Efeito do campo magnético na precipitação de parafinas

In the oil industry, the paraffination phenomenon is a major problem during oil production, displacement and treatment. Paraffin deposition in subsea flowlines, surface equipment, production string or even in the reservoir, can cause significant and increasing oil losses. To minimize paraffin precipitation, the application of magnetic field in the petroleum path has been suggested based on empiric studies. In this study, we assembled a labscale magnetic conditioner to determine the influence of magnetic field on the physical-chemical properties of two fluids : oil and a paraffin mixture. We observed that magnetic field reduce sample aparent viscosity due to crystal morphology alteration.

Íon Be H+ em campo elétrico uniforme intenso

The influence of a strong external electric field in chemical bonding is not extensively studied. In this work, the behavior of the potential energy curves of the BeH+ ion in an external electric field is investigated by means of variational calculations using molecular orbitals. For simplicity we consider the case where the external field is parallel to the molecular axis, in the direction of the dipole moment, which raises the polarization of the ion. The effects on dissociation are investigated.

Relação entre as massas úmida, seca e de cinza em materiais biológicos - uma ferramenta para amostragens em campo e análise de amostras

Little is known about the amount of water and ash in brazilian foodstuffs and plants. The relationships between fresh, dry and ash weight were determined in 40 different biological samples. It could be an important tool when one studies biological material containing low concentration of the chemical elements. This study address to determine these relationships and to provide the amount of biological material that one needs to collect. It aims to supply information that could be used to improve the detection limit, precision and accuracy of the analytical methodology utilized.

RMN 2D: Detecção inversa e gradiente de campo na determinação estrutural de compostos orgânicos

A view of the general aspects involving the 2D NMR spectroscopy using inverse detection and field gradient techniques is presented through the analysis of a sesquiterpene.

Aspectos práticos relacionados ao uso do Rincoforol, o feromônio de agregação da Broca-do-olho-do-coqueiro Rhynchophorus palmarum L. (Coleopterate: Curculionidae) no controle de pragas do coqueiro: análise de sua eficiência em campo

Rhynchophorol (6-Methyl-2-hepten-4-ol) is the major constituent of the aggregation pheromone of Rhynchophorus palmarum L. (Coleoptera: Curculionidae), which is released by males of this species. The racemic mixture has been produced in one step-simplified preparation. The pheromone is placed into ampoules and furnished to coconut farmers. In the field, traps baited with Rhynchophorol and pieces of sugarcane attract both males and females, reducing the population of R. palmarum. The best conditions for field application are showed.

Espectros eletrônicos de alguns complexos de geometria octaédrica de Ni2+: uma introdução prática à teoria do campo cristalino no curso de graduação

The experiment introduces the undergraduate students to the crystal field theory. The electronic spectra of the octahedral complexes of [Ni(L)n]2+ (L = H2O, dmso, NH3 and en) obtained in the experiment are used to calculate 10Dq and B parameters. The experiment shows how the parameters can be calculated and correlated with the nature of the ligands and the field intensities produced.

Construção de campo de força empírico para estudo de complexos de Fe(III) com interesse bioinorgânico

In this work we present a new parametrization in molecular mechanics for studying iron complexes. This force field was implemented in the FORCES 2000 program, developed in our group for studying in coordination compounds of interest in bioinorganic chemistry. Mononuclear and dinuclear iron complexes were studied using this program with good success.

Utilización de software de corrección automática en el campo de las ciencias de la salud

We live in an era of profound changes in university education. The implementation of Bologna plan has led us to raise new teaching methodologies, to review the role of the student, competency assessment, the incorporation of ICT. Unthinkable acts, one or two decade ago. The TIC concept is very broad and is attributed to the media, processes and content usage. Inside the supports and platforms, we stress tools that allow automatic correction of exercises, because they are instruments of great educational value because instantly they assess students and provide instant feedback about the knowledge that they have either as message support or note. If the power of these tools, we add the Internet, using e-learning environment, the results allow us to work, edit, evaluate, resolve doubts, and so on, anywhere, anytime. We present part of a platform and the results of its use in the field of health sciences

Theoremata nonnulla, e latissimo scientiarum mathematicarum campo, collecta

Painovuosi nimekkeestä.

Variações no teor e na composição volátil de Hyptis marrubioides EPL: cultivada no campo e em casa de vegetação

This work describes the chemical composition of the volatile oil of Hyptis marrubioides cultivated in field and greenhouse. The experimental design was completely randomized, with ten replications for each type of cultivation. The volatile oil was extracted by hydrodistillation and analyzed by GC-MS. The highest content of volatile oil was found for plants grown in field. The highest percentage of the compounds present in oils was observed in samples grown in the field, such as germacra-4(15),5,10(14)-trien-1-α-ol (16.34%), β-caryophyllene (10.42%), γ-muurolene (12.83%) and trans-thujone (9.98%). However, some compounds were found only in plants grown in a greenhouse, such as cis-muurol-5-en-4α-ol (10.84%), α-cadinol (3.06%) and eudesma-4(15),7-dien-1β-ol (6.82%).

Abordagem teórico-experimental da teoria do campo cristalino na disciplina de síntese inorgânica

We describe herein the synthesis and characterization of the complexes KNiF3, [Ni(en)3]I2, [Ni(en)3]Cl2, [Ni(acac)2(H2O)2], [Ni(en)2(H2O)2]Cl2 and [Ni(NH3)6](BF4)2 (en = ethylenediamine, acac- = acetylacetonate) performed in the inorganic synthesis major course at the Chemistry Institute of UFRGS (Universidade Federal do Rio Grande do Sul). The compounds were characterized by infrared and electronic spectroscopy and the electrolytic conductivity was measured. The parameters 10Dq and B were obtained from the electronic spectra and the nefelauxetic and spectrochemical series were determined. The obtained spectrochemical series was F- < acac- < NH3 < en and the nefeulaxetic series was en < NH3 < acac- < F-.

Métodos para análises de HPA e BTEX em águas subterrâneas de postos de revenda de combustíveis: um estudo de caso em Campo Grande, MS, Brasil

Two methods using headspace solid-phase microextraction and gas chromatography - mass spectrometry were developed for the determination of polycyclic aromatic hydrocarbons (PAH) and BTEX. Best results were obtained using DVB/CAR/PDMS fiber, with 10 min extraction at 25 °C and 0.15 min desorption at 260 °C (BTEX), and PDMS/DVB fiber, with 60 min extraction at 90 °C, 10% NaCl and 5 min desorption at 270 °C (PAH). LOD intervals were 3x10-2 - 5x10-2 µg L-1 (BTEX) and 1.6x10-3 - 1.4 µg L-1 (PAH). The methods were applied to forty-five groundwater samples from monitoring wells of gas stations and only benzene level exceeded the limit established by Brazilian regulations.

Análise do teor e da qualidade dos lipídeos presentes em sementes de oleaginosas por rmn de baixo campo

To choose among the variety of oleaginous plants for biodiesel production, the oil content of several matrices was determined through different low-field ¹H nuclear magnetic resonance (NMR) experiments with varied pulse sequences, namely single-pulse, spin-echo, CPMG, and CWFP. The experiments that involved the first three sequences showed high correlation with each other and with the solvent extraction method. The quality of the vegetable oils was also evaluated on the basis of the existing correlation between the T2 values of the oils and their properties, such as viscosity, iodine index, and cetane index. These analyses were performed using HCA and PCA chemometric tools. The results were sufficiently significant to allow separation of the oleaginous matrices according to their quality. Thus, the low-field ¹H NMR technique was confirmed as an important tool to aid in the selection of oleaginous matrices for biodiesel production.