Análise dos riscos físicos e ergonômicos em roçadora transversal motorizada

According to Statistical Yearbook of Social Security (2011), the number of accidents at work recorded in the agricultural sector is quite high, in the year 2010 there are records of thirty-four thousand nine hundred and ninetysix accidents, and in the year of 2011 there were thirty-one thousand and ninety-six accidents in the industry. Among so many diseases and accidents at work hearing loss is one of them. According to the Pan American Health Organization (2011) the Occupational hearing loss is then jury to the worker's health, often in the workplace. Mechanical vibrations are also present in many human activities exposing employees to an extremely aggressive agent. The combined action of these two factors can cause damage to the health of the worker, in this way, noise and vibration are the two major occupational agents present in the brush cutter operator activity. In the case there is another risk factor, the open work, which exposes the employee to the Sun’s rays and the high temperature indices. Studies have shown that: noise exceeds 115 dB (A) vibration 4.0 m/s2 and thermal stress of 29.9 o C. Ergonomic evaluations also demonstrated that the activity cause injury to workers.

Vibrações em sistemas bidimensionais

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Síntese de polímeros supramoleculares derivados dos ácidos palmítico e mirístico com meglumina e suas caracterizações em meio aquoso

Pós-graduação em Química - IQ

Impactos causados por vibrações mecânicas em chapas de alumínio no processo de laminação a frio

This paper purpose is to analyze one of the main problems faced by cold rolling industry of the current time, the mechanical vibration. Factors such as strips with high velocity in order to increase the productivity and thickness becoming thinner and thinner cause the vibrations to be present at all times during rolling. These market requirements also drive the industry for technology development and thus bring the challenges that the operation of a new modern equipment and more powerful. The initial purpose is to analyze the forces that cause vibration in a rolling mill type four high with two stands, where is desirable to identify the origins of these vibrational forces to make possible dismiss them or at least control its intensity, in order to prevent damage in the rolling mill and ensure product quality to the customer. For it, will be used instruments to record and store the vibrations that occur during the lamination process. With this data will be able to analyze the characteristics of the vibrations and act at your elimination. At the end of the work is expected to demonstrate how important the critical view of the engineer in the analysis of graphics combined with the calculations of the natural vibration frequency and engagement of key parts of the laminator. With these two tools at hand, will be possible to increase the productivity of the rolling mill and act preventively in maintenance, thereby reducing your downtime and increasing its performance and efficiency

Estudo da formação de domínios em membranas modelos induzidos por peptídeos antimicrobianos e sua ação interfacial

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Differences between Tethered Polyelectrolyte Chains on Bare Mica and Hydrophobically Modified Mica

This study investigates the structures of layers of amphiphilic diblock copolymers of poly(t-butyl styrene)-poly- (styrene sulfonate) (PtBS-PSS) adsorbed on both the bare mica surface (hydrophilic) and an octadecyltriethoxysilane (OTE)-modified mica surface (hydrophobic). When the surface is rendered hydrophobic, the nonsoluble block exhibits stronger interaction with the surface and higher adsorbed masses are achieved. Interaction forces between two such adsorbed layers on both substrates were measured using the surface forces apparatus. The effect of salt concentration (Cs) and molecular weight (N) on the height of the self-assembled layers (L0) was examined in each case. The resulting scaling relationship is in good agreement with predictions of the brush model, L0 ∞ N1.0 in the low-salt limit and L0N-1 ∞ (Cs/σ)-0.32 in the salted regime, when adsorption takes place onto the hydrophobized mica surface. For adsorption on the bare mica surface, L0N-0.7 ∞ Cs -0.17 agrees with the scaling prediction of the sparse tethering model. The results suggest that, on the hydrophilic bare mica surface, the adsorbed amount is not high enough to form a brush structure and only very little intermolecular stretching of the tethered chains occurs; in contrast, the presence of the hydrophobic OTE layer increases the tethering density such that the polyelectrolyte chains adopt a brush conformation.

Impactos causados por vibrações mecânicas em chapas de alumínio no processo de laminação a frio

This paper purpose is to analyze one of the main problems faced by cold rolling industry of the current time, the mechanical vibration. Factors such as strips with high velocity in order to increase the productivity and thickness becoming thinner and thinner cause the vibrations to be present at all times during rolling. These market requirements also drive the industry for technology development and thus bring the challenges that the operation of a new modern equipment and more powerful. The initial purpose is to analyze the forces that cause vibration in a rolling mill type four high with two stands, where is desirable to identify the origins of these vibrational forces to make possible dismiss them or at least control its intensity, in order to prevent damage in the rolling mill and ensure product quality to the customer. For it, will be used instruments to record and store the vibrations that occur during the lamination process. With this data will be able to analyze the characteristics of the vibrations and act at your elimination. At the end of the work is expected to demonstrate how important the critical view of the engineer in the analysis of graphics combined with the calculations of the natural vibration frequency and engagement of key parts of the laminator. With these two tools at hand, will be possible to increase the productivity of the rolling mill and act preventively in maintenance, thereby reducing your downtime and increasing its performance and efficiency

