The local density of matter mapped by Hipparcos

We determine the velocity distribution and space density of a volume complete sample of A and F stars, using parallaxes and proper motions from the Hipparcos satellite. We use these data to solve for the gravitational potential vertically in the local Galactic disc, by comparing the Hipparcos measured space density with predictions from various disc models. We derive an estimate of the local dynamical mass density of 0.102 +/- 0.010 solar masses per cubic parsec which may be compared to an estimate of 0.095 solar masses per cubic parsec in visible disc matter. Our estimate is found to be in reasonable agreement with other estimates by Creze et al. and Pham, also based on Hipparcos data. We conclude that there is no compelling evidence for significant amounts of dark matter in the disc.Comment: 9 pages, 7 figures, accepted by MNRA

White dwarfs and Galactic dark matter

We discuss the recent discovery by Oppenheimer et al (2001) of old, cool white dwarf stars, which may be the first direct detection of Galactic halo dark matter. We argue here that the contribution of more mundane white dwarfs of the stellar halo and thick disk would contribute sufficiently to explain the new high velocity white dwarfs without invoking putative white dwarfs of the dark halo. This by no means rules out that the dark matter has been found, but it does constrain the overall contribution by white dwarfs brighter than M_V ~ 16 to significantly less than 1% of the Galactic dark matter. This work confirms a similar study by Reyle et al (2001).Comment: 8 pages, 8 figures. MNRAS style fil

Psychological factors and communication skills training in intensive care medical staff

Background. Intensive care settings have been shown to present a demanding work setting with health related and work-related consequences for intensive care medical staff. The health-related consequences observed are high levels of burnout, traumatic stress, symptoms of anxiety, depression, and fatigue. Specific stressors mentioned by staff is high workload, moral distress, end-of-life issues, and interpersonal issues/conflicts with colleagues, patients, and relatives. During the covid-19 pandemic, the need for healthcare organizations to attend to the occupational psychological health of staff has been evidently clear. Although, the prevalence of stress in intensive care has been previously observed and reported on, at least since the 70s. Purpose and aims. Overall purpose of thesis was threefold; to improve knowledge on occupational psychological health among healthcare staff, particularly in intensive care settings, to develop a behavioural intervention to improve communication skills and management of distress to enhance occupational health, and to evaluate the implementation of psychological support to ICU staff. The thesis included four studies and the specific aim of study I was to evaluate the reliability and validity of a Swedish version of the Workrelated Acceptance and Action Questionnaire (WAAQ), a self-report questionnaire measuring psychological flexibility at work. Study II evaluated the relationship between psychological flexibility (measured by WAAQ) and other aspects of occupational psychological health, i.e., perceived stress, general mental health, and work engagement, in a sample of intensive care medical staff. Study III evaluated the effects of a Behavioral Skills Training (BST) program on dependent measures of occupational psychological health in a sample of intensive care medical staff. Finally, study IV evaluated the implementation and feasibility of a psychological support model rapidly developed and implemented for ICU staff during the first wave of the covid-19 pandemic. Methods. Four studies were included in the thesis. Study I used a cross-sectional design to evaluate reliability and validity of a measure of psychological flexibility, WAAQ, in a sample of healthcare professionals. In a subsample of participants, a longitudinal design was used to evaluate test-retest reliability. Measures used in the study were three self-report questionnaires, WAAQ, PSS-10 (Perceived Stress Scale-10), and UWES (Utrecht Work Engagement Scale) and the sample consisted of 184 healthcare professionals. Study II evaluated the relationship between psychological flexibility (WAAQ), work engagement (UWES), perceived stress (PSS-10), and general mental health (GHQ-12) in a crosssectional design in a sample of intensive care medical staff. A longitudinal design was used in a subsample (n=46) to further evaluate the relationship between WAAQ and UWES. Study III evaluated the effects of the BST program in a pre-post uncontrolled trial with three assessment points (pre, mid, and post). Study IV used a cross-sectional and qualitative design to evaluate implementation of the support model. Results. In study I, WAAQ showed good internal consistency and good test-retest reliability. Furthermore, it showed a significant negative relationship with perceived stress and significant positive relationship with work engagement. In study II, a hierarchical regression analysis showed WAAQ to explain variance in UWES when controlling for PSS-10 and GHQ-12. Additionally, WAAQ had a significant indirect effect on the relationship between perceived stress (PSS-10) and work engagement (UWES), and the relationship between general mental health (GHQ-12) and work engagement (UWES). In Study III, dependent t-test and linear mixed model analysis of occupational psychological health showed decrease in perceived stress (PSS-10) and improved general mental health (GHQ-12). It showed no change on measures of psychological flexibility (WAAQ) or work engagement (UWES) Study IV showed that although all support efforts were used, daily group sessions followed by peer support had the highest attendance ratings in relation to awareness. Furthermore, interviews with psychologists delivering support showed three themes labelled utility, challenges, and keys to implementation. Conclusions. Results from study I support the use of the Swedish version of WAAQ as a measure of psychological flexibility among healthcare professionals, and considering the sample composition, especially among highly educated female samples. Study II showed support for the utility of psychological flexibility and work engagement to assess and characterize occupational psychological health among intensive care medical staff. Although tentative, findings of study III, support the use of the BST program to promote occupational psychological health among intensive care medical staff. Lastly, the process evaluation of the support model delivered during the pandemic, suggested the importance of a rapid implementation of support when needed, and that success is dependent on the managers to facilitate and implement the interventions, as well as access to competent resources

