3,649 research outputs found
Dichotomous Hamiltonians with Unbounded Entries and Solutions of Riccati Equations
An operator Riccati equation from systems theory is considered in the case
that all entries of the associated Hamiltonian are unbounded. Using a certain
dichotomy property of the Hamiltonian and its symmetry with respect to two
different indefinite inner products, we prove the existence of nonnegative and
nonpositive solutions of the Riccati equation. Moreover, conditions for the
boundedness and uniqueness of these solutions are established.Comment: 31 pages, 3 figures; proof of uniqueness of solutions added; to
appear in Journal of Evolution Equation
Generation of Porous Particle Structures using the Void Expansion Method
The newly developed "void expansion method" allows for an efficient
generation of porous packings of spherical particles over a wide range of
volume fractions using the discrete element method. Particles are randomly
placed under addition of much smaller "void-particles". Then, the void-particle
radius is increased repeatedly, thereby rearranging the structural particles
until formation of a dense particle packing.
The structural particles' mean coordination number was used to characterize
the evolving microstructures. At some void radius, a transition from an
initially low to a higher mean coordination number is found, which was used to
characterize the influence of the various simulation parameters. For structural
and void-particle stiffnesses of the same order of magnitude, the transition is
found at constant total volume fraction slightly below the random close packing
limit. For decreasing void-particle stiffness the transition is shifted towards
a smaller void-particle radius and becomes smoother.Comment: 9 pages, 8 figure
Calculation of the spectrum of 12Li by using the multistep shell model method in the complex energy plane
The unbound nucleus Li is evaluated by using the multistep shell model
in the complex energy plane assuming that the spectrum is determined by the
motion of three neutrons outside the Li core. It is found that the ground
state of this system consists of an antibound state and that only this
and a and a excited states are physically meaningful
resonances.Comment: 9 pages, 5 tables, 7 figures, printer-friendly versio
The bumpy road of purinergic inhibitors to clinical application in immune-mediated diseases
Purinergic signaling plays important roles throughout the body in the regulation of organ functions during and following the disruption of homeostasis. This is also reflected by the widespread expression of two families of purinergic receptors (P1 and P2) with numerous subtypes. In the last few decades, there has been increasing evidence that purinergic signaling plays an important role in the regulation of immune functions. Mainly, signals mediated by P2 receptors have been shown to contribute to immune system-mediated pathologies. Thus, interference with P2 receptors may be a promising strategy for the modulation of immune responses. Although only a few clinical studies have been conducted in isolated entities with limited success, preclinical work suggests that the use of P2 receptor inhibitors may bear some promise in various autoimmune diseases. Despite the association of P2 receptors with several disorders from this field, the use of P2 receptor antagonists in clinical therapy is still very scarce. In this narrative review, we briefly review the involvement of the purinergic system in immunological responses and clinical studies on the effect of purinergic inhibition on autoimmune processes. We then open the aperture a bit and show some preclinical studies demonstrating a potential effect of purinergic blockade on autoimmune events. Using suramin, a non-specific purinergic inhibitor, as an example, we further show that off-target effects could be responsible for observed effects in immunological settings, which may have interesting implications. Overall, we believe that it is worthwhile to further investigate this hitherto underexplored area
The good character at work: an initial study on the contribution of character strengths in identifying healthy and unhealthy work-related behavior and experience patterns
Purpose: Positive psychological functioning has been related to various positive work-related outcome variables, such as job satisfaction or work engagement. The aim of the present study was to examine the relations between morally positively valued traits (i.e., strengths of character) and work-related behaviors. Method: A sample of 887 adult women completed the Values in Action Inventory of Strengths (VIA-IS) and the Work-related Behavior and Experience Patterns Questionnaire (AVEM) in an online survey. Results: Those assigned to healthy work-related behavior and experience patterns differed in their strengths profiles from those that demonstrated unhealthy patterns (i.e., burnout type) in a predictable way. Especially the strengths of zest, persistence, hope, and curiosity seemed to play a key role in healthy and ambitious work behavior. Conclusions: The study underlines the relevance of character strengths in work settings and suggests that interventions based on character strengths could substantiate interventions already existing at the workplace in order to enhance positive work outcomes further (e.g., work satisfaction, engagement
PD-1<sup>+</sup> Tcf1<sup>+</sup> CD8<sup>+</sup> T cells from established chronic infection can form memory while retaining a stableimprint of persistent antigen exposure.
Virus-specific PD1 <sup>+</sup> Tcf1 <sup>+</sup> memory-like CD8 <sup>+</sup> T cells (T <sub>ML</sub> s) maintain the CD8 <sup>+</sup> T cell response during chronic viral infection. However, the fate of these cells following cessation of persistent antigen exposure has been unclear. Here, we find that T <sub>ML</sub> s persist upon transfer into antigen-free hosts and form memory following recall stimulation. Phenotypic, functional, and transcriptome analyses show that T <sub>ML</sub> -derived memory cells resemble those arising in response to acute, resolved infection, but they retain features of chronically stimulated cells, including elevated PD-1 and Tox and reduced cytokine expression. This chronic infection imprint is largely accounted for by constitutive Tox expression. Virus-specific Tcf1 <sup>+</sup> CD8 <sup>+</sup> T cells that persist after clearance of systemic infection also display a chronic infection imprint. Notwithstanding, renewed virus exposure induces a recall response, which controls virus infection in part. Thus, cessation of chronic antigen exposure yields a memory CD8 <sup>+</sup> T cell compartment that reflects prior stimulation
Pairing in Nuclei
Simple generic aspects of nuclear pairing in homogeneous medium as well as in
finite nuclei are discussed. It is argued that low-energy nuclear structure is
not sensitive enough to resolve fine details of nuclear nucleon-nucleon (NN)
interaction in general and pairing NN interaction in particular what allows for
regularization of the ultraviolet (high-momentum) divergences and a consistent
formulation of effective superfluid local theory. Some aspects of
(dis)entanglement of pairing with various other effects as well as forefront
ideas concerning isoscalar pairing are also briefly discussed.Comment: Invited talk presented at the International Conference on Finite
Fermionic Systems, Nilsson Model 50 Years,Lund, Sweden, June 14-18, 2005, 7
LaTeX pages, 4 encapsulated postscript figure
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