The System Iron Oxide-Al2O3 207 of heteropolar bonding than ZrOo, thus agreeing with our theory. I assume that this will be the case.I agree with the interpretation of the various observations on the "region of transformation," and I am of the opinion that one can say something positive about inversion of zirconia only if particle size and degree of disorder are determined exactly. Comments of POI Duwez*The authors should be congratulated for an interesting study of the complex subject of stabilization of zirconia. I agree completely with the conclusions presented in the paper. I would like to add, however, that if the compositions in the ternary system Zr-Ti-0 could be melted without contamination from crucible or atmosphere, many of the apparently contradictory results obtained on sintered specimens could be clarified.I am glad to see that the stability of calcia-stabilized zirconia and the instability of magnesia-stabilized zirconia have been confirmed. The existence of the compound ZrTi04 also has been confirmed. The fact that this compound decomposes when heated in vacuum at 118OoC. means that under these conditions some of the oxygen is probably lost and the composition is not ZrTiOc any more.Phase equilibrium data, obtained by using the quenching technique, are presented for the system iron oxide-A1203 in air and at 1 atm. O2 pressure in the temperature interval 1085" to 1725OC. Stability ranges of the various phases are delineated, and approximate compositions of crystalline and liquid phases are determined. Special attention is focused on the phase Fe203.-AlZO3(ss) and its stability relationships.

Members of the genus Aeromonas are ubiquitous in nature and have increasingly been implicated in numerous diseases of humans and other animal taxa. Although some species of aeromonads are human pathogens, their presence, density, and relative abundance are rarely considered in assessing water quality. The objectives of this study were to identify Aeromonas species within Lake Erie, determine their antibiotic resistance patterns, and assess their potential pathogenicity. Aeromonas strains were isolated from Lake Erie water by use of Aeromonas selective agar with and without tetracycline and ciprofloxacin. All isolates were analyzed for hemolytic ability and cytotoxicity against human epithelial cells and were identified to the species level by using 16S rRNA gene restriction fragment length polymorphisms and phylogenetic analysis based on gyrB gene sequences. A molecular virulence profile was identified for each isolate, using multiplex PCR analysis of six virulence genes. We demonstrated that Aeromonas comprised 16% of all culturable bacteria from Lake Erie. Among 119 Aeromonas isolates, six species were identified, though only two species (Aeromonas hydrophila and A. veronii) predominated among tetracycline-and ciprofloxacin-resistant isolates. Additionally, both of these species demonstrated pathogenic phenotypes in vitro. Virulence gene profiles demonstrated a high prevalence of aerolysin and serine protease genes among A. hydrophila and A. veronii isolates, a genetic profile which corresponded with pathogenic phenotypes. Together, our findings demonstrate increased antibiotic resistance among potentially pathogenic strains of aeromonads, illustrating an emerging potential health concern.

Berries of grapevine (Vitis spp.) have a limited window of susceptibility to Uncinula necator, the causal agent of grapevine powdery mildew, until the onset of ontogenic resistance approximately 2 to 3 weeks postbloom. This phenomenon has been demonstrated in several cultivars of V. vinifera and in V. labruscana ‘Concord’, which all exhibited a similar duration of susceptibility. To identify genetic variation for ontogenic resistance, we screened a diverse collection of Vitis species and interspecific hybrids maintained in the USDA-ARS cold-hardy Vitis germplasm collection in Geneva, NY. Of the 79 genotypes whose fruit clusters were screened for susceptibility to powdery mildew under field conditions, 50 exhibited a high level of constitutive resistance to powdery mildew and did not develop more than trace levels of disease when inoculated, irrespective of the stage of berry development at inoculation. Twenty-four genotypes exhibited a significant gain of resistance as berries aged. This ontogenic resistance was conserved across four species and several interspecific hybrids of Vitis spp., although the timing of the onset of ontogenic resistance varied by genotype. The mechanism of ontogenic resistance was examined for four genotypes. Similar to previous studies, ontogenic resistance greatly reduced the incidence of successful penetration. Despite the broad conservation of ontogenic resistance across species, one genotype (V. rupestris ‘R-65-44’) remained susceptible past the onset of ripening, over 1 month later than reported previously for V. vinifera and V. labruscana. Variation in the resistance phenotype was observed among the rachis, pedicels, and berries within clusters of the majority of genotypes studied. The genetic variation in ontogenic resistance, in particular the discovery of a genotype in which berries remain susceptible as they mature, will facilitate further study of the inheritance and molecular basis of ontogenic resistance.

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A near-peer departmental induction using simulated ward rounds may improve the preparedness of junior doctors for their role within a new department, potentially improving patient care and the junior doctors' learning experiences.

The trajectory of Singapore's population size and composition can be mapped out with its progression through the various phases of demographic transition from high birth and death rates in the post-war years to very low birth and death rates today, all within the context of rapid economic and social development that has taken place in the past 50 years. Population planning has been integral in Singapore's national development strategy, balancing the economy's needs for more and better qualified workers with social considerations such as the dependency burden and the integration of large numbers of foreigners in a global city-state. This paper considers Singapore's population and manpower planning policies, with an account of the country's passage through the various stages of its demographic transition, and how its working age population composition has evolved. Population and labor force policies are examined with specific consideration of the social, economic and political implications resulting from those policy choices. A final section considers the challenges for the future stemming from these demographic trends.

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Downy mildew (Plasmopara viticola) is a significant problem in grape vineyards throughout the growing season. Control of downy mildew is carried out with a combination of host tolerance and chemical applications. Even in vineyards planted with very tolerant varieties (e.g., Concord), control is important in years with ideal pathogen conditions. Fungicides with a single mode of action possess a very high potential for the development of resistance. Resistance has been observed often in the Quinone outside inhibitor (QoI) fungicides, such as strobilurins. We ascertained the levels of QoI resistance in downy mildew colonies on diseased leaves using CAPS-PCR to detect the glycine to alanine mutation (G143A) known to confer a qualitative level of resistance in fungal pathogens. Our data uncovered a small percentage of samples that contain G143A, suggesting an overall low level of QoI resistance. The low prevalence of the resistant single nucleotide polymorphism (SNP) suggests that QoI fungicides should remain a viable control mechanism in Lake Erie vineyards. Additionally, it appears that a viticultural region where tolerant hosts predominant and QoI use is minimal, resistance buildup in the pathogen population will be minimal. Accepted for publication 15 January 2013. Published 22 April 2013.