Polarization and Strong Infra-Red Activity in Compressed Solid Hydrogen

Under a pressure of ~150 GPa solid molecular hydrogen undergoes a phase transition accompanied by a dramatic rise in infra-red absorption in the vibron frequency range. We use the Berry's phase approach to calculate the electric polarization in several candidate structures finding large, anisotropic dynamic charges and strongly IR-active vibron modes. The polarization is shown to be greatly affected by the overlap between the molecules in the crystal, so that the commonly used Clausius-Mossotti description in terms of polarizable, non-overlapping molecular charge densities is inadequate already at low pressures and even more so for the compressed solid.Comment: To appear in Phys. Rev. Let

Basement membrane components are key players in specialized extracellular matrices

More than three decades ago, basement membranes (BMs) were described as membrane-like structures capable of isolating a cell from and connecting a cell to its environment. Since this time, it has been revealed that BMs are specialized extracellular matrices (sECMs) with unique components that support important functions including differentiation, proliferation, migration, and chemotaxis of cells during development. The composition of these sECM is as unique as the tissues to which they are localized, opening the possibility that such matrices can fulfill distinct functions. Changes in BM composition play significant roles in facilitating the development of various diseases. Furthermore, tissues have to provide sECM for their stem cells during development and for their adult life. Here, we briefly review the latest research on these unique sECM and their components with a special emphasis on embryonic and adult stem cells and their niches

LA DETERMINACIÓN DEL “ELEMENTO HISTÓRICO Y MORAL” DEL VALOR DE LA FUERZA DE TRABAJO

El objetivo de este artículo es discutir la interpretación marxista dominante respecto del significado de lo que Marx llamó el “elemento histórico y moral” del valor de la fuerza de trabajo y ofrecer una lectura alternativa que sea consistente con los fundamentos de la crítica marxiana de la economía política. Para tal fin, en la primera parte del artículo, se realiza una crítica de dicha interpretación basada en el reconocimiento de su génesis histórica y su filiación con la base textual y fundamentos de la crítica marxiana de la economía política. En la segunda parte, se realiza una reconstrucción crítica del legado de Marx respecto a la determinación del valor de la fuerza de trabajo y se presenta una resignificación del elemento histórico y moral en cuestión. A DETERMINAÇÃO DO “ELEMENTO HISTÓRICO E MORAL” DO VALOR DA FORÇA DE TRABALHOO objetivo deste artigo é discutir a interpretação marxista dominante sobre o significado do que Marx chamou de “elemento histórico e moral” do valor da força de trabalho e oferecer uma leitura alternativa atrelada aos fundamentos da crítica marxiana da economia política. Para tanto, na primeira parte do artigo, realizamos uma crítica da interpretação acima citada, baseada no reconhecimento de sua gênese histórica e sua filiação com a base textual e com os fundamentos da crítica marxiana da economia política. Na segunda parte, realizamos uma reconstrução crítica do legado de Marx quanto à determinação do valor da força de trabalho e apresentamos uma ressignificação do elemento histórico e moral em questão.Palavras-chave: Elemento histórico e moral. Valor da força de trabalho. Debates marxistas. Teoria marxista do salário.THE DETERMINATION OF THE “HISTORIC AND MORAL ELEMENT” OF THE VALUE OF LABOUR POWERThe aim of this article is to challenge the prevailing Marxist interpretation of what Marx called the “historical and moral component” of the value of labour-power, and to offer an alternative reading which is consistent with the foundations of the critique of political economy. In order to do so, the first part of the article develops a critique of the aforementioned Marxist view, on the basis of a reconstruction of its historical genesis, its support on textual evidence from Marx’s works and its theoretical consistency with the foundations of the critique of political economy. Subsequently, the second part of the article undertakes a critical reconstruction of Marx’s legacy on the determination of the value of labour-power and proposes a reconsideration of the meaning of its socalled “historical and moral” component.Keywords: Historical and moral element. Value of labour-power. Marxist debates. Marx’s theory of wages.LA DÉTERMINATION DE L “ÉLÉMENT HISTORIQUE ET MORAL” DE LA VALEUR DE LA FORCE DE TRAVAILL’objectif de cet article est de discuter de l’interprétation marxiste dominante de ce que Marx appelait “l’élément historique et moral” de la valeur de la force de travail et d’offrir une lecture alternative liée aux fondements de la critique marxienne de l’économie politique. Pour ce faire, dans la première partie de l’article nous critiquons l’interprétation susmentionnée, fondée sur la reconnaissance de sa genèse historique et son affiliation à la base textuelle et aux fondements de la critique marxienne de l’économie politique. Dans la deuxième partie, nous effectuons une reconstruction critique de l’héritage de Marx concernant la détermination de la valeur de la force de travail et nous y présentons une nouvelle signification de l’élément historique et moral en question.Mots-clés: Elément historique et moral. Valeur de la force de travail. Débats marxistes. Théorie marxiste du salaire

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