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Dynamical structure factor from weak measurements
Get PDFMuch of our knowledge of quantum systems is encapsulated in the expectation value of Hermitian operators, experimentally obtained by averaging projective measurements. However, dynamical properties are often described by products of operators evaluated at different times; such observables cannot be measured by individual projective measurements, which occur at a single time. For example, the dynamical structure factor (DSF) describes the propagation of density excitations, such as phonons, and is derived from the spatial density operator evaluated at different times. In equilibrium systems this can be obtained by first exciting the system at a specific wavevector and frequency, then measuring the response. Here, we describe an alternative approach using a pair of time-separated weak measurements, and analytically show that their cross-correlation function directly recovers the DSF, for all systems, even far from equilibrium. This general schema can be applied to obtain the cross-correlation function of any pair of weakly observable quantities. We provide numerical confirmation of this technique with a matrix product states simulation of the one-dimensional Bose–Hubbard model, weakly measured by phase contrast imaging. We explore the limits of the method and demonstrate its applicability to real experiments with limited imaging resolution
Viro3D: a comprehensive database of virus protein structure predictions
Get PDFViruses are genetic parasites of cellular life. Tolerance to genetic change, high mutation rates, adaptations to hosts, and immune escape have driven extensive sequence divergence of viral genes, hampering phylogenetic inference and functional annotation. Protein structure, however, is more conserved, allowing searches for distant homologs and revealing otherwise obscured evolutionary histories. Viruses are underrepresented in current protein structure databases, but this can be addressed by recent advances in machine learning. Using AlphaFold2-ColabFold and ESMFold, we predicted structures for >85,000 proteins from >4400 viruses, expanding viral coverage 30 times compared to experimental structures. Using this data, we map form and function across the human and animal virosphere and examine the evolutionary history of viral class-I fusion glycoproteins, revealing the potential origins of coronavirus spike glycoprotein. Our database, Viro3D (https://viro3d.cvr.gla.ac.uk/), will allow the virology community to fully benefit from the structure prediction revolution, facilitating fundamental molecular virology and structure-informed design of therapies and vaccines
A piecewise linear homeomorphim of the circle which is periodic under renormalization
No full textWe demonstrate the existence of a piecewise linear homeomorphism f of R/Z which maps rationals to rationals, whose slopes are powers
2
3
, and whose rotation number is √
2 − 1. This is achieved by showing that a
renormalization procedure becomes periodic when applied to f. Our construction gives a negative answer to a question of D. Calegari [3]. In fact the class
of functions which provide counterexamples to Calegari’s question was already
studied in Herman’s seminal paper on piecewise smooth homeomorphisms of
the circle [7], although for a different purpose. When combined with [8], our
result also shows that F 2
3
does not embed into F, where F 2
3
is the subgroup of
the Stein-Thompson group F2,3 consisting of those elements whose slopes are
powers of 2
3
. Finally, we produce some evidence suggesting a positive answer
to a variation of Calegari’s question and record a number of computational
observations
Review of the Commonwealth Laws on Digital Open Source Evidence in Criminal Proceedings: Country Survey Analysis and Next Steps
No full textNo abstract available
pXRF, Raman, MSI and Microphotogtraphy: developing portable multi-technique analysis of a polychrome Roman altar to Minerva from Mainz
No full textTalk About Tsetse: enabling public engagement through an arts-science collaboration
No full text‘Talk about Tsetse’ was a collaboration between scientific researchers (the University of Glasgow, Kamuzu University of Health Sciences), theatre professionals (Surge, VOICES-Malawi), and Malawian hospital staff. It was a public engagement initiative combining parasitology and outdoor message-based street theatre to raise awareness of human African trypanosomiasis, also known as sleeping sickness, and foster dialogue between scientists and affected communities. Sleeping sickness is a neglected tropical disease caused by single-cell trypanosome parasites and transmitted mainly in rural areas via the bite of a tsetse fly to humans (Kuepfer et al., 2011). It is prevalent in sub-Saharan African countries including Malawi and the Democratic Republic of the Congo. Globally, trypanosomiasis affects approximately 1000 people per year. Surveillance of at-risk communities, diagnosis and treatment are all essential for detection and survival, as this disease is fatal if not treated
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