Characterization of Buriti (Mauritia flexuosa L.) oil by absorption and emission spectroscopies

Amostras de óleo obtido do fruto do Buriti (Mauritia flexuosa L.) foram caracterizadas por espectroscopia de absorção e emissão. O espectro de absorção foi obtido no intervalo de 300 a 2000 nm, enquanto o espectro de emissão foi analisado entre 400 e 800 nm, onde observamos várias bandas. Para melhor entender a complexidade destes espectros, também obtivemos os espectros de absorção e emissão dos componentes majoritários do óleo de Buriti. Correlacionando estes dados, apresentamos uma discussão sobre a origem das bandas observadas.

Gas Analysis by Absorption

There is practically only one method of gas analysis. This was worked out many years ago by Bunsen, Hempel, and Winkler and consists in the successive absorption with different chemicals of the various constituents of the gas. The only improvement to this method is the oxidation and combustion of different components of a mixture followed by absorption.

CO2 capture by absorption into aqueous tertiary amine solution

The aim of this research is to obtain the absorption rate of CO2 into aqueous solution of N,N- di methyl ethanolamine and into aqueous solution of Triethylene diamine and to demonstrate the importance of absorption of CO2 in nowadays by discussing global warming and greenhouse effect. It is also discussed the current situation of China focusing in the latest steps this country has recently made. In the experimental part of this work, the two tertiary amine solutions will absorb CO2 in a Lewis type cell, measuring the pressure change during the reactions take place. The temperature will be between 35 degree and 70 degree Celsius. The results of both solutions, concentrations of 0.5 and 1.0 mol per liter, are discussed and a single value of the rate constant is given for the first time along with some others parameters.

3D-form metrology of arbitrary optical surfaces by absorption in fluids

We present an imaging technique for the 3D-form metrology of optical surfaces. It is based on the optical absorption in fluids situated between the surface and a reference. An improved setup with a bi-chromatic light source is fundamental to obtain reliable topographic maps. It is able to measure any surface finish (rough or polished), form and slope and independently of scale. We present results focused on flat and spherical optical surfaces, arrays of lenses and with different surface finish (rough-polished). We achieve form accuracies from several nanometers to sub-lambda for sag departures from tens to hundred of microns. Therefore, it seems suitable for the quality control in the production of precision aspheric, freeform lenses and other complex shapes on transparent substrates, independently of the surface finish.

Epidemiología y perdurabilidad empresarial en Colombia: Grupo Éxito

La muerte empresarial es un proceso que se ha venido presentando en compañías de las diferentes industrias a nivel nacional. La causa son los diferentes factores externos que impactan directamente las operaciones y estructura de estas. Con base en lo anterior es importante resaltar que existen diferentes tipos de muerte empresarial que para efectos de este trabajo se encontraron importante referenciar, pues son el marco del análisis de caso sobre Almacenes Éxito S.A. perteneciente al sector retail, donde se buscaba determinar cuál fue el tipo de cesión que tuvo, como consecuencia de la venta de acciones a la Compañía Francesa Casino Guichard-Perrachon S.A. Además del marco teórico empleado, se encontró importante realizar una reseña histórica de las diferentes empresas que han integrado el sector con el fin de entender posibles generalidades que se han venido replicando y que han llevado a la muerte empresarial de importantes compañías. Este trabajo permite la comprensión de las diferentes transformaciones que pueden tener los entes económicos a lo largo de su vida empresarial, no solo con lo que puede entenderse como el cese de operaciones sino también como apertura a nuevas estrategias de crecimiento y expansión.

Antibody-dependent cell-mediated cytolysis of human colon carcinoma cells induced by specific antisera against carcinoembryonic antigen.

Antibody-dependent lymphocyte cytotoxicity against human colon carcinoma cells grown in vitro was demonstrated with rabbit anti-carcinoembryonic antigen (CEA) antisera and normal human lymphocytes. The same antisera produced no tumor cell lysis in a complement-dependent cytotoxicity test. The specificity of the reaction was demonstrated by the inhibition of antibody-dependent lymphocyte cytotoxicity after the addition of increasing amounts of purified CEA to the antiserum and by the fact that only tumor cell lines expressing CEA on their surface were lysed. Antibody-dependent lymphocyte cytotoxicity was also observed against two colon carcinoma cell lines that expressed Blood Group A antigen, using a human serum containing anti-Blood Group A antibodies of the immunoglobulin G class. This reaction was specifically inhibited by absorption with Blood Group A red cells, whereas the anti-CEA-dependent cytotoxicity was not inhibited by absorption with red cells of different blood groups.

