Beyond Anderson localization in 1D: anomalous localization of microwaves in random waveguides.

Experimental evidence demonstrating that anomalous localization of waves can be induced in a controllable manner is reported. A microwave waveguide with dielectric slabs randomly placed is used to confirm the presence of anomalous localization. If the random spacing between slabs follows a distribution with a power-law tail (Lévy-type distribution), unconventional properties in the microwave-transmission fluctuations take place revealing the presence of anomalous localization. We study both theoretically and experimentally the complete distribution of the transmission through random waveguides characterized by α=1/2 ("Lévy waveguides") and α=3/4, α being the exponent of the power-law tail of the Lévy-type distribution. As we show, the transmission distributions are determined by only two parameters, both of them experimentally accessible. Effects of anomalous localization on the transmission are compared with those from the standard Anderson localization.

Three-dimensional axisymmetric cloak based on the cancellation of acoustic scattering from a sphere.

This Letter presents the design, fabrication, and experimental characterization of a directional three-dimensional acoustic cloak for airborne sound. The cloak consists of 60 concentric acoustically rigid tori surrounding the cloaked object, a sphere of radius 4 cm. The major radii and positions of the tori along the symmetry axis are determined using the condition of complete cancellation of the acoustic field scattered from the sphere. They are obtained through an optimization technique that combines genetic algorithm and simulated annealing. The scattering cross section of the sphere with the cloak, which is the magnitude that is minimized, is calculated using the method of fundamental solutions. The low-loss fabricated cloak shows a reduction of the 90% of the sphere scattering cross section at the frequency of 8.55 kHz.

[Information overload syndrome: a bibliographic review]. / Síndrome de la sobrecarga informativa: una revisión bibliográfica.

INTRODUCTION: We are living in the time of greatest dissemination of information in the history of the human race, and this excess of information has resulted in considering human attention as a scarce resource. Information overload is the situation in which the amount or intensity of information exceeds the individual's limited capacity for cognitive processing. OBJECTIVE: To describe the concept of information overload, its possible neurocognitive substrates, associated symptoms, causes, measures to avoid it, as well as its possible relationship with the internet and electronic devices. DEVELOPMENT: People respond differently to information overload, and this depends on individual factors as well as on the amount and characteristics of the informative stimulation. Some symptoms of information overload are: inefficient work, confusion, delay in making decisions, lack of critical evaluation of information, loss of control over information, refusal to receive communication, lack of general perspective, greater tolerance for error, anxiety, stress, etc. The limits of information processing capacity are probably conditioned by the limited metabolic energy that is distributed in the brain and remains constant regardless of the difficulty of the tasks. CONCLUSION: Attention is a limited cognitive function. In order to reduce the adverse effects of information overload, it is necessary to improve the personal management of our own cognitive resources and to understand their relationship with technology. Likewise, it is necessary to improve the handling of information through the organization, filtering and application of cognitive ergonomics design guidelines.

TITLE: Síndrome de la sobrecarga informativa: una revisión bibliográfica.Introducción. Vivimos la época de mayor difusión de información en la historia de la humanidad, y este exceso de información ha dado como consecuencia considerar la atención humana como un bien escaso. La sobrecarga informativa es la situación en la cual la cantidad o la intensidad de información exceden la capacidad limitada de procesamiento cognitivo del individuo. Objetivo. Describir el concepto de sobrecarga informativa, sus posibles sustratos neurocognitivos, síntomas asociados, causas, medidas para evitarla, así como su posible relación con internet y los dispositivos electrónicos. Desarrollo. Las personas responden de forma diferente a la sobrecarga informativa, y esto depende tanto de factores individuales como de la cantidad y características de la estimulación informativa. Algunos síntomas de la sobrecarga informativa son: trabajo ineficiente, confusión, retraso al tomar decisiones, falta de evaluación crítica de la información, pérdida de control sobre la información, rechazo de la recepción en la comunicación, falta de perspectiva general, mayor tolerancia al error, ansiedad, estrés, etc. Probablemente, los límites de la capacidad de procesamiento de información estén condicionados por la energía metabólica limitada que se distribuye en el cerebro y que permanece constante independientemente de la dificultad de las tareas. Conclusión. La atención es una función cognitiva limitada. Para que los efectos adversos de la sobrecarga informativa puedan disminuirse, se requiere mejorar la gestión personal de nuestros propios recursos cognitivos y comprender su relación con la tecnología. Es necesario mejorar el manejo de información mediante la organización, el filtrado y la aplicación de pautas de diseño de ergonomía cognitiva.

