Structural Complexity and Phonon Physics in 2D Arsenenes

In the quest for stable 2D arsenic phases, four different structures have been recently claimed to be stable. We show that, due to phonon contributions, the relative stability of those structures differs from previous reports and depends crucially on temperature. We also show that one of those four phases is in fact mechanically unstable. Furthermore, our results challenge the common assumption of an inverse correlation between structural complexity and thermal conductivity. Instead, a richer picture emerges from our results, showing how harmonic interactions, anharmonicity and symmetries all play a role in modulating thermal conduction in arsenenes. More generally, our conclusions highlight how vibrational properties are an essential element to be carefully taken into account in theoretical searches for new 2D materials

The Morality of an Artist’s House: a Laboratory for Modern Dwelling. From 1923 «Maison d’Artiste» to van Doesburg’s «Maison-Atelier»

In June 1929, Theo van Doesburg, almost 46, finished the plans to build his own maison-atelier in the outskirts of Paris. Facing for the first time a real project to be built, his former theories of 1923 maison d’artiste for the De Stijl exhibition in Paris (Galerie Rosenberg) changed into a more concerning and possible architecture. In May 1930, while his house was being built, he visited Spain and lectured in Residencia de Estudiantes,Madrid. The lecture gives some clues of this change.But as in the very beginnings of his career, he will go on in his own aspiration of breaking the limits between art and life. The maison-atelier is the test ground. For him, as in 1923, architecture had an important role to contribute to life and society not only in an esthetical but in a moral and ethical way. «We are, he said, painters that think and measure» as a way to reach a different and new culture. But also, he said: «functions of life can not be projected in two dimensions on the drawing-board. Our step, our way of sitting, eating, drinking, sleeping, working, etc., are arguments of a certain order, a rhythm in time. This order, defines the arrangement of things in space.» In Vers le Peinture Blanche, he identified white color as «perfection, purity and certainty». So does his own maison-atelier. Some years before, Le Corbusier had talked about the ripolin blanc or the lait de chaux (L’art decoratif d’aujourd’hui, 1925) as a moral argument toward the 1925 Exposition des Arts Decoratifs’ interiors excesses. In both cases, they will be thinking in artist’s houses to exemplify his theories. The former in his own house, the latter in Ozenfant’s maison-atelier. A more detailed study on van Doesburg’s house in Meudon-val-Fleury shows it as a laboratory for modern dwelling in which the manipulation of space deals with a peculiar understanding of the modern atmosphere to live in. The last issue of the De Stijl magazine included a van Doesburg postume article, we can read: «The qualities of our “environment” depend on the qualities of our work. The artist-atelier will be as a glass box or an empty glass. The painter must be white, to say, without drama and without dirty; his palette must be of glass, the brush square and hard, without dust, pure as a medical instrument...»

10 números de RA, Revista de Arquitectura

Con esta entrega se cumplen los 10 primeros números de Ra, Revista de Arquitectura. Es un momento apropiado, a pesar de tan corto recorrido, para volver brevemente la vista atrás. No se trata de una celebración, ni de una mirada autocomplaciente –este nuevo número no añade nada a la línea editorial marcada en el primero– sino más bien de agradecer y hacer partícipes a todas las personas que han colaborado en ella, del esfuerzo no pequeño que supone sacar adelante una revista académica de estas características en el inmenso panorama editorial que nos rodea. Como rezaba la consabida letra popularizada por Golpes Bajos, que hay que recordar no es sino el título de un poema de Bertold Brecht, son ‘malos tiempos para la lírica’ (por cierto, expresión que la Real Academia de la Lengua, incluye ya en el diccionario para explicar el adjetivo ‘malo’). Y es que no son precisamente las publicaciones que intentan traer a sus páginas la arquitectura desde el pensamiento, el debate, o la reflexión, las que llenan las estanterías de las librerías

