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It is shown quantitatively that quasiparticles cause decoherence.

Scanning tunneling spectroscopy of the high-[T.sub.c] superconductor [Bi.sub.2][Sr.sub.2]Ca[Cu.sub.2][O.sub.8+δ] reveals weak, incommensurate, spatial modulations in the tunneling conductance. Images of these energy-dependent modulations are Fourier analyzed to yield the dispersion of their wavevectors. Comparison of the dispersions with photoemission spectroscopy data indicates that quasiparticle interference, due to elastic scattering between characteristic regions of momentum-space, provides a consistent explanation for the conductance modulations, without appeal to another order parameter. These results refocus attention on quasiparticle scattering processes as potential explanations for other incommensurate phenomena in the cuprates. The momentum-resolved tunneling spectroscopy demonstrated here also provides a new technique with which to study quasiparticles in correlated materials., In an ideal metal, the Landau-quasiparticle eigenstates are Bloch wavefunctions characterized by wavevector k and energy ζ. Their dispersion relation, ζ(k), can be measured with momentum-resolved techniques such as angle-resolved [...]

Scanning tunneling microscopy is used to image the additional quasi-particle states generated by quantized vortices in the high critical temperature superconductor [Bi.sub.2][Sr.sub.2]Ca[Cu.sub.2][O.sub.8+δ]. They exhibit a copper-oxygen bond-oriented 'checkerboard' pattern, with four unit cell (4[a.sub.0]) periodicity and a ~30 angstrom decay length. These electronic modulations may be related to the magnetic field-induced, 8[a.sub.0] periodic, spin density modulations with decay length of ~70 angstroms recently discovered in [La.sub.1.84][Sr.sub.0.16]Cu[O.sub.4]. The proposed explanation is a spin density wave localized surrounding each vortex core. General theoretical principles predict that, in the cuprates, a localized spin modulation of wavelength λ should be associated with a corresponding electronic modulation of wavelength λ/2, in good agreement with our observations., Theory indicates that the electronic structure of the cuprates is susceptible to transitions into a variety of ordered states (1-10). Experimentally, antiferromagnetism (AF) and high-temperature superconductivity (HTSC) occupy well-known regions [...]

BackgroundThe prevalence of psychological distress and common mental disorders has been shown to peak in midlife but analyses have ignored the association of poor material circumstances with prevalence. This study aimed to test the hypothesis that the midlife prevalence peak occurs only in lower-income households.MethodPooled data were used from the annual Health Survey for England, a nationally representative cross-sectional study, on community-dwelling individuals aged ⩾16 years from years 1997 to 2006 (n=100 457). 12-item General Health Questionnaire scores, reported mental illness diagnoses and receipt of relevant medication were assessed in relation to household income and age. Analyses were separated by gender and adjusted for age, ethnicity, smoking, social class, education and co-morbidities.ResultsPrevalence of psychological distress, diagnoses and treatments rose with age until early middle age and declined subsequently. In analyses conducted separately by income categories, this pattern was marked in low-income groups but absent in high-income groups. Income-related inequalities in the prevalence of psychological distress were greatest in midlife; for example, in men aged 45–54 years the odds ratio of receiving psychiatric medication in the lowest income group compared with the highest was 7.50 [95% confidence interval (CI) 4.24–13.27] and in women aged 45–54 years the odds ratio of reporting mental illness was 10.25 (95% CI 6.16–17.05).ConclusionsAn increased prevalence of psychological distress, common mental disorder diagnoses and treatment in midlife is not a universal phenomenon but is found only in those in low-income households. This implies the phenomenon is not inevitable but is potentially manageable or preventable. [ABSTRACT FROM PUBLISHER]

Reports on the results of scanning tunneling microscope studies of underdoped high-temperature bismuth strontium calcium copper oxide superconductors. Segregation of electronic structure into superconducting domains; Mixture of short-range electronic orders with long-range characteristics of granular superconductor; Energy gap maps; Interactions between quasiparticles and an impurity atom.

