Feasibility of near-unstable cavities for future gravitational wave detectors

Near-unstable cavities have been proposed as an enabling technology for future gravitational wave detectors, as their compact structure and large beam spots can reduce the coating thermal noise of the interferometer. We present a tabletop experiment investigating the behaviour of an optical cavity as it is parametrically pushed to geometrical instability. We report on the observed degeneracies of the cavity's eigenmodes as the cavity becomes unstable and the resonance conditions become hyper-sensitive to mirror surface imperfections. A simple model of the cavity and precise measurements of the resonant frequencies allow us to characterize the stability of the cavity and give an estimate of the mirror astigmatism. The significance of these results for gravitational wave detectors is discussed, and avenues for further research are suggested.Comment: 11 pages, 8 figure

Codeless App Development: Evaluating A Cloud-Native Domain-Specific Functions Approach

Mobile applications play an important role in the economy today and there is an increasing trend for app enablement on multiple platforms. However, creating, distributing, and maintaining an application remain expert tasks. Even for software developers, the process can be error-prone and resource-consuming, especially when targeting different platforms simultaneously. Researchers have proposed several frameworks to facilitate cross-platform app development, but little attention has been paid to non-technical users. In this paper, we described the Flow framework, which takes the advantage of domain-specific languages to enable no-code specification for app modeling. The cloud-native coordination mechanism further supports non-technical users to execute, monitor, and maintain apps for any target platforms. User evaluations were conducted to assess the usability and user experience with the system. The results indicated that users can develop apps in Flow with ease, but the prototype could be optimized to reduce learning time and workload

Orientation of propagating crack paths emanating from fretting-fatigue contact problems

[EN] In this work, the orientation and propagation of cracks in fretting fatigue problems is analyzed numerically using the finite element method (FEM) and the extended finite element method (X- FEM). The analysis is performed by means of a 2D model of a complete-contact fretting problem, consisting of two square indenters pressed onto a specimen subjected to cyclic fatigue. For the simulation, we allow for crack face contact in the implementation during the corresponding parts of the fatigue cycle. The problem is highly nonlinear and non-proportional and we make use of the so-called minimum shear stress range orientation criterion, min(Delta tau), proposed by the authors in previous works. This criterion is introduced to predict the crack path in each step of the crack growth simulation. The objective of the work is to detect which is the relevant parameter affecting the crack path orientation. A parametric study of some a priori relevant magnitudes is carried out, such as normal load on the indenters, bulk load on the specimen, stress ratio and relative stiffness of the indenter and specimen materials. Contrary to previous expectations, it is shown that the relative magnitude of the applied loads has no significant effect. However, it is found that the stiffness of the indenter material with respect to the specimen material has the greatest effect. A simple explanation of this behavior is also provided.The authors gratefully acknowledge the financial support given by the SGPI of the Spanish Ministry of Economy and Competitiveness (Project DPI2013-46641-R).Giner Maravilla, E.; Diaz-Alvarez, J.; Marco Esteban, M.; Miguélez, MH. (2016). Orientation of propagating crack paths emanating from fretting-fatigue contact problems. Frattura e Integrità Strutturale. Fracture and Structural Integrity. (35):417-426. https://doi.org/10.3221/IGF-ESIS.35.33S4174263

Chemistry of a Nitrosyl Ligand ¿:¿-Bridging a Ditungsten Center: rearrangement and N–O Bond cleavage reactions

The novel nitrosyl-bridged complex [W2Cp2(μ-PtBu2)(μ-κ:η-NO)(CO)(NO)](BAr4) [Ar = 3,5-C6H3(CF3)2] was prepared in a multistep procedure starting from the hydride [W2Cp2(μ-H)(μ-PtBu2)(CO)4] and involving the new complexes [W2Cp2(μ-PtBu2)(CO)4](BF4), [W2Cp2(μ-PtBu2)(CO)2(NO)2](BAr4), and [W2(μ-κ:η5-C5H4)Cp(μ-PtBu2)(CO)(NO)2] as intermediates, which follow from reactions with HBF4·OEt2, NO, and Me3NO·2H2O, respectively. The nitrosyl-bridged cation easily added chloride upon reaction with [N(PPh3)2]Cl, with concomitant NO rearrangement into the terminal coordination mode, to give [W2ClCp2(μ-PtBu2)(CO)(NO)2], and underwent N–O and W–W bond cleavages upon the addition of CNtBu to give the mononuclear phosphinoimido complex [WCp(NPtBu2)(CNtBu)2](BAr4). Another N–O bond cleavage was induced upon photochemical decarbonylation at 243 K, which gave the oxo- and phosphinito-bridged nitrido complex [W2Cp2(N)(μ-O)(μ-OPtBu2)(NO)](BAr4), likely resulting from a N–O bond cleavage step following decarbonylation

Evolution in the use of natural building stone in Madrid, Spain

Many types of stone have been used for construction in Madrid. In historical times, their use was determined by the proximity of the geological resources, the ease of quarrying and transportation links to the city. More recently, as transport connections and quarrying techniques have improved, quality and durability have become key determinants of building stone selection. Local flint was used intensively from the ninth to the eleventh century, when it was replaced by Redueña dolostone, used in turn until the seventeenth century. Granitic rocks from the Guadarrama Mountain Range that crop out in the northern and western area of the province increasingly began to be used in the city from the sixteenth century. Traditionally known as Berroqueña stone, this building stone was quarried in a number of areas; the primary point of supply was Zarzalejo, and from the eighteenth century the granite used was mainly quarried in the Alpedrete area. Eighteenth century advances in underground quarrying made it possible to extract a limestone (Colmenar stone) located in the southeastern part of the region. Together with Berroqueña stone, this limestone became one of Madrid's traditional building stones, and both, highly esteemed for their excellent petrophysical properties and durability, are still used today

Efectos del deshojado precoz sobre la composición aromática del vino Albariño en el valle del Salnés (D.O. Rías Baixas)

Este trabajo pretende estudiar los efectos del deshojado precoz sobre la composición aromática del vino Albariño. Para ello se llevó a cabo el deshojado en dos estados fenológicos de la planta, floración y cuajado y a dos intensidades distintas, 4 y 8 hojas basales. Los resultados se compararon con un control en el que no se realizó ningún deshojado. Los análisis químicos clásicos no mostraron diferencias significativas para ningún parámetro estudiado entre los vinos elaborados con los distintos tratamientos. La identificación y cuantificación de los compuestos volátiles se realizó mediante cromatografía de Gases (GC-FID). Los resultados obtenidos mostraron diferencias significativas para 14 compuestos de los 36 analizados. Se podría concluir, en este primer año de estudio, que el deshojado precoz es capaz de aumentar la composición volátil del vino Albariño

Raising and lowering operators and their factorization for generalized orthogonal polynomials of hypergeometric type on homogeneous and non-homogeneous lattice

We complete the construction of raising and lowering operators, given in a previous work, for the orthogonal polynomials of hypergeometric type on non-homogeneous lattice, and extend these operators to the generalized orthogonal polynomials, namely, those difference of orthogonal polynomials that satisfy a similar difference equation of hypergeometric type.Comment: LaTeX, 19 pages, (late submission to arXiv.org