Evidence for an ultrafast breakdown of the BeO band structure due to swift argon and xenon ions.

Auger-electron spectra associated with Be atoms in the pure metal lattice and in the stoichiometric oxide have been investigated for different incident charged particles. For fast incident electrons, for Ar7+ and Ar15+ ions as well as Xe15+ and Xe31+ ions at velocities of 6% to 10% the speed of light, there are strong differences in the corresponding spectral distributions of Be-K Auger lines. These differences are related to changes in the local electronic band structure of BeO on a femtosecond time scale after the passage of highly charged heavy ions.

ToF-SIMS application in the visualization and analysis of fingerprints after contact with amphetamine drugs.

Time-of-flight secondary ion mass spectrometry was applied in forensic research for characterization, visualization and analysis of fingerprints left after the fingers were contaminated by traces of drugs: amphetamine (AF), methamphetamine (MA) and methylenedioxymethamphetamine (MDMA; ecstasy). Experimental work was carried out using four kinds of bases (steel, aluminium, brass and glass) on which fingerprints were imprinted. The results of our preliminary studies have demonstrated that the ToF-SIMS technique can be a powerful tool in chemical investigations of fingerprints and detection of traces of substances, which do not exist in natural skin extraction, but can be found at the crime scene.

Indications for enhanced auger-electron absorption in a hot-electron gas.

Solid-state Auger-electron angular distributions are known to be largely independent of the type of excitation, following roughly a cosine law for low ejection energies. In this Letter it is shown that the ion-track dynamics and the corresponding high electron temperatures lead to significant variations of these Auger distributions. Ratios for different degrees of inner-shell ionization versus angle are sensitive to the high-energy-deposition density. The ratios show a minimum for emission angles close to the ion-track direction, consistent with enhanced inelastic electron-energy losses or electron absorption, respectively. Thus Auger-electron yields are influenced by the spatial electronic excitation distribution.

Magnetocardiographic mapping of QRS fragmentation in patients with a history of malignant tachyarrhythmias.

BACKGROUND: The identification of patients at increased risk for ventricular tachycardia or ventricular fibrillation (VT/VF) and sudden cardiac death has consequences for therapeutic options and thus may reduce mortality in patients with coronary artery disease (CAD). HYPOTHESIS: We hypothesized that the intra-QRS fragmentation in magnetocardiographic recordings is increased in patients with CAD and with a history of VT/VF. METHODS: Multichannel magnetocardiography (MCG) was carried out in 34 healthy controls, 42 patients with CAD without a history of VT/VF, and 43 patients with CAD and with a history of VT/VF. The intra-QRS fragmentation was quantified by a new fragmentation score. Its spatial distribution was investigated using two-dimensional (2-D) contour maps according to the sensor position of the 49-channel magnetogradiometer. RESULTS: Patients with CAD and with a history of VT/VF had significantly increased QRS fragmentation compared with patients with CAD without VT/VF or controls (72.9+/-37.5, 48.5+/-14.3, and 42.5+/-7.8, respectively: p <0.05). The area of high fragmentation in 2-D contour maps was twice as large in patients with than in those without a history of VT/VF (represented by the number of MCG channels with high fragmentation: 26.3+/-15.5 vs. 12.4+/-9.9, p<0.0001). Patients prone to VT/VF could be identified with a sensitivity of 64% and a specificity of 90%. CONCLUSION: In patients with CAD and with a history of VT/VF, intra-QRS fragmentation is increased and the area of high fragmentation in 2-D contour maps is enlarged. These findings may be helpful in identifying patients with CAD at risk for malignant tachyarrhythmias.

Localization of a ventricular tachycardia-focus with multichannel magnetocardiography and three-dimensional current density reconstruction.

The objective of this case report is to determine the accurate localization of a malignant ventricular tachycardia (VT) focus by combining multichannel magnetocardiographic (MCG) information with morphologic data. The localization was obtained by calculating the three-dimensional current density distribution (3D-CDD) on the left ventricular surface. To estimate the accuracy of this localization technique, examinations of a healthy volunteer were additionally performed. The MCG-signals were recorded in a magnetically shielded room by a 49-channel magnetogradiometer. The corresponding morphologic information was recorded by magnetic resonance tomography (MRT). The coordinate systems were matched with the help of markers. The 3D-CDD was calculated by the Philips CURRY software package. The origin of a malignant VT determined by X-ray images of the ablation catheter position during the electrophysiological examination (EPE), was used as the gold standard. This was then compared with the localization results obtained by the 3D-CDD. It was found that the localization coordinates showed a difference of less than 10 mm.

Magnetocardiographic analysis of the two-dimensional distribution of intra-QRS fractionated activation.

The spatial distribution of high-frequency components in magnetic signals during the QRS complex of the human heartbeat was investigated. Cardiomagnetic signals were recorded simultaneously using 49 first-order magnetogradiometer channels of a multi-SQUID system with a low noise power density. The QRS fragmentation score S, as a measure of the fragmentation of the bandpass-filtered QRS complex, was examined for its sensitivity and specificity to discriminate 34 healthy volunteers, 42 post-myocardial infarction patients and 43 patients with coronary heart disease and with a history of malignant sustained ventricular tachycardia or ventricular fibrillation. The multichannel information was visualized by two-dimensional mapping of the score values of the single channels. By averaging the score values for the seven central channels, S7, the score values of all 49 channels, S49, and calculating the standard deviation for all 49 channels, D49, a higher sensitivity and specificity for detecting patients with ventricular tachycardia (VT) or ventricular fibrillation (VF) was reached than by analysis of a single channel. Combination of these parameters furnishes a sensitivity of 90% and a specificity of 70% for identifying patients prone to VT/VF. The results were compared with diagnostic information obtained from the QRS duration of the signal as well as with results obtained by modified QRS integral mapping.