Comparação entre diferentes equações antropométricas e a pletismografia para estimar o percentual de gordura de atletas masculinos de Taekwondo

TCC (Graduação) - Universidade Federal de Santa Catarina. Centro de Desportos. Educação Física - Bacharelado.O Taekwondo é um esporte de combate oriundo da Coréia, atualmente integrao quadro de esportes olímpicos, no qual tem suas lutas divididas por categorias de peso, que possui como principal característica os chutes, estes, que são definidos por fatores físicos e que correspondem a 98% dos gestos do combate. Por ser um esporte intermitente, solicita alta preparação física durante a competição, no qual uma luta tem duração aproximada de 8 min, e pelas mudanças ocorridas nos últimos anos, fez com que a antropometria dos atletas fosse um fator decisivo no resultado de uma luta. Pela falta de um protocolo qualificado, específico e válido para avaliar a composição corporal destes atletas, o presente estudo tem como objetivo verificar quais equações antropométricasapresenta maior correlação quando correlacionado com o método de pletismografia por deslocamento de ar para avaliação dopercentual de gordura de atletas masculinos de Taekwondo. Participaram da pesquisa 11 atletas de Taekwondo com idade entre 16 e 30 anos, que foram avaliados por meio de medidas antropométricas de dobras cutâneas, circunferências e perímetros e pelo método de referência pletismografiapor deslocamento de ar. Posteriormente analisou-se a correlação entre a pletismografia por deslocamento de ar e as equações antropométricas.Das nove equações utilizadas seis não apresentaram diferença significativa (p>0,05) com relação à pletismografiapor deslocamento de ar. Dentre estas, três equações apresentaram grande correlação e duas delas apresentaram correlação muito grande com r=914. Devido as características, Whiterset al. (1987) foi considerada a mais adequada para avaliar o %G de atletas masculinos de Taekwondo

A Terminal N₂ Complex of High-Spin Iron(I) in a Weak, Trigonal Ligand Field

The role of Fe in biological and industrial N₂ fixation has inspired the intense study of small molecule analogues of Fe–(N_<i>x</i>H_<i>y</i>) intermediates of potential relevance to these processes. Although a number of low-coordinate Fe–(N₂) featuring varying degrees of fidelity to the nitrogenase active site are now known, these complexes frequently feature strongly donating ligands that either enforce low- or intermediate-spin states or result in linear Fe–(N₂)–Fe bridging motifs. Given that the nitrogenase active site uses weak-field sulfide ligands to stabilize its reactive Fe center(s), N₂ binding to high-spin Fe is of great interest. Herein, we report the synthesis and characterization of the first terminal N₂ complex of high-spin (<i>S</i> = 3/2) Fe­(I) as well as a bridging Fe–(N₂)–Fe analogue. Electron paramagnetic resonance and solution magnetic moment determination confirm the high-spin state, and vibrational experiments indicate a substantial degree of activation of the NN bond in these complexes. Density functional theory calculations reveal an electronic structure for the terminal adduct featuring substantial delocalization of unpaired spin onto the N₂ ligand

A Terminal N₂ Complex of High-Spin Iron(I) in a Weak, Trigonal Ligand Field

The role of Fe in biological and industrial N₂ fixation has inspired the intense study of small molecule analogues of Fe–(N_<i>x</i>H_<i>y</i>) intermediates of potential relevance to these processes. Although a number of low-coordinate Fe–(N₂) featuring varying degrees of fidelity to the nitrogenase active site are now known, these complexes frequently feature strongly donating ligands that either enforce low- or intermediate-spin states or result in linear Fe–(N₂)–Fe bridging motifs. Given that the nitrogenase active site uses weak-field sulfide ligands to stabilize its reactive Fe center(s), N₂ binding to high-spin Fe is of great interest. Herein, we report the synthesis and characterization of the first terminal N₂ complex of high-spin (<i>S</i> = 3/2) Fe­(I) as well as a bridging Fe–(N₂)–Fe analogue. Electron paramagnetic resonance and solution magnetic moment determination confirm the high-spin state, and vibrational experiments indicate a substantial degree of activation of the NN bond in these complexes. Density functional theory calculations reveal an electronic structure for the terminal adduct featuring substantial delocalization of unpaired spin onto the N₂ ligand

N‑Heterocyclic Carbene-Stabilized Boranthrene as a Metal-Free Platform for the Activation of Small Molecules

