Self-interaction correction in multiple scattering theory: application to transition metal oxides

We apply to transition metal monoxides the self-interaction corrected (SIC) local spin density approximation, implemented locally in the multiple scattering theory within the Korringa-Kohn-Rostoker (KKR) band structure method. The calculated electronic structure and in particular magnetic moments and energy gaps are discussed in reference to the earlier SIC results obtained within the linear muffin-tin orbital atomic sphere approximation band structure method, involving transformations between Bloch and Wannier representations, in order to solve the eigenvalue problem and calculate the SIC charge and potential. Since the KKR method can be easily extended to treat disordered alloys, by invoking the coherent potential approximation (CPA), in this paper we compare the CPA approach and supercell calculations to study the electronic structure of NiO with cation vacancies.

Spin wave dispersion on the nanometer scale

Hot electrons injected into antiferromagnetic Mn layers from the tip of a low temperature scanning tunneling microscope have been used to determine the energies, lifetimes, and momenta of antiferromagnetic spin waves on the nanometer scale. The spin waves show a linear dispersion with a velocity of 160+/-10 meV A and lifetimes that scale linearly with energy in agreement with neutron scattering and theory. It is shown that the method is sensitive enough to detect the influence of surface anisotropies on the spin wave dispersion.

Noncollinear surface spin density by surface reconstruction in the alloy NiMn

At the (001) surface of the alloy Ni(50)Mn(50), a noncollinear spin density is observed in real space by spin-polarized scanning tunneling microscopy. The spin density of individual atoms also varies in both size and direction as a function of bias voltage, indicating a noncollinearity in the energy domain. The noncollinearity is driven by a surface reconstruction which breaks the otherwise high surface symmetry. First-principles electronic-structure calculations support the experimental observations and evidence the interplay of reconstruction and spin-orbit coupling.

Wertigkeit der BAHA-Testung für das postoperative Hörergebnis

BACKGROUND

Bone-anchored hearing aids provide a therapy option for patients with conductive and mixed hearing loss, with the possibility of audiological rehabilitation. Test rod and tension headband offer the patient a preoperative impression of their postoperative hearing. The aim of this study was to evaluate the tools available for preoperative assessment of candidates for bone-anchored hearing aids and to ascertain predictive audiometric values.

METHODS

Following implantation of a BAHA Compact system, sound and speech audiograms were performed in each of 16 patients with the bone-anchored BAHA device and with test rod and tension headband.

RESULTS

Both with the BAHA and with the test devices, closure of the air-bone gap occurred and resulted in a clear improvement in hearing threshold and speech perception. The threshold increase with the BAHA was 9 dB greater on average (mean) than that measured with the test rod and the tension headband. Examinaation of speech perception indicated a mean advantage of 14-20% for the anchored BAHA system over the tension headband in monosyllabic testing.

CONCLUSION

Preoperative testing before providing a BAHA system is a good way of predicting what level of hearing and speech perception can be expected after implantation.

Lanthanide contraction and magnetism in the heavy rare earth elements

The heavy rare earth elements crystallize into hexagonally close packed (h.c.p.) structures and share a common outer electronic configuration, differing only in the number of 4f electrons they have. These chemically inert 4f electrons set up localized magnetic moments, which are coupled via an indirect exchange interaction involving the conduction electrons. This leads to the formation of a wide variety of magnetic structures, the periodicities of which are often incommensurate with the underlying crystal lattice. Such incommensurate ordering is associated with a 'webbed' topology of the momentum space surface separating the occupied and unoccupied electron states (the Fermi surface). The shape of this surface-and hence the magnetic structure-for the heavy rare earth elements is known to depend on the ratio of the interplanar spacing c and the interatomic, intraplanar spacing a of the h.c.p. lattice. A theoretical understanding of this problem is, however, far from complete. Here, using gadolinium as a prototype for all the heavy rare earth elements, we generate a unified magnetic phase diagram, which unequivocally links the magnetic structures of the heavy rare earths to their lattice parameters. In addition to verifying the importance of the c/a ratio, we find that the atomic unit cell volume plays a separate, distinct role in determining the magnetic properties: we show that the trend from ferromagnetism to incommensurate ordering as atomic number increases is connected to the concomitant decrease in unit cell volume. This volume decrease occurs because of the so-called lanthanide contraction, where the addition of electrons to the poorly shielding 4f orbitals leads to an increase in effective nuclear charge and, correspondingly, a decrease in ionic radii.