Detection of new cross-reacting carcinoembryonic antigen(s) on cultured tumor cells by mixed hemadsorption assay.

Antisera highly specific for carcinoembryonic antigen (CEA) from New Zealand White rabbits and a goat reacted strongly in antibody binding tests with cultured tumor cell lines, irrespective of the ability of the cell lines to produce CEA. The most reactive were colon carcinoma and melanoma cell lines, the former known to produce CEA and the latter not associated with CEA production. The reactivity was not diminished by absorption with perchloric acid extracts of normal lung or spleen, whereas absoprtion with purified CEA preparations abolished the reactivity. Quantitative absorption studies indicated that reactivity against CEA-producing cell lines could be totally removed by absorption with other CEA-producing lines but not with melanoma cell lines. Reactivity against melanoma cell lines could be completely removed by colon carcinoma cells as well as by melanoma cells. Antisera raised against purified CEA, after absorption with extracts of normal lung, still contained two populations of antibodies, one that binds a newly described antigen cross-reacting with CEA which is present on melanoma cells.

Nitric oxide release from the S-nitrosothiol zinc phthalocyanine complex by flash photolysis

The photogeneration of nitric oxide (NO) using laser flash photolysis was investigated for S-nitroso-glutathione (GSNO) and S-nitroso-N-acetylcysteine (NacySNO) at pH 6.4 (PBS/HCl) and 7.4 (PBS). Irradiation of S-nitrosothiol with light (lambda = 355 nm followed by absorption spectroscopy) resulted in the homolytic decomposition of NacySNO and GSNO to generate radicals (GS· and NacyS·) and NO. The release of NO from donor compounds measured with an ISO-Nometer apparatus was larger at pH 7.4 than pH 6.4. NacySNO was also incorporated into dipalmitoyl-phosphatidylcholine liposomes in the presence and absence of zinc phthalocyanine (ZnPC), a well-known photosensitizer useful for photodynamic therapy. Liposomes are usually used as carriers for hydrophobic compounds such as ZnPC. Inclusion of ZnPC resulted in a decrease in NO liberation in liposomal medium. However, there was a synergistic action of both photosensitizers and S-nitrosothiols resulting in the formation of other reactive species such as peroxynitrite, which is a potent oxidizing agent. These data show that NO release depends on pH and the medium, as well as on the laser energy applied to the system. Changes in the absorption spectrum were monitored as a function of light exposure.

Absorption and fluorescence of Er3+-doped LiYF4: Measurements and simulation

Er3+:LiYF4 single crystal has been studied by absorption and fluorescence spectroscopy in the IR-visible-UV (0-44000 cm-1) region from 4.2 K to room temperature. Polarized spectra were recorded in order to assign numerous Stark levels of electronic transitions mentioned but not attributed before in the related literature and to discuss the irreducible representations (irreps) of the 4I15/2 sublevels. A parametric hamiltonian, including free ion (Eν, α, β, γ, Tλ, ζ, Mk and Pi) and crystal field parameters (B2 0, B4 0, B4 4, B6 0 and B6 4) in an approximate D2d symmetry for the rare earth site in this scheelite type structure, was used to simulate 109 energy positions of the Er ion with a r.m.s. standard deviation of 14.6 cm-1. A comparison with previously published results for Nd3+ in the same matrix is done. © 1998 Elsevier Science S.A.

Temperature of solar cells with regard to photoactive and non-photoactive light absorption in concentrator PV modules

A new method has recently been proposed by us for accurate measurement of the solar cell temperature in any operational regime, in particular, at a maximum power point (MPP) of the I-V curve (T-p-n(MPP)). For this, fast switching of a cell from MPP to open circuit (OC) regime is carried out and open circuit voltage V-oc is measured immediately (within about 1 millisecond), so that this value becomes to be an indicator of T-p-n(MPP). In the present work, we have considered a practical case, when a solar cell is heated not only by absorption of light incident upon its surface (called "photoactive" absorption of power), but also by heat transferred from structural elements surrounding the cell and heated by absorption of direct or diffused sunlight ("non-photoactive" absorption of power with respect to a solar cell). This process takes place in any concentrator module with non-ideal concentrators. Low overheating temperature of the p-n junction (or p-n junctions in a multijunction cell) is a cumulative parameter characterizing the quality of a solar module by the factor of heat removal effectiveness and, at the same time, by the factor of low "non-photoactive" losses.