The multielectron reduction of small molecules (e.g., CO₂) is a key aspect of fuel synthesis from renewable electricity. Transition metals have been researched extensively in this role due to their intrinsic redox properties and reactivity, but more recently, strategies that forego transition metal ions for <i>p</i>-block elements have emerged. In this vein, we report an analogue of boranthrene (9,10-diboraanthracene) stabilized by N-heterocyclic carbenes and its one- and two-electron oxidized congeners. This platform exhibits reversible, two-electron redox chemistry at mild potentials and reacts with O₂, CO₂, and ethylene via formal [4+2] cycloaddition to the central diborabutadiene core. In an area traditionally dominated by transition metals, these results outline an approach for the redox activation of small molecules at mild potentials based on conjugated, light element scaffolds

Functional Synthetic Model for the Lanthanide-Dependent Quinoid Alcohol Dehydrogenase Active Site

The oxidation of methanol by dehydrogenase enzymes is an essential part of the bacterial methane metabolism cycle. The recent discovery of a lanthanide (Ln) cation in the active site of the XoxF dehydrogenase represents the only example of a rare-earth element in a physiological role. Herein, we report the first synthetic, functional model of Ln-dependent dehydrogenase and its stoichiometric and catalytic dehydrogenation of a benzyl alcohol. Density functional theory calculations implicate a hydride transfer mechanism for these reactions

Rhodium Complexes of a Chelating Ligand with Imidazol-2-ylidene and Pyridin-2-ylidene Donors: The Effect of <i>C</i>-Metalation of Nicotinamide Groups on Uptake of Hydride Ion

Rhodium complexes of the imidazolylidene (<i>C</i>-im) <i>N</i>-heterocyclic carbene (NHC) ligand, <i>C</i>-im-pyH⁺, bearing a nicotinamide cation substituent (pyH⁺) have been targeted for ligand-centered uptake and delivery of hydride ion. This work reveals that rhodium­(I) complexes such as [Rh­(<i>C</i>-im-pyH⁺)­(COD)­X]­[PF₆] (<b>1</b>, <b>a</b>: X = Cl, <b>b</b>: X = I) undergo facile <i>C</i>-metalation of the nicotinamide ring to afford rhodium complexes of a novel chelate ligand, <i>C,C′</i>-im-py, with coordinated imidazolylidene (C_im) and pyridylidene (C_py) NHC-donors. Seven examples were characterized and include rhodium­(III) monomers of the general formula [Rh­(<i>C,C′</i>-im-py)­L_<i>x</i>I₂]^<i>z</i>+ (<b>2</b>: <i>z</i> = 1, L = H₂O or solvent, <i>x</i> = 2; <b>3</b>, <b>5</b>, <b>7</b>: <i>z</i> = 0, L = carboxylate, <i>x</i> = 1) and novel rhodium­(II) dimers, the <i>anti/syn</i>-isomers of [Rh₂(<i>C,C′</i>-im-py)₂(μOAc)₂I₂] (<b>4-</b><i><b>anti</b></i>/<i><b>syn</b></i>). The NMR data, backed by DFT calculations, is consistent with attribution of the <i>C,C′</i>-im-py ligand as a bis­(carbene) donor. Single crystal X-ray diffraction studies are reported for <b>2</b>, <b>3</b>, <b>4-</b><i><b>anti</b></i>, <b>4-</b><i><b>syn</b></i> and <b>7</b>. Consistently, within the each complex, the Rh–C_im bond length is shorter than the Rh–C_py bond length, which is the opposite trend to that expected based on simple electronic considerations. It is proposed that intramolecular steric interactions imposed by different rings in the rigid <i>C,C′</i>-im-py chelate ligand dictate the observed Rh–C_NHC bond lengths. Attempts to add hydride to the <i>C</i>-metalated nicotinamide ring in <b>3</b> were unsuccessful. The redox behavior of <b>3</b> and <b>4</b> and, for comparison, an analogous bis­(imidazolylidene)­rhodium­(III) monomer (<b>8</b>), were characterized by cyclic voltammetry, electron paramagnetic resonance (EPR), and UV–vis spectroelectrochemistry. In <b>3</b> and <b>4</b>, the <i>C</i>-metalated nicotinamide ring is found to exhibit a one-electron reduction process at far lower potential (−2.34 V vs. Fc⁺/Fc in acetonitrile) than the two-electron nicotinamide cation-dihydronicotinamide couple found for the corresponding nonmetalated ring (−1.24 V). The <i>C,C′</i>-ligand is electrochemically silent over a large potential range (from −2.3 V to the anodic solvent limit), thus for both <b>3</b> and <b>4</b> the first reduction processes are metal-centered. For <b>4-</b><i><b>anti</b></i>, the cyclic voltammetry and UV–vis spectrochemical results are consistent with a diamagnetic [Rh­(I)­Rh­(II)]₂ tetrameric reduction product. Density functional theory (DFT) calculations were used to further probe the uptake of hydride ion by the nicotinamide ring, both before and after <i>C</i>-metalation. It is found that <i>C</i>-metalation significantly decreases the ability of the nicotinamide ring to take up hydride ion, which is attributed to the “carbene-like” character of a <i>C</i>-metalated pyridylidene ring