Estudo da formação de domínios em membranas modelos induzidos por peptídeos antimicrobianos e sua ação interfacial

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Low-energy electron collisions with glycine

We report cross sections for elastic electron scattering by gas phase glycine (neutral form), obtained with the Schwinger multichannel method. The present results are the first obtained with a new implementation that combines parallelization with OpenMP directives and pseudopotentials. The position of the well known pi* shape resonance ranged from 2.3 eV to 2.8 eV depending on the polarization model and conformer. For the most stable isomer, the present result (2.4 eV) is in fair agreement with electron transmission spectroscopy assignments (1.93 +/- 0.05 eV) and available calculations. Our results also point out a shape resonance around 9.5 eV in the A' symmetry that would be weakly coupled to vibrations of the hydroxyl group. Since electron attachment to a broad and lower lying sigma* orbital located on the OH bond has been suggested the underlying mechanism leading to dissociative electron attachment at low energies, we sought for a shape resonance around similar to 4 eV. Though we obtained cross sections with the target molecule at the equilibrium geometry and with stretched OH bond lengths, least-squares fits to the calculated eigenphase sums did not point out signatures of this anion state (though, in principle, it could be hidden in the large background). The low energy (similar to 1 eV) integral cross section strongly scales as the bond length is stretched, and this could indicate a virtual state pole, since dipole supported bound states are not expected at the geometries addressed here. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3687345]

Spectroscopic, Structural, and Conformational Properties of (Z)-4,4, 4-Trifluoro-3-(2-hydroxyethylamino)-1-(2-hydroxypheny1)-2-buten-1-one, C12H12F3NO3: A Trifluoromethyl-Substituted beta-Aminoenone

The ( Z)-4,4,4-trifluoro-3-(2-hydroxyethylamino)-1-(2-hydroxyphenyl)-2-buten-1-one (C12H12F3NO3) compound was thoroughly studied by IR, Raman, UV-visible, and C-13 and F-19 NMR spectroscopies. The solid-state molecular structure was determined by X-ray diffraction methods. It crystallizes in the P2(1)/c space group with a = 12.1420(4) angstrom, b = 7.8210(3) angstrom, c := 13.8970(5) angstrom, beta = 116.162(2)degrees, and Z = 4 molecules per unit cell. The molecule shows a nearly planar molecular skeleton, favored by intramolecular OH center dot center dot center dot 0 and NH center dot center dot center dot 0 bonds, which are arranged in the lattice as an OH center dot center dot center dot 0 bonded polymer coiled around crystallographic 2-fold screw-axes. The three postulated tautomers were evaluated using quantum chemical calculations. The lowest energy tautomer (I) calculated with density functional theory methods agrees with the observed crystal structure. The structural and conformational properties are discussed considering the effect of the intra- and intermolecular hydrogen bond interactions.

Experimental comparative study on vortex-induced motion (VIM) of a monocolumn platform

An analysis methodology is presented as well as a comparison of results obtained from vortex-induced motion (VIM) model tests of the MonoGoM platform, a monocolumn floating unit designed for the Gulf of Mexico. The choice of scale between the model and the platform in which the tests took place was a very important issue that took into account the basin dimensions and mooring design. The tests were performed in three different basins: the IPT Towing Tank in Brazil (Sept. 2005), the NMRI Model Ship Experimental Towing Tank in Japan (Mar. 2007), and the NMRI Experimental Tank in Japan (Jun. 2008). The purpose is to discuss the most relevant issues regarding the concept, execution, and procedures to comparatively analyze the results obtained from VIM model tests, such as characteristic motion amplitudes, motion periods, and forces. The results pointed out the importance of considering the 2DOF in the model tests, i.e., the coexistence of the motions in both in-line and transverse directions. The approach employed in the tests was designed to build a reliable data set for comparison with theoretical and numerical models for VIM prediction, especially that of monocolumn platforms. [DOI: 10.1115/1.4003494]

Host-guest interactions between xanthones and water: the role of O-H center dot center dot center dot O, C-H center dot center dot center dot O, and pi center dot center dot center dot pi contacts in the channel- and cage-type frameworks

