Sector-based Fresnel zone plate with extended depth of focus

A Sector-based Fresnel zone plate consists of a binary diffractive lens composed of a mosaic of sectors of Fresnel zone plates with different focal distances. When these focal distances are linearly distributed within the sectors, dual focus is obtained. Besides, we explore the possibility to generate an extended depth-of-focus lens by using a cubic distribution of the focal distances assigned to the sectors and optimizing the weight factors given to the terms of the cubic polynomial. Finally, numerical simulations based on the Rayleigh-Sommerfeld approach are carried out and experimental verifications by using a Spatial Light Modulator are performed, showing high agreement. The proposed kind of zone plate has potential applications in different research fields such as microscopy, lithography, data storage, or imaging

Caída de bloques de hielo en los frentes del glaciar de casquete de la isla Livingston (Archipiélago de las Shetland del Sur). Detección por métodos sísmicos. Influencia de las variables ambientales

We used data from a seismic array to study the evolution of calving at Livingston Island. Starting with the idea that the flow is the main cause of calving, we examined the effect of temperature, tide, relative humidity and wind velocity on this phenomenon. Air temperature proved to be the most relevant parameter

Caída de bloques de hielo en los frentes del glaciar de casquete de la isla Livingston (Archipiélago de las Shetland del Sur). Detección por métodos sísmicos. Influencia de las variables ambientales

Se han utilizado los datos procedentes de una red (array) sísmica situada en la isla Livingston para estudiar la evolución de las caídas de bloques de hielo en los frentes de los glaciares (calving). Partiendo de que la causa fundamental de las caídas de bloques es el flujo del hielo, se ha estudiado la influencia de la temperatura ambiental, la variación del nivel de la marea, la humedad y la velocidad del viento sobre este fenómeno. Como principal conclusión se deduce que la temperatura ambiental es el factor que ejerce una mayor y más directa influencia sobre las caídas de los bloques de hielo.We used data from a seismic array to study the evolution of calving at Livingston Island. Starting with the idea that the flow is the main cause of calving, we examined the effect of temperature, tide, relative humidity and wind velocity on this phenomenon. Air temperature proved to be the most relevant parameter

Accurate quantification of apoptosis progression and toxicity using a dielectrophoretic approach

A loss of ability of cells to undergo apoptosis (programmed cell death, whereby the cell ceases to function and destroys itself) is commonly associated with cancer, and many anti-cancer interventions aim to restart the process. Consequently, the accurate quantification of apoptosis is essential in understanding the function and performance of new anti-cancer drugs. Dielectrophoresis has previously been demonstrated to detect apoptosis more rapidly than other methods, and is low-cost, label-free and rapid, but has previously been unable to accurately quantify cells through the apoptotic process because cells in late apoptosis disintegrate, making cell tracking impossible. In this paper we use a novel method based on light absorbance and multi-population tracking to quantify the progress of apoptosis, benchmarking against conventional assays including MTT, trypan blue and Annexin-V. Analyses are performed on suspension and adherent cells, and using two apoptosis-inducing agents. IC50 measurements compared favourably to MTT and were superior to trypan blue, whilst also detecting apoptotic progression faster than Annexin-V

Arc-parallel vs back-arc extension in the Western Gibraltar arc : is the Gibraltar forearc still active?

Extremely tight arcs, framed within the Eurasia-Africa convergence region, developed during the Neogene on both sides of the western Mediterranean. A complex interplate deformation zone has been invoked to explain their structural trend-line patterns, the shortening directions and the development of back-arc basins. Updated structural and kinematic maps, combined with earthquake data covering the complete hinge zone of the western Gibraltar arc help us to explore the mode of strain partitioning from 25My ago to present. During the Miocene, the strain partitioning pattern showed arc-perpendicular shortening in the active orogenic wedge -assessed from the radial pattern of tectonic transport directions- accompained by subhorizontal stretching. Structures accommodating stretching fall into two categories on the basis of their space distribution and their relationships with the structural trend-line pattern: i) arc-parallel stretching structures in the external wedge (mainly normal faults and conjugate strike-slip faults); and ii) extensional faults developed in the hinterland zone in which transport directions are centripetal towards the Alborán back-arc basin. Pliocene to Recent deformational structures together with focal solutions from crustal earthquakes (n=167; 1.