Characterization by ENDOR Spectroscopy of the Iron–Alkyl Bond in a Synthetic Counterpart of Organometallic Intermediates in Radical SAM Enzymes

Members of the radical S-adenosyl-l-methionine (SAM) enzyme superfamily initiate a broad spectrum of radical transformations through reductive cleavage of SAM by a [4Fe–4S]1+ cluster it coordinates to generate the reactive 5′-deoxyadenosyl radical (5′-dAdo•). However, 5′-dAdo• is not directly liberated for reaction and instead binds to the unique Fe of the cluster to create the catalytically competent S = 1/2 organometallic intermediate Ω. An alternative mode of reductive SAM cleavage, especially seen photochemically, instead liberates CH3•, which forms the analogous S = 1/2 organometallic intermediate with an Fe–CH3 bond, ΩM. The presence of a covalent Fe–C bond in both structures was established by the ENDOR observation of 13C and 1H hyperfine couplings to the alkyl groups that show isotropic components indicative of Fe–C bond covalency. The synthetic [Fe4S4]3+–CH3 cluster, M-CH3, is a crystallographically characterized analogue to ΩM that exhibits the same [Fe4S4]3+ cluster state as Ω and ΩM, and thus an analysis of its spectroscopic propertiesand comparison with those of Ω and ΩMcan be grounded in its crystal structure. We report cryogenic (2 K) EPR and 13C/1/2H ENDOR measurements on isotopically labeled M-CH3. At low temperatures, the complex exhibits EPR spectra from two distinct conformers/subpopulations. ENDOR shows that at 2 K, one contains a static methyl, but in the other, the methyl undergoes rapid tunneling/hopping rotation about the Fe–CH3 bond. This generates an averaged hyperfine coupling tensor whose analysis requires an extended treatment of rotational averaging. The methyl group 13C/1/2H hyperfine couplings are compared with the corresponding values for Ω and ΩM

Coordination Chemistry of a Strongly-Donating Hydroxylamine with Early Actinides: An Investigation of Redox Properties and Electronic Structure

Separations of f-block elements are a critical aspect of nuclear waste processing. Redox-based separations offer promise, but challenges remain in stabilizing and differentiating actinides in high oxidation states. The investigation of new ligand types that provide thermodynamic stabilization to high-valent actinides is essential for expanding their fundamental chemistry and to elaborate new separation techniques and storage methods. We report herein the preparation and characterization of Th and U complexes of the pyridyl-hydroxylamine ligand, <i>N</i>-<i>tert</i>-butyl-<i>N</i>-(pyridin-2-yl)­hydroxylamine (pyNO^–). Electrochemical studies performed on the homoleptic complexes [M­(pyNO)₄] (M = Th, U) revealed significant stabilization of the U complex upon one-electron oxidation. The salt [U­(pyNO)₄]⁺ was isolated by chemical oxidation of [U­(pyNO)₄]; spectroscopic and computational data support assignment as a U^V cation

Understanding and Controlling the Emission Brightness and Color of Molecular Cerium Luminophores

Molecular cerium complexes are a new class of tunable and energy-efficient visible- and UV-luminophores. Understanding and controlling the emission brightness and color are important for tailoring them for new and specialized applications. Herein, we describe the experimental and computational analyses for series of <i>tris</i>(guanidinate) (<b>1</b>–<b>8</b>, Ce­{(R₂N)­C­(N^<i>i</i>Pr)₂}₃, R = alkyl, silyl, or phenyl groups), guanidinate-amide [<b>GA</b>, <b>A</b> = N­(SiMe₃)₂, <b>G</b> = (Me₃Si)₂NC­(N^<i>i</i>Pr)₂], and guanidinate-aryloxide (<b>GOAr</b>, <b>OAr</b> = 2,6-di-<i>tert</i>-butylphenoxide) cerium­(III) complexes to understand and develop predictive capabilities for their optical properties. Structural studies performed on complexes <b>1</b>–<b>8</b> revealed marked differences in the steric encumbrance around the cerium center induced by various guanidinate ligand backbone substituents, a property that was correlated to photoluminescent quantum yield. Computational studies revealed that consecutive replacements of the amide and aryloxide ligands by guanidinate ligand led to less nonradiative relaxation of bright excited states and smaller Stokes shifts. The results establish a comprehensive structure–luminescence model for molecular cerium­(III) luminophores in terms of both quantum yields and colors. The results provide a clear basis for the design of tunable, molecular, cerium-based, luminescent materials