Bubble-assisted Leptogenesis

We explore the possibility of embedding thermal leptogenesis within a first-order phase transition (FOPT) such that RHNs remain massless until a FOPT arises. Their sudden and violent mass gain allows the neutrinos to become thermally decoupled, and the lepton asymmetry generated from their decay can be, in principle, free from the strong wash-out processes that conventional leptogenesis scenarios suffer from, albeit at the cost of new washout channels. To quantify the effect of this enhancement, we consider a simple setup of a classically scale-invariant $B-L$ potential, which requires three RHNs with similar mass scales, in the ``strong-washout'' regime of thermal leptogenesis. Here we find that parameter space which requires $M_N\sim 10^{11}\text{ GeV}$ without bubble assistance is now predicted at $M_N \sim 5\times 10^9 \text{ GeV}$ suggesting a sizeable reduction from bubble effects. We numerically quantify to what extent such a framework can alleviate strong-washout effects and we find the lower bound on the RHN mass, $M_N \sim 10^{7}\text{ GeV}$, below which bubble-assisted leptogenesis cannot provide an enhancement. We also study the signature possibly observable at GW terrestrial interferometers and conclude that bubble-assisted leptogenesis models with relatively light masses, $M_N \lesssim 5\times 10^9 \text{ GeV}$ may be probable.Comment: 27 pages, 8 figures, published version, references added, discussion slightly change

Discontinuous Transitions Towards Vortex Condensates in Buoyancy-Driven Rotating Turbulence: Analogies with First-Order Phase Transitions

Using direct numerical simulations of rotating Rayleigh-B\'enard convection, we explore the transitions between turbulent states from a 3D flow state towards a quasi-2D condensate known as the large-scale vortex (LSV). We vary the Rayleigh number $Ra$ as control parameter and study the system response (strength of the LSV) in terms of order parameters assessing the energetic content in the flow and the upscale energy flux. By sensitively probing the boundaries of the domain of existence of the LSV, we find discontinuous transitions and we identify the presence of a hysteresis loop as well as nucleation & growth type of dynamics, manifesting a remarkable correspondence with first-order phase transitions in equilibrium statistical mechanics. We show furthermore that the creation of the condensate state coincides with a discontinuous transition of the energy transport into the largest mode of the system.Comment: 10 pages, 5 figure

The robust wall modes and their interplay with bulk turbulence in confined rotating Rayleigh-B\'enard convection

In confined rotating convection, a strong zonal flow can develop close to the side wall with a modal structure that precesses anti-cyclonically (counter to the applied rotation) along the side wall. It is surmised that this is a robust non-linear evolution of the wall modes observed before the onset of bulk convection. Here, we perform direct numerical simulations of cylindrically confined rotating convection at high rotation rates and strong turbulent forcing. Through comparison with earlier work, we find a fit-parameter-free relation that links the angular drift frequency of the robust wall mode observed far into the turbulent regime with the critical wall mode frequency at onset, firmly substantiating the connection between the observed boundary zonal flow and the wall modes. Deviations from this relation at stronger turbulent forcing suggest early signs of the bulk turbulence starting to hamper the development of the wall mode. Furthermore, by studying the interactive flow between the robust wall mode and the bulk turbulence, we identify radial jets penetrating from the wall mode into the bulk. These jets induce a large scale multipolar vortex structure in the bulk turbulence, dependent on the wavenumber of the wall mode. In a narrow cylinder the entire bulk flow is dominated by a quadrupolar vortex driven by the radial jets, while in a wider cylinder the jets are found to have a finite penetration length and the vortices do not cover the entire bulk. We also identify the role of Reynolds stresses in the generation of zonal flows in the region near the sidewall.Comment: 14 pages, 8 figure

Following the migration of glass eel and three-spined stickleback passing Europe’s largest pumping station and world’s largest sluice

In order to quantify abundance, to study migration behaviour and to evaluate different fish passages along a 26 km long canal (North Sea Canal) in the Netherlands, a mark recapture experiment was carried out by tagging 6750 glass eel (Anguilla anguilla), 625 three-spined stickleback (Gasterosteus aculeatus) caught in marine environment and 625 three-spined stickleback caught in brackish environment in spring 2018. To reach the canal, migratory fish must pass a large complex of four large sea sluices, spill gates and Europe’s largest pumping station. Twenty five groups could be distinguished using different combinations of fluorescent colours of Visible Implant Elastomer Tags. The majority of the marked fish were released at the sea side and just behind a large tidal barrier (each group: 2000 glass eel and 500 stickleback). In addition, different groups of both species were caught and released locally at different sites along the canal to evaluate fish passage efficiency. Fish were recaptured in an extensive netting program of volunteers along the canal, twelve especially designed glass eel monitoring devices and professional fisherman who monitored fish passages along pumping stations or sluices. Stickleback originally caught in brackish environment showed higher recapture rate (7.6%) compared to stickleback caught in the marine environment (2.8%). Also, fastest average migration speed was estimated on 0.09 m/s and migratory delay at the tidal barrier was limited since difference groups were recaptured in comparable ratio’s and migration speeds. Glass eel were recaptured along almost all monitoring locations along the canal. Fastest, average migration speed was estimated at 0.02 m/s and the furthermost recapture was 28 km from release site after 26 days (average speed 0.01 m/s). Migratory delay at the tidal barrier seemed limited, however some individuals were caught after 23 days at the sea side and others were flushed out by the spill gates

