Multisite dependency of an E3 ligase controls monoubiquitylation-dependent cell fate decisions.

Metazoan development depends on tightly regulated gene expression programs that instruct progenitor cells to adopt specialized fates. Recent work found that posttranslational modifications, such as monoubiquitylation, can determine cell fate also independently of effects on transcription, yet how monoubiquitylation is implemented during development is poorly understood. Here, we have identified a regulatory circuit that controls monoubiquitylation-dependent neural crest specification by the E3 ligase CUL3 and its substrate adaptor KBTBD8. We found that CUL3KBTBD8 monoubiquitylates its essential targets only after these have been phosphorylated in multiple motifs by CK2, a kinase whose levels gradually increase during embryogenesis. Its dependency on multisite phosphorylation allows CUL3KBTBD8 to convert the slow rise in embryonic CK2 into decisive recognition of ubiquitylation substrates, which in turn is essential for neural crest specification. We conclude that multisite dependency of an E3 ligase provides a powerful mechanism for switch-like cell fate transitions controlled by monoubiquitylation

Battery Discharge from Monday to Friday: Background Social Stress at Work is Associated with more Rapid Accumulation of Fatigue

Purpose: This field study investigated the effects of background social stress at work on the weekly course of evening fatigue. Methods: Male employees of a Swiss organisation reported their fatigue after work and at 9 pm in the evening over three weeks. A total of 482 evening fatigue measurements from 34 male participants were subjected to multilevel analysis. Results: Sleep quality in the previous night and fatigue after work predicted evening fatigue. Evening fatigue was not associated with the time spent on daily housework or child care. There was a linear increase in evening fatigue across weekdays and a main effect of workplace social stressors on evening fatigue. Sleep quality during the previous night mediated the link between background social stressors and evening fatigue. Moreover, an interaction between workplace social stressors and working days indicated that fatigue accumulated faster during the working week in those reporting a high level of social stress at work. Conclusion: Social stress at work seems to accelerate the loss of resources over consecutive workdays. The analysis of workplace social stressors and other potential moderators of resource dynamics contributes to our understanding of work-related stress, including the role of background stressors and the temporal dynamics of resource loss

Selective area growth and characterization of InGaN nano-disks implemented in GaN nanocolumns with different top morphologies

This work reports on the morphology control of the selective area growth of GaN-based nanostructures on c-plane GaN templates. By decreasing the substrate temperature, the nanostructures morphology changes from pyramidal islands (no vertical m-planes), to GaN nanocolumns with top semipolar r-planes, and further to GaN nanocolumns with top polar c-planes. When growing InGaN nano-disks embedded into the GaN nanocolumns, the different morphologies mentioned lead to different optical properties, due to the semi-polar and polar nature of the r-planes and c-planes involved. These differences are assessed by photoluminescence measurements at low temperature and correlated to the specific nano-disk geometry

Induced P-wave Superfluidity in Asymmetric Fermi Gases

We show that two new intra-species P-wave superfluid phases appear in two-component asymmetric Fermi systems with short-range S-wave interactions. In the BEC limit, phonons of the molecular BEC induce P-wave superfluidity in the excess fermions. In the BCS limit, density fluctuations induce P-wave superfluidity in both the majority and the minority species. These phases may be realized in experiments with spin-polarized Fermi gases.Comment: published versio

Time Pressure, Time Autonomy, and Sickness Absenteeism in Hospital Employees: A Longitudinal Study on Organizational Absenteeism Records

Background Although work absenteeism is in the focus of occupational health, longitudinal studies on organizational absenteeism records in hospital work are lacking. This longitudinal study tests time pressure and lack of time autonomy to be related to higher sickness absenteeism. Methods Data was collected for 180 employees (45% nurses) of a Swiss hospital at baseline and at follow-up after 1 year. Absent times (hours per month) were received from the human resources department of the hospital. One-year follow-up of organizational absenteeism records were regressed on self-reported job satisfaction, time pressure, and time autonomy (i.e., control) at baseline. Results A multivariate regression showed significant prediction of absenteeism by time pressure at baseline and time autonomy, indicating that a stress process is involved in some sickness absenteeism behavior. Job satisfaction and the interaction of time pressure and time autonomy did not predict sickness absenteeism. Conclusion Results confirmed time pressure and time autonomy as limiting factors in healthcare and a key target in work redesign. Keywords healthcare ; occupational health ; time autonomy ; work absenteeism ; work stres

Experimental Investigation of Reactive-Inert Particulate Matter Detachment from Metal Fibres at Low Flow Velocities and Different Gas Temperatures

The detachment of particle structures from single fibres in gas flow has been investigated only for inert particle structures yet. This study investigates the detachment of particle structures containing reactive components. These reactive components disappear during the reaction and enhance detachment at low flow velocities. Soot was used as the reactive component and glass spheres as the inert component of the particle structure. The soot disappears due to combustion with oxygen leaving only the glass spheres on the fibre. Without reaction, the detachment phenomenon was observed at superficial flow velocities above 1.9 m/s and with reaction at 0.5 m/s. This shows that reacting and disappearing components of the particle structure can enhance detachment

Turbulent fluctuations around Bjorken flow

We study the evolution of local event-by-event deviations from smooth average fluid dynamic fields, as they can arise in heavy ion collisions from the propagation of fluctuating initial conditions. Local fluctuations around Bjorken flow are found to be governed by non-linear equations whose solutions can be characterized qualitatively in terms of Reynolds numbers. Perturbations at different rapidities decouple quickly, and satisfy (after suitable coordinate transformations) an effectively two-dimensional Navier-Stokes equation of non-relativistic form. We discuss the conditions under which non-linearities in these equations cannot be neglected and turbulent behavior is expected to set in.Comment: 4 pages, 2 figures - To appear in the conference proceedings for Quark Matter 2011, May 23 - May 28, Annecy, Franc

Resonance contributions to HBT correlation radii

We study the effect of resonance decays on intensity interferometry for heavy ion collisions. Collective expansion of the source leads to a dependence of the two-particle correlation function on the pair momentum K. This opens the possibility to reconstruct the dynamics of the source from the K-dependence of the measured HBT radii. Here we address the question to what extent resonance decays can fake such a flow signal. Within a simple parametrization for the emission function we present a comprehensive analysis of the interplay of flow and resonance decays on the one- and two-particle spectra. We discuss in detail the non-Gaussian features of the correlation function introduced by long-lived resonances and the resulting problems in extracting meaningful HBT radii. We propose to define them in terms of the second order q-moments of the correlator C(q, K). We show that this yields a more reliable characterisation of the correlator in terms of its width and the correlation strength `lambda' than other commonly used fit procedures. The normalized fourth-order q-moments (kurtosis) provide a quantitative measure for the non-Gaussian features of the correlator. At least for the class of models studied here, the kurtosis helps separating effects from expansion flow and resonance decays, and provides the cleanest signal to distinguish between scenarios with and without transverse flow.Comment: 23 pages, twocolumn RevTeX, 12 eps-figures included, minor changes following referee comment

Nonpointlike Particles in Harmonic Oscillators

Quantum mechanics ordinarily describes particles as being pointlike, in the sense that the uncertainty $\Delta x$ can, in principle, be made arbitrarily small. It has been shown that suitable correction terms to the canonical commutation relations induce a finite lower bound to spatial localisation. Here, we perturbatively calculate the corrections to the energy levels of an in this sense nonpointlike particle in isotropic harmonic oscillators. Apart from a special case the degeneracy of the energy levels is removed.Comment: LaTeX, 9 pages, 1 figure included via epsf optio