Kinetics of mobile impurities and correlation functions in one-dimensional superfluids at finite temperature

We scrutinize the hydrodynamic approach for calculating dynamical correlations in one-dimensional superfluids near integrability and calculate the characteristic time scale {\tau} beyond which this approach is valid. For time scales shorter than {\tau} hydrodynamics fails and we develop an approach based on kinetics of fermionic quasiparticles described as mobile impurities. New universal results for the dynamical structure factor relevant to experiments in ultracold atomic gases are obtained.Comment: 5 pages, 2 figures. Supplemental material included. Version 3: Minor typos correcte

Mechanisms of vascular stabilization by PDGF-BB

Peripheral artery disease is a chronic condition characterised by the narrowing of peripheral arteries due to atherosclerotic plaques and subsequent decrease in blood supply. The disease mainly affects the lower limbs and it manifests clinically as limb claudication in the early stages and can progress to a more severe form characterized by rest pain and tissue loss. Morbidity and mortality are high amongst individuals affected by the disease and although lifestyle changes and medical therapy have shown some efficiency, surgical and mini-invasive revascularization are still the mainstays of treatment. Novel strategies should be investigated in order to promote the formation of new collateral arteries (arteriogenesis) and/or capillaries (angiogenesis) and restore blood flow. Vascular Endothelial Growth Factor (VEGF) is the master regulator of angiogenesis, and its delivery in ischemic tissues has been associated with improved collateral artery development. However, its therapeutic potential is challenged by the need to control both the dose and duration of expression: sustained and uncontrolled levels cause the growth of angioma-like structures, whereas transient delivery shorter than about 4 weeks is insufficient for stabilization and persistence of induced vessels. We previously found that: 1) increasing VEGF doses impair vessel stabilization by inhibiting the endothelial Semaphorin3A/Neuropilin1+ monocytes (NEM)/TGF-b1 paracrine axis, and 2) PDGF-BB co-expression restores normal angiogenesis despite high VEGF levels. Here we investigated whether and how PDGF-BB accelerates the stabilization of VEGF dose-dependent angiogenesis. For this purpose, mouse muscles were implanted with monoclonal myoblast populations homogeneously producing low, medium or high VEGF levels, with or without PDGF-BB. VEGF signaling was abrogated after 2 and 3 weeks by systemic treatment with the receptor-body Aflibercept. As expected, increasing VEGF doses progressively impaired stabilization. PDGF-BB co-expression did not change the effects of low and medium VEGF, but it greatly accelerated vascular stabilization at high VEGF (80% at 3 weeks vs 0% with VEGF alone). Aberrant vascular structures were switched to normal pericyte-covered capillaries, similar to those induced by low VEGF alone. However, stabilization was significantly greater than with low VEGF (50%), suggesting pericyte restoration may not be the only mechanism. Moreover, PDGF-BB dose-dependently stimulated endothelial Sema3A expression in vitro and restored Sema3A production, NEM recruitment and TGF-b1 level in vivo despite high VEGF levels. These results suggest that PDGF-BB dose-dependently accelerates vascular stabilization independently of pericytes recruitment through Sema3A expression and the NEM/TGF-b1 axis. In conclusion, PDGF-BB co-delivery has the potential to overcome the limitations of VEGF gene delivery (dose and duration), providing a rational strategy to improve the clinical outcome of patients with limb ischemia

Entre terreur et fascination : la foule dans le monde d’hier / Terror or Fascination: The Crowd in Nineteenth Century Europe