In this article were studied two xanthone derivatives known as 1,5-dihydroxy-8-methoxyxanthone (I) and 1,3,7-trihydroxy-8-methoxyxanthone (II), which show one water molecule into their crystal structures. In xanthone I, there are water wires contributing to build up channel-like cavities along the c axis, whereas in xanthone II the water is surrounded by three xanthone molecules forming a cage-type structure. The geometries of I and II were optimized using the density functional theory method with B3LYP functional, and the results were compared with crystal structure. Both theoretical and experimental investigations reveal a concordance between structural parameters, with the xanthone core presenting an almost flat conformation and substituents adopting the more stable orientations. In the two compounds, the hydroxyl group linked at position 1 is involved in a resonance-assisted hydrogen bond with the carbonyl group. Besides, the supramolecular arrangement of the host/guest systems are stabilized mainly by classical intermolecular hydrogen bonds (O-H center dot center dot center dot O) involving xanthone-to-water and xanthone-to-xanthone. In addition, C-H center dot center dot center dot O weak hydrogen bonds, as well as pi-pi interactions play an important role to stabilize the crystal self-assembly of xanthones I and II. The results reported here underline the role of inclusion of water molecules and their different arrangement into the crystal structure of two xanthone host/guest systems.

Magnetic Tuning of All-Organic Binary Alloys between Two Stable Radicals

Mixtures of 2-(4,5,6,7-tetrafluorobenzimidazol-2-yl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-3-oxide-1-oxyl (F4BImNN) and 2-(benzi-midazol-2-yl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-3-oxide-1-oxyl (BImNN.) crystallize as solid solutions (alloys) across a wide range of binary compositions. (F4BImNN)(x)(BImNN)((1-x)) with x < 0.8 gives orthorhombic unit cells, while x >= 0.9 gives monoclinic unit cells. In all crystalline samples, the dominant intermolecular packing is controlled by one-dimensional (1D) hydrogen-bonded chains that lead to quasi-1D ferromagnetic behavior. Magnetic analysis over 0.4-300 K indicates ordering with strong 1D ferromagnetic exchange along the chains (J/k = 12-22 K). Interchain exchange is estimated to be 33- to 150-fold weaker, based on antiferromagnetic ordered phase formation below Neel temperatures in the 0.4-1.2 K range for the various compositions. The ordering temperatures of the orthorhombic samples increase linearly as (1 - x) increases from 0.25 to 1.00. The variation is attributed to increased interchain distance corresponding to decreased interchain exchange, when more F4BImNN is added into the orthorhombic lattice. The monoclinic samples are not part of the same trend, due to the different interchain arrangement associated with the phase change.

Hydrogen bond and the resonance effect on the formamide-water complexes

The interaction of formamide and the two transition states of its amide group rotation with one, two, or three water molecules was studied in vacuum. Great differences between the electronic structure of formamide in its most stable form and the electronic structure of the transition states were noticed. Intermolecular interactions were intense, especially in the cases where the solvent interacted with the amide and the carbonyl groups simultaneously. In the transition states, the interaction between the lone pair of nitrogen and the water molecule becomes important. With the aid of the natural bond orbitals, natural resonance theory, and electron localization function (ELF) analyses an increase in the resonance of planar formamide with the addition of successive water molecules was observed. Such observation suggests that the hydrogen bonds in the formamidewater complexes may have some covalent character. These results are also supported by the quantitative ELF analyses. (C) 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2012

Revision of Singlet Quantum Yields in the Catalyzed Decomposition of Cyclic Peroxides

The chemiluminescence of cyclic peroxides activated by oxidizable fluorescent dyes is an example of chemically initiated electron exchange luminescence (CIEEL), which has been used also to explain the efficient bioluminescence of fireflies. Diphenoyl peroxide and dimethyl-1,2-dioxetanone were used as model compounds for the development of this CIEEL mechanism. However, the chemiexcitation efficiency of diphenoyl peroxide was found to be much lower than originally described. In this work, we redetermine the chemiexcitation quantum efficiency of dimethyl-1,2-dioxetanone, a more adequate model for firefly bioluminescence, and found a singlet quantum yield (Phi(s)) of 0.1%, a value at least 2 orders of magnitude lower than previously reported. Furthermore, we synthesized two other 1,2-dioxetanone derivatives and confirm the low chemiexcitation efficiency (Phi(s) < 0.1%) of the intermolecular CIEEL-activated decomposition of this class of cyclic. peroxides. These results are compared with other chemiluminescent reactions, supporting the general trend that intermolecular CIEEL systems are much less efficient in generating singlet excited states than analogous intramolecular processes (Phi(s) approximate to 50%), with the notable exception of the peroxyoxalate reaction (Phi(s) approximate to 60%).