High-energy anomaly in the angle-resolved photoemission spectra of Nd(2-x)Ce(x)CuO4: evidence for a matrix element effect.

We use polarization-dependent angle-resolved photoemission spectroscopy (ARPES) to study the high-energy anomaly (HEA) in the dispersion of Nd(2-x)Ce(x)CuO4, x=0.123. We find that at particular photon energies the anomalous, waterfall-like dispersion gives way to a broad, continuous band. This suggests that the HEA is a matrix element effect: it arises due to a suppression of the intensity of the broadened quasiparticle band in a narrow momentum range. We confirm this interpretation experimentally, by showing that the HEA appears when the matrix element is suppressed deliberately by changing the light polarization. Calculations of the matrix element using atomic wave functions and simulation of the ARPES intensity with one-step model calculations provide further evidence for this scenario. The possibility to detect the full quasiparticle dispersion further allows us to extract the high-energy self-energy function near the center and at the edge of the Brillouin zone.

Reversal of the circular dichroism in angle-resolved photoemission from Bi2Te3.

The helical Dirac fermions at the surface of topological insulators show a strong circular dichroism which has been explained as being due to either the initial-state spin angular momentum, the initial-state orbital angular momentum, or the handedness of the experimental setup. All of these interpretations conflict with our data from Bi(2)Te(3) which depend on the photon energy and show several sign changes. Our one-step photoemission calculations coupled to ab initio theory confirm the sign change and assign the dichroism to a final-state effect. Instead, the spin polarization of the photoelectrons excited with linearly polarized light remains a reliable probe for the spin in the initial state.

Correlation of electron self-energy with geometric structure in low-energy electron diffraction.

In low-energy electron diffraction (LEED) studies of surface geometries where the energy dependence of the intensities is analyzed, the in-plane lattice parameter of the surface is usually set to a value determined by x-ray diffraction for the bulk crystal. In cases where it is not known, for instance in films that are incommensurate with the substrate, it is desirable to fit the in-plane lattice parameters in the same analysis as the perpendicular interlayer spacings. We show that this is not possible in a conventional LEED I(E) analysis because the inner potential, which is typically treated as an adjustable parameter, is correlated with the geometrical structure. Therefore, without having prior knowledge of the inner potential, it is not possible to determine the complete surface structure simply from LEED I(E) spectra, and the in-plane lattice parameter must be determined independently before the I(E) analysis is performed. This can be accomplished by establishing a more precise experimental geometry. Further, it is shown that the convention of omitting the energy dependency of the real part of the inner potential means geometrical LEED results cannot be trusted beyond a precision of approximately 0.01 Å.

Voxelwise analysis of diffusion tensor imaging and structural MR imaging in patients with the m.3243A>G mutation in mitochondrial DNA.

BACKGROUND AND PURPOSE: The m.3243A>G mutation is the most common pathogenic mutation in mtDNA; tissues with high dependence on aerobic energy metabolism, such as the brain, heart, and skeletal muscle, are most affected by the ensuing mitochondrial dysfunction. We hypothesized that the m.3243A>G mutation manifests as disturbances in white matter microstructural integrity and volumetric changes in the brain. MATERIALS AND METHODS: DTI and structural MR imaging were performed on 15 adult patients with the m.3243A>G mutation and 14 healthy age-matched controls. Voxelwise analysis of the DTI data was performed to reveal possible differences in FA and MD values. Additionally, normalized brain tissue volumes of the subjects were measured, and voxelwise analysis of gray matter was performed to assess volumetric changes in the brain. RESULTS: Among patients with m.3243A>G mutation, voxelwise analysis of the DTI data revealed significantly reduced FA in several areas located mainly in the occipital lobes, thalami, external and internal capsules, brain stem, cerebellar peduncles, and cerebellar white matter. There were no differences in MD values between the patients and the controls. Analysis of the structural MR imaging data revealed reduced total volume of gray and white matter in patients with m.3243A>G mutation, and VBM analysis identified areas of significant gray matter loss mainly in the occipital lobes and cerebellum. CONCLUSIONS: Our findings show that patients with m.3243A>G mutation have mild microstructural damage leading to loss of directional organization of white matter and reduced brain volumes.

Circular dichroism in the angle-resolved photoemission spectrum of the high-temperature Bi_{2}Sr_{2}CaCu_{2}O_{8+delta} superconductor: can these measurements be interpreted as evidence for time-reversal symmetry breaking?

