Effect of columnar defects on theJ c anisotropy of YBa2Cu3O7−δ thin films and YBa2Cu3O7−δ /PrBa2Cu3O7−δ multilayers

Epitaxial YBa₂Cu₃O_7?δ thin films (YBCO) and YBa₂Cu₃O_7?δ /PrBa₂Cu₃O_7?δ multilayers (Y/Pr) were irradiated with high-energy heavy ions (770 Mev²⁰⁸Pb) under various directionsφ relative to thec-axis. The irradiation resulted in columnar defects tilted byφ from thec-axis. The angular dependence of their pinning activity was studied by measuring the anisotropy of the critical current density. TheJ _c (B, T,?) behavior of the irradiated YBCO thin films showed an additional peak, which exceeds the intrinsic pinning peak, exactly at the irradiation direction. The Y/Pr multilayers, however, showed an isotropicT _c -enhancement by a factor of 5, without any additional structure in theJ _c(B, T,?) curve.     

Cover Picture: Closing the Gap Between Self‐Assembly and Microsystems Using Self‐Assembly,Transfer, and Integration of Particles (Adv. Mater. 20/2005)

The cover shows 100 μm diameter glass spheres covered by a grid of hexagonally packed polystyrene beads. Wolf and co‐workers placed the 500 nm diameter polystyrene beads onto the larger spheres using the self‐assembly, transfer, and integration (SATI) process that they report on p. 2438. The cover illustrates the capability of SATI to process uneven surfaces in addition to the planar substrates discussed in the article. The carrier that holds the smaller beads deforms during their transfer onto the larger spheres, so that on the larger spheres patterned “caps” are formed. Using this process, which is compatible with standard microfabrication techniques, a variety of particle assemblies can be achieved.     

Pool boiling heat transfer of carbon dioxide on a horizontal tube

Carbon dioxide is again becoming an important refrigerant. While the thermophysical properties are well known there is a lack of data on its heat transfer characteristics.

In this study, heat transfer coefficients for nucleate boiling of carbon dioxide are determined using a standard apparatus for the investigation of pool boiling based on a set-up from Karlsruhe [D. Gorenflo, J. Goetz, K. Bier. Vorschlag für eine Standard-Apparatur zur Messung des Wärmeübergangs beim Blasensieden. Wärme-und Stoffübertragung 16 (1982), 69–78; J. Goetz, Entwicklung und Erprobung einer Normapparatur zur Messung des Wärmeübergangs beim Blasensieden. Dissertation Universität Karlsruhe (1980).] and built at our institute. Electrically heated horizontal cylinders with an outer diameter of 16 mm and a length of 100 mm are used as heating elements. Measurements with constant heat flux are performed for different wall materials and surface roughnesses. The heat transfer is investigated within the pressure range of 0.53≤ p ≤1.43 MPa (0.072≤ p/p_c ≤0.190) and a temperature range of −56≤ t ≤−30 °C, respectively. Heat fluxes of up to 80,000 W m⁻² are applied.

The influences of wall material and roughness on the heat transfer coefficient are evaluated separately. The obtained coefficients are compared to generally accepted correlations and to experimental results of other authors, who used similar configurations with copper tubes and carbon dioxide. These are the only previous experimental data, which could be found. Results for copper, stainless steel and aluminium as wall materials are presented.     

Integration of a three-stage expander into a CO2 refrigeration system

The inclusion of an expander with work recovery provides two advantages for transcritical CO₂ refrigeration cycles: the COP is improved and the exhaust pressure of the main compressor is lowered. Several designs of expanders have been proposed for this application and some prototypes have been tested already. In our laboratory a three-stage expander has been developed, which replaces the throttle valve of the normal refrigeration cycle and expands into the two-phase region. For optimum integration into the overall system it is proposed to install a vapour-liquid separator between the second and third stage of expansion. The vapour is guided back to the third expander stage whereas the liquid is supplied to the cooling stations via thermostatic or electronic expansion valves.     

Seat position and the risk of serious thoracoabdominal injury in lateral motor vehicle crashes

CONTEXT: Previous studies have suggested that motor vehicle occupants seated on the near-side of a lateral impact have a higher proportion of thoracoabdominal injuries. However, due to limitations in previous studies, the true association between seat position, side of lateral impact, and thoracoabdominal injury is unclear. OBJECTIVE: To assess the relationship between seat position (i.e., near-side, middle-seat, and far-side, regardless of row), side of lateral motor vehicle crash (MVC), and serious thoracoabdominal injury after adjusting for important crash factors. DESIGN: National population-based cohort of adult subjects involved in MVCs and included in the National Automotive Sampling System Crashworthiness Data System database (NASS CDS) from 1995 to 2003. PATIENTS: Occupants aged > or =16 years involved in MVCs where the highest external deformation of the vehicle was located on the right or left side (i.e., lateral). MAIN OUTCOME MEASURE: Serious thoracic or abdominal injury, defined as an Abbreviated Injury Scale (AIS) > or =3 in the thoracic or abdominal body region. RESULTS: Fifteen thousand, one hundred and sixty persons involved in primary lateral MVCs were represented in the NASS CDS database during the 9-year period. There were 1867 (2%) persons with serious thoracic injuries and 507 persons (0.5%) with serious abdominal injuries. In multivariable logistic regression models that adjusted for important crash factors and the NASS CDS sampling design, seat position was a strong effect modifier of the association between side of lateral impact and serious thoracic (p<0.0001) and abdominal (p=0.0009) injury, with the risk of serious thoracic and abdominal injury highest for occupants seated on the near-side of the crash. The mean probability of injury was higher for near-side and middle-seat occupants compared to far-side occupants, and the probability of thoracic injury was approximately four times higher than that of abdominal injury for all seat positions. CONCLUSIONS: There is a strong, synergistic relationship between seat position and side of lateral MVC in assessing risk of serious thoracic and abdominal injury among adult occupants. The probability of serious thoracoabdominal injury increases with increasing proximity of seat position to side of the crash and the risk of thoracic injury is higher than abdominal injury for all seat positions.     

Energy sensitive detection of heavy ions with transition edge calorimeters

Status and results of a research project are reported, which aims at developing calorimetric low temperature detectors for heavy ions. The special conditions for the detection of energetic heavy ions are discussed. The response of an aluminium transition edge calorimeter, operated at about1.5K, to the impact of heavy ions was investigated. The observed energy resolutions E/E=3.9×10^–3for5.9MeV/u ²⁰⁸ Pb-ions, E/E=1.6×10^–3for4.8MeV/u ⁵⁸ Ni-ions and E/E=4.3×10^–3for100MeV/u ²⁰ Ne-ions are most probably not yet limited by the intrinsic detector resolution. The present results already represent an improvement over conventional solid state detectors and ionization chambers.     

Monitoring of cellular signalling and metabolism with modular sensor-technique: the PhysioControl-Microsystem (PCM)

This cohort study of 725 women examined the health, occupational, and social factors that contribute to quitting work in two transnational electronics maquiladoras (assembly plants) in Tijuana, Mexico. The estimated cumulative probabilities of quitting were 68% and 81% by 1 and 2 years of employment. After adjusting for other factors, women who had a history of smoking or surgery and those who returned to work after a paid leave due to illness were more likely to quit. In contrast, women with a history of chronic illness had lower quitting rates. The nationality of the company and the work shift also significantly influenced quitting rates, but demographic characteristics and health care visits did not have a significant effect. Women selectively leave maquiladora employment, often due to health-related events. The healthy worker effect is difficult to measure in a mobile population with high turnover.