Spatial Substructures Research Articles

Crossed products, extended phase spaces and the resolution of entanglement singularities

We identify a direct correspondence between the crossed product construction which plays a crucial role in the theory of Type III von Neumann algebras, and the extended phase space construction which restores the integrability of non-zero charges generated by gauge symmetries in the presence of spatial substructures. This correspondence provides a blue-print for resolving singularities which are encountered in the computation of entanglement entropy for subregions in quantum field theories. The extended phase space encodes quantities that would be regarded as ‘pure gauge’ from the perspective of the full theory, but are nevertheless necessary for gluing together, in a path integral sense, physics in different subregions. These quantities are required in order to maintain gauge covariance under such gluings. The crossed product provides a consistent method for incorporating these necessary degrees of freedom into the operator algebra associated with a given subregion. In this way, the extended phase space completes the subregion algebra and subsequently allows for the assignment of a meaningful, finite entropy to states therein.

Beam torsion effect of monolithic precast concrete beam-column substructures during progressive collapse

To investigate the effect of spandrel beam torsion on the progressive collapse resistance of the monolithic precast concrete (PC) spatial frames, three PC substructures (a cantilever beam substructure PC-c, a double-span planar substructure PC-p and a spatial substructure PC-s) were designed. They were tested under a middle column removal scenario, to simulate the progressive collapse of the PC frame structures. The test results indicated that the torque developed in spandrel beams of the spatial substructure PC-s leaded to more severe concrete cracking and crushing at its beam ends. The existence of torque in the PC spatial substructure weakened the mobilization of compressive arch action (CAA) and catenary action (CA). The CA capacity of the spatial PC substructure was reduced by 27.23% compared with the planar substructure PC-p, and the CA action was ended in advance. Additionally, a three-dimensional joint model considering the torsion effect was proposed herein, which accurately captured the progressive collapse behavior of spatial substructures. Based on the verified numerical model, the difference between the combined torsion–bending interaction in the spandrel beam of planar and spatial substructures was analyzed. The effects of reinforcement configuration and span-depth ratio of spandrel beams on the collapse resistance were studied. Finally, a conservative calculation method of the increased gravity loads GN was given when the torsion effect needs to be considered.

Progressive-collapse test of slab effects on reinforced concrete spatial frame substructures

Floor systems constructed from slabs and beams are critical structural elements of reinforced concrete (RC) frame structures, allowing them to resist progressive collapse. To elucidate the complex effects of the slab and its thickness on the progressive-collapse resistance of RC spatial frame structures, three 1/3-scale 2 × 2 span substructure specimens, including one three-dimensional (3D) skeletal frame substructure and two 3D frame–slab substructures with different slab thicknesses, were tested in a middle-column-removal scenario. The test results indicated that the frame–slab substructure exhibited two resisting progressive-collapse stages: a primary mechanism stage, with small deformations, and a secondary mechanism stage, with large deformations. The slab contributions were separated from the floor system and quantified by comparing the results for the skeletal frame substructure and frame–slab substructure. Although there were no in-plane confinements, the slab also significantly improved the resistance against progressive collapse, owing to the compressive and tensile membrane action in the primary and secondary mechanism stages, respectively. Increasing the slab thickness increased the compressive membrane action of the slab, which significantly enhanced the progressive-collapse resistance under small deformations. However, under large deformations, the beam and slab did not work synergistically, which limited the development of secondary mechanisms against progressive collapse.

The within-host evolution of antimicrobial resistance in Mycobacterium tuberculosis.

ABSTRACTTuberculosis (TB) has been responsible for the greatest number of human deaths due to an infectious disease in general, and due to antimicrobial resistance (AMR) in particular. The etiological agents of human TB are a closely-related group of human-adapted bacteria that belong to the Mycobacterium tuberculosis complex (MTBC). Understanding how MTBC populations evolve within-host may allow for improved TB treatment and control strategies. In this review, we highlight recent works that have shed light on how AMR evolves in MTBC populations within individual patients. We discuss the role of heteroresistance in AMR evolution, and review the bacterial, patient and environmental factors that likely modulate the magnitude of heteroresistance within-host. We further highlight recent works on the dynamics of MTBC genetic diversity within-host, and discuss how spatial substructures in patients’ lungs, spatiotemporal heterogeneity in antimicrobial concentrations and phenotypic drug tolerance likely modulates the dynamics of MTBC genetic diversity in patients during treatment. We note the general characteristics that are shared between how the MTBC and other bacterial pathogens evolve in humans, and highlight the characteristics unique to the MTBC.

