Production of a monolithic fuel cell stack with high power density.

The transportation sector is undergoing a technology shift from internal combustion engines to electric motors powered by secondary Li-based batteries. However, the limited range and long charging times of Li-ion batteries still hinder widespread adoption. This aspect is particularly true in the case of heavy freight and long-range transportation, where solid oxide fuel cells (SOFCs) offer an attractive alternative as they can provide high-efficiency and flexible fuel choices. However, the SOFC technology is mainly used for stationary applications owing to the high operating temperature, low volumetric power density and specific power, and poor robustness towards thermal cycling and mechanical vibrations of conventional ceramic-based cells. Here, we present a metal-based monolithic fuel cell design to overcome these issues. Cost-effective and scalable manufacturing processes are employed for fabrication, and only a single heat treatment is required, as opposed to multiple thermal treatments in conventional SOFC production. The design is optimised through three-dimensional multiphysics modelling, nanoparticle infiltration, and corrosion-mitigating treatments. The monolithic fuel cell stack shows a power density of 5.6 kW/L, thus, demonstrating the potential of SOFC technology for transport applications.

2H chemical shift anisotropies from high-field 2H MAS NMR spectroscopy.

2H chemical shift anisotropies (CSAs) have been determined for the first time for polycrystalline samples employing 2H MAS NMR spectroscopy at high magnetic field strength (14.1 T). The 2H CSA is reflected as distinct asymmetries in the manifold of spinning sidebands (ssbs) observed for the two overlapping single-quantum transitions. Least-squares fitting to the manifold of ssbs allows determination of the 2H CSA parameters along with the quadrupole coupling parameters. This is demonstrated for KD2PO4, ND4D2PO4, KDSO4, KDCO3, alpha-(COOD)2, alpha-(COOD)2.2D2O, and boehmite (AlOOD) which exhibit 2H shift anisotropies in the range 13< or =deltasigma< or =27 ppm. For fixed values of the shift anisotropy and the 2H quadrupole coupling it is shown that the precision of the CSA parameters depends strongly on the asymmetry parameter (etaQ) for the quadrupole coupling tensor, giving the highest precision for etaQ approximately 0. The 2H CSA parameters (deltasigma and etasigma) are in good agreement with 1H CSA data reported in the literature for the corresponding protonated samples from 1H NMR spectra employing various homonuclear decoupling techniques. The determination of 2H quadrupole coupling parameters and 2H (1H) CSAs from the same 2H MAS NMR experiment may be particularly useful in studies of hydrogen bonding since the 2H quadrupole coupling constant and the CSA appear to characterize bond lengths in a hydrogen bond in a different manner.

[Hearing loss in children--epidemiology, age at identification and causes through 30 years]. / Høretab hos børn--epidemiologi, identifikation og årsager gennem 30 år.

INTRODUCTION: The survey describes paediatric audiology through 30 years within Copenhagen City concerning epidemiology, age at identification, and causes of permanent hearing impairment in children. MATERIAL AND METHODS: Three longitudinal ten years birth-cohorts [table: see text] are included: 1970-1979 (n = 69); 1980-1989 (n = 64), and 1990-1999 (n = 104) provided with hearing aids, living in the Copenhagen City at the time of the data collection in January 1982, 1992, and 2002. The cohorts 1970-1979 and 1980-1989 have previously been described (1), whereas the 1990-1999 birth cohort is evaluated as part of a prospective registry study. The estimated prevalences are based on the age-matched background population. RESULTS: The estimated prevalence of children provided with hearing aids is 1.97/1000 and the estimated prevalence of congenital hearing impairment is 1.50/1000--without longitudinal changes from 1970-1979 over 1980-1989 to 1990-1999. The proportion of at-risk children in the three-pooled birth-cohorts is 63.3%. The median age at identification of the birth-cohort 1990-1999 was 18 months, 1980-1989 16 months, and 1970-1979 43 months. Only 6% of children with congenital hearing impairment born 1990-1999 are identified at the age of six months, and only 27% at the age of one year. An increase in the prevalence of genetic hearing impairment in the cohort 1970-1979 was demonstrated. DISCUSSION: The prevalence of permanent hearing impairment in childhood through three decades is unchanged, and the age at identification of children with congenital hearing impairments is still delayed. Factors causing hearing impairment demonstrate an increase in genetic factors, which, however, are not significant.