Emergent spacetime from a momentum gauge and electromagnetism

Motivated by the fermionic Berry's phase in momentum space, we study a local Abelian phase in momentum space, also known as the momentum gauge, coupled to electromagnetism, for complex scalars in the phase-space worldline formalism. The interaction of both Abelian fields is shown to give rise to a momentum gauge dependant emergent spacetime. As a concrete example, we further study classical solutions of the momentum gauge field which lead to an emergent Newtonian gravity with gravitational potential predicted by coupled Coulomb fields both in configuration and momentum spaces. Noncommutative aspects of the theory are also provided.Comment: 6 pages, 1 figur

Curvature induced pseudo-gauge fields from time-dependent geometries in graphene

The massless Dirac equation is studied in curved spacetime on the (2+1)-dimensional graphene sheet in time-dependent geometries. Emergent pseudo-gauge fields are found both in the adiabatic regime and, for high-frequency periodic geometries, in the non-adiabatic regime for a generic FLRW metric in Fermi normal coordinates. The former extends the conventionally understood homogeneous pseudo-gauge field to include weak temporal inhomogeneities. The latter, through the usage of Floquet theory, represent a new class of emergent pseudo-gauge field, and is argued to potentially provide a condensed matter realization of cosmological high-frequency geometries.Comment: 12 pages, 1 figur

Assessing the performance of ultrafast vector flow imaging in the neonatal heart via multiphysics modeling and In vitro experiments

Ultrafast vector flow imaging would benefit newborn patients with congenital heart disorders, but still requires thorough validation before translation to clinical practice. This paper investigates 2-D speckle tracking (ST) of intraventricular blood flow in neonates when transmitting diverging waves at ultrafast frame rate. Computational and in vitro studies enabled us to quantify the performance and identify artifacts related to the flow and the imaging sequence. First, synthetic ultrasound images of a neonate's left ventricular flow pattern were obtained with the ultrasound simulator Field II by propagating point scatterers according to 3-D intraventricular flow fields obtained with computational fluid dynamics (CFD). Noncompounded diverging waves (opening angle of 60 degrees) were transmitted at a pulse repetition frequency of 9 kHz. ST of the B-mode data provided 2-D flow estimates at 180 Hz, which were compared with the CFD flow field. We demonstrated that the diastolic inflow jet showed a strong bias in the lateral velocity estimates at the edges of the jet, as confirmed by additional in vitro tests on a jet flow phantom. Furthermore, ST performance was highly dependent on the cardiac phase with low flows (< 5 cm/s), high spatial flow gradients, and out-of-plane flow as deteriorating factors. Despite the observed artifacts, a good overall performance of 2-D ST was obtained with a median magnitude underestimation and angular deviation of, respectively, 28% and 13.5 degrees during systole and 16% and 10.5 degrees during diastole

Designing Interactive and Immersive Multimodal Installations for People with Disability

We developed an end-to-end co-creative methodology for designing interactive and immersive multisensory virtual reality experiences with a particular focus on people with disability. Our method draws on what is called “design thinking” to provide a backbone to our approach. This embraces three stages, an empathic first stage, followed by an ideation phase, during which the thematic context is elaborated, and then an iterative exploration phase during which the initial concept is refined and the implementation is achieved. Furthermore, the “cognitive design” methodology developed by one of us led us to an approach incorporating all sensory modalities, not just the audio and visual modalities (that is, it includes odor, tactile, taste and proprioceptive stimuli), in order to deliver an experience that fully enhances the user’s sense of embodiment, and also led us to place the user’s experience at the heart of the installation. Users participate in the design process through co-design protocols. We showcase the application of this methodology in a detailed way for the construction of an interactive and immersive VR installation for people with disabilities

Understanding risk in daily life of diverse persons with physical and sensory impairments

