1,270 research outputs found
What is the reference frame of an accelerated observer?
The general construction of extended refrence frames for noninertial
observers in flat space is studied. It is shown that, if the observer moves
inertially before and after an arbitrary acceleration and rotation, the region
where reference frames can coincide with an inertial system is bounded for
final velocities exceeding 0.6 c.Comment: 5 pages, 2 figures, published in Phys. Lett. A 215, 1 (1996
A Machine Learning Based Regulatory Risk Index for Cryptocurrencies
Cryptocurrencies' values often respond aggressively to major policy changes,
but none of the existing indices informs on the market risks associated with
regulatory changes. In this paper, we quantify the risks originating from new
regulations on FinTech and cryptocurrencies (CCs), and analyse their impact on
market dynamics. Specifically, a Cryptocurrency Regulatory Risk IndeX (CRRIX)
is constructed based on policy-related news coverage frequency. The unlabeled
news data are collected from the top online CC news platforms and further
classified using a Latent Dirichlet Allocation model and Hellinger distance.
Our results show that the machine-learning-based CRRIX successfully captures
major policy-changing moments. The movements for both the VCRIX, a market
volatility index, and the CRRIX are synchronous, meaning that the CRRIX could
be helpful for all participants in the cryptocurrency market. The algorithms
and Python code are available for research purposes on www.quantlet.de
Fermi Coordinates for Weak Gravitational Fields
A Reference is corrected. (We derive the Fermi coordinate system of an
observer in arbitrary motion in an arbitrary weak gravitational field valid to
all orders in the geodesic distance from the worldline of the observer. In flat
space-time this leads to a generalization of Rindler space for arbitrary
acceleration and rotation. The general approach is applied to the special case
of an observer resting with respect to the weak gravitational field of a static
mass distribution. This allows to make the correspondence between general
relativity and Newtonian gravity more precise.)Comment: 7 Pages, Preprint KONS-RGKU-94-04, LaTe
Structures of monomeric and oligomeric forms of the Toxoplasma gondiiperforin-like protein 1
Toxoplasma and Plasmodium are the parasitic agents of toxoplasmosis and malaria, respectively, and use perforin-like proteins (PLPs) to invade host organisms and complete their life cycles. The Toxoplasma gondii PLP1 (TgPLP1) is required for efficient exit from parasitophorous vacuoles in which proliferation occurs. We report structures of the membrane attack complex/perforin (MACPF) and Apicomplexan PLP C-terminal β-pleated sheet (APCβ) domains of TgPLP1. The MACPF domain forms hexameric assemblies, with ring and helix geometries, and the APCβ domain has a novel β-prism fold joined to the MACPF domain by a short linker. Molecular dynamics simulations suggest that the helical MACPF oligomer preserves a biologically important interface, whereas the APCβ domain binds preferentially through a hydrophobic loop to membrane phosphatidylethanolamine, enhanced by the additional presence of inositol phosphate lipids. This mode of membrane binding is supported by site-directed mutagenesis data from a liposome-based assay. Together, these structural and biophysical findings provide insights into the molecular mechanism of membrane targeting by TgPLP1
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