Generating Macroscopic Superpositions with Interacting Bose-Einstein Condensates: Multi-Mode Speed-Ups and Speed Limits

We theoretically investigate the effect of multi-mode dynamics on the creation of macroscopic superposition states (spin-cat states) in Bose-Einstein condensates via one-axis twisting. A two-component Bose-Einstein condensate naturally realises an effective one-axis twisting interaction, under which an initially separable state will evolve toward a spin-cat state. However, the large evolution times necessary to realise these states is beyond the scope of current experiments. This evolution time is proportional to the degree of asymmetry in the relative scattering lengths of the system, which results in the following trade-off; faster evolution times are associated with an increase in multi-mode dynamics, and we find that generally multi-mode dynamics reduce the degree of entanglement present in the final state. However, we find that highly entangled cat-like states are still possible in the presence of significant multi-mode dynamics, and that these dynamics impose a speed-limit on the evolution such states

Is acetylation a metabolic rheostat that regulates skeletal muscle insulin action?

Skeletal muscle insulin resistance, which increases the risk for developing various metabolic diseases, including type 2 diabetes, is a common metabolic disorder in obesity and aging. If potential treatments are to be developed to treat insulin resistance, then it is important to fully understand insulin signaling and glucose metabolism. While recent large-scale "omics" studies have revealed the acetylome to be comparable in size to the phosphorylome, the acetylation of insulin signaling proteins and its functional relevance to insulin-stimulated glucose transport and glucose metabolism is not fully understood. In this Mini Review we discuss the acetylation status of proteins involved in the insulin signaling pathway and review their potential effect on, and relevance to, insulin action in skeletal muscle

Gradient-based quantitative image reconstruction in ultrasound-modulated optical tomography: first harmonic measurement type in a linearised diffusion formulation

Ultrasound-modulated optical tomography is an emerging biomedical imaging modality which uses the spatially localised acoustically-driven modulation of coherent light as a probe of the structure and optical properties of biological tissues. In this work we begin by providing an overview of forward modelling methods, before deriving a linearised diffusion-style model which calculates the first-harmonic modulated flux measured on the boundary of a given domain. We derive and examine the correlation measurement density functions of the model which describe the sensitivity of the modality to perturbations in the optical parameters of interest. Finally, we employ said functions in the development of an adjoint-assisted gradient based image reconstruction method, which ameliorates the computational burden and memory requirements of a traditional Newton-based optimisation approach. We validate our work by performing reconstructions of optical absorption and scattering in two- and three-dimensions using simulated measurements with 1% proportional Gaussian noise, and demonstrate the successful recovery of the parameters to within +/-5% of their true values when the resolution of the ultrasound raster probing the domain is sufficient to delineate perturbing inclusions.Comment: 12 pages, 6 figure

Empirical adequacy and scientific discovery

O presente trabalho busca mostrar que o empirismo construtivo de Bas van Fraassen, segundo enunciado em sua obra The Scientific Image, conduz a dificuldades consideráveis em filosofia da ciência. A principal dificuldade seria a exclusão da matemática dessa concepção, por sua clara ausência de adequação empírica, sendo essa a mais importante exigência da formulação de van Fraassen. Nesse sentido, é proposto uma formulação mais ampla de teoria científica, oriunda a noção de estrutura simples de Da Costa (1999), considerando a noção de descoberta científica num sentido estrito, o limite de validade da teoria e o formalismo utilizado, num contexto temporal. _______________________________________________________________________________________ ABSTRACTThis paper aims to show that Bas van Fraassen’s constructive empiricism, such as it is expounded in The Scientific Image, ends up in considerable difficulties in the philosophy of science. The main problem would be the exclusion of mathematics from the conception of science, given its clear absence of empirical adequacy, which is the most important requirement of his formulation. In this sense, it is suggested a more inclusive formulation of scientific theory, aroused from the notion of Da Costa’s (1999) simple structure, considering the notion of scientific discovery in a strict sense, and the validity limit of a theory and the formalism used in a temporal context