35 research outputs found
Post-Exercise Protein Trial: Interactions between Diet and Exercise (PEPTIDE): study protocol for randomized controlled trial
Concentration addition, independent action and generalized concentration addition models for mixture effect prediction of sex hormone synthesis in vitro
Humans are concomitantly exposed to numerous chemicals. An infinite number of combinations and doses thereof can be imagined. For toxicological risk assessment the mathematical prediction of mixture effects, using knowledge on single chemicals, is therefore desirable. We investigated pros and cons of the concentration addition (CA), independent action (IA) and generalized concentration addition (GCA) models. First we measured effects of single chemicals and mixtures thereof on steroid synthesis in H295R cells. Then single chemical data were applied to the models; predictions of mixture effects were calculated and compared to the experimental mixture data. Mixture 1 contained environmental chemicals adjusted in ratio according to human exposure levels. Mixture 2 was a potency adjusted mixture containing five pesticides. Prediction of testosterone effects coincided with the experimental Mixture 1 data. In contrast, antagonism was observed for effects of Mixture 2 on this hormone. The mixtures contained chemicals exerting only limited maximal effects. This hampered prediction by the CA and IA models, whereas the GCA model could be used to predict a full dose response curve. Regarding effects on progesterone and estradiol, some chemicals were having stimulatory effects whereas others had inhibitory effects. The three models were not applicable in this situation and no predictions could be performed. Finally, the expected contributions of single chemicals to the mixture effects were calculated. Prochloraz was the predominant but not sole driver of the mixtures, suggesting that one chemical alone was not responsible for the mixture effects. In conclusion, the GCA model seemed to be superior to the CA and IA models for the prediction of testosterone effects. A situation with chemicals exerting opposing effects, for which the models could not be applied, was identified. In addition, the data indicate that in non-potency adjusted mixtures the effects cannot always be accounted for by single chemicals
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Magnetism and negative magnetoresistance of two magnetically ordering, rare-earth-containing zintl phases with a new structure type: EuGa 2Pn2 (Pn=P, As)
Single crystals of EuGa2Pn2 (Pn=P, As) were grown from a molten Ga flux and characterized by single-crystal X-ray diffraction at 100(1) K. They are isostructural and crystallize in a new structure type (monoclinic, P2/m, a=9.2822(9) A, =3.8967(4) A, c=12.0777(11) A, Î’=95.5220(10), R1= 0.0148, wR2=0.0325 (EuGa2P2) and a=9.4953(7) A, b=4.0294(3) A, c=12.4237(9) A, Î’ =95.3040(10), R1=0.0155, wR2=0.0315 (EuGa2As2)). The structures consist of alternating layers of two-dimensional Ga2Pn2 anions and Eu cations. The anion layers are composed of Ga2Pn6 staggered, ethane-like moieties having a rare Ga-Ga bonding motif; these moieties are connected in a complex fashion bymeans of shared Pn atoms. Both structures showsmall residual electron densities that can be modeled by adding a Eu atom and removing two bonded Ga atoms, resulting in structures (< 2%) wheremost of the atoms are the same, but there is a difference in bonding that leads to one-dimensional ribbons of parallel Ga2Pn6 staggered, ethane-like moieties. The compounds can be understood within the Zintl formalism, but show metallic resistivity. Magnetization measurements performed on single crystals show low-temperature magnetic anisotropy as well as multiple magnetic ordering events that occur at and below 24 and 20 K for the phosphorus and arsenic analogs, respectively. The magnetic coupling between Eu ions is attributed to indirect exchange via an RKKY interaction, which is consistent with the metallic behavior. The compounds display large negative magnetoresistance of up to-80 and-30%(MR=[(F(H)-F(0))/F(H)] 100%) for Pn=P,As, respectively,which is maximal at the magnetic ordering temperatures in the highest measured field (5T)
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Magnetism and negative magnetoresistance of two magnetically ordering, rare-earth-containing zintl phases with a new structure type: EuGa 2Pn2 (Pn=P, As)
Single crystals of EuGa2Pn2 (Pn=P, As) were grown from a molten Ga flux and characterized by single-crystal X-ray diffraction at 100(1) K. They are isostructural and crystallize in a new structure type (monoclinic, P2/m, a=9.2822(9) A, =3.8967(4) A, c=12.0777(11) A, Î’=95.5220(10), R1= 0.0148, wR2=0.0325 (EuGa2P2) and a=9.4953(7) A, b=4.0294(3) A, c=12.4237(9) A, Î’ =95.3040(10), R1=0.0155, wR2=0.0315 (EuGa2As2)). The structures consist of alternating layers of two-dimensional Ga2Pn2 anions and Eu cations. The anion layers are composed of Ga2Pn6 staggered, ethane-like moieties having a rare Ga-Ga bonding motif; these moieties are connected in a complex fashion bymeans of shared Pn atoms. Both structures showsmall residual electron densities that can be modeled by adding a Eu atom and removing two bonded Ga atoms, resulting in structures (< 2%) wheremost of the atoms are the same, but there is a difference in bonding that leads to one-dimensional ribbons of parallel Ga2Pn6 staggered, ethane-like moieties. The compounds can be understood within the Zintl formalism, but show metallic resistivity. Magnetization measurements performed on single crystals show low-temperature magnetic anisotropy as well as multiple magnetic ordering events that occur at and below 24 and 20 K for the phosphorus and arsenic analogs, respectively. The magnetic coupling between Eu ions is attributed to indirect exchange via an RKKY interaction, which is consistent with the metallic behavior. The compounds display large negative magnetoresistance of up to-80 and-30%(MR=[(F(H)-F(0))/F(H)] 100%) for Pn=P,As, respectively,which is maximal at the magnetic ordering temperatures in the highest measured field (5T)