Helium mixtures in nanotube bundles

An analogue to Raoult's law is determined for the case of a 3He-4He mixture adsorbed in the interstitial channels of a bundle of carbon nanotubes. Unlike the case of He mixtures in other environments, the ratio of the partial pressures of the coexisting vapor is found to be a simple function of the ratio of concentrations within the nanotube bundle.Comment: 3 pages, no figures, submitted to Phys. Rev. Let

On-chip mode-locked laser diode structure using multimode interference reflectors

We report, for the first time to our knowledge, an on-chip mode-locked laser diode (OCMLLD) that employs multimode interference reflectors to eliminate the need of facet mirrors to form the cavity. The result is an OCMLLD that does not require cleaved facets to operate, enabling us to locate this OCMLLD at any location within the photonic chip. This OCMLLD provides a simple source of optical pulses that can be inserted within a photonic integrated circuit chip for subsequent photonic signal processing operations within the chip (modulation, optical filtering, pulse rate multiplication, and so on). The device was designed using standardized building blocks of a generic active/passive InP technology platform, fabricated in a multi-project wafer run, and achieved mode-locking operation at its fundamental frequency, given the uncertainty at the design step of the optical length of these mirrors, critical to achieve colliding pulse mode-locked operation. © 2014 Chinese Laser Pres

Colliding Pulse Mode-Locked Laser Diode using Multimode Interference Reflectors

We present a novel fully monolithic Colliding Pulse Mode-Locked Laser Diode (CPML) using Multimode Interference Reflectors (MMIRs) to create the laser resonator. We demonstrate experimentally for the first time to our knowledge the Colliding Pulse mode-locking of a laser using MMIRs by observation of the Optical Spectrum and by measuring the frequency spacing between the modes. This component is a promising candidate for Stable Millimeter-Wave Generation in ultra-wideband wireless communication links. Multimode Interference Reflectors are very versatile components that allow avoiding the required cleaved facets to operate

Influence of the size and amount of cork particles on the toughness of a structural adhesive

The inclusion of particles (nano or micro) is a method to improve the mechanical properties such as toughness of structural adhesives. Structural adhesives are known for their high strength and stiffness but also for their low ductility and toughness. There are many processes described in the literature to increase the toughness, being one of the most common the use of rubber particles. In the present study, natural micro particles of cork are used with the objective to increase the toughness of a brittle epoxy adhesive. The idea is for the cork particles to act like as a crack stopper leading to more energy absorption. The influence of the cork particle size and amount were studied. Particles of cork ranging from 38 to 250 µm were mixed in the epoxy adhesive Araldite 2020 from Huntsman. The amount of cork in the adhesive was varied between 1 and 5% in weight. Surface treatment (low pressure plasma) was applied to the cork powder to assess the effect of the interaction adhesive-cork with several degrees of adhesion

La metafísica en la encíclica «Fides et ratio»

El pensamiento filosófico del siglo XX, principalmente a partir del segundo tercio del mismo, está marcado por la crisis de la metafísica. Dos actores directos de esta crisis son el Positivismo lógico de Wittgenstein y el Postmodernismo filosófico postheideggeriano. Estas corrientes de pensamiento fracasarían al intentar fundamentar la realidad a partir de criterios de racionalidad antimetafísicos. Consecuentemente, el hombre contemporáneo quedaría lastrado por la desconfianza de la capacidad de la razón humana para conocer la verdad; y, por lo mismo, abandonado a lo meramente práctico e instrumental y relativizando toda fundamentación del saber. Frente a este panorama, Juan Pablo II propone rescatar la dimensión metafísica de la verdad para recuperar la confianza en la razón y su capacidad de conocer la verdad; y, en definitiva, para restaurar al hombre mismo que quedó resquebrajado en su unidad interior. Tal dimensión, en la perspectiva del Papa filósofo, tiene que ver con un modo de pensar abierto al ser, a la verdad, y a la trascendencia. Se trataría, entonces, de un modo de pensar que, lejos de ser un modelo único de metafísica, es la propiedad interior de toda filosofía que le hace estar orientada hacia la verdad y que, estrictamente hablando, da identidad filosófica a cualquier esfuerzo especulativo. De este modo, Fides et ratio traza la senda que la reflexión filosófica debería seguir para superar la crisis de verdad que caracteriza el pensamiento moderno y contemporáneo. La superación de esta crisis es vital para el hombre porque no se trata de alcanzar una verdad abstracta o teórica sino más bien vivencial y decisiva para su existencia. La verdad que Fides et ratio propone es la que permite alcanzar también la plena verdad sobre sí mismo.Twentieth century philosophical thinking, principally during the second-third of that century, is marked by the crisis of metaphysics. Two direct actors in this crisis are logical Positivism of Wittgenstein and post-Heidegger philosophical Postmodernism. These currents of thought would fail if they intend to found reality in the criteria of anti-metaphysical rationality. Consequently, modern humanity would be burdened by the lack of confidence in the capacity of human reason to know truth; and, for the same reason, abandoned to the merely practical and instrumental, relativizing all foundations of knowledge. In confronting this perspective, John Paul II proposed to rescue the metaphysical dimension of truth to recover confidence in reason and its capacity to know truth; and, definitively, to restore humanity itself whose interior unity is left fractured. That dimension, in the perspective of the philosopher-Pope, deals with a mode of thinking open to being, to truth, and to the transcendent. It addresses, then, one way of thinking that, far from a unified model of metaphysics, is the interior property of every philosophy that is oriented to truth and which, strictly speaking, lends philosophical identity to any speculative endeavor. In this mode, Fides et ratio traces the path that philosophical reflection should follow to overcome the crisis of truth that characterizes modern and contemporary thought. Overcoming this crisis is vital for humanity because it is not about reaching an abstract or theoretical truth but rather experiential and decisive for its existence. The truth that Fides et ratio proposes is that which allows for also reaching the fullness of truth over itself

