Dynamics of a vibrating tip near or in intermittent contact with a surface

We discuss the stability of the tip motion in dynamic atomic force microscopy. A nonlinear dynamics analysis shows that the tip's phase space is divided in two basins of attraction. A phase space diagram dominated by either basin of attraction implies a stable motion while a substantial contribution from both basins is associated with instabilities. Because the dominance of a given basin of attraction depends on the tip-surface interaction potential and separation, stable and unstable motions are intrinsic features of an oscillating tip near or in intermittent contact with a surface.This work has been supported by the Dirección General de Investigación Científica y Técnica (PB98-0471) and the European Union (BICEPS, BIO4-CT-2112). A.S.P. acknowledges financial support from the Comunidad de Madrid.Peer reviewe

Lyapunov exponents for stochastic differential equations on semi-simple Lie groups

summary:With an intrinsic approach on semi-simple Lie groups we find a Furstenberg–Khasminskii type formula for the limit of the diagonal component in the Iwasawa decomposition. It is an integral formula with respect to the invariant measure in the maximal flag manifold of the group (i.e. the Furstenberg boundary $B=G/MAN$). Its integrand involves the Borel type Riemannian metric in the flag manifolds. When applied to linear stochastic systems which generate a semi-simple group the formula provides a diagonal matrix whose entries are the Lyapunov spectrum. Some Brownian motions on homogeneous spaces are discussed

Desarrollo de una librería de gestión de redes domóticas X10 en Java J2SE 1.6

El objetivo de este proyecto el presentar una solución de software que permita una comunicación con redes X10 igual de sencilla que lo es su instalación y despliegue. Además, este proyecto permitirá el control y monitorización de estas redes desde cualquier dispositivo, no sólo desde el propio PC conectado a la red sino desde una enorme variedad de dispositivos, y al implementar el acceso a esta red como un servicio, su integración con redes domóticas alternativas serán extremadamente simple. Se pretende diseñar un API de desarrollo de aplicaciones X10 que traslade la simplicidad del hardware y la red X10 al software de control y monitorización de estas redes, supliendo las carencias del software comercial actual. En especial, trataremos el acceso remoto a la red X10 de la forma más simple posible, para que nuestra solución sea compatible con aplicaciones programadas en cualquier lenguaje de programación y ejecutadas sobre la mayor variedad posible de dispositivos (teléfonos móviles, PDA, diversos sistemas operativos). El segundo objetivo será diseñar el API de cara a una futura integración con otras soluciones domóticas, implementando éste como un servicio accesible de forma independiente y ejecutado en segundo plano, permitiendo el acceso simple y transparente a la red X10 y su futura integración con otras redes inalámbricas como ZigBee, Bluetooth o incluso WiFi.Ingeniería de Telecomunicació

Mechanical detection of carbon nanotube resonator vibrations

Bending-mode vibrations of carbon nanotube resonator devices were mechanically detected in air at atmospheric pressure by means of a novel scanning force microscopy method. The fundamental and higher order bending eigenmodes were imaged at up to 3.1GHz with sub-nanometer resolution in vibration amplitude. The resonance frequency and the eigenmode shape of multi-wall nanotubes are consistent with the elastic beam theory for a doubly clamped beam. For single-wall nanotubes, however, resonance frequencies are significantly shifted, which is attributed to fabrication generating, for example, slack. The effect of slack is studied by pulling down the tube with the tip, which drastically reduces the resonance frequency

Modelado de paneles acústicos ranurados

El comportamiento acústico de un medio poroso común depende en gran medida de su porosidad abierta, consistiendo ésta en una red interconectada de poros que incluye porosidades cinemáticas y «sin salida». Una porosidad «sin salida» adecuadamente seleccionada puede ayudar a mejorar las propiedades de absorción acústica de dichos materiales gracias a los intercambios térmicos entre los fluidos en cada uno de estos poros. Este trabajo presenta un modelo que trata situaciones como las anteriores para el caso específico de paneles rígidos con orificios circulares dispuestos periódicamente y que contienen poros sin salida en forma de ranura. Para ello, se utilizan las soluciones analíticas que describen la propagación de ondas acústicas en poros de sección circular y en ranuras. Los resultados preliminares muestran la capacidad absorbente de estos sistemas, haciendo de ellos una interesante alternativa a las soluciones de panel perforado tradicionales. Además, el modelo demuestra ser una herramienta útil para estimar sus propiedades acústicas de una manera sencilla que también puede extenderse a otras geometrías.The acoustic behaviour of common porous media is highly dependent on their open porosity, this consisting of an interconnected network of pores including kinematic and dead-end porosities. A properly chosen dead-end porosity can help enhance the sound absorption properties of such materials because of the thermal exchanges between the fluids filling each of these pores. This work presents a model to deal with previous situations for the specific case of rigid panels with periodically arranged circular holes containing slit-like dead-end pores. Analytical solutions describing acoustic wave propagation in pores of circular cross-section and slits are used together to this end. Preliminary results show the absorption capability of these systems, making them an interesting alternative to traditional perforated panel solutions. Additionally, the model is proven to be a useful tool to estimate their acoustic properties in a simple manner that can also be extended to other geometry cases