Progressive collapse test of assembled monolithic concrete frame spatial substructures with different anchorage methods in the beam–column joint

In this study, three two-third-scale assembled monolithic concrete spatial frame substructures with three beams and four columns were tested to evaluate progressive collapse resistance. The test parameters are anchorage methods, such as 90° hooked bar, lap splice in U-shaped assembled monolithic concrete beam, and headed bar using welded anchor plate. Force–displacement-controlled pseudo-static loading was applied to the mid-column. On the basis of structural performance, including load-carrying capacity, deformation capacity, crack distribution, rebar strain, and failure mode, the progressive collapse resistance mechanism of the specimens was analyzed. Test results showed that three types of cracks were developed: initial flexural cracks in beam–column joints, diagonal cracks due to compressive arch action, and tension cracks due to catenary action. The specimen using the headed bar exhibited the best progressive collapse performance, whereas the specimen using the lap splice connection showed the worst structural performance. Regardless of anchorage methods, bond failure did not occur during progressive collapse. The progressive collapse performance of the specimen was assessed based on Chinese and American codes.

NGC 2548: clumpy spatial and kinematic structure in an intermediate-age Galactic cluster

NGC 2548 is a 400-500 Myr old open cluster with evidence of spatial substructures likely caused by its interaction with the Galactic disk. In this work we use precise astrometric data from the Carte du Ciel - San Fernando (CdC-SF) catalogue to study the clumpy structure in this cluster. We confirm the fragmented structure of NGC 2548 but, additionally, the relatively high precision of our kinematic data lead us to the first detection of substructures in the proper motion space of a stellar cluster. There are three spatially separated cores each of which has its own counterpart in the proper motion distribution. The two main cores lie nearly parallel to the Galactic plane whereas the third one is significantly fainter than the others and it moves toward the Galactic plane separating from the rest of the cluster. We derive core positions and proper motions, as well as the stars belonging to each core.

Simple Learned Weighted Sums of Inferior Temporal Neuronal Firing Rates Accurately Predict Human Core Object Recognition Performance.

To go beyond qualitative models of the biological substrate of object recognition, we ask: can a single ventral stream neuronal linking hypothesis quantitatively account for core object recognition performance over a broad range of tasks? We measured human performance in 64 object recognition tests using thousands of challenging images that explore shape similarity and identity preserving object variation. We then used multielectrode arrays to measure neuronal population responses to those same images in visual areas V4 and inferior temporal (IT) cortex of monkeys and simulated V1 population responses. We tested leading candidate linking hypotheses and control hypotheses, each postulating how ventral stream neuronal responses underlie object recognition behavior. Specifically, for each hypothesis, we computed the predicted performance on the 64 tests and compared it with the measured pattern of human performance. All tested hypotheses based on low- and mid-level visually evoked activity (pixels, V1, and V4) were very poor predictors of the human behavioral pattern. However, simple learned weighted sums of distributed average IT firing rates exactly predicted the behavioral pattern. More elaborate linking hypotheses relying on IT trial-by-trial correlational structure, finer IT temporal codes, or ones that strictly respect the known spatial substructures of IT ("face patches") did not improve predictive power. Although these results do not reject those more elaborate hypotheses, they suggest a simple, sufficient quantitative model: each object recognition task is learned from the spatially distributed mean firing rates (100 ms) of ∼60,000 IT neurons and is executed as a simple weighted sum of those firing rates. Significance statement: We sought to go beyond qualitative models of visual object recognition and determine whether a single neuronal linking hypothesis can quantitatively account for core object recognition behavior. To achieve this, we designed a database of images for evaluating object recognition performance. We used multielectrode arrays to characterize hundreds of neurons in the visual ventral stream of nonhuman primates and measured the object recognition performance of >100 human observers. Remarkably, we found that simple learned weighted sums of firing rates of neurons in monkey inferior temporal (IT) cortex accurately predicted human performance. Although previous work led us to expect that IT would outperform V4, we were surprised by the quantitative precision with which simple IT-based linking hypotheses accounted for human behavior.

