Temperature and magnetic field dependence of the lattice constant in spin-Peierls cuprate CuGeO_3 studied by capacitance dilatometry in fields up to 16 Tesla

We present high resolution measurements of the thermal expansion coefficient and the magnetostriction along the a-axis of CuGeO_3 in magnetic fields up to 16 Tesla. From the pronounced anomalies of the lattice constant a occurring for both temperature and field induced phase transitions clear structural differences between the uniform, dimerized, and incommensurate phases are established. A precise field temperature phase diagram is derived and compared in detail with existing theories. Although there is a fair agreement with the calculations within the Cross Fisher theory, some significant and systematic deviations are present. In addition, our data yield a high resolution measurement of the field and temperature dependence of the spontaneous strain scaling with the spin-Peierls order parameter. Both the zero temperature values as well as the critical behavior of the order parameter are nearly field independent in the dimerized phase. A spontaneous strain is also found in the incommensurate high field phase, which is significantly smaller and shows a different critical behavior than that in the low field phase. The analysis of the temperature dependence of the spontaneous strain yields a pronounced field dependence within the dimerized phase, whereas the temperature dependence of the incommensurate lattice modulation compares well with that of the dimerization in zero magnetic field.Comment: 25 pages, 15 Figs., to appear in Phys. Rev. B55 (Vol.5

Does It Pay To Be a Woman? Labour Demand Effects of Maternity-Related Job Protection and Replacement Incomes

In countries with strong employment protection laws it is often considered to be unwise to hire a woman in childbearing age because she might get pregnant. However, such labour demand e ects of job protection measures related to maternity leave are often rather anecdotal. To provide analytical evidence, this paper studies the impact of changes in maternity-related job protection in Germany on employment opportunities for women in childbearing age without children for whom the observed e ects should be largely demand-related. Exogenous, discrete policy changes in the German labour market of the 1980s and 1990s constitute the setting for a difference-in-differences analysis of the transition into employment as well as wages. The data for this study are taken from the German Socio-Economic Panel and from the German Microcensus. Doubling the job-protected leave period from 6 months to 12 months between 1986 and 1988 led to an approximately 6% lower probability of being hired for women in childbearing age without a university degree.In addition, I nd a 5-10% increase in wages for women in childbearing age associated with the latter reform. Since this effect disappears when controlling for having a child in the future, this may indicate an increased need to signal commitment by increased effort after the reform

We're in this Together: Sensation of the Host Cell Environment by Endosymbiotic Bacteria

Bacteria inhabit diverse environments, including the inside of eukaryotic cells. While a bacterial invader may initially act as a parasite or pathogen, a subsequent mutualistic relationship can emerge in which the endosymbiotic bacteria and their host share metabolites. While the environment of the host cell provides improved stability when compared to an extracellular environment, the endosymbiont population must still cope with changing conditions, including variable nutrient concentrations, the host cell cycle, host developmental programs, and host genetic variation. Furthermore, the eukaryotic host can deploy mechanisms actively preventing a bacterial return to a pathogenic state. Many endosymbionts are likely to use two-component systems (TCSs) to sense their surroundings, and expanded genomic studies of endosymbionts should reveal how TCSs may promote bacterial integration with a host cell. We suggest that studying TCS maintenance or loss may be informative about the evolutionary pathway taken toward endosymbiosis, or even toward endosymbiont-to-organelle conversion.Peer reviewe