A proposed classification system of central airway stenosis

Tracheobronchial stenosis, a serious problem in adults and children, has multiple causes and has been treated in many ways. While developing an international multicentre study to evaluate efficacy of airway stents, it was realised that no adequate description of central airway stenosis regarding type, location and degree has been published. Thus, comparing results of different treatment modalities in different centres has been difficult due to a lack of uniformity of classification. Reports are typically descriptive and precise classification schemes have not adequately addressed either for the trachea or the main bronchi. A standardised classification scheme was proposed with descriptive images and diagrams for rapid and uniform classification of central airway stenosis. The present authors' system divides stenosis into structural and dynamic types and further classifies the disease by degree of stenosis, location and transition zone. Multiple sites can be described and each is transformed into a simple numerical scoring system prompted by a diagram, which can be easily captured for subsequent uniform analysis across sites. A pilot validation of the system, with 18 pulmonologists of varying training background, showed strong precision and agreement between observers. Such a system will enhance the ability to study the effectiveness of treatment modalities for central airway stenosis.

Mn-stabilized zirconia: from imitation diamonds to a new potential high-Tc ferromagnetic spintronics material

From the basis of ab initio electronic structure calculations which include the effects of thermally excited magnetic fluctuations, we predict Mn-stabilized cubic zirconia to be ferromagnetic above 500 K. We find this material, which is well known both as an imitation diamond and as a catalyst, to be half-metallic with the majority and minority spin Mn impurity states lying in zirconia's wide gap. The Mn concentration can exceed 40%. The high-Tc ferromagnetism is robust to oxygen vacancy defects and to how the Mn impurities are distributed on the Zr fcc sublattice. We propose this ceramic as a promising future spintronics material.

Endobronchial ultrasound-guided transbronchial needle aspiration of lymph nodes in the radiologically normal mediastinum

Endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) can sample enlarged mediastinal lymph nodes in patients with nonsmall cell lung cancer (NSCLC). To date, EBUS-TBNA has only been used to sample nodes visible on computed tomography (CT). The aim of the present study was to determine the accuracy of EBUS-TBNA in sampling nodes <or=1 cm in diameter. NSCLC patients with CT scans showing no enlarged lymph nodes (no node >1 cm) in the mediastinum underwent EBUS-TBNA. Identifiable lymph nodes at locations 2r, 2l, 4r, 4l, 7, 10r, 10l, 11r and 11l were aspirated. All patients underwent subsequent surgical staging. Diagnoses based on aspiration results were compared with those based on surgical results. In 100 patients (mean age 58.9 yrs; 68 males), 119 lymph nodes ranging 5-10 mm in size were detected and sampled. Malignancy was detected in 19 patients but missed in two; all diagnoses were confirmed by surgical findings. The mean diameter of the punctured lymph nodes was 8.1 mm. The sensitivity of EBUS-TBNA for detecting malignancy was 92.3%, specificity was 100%, and the negative predictive value was 96.3%. No complications occurred. In conclusion, endobronchial ultrasound-guided transbronchial needle aspiration can accurately sample even small mediastinal nodes, therefore avoiding unnecessary surgical exploration in one out of six patients who have no computed tomography evidence of mediastinal disease. Potentially operable patients with no signs of mediastinal involvement on computed tomography may benefit from pre-surgical endobronchial ultrasound-guided transbronchial needle aspiration and staging.