Energy shifts in photoemission lines during the tetragonal- to cubic-phase transition in BaTiO3 single crystals and systems with CoFe2O4 and NiFe2O4 overlayers.

In BaTiO3 the phase transition from tetragonal to cubic is connected with the disappearance of the ferroelectric polarization. In photoelectron spectroscopy huge transient shifts in the binding energies of all core-level photoemission lines have been observed while heating and cooling through the Curie temperature. Excitation energies from 2 keV to 6 keV have been used to show this to be a bulk effect and not a surface effect alone. These observations are discussed in terms of charging, which results from the disappearance of the ferroelectric polarization. This mechanism has previously been proposed as the origin of electron emission in ferroelectric materials. Besides the jump-like shifts, additional permanent shifts in binding energies have been observed for the tetragonal and the cubic phase. These experimental shifts have been related to theoretical ones from ab initio calculations. In addition to BaTiO3 single crystals, systems with CoFe2O4 and NiFe2O4 overlayers on BaTiO3 have been investigated. The low conductivity of these layers sets them apart from metallic overlayers like Fe or Co, where the shifts are suppressed. This difference adds further support for charging as the origin of the effect.

XMCD studies of thin Co films on BaTiO3.

Different layer thicknesses of cobalt ranging from 2.6 Å (1.5 ML) up to 55 Å (30.5 ML) deposited on ferroelectric BaTiO3 have been studied regarding their magnetic behavior. The layers have been characterized using XMCD spectroscopy at remanent magnetization. After careful data analysis the magnetic moments of the cobalt could be determined using the sum rule formalism. There is a sudden and abrupt onset in magnetism starting at thicknesses of 9 Å (5 ML) of cobalt for measurements at 120 K and of 10 Å (5.5 ML) if measured at room temperature. Initial island growth and subsequent coalescence of Co on BaTiO3 is suggested to explain the sudden onset. In that context, no magnetically dead layers are observed.

Decreased rate of back injuries through a wellness program for offshore petroleum employees.

High rates of injury, particularly those for back injuries, at an offshore petroleum unit were addressed through an intensive wellness program initiated in 1991. The number of all types of injuries, including back injuries, decreased between 1991 and 1995. The number of back injuries decreased from nine in 1987 to four in 1992 and was zero in 1993. Although there are inadequate data to provide power for a significant result, other criteria suggest a causal relationship. The results are consistent with the few published studies that suggest a decrease in the number of injuries in association with exercise and perhaps with modification of psychosocial risk factors. Calculations suggest a cost savings of over $800,000 and a return on investment of $2.51, as well as avoidance of pain and injury.

[A new method in the determination of individual delay time in bolus application in spiral CT]. / Neues Verfahren zur Bestimmung der individuellen Verzögerungszeit für die Bolusapplikation im Spiral-CT.

Helical-CT examinations, particularly CT angiography, require precise timing between the examination procedure and the individual dynamics of contrast medium distribution in the arteriovenous system of the patient. The necessary delay between contrast medium injection and onset of has usually been either estimated or determined by means of an additional helical CT examination. The present paper introduces a new technique which allows bolus analysis without an additional scan. Prior to a CT angiography with 10 patients, two techniques for bolus analysis (BA) were compared. Prior to diagnostic contrast medium enhanced examination, a native (BA I) and a dynamic (BA II) examination were performed. Ten seconds prior to the start of each examination, a 10 ml test bolus was applied with an injection flow rate of 3 ml/s. Both examinations lasted for 30 s. During BA I, increase in attenuation in the aorta was compared at different sites, during BA II consistently at the same site. Comparison of the individual peak times yielded a coefficient of correlation of r = 0.926. The median value for BA I was 18.4 +/- 5.4 s and 19.2 +/- 4.5 s for BA II. The difference between measurement of peak time was 1.2 +/- 1.16 s. This modified technique for bolus analysis during the primary native scan of the upper abdominal organs permits calculation of the required individual delay time between contrast medium application and scan start: no additional examination is required and the method can be performed with any helical CT unit.

Measurement of pulmonary parenchymal attenuation: use of spirometric gating with quantitative CT.

A new approach to reproducible measurement of lung attenuation and structure by means of respiratory-gated computed tomography (CT) was developed. The patient breathes through a microcomputer-controlled pocket spirometer during the complete CT examination, starting with a measurement of the vital capacity. At a user-selected respiratory level, the CT scan is triggered and air flow is inhibited mechanically. To exclude operator-related reproducibility errors, evaluation is based on semiautomated algorithms that isolate lung parenchyma by fast contour tracing. In a study on one volunteer, measurement of lung attenuation changed by a factor of about 2.6 (-895 to -730 HU) as a function of inspirational status. Reproducibility on the order of 5% or better can be achieved only with tight spirometric control of respiration.