We report first-principles computations of the angle-resolved photoemission response with circularly polarized light in Bi_{2}Sr_{2}CaCu_{2}O_{8+delta} for the purpose of delineating contributions to the circular dichroism resulting from distortions and modulations of the crystal lattice. Comparison with available experimental results shows that the measured circular dichroism from antinodal mirror planes is reproduced in quantitative detail in calculations employing the average orthorhombic crystal structure. We thus conclude that the existing angle-resolved photoemission measurements can be understood essentially within the framework of the conventional picture, without the need to invoke unconventional mechanisms.

Effect of symmetry distortions on photoelectron selection rules and spectra of Bi2Sr2CaCu2O8+delta.

We derive photoelectron selection rules along the glide plane in orthorhombic Bi2Sr2CaCu2O8+delta (Bi2212). These selection rules explain the reversed intensity behavior of the shadow and the main band of the material as a natural consequence of the variating representation of the final state as a function of k(parallel). Our one-step simulations strongly support the structural origin of the shadow band but we also introduce a scenario for detecting antiferromagnetic signatures in low doping.

Experimental proof of a structural origin for the shadow fermi surface of Bi2Sr2CaCu2O8+delta.

By combining surprising new results from a full polarization analysis of nodal angle-resolved photoemission data from pristine and modulation-free Bi(2)Sr(2)CaCu(2)O(8+delta) with structural information from LEED and ab initio one-step photoemission simulations, we prove that the shadow Fermi surface in these systems is of structural origin, being due to orthorhombic distortions from tetragonal symmetry present both in surface and bulk. Consequently, one of the longest standing open issues in the investigation of the Fermi surface of these widely studied systems finally meets its resolution.

Evolution of midgap states and residual three dimensionality in La2-xSrxCuO4.

We carry out extensive first-principles doping-dependent computations of angle-resolved photoemission (ARPES) intensities in La2-xSrxCuO4 over a wide range of binding energies. Intercell hopping and the associated three dimensionality, which is usually neglected in discussing cuprate physics, is shown to play a key role in shaping the ARPES spectra. Despite the obvious importance of strong coupling effects (e.g., the presence of a lower Hubbard band coexisting with midgap states in the doped insulator), a number of salient features of the experimental ARPES spectra are captured to a surprising extent when kz dispersion is properly included in the analysis.

Patellofemoral relationships and cartilage breakdown.

We evaluated the association between patellofemoral relationships and cartilage lesions in patients (age range 15-49) with anterior knee pain without patellar dislocation (n = 24) and in patients with isolated meniscal rupture without a high energy trauma (n = 21). The position of the patella was assessed from knee radiographs, and cartilage lesion was graded and mapped at arthroscopy. In subjects with lateral patellar cartilage lesion the patella tilted laterally (p < 0.01) and was clearly laterally displaced (p < 0.001), compared to those without patellar cartilage lesion. In subjects with central patellar cartilage lesion the patella located high according to the Insall-Salvati index (p < 0.01) and was somewhat laterally displaced (p < 0.05). Compared to subjects without cartilage lesion in the femoral trochlea, the patella was laterally displaced in subjects with lesion in the lateral trochlea (p < 0.001). In conclusion, our results suggest that specific malalignments predispose to patellofemoral cartilage lesion, but prospective studies are needed to confirm the finding.

The influence of EDTMP-concentration on the biodistribution of radio-lanthanides and 225-Ac in tumor-bearing mice. The ISOLDE Collaboration.

High-resolution gamma spectroscopy was applied to measure simultaneously the biodistribution of carrier-free radionuclides of several lanthanides (141Ce, 145Sm, 149Gd, 167Tm) and 225Ac in tumor-bearing nude mice. Mixtures of the radiotracers were injected in solutions containing different concentrations of EDTMP (ethylenediaminetetramethylenephosphonic acid). The strong dependence of liver uptake on the ionic radius of the radio-lanthanides was confirmed for all tracers used. The ratios of radioactivity concentrated in tumour that concentrated in liver are strongly influenced by the EDTMP concentration, reaching values close to 10 for Tm, 3 for Sm, and 1 for Ac. The optimal EDTMP concentrations, giving highest tumor-to-liver ratios of enrichment, were between 1 and 10 mM for 100 microL injected volume for the animal model used in this experiment. In radionuclide therapy using EDTMP as ligands, close control of ligand concentration will be necessary.