Experimental Evidence of Rainbow Trapping and Bloch Oscillations of Torsional Waves in Chirped Metallic Beams.

The Bloch oscillations (BO) and the rainbow trapping (RT) are two apparently unrelated phenomena, the former arising in solid state physics and the latter in metamaterials. A Bloch oscillation, on the one hand, is a counter-intuitive effect in which electrons start to oscillate in a crystalline structure when a static electric field is applied. This effect has been observed not only in solid state physics but also in optical and acoustical structured systems since a static electric field can be mimicked by a chirped structure. The RT, on the other hand, is a phenomenon in which the speed of a wave packet is slowed down in a dielectric structure; different colors then arrive to different depths within the structure thus separating the colors also in time. Here we show experimentally the emergence of both phenomena studying the propagation of torsional waves in chirped metallic beams. Experiments are performed in three aluminum beams in which different structures were machined: one periodic and two chirped. For the smaller value of the chirping parameter the wave packets, with different central frequencies, are back-scattered at different positions inside the corrugated beam; the packets with higher central frequencies being the ones with larger penetration depths. This behavior represents the mechanical analogue of the rainbow trapping effect. This phenomenon is the precursor of the mechanical Bloch oscillations, which are here demonstrated for a larger value of the chirping parameter. It is observed that the oscillatory behavior observed at small values of the chirp parameter is rectified according to the penetration length of the wave packet.

Síndrome de la sobrecarga informativa: una revisión bibliográfica / Information overload syndrome: a bibliographic review

Introducción: Vivimos la época de mayor difusión de información en la historia de la humanidad, y este exceso de información ha dado como consecuencia considerar la atención humana como un bien escaso. La sobrecarga informativa es la situación en la cual la cantidad o la intensidad de información exceden la capacidad limitada de procesamiento cognitivo del individuo. Objetivo: Describir el concepto de sobrecarga informativa, sus posibles sustratos neurocognitivos, síntomas asociados, causas, medidas para evitarla, así como su posible relación con internet y los dispositivos electrónicos. Desarrollo: Las personas responden de forma diferente a la sobrecarga informativa, y esto depende tanto de factores individuales como de la cantidad y características de la estimulación informativa. Algunos síntomas de la sobrecarga informativa son: trabajo ineficiente, confusión, retraso al tomar decisiones, falta de evaluación crítica de la información, pérdida de control sobre la información, rechazo de la recepción en la comunicación, falta de perspectiva general, mayor tolerancia al error, ansiedad, estrés, etc. Probablemente, los límites de la capacidad de procesamiento de información estén condicionados por la energía metabólica limitada que se distribuye en el cerebro y que permanece constante independientemente de la dificultad de las tareas. Conclusión: La atención es una función cognitiva limitada. Para que los efectos adversos de la sobrecarga informativa puedan disminuirse, se requiere mejorar la gestión personal de nuestros propios recursos cognitivos y comprender su relación con la tecnología. Es necesario mejorar el manejo de información mediante la organización, el filtrado y la aplicación de pautas de diseño de ergonomía cognitiva.(AU)

Introduction: We are living in the time of greatest dissemination of information in the history of the human race, and this excess of information has resulted in considering human attention as a scarce resource. Information overload is the situation in which the amount or intensity of information exceeds the individual’s limited capacity for cognitive processing. Objective: To describe the concept of information overload, its possible neurocognitive substrates, associated symptoms, causes, measures to avoid it, as well as its possible relationship with the internet and electronic devices. Development: People respond differently to information overload, and this depends on individual factors as well as on the amount and characteristics of the informative stimulation. Some symptoms of information overload are: inefficient work, confusion, delay in making decisions, lack of critical evaluation of information, loss of control over information, refusal to receive communication, lack of general perspective, greater tolerance for error, anxiety, stress, etc. The limits of information processing capacity are probably conditioned by the limited metabolic energy that is distributed in the brain and remains constant regardless of the difficulty of the tasks. Conclusion: Attention is a limited cognitive function. In order to reduce the adverse effects of information overload, it is necessary to improve the personal management of our own cognitive resources and to understand their relationship with technology. Likewise, it is necessary to improve the handling of information through the organization, filtering and application of cognitive ergonomics design guidelines.(AU)

Comment on "Theory of tailoring sonic devices: diffraction dominates over refraction".