Prediction of DNA-binding proteins from relational features

BackgroundThe process of protein-DNA binding has an essential role in the biological processing of genetic information. We use relational machine learning to predict DNA-binding propensity of proteins from their structures. Automatically discovered structural features are able to capture some characteristic spatial configurations of amino acids in proteins.ResultsPrediction based only on structural relational features already achieves competitive results to existing methods based on physicochemical properties on several protein datasets. Predictive performance is further improved when structural features are combined with physicochemical features. Moreover, the structural features provide some insights not revealed by physicochemical features. Our method is able to detect common spatial substructures. We demonstrate this in experiments with zinc finger proteins.ConclusionsWe introduced a novel approach for DNA-binding propensity prediction using relational machine learning which could potentially be used also for protein function prediction in general.

Are small-scale substructures a universal property of galaxy haloes? The case of the giant elliptical NGC 5128★

We present an analysis of the spatial and chemical substructures in a remote halo field in the nearby giant elliptical galaxy Centaurus A (NGC 5128), situated ∼38 kpc from the centre of the galaxy. The observations were taken with the Advanced Camera for Surveys instrument onboard the Hubble Space Telescope, and reach down to the horizontal branch. In this relatively small 3.8 x 3.8 kpc 2 field, after correcting for Poisson noise, we do not find any statistically strong evidence for the presence of small-scale substructures in the stellar spatial distribution on scales ≳ 100 pc. However, we do detect the presence of significant small spatial-scale inhomogeneities in the stellar median metallicity over the surveyed field. We argue that these localized chemical substructures could be associated with not fully mixed debris from the disruption of low-mass systems. NGC 5128 joins the ranks of the late-type spiral galaxies the Milky Way, for which the stellar halo appears to be dominated by small-scale spatial substructures, and NGC 891, where localized metallicity variations have been detected in the inner extraplanar regions. This suggests that the presence of small-scale substructures may be a generic property of stellar haloes of large galaxies.

A New Approach to the Analysis of Multidimensional Neuronal Activity: Markov Random Fields

How can information hidden in a spatial configuration of neuronal activity be addressed? The Markov Random Field method for the analysis of the spatial component of a multidimensional neuronal process is introduced and after simulations is applied to experimental data on rat at olivocerebellar activity. Using this method it was determined, for the first time, that the activity demonstrates dynamic coupling and may have different fine spatial substructures. The results obtained support the view that the inferior olive serves as a movement organizing centre that controls motor activity by means of spatially as well as temporally organized patterns of coherent activity. © 1997 Elsevier Science Ltd.

Interactions of solar wind streams and related small structures

Coronal holes produce high‐speed, low‐density, and high‐temperature streams that propagate into the interplanetary space. These streams interact with the slow‐speed, high‐density, and low‐temperature stream of the ambient solar wind. We investigate this problem using the time‐dependent, two‐dimensional hydrodynamic model in the spherical‐equatorial coordinate system. More accurate numerical methods and finer difference meshes used enable us to track the evolution of detailed features of the fast and slow stream interaction. An analysis of formation of shock pairs (forward and reverse shocks) is presented for both erupting and corotating parts of fast streams. Further, it is shown that the process of interaction of fast and slow solar wind streams may contain richer structures. Such structures may originate during the reconfinement process (internal shocks), spatial substructures (flux tubes), and small temporal modulations (shock wings). They may influence the global shape of stream interfaces and heating of the plasma. Finally, conclusion can be made that boundaries between the fast and slow coronal streams seem to be stable against small random fluctuations and against small introduced disturbances and the Kelvin‐Helmholtz instability is not initiated.

A Coordinate Reduction Technique for Dynamic Analysis of Spatial Substructures with Large Angular Rotations∗

ABSTRACT A substructuring technique is presented for transient dynamic analysis of systems composed of interconnected rigid and elastic bodies that undergo large angular displacements. Displacement of elastic bodies is represented by superposition of local linear elastic deformation on large displacement of body reference coordinate systems. Elastic bodies are thus represented by combined sets of reference and local elastic generalized coordinates. Modal analysis and substructuring of individual elastic components allow for elimination of insignificant modes. Equations of motion and constraint are formulated in terms of mixed sets of modal and reference generalized coordinates. Planar and spatial linkages with flexible elements are presented to illustrate use of the method developed.