Congestive heart failure in old age: prevalence, mechanisms and 4-year prognosis in the Helsinki Ageing Study.

OBJECTIVE: To examine the prevalence, underlying diseases, abnormalities of left ventricular function and prognosis in congestive heart failure (CHF) of old age. DESIGN: A population-based clinical and echocardiographic study with a 4-year mortality follow-up. SETTING: University hospital. SUBJECTS: Five hundred and one individuals born in 1904. 1909 and 1914 (367 women). MAIN OUTCOME MEASURES: Presence of CHF by clinical and chest radiograph criteria: left ventricular size and systolic function by echocardiography; grade of aortic and mitral valve lesion by Doppler echocardiography; 4-year total and cardiovascular mortality. RESULTS: Forty-one of 501 participants (8.2%) had CHF. Ischaemic heart disease (54%), hypertension (54%) and moderate-to-severe mitral or aortic valve disease (51%) were the main underlying conditions; 90% of patients had one or more of these diseases. Most individuals with CHF (28 of 39 patients, 72%) had normal left ventricular contractions at echocardiography. 'Diastolic CHF', defined as CHF with normal systolic left ventricular function and no regurgitant valve disease, was found in 51% (20 of 39 patients). The relative 4-year risk for death associated with CHF, adjusted for age and sex, was 2.1 (95% confidence interval 1.3-3.4) for all-cause mortality and 4.2 (CI 1.9-5.6) for cardiovascular mortality. CONCLUSIONS: The prevalence of CHF in a population aged 75-86 years is approximately 8%. Ischaemic or valvular heart disease and hypertension are the main underlying conditions. At echocardiography, about 50% of the elderly with CHF have normal left ventricular systolic contractions in the absence of valve disease and an additional 20% have normal systolic function with mitral regurgitation. The presence of CHF doubles the age- and sex-adjusted risk of death from all causes, and quadruples the risk of cardiovascular death during 4-year follow-up.

Natural history of aortic valve stenosis of varying severity in the elderly.

In a population sample of 501 persons aged 75 to 86 years, Doppler echocardiography uncovered moderate or severe aortic valve stenosis in 8.8% of women and 3.6% of men. Severe aortic valve stenosis predicted a four-fold-age- and sex-adjusted risk of death within 4 years of diagnosis, and mortality tended to be increased also with moderate lesions; mild aortic valve stenosis had a favorable outcome.

Calcific degeneration of the aortic valve in old age: is the development of flow obstruction predictable?

OBJECTIVE: Aortic valve calcification and stenosis become increasingly common with advancing age. This work aimed at assessing whether a time-dependent reduction of aortic valve area is detectable in an unselected elderly population and whether the rate of reduction can be predicted from clinical or biochemical characteristics. DESIGN: A population-based prospective echocardiographic follow-up study. SETTING: A university hospital. SUBJECTS: In 1990, randomly selected persons born in 1904, 1909 and 1914 (total n = 501) underwent a Doppler echocardiographic study of aortic valve and biochemical tests of glucose, lipid and calcium metabolism. In 1993, echocardiography was repeated in 333 survivors of the original cohorts. These individuals constitute the present study population. MAIN OUTCOME MEASURES: Three-year changes in the aortic valve area and velocity ratio (peak outflow tract velocity/peak aortic jet velocity) determined by Doppler echocardiography. RESULTS: Aortic valve area decreased from a mean of 1.95 cm2 (95% confidence interval of mean, 1.88-2.03 cm2) to 1.78 cm2 (1.71-1.85 cm2) within 3 years (P < 0.001). Concomitantly, the velocity ratio decreased from 0.75 (0.73-0.77) to 0.68 (0.67-0.70) (P < 0.001). The changes in aortic valve area and velocity ratio were unrelated to age, sex, presence of hypertension, coronary artery disease or diabetes, and to all assessed biochemical characteristics. A weak positive statistical association was found between the decrease in aortic valve area and the body mass index at entry (r = 0.16, P < 0.01). CONCLUSIONS: A time-dependent reduction of the aortic valve flow orifice can be demonstrated in persons representing the general elderly population. The deterioration of aortic valve function within a span of 3 years is neither clinically nor biochemically predictable. A longer follow-up may be necessary to identify the risk factors of aortic valve stenosis in old age.