Comment on "Thermal Effects on the Casimir Force in the 0.1-5 micrometer Range"

In a recent paper (M. Bostrom and Bo E. Sernelius, Phys. Rev. Lett. 84, 4757 (2000)) the combined effect of finite conductivity and finite temperature on the Casimir force is analyzed, and significant deviations from other theoretical results and a recent experiment are obtained. In this Comment, I show that the extrapolation to zero frequency is incorrect because the authors have neglected that the wavenumber and frequency of the electromagentic mode must simultaneously appraoch zeroComment: Final version (two previous versions, first was partly incorrect) Rejected by PRL

Redescription of Cervidellus vexilliger (de Man, 1880) Thorne, 1937 (Nematoda : Cephalobidae) and taxonomical consequences

#Cervidellus vexilliger, actuellement espèce type du genre #Ypsylonellus, est redécrit et un néotype est désigné parmi les spécimens d'un échantillon collecté dans la localité type : Haagse Bos, Pays-Bas. Une autre espèce très proche, correspondant à la diagnose de #C. neftasiensis, était également présente dans cet échantillon. La description originale de #C. vexilliger et les nouveaux spécimens provenant de la localité type suggèrent que #C. vexilliger est conspécifique de #C. serratus. #C. serratus est donc synonymisé avec #C. vexilliger et #Ypsilonellus est synonymisé avec #Cervidellus. Des diagnoses différentielles et une classification provisoire sont proposées pour les genres #Cervidellus et #Stegelletina. (Résumé d'auteur

Casimir attractive-repulsive transition in MEMS

Unwanted stiction in micro- and nanomechanical (NEMS/MEMS) systems due to dispersion (van der Waals, or Casimir) forces is a significant hurdle in the fabrication of systems with moving parts on these length scales. Introducing a suitably dielectric liquid in the interspace between bodies has previously been demonstrated to render dispersion forces repulsive, or even to switch sign as a function of separation. Making use of recently available permittivity data calculated by us we show that such a remarkable non-monotonic Casimir force, changing from attractive to repulsive as separation increases, can in fact be observed in systems where constituent materials are in standard NEMS/MEMS use requiring no special or exotic materials. No such nonmonotonic behaviour has been measured to date. We calculate the force between a silica sphere and a flat surface of either zinc oxide or hafnia, two materials which are among the most prominent for practical microelectrical and microoptical devices. Our results explicate the need for highly accurate permittivity functions of the materials involved for frequencies from optical to far-infrared frequencies. A careful analysis of the Casimir interaction is presented, and we show how the change in the sign of the interaction can be understood as a result of multiple crossings of the dielectric functions of the three media involved in a given set-up.Comment: 6 pages, 4 figure

Compositional nanodomain formation in hybrid formate perovskites

We report the synthesis and structural characterisation of three mixed-metal formate perovskite families [C(NH$_2$)$_3$]M$_{1-x}$Cu$_x$(HCOO)$_3$ (M = Mn, Zn, Mg). Using a combination of infrared spectroscopy, non-negative matrix factorization, and reverse Monte Carlo refinement, we show that the Mn- and Zn-containing compounds support compositional nanodomains resembling the polar nanoregions of conventional relaxor ferroelectrics. The M = Mg family exhibits a miscibility gap that we suggest reflects the limiting behaviour of nanodomain formation.Comment: 4 pages, 3 figure

Non-Perturbative Theory of Dispersion Interactions

Some open questions exist with fluctuation-induced forces between extended dipoles. Conventional intuition derives from large-separation perturbative approximations to dispersion force theory. Here we present a full non-perturbative theory. In addition we discuss how one can take into account finite dipole size corrections. It is of fundamental value to investigate the limits of validity of the perturbative dispersion force theory.Comment: 9 pages, no figure

Individual and organisational factors in the psychosocial work environment are associated with home care staffs’ job strain: A Swedish cross-sectional study

Background Home care staff (HCS) provide essential service to enable older adults to age in place. However, unreasonable demands in the work environment to deliver a safe, effective service with high quality has a negative impact on the individual employee’s well-being and the care provided to the older adults. The psychosocial work environment is associated with employees´ well-being, although, knowledge regarding which individual and organisational factors that contribute to job strain for HCS is limited. These factors need to be identified to develop targeted interventions and create sustainable work situations for HCS. This study aimed to explore how HCS´s perceived job strain is associated with, and to what extent can be explained by, individual and organisational factors of the psychosocial work environment and psychosomatic health. Method An explorative cross-sectional questionnaire survey design was used in a large Swedish county. Five home care agencies with a total of 481 HCS were asked to respond to a questionnaire regarding their perceived level of job strain (Strain in Dementia Care Scale), psychosocial work environment (QPSNordic34+), and psychosomatic health (Satisfaction with Work Questionnaire). Multiple linear regression (MLR) analyses were conducted to explore the association between job strain and individual and organisational factors. Results In total, 226 (46%) HCS responded to the questionnaire. Both individual and organisational factors were significant predictors of job strain and explained a variance ranging between 39 to 51% (p = 0.001). The organisational factor job demand and the individual factor feeling worried and restless was most frequently represented in these MRL models. A higher job strain was also associated with adverse outcomes regarding leadership, organisational culture and climate, and control at work. Conclusion This study indicates that there is an intertwined complexity of individual and organisational factors that are associated with the HCS´s perception of job strain. Implementation of new multidimensional work strategies, such as a reablement approach, could support the development of efficient strategies for HCS and reduce the level of job strain. Policy changes for the provision of home care are also needed to support the development of a sustainable and healthy psychosocial work environment

The Spin Holonomy Group In General Relativity

It has recently been shown by Goldberg et al that the holonomy group of the chiral spin-connection is preserved under time evolution in vacuum general relativity. Here, the underlying reason for the time-independence of the holonomy group is traced to the self-duality of the curvature 2-form for an Einstein space. This observation reveals that the holonomy group is time-independent not only in vacuum, but also in the presence of a cosmological constant. It also shows that once matter is coupled to gravity, the "conservation of holonomy" is lost. When the fundamental group of space is non-trivial, the holonomy group need not be connected. For each homotopy class of loops, the holonomies comprise a coset of the full holonomy group modulo its connected component. These cosets are also time-independent. All possible holonomy groups that can arise are classified, and examples are given of connections with these holonomy groups. The classification of local and global solutions with given holonomy groups is discussed.Comment: 21 page