High-sensitivity linear piezoresistive transduction for nanomechanical beam resonators

Highly sensitive conversion of motion into readable electrical signals is a crucial and challenging issue for nanomechanical resonators. Efficient transduction is particularly difficult to realize in devices of low dimensionality, such as beam resonators based on carbon nanotubes or silicon nanowires, where mechanical vibrations combine very high frequencies with miniscule amplitudes. Here we describe an enhanced piezoresistive transduction mechanism based on the asymmetry of the beam shape at rest. We show that this mechanism enables highly sensitive linear detection of the vibration of low-resistivity silicon beams without the need of exceptionally large piezoresistive coefficients. The general application of this effect is demonstrated by detecting multiple-order modes of silicon nanowire resonators made by either top-down or bottom-up fabrication methods. These results reveal a promising approach for practical applications of the simplest mechanical resonators, facilitating its manufacturability by very large-scale integration technologies. © 2014 Macmillan Publishers Limited. All rights reserved.This work was partially funded by the projects SNM (FP7-ICT-2011-8), FORCE-for-FUTURE (CSD2010-00024), ANEM (TEC2009-14517-C02-01), SGR-NANOFABRICACION (2009 SGR 265), SiNSoC (MAT2011-15159-E). M.S. acknowledges the FPU grant (Ref. AP2008-03849).Peer Reviewe

A prototipagem rápida na modelação de patologias

A utilização da prototipagem rápida tem, cada vez mais, vindo a revelar-se como uma ferramenta de extremo valor no apoio à actividade médica. Partindo de imagens médicas bidimensionais provenientes de Tomografia Computorizada (TC) ou Ressonância Magnética (MRI) é possível a obtenção de modelos tridimensionais. Os modelos produzidos por prototipagem rápida têm utilidade quer em ambiente educacional, quer em ambiente médico- cirúrgico. Podem facilitar o diagnóstico de determinadas patologias, a elaboração de procedimentos cirúrgicos complexos, o fabrico de próteses, o fabrico de instrumentos médicos bem como a visualização de estruturas anatómicas em ambiente educacional

Inappropriate hospital admission as a risk factor for the subsequent development of adverse events: a cross-sectional study

Background: All health overuse implies an unnecessary risk of patients suffering adverse events (AEs). However, this hypothesis has not been corroborated by direct estimates for inappropriate hospital admission (IHA). The objectives of the study were the following: (1) to analyze the association between IHA and the development of subsequent AEs; (2) to explore the distinct clinical and economic implications of AEs subsequent IHA compared to appropriate admissions. Methods: An observational cross-sectional study was conducted on hospitalized patients in May 2019 in a high-complexity hospital in Madrid, Spain. The Appropriateness Evaluation Protocol was used to measure IHA, and the methodologies of the Harvard Medical Practice Study and the European Point Prevalence Survey of Healthcare-associated Infections were used to detect and characterize AEs. The association between IHA and the subsequent. Results: A total of 558 patients in the hospital ward were studied. IHA increased the risk of subsequent occurrence of AEs (OR [95% CI]: 3.54 [1.87 to 6.69], versus appropriate) and doubled the mean AEs per patient (coefficient [95% CI]: 0.19 [0.08 to 0.30] increase, versus appropriate) after adjusting for confounders. IHA was a predictive variable of subsequent AEs and the number of AEs per patient. AEs developed after IHA were associated with scheduled admissions (78.9% of AEs, versus 27.9% after appropriate admissions; p < 0.001). Compared with AEs developed after appropriate admissions, AEs after IHA added 2.4 additional days of stay in the intensive care unit and incurred an extra cost of €166,324.9 for the studied sample. Conclusions: Patients with IHA have a higher risk of subsequent occurrence of AE. Due to the multifactorial nature of AEs, IHA is a possible contributing factor. AEs developed after IHA are associated with scheduled admissions, prolonged ICU stays, and resulted in significant cost overruns. © 2023, BioMed Central Ltd., part of Springer Nature

Nanomechanical properties of solvent cast polystyrene and poly(methyl methacrylate) polymer blends and self-assembled block copolymers

© 2015 Society of Photo-Optical Instrumentation Engineers (SPIE). The nanomechanical properties of solvent-cast polymer thin films have been investigated using PeakForce™ Quantitative Nanomechanical Mapping. The samples consisted of films of polystyrene (PS) and poly(methyl methacrylate) (PMMA) obtained after the dewetting of toluene solution on a polymeric brush layer. Additionally, we have probed the mechanical properties of poly(styrene-b-methyl methacrylate) block copolymers (BCP) as randomly oriented thin films. The probed films have a critical thickness <50 nm and present features to be resolved <42 nm. The Young's modulus values obtained through several nanoindentation experiments present a good agreement with previous literature, suggesting that the PeakForce™ technique could be crucial for BCP investigations, e.g., as a predictor of the mechanical stability of the different phases.This work was partially funded by the projects SNM (FP7-ICT-2011-8) and FORCE-for-FUTURE (CSD2010-00024).Peer Reviewe