DO THE PHASES OF THE BUSINESS CYCLE DIE OF OLD AGE?

The paper re-examines the issue of duration dependence in the Australian classical and growth business cycles in light of the somewhat surprising results obtained recently by Cashin and Ouliaris (2004). In so doing the authors use the multinomial logit regime switching modelling approach of Layton and Smith (2003). The paper also represents an extension of the earlier work on the issue undertaken by Bodman (1998); the key extensions being that the issue is framed within an explicit established business cycle chronology, a leading index is also included within the analysis, and the growth cycle, in addition to the classical cycle, is considered. Strong evidence of duration dependence is found for periods of recession within the classical cycle and for both phases of the growth cycle. Moderate evidence of duration dependency is also found for periods of classical cycle expansion. However, the evidence in this regard is significantly reduced once movements in the leading index are included in the analysis with its movements exhibiting strong power in predicting the termination of classical business cycle expansions. For growth cycles, duration dependence symmetry is found across both phases of the cycle. Copyright Blackwell Publishing Ltd/University of Adelaide and Flinders University 2005..

Absolute metabolite quantification by in vivo NMR spectroscopy:II. A multicentre trial of protocols for in vivo localised proton studies of human brain

We have performed a multicentre trial to assess the performance of three techniques for absolute quantification of cerebral metabolites using in vivo proton nuclear magnetic resonance (NMR). The techniques included were 1) an internal water standard method, 2) an external standard method based on phantom replacement, and 3) a more sophisticated method incorporating elements of both the internal and external standard approaches, together with compartmental analysis of brain water. Only the internal water standard technique could be readily implemented at all participating sites and gave acceptable precision and interlaboratory reproducibility. This method was insensitive to many of the experimental factors affecting the performance of the alternative techniques, including effects related to loading, standing waves and B1 inhomogeneities; and practical issues of phantom positioning, user expertise and examination duration. However, the internal water standard method assumes a value for the concentration of NMR-visible water within the spectroscopic volume of interest. In general, it is necessary to modify this assumed concentration on the basis of the grey matter, white matter and cerebrospinal fluid (CSF) content of the volume, and the NMR-visible water content of the grey and white matter fractions. Combining data from 11 sites, the concentrations of the principal NMR-visible metabolites in the brains of healthy subjects (age range 20-35 years) determined using the internal water standard method were (mean ± SD): [NAA] = 10.0 ± 3.4 mM (n = 53), [tCho] = 1.9 ± 1.0 mM (n = 51), [Cr + PCr] = 6.5 ± 3.7 mM (n = 51). Evidence of system instability and other sources of error at some participating sites reinforces the need for rigorous quality assurance in quantitative spectroscopy