Separation of quadrupolar and magnetic contributions to spin-lattice relaxation in the case of a single isotope

We present a NMR pulse double-irradiation method which allows one to separate magnetic from quadrupolar contributions in the spin-lattice relaxation. The pulse sequence fully saturates one transition while another is observed. In the presence of a Delta m = 2 quadrupolar contribution, the intensity of the observed line is altered compared to a standard spin-echo experiment. We calculated analytically this intensity change for spins I=1, 3/2, 5/2, thus providing a quantitative analysis of the experimental results. Since the pulse sequence we used takes care of the absorbed radio-frequency power, no problems due to heating arise. The method is especially suited when only one NMR sensitive isotope is available. Different cross-checks were performed to prove the reliability of the obtained results. The applicability of this method is demonstrated by a study of the plane oxygen 17O (I = 5/2) in the high-temperature superconductor YBa_2Cu_4O_8: the 17O spin-lattice relaxation rate consists of magnetic as well as quadrupolar contributions.Comment: 7 pages, 6 figure

Charge degree of freedom and single-spin fluid model in YBa_2Cu_4O_8

We present a 17O nuclear magnetic resonance study in the stoichiometric superconductor YBa_2Cu_4O_8. A double irradiation method enables us to show that, below around 180 K, the spin-lattice relaxation rate of plane oxygen is not only driven by magnetic, but also significantly by quadrupolar fluctuations, i.e. low-frequency charge fluctuations. In the superconducting state, on lowering the temperature, the quadrupolar relaxation diminishes faster than the magnetic one. These findings show that, with the opening of the pseudo spin gap, a charge degree of freedom of mainly oxygen character is present in the electronic low-energy excitation spectrum.Comment: 4 pages, 3 figures, REVTE

Prenatal stress exposure is associated with increased dyspnea perception in adulthood

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.Dyspnoea is the aversive cardinal symptom in various prevalent conditions such as respiratory, cardiovascular and neuromuscular diseases and is associated with great individual and socioeconomic burden [1]. Over the past years, several physiological and also psychological factors have been demonstrated to affect the perception of dyspnoea [1, 2]. For example, high levels of anxiety in adulthood were associated with increased dyspnoea perception in patients with asthma or chronic obstructive pulmonary disease (COPD), but also in healthy controls [2]. Moreover, adverse, separation-related experiences in childhood were linked to the subsequent development of increased anxiety and dyspnoea [3]. However, the effects of adverse experiences in early, prenatal life on dyspnoea perception remain widely unknown, although prenatal exposure to maternal stress and anxiety has convincingly been related to the development of other health and behavioural problems later in life, including impairments of the respiratory control system and high anxiety levels [4–9]. Therefore, this study investigated the relationship between prenatal exposure to maternal stress and the perception of dyspnoea in adulthood 28 years later

Planar Cu and O hole densities in high-Tc cuprates determined with NMR

The electric hyperfine interaction observable in atomic spectroscopy for O and Cu ions in various configurations is used to analyze the quadrupole splitting of O and Cu nuclear magnetic resonance (NMR) in La2-xSrxCuO4 and YBa2Cu3O6+y and to determine the hole densities at both sites as a function of doping. It is found that in La2-xSrxCuO4 all doped holes (x) reside in the Cu-O plane but almost exclusively at O. For YBa2Cu3O6+y and y<0.6 doped holes are found at planar Cu as well as O. For y>0.6 further doping increases the hole content only for planar O. The phase diagram based on NMR data is presented. Further implications from the Cu A and B site in La2-xSrxCuO4 and the two planar O sites in YBa2Cu3O6+y and consequences for the phase diagram are discussed.Comment: 18 pages, 1 figure, 2 tables, 2 appendice