Contribution of oxygen extraction fraction to maximal oxygen uptake in healthy young men

We analysed the importance of systemic and peripheral arteriovenous O2 difference (a- v− O2 and a-vf O2 difference, respectively) and O2 extraction fraction for maximal oxygen uptake ( V˙ O2max ). Fick law of diffusion and the Piiper and Scheid model were applied to investigate whether diffusion vs perfusion limitations vary with V˙ O2max . Articles (n=17) publishing individual data (n=154) on V˙ O2max , maximal cardiac output ( Q˙ max ; indicator-dilution or Fick method), a- v− O2 difference (catheters or Fick equation) and systemic O2 extraction fraction were identified. For the peripheral responses, group-mean data (articles: n=27; subjects: n=234) on leg blood flow (LBF; thermodilution), a-vf O2 difference and O2 extraction fraction (arterial and femoral venous catheters) were obtained. Q˙ max and two-LBF increased linearly by 4.9-6.0 L·min-1 per 1 L·min-1 increase in V˙ O2max (R2 =0.73 and R2 =0.67, respectively; both P<0.001). The a- v− O2 difference increased from 118-168 mL·L-1 from a V˙ O2max of 2-4.5 L·min-1 followed by a reduction (second-order polynomial: R2 =0.27). After accounting for a hypoxemia-induced decrease in arterial O2 content with increasing V˙ O2max (R2 =0.17; P<0.001), systemic O2 extraction fraction increased up to ~90% ( V˙ O2max : 4.5 L·min-1 ) with no further change (exponential decay model: R2 =0.42). Likewise, leg O2 extraction fraction increased with V˙ O2max to approach a maximal value of ~90-95% (R2 =0.83). Muscle O2 diffusing capacity and the equilibration index Y increased linearly with V˙ O2max (R2 =0.77 and R2 =0.31, respectively; both P<0.01), reflecting decreasing O2 diffusional limitations and accentuating O2 delivery limitations. In conclusion, although O2 delivery is the main limiting factor to V˙ O2max , enhanced O2 extraction fraction (≥90%) contributes to the remarkably high V˙ O2max in endurance-trained individuals

Atomic-resolution studies of epitaxial strain release mechanisms in La1.85Sr0.15CuO4/La0.67Ca0.33MnO3\mathrm{L}{\mathrm{a}}_{1.85}\mathrm{S}{\mathrm{r}}_{0.15}\mathrm{Cu}{\mathrm{O}}_{4}/\mathrm{L}{\mathrm{a}}_{0.67}\mathrm{C}{\mathrm{a}}_{0.33}\mathrm{Mn}{\mathrm{O}}_{3} superlattices

In this paper we present an atomic-resolution electron microscopy study of superlattices (SLs) where the colossal magnetoresistant manganite La0.67Ca0.33MnO3 (LCMO) and the high critical temperature superconducting cuprate La1.85Sr0.15CuO4 (LSCO) are combined. Although good quality epitaxial growth can be achieved, both the choice of substrate and the relatively large lattice mismatch between these materials (around 2%) have a significant impact on the system properties [Phys. C 468, 991 (2008); Nature (London) 394, 453 (1998)]. Our samples, grown by pulsed laser deposition, are epitaxial and exhibit high structural quality. By means of cutting-edge electron microscopy and spectroscopy techniques we still find that the epitaxial strain is accommodated by a combination of defects, such as interface steps and antiphase boundaries in the manganite. These defects result in inhomogeneous strain fields through the samples. Also, some chemical inhomogeneities are detected, up to the point that novel phases nucleate. For example, at the LCMO/LSCO interface the ABO3-type manganite adopts a tetragonal LSCO-like structure forming localized layers that locally resemble the composition of La2/3Ca4/3MnO4. Structural distortions are detected in the cuprate as well, which may extend over lateral distances of several unit cells. Finally, we also analyze the influence of the substrate-induced strain by examining superlattices grown on two different substrates: (LaAlO3)0.3(Sr2AlTaO6)0.7 (LSAT) and LaSrAlO4 (LSAO). We observe that SLs grown on LSAT, which are nonsuperconducting, present reduced values of the c axis compared to superlattices grown on LSAO (which are fully superconducting). This finding points to the fact that the proper distance between copper planes in LSCO is essential in obtaining superconductivity in cuprates

Werner states and the two-spinors Heisenberg anti-ferromagnet

We ascertain, following ideas of Arnesen, Bose, and Vedral concerning thermal entanglement [Phys. Rev. Lett. {\bf 87} (2001) 017901] and using the statistical tool called {\it entropic non-triviality} [Lamberti, Martin, Plastino, and Rosso, Physica A {\bf 334} (2004) 119], that there is a one to one correspondence between (i) the mixing coefficient $x$ of a Werner state, on the one hand, and (ii) the temperature $T$ of the one-dimensional Heisenberg two-spin chain with a magnetic field $B$ along the $z-$axis, on the other one. This is true for each value of $B$ below a certain critical value $B_c$. The pertinent mapping depends on the particular $B-$value one selects within such a range

Procedimiento para modular las propiedades eléctricas de óxidos con estructura tipo perovskita derivados del niobato de sodio mediante la creación de vacantes catiónicas

Procedimiento para modular las propiedades eléctricas de óxidos con estructura tipo perovskita derivados del niobato de sodio mediante la creación de vacantes catiónicas. La presente invención se refiere a un procedimiento para modificar controladamente las propiedades eléctricas del óxido NaNbO3 mediante la creación de vacantes catiónicas en la subred A de la estructura tipo perovskita. La introducción progresiva de vacantes en la subred A al dopar con un ión alcalinotérreo como por ejemplo Sr2+ o con un ión de tierra rara como por ejemplo La3+ permite la estabilización de un material ferroeléctrico, y el cambio continuo de comportamiento ferroeléctrico a ferroeléctrico-relaxor característico de las disoluciones sólidas tipo perovskita sin plomo. La presente invención incluye el procedimiento para la obtención de los óxidos que, en función de sus propiedades, pueden ser usados en dispositivos electrónicos como materiales piezoeléctricos y piroeléctricos en sensores y actuadores.Universidad Complutense de Madrid, Consejo Superior de Investigaciones Científicas (España)A1 Solicitud de patentes con informe sobre el estado de la técnic