The colours of the Sun

We compile a sample of Sun-like stars with accurate effective temperatures, metallicities and colours (from the UV to the near-IR). A crucial improvement is that the effective temperature scale of the stars has recently been established as both accurate and precise through direct measurement of angular diameters obtained with stellar interferometers. We fit the colours as a function of effective temperature and metallicity, and derive colour estimates for the Sun in the Johnson/Cousins, Tycho, Stromgren, 2MASS and SDSS photometric systems. For (B-V)_Sun, we favour the ``red'' colour 0.64 versus the ``blue'' colour 0.62 of other recent papers, but both values are consistent within the errors; we ascribe the difference to the selection of Sun-like stars versus interpolation of wider colour-Teff-metallicity relations.Comment: 5 pages, 2 figures, accepted by MNRA

Higher Education Leadership: Cruise or Expedition?

Higher education can create space for learning where students can work with integrated real-world issues, thereby creating value for others while building transformative leadership capabilities. It requires organisational leaders understand how to distinguish between two logics for leadership: the cruise and expedition logic, respectively. Good leadership understands the value of expeditions for the development of the entire system

QED Corrections to Atomic Wavefunctions in Highly Charged Ions

Bound electron states in highly charged ions are strongly influenced by the effects of relativity and quantum electrodynamics (QED). These effects induce shifts of the binding energies as well as corrections to observables related to atomic processes. In this work a numerical procedure is described and implemented in which the QED effects are treated as corrections to relativistic bound-state wavefunctions. This approach, which is based on the recently developed covariant evolution-operator formalism, allows for a merging of QED with the standard methods of many-body perturbation theory. In particular, it enables an evaluation of the combined effect of QED and electron correlation in few-electron systems. Numerical results for this effect are presented for the ground state energy of heliumlike ions. A detailed analysis of the contribution from the electron self-energy is carried out in both the Feynman and Coulomb gauge. It is found that the Feynman gauge suffers from large numerical cancellations and aquires significant contributions from terms involving multiple interactions with the nuclear potential (the so-called many-potential terms), while the Coulomb gauge is well suited for an approximate treatment based on terms involving only freely propagating electrons (the zero-potential terms). With the help of QED-corrected wavefunctions it is also possible to compute corrections to observables in basic atomic processes. In this work some of the one-loop QED corrections (those derivable from perturbed wavefunctions and energies) to the differential cross section and distribution of polarization in radiative recombination of initially bare uranium nuclei are evaluated, as well as the corresponding corrections to the ratio of the electric dipole and magnetic quadrupole transition amplitudes in the 2p3/2 → 1s radiative decay of hydrogenlike uranium. The results from these calculations are all of the expected magnitude, namely on the order of the fine-structure contant