Nowadays the crowd no longer takes to the streets and overruns the squares and public places, or at least only occasionally. My intent in this paper is not to study the concept of ‘crowd’ as such, even supposing this were possible, nor is it to undertake a lexical analysis of the term ‘crowd’. I shall adopt a different point of view, partial, as any point of view is bound to be. At a specific historical period, the turning point of the nineteenth century, and in a restricted area of the world, Italy and France, the crowd, or what is meant by the term ‘crowd’, was a source of terror and fascination. Today, this very same term has none of its past resonance and strength, nor does it conjure up the same powerful images as it did then. However, it is precisely these images, which will always go beyond the strict meaning of the term to which they refer whilst being inextricably bound to it, that I shall discuss. From an examination of two emblematic Italian paintings of the period, my analysis will focus on the famous Psychology of Crowds by Gustave Le Bon published in 1895. What of his sharp and troubling analysis of crowd behavior is still pertinent to the world we live in today? 要旨 今日、街が群衆によって占領されることが珍しくなった。本稿は「群衆」という概念、またはその語彙を研究することを目的としていない。その代わりに「群衆」というもの自体に別の視点を提供したいと思う。１９世紀の転換期、イタリアとフランスでは「群衆」という言葉のイメージの元には魅了または恐怖があった。今日ではこの単語がかつて持っていた力やイメージは残されていない。しかし、本稿ではまさに当時の魅了と恐怖のイメージについて論じたい。このイメージは「群衆」という語にとって本質的なものではあるが、しかし常に「群衆」の狭義の意味からはこぼれ落ちるものである。イタリアで１９世紀の転換期に描かれた２枚の象徴主義の絵画の研究を元に、本稿はギュスターブ・ルボンが１８９５年に著した『群集心理』に焦点をあてる。ルボンが分析した群衆心理は現代、どのような形で残されているのだろうか

Room temperature spin crossover in molecular and polymeric materials

Spin crossover materials represent a remarkable model of molecular spin switching, where a transition between low spin and high spin configurations can be reversibly triggered by suitable external stimuli and is often accompanied by a hysteresis of various physical properties, holding potential for application in memory devices and optical switches. This thesis work investigates the thermal spin crossover behaviour of a class of Fe(II)-triazole polymers where the chemical properties can be tailored to achieve solubility in common solvents and one mononuclear Fe(II) complex deemed suitable for thermal evaporation. A broad spectrum of experimental techniques including magnetic, optical, calorimetric and structural assessments are applied to characterise the spin crossover phenomena in powders, thick films and pellets, highlighting the impact of the molecular environment and the effects of the processing methods on the spin switching. Additionally, thermal expansion measurements with a capacitance dilatometer provide a macroscopic evaluation of the mechanical changes associated with the transitions, which mirror the expansion/contraction of the Fe coordination sphere at the molecular level. Solution processing and vacuum deposition of the materials further enables the preparation and study of stable thin films, better suited to device application, with optical characterisation confirming the retention of spin crossover thermochromic properties. As a first step to deploy the iron-polymers inside simple electronic devices, MIM structures (metal-insulator-metal) are fabricated and tested by impedance spectroscopy, showing the presence of a thermal hysteresis loop in the dielectric function around room temperature. We demonstrate that in addition to the previous studies on bulk powders, optical and dielectric bistability with sharp spin transitions can also be achieved for thin films devices, thus opening interesting new perspectives for the application of spin crossover polymeric and molecular materials.Open Acces

Structure-properties relationships in bioactive glasses for PAA-based polyalkenoate cements

