Imaging the impact on cuprate superconductivity of varying the interatomic distances within individual crystal unit cells.

Many theoretical models of high-temperature superconductivity focus only on the doping dependence of the CuO(2)-plane electronic structure. However, such models are manifestly insufficient to explain the strong variations in superconducting critical temperature, T(c), among cuprates that have identical hole density but are crystallographically different outside of the CuO(2) plane. A key challenge, therefore, has been to identify a predominant out-of-plane influence controlling the superconductivity, with much attention focusing on the distance d(A) between the apical oxygen and the planar copper atom. Here we report direct determination of how variations in interatomic distances within individual crystalline unit cells affect the superconducting energy-gap maximum Delta of Bi(2)Sr(2)CaCu(2)O(8+delta). In this material, quasiperiodic variations of unit cell geometry occur in the form of a bulk crystalline "supermodulation." Within each supermodulation period, we find approximately 9 +/- 1% cosinusoidal variation in local Delta that is anticorrelated with the associated d(A) variations. Furthermore, we show that phenomenological consistency would exist between these effects and the random Delta variations found near dopant atoms if the primary effect of the interstitial dopant atom is to displace the apical oxygen so as to diminish d(A) or tilt the CuO(5) pyramid. Thus, we reveal a strong, nonrandom out-of-plane effect on cuprate superconductivity at atomic scale.

Interplay of electron-lattice interactions and superconductivity in superconductivity in Bi2Sr2CaCu2O8+delta.

Formation of electron pairs is essential to superconductivity. For conventional superconductors, tunnelling spectroscopy has established that pairing is mediated by bosonic modes (phonons); a peak in the second derivative of tunnel current d2I/dV2 corresponds to each phonon mode. For high-transition-temperature (high-T(c)) superconductivity, however, no boson mediating electron pairing has been identified. One explanation could be that electron pair formation and related electron-boson interactions are heterogeneous at the atomic scale and therefore challenging to characterize. However, with the latest advances in d2I/dV2 spectroscopy using scanning tunnelling microscopy, it has become possible to study bosonic modes directly at the atomic scale. Here we report d2I/dV2 imaging studies of the high-T(c) superconductor Bi2Sr2CaCu2O8+delta. We find intense disorder of electron-boson interaction energies at the nanometre scale, along with the expected modulations in d2I/dV2 (refs 9, 10). Changing the density of holes has minimal effects on both the average mode energies and the modulations, indicating that the bosonic modes are unrelated to electronic or magnetic structure. Instead, the modes appear to be local lattice vibrations, as substitution of 18O for 16O throughout the material reduces the average mode energy by approximately 6 per cent--the expected effect of this isotope substitution on lattice vibration frequencies. Significantly, the mode energies are always spatially anticorrelated with the superconducting pairing-gap energies, suggesting an interplay between these lattice vibration modes and the superconductivity.

Atomic-Scale Sources and Mechanism of Nanoscale Electronic Disorder in Bi2Sr2CaCu2O8+delta.

The randomness of dopant atom distributions in cuprate high-critical temperature superconductors has long been suspected to cause nanoscale electronic disorder. In the superconductor Bi2Sr2CaCu2O8+delta, we identified populations of atomic-scale impurity states whose spatial densities follow closely those of the oxygen dopant atoms. We found that the impurity-state locations are strongly correlated with all manifestations of the nanoscale electronic disorder. This disorder occurs via an unanticipated mechanism exhibiting high-energy spectral weight shifts, with associated strong superconducting coherence peak suppression but very weak scattering of low-energy quasi-particles.

Providers' smoking cessation attitudes and practices for older patients.

A mail survey of 136 providers in a health maintenance organization in the Chicago metropolitan area examined smoking cessation attitudes and performance of the 4As protocol (asking, advising, assisting, arranging) for patients aged 50 years or older. Asking about smoking was most frequent, followed by arranging, advising, and assisting. Physicians and nurse practitioners performed each of the 4As more often than did registered and licensed practical nurses. In multiple logistic regression analyses, provider type was the only significant predictor of asking about smoking. Advising, assisting, and arranging follow-ups were more likely to be performed by providers who perceived a sense of professional responsibility about older patients' smoking; advising was more likely for providers who perceived that they had enough time to advise older patients about smoking; and assisting and arranging were more likely for providers with a stronger sense of self-efficacy for helping older patients stop smoking.

Asthma prevalence and risk factors in selected Head Start sites in Chicago.

Prevalence of and risk factors for asthma were examined in 1085 Head Start families at 18 Head Start sites in four high-risk community areas in 1994. A total of 13.9% of the families reported diagnosed asthma in their Head Start child and 18.8% reported that their child wheezed in the last 12 months. A total of 26.9% of respondents reported asthma in the immediate family of the child. Low birth weight (1500-2499 g), very low birth weight (<1500 g), and self-reported exposure to dampness or mold in the last 12 months were significantly associated with self-reported diagnosed asthma (OR = 1.93; 95% CI 1.17-8.73), (OR = 4.5; 95% CI 1.25-16.3), and (OR = 1.94; 95% CI 1.23-3.04), respectively. The young age of the children in Head Start, as well as the high prevalence of asthma in their families, suggest that the Head Start programs offer an unusual opportunity for asthma prevention programs.

Attitudes and practices for smoking cessation counseling by provider type and patient age.

Attitudes and self-reported practices for smoking cessation counseling among 145 providers at a health maintenance organization were compared among two provider groups, physicians/nurse practitioners and registered/licensed practical nurses, and across three patient age groups, < 50, 50-64, and > or = 65. Smoking cessation attitudes did not differ by provider type but they did differ by patient age, especially among the registered/licensed practical nurses, whose attitudes were least favorable for the oldest smokers (> or = 65). While smoking cessation practices did not differ by patient age, they did differ by provider type. Self-reported performance of the 4 As of smoking cessation practice (Ask, Advise, Assist, Arrange) was more frequent among the physicians/nurse practitioners than among the registered/licensed practical nurses. However, among both groups, asking and advising practices were reported more often than were assisting and arranging. In all cases, different attitudes were correlated with different practice behaviors for the two provider groups. Also, there were more significant correlations between age-specific attitudes and practices among the registered/licensed practical nurses than among the physicians/nurse practitioners. This was true especially regarding the oldest patients. The findings suggest a need for provider education, especially among registered/licensed practical nurses, about the benefits of smoking cessation for patients of all ages and the potential effectiveness of provider-based intervention strategies that are targeted toward specific age groups. The findings also suggest that assisting and arranging practices in particular need improvement among all types of providers.