Recently, Garcia et al. [Phys. Rev. E 67, 046606 (2003)] studied theoretically several acoustic devices with dimensions on the order of several wavelengths. Those authors also discussed experimental results previously reported by several of us [Phys. Rev. Lett. 88, 023902 (2002)]] and concluded that it is diffraction rather than refraction that is the dominating mechanism explaining the focusing effects observed in those experiments. In this Comment we reexamined their calculations and discussed why some of their interpretations of our results are misleading.

Radial Photonic Crystal for detection of frequency and position of radiation sources.

Based on the concepts of artificially microstructured materials, i.e. metamaterials, we present here the first practical realization of a radial wave crystal. This type of device was introduced as a theoretical proposal in the field of acoustics, and can be briefly defined as a structured medium with radial symmetry, where the constitutive parameters are invariant under radial geometrical translations. Our practical demonstration is realized in the electromagnetic microwave spectrum, because of the equivalence between the wave problems in both fields. A device has been designed, fabricated and experimentally characterized. It is able to perform beam shaping of punctual wave sources, and also to sense position and frequency of external radiators. Owing to the flexibility offered by the design concept, other possible applications are discussed.

Chronic caffeine consumption prevents cognitive decline from young to middle age in rats, and is associated with increased length, branching, and spine density of basal dendrites in CA1 hippocampal neurons.

Chronic caffeine consumption has been inversely associated with the risk of developing dementia and Alzheimer's disease. Here we assessed whether chronic caffeine treatment prevents the behavioral and cognitive decline that male Wistar rats experience from young (≈3 months) to middle age (≈10 months). When animals were young they were evaluated at weekly intervals in three tests: motor activity habituation in the open field (30-min sessions at the same time on consecutive days), continuous spontaneous alternation in the Y-maze (8 min), and elevated plus-maze (5 min). Afterward, rats from the same litter were randomly assigned either to a caffeine-treated group (n=13) or a control group (n=11), which received only tap water. Caffeine treatment (5 mg/kg/day) began when animals were ≈4 months old, and lasted for 6 months. Behavioral tests were repeated from day 14 to day 28 after caffeine withdrawal, a time period that is far in excess for the full excretion of a caffeine dose in this species. Thirty days after caffeine discontinuation brains were processed for Golgi-Cox staining. Compared with controls, we found that middle-aged rats that had chronically consumed low doses of caffeine (1) maintained their locomotor habituation during the second consecutive day exposure to the open field (an index of non-associative learning), (2) maintained their exploratory drive to complete the conventional minimum of nine arm visits required to calculate the alternation performance in the Y-maze in a greater proportion, (3) maintained their alternation percentage above chance level (an index of working memory), and (4) did not increase the anxiety indexes assessed by measuring the time spent in the open arms of the elevated plus maze. In addition, morphometric analysis of hippocampal neurons revealed that dendritic branching (90-140 µm from the soma), length of 4th and 5th order branches, total dendritic length, and spine density in distal dendritic branches were greater in the basal but not the apical dendrites of CA1 pyramidal neurons from rats chronically treated with caffeine, in comparison with their age- and littermate-matched controls. Altogether, the present findings strengthen the epidemiological observations suggesting that prolonged caffeine intake prevents the cognitive decline associated with aging, and open the possibility that this process could be mediated by promoting the growth of dendrites and spines in neurons of the adult mammalian brain.

Improvement of postural adjustment steps in hemiparkinsonian rats chronically treated with caffeine is mediated by concurrent blockade of A1 and A2A adenosine receptors.

