A rigidity property of asymptotically simple spacetimes arising from conformally flat data

Given a time symmetric initial data set for the vacuum Einstein field equations which is conformally flat near infinity, it is shown that the solutions to the regular finite initial value problem at spatial infinity extend smoothly through the critical sets where null infinity touches spatial infinity if and only if the initial data coincides with Schwarzschild data near infinity.Comment: 37 page

Selective cerebral hypothermia for post-hypoxic neuroprotection in neonates using a solid ice cap

No Abstract. South African Medical Journal Vol. 96(9) (Part 2) 2006: 976-98

Age at work:Explaining variation in frames of older employees in corporate and news media

Despite the fact that workforce aging is recognized as a key social and economic concern of developed countries, previous research has largely neglected the role of corporate and news media in the debate about this topic. Relying on a content analysis of five Dutch newspapers and the corporate media of 50 Dutch organizations (N = 1328), this study traces variation in frames of older workers’ employability. Results reveal that organizations in their corporate media attempt to avoid associations with problems related to older employees and highlight the solutions they offer, while news media are more inclined to problematize the issue and victimize older employees. This study elucidates our understanding of how corporate and news media communicatively deal with older workers’ employability, and how key actors drive frame-formation processes in both domains

Divergent evolution of protein conformational dynamics in dihydrofolate reductase.

Molecular evolution is driven by mutations, which may affect the fitness of an organism and are then subject to natural selection or genetic drift. Analysis of primary protein sequences and tertiary structures has yielded valuable insights into the evolution of protein function, but little is known about the evolution of functional mechanisms, protein dynamics and conformational plasticity essential for activity. We characterized the atomic-level motions across divergent members of the dihydrofolate reductase (DHFR) family. Despite structural similarity, Escherichia coli and human DHFRs use different dynamic mechanisms to perform the same function, and human DHFR cannot complement DHFR-deficient E. coli cells. Identification of the primary-sequence determinants of flexibility in DHFRs from several species allowed us to propose a likely scenario for the evolution of functionally important DHFR dynamics following a pattern of divergent evolution that is tuned by cellular environment

Photoionization in the time and frequency domain

Ultrafast processes in matter, such as the electron emission following light absorption, can now be studied using ultrashort light pulses of attosecond duration ($10^{-18}$s) in the extreme ultraviolet spectral range. The lack of spectral resolution due to the use of short light pulses may raise serious issues in the interpretation of the experimental results and the comparison with detailed theoretical calculations. Here, we determine photoionization time delays in neon atoms over a 40 eV energy range with an interferometric technique combining high temporal and spectral resolution. We spectrally disentangle direct ionization from ionization with shake up, where a second electron is left in an excited state, thus obtaining excellent agreement with theoretical calculations and thereby solving a puzzle raised by seven-year-old measurements. Our experimental approach does not have conceptual limits, allowing us to foresee, with the help of upcoming laser technology, ultra-high resolution time-frequency studies from the visible to the x-ray range.Comment: 5 pages, 4 figure

Painleve-Gullstrand Coordinates for the Kerr Solution

We construct a coordinate system for the Kerr solution, based on the zero angular momentum observers dropped from infinity, which generalizes the Painleve-Gullstrand coordinate system for the Schwarzschild solution. The Kerr metric can then be interpreted as describing space flowing on a (curved) Riemannian 3-manifold. The stationary limit arises as the set of points on this manifold where the speed of the flow equals the speed of light, and the horizons as the set of points where the radial speed equals the speed of light. A deeper analysis of what is meant by the flow of space reveals that the acceleration of free-falling objects is generally not in the direction of this flow. Finally, we compare the new coordinate system with the closely related Doran coordinate system.Comment: 6 pages; v2: new section, matches final published version; v3: sign error in the expression of the function delta correcte

Precarious employment amidst global crises:Career shocks, resources and migrants' employability

PurposeThe authors conducted 22 in-depth longitudinal interviews with 11 Hungarian migrant workers in the Dutch logistics sector, before and during the COVID-19 crisis, using thematic analysis and visual life diagrams to interpret them.Design/methodology/approachThis study aims to contribute to conservation of resources theory, by exploring how global crises influence the perceived employability of migrant workers in low-wage, precarious work.FindingsThe authors find that resources are key in how migrants experience the valence of global crises in their careers and perceive their employability. When unforeseen consequences of the COVID-19 crisis coincided with migrants' resource gain spirals, this instigated a positively valenced career shock, leading to positive perceptions of employability. Coincidence with loss spirals led to negative perceptions.Research limitations/implicationsThe authors contribute to careers literature by showing that resources do not only help migrants cope with the impact of career shocks but also directly influence the valence of global crises in their perceived employability and careers.Originality/valueInterestingly, when the COVID-19 crisis did not co-occur with migrants' resource gain and loss spirals, migrants experienced resource stress (psychological strain induced by the threat or actual loss of resources) and no significant change in their perceptions of employability