Possible satellite-based observations of the 1997 Leonid meteoroids

The Block IIA GPS satellites are equipped with a sensor designed to detect electromagnetic transients. Several phenomena will produce triggers in this sensor. They include earth-based electromagnetic transients such as lightning and two space-based phenomena--deep dielectric discharge and meteoroid or hyper-velocity micro-gram particle impact (HMPI). Energetic electrons in the GPS environment cause the deep dielectric charging. HMPIs cause triggers through the transient electric fields generated by the ejecta plasma. During the 1997 Leonid passage the energetic particle fluxes were very low. In the presence of such low fluxes the typical median trigger rate is 20 per minute with a standard deviation of about 20 per minute. Between 0800 UT and 1200 UT on November 17, 1997, the sensor on a specially configured satellite observed trigger rates more than 10 sigma above the nominal median rate. Sensors on other Block IIA GPS satellites also observed excess triggers during November. Detection is enhanced when the sensor antenna is oriented into the Leonid radiant. While many questions persist the authors feel that it is likely that the excess events during the November interval were caused by the close approach of the satellites to the Leonid meteoroid path

Efeito de reguladores de crescimento no potencial osmótico de tomateiro (Lycopersicon esculentum Mill. cv. Angela)

This research deals with the effects of exogenous growth regulators on leaf osmotic potential of tomato cultivar "Angela". To study the influence of growth substances on osmotic potentia, (2-chloroethyl) trimethylammonium chloride (CCC) at concentration of 2,000 ppm, succinic acid-2,2-dirnethylhydrazide (Alar) (3,000 ppm), and potassium gibberellate (Gibrel) (100 ppm) were applied. The leaf osmotic potential established everyday during six days showed that plants treated with Gibrel presented lower (negative) osmotic potential. CCC promoted better equilibrium in the osmotic potential of tomato plants. Leaves of tomato cultivar "Angela" presented higher osmotic potential in the morning in relation to leaves collected in the afternoon.A importância do estudo do potencial osmótico das plantas deve-se ao fato deste parâmetro ser considerado o principal componente do potencial hídrico, refletindo o equilíbrio de água na planta. Determinou-se o potencial osmótico foliar do tomateiro (Lycopersicon esculentum Mill. cv. "Angela") através de osmômetro de precisão. As plantas haviam sido tratadas com cloreto de (2-cloroetil) trimetilamônio (CCC) 2000 ppm, ácido succínico-2,2-dimetilhidrazida (Alar) 3000 ppm e giberelato de potássio (Gibrel) 100 ppm, além do controle. Verificou-se que o Gibrel promoveu uma redução no potencial osmótico; sendo que Alar provocou flutuações no potencial do tomateiro "Angela". O CCC causou maior equilíbrio no potencial osmótico foliar do tomateiro. Observou-se que as folhas da cultivar "Angela'' mostraram potencial osmótico mais alto pela manhã com relação ao período da tarde

Fully monolithic photonic integrated circuits for microwave and millimeter wave signal generation

We present two different photonic integrated circuits aimed to generate electrical signals within the microwave and millimeter wave range with two different techniques. The first approach uses the heterodyne technique, implementing a monolithic dual wavelength source by integrating on a single chip two distributed feedback (DFB) lasers together with the high speed photodiode. The second approach, using mode locked lasers, describes a novel device structure based on multimode interference reflectors (MIR)

Predicting environmental gradients with fern species composition in Brazilian Amazonia

Conclusions: Fern species composition can be used as an indicator of soil cation concentration, which can be expected to be relevant also for other components of rain forests. Presence-absence data are adequate for this purpose, which makes the collecting of additional data potentially very rapid. Comparison with earlier studies suggests that edaphic preferences of fern species have good transferability across geographical regions within lowland Amazonia. Therefore, species and environmental data sets already available in the Amazon region represent a good starting point for generating better environmental and floristic maps for conservation planning.</p