582 research outputs found
Series expansions in closed and open quantum many-body systems with multiple quasiparticle types
The established approach of perturbative continuous unitary transformations
(pCUTs) constructs effective quantum many-body Hamiltonians as perturbative
series that conserve the number of one quasiparticle type. We extend the pCUT
method to similarity transformations - dubbed -
allowing for multiple quasiparticle types with complex-valued energies. This
enlarges the field of application to closed and open quantum many-body systems
with unperturbed operators corresponding to arbitrary superimposed ladder
spectra. To this end, a generalized counting operator is combined with the
quasiparticle generator for open quantum systems recently introduced by
Schmiedinghoff and Uhrig (arXiv:2203.15532). The
then yields model-independent block-diagonal effective Hamiltonians and
Lindbladians allowing a linked-cluster expansion in the thermodynamic limit
similar to the conventional pCUT method. We illustrate the application of the
method by discussing representative closed, open,
and non-Hermitian quantum systems
Dynamic structure factor of the antiferromagnetic Kitaev model in large magnetic fields
We investigate the dynamic structure factor of the antiferromagnetic Kitaev
honeycomb model in a magnetic field by applying perturbative continuous unitary
transformations about the high-field limit. One- and two-quasi-particle
properties of the dressed elementary spin flip excitations of the high-field
polarized phase are calculated which account for most of the spectral weight in
the dynamic structure factor. We discuss the evolution of spectral features in
these quasi-particle sectors in terms of one-quasi-particle dispersions,
two-quasi-particle continua, the formation of anti-bound states, and
quasi-particle decay. In particular, a comparably strong spectral feature above
the upper edge of the upmost two-quasi-particle continuum represents three
anti-bound states which form due to nearest-neighbor density-density
interactions.Comment: 14 pages, 10 figure
Bridges over troubled waters: an interdisciplinary framework for evaluating the interconnectedness within fragmented domestic flood risk management systems
Diversification of strategies in Flood Risk Management (FRM) is widely regarded as a necessary step forward in terms of lessening the likelihood and magnitude of flooding, as well as minimizing the exposure of people and property, and in turn the disruption, economic damage, health impacts and other adverse consequences that ensue when floods occur. Thus, diversification is often heralded as an essential condition for enhancing societal resilience to flooding. However, an inevitable consequence of diversifying strategies and practices in FRM is that it can lead to fragmentation within FRM systems, in terms of the distribution of responsibilities between actors and governing rules enacted within different policy domains. This can prove detrimental to the effectiveness of FRM.
Building upon the notion of fragmentation developed in legal and governance literature, this paper introduces the concept of âbridging mechanismsâ, i.e. instruments that remedy fragmentation by enhancing interconnectedness between relevant actors through information transfer, coordination and cooperation. This paper develops a typology of both fragmentation and bridging mechanisms and analyzes their relations, partly drawing upon empirical research conducted within the EU âSTAR-FLOODâ project. In turn, this paper outlines a novel interdisciplinary methodological framework for evaluating the degree and quality of the interconnectedness within fragmented domestic FRM systems. A pragmatic, flexible and broadly applicable tool, this framework is both suited for academic purposes, as well as for practically oriented analysis and (re)development of fragmented FRM systems, and potentially other fragmented systems, within the EU and abroad
HSP90-CDC37-PP5 forms a structural platform for kinase dephosphorylation.
Activation of client protein kinases by the HSP90 molecular chaperone system is affected by phosphorylation at multiple sites on HSP90, the kinase-specific co-chaperone CDC37, and the kinase client itself. Removal of regulatory phosphorylation from client kinases and their release from the HSP90-CDC37 system depends on the Ser/Thr phosphatase PP5, which associates with HSP90 via its N-terminal TPR domain. Here, we present the cryoEM structure of the oncogenic protein kinase client BRAFV600E bound to HSP90-CDC37, showing how the V600E mutation favours BRAF association with HSP90-CDC37. Structures of HSP90-CDC37-BRAFV600E complexes with PP5 in autoinhibited and activated conformations, together with proteomic analysis of its phosphatase activity on BRAFV600E and CRAF, reveal how PP5 is activated by recruitment to HSP90 complexes. PP5 comprehensively dephosphorylates client proteins, removing interaction sites for regulatory partners such as 14-3-3 proteins and thus performing a 'factory reset' of the kinase prior to release
GLAMM: Genome-Linked Application for Metabolic Maps
The Genome-Linked Application for Metabolic Maps (GLAMM) is a unified web interface for visualizing metabolic networks, reconstructing metabolic networks from annotated genome data, visualizing experimental data in the context of metabolic networks and investigating the construction of novel, transgenic pathways. This simple, user-friendly interface is tightly integrated with the comparative genomics tools of MicrobesOnline [Dehal et al. (2010) Nucleic Acids Research, 38, D396âD400]. GLAMM is available for free to the scientific community at glamm.lbl.gov
An Outdoor Aging Study to Investigate the Release of Per- And Polyfluoroalkyl Substances (PFAS) from Functional Textiles
The emission of per- and polyfluoroalkyl substances (PFAS) from functional textiles was investigated via an outdoor weathering experiment in Sydney, Australia. Polyamide (PA) textile fabrics treated with different water-repellent, side-chain fluorinated polymers (SFPs) were exposed on a rooftop to multiple natural stressors, including direct sunlight, precipitation, wind, and heat for 6-months. After weathering, additional stress was applied to the fabrics through abrasion and washing. Textile characterization using a multiplatform analytical approach revealed loss of both PFAS-containing textile fragments (e.g., microfibers) as well as formation and loss of low molecular weight PFAS, both of which occurred throughout weathering. These changes were accompanied by a loss of color and water repellency of the textile. The potential formation of perfluoroalkyl acids (PFAAs) from mobile residuals was quantified by oxidative conversion of extracts from unweathered textiles. Each SFP-textile finish emitted a distinct PFAA pattern following weathering, and in some cases the concentrations exceeded regulatory limits for textiles. In addition to transformation of residual low molecular weight PFAA-precursors, release of polymeric PFAS from degradation and loss of textile fibers/particles contributed to overall PFAS emissions during weathering
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