Más Mies que el propio Mies. Philip Johnson y algunos límites de la originalidad

Es conocida la controversia por el parecido entre la casa Farnsworth de Ludwig Mies van der Rohe (Plano, IL, 1950) y la Glass House de Philip Johnson (New Canaan, CT, 1949). Se ha convertido en todo un paradigma moderno y ejemplo sobre la alusión y la copia o el plagio arquitectónico. Sin embargo, no debería plantearse tal polémica, al menos en cuanto a su originalidad, pues Philip Johnson publicó en septiembre de 1950 un sorprendente artículo en Architectural Review donde revelaba “las fuentes de su inspiración” y reconocía abiertamente la deuda con la casa Farnsworth y, en general, con la arquitectura de Mies. Recuperando otros textos de Johnson y revisando lo que otros autores han escrito al respecto, planteamos cómo, con el modo iconoclasta en el que publicó la Glass House, más bien estaba cuestionando los límites de la originalidad del proceso creativo

Physically founded phonon dispersions of few-layer materials, and the case of borophene

An increasing number of theoretical calculations on few-layer materials have been reporting a non-zero sound velocity for all three acoustic phonon modes. In contrast with these reports, here we show that the lowest phonon dispersion branch of atomistically described few-layer materials should be quadratic, and this can have dramatic consequencies on calculated properties, such as the thermal conductivity. By reformulating the interatomic force constants (IFC) in terms of internal coordinates, we find that a delicate balance between the IFCs is responsible for this quadraticity. This balance is hard to obtain in ab-initio calculations even if all the symmetries are numerically enforced a posteriori, but it arises naturally in our approach. We demonstrate the phenomenon in the case of borophene, where a very subtle correction to the ab-initio IFCs yields the physically correct quadratic dispersion, while leaving the rest of the spectrum virtually unmodified. Such quadraticity nevertheless has a major effect on the computed lattice thermal conductivity, which in the case of borophene changes by more than a factor 2, and reverses its anisotropy, when the subtle IFC correction is put in place

B759: Balsam Fir (Abies balsamea (L.) Mill.) Phenology in Maine

Spring phenology of balsam fir in Maine was investigated during 1978. Multiple regression models based on climatic and geographic factors were developed for predicting fir phenology and accounted for a maximum of 52.6% of the observed phenological variation. Generalized maps depicting observed and expected phenology patterns are also presented.https://digitalcommons.library.umaine.edu/aes_bulletin/1013/thumbnail.jp

Clear detection of dusty torus signatures in a Weak-Line Radio Galaxy: the case of PKS 0043-42

We report the clearest detection to date of dusty torus signatures in a Weak-Line Radio Galaxy (WLRG). The deep Spitzer InfraRed Spectrograph (IRS) rest-frame mid-infrared (MIR) spectrum of the WLRG PKS 0043-42 (z=0.116) shows a clear spectral turnover at wavelengths longer than ~20 micron suggestive of warm dust, as well as a 9.7 micron silicate absorption feature. In addition, the hard X-ray results, based on Chandra data, strongly support a picture in which PKS 0043-42 has a torus and accretion disc more typical of Strong-Line Radio Galaxies (SLRGs). The MIR and X-ray spectra are markedly different from those of other WLRGs at similar redshifts, and here we show that the former can be successfully fitted with clumpy torus models with parameters characteristic of Type-2 AGN tori: close to edge-on (i=74 deg) and relatively broad (torus angular width=60 deg), with an outer radius of 2 pc, hydrogen column density ~1.6x10^(23) cm^(-2), and AGN bolometric luminosity ~1.6x10^(44) erg s^(-1). The presence of a compact torus in PKS 0043-42 provides evidence that this WLRG is fuelled by cold, rather than hot, gas accretion. We suggest that WLRGs are a diverse population, and PKS 0043-42 may represent a type of radio galaxy in which the AGN activity has been recently re-triggered as a consequence of intermittent gas supply, or in which the covering factor of the Narrow-Line Region (NLR) clouds is relatively low.Comment: 7 pages, 6 figures, 1 table. Accepted by MNRA

Vibrational inelastic scattering effects in molecular electronics

We describe how to treat the interaction of travelling electrons with localised vibrational modes in nanojunctions. We present a multichannel scattering technique which can be applied to calculate the transport properties for realistic systems, and show how it is related to other methods that are useful in particular cases. We apply our technique to describe recent experiments on the conductance through molecular junctions.Comment: LaTeX, 12 pages, 3 figure