters as main constituents, resulting in high oxidative stability and low cloud and freezing points. In order to reduce these side effects, the saturated ethyl esters content was reduced by means of winterization process. The TMDSC and PDSC techniques were used to verify the thermal and oxidative stabilities of the ethyl babassu biodiesel. During the heating stage, the winterized solid phase of ethyl esters presented an endothermic transition associated to the solidification process. This behavior was not observed for the liquid winterized FAEE, confirming the efficiency of the winterization process.     

Isolation and Characterisation of (5R, 6S,5′R,8′R)- and (5R,6S,5′R,8′S)-Luteochrome from Brazilian Sweet Potatoes (Ipomoea batatas LAM.)

Luteochrome isolated from the tubers of a white-fleshed variety of sweet potato (Ipomoea batatas LAM .) has been shown by HPLC, ¹H-NMR and CD spectra to consist of a mixture of (5R,6S,5′R,8′R)- and (5R,6S,5′R,8′S)- 5,6:5′,8′-diepoxy-5,6,5′,8′-tetrahydro-β,β-carotene ( 1 and 2 , resp.). Therefore, its precursor is (5R,6S,5′R,6′S)-5,6:5′,6′-diepoxy-5,6,5′,6′-tetrahydro-β,β-carotene ( 4 ). This is the first identification of luteochrome as a naturally occurring carotenoid and, at the same time, gives the first clue to the as yet unknown chirality of the widespread β,β-carotene diepoxide. These facts demonstrate that the enzymic epoxidation of the β-end group occurs from the α-side, irrespective of the presence of OH groups on the ring.     

Rheology and MT-DSC studies of the flow properties of ethyl and methyl babassu biodiesel and blends

The synthesis of pigments from the system Ce_1−x O₂–M _x O (M = Cu, Co) was achieved via a polymeric precursors method, Pechini method. Differential scanning calorimetry (DSC) and thermogravimetry (TG) techniques were used to accurately characterize the distinct thermal events occurring during synthesis. The TG and DSC results revealed a series of decomposition temperatures due to different exothermal events, which were identified as H₂O elimination, organic compounds degradation, and phase formation. X-Ray diffraction patterns show the presence of pure cubic CeO₂ phase for the samples with low Cu and Co loading. A decrease of the specific surface area with increasing copper and cobalt content was observed. The UV–visible diffuse reflectance technique was employed to study the optical properties in the 200–800 nm range. Colorimetric coordinates L*, a*, b* were calculated for the pigment powders. The powders presented a variety of colors from yellow for pure CeO₂, to brown for the ones loaded with copper and gray for the ones with cobalt.