Differential distribution of two ATP-gated channels (P2X receptors) determined by immunocytochemistry.

Several P2X receptor subunits were recently cloned; of these, one was cloned from the rat vas deferens (P2X1) and another from pheochromocytoma (PC12) cells differentiated with nerve growth factor (P2X2). Peptides corresponding to the C-terminal portions of the predicted receptor proteins (P2X1 391-399 and P2X2 460-472) were used to generate antisera in rabbits. The specificities of antisera were determined by staining human embryonic kidney cells stably transfected with either P2X1 or P2X2 receptors and by absorption controls with the cognate peptides. In the vas deferens and the ileal submucosa, P2X1 immunoreactivity (ir) was restricted to smooth muscle, whereas P2X2-ir was restricted to neurons and their processes. Chromaffin cells of the adrenal medulla and PC12 cells contained both P2X1- and P2X2-ir. P2X1-ir was also found in smooth muscle cells of the bladder, cardiac myocytes, and nerve fibers and terminals in the superficial dorsal horn of the spinal cord. In contrast, P2X2-ir was observed in scattered cells of the anterior pituitary, neurons in the hypothalamic arcuate and paraventricular nuclei, and catecholaminergic neurons in the olfactory bulb, the substantia nigra, ventral tegmental area, and locus coeruleus. A plexus of nerve fibers and terminals in the nucleus of the solitary tract contained P2X2-ir. This staining disappeared after nodose ganglionectomy, consistent with a presynaptic function. The location of the P2X1 subunit in smooth muscle is consistent with its role as a postjunctional receptor in autonomic transmission, while in neurons, these receptors appear in both postsynaptic and presynaptic locations.

Absorption Measurements of Periodically Poled Potassium Titanyl Phosphate (PPKTP) at 775 nm and 1550 nm

The efficient generation of second-harmonic light and squeezed light requires non-linear crystals that have low absorption at the fundamental and harmonic wavelengths. In this work the photo-thermal self-phase modulation technique is exploited to measure the absorption coefficient of periodically poled potassium titanyl phosphate (PPKTP) at 1,550 nm and 775 nm. The measurement results are (84 +/- 40) ppm/cm and (127 +/- 24) ppm/cm, respectively. We conclude that the performance of state-of-the-art frequency doubling and squeezed light generation in PPKTP is not limited by absorption.

Comparison of some theoretical models for fittings of the temperature dependence of the fundamental energy gap in GaAs

In this work we report on a comparison of some theoretical models usually used to fit the dependence on temperature of the fundamental energy gap of semiconductor materials. We used in our investigations the theoretical models of Viña, Pässler-p and Pässler-ρ to fit several sets of experimental data, available in the literature for the energy gap of GaAs in the temperature range from 12 to 974 K. Performing several fittings for different values of the upper limit of the analyzed temperature range (Tmax), we were able to follow in a systematic way the evolution of the fitting parameters up to the limit of high temperatures and make a comparison between the zero-point values obtained from the different models by extrapolating the linear dependence of the gaps at high T to T = 0 K and that determined by the dependence of the gap on isotope mass. Using experimental data measured by absorption spectroscopy, we observed the non-linear behavior of Eg(T) of GaAs for T > ΘD.

Molybdenum-containing proteins from Sulphate Reducing Bacteria: studying proteins with novel cofactors and revealing new features of old enzymes

Dissertação apresentada para a obtenção do Grau de Doutor em Bioquímica, especialidade de Bioquímica-Física pela Universidade Nova de Lisboa, Faculdade de Ciências e Tecnologia

Estratégia de centralização de compras e minimização de custos estudo de caso do Grupo Pinto & Cruz

Trabalho de Projeto apresentado ao Instituto de Contabilidade e Administração do Porto, para a obtenção do grau de Mestre em Auditoria, sob orientação de Doutora Alcina Dias