The rigidity of periodic body-bar frameworks on the three-dimensional fixed torus

We present necessary and sufficient conditions for the generic rigidity of body-bar frameworks on the three-dimensional fixed torus. These frameworks correspond to infinite periodic body-bar frameworks in $\mathbb{R}^3$ with a fixed periodic lattice.Comment: 31 pages, 12 figure

Binary mixture of hard disks as a model glass former: Caging and uncaging

I have proposed a measure for the cage effect in glass forming systems. A binary mixture of hard disks is numerically studied as a model glass former. A network is constructed on the basis of the colliding pairs of disks. A rigidity matrix is formed from the isostatic (rigid) sub--network, corresponding to a cage. The determinant of the matrix changes its sign when an uncaging event occurs. Time evolution of the number of the uncaging events is determined numerically. I have found that there is a gap in the uncaging timescales between the cages involving different numbers of disks. Caging of one disk by two neighboring disks sustains for a longer time as compared with other cages involving more than one disk. This gap causes two--step relaxation of this system

The role of acidification in the inhibition of Neisseria gonorrhoeae by vaginal lactobacilli during anaerobic growth

<p>Abstract</p> <p>Background</p> <p>Vaginal lactobacilli protect the female genital tract by producing lactic acid, bacteriocins, hydrogen peroxide or a local immune response. In bacterial vaginosis, normal lactobacilli are replaced by an anaerobic flora and this may increase susceptibility to <it>Neisseria gonorrhoeae</it>, a facultative anaerobe. Bacterial interference between vaginal lactobacilli and <it>N. gonorrhoeae </it>has not been studied in liquid medium under anaerobic conditions. By co-cultivating <it>N. gonorrhoeae </it>in the presence of lactobacilli we sought to identify the relative contributions of acidification and hydrogen peroxide production to any growth inhibition of <it>N. gonorrhoeae</it>.</p> <p>Methods</p> <p>Three strains of <it>N. gonorrhoeae </it>distinguishable by auxotyping were grown in the presence of high concentrations (10⁷-10⁸cfu/mL) of three vaginal lactobacilli (<it>L. crispatus</it>, <it>L. gasseri </it>and <it>L. jensenii</it>) in an anerobic liquid medium with and without 2-(<it>N</it>-morpholino)-ethanesulfonic (MES) buffer. <it>Fusobacterium nucleatum </it>was used as an indicator of anaerobiosis. Bacterial counts were performed at 15, 20 and 25 h; at 25 h pH and hydrogen peroxide concentrations were measured.</p> <p>Results</p> <p>Growth of <it>F. nucleatum </it>to >10⁸cfu/mL at 25 h confirmed anaerobiosis. All bacteria grew in the anaerobic liquid medium and the addition of MES buffer had negligible effect on growth. <it>L. crispatus </it>and <it>L. gasseri </it>produced significant acidification and a corresponding reduction in growth of <it>N. gonorrhoeae</it>. This inhibition was abrogated by the addition of MES. <it>L. jensenii </it>produced less acidification and did not inhibit <it>N. gonorrhoeae</it>. Hydrogen peroxide was not detected in any experiment.</p> <p>Conclusions</p> <p>During anaerobic growth, inhibition of <it>N. gonorrhoeae </it>by the vaginal lactobacilli tested was primarily due to acidification and abrogated by the presence of a buffer. There was no evidence of a specific mechanism of inhibition other than acid production under these conditions and, in particular, hydrogen peroxide was not produced. The acidification potential of vaginal lactobacilli under anaerobic conditions may be their most important characteristic conferring protection against <it>N. gonorrhoeae </it>infection.</p

AI as a legal person

Abstract: The idea of the legal personhood of artificial intelligence (AI) &#8212; the idea that intelligent agents can have rights and incur obligations under the law&#8212; is controversial, and in fact is often dismissed out of hand: in this paper I will argue that, on the contrary, such legal personhood may be the next big challenge for our legal systems, and we need it to deal with the new kinds ofcomplexity introduced by AI. Furthermore, I argue that we already have experiences we can look: to this end we can draw on the reasoning applied to the legal personhood recognized for corporations and other nonhuman entities. In order to do this, I address some of the criticisms against ascribing legal personhood to AI. I also look at the Canadian and EU ethical guidelines so as to keep the development of AI within the framework of human values, and I show that an ascription of legal personhood to AI is consistent with them. I also address a few of the big issues involved in making the legal personhood of AI a reality.This paper is part of the project supported by the CONEX programme and has received funding from the Universidad Carlos III de Madrid, the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement N. 600371, el Ministerio de Economia, Industria y Competitividad (COFUND2014-51509), el Ministerio de Educacion, Cultura y Deporte (CEI-15-17) and Banco SantanderUniversidad Carlos III de Madrid (APC. Read & Publish Agreement CRUE-CSIC 2023

Multi-triangulations as complexes of star polygons

Maximal $(k+1)$-crossing-free graphs on a planar point set in convex position, that is, $k$-triangulations, have received attention in recent literature, with motivation coming from several interpretations of them. We introduce a new way of looking at $k$-triangulations, namely as complexes of star polygons. With this tool we give new, direct, proofs of the fundamental properties of $k$-triangulations, as well as some new results. This interpretation also opens-up new avenues of research, that we briefly explore in the last section.Comment: 40 pages, 24 figures; added references, update Section

