Estimation of the mechanical properties of the eye through the study of its vibrational modes

Measuring the eye's mechanical properties in vivo and with minimally invasive techniques can be the key for individualized solutions to a number of eye pathologies. The development of such techniques largely relies on a computational modelling of the eyeball and, it optimally requires the synergic interplay between experimentation and numerical simulation. In Astrophysics and Geophysics the remote measurement of structural properties of the systems of their realm is performed on the basis of (helio-)seismic techniques. As a biomechanical system, the eyeball possesses normal vibrational modes encompassing rich information about its structure and mechanical properties. However, the integral analysis of the eyeball vibrational modes has not been performed yet. Here we develop a new finite difference method to compute both the spheroidal and, specially, the toroidal eigenfrequencies of the human eye. Using this numerical model, we show that the vibrational eigenfrequencies of the human eye fall in the interval 100 Hz - 10 MHz. We find that compressible vibrational modes may release a trace on high frequency changes of the intraocular pressure, while incompressible normal modes could be registered analyzing the scattering pattern that the motions of the vitreous humour leave on the retina. Existing contact lenses with embebed devices operating at high sampling frequency could be used to register the microfluctuations of the eyeball shape we obtain. We advance that an inverse problem to obtain the mechanical properties of a given eye (e.g., Young's modulus, Poisson ratio) measuring its normal frequencies is doable. These measurements can be done using non-invasive techniques, opening very interesting perspectives to estimate the mechanical properties of eyes in vivo. Future research might relate various ocular pathologies with anomalies in measured vibrational frequencies of the eye.Comment: Published in PLoS ONE as Open Access Research Article. 17 pages, 5 color figure

Utilización de fijadores externos circulares en el tratamiento de la pseudoartrosis infectada de tibia secuela de aplastamiento de miembros

Se revisan 7 casos de pseudoartrosis infectada de tibia, secuela de aplastamiento de miembros, tratadas inicialmente en el momento de la fractura con desbridamiento y fijador externo monolateral. Todos los casos eran iniciamente fracturas abiertas grado III de Gustilo. El tratamiento de la pseudoartrosis se realizó mediante desbridamiento, estabilización con fijador externo circular, cobertura de partes blandas e injerto óseo. La unión ósea se consiguió en todos los casos con una buena recuperación funcional. Se discuten las ventajas del fijador externo circular en estos casos.Seven patients with infected tibial pseuarthrosis due to crush injuries of the lower extremity and treated by using circular cxternal fixators were reviewed. All cases had tibial open fractures, Gustillo's type III. Treatment consisted of debridement, stabilization with a circular device, bone graft and coverage of soft tissues. Bone union «as achieved in all cases with a satisfactory functional recovery. The advantages of external fixators for this type of lesion are addressed

Capas finas de ZrO2 para mejorar la resistencia química de los vidriados mates de calcio

La resistencia al ataque químico de vidriados cerámicos susceptibles al mismo, concretamente formulados a partir de una frita mate de calcio, se ha mejorado depositando en la superficie una capa delgada de óxido de circonio. Un sol de circonio estabilizado es el precursor de la capa, el cual se deposita mediante aerografía sobre el vidriado cocido y con un tratamiento térmico suave (Tmax ≈ 400 ºC), es transformado en ZrO2 y anclado a la superficie. Los ensayos de resistencia química demuestran que el vidriado protegido no sufre un ataque apreciable visualmente por parte del ácido clorhídrico concentrado, condiciones en las que el mismo vidriado sin el recubrimiento resulta gravemente dañado. El precursor utilizado genera una capa de óxido de circonio que protege el vidriado subyacente, de modo que el ataque químico por parte del ácido clorhídrico queda confinado al entorno de las grietas y discontinuidades de la capa depositadaPeer reviewe

Detection of app collusion potential using logic programming

Mobile devices pose a particular security risk because they hold personal details (accounts, locations, contacts, photos) and have capabilities potentially exploitable for eavesdropping (cameras/microphone, wireless connections). The Android operating system is designed with a number of built-in security features such as application sandboxing and permission-based access control. Unfortunately, these restrictions can be bypassed, without the user noticing, by colluding apps whose combined permissions allow them to carry out attacks that neither app is able to execute by itself. While the possibility of app collusion was first warned in 2011, it has been unclear if collusion is used by malware in the wild due to a lack of suitable detection methods and tools. This paper describes how we found the first collusion in the wild. We also present a strategy for detecting collusions and its implementation in Prolog that allowed us to make this discovery. Our detection strategy is grounded in concise definitions of collusion and the concept of ASR (Access-Send-Receive) signatures. The methodology is supported by statistical evidence. Our approach scales and is applicable to inclusion into professional malware detection systems: we applied it to a set of more than 50,000 apps collected in the wild. Code samples of our tool as well as of the detected malware are available

Some functional relations derived from the Lindelöf-Wirtinger expansion of the Lerch transcendent function

The Lindelöf-Wirtinger expansion of the Lerch transcendent function implies, as a limiting case, Hurwitz’s formula for the eponymous zeta function. A generalized form of M ¨obius inversion applies to the Lindelöf-Wirtinger expansion and also implies an inversion formula for the Hurwitz zeta function as a limiting case. The inverted formulas involve the dynamical system of rotations of the circle and yield an arithmetical functional equation