Managing risk of injury in daily life is a task common to all humans. However, people with impairments face significantly greater challenges in both assessing and managing risk of injury. To find out more about how individuals with impairments understand risk, we developed a qualitative study design based on semi-structured interviews. Seven people with a broad range of impairments were recruited for the study. The interviews were analyzed and organized into a codification tree subdivided into four main sections: safety and risk management, risk situation portrayal, perceptions of safety measures and finally loss of control and strong sensations. The study revealed that the difficulties related to managing risk in day-to-day situations are much higher than for people without impairments and, indeed, are possibly under reported in the literature. The realization that risk is ever present in the daily lives of people with impairments has led us to reconsider how we move forward on the remainder of our study.Peer Reviewe

Gypsum-DL: an open-source program for preparing small-molecule libraries for structure-based virtual screening

Computational techniques such as structure-based virtual screening require carefully prepared 3D models of potential small-molecule ligands. Though powerful, existing commercial programs for virtual-library preparation have restrictive and/or expensive licenses. Freely available alternatives, though often effective, do not fully account for all possible ionization, tautomeric, and ring-conformational variants. We here present Gypsum-DL, a free, robust open-source program that addresses these challenges. As input, Gypsum-DL accepts virtual compound libraries in SMILES or flat SDF formats. For each molecule in the virtual library, it enumerates appropriate ionization, tautomeric, chiral, cis/trans isomeric, and ring-conformational forms. As output, Gypsum-DL produces an SDF file containing each molecular form, with 3D coordinates assigned. To demonstrate its utility, we processed 1558 molecules taken from the NCI Diversity Set VI and 56,608 molecules taken from a Distributed Drug Discovery (D3) combinatorial virtual library. We also used 4463 high-quality protein-ligand complexes from the PDBBind database to show that Gypsum-DL processing can improve virtual-screening pose prediction. Gypsum-DL is available free of charge under the terms of the Apache License, Version 2.0

EIF4E/4E-BP dissociation and 4E-BP degradation in the first mitotic division of the sea urchin embryo

AbstractThe mRNA’s cap-binding protein eukaryotic translation initiation factor (eIF)4E is a major target for the regulation of translation initiation. eIF4E activity is controlled by a family of translation inhibitors, the eIF4E-binding proteins (4E-BPs). We have previously shown that a rapid dissociation of 4E-BP from eIF4E is related with the dramatic rise in protein synthesis that occurs following sea urchin fertilization. Here, we demonstrate that 4E-BP is destroyed shortly following fertilization and that 4E-BP degradation is sensitive to rapamycin, suggesting that proteolysis could be a novel means of regulating 4E-BP function. We also show that eIF4E/4E-BP dissociation following fertilization is sensitive to rapamycin. Furthermore, while rapamycin modestly affects global translation rates, the drug strongly inhibits cyclin B de novo synthesis and, consequently, precludes the completion of the first mitotic cleavage. These results demonstrate that, following sea urchin fertilization, cyclin B translation, and thus the onset of mitosis, are regulated by a rapamycin-sensitive pathway. These processes are effected at least in part through eIF4E/4E-BP complex dissociation and 4E-BP degradation

Sanar la memoria, amanecer la palabra. Reflexiones sobre los procesos de memoria histórica desde las comunidades étnicas

Este artículo propone una reflexión alrededor de las diversas estrategias que en los últimos años han venido construyendo los pueblos indígenas, y en general las comunidades étnicas, para asumir el reto de adelantar procesos de memoria histórica gestionados localmente. El abordaje de un pasado doloroso asociado a los impactos del conflicto armado en los territorios ancestrales es discutido desde los debates que las organizaciones y pueblos indígenas han posicionado en torno a las nociones de daño y sanación de las memorias asociadas al dolor y en términos de una propuesta que posicione el reconocimiento de su agencia social en clave de su pervivencia como pueblos indígenas. Construido desde los aprendizajes derivados del trabajo del equipo de enfoque diferencial étnico del Centro Nacional de Memoria Histórica, el texto plantea la relevancia de estos aportes para el debate más amplio sobre la reparación en Colombia, la dignificación de las víctimas del conflicto y las condiciones que permitan la no repetición de los hechos asociados al conflicto armado en el país