Intrinsic roughness and interfaces of Cr/Be multilayers

The structures of Cr/Be multilayer mirror interfaces are investigated using X-ray reflectometry, diffuse X-ray scattering and atomic force microscopy. The combination of these methods makes it possible to separate the contributions of roughness and interlayer diffusion/intermixing for each sample. In the range of period thicknesses of 2.26–0.8 nm, it is found that the growth roughness of the Cr/Be multilayer mirrors does not depend on the period thickness and is ∼0.2 nm. The separation of roughness and diffuseness allows estimation of layer material intermixing and the resulting drop in the optical contrast, which is from 0.85 to 0.17 in comparison with an ideally sharp structure.

Radiological features and management of retained needles

The identification of retained needles is essential because of their sharp structure with possible life-threatening complications. However, radiological evaluation could be challenging, especially in case of needles’ relatively poor conspicuity and small dimension. This pictorial essay focuses on clinical issues (needle features, retention mechanisms and associated complications) and technical aspects (choice of the best diagnostic modality and technique) that can lead the radiologist to an earlier and proper diagnosis of needle retention in order to provide the best treatment for the patient.

Optical Properties of Dopant Induced States in La2−xSrxCuO4-δ Compounds

ABSTRACTOptical data over a broad energy range (∼ 0.01 eV to ∼ 6 eV) for a series of La2−xSrxCuO4-δ compounds are obtained in parallel with the Meissner effect and the superconductivity transition temperature, Tc. Two noteworthy trends in the optical spectra are observed as the Sr concentration is increased in small steps from x = 0 to x = 0.3. First is the appearance of a low frequency band in the reflectivity, R, whose strength follows closely the Meissner effect and Tc measured on the same set of samples. The position of the onset of this band is pinned at ∼0.9 eV for all values of x. The origin of this band in R is identified as an absorption process due to an electronic transition with a large oscillator strength. Second is the appearance and disappearance of an intense vibrational mode whose strength also tracks “superconductivity”. This sharp structure in the far infrared is a characteristic vibrational mode associated with the dopant induced electronic state.

Test of the charge density wave model of potassium

Predictions of the charge density wave (CDW) model for potassium are tested by high-field induced torque experiments. The CDW model is described to show the open orbits on the Fermi surface of potassium with a CDW. Expressions for the induced torque are developed in terms of the resistivity and other parameters of the sample. The induced torque as a function of magnetic field direction shows sharp structure above 3–4 T with more than 20 peaks in 180° rotation. The peaks have the character of open orbits and the large number is predicted by the CDW model. The magnetic field, sample orientation, and temperature dependences of induced torque are also investigated. The magnetic field dependence agrees with that expected from open orbits with magnetic breakdown. However, the open orbits that would cause the induced torque peaks are not in directions predicted by the CDW model. Variation of induced torque with temperatures between 1.4 and 2.1 K can be explained by some of the features of the model although the observed changes are larger than those predicted. The conclusion is that the CDW model explains many of the properties of the high-field induced torque structure.

DIFFUSENESS IN ELECTRONIC SPECTRA THE VAPOR SPECTRUM OF ANTHRACENE

Approximate calculations of the number of rovibronic transitions per unit wavenumber are given for benzene, naphthalene, anthracene, and tetracene. Primarily because of the density of sequence structure all transitions in tetracene vapor should be irresolvably crowded, and hence apparently diffuse, at practical temperatures. Anthracene, whose spectrum has hitherto been described as wholly diffuse, is predicted to be capable of showing resolvable structure at room temperature. At 60 °C and 40 m path a short region of fine sharp structure has been observed. The origin of the first singlet transition is located at 27 688.3 cm−1 (27 757.6 cm−1 in anthracene-d10).