Mach-Zehnder-based measurement of light emitting diodes temporal coherence

Objectives: The main objective of this work is to validate a Mach-Zehnder based interferometric method to measure the temporal coherence length of broadband finite size light sources such as Light Emitting Diodes (LEDs), and give a qualitative value of the temporal coherence length of white LEDs, for which nor their spectral width neither their emission peak wavelength are clearly defined. Motivation: Low-coherence light sources such as LEDs have opened many possibilities in applications in which using lasers introduces coherent noise (speckle) that hinders the performance of interferometric measurement techniques. The coherence length is an important characteristic of light sources for scientific applications related to diffraction, holography, tomography, or interferometry. The spatial coherence of a source depends on the distance from the source to the observation plane and its size, while the temporal coherence is related to the emission spectral width and the emission peak wavelength. Therefore, the temporal coherence is a characteristic of each source. Methodology and results: In this work, we use a Mach-Zehnder interferometer for the first time to measure the coherence degree and the temporal coherence length of quasi-monochromatic LEDs. We validate the technique by comparing the results to those obtained directly from the spectrum. Then, we use the tested interferometric method to measure the temporal coherence length of a white LED, for which neither the width of the spectrum nor the emission peak wavelength, are clearly defined. In this case, the Wiener-Khinchin theorem is used to validate the interferometric technique. A very interesting property of the method is that the temporal coherence length is obtained from a single measurement, without needing to perform a scanning. This method can be used also for other non-coherent sources such as halogen lamps, pulsed lasers, and so on. The obtained results will improve the characterization of light sources and the applications dealing with physical optics and electromagnetic interference. © 2022 The Author

Modelos deposicionales y ocupación antrópica en el NE de la Península Ibérica durante el Paleolítico Medio

En este trabajo se estudian las características geoarqueológicas y de la ocupación antrópica en los yacimientos del Estret de Tragó (Tragó de la Noguera) y de La Roca dels Bous (Sant Llorenç de Montgai), ambos del Paleolítico medio (Pleistoceno superior), situados en la comarca leridana de La Noguera. En los dos yacimientos se ha realizado un estudio litoestratigráfico y sedimentológico, que ha permitido diferenciar una serie de unidades estratigráficas y establecer sus condiciones de formación. En el primero, la sedimentación responde a las condiciones de un ambiente fluvial, mientras que en el segundo (todavía en estudio) se observan dos ambientes con una dinámica complej

Las fallas del recinto de la Alhambra : Faults in the Alhambra area

The Alhambra is built on a conglomeratic formation, known as the Alhambra Formation, whose age is Pliocene to Lower Pleistocene and has a visible thickness of 200 metres. The western part of the San Pedro escarpment corresponds to a fault-scarp with some retreat; the fault-plane outcrops in the innermost part of the escarpment, showing normal displacement and NW-SE strike with NE steep dip. This fault is the most important one of a set that outcrops along the northern hillslope of the Alhambra. Several topographic steps with NW-SE orientation are interpreted as retreated fault-scarps. In some cases, the activity of these faults seems to be very recent and maybe related to earthquakes. The seismic risk associated with these faults (and maybe some not-outcropping ones) can be taken to be moderate, as some historical damages have been reported concerning the Alhambra walls and the fence. In this respect, the Alhambra fence has numerous cracks geometrically related to fault planes outcropping in the Alhambra Formation, i.e. faults and cracks are continuous and have similar strike and dip. We hypothesize that these cracks are due to small displacements along the faults, occurred during recent earthquakes in the region. These faults constitute mechanical discontinuities, which represent a supplementary risk, because they contribute to reduce the stability of the entire rock massif