Evidence for mass renormalization in LaNiO$"" sub 3_: an in situ soft x-ray photoemission study of epitaxial films

We investigate the electronic structure of high-quality single-crystal LaNiO$_3$ (LNO) thin films using in situ photoemission spectroscopy (PES). The in situ high-resolution soft x-ray PES measurements on epitaxial thin films reveal the intrinsic electronic structure of LNO. We find a new sharp feature in the PES spectra crossing the Fermi level, which is derived from the correlated Ni 3$d$ $e_g$ electrons. This feature shows significant enhancement of spectral weight with decreasing temperature. From a detailed analysis of resistivity data, the enhancement of spectral weight is attributed to increasing electron correlations due to antiferromagnetic fluctuations.Comment: 4 pages, 4 figures. submitted to Phys. Rev.

The Ergogenic Effect of Recombinant Human Erythropoietin on V̇O2max Depends on the Severity of Arterial Hypoxemia

Treatment with recombinant human erythropoietin (rhEpo) induces a rise in blood oxygen-carrying capacity (CaO2) that unequivocally enhances maximal oxygen uptake (V̇O2max) during exercise in normoxia, but not when exercise is carried out in severe acute hypoxia. This implies that there should be a threshold altitude at which V̇O2max is less dependent on CaO2. To ascertain which are the mechanisms explaining the interactions between hypoxia, CaO2 and V̇O2max we measured systemic and leg O2 transport and utilization during incremental exercise to exhaustion in normoxia and with different degrees of acute hypoxia in eight rhEpo-treated subjects. Following prolonged rhEpo treatment, the gain in systemic V̇O2max observed in normoxia (6–7%) persisted during mild hypoxia (8% at inspired O2 fraction (FIO2) of 0.173) and was even larger during moderate hypoxia (14–17% at FIO2 = 0.153–0.134). When hypoxia was further augmented to FIO2 = 0.115, there was no rhEpo-induced enhancement of systemic V̇O2max or peak leg V̇O2. The mechanism highlighted by our data is that besides its strong influence on CaO2, rhEpo was found to enhance leg V̇O2max in normoxia through a preferential redistribution of cardiac output toward the exercising legs, whereas this advantageous effect disappeared during severe hypoxia, leaving augmented CaO2 alone insufficient for improving peak leg O2 delivery and V̇O2. Finally, that V̇O2max was largely dependent on CaO2 during moderate hypoxia but became abruptly CaO2-independent by slightly increasing the severity of hypoxia could be an indirect evidence of the appearance of central fatigue

Interface double-exchange ferromagnetism in the Mn-Zn-O system: New class of biphase magnetism

In this Letter, we experimentally show that the room temperature ferromagnetism in the Mn-Zn-O system recently observed is associated with the coexistence of Mn^(3+) and Mn^(4+) via a double-exchange mechanism. The presence of the ZnO around MnO_2 modifies the kinetics of MnO_2 →Mn_2O_3 reduction and favors the coexistence of both Mn oxidation states. The ferromagnetic phase is associated with the interface formed at the Zn diffusion front into Mn oxide, corroborated by preparing thin film multilayers that exhibit saturation magnetization 2 orders of magnitude higher than bulk samples

A major star formation region in the receding tip of the stellar Galactic bar. II. Supplementary information and evidence that the bar is not the same structure as the triaxial bulge previouly reported

This paper is the second part of Garzon et al. (1997: ApJ 491, L31) in which we presented an outline of the analysis of 60 spectra from a follow-up program to the Two Micron Galactic Survey (TMGS) project in the l=27 deg., b=0 deg. area. In this second part, we present a more detailed explanation of the analysis as well a library of the spectra for more complete information for each of the 60 stars, and further discussions on the implications for the structure of the Galaxy. This region contains a prominent excess in the flux distribution and star counts previously observed in several spectral ranges, notably in the TMGS. More than 50% of the spectra of the stars detected with m_K<5.0 mag, within a very high confidence level, correspond to stars of luminosity class I, and a significant proportion of the remainder are very late giants which must also be rapidly evolving. We make the case, using all the available evidence, that we are observing a region at the nearer end of the Galactic bar, where the Scutum spiral arm breaks away, and that this is powerful evidence for the presence of the bar. Alternative explanations do not give nearly such a satisfactory account of the observations. The space localization of one and, a fortiori, of both ends of the bar allows us to infer a position angle for the bar of around 75 deg. with respect to the Sun-Galactic centre line. The angle is different from that given by other authors for the bar and this, we think, is because they refer to the triaxial bulge and not to the bar as detected here.Comment: 21 pages, 1 table, 9 figures, accepted in A

Magnetic field driving custom assembly in (FeCo) nanocrystals

We present the possibility of tuning the nanocrystalline microstructure of Co-rich samples by magnetic field annealing. Custom assembly of nucleated grains, aligned in the field direction, has been observed by means of high resolution transmission microscopy. The organized microstructure was obtained on the basis of the appropriate choice of composition, annealing temperature, related to the initial stages of nanocrystallization process, and magnetic field intensity. The linear pattern of the grains has been explained as a consequence of the counterbalance between magnetic, magnetostatic, and magnetocrystalline couplings, only relevant when the nucleation temperature is well below the Curie temperature of the nucleated phase