The relationship between managers' goal-setting styles and subordinates' goal commitment

CITATOIN: Van Lill, X., Roodt, G. & De Bruin, G. P. 2020. The relationship between managers' goal-setting styles and subordinates' goal commitment. South African Journal of Economic and Management Sciences, 23(1):a3601, doi:10.4102/sajems.v23i1.3601.The original publication is available at https://sajems.orgBackground: Convincing employees to set aside their self-interests and commit to collective goals is essential for the effective functioning of organisations. It is critical that the impact of different managerial goal-setting styles, and the associated impressions of fair interpersonal treatment in the workplace, is understood from subordinates’ perspective. This might clarify the psychological mechanisms involved in motivating subordinates to commit to organisational goals. Aim: The primary aim of this article is to determine the relationship between managers’ goal-setting styles and subordinates’ goal commitment. The secondary aim is to determine whether this relationship is mediated by interactional justice. Setting: A total of 451 working adults completed an online or paper-and-pen survey. Methods: A mediator model was conducted in structural equation modelling with maximum likelihood estimation and Bollen-Stine bootstrapping, with 5000 bootstrap resamples, to test the hypotheses. Results: The perception that managers are deliberative had the greatest positive direct relationship with subordinates’ goal commitment, followed by the directive style. Subordinates’ perception of managers as complaisant, in turn, were unrelated to goal commitment (amotivational), whereas the perception of managers as hostile had a negative relationship with goal commitment. Informational justice, not interpersonal justice, emerged as the only mediating variable. Conclusion: Managers should be encouraged to actively seek feedback from subordinates on their goal-setting styles. Managers can accordingly adapt their behaviour to effectively motivate subordinates to commit to organisational goals.https://sajems.org/index.php/sajems/article/view/3601Publisher's versio

One job, one deal...or not: do generations respond differently to psychological contract fulfillment?

This paper investigates generational differences in the relations between psychological contract fulfillment and work attitudes. Data were collected from a sample of 909 employees in the Dutch service sector. Structural equation modeling analyses were used to test the moderating effects of generational differences on the influence of psychological contract fulfillment on affective commitment and turnover intention. The relationship between psychological contract fulfillment and these work outcomes was moderated by generational differences. Furthermore, results indicate that different generations respond differently to different aspects of psychological contract fulfillment, such as career development, job content, organizational policies, social atmosphere and rewards. The study provides evidence that generational differences impact the reciprocal relationship between employer and employee. Results from this study suggest that Baby Boomers and Generation X may be more motivated by social atmosphere, whereas Generation Y may be more motivated by job content and career development. Fair organizational policies are particularly motivating to Generation X, and providing rewards, though more important to Generation Y, seem mostly unrelated to work outcomes. This article is the first to study the moderation of generational differences in the relationships between psychological contract fulfillment and work outcomes

The use of quality information by general practitioners: does it alter choices? A randomized clustered study

Background: Following the introduction of elements of managed competition in the Netherlands in 2006, General Practitioners (GPs) and patients were given the role to select treatment hospital using public quality information. In this study we investigate to what extent hospital preferences of GP's are affected by performance indicators on medical effectiveness and patient experiences. We selected three conditions: breast cancer, cataract surgery, and hip and knee replacement. Methods. After an inquiry 26 out of 226 GPs in the region signed up to participate in our study. After a 2:1 randomization, we analyzed the referral patterns in the region using three groups of GPs: GPs (n=17) who used the report cards and received personal clarification, GPs that signed up for the study but were assigned to the control group (n=9), and the GPs outside the study (n=200).We conducted a difference in differences analysis where the choice for a particular hospital was the dependent variable and time (2009 or 2010), the sum score of the CQI, the sum score of the PI's and dummy variables for the individual hospitals were used as independent variables. Results: The analysis of the conditions together and cataract surgery and hip and knee replacement separately, showed no significant relationships between the scores on the report cards and the referral patterns of the GPs. For breast cancer our analysis revealed that GPs in the intervention group refer 1.0% (p=0.01) more to hospitals that score one percent point better on the indicators for medical effectiveness. Conclusion: Our study provides empirical evidence that GP referral patterns were unaffected by the available quality information, except for the outcome indicators for breast cancer care that were presented. This finding was surprising since our study was designed to identify changes in hospital preference (1) amongst the most motivated GP's, (2) that received personal clarification of the performance indicators, and (3) selected indicators/conditions from a large set of indicators that they believed were most important. This finding may differ when quality information is based on outcome indicators with a clinically relevant difference, as shown by our indicators for breast cancer treatment. We believe that the current set of (largely process) hospital quality indicators do not serve the GP's information needs and consequently quality plays little role in the selection of hospitals for treatment. © 2013 Ikkersheim and Koolman; licensee BioMed Central Ltd