Algorithms for 3D rigidity analysis and a first order percolation transition

A fast computer algorithm, the pebble game, has been used successfully to study rigidity percolation on 2D elastic networks, as well as on a special class of 3D networks, the bond-bending networks. Application of the pebble game approach to general 3D networks has been hindered by the fact that the underlying mathematical theory is, strictly speaking, invalid in this case. We construct an approximate pebble game algorithm for general 3D networks, as well as a slower but exact algorithm, the relaxation algorithm, that we use for testing the new pebble game. Based on the results of these tests and additional considerations, we argue that in the particular case of randomly diluted central-force networks on BCC and FCC lattices, the pebble game is essentially exact. Using the pebble game, we observe an extremely sharp jump in the largest rigid cluster size in bond-diluted central-force networks in 3D, with the percolating cluster appearing and taking up most of the network after a single bond addition. This strongly suggests a first order rigidity percolation transition, which is in contrast to the second order transitions found previously for the 2D central-force and 3D bond-bending networks. While a first order rigidity transition has been observed for Bethe lattices and networks with ``chemical order'', this is the first time it has been seen for a regular randomly diluted network. In the case of site dilution, the transition is also first order for BCC, but results for FCC suggest a second order transition. Even in bond-diluted lattices, while the transition appears massively first order in the order parameter (the percolating cluster size), it is continuous in the elastic moduli. This, and the apparent non-universality, make this phase transition highly unusual.Comment: 28 pages, 19 figure

Acute Surgical Pulmonary Embolectomy: A 9-Year Retrospective Analysis

Acute pulmonary embolism is a substantial cause of morbidity and death. Although the American College of Chest Physicians Evidence-Based Clinical Practice Guidelines recommend surgical pulmonary embolectomy in patients with acute pulmonary embolism associated with hypotension, there are few reports of 30-day mortality rates. We performed a retrospective review of acute pulmonary embolectomy procedures performed in 96 consecutive patients who had severe, globally hypokinetic right ventricular dysfunction as determined by transthoracic echocardiography. Data on patients who were treated from January 2003 through December 2011 were derived from health system databases of the New York State Cardiac Surgery Reporting System and the Society of Thoracic Surgeons. The data represent procedures performed at 3 tertiary care facilities within a large health system operating in the New York City metropolitan area. The overall 30-day mortality rate was 4.2%. Most patients (68 [73.9%]) were discharged home or to rehabilitation facilities (23 [25%]). Hemodynamically stable patients with severe, globally hypokinetic right ventricular dysfunction had a 30-day mortality rate of 1.4%, with a postoperative mean length of stay of 9.1 days. Comparable findings for hemodynamically unstable patients were 12.5% and 13.4 days, respectively. Acute pulmonary embolectomy can be a viable procedure for patients with severe, globally hypokinetic right ventricular dysfunction, with or without hemodynamic compromise; however, caution is warranted. Our outcomes might be dependent upon institutional capability, experience, surgical ability, and careful patient selection

Cytokine producing B-cells and their capability to polarize macrophages in giant cell arteritis

OBJECTIVE: The lack of disease-specific autoantibodies in giant cell arteritis (GCA) suggests an alternative role for B-cells readily detected in the inflamed arteries. Here we study the cytokine profile of tissue infiltrated and peripheral blood B-cells of patients with GCA. Moreover, we investigate the macrophage skewing capability of B-cell-derived cytokines.METHODS: The presence of various cytokines in B-cell areas in temporal artery (n = 11) and aorta (n = 10) was identified by immunohistochemistry. PBMCs of patients with GCA (n = 11) and polymyalgia rheumatica (n = 10), and 14 age- and sex-matched healthy controls (HC) were stimulated, followed by flow cytometry for cytokine expression in B-cells. The skewing potential of B-cell-derived cytokines (n = 6 for GCA and HC) on macrophages was studied in vitro.RESULTS: The presence of IL-6, GM-CSF, TNFα, IFNγ, LTβ and IL-10 was documented in B-cells and B-cell rich areas of GCA arteries. In vitro, B-cell-derived cytokines (from both GCA and HC) skewed macrophages towards a pro-inflammatory phenotype with enhanced expression of IL-6, IL-1β, TNFα, IL-23, YKL-40 and MMP-9. In vitro stimulated peripheral blood B-cells from treatment-naïve GCA patients showed an enhanced frequency of IL-6+ and TNFα+IL-6+ B-cells compared to HCs. This difference was no longer detected in treatment-induced remission. Erythrocyte sedimentation rate positively correlated with IL-6+TNFα+ B-cells.CONCLUSION: B-cells are capable of producing cytokines and steering macrophages towards a pro-inflammatory phenotype. Although the capacity of B-cells in skewing macrophages is not GCA specific, these data support a cytokine-mediated role for B-cells in GCA and provide grounds for B-cell targeted therapy in GCA.</p