Los cementos óseos basados en polimetilmetacrilato (PMMA) se han utilizado ampliamente en los últimos 30 años para aplicaciones en medicina. Sin embargo, la utilización de estos cementos está relacionada con una serie de problemas, debidos por ejemplo a la presencia de monómero de PMMA no reaccionado que puede tener efectos tóxicos en el organismo del huésped, y al calor producido por la exotermia de la reacción de curado del polímero in situ. Lo cementos de ionómero de vidrio (GIC) se forman a partir de una mezcla de un ácido polimérico, generalmente ácido poliacrílico (PAA), con polvo de vidrio de alúminosilicato, degradable por ataque ácido, en una solución aquosa. Es importante notar que, por el hecho de ser una reacción de salificación antes que una polimerización, la exotermia asociada a la reacción es muy baja. Además estos materiales pueden formar una unión adhesiva entre el hueso y los metales que normalmente se emplean en cirugía ortopédica [1]. Otra característica remarcable de los cementos de ionómero de vidrio es que pueden manifestar un comportamiento bioactivo en el sentido en que pueden liberar iones osteoconductivos. Así pues, desde cuando fueron introducidos por Wilson en los años sesenta, estos materiales han sido indicados como una alternativa válida a los cementos basados en PMMA para aplicaciones en ortopedia y, además, como alternativa a las amalgamas de mercurio normalmente utilizadas en odontología. Se han producido dos series de vidrio substituyendo progresivamente calcio por magnesio y variando a la vez la fracción molar de silicio, mientras que el contenido de sodio se ha mantenido constante a lo largo de las dos series. Para caracterizar los vidrios se han utilizado diferentes técnicas cuales difracción de rayos X, análisis térmica y análisis del tamaño de partícula. Utilizando los conceptos del modelo del vidrio como polímero inorgánico se ha evaluado la influencia de la sustitución progresiva de calcio por magnesio sobre la network connectivity (NC) a través de técnicas de caracterización como espectroscopia FTIR, RAMAN y MAS-NMR. Por fin, para caracterizar las propiedades mecánicas de los cementos formados, han sido medidas la resisencia a compressión y el módulo elastico. A pesar de que las teorías convencionales sobre la estructura de los vidrios reporten el magnesio como un elemento modificador de red, los resultados de este trabajo sugerien que el magnesio actua más como un óxido intermedio, entrando en la red del vidrio antes que destruiendola. El objetivo de este trabajo es demostrar que la sustitución de calcio por magnesio puede resultar en la posibilidad de formar un nuevo cemento de ionómero de vidrio sin alúmina y con propiedades mecánicas comparables con las de los cementos óseos tradicionales

How the Presence of Newly Arrived Migrants Challenges Urban Spaces: Three Perspectives from Recent Literature

This article explores the notion of arrival spaces in the recent urban studies literature, and it outlines three emerging perspectives on their role and the associated processes and complexities. Recently, within changing migratory trajectories, the dimension of arrival has gained increasing relevance, and scholars have discussed the growing complexity underpinning it. Within this framework, some contributions reflect on the role of arrival spaces, which currently represent a rapidly changing research subject. However, by the term ‘arrival space,’ authors refer to various types of space, and the article argues that a clearer reference to the spatial dimension of arrival is needed. Spaces are contexts where different actors interact and intervene in the city, and their understanding represents a preliminary step for future research. In this sense, this contribution aims to unpack the previous decade’s debate on arrival spaces. It outlines three main perspectives: The first discusses the role of trans-local contexts, working as nodes in international migration networks; the second follows the debate on arrival neighborhoods; the third suggests that arrival spaces may be defined as all those parts of the urban fabric with which newcomers interact at the moment of arrival. Finally, drawing from this review, the article underlines that arrival spaces are not only specialized areas with migrant newcomers’ concentration, but they may also be ordinary urban spaces that temporarily work for arrival. Hence, future research should further deepen this perspective and more explicitly investigate the relation of arrival spaces to the city and its actors

Confinement et foule virtuelle : Rationalité médicale et panique collective / Lockdowns and Virtual Crowds: Medical Rationality and Collective Panic

There have been many epidemics in the past, but the Covid-19 outbreak is the first worldwide epidemic, or more precisely pandemic, to have been subject to continuous media coverage. What impact did this media flow have on our behaviour, both individually and collectively? In many countries moreover, Italy and France in particular (the two countries of reference for this analysis), lockdown orders forbade all public gatherings and suddenly, the streets, the squares, the public places in general were completely deserted. So if, as is generally accepted, a crowd is understood as being a gathering of human beings in a given space (a square, a stadium, …) with a common purpose, usually celebrations or protests, the lockdowns we experienced, causing geographic and social atomization, would, therefore, seem to be an exact antithesis. Nonetheless, a crowd, albeit a virtual crowd, united by fear in the face of an unprecedented threat relentlessly relayed by the media, did indeed exist. Moreover, this ‘crowd that was not a crowd’ was governed by certain behaviours specific to physical crowds. In this paper, I would like to discuss these behaviours and their causes