4 research outputs found
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
Bridgehead Hydrogen Atoms Are Important: Unusual Electrochemistry and Proton Reduction at Iron Dimers with Ferrocenyl-Substituted Phosphido Bridges
The diphosphido-bridged diiron clusters <i>syn</i>-[{μ<sub><i>2</i></sub>-P(CH<sub>2</sub>Fc)H}<sub>2</sub>Fe<sub>2</sub>(CO)<sub>6</sub>] (<b>2a</b>) and <i>anti</i>-/<i>syn</i>-[{μ<sub><i>2</i></sub>-P(CH<sub>2</sub>Fc)Me}<sub>2</sub>Fe<sub>2</sub>(CO)<sub>6</sub>] (<b>3</b>), containing covalently linked ferrocenyl (Fc)
groups, were synthesized
in order to explore the effect of having a redox-active ligand bound
to a Fe<sub>2</sub>P<sub>2</sub> core as in the covalently linked
Fe<sub>4</sub>S<sub>4</sub>-{μ<sub>2</sub>-S(Cys)}-Fe<sub>2</sub>S<sub>2</sub> cofactor of [FeFe]-hydrogenases. The X-ray crystal
structure of <b>2a</b> shows an Fe–Fe bond length of
2.630(1) Å and confirms that the two P–H bonds of the
bridging 1°-phosphido groups are parallel and are separated by
2.683(2) Å. Cyclic voltammetry and spectroelectrochemistry studies
revealed that <b>2a</b>, unusually, undergoes one-electron reduction
at −2.18 V (vs Fc<sup>+</sup>/Fc) to give the anion [{μ<sub><i>2</i></sub>-P(CH<sub>2</sub>Fc)}{μ<sub><i>2</i></sub>-P(CH<sub>2</sub>Fc)H}Fe<sub>2</sub>(CO)<sub>6</sub>]<sup><b>–</b></sup> ([<b>2a</b> – H]<sup><b>–</b></sup>), which was independently obtained by
deprotonation of <b>2a</b> with excess 1,8-diazabicycloundec-7-ene
(DBU). The reduction proceeds through the radical anion <b>2a</b>′<sup><b>•–</b></sup> intermediate, which
was detected by X-band EPR spectroscopy in situ during electrolysis.
The formation of [<b>2a</b> – H]<sup><b>–</b></sup> from the <b>2a</b>′<sup><b>•–</b></sup> radical formally equates to loss of a hydrogen atom from the
bridging P–H group. The result suggests that a new low-energy
route for evolution of molecular hydrogen is available in Fe<sub>2</sub>E<sub>2</sub> dimers with bridgehead hydrogen atomsi.e. dimers
with hydrogen directly bonded to the bridging nonmetal atoms (E =
P, S). In contrast to the one-electron reduction behavior of <b>2a</b>, the mixture of dimers <b>3</b> exhibited a two-electron
reduction at −2.11 V (vs Fc<sup>+</sup>/Fc) that afforded <b>3</b><sup>2–</sup>. Both dimers catalyze the reduction
of protons from <i>p</i>-toluenesulfonic acid, with <b>2a</b> exhibiting higher catalytic currents at lower overpotential
Bridgehead Hydrogen Atoms Are Important: Unusual Electrochemistry and Proton Reduction at Iron Dimers with Ferrocenyl-Substituted Phosphido Bridges
The diphosphido-bridged diiron clusters <i>syn</i>-[{μ<sub><i>2</i></sub>-P(CH<sub>2</sub>Fc)H}<sub>2</sub>Fe<sub>2</sub>(CO)<sub>6</sub>] (<b>2a</b>) and <i>anti</i>-/<i>syn</i>-[{μ<sub><i>2</i></sub>-P(CH<sub>2</sub>Fc)Me}<sub>2</sub>Fe<sub>2</sub>(CO)<sub>6</sub>] (<b>3</b>), containing covalently linked ferrocenyl (Fc)
groups, were synthesized
in order to explore the effect of having a redox-active ligand bound
to a Fe<sub>2</sub>P<sub>2</sub> core as in the covalently linked
Fe<sub>4</sub>S<sub>4</sub>-{μ<sub>2</sub>-S(Cys)}-Fe<sub>2</sub>S<sub>2</sub> cofactor of [FeFe]-hydrogenases. The X-ray crystal
structure of <b>2a</b> shows an Fe–Fe bond length of
2.630(1) Å and confirms that the two P–H bonds of the
bridging 1°-phosphido groups are parallel and are separated by
2.683(2) Å. Cyclic voltammetry and spectroelectrochemistry studies
revealed that <b>2a</b>, unusually, undergoes one-electron reduction
at −2.18 V (vs Fc<sup>+</sup>/Fc) to give the anion [{μ<sub><i>2</i></sub>-P(CH<sub>2</sub>Fc)}{μ<sub><i>2</i></sub>-P(CH<sub>2</sub>Fc)H}Fe<sub>2</sub>(CO)<sub>6</sub>]<sup><b>–</b></sup> ([<b>2a</b> – H]<sup><b>–</b></sup>), which was independently obtained by
deprotonation of <b>2a</b> with excess 1,8-diazabicycloundec-7-ene
(DBU). The reduction proceeds through the radical anion <b>2a</b>′<sup><b>•–</b></sup> intermediate, which
was detected by X-band EPR spectroscopy in situ during electrolysis.
The formation of [<b>2a</b> – H]<sup><b>–</b></sup> from the <b>2a</b>′<sup><b>•–</b></sup> radical formally equates to loss of a hydrogen atom from the
bridging P–H group. The result suggests that a new low-energy
route for evolution of molecular hydrogen is available in Fe<sub>2</sub>E<sub>2</sub> dimers with bridgehead hydrogen atomsi.e. dimers
with hydrogen directly bonded to the bridging nonmetal atoms (E =
P, S). In contrast to the one-electron reduction behavior of <b>2a</b>, the mixture of dimers <b>3</b> exhibited a two-electron
reduction at −2.11 V (vs Fc<sup>+</sup>/Fc) that afforded <b>3</b><sup>2–</sup>. Both dimers catalyze the reduction
of protons from <i>p</i>-toluenesulfonic acid, with <b>2a</b> exhibiting higher catalytic currents at lower overpotential
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<sup>+</sup>, bearing a nicotinamide cation substituent
(pyH<sup>+</sup>) 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<sup>+</sup>)(COD)X][PF<sub>6</sub>] (<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<sub>im</sub>) and pyridylidene
(C<sub>py</sub>) NHC-donors. Seven examples were characterized and
include rhodium(III) monomers of the general formula [Rh(<i>C,C′</i>-im-py)L<sub><i>x</i></sub>I<sub>2</sub>]<sup><i>z</i>+</sup> (<b>2</b>: <i>z</i> = 1, L = H<sub>2</sub>O 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 [Rh<sub>2</sub>(<i>C,C′</i>-im-py)<sub>2</sub>(μOAc)<sub>2</sub>I<sub>2</sub>] (<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<sub>im</sub> bond length is shorter than the Rh–C<sub>py</sub> 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<sub>NHC</sub> 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<sup>+</sup>/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)]<sub>2</sub> 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