Reports on the presence of an electronic inhomogeneity in the high-temperature superconductor Bi[sub2]Sr[sub 2]CaCu[sub 2]O[sub 8+x], using scanning tunneling microscopy and spectroscopy. Spatial variations in both the local density of states spectrum and the superconducting energy gap; View that the inhomogeneity is a consequence of the proximity to a Mott insulator resulting in poor screening of the charge potentials associated with the oxygen ions left in the BiO plan after doping.

Background: Although various prescription drugs may be equally effective in promoting sleep, some may lead to substantial impairment in psychomotor functioning and an increased risk of motor vehicle accidents.Objective: To develop a general model to evaluate the potential effects of sleep medications on motor vehicle accidents and costs, and apply the model to the French setting.Methods: Impairment in driving performance, as evaluated by randomised controlled open-road studies using the standard deviation of a vehicle's lateral position (SDLP), a measure of weaving, was expressed in terms of equivalent blood alcohol (ethanol) concentration (BAC). Epidemiological data were then used to relate BAC to the excess risk of motor vehicle accidents. Although a non-impairing medication would not increase risk, a medication that produces mild impairment in driving performance (a change of 2.5 cm in SDLP, equivalent to 0.05% BAC) would increase motor vehicle accident risk by 25%. One that leads to moderate impairment (an SDLP change of 4.5 cm, equivalent to 0.08% BAC) would roughly double this risk, and a severely impairing medication (an SDLP change of 7 cm, equivalent to 0.12% BAC) would result in up to a 5-fold increase in motor vehicle accident risk. For application to the French setting, a hypothetical cohort of 100,000 adult drivers with insomnia was assumed to be treated for 14 days either with zaleplon 10 mg, a new sleep medication that has been shown not to significantly impair driving performance, or zopiclone 7.5 mg, which has been shown to cause moderate impairment.Results: Compared with zaleplon, use of zopiclone over 14 days in France would be expected to result in 503 excess accidents per 100,000 drivers at an additional cost of 158 French francs (31 US dollars) per person (1996 values).Conclusions: Our model illustrates the extent to which non-impairing sleep medications could reduce the burden posed by motor vehicle accidents. Our model is designed to be general, and thus can serve as the basis for similar investigations. [ABSTRACT FROM AUTHOR]

Scanning tunneling microscopy is used to image the additional quasi-particle states generated by quantized vortices in the high-Tc superconductor Bi2Sr2CaCu2O8+δ. They exhibit a Cu–O bond oriented ‘checkerboard’ pattern, with (4.2±0.4)a0 periodicity and ∼30 A˚ decay length. [Copyright &y& Elsevier]

Scanning tunneling spectroscopy of the high-T[sub c] superconductor Bi[sub 2]Sr[sub 2]CaCu[sub 2]O[sub 8+δ] reveals weak, incommensurate, spatial modulations in the tunneling conductance. Images of these energy-dependent modulations are Fourier analyzed to yield the dispersion of their wavevectors. Comparison of the dispersions with photoemission spectroscopy data indicates that quasiparticle interference, due to elastic scattering between characteristic regions of momentum-space, provides a consistent explanation for the conductance modulations, without appeal to another order parameter. These results refocus attention on quasiparticle scattering processes as potential explanations for other incommensurate phenomena in the cuprates. The momentum-resolved tunneling spectroscopy demonstrated here also provides a new technique with which to study quasiparticles in correlated materials. [ABSTRACT FROM AUTHOR]

Scanning tunneling spectroscopy of Bi2Sr2CaCu2O8+δ reveals weak, incommensurate, spatial modulations in the tunneling conductance. When images of these energy-dependent modulations are Fourier analyzed the dispersion of their wave vectors can be determined. Comparison of the dispersions with angle-resolved photoemission indicates that quasiparticle interference, due to elastic scattering between specific regions of the Fermi surface, provides a consistent explanation for the conductance modulations. [Copyright &y& Elsevier]