Chronic treatment with the non-selective adenosine receptor antagonist caffeine produces full recovery of the contralateral adjusting steps in hemiparkinsonian rats. In order to disclose which adenosine receptor subtype mediates this effect, a group of hemiparkinsonian rats (n=9) was treated with caffeine (5.15 mumol/kg/day), or equimolar doses of selective A1 (DPCPX) or A2A (ZM 241385) adenosine receptor antagonists, administered in a counterbalanced order over periods of 3 weeks, interspersed with equivalent washout intervals. Treatment with ZM 241385 caused full recovery (102+/-6%) of the contralateral forepaw stepping, while the maximal effect of DPCPX was only 73+/-7% of that produced by caffeine. The maximal effect of caffeine and ZM 241385 remained stable throughout the treatment period. The response to DPCPX showed more fluctuations, but tolerance did not develop. Stepping improvement was significantly faster with DPCPX than with ZM 241385, while caffeine had intermediate values. Stepping decrease after treatment interruption was faster with ZM 241385 than with caffeine, while DPCPX had intermediate values. In other experiments with the same rats, addition of the A2AR agonist CGS 21680 (5.15 mumol/kg) or the A1R agonist CCPA (2.71 mumol/kg) during the second week of caffeine treatment reversed the improvement of contralateral stepping by 59+/-4% and 30+/-3%, respectively. The combined treatment with CGS 21680 and CCPA caused complete reversal of the contralateral stepping recovery afforded by caffeine, which was more than additive (114+/-5%) compared with the sum of the maximal inhibition produced by either agonist administered alone (89+/-4%). In all cases, after interrupting the adenosine agonists, the effect of caffeine was fully restored. None of the aforementioned treatments induced significant changes in the stepping of the ipsilateral forepaw. Collectively, these results suggest that the improvement of postural adjustments induced by chronic treatment with low doses of caffeine in hemiparkinsonian rats is mediated by concurrent blockade of A1 and A2A adenosine receptors, with a larger involvement of the latter.

Community response to road traffic noise in the littoral region near Valencia (Spain).

The road traffic noise in three different cities and community response is presented in this paper. Road traffic noise is obtained by the equivalent continuous sound pressure level. To obtain the community response a questionnaire has been designed. Results from measurements and questionnaire have been compared and it has been found out that heavy goods traffic noise is the origin of disturbance and indisposition.

Reflectance properties of two-dimensional sonic band-gap crystals.

An analysis of the reflectance of sonic band-gap crystals consisting of square arrays of rigid cylinders in air is presented. The standing wave formed in front of the structures is studied both experimentally and theoretically. Experiments have been performed with a mobile robotized microphone that obtains pressure maps on the plane perpendicular to the axes of the cylinders. Enhancements of the standing wave ratio (SWR) are observed in frequency regions where attenuation bands appear in zero-order transmission experiments. Also, the SWR presents oscillations that can be related to the finite dimension of the structure (Fabry-Perot effect). Both features are well described by calculations based on a double-scattering approach.

Refractive acoustic devices for airborne sound.

We show that a sonic crystal made of periodic distributions of rigid cylinders in air acts as a new material which allows the construction of refractive acoustic devices for airborne sound. It is demonstrated that, in the long-wave regime, the crystal has low impedance and the sound is transmitted at subsonic velocities. Here, the fabrication and characterization of a convergent lens are presented. Also, an example of a Fabry-Perot interferometer based on this crystal is analyzed. It is concluded that refractive devices based on sonic crystals behave in a manner similar to that of optical systems.

A novel rotometer based on a RISC microcontroller.

A new, low-cost rotometer, based on a reduced instruction set computer (RISC) microcontroller, is presented. Like earlier devices, it counts the number and direction of full turns for predetermined time periods during the evaluation of turning behavior induced by drug administration in rats. The present stand-alone system includes a nonvolatile memory for long-term data storage and a serial port for data transmission. It also contains a display for monitoring the experiments and has battery backup to avoid interruptions owing to power failures. A high correlation was found (r > .988, p < 2 x 10(-14)) between the counts of the rotometer and those of two trained observers. The system reflects quantitative differences in turning behavior owing to pharmacological manipulations. It provides the most common counting parameters and is inexpensive, flexible, highly reliable, and completely portable (weight including batteries, 159 g).