On the ultraviolet signatures of small scale heating in coronal loops

Studying the statistical properties of solar ultraviolet emission lines could provide information about the nature of small scale coronal heating. We expand on previous work to investigate these properties. We study whether the predicted statistical distribution of ion emission line intensities produced by a specified heating function is affected by the isoelectronic sequence to which the ion belongs, as well as the characteristic temperature at which it was formed. Particular emphasis is placed on the strong resonance lines belonging to the lithium isoelectronic sequence. Predictions for emission lines observed by existing space-based UV spectrometers are given. The effects on the statistics of a line when observed with a wide-band imaging instrument rather than a spectrometer are also investigated. We use a hydrodynamic model to simulate the UV emission of a loop system heated by nanoflares on small, spatially unresolved scales. We select lines emitted at similar temperatures but belonging to different isoelectronic groups: Fe IX and Ne VIII, Fe XII and Mg X, Fe XVII, Fe XIX and Fe XXIV. Our simulations confirm previous results that almost all lines have an intensity distribution that follows a power-law, in a similar way to the heating function. However, only the high temperature lines best preserve the heating function's power law index (Fe XIX being the best ion in the case presented here). The Li isoelectronic lines have different statistical properties with respect to the lines from other sequences, due to the extended high temperature tail of their contribution functions. However, this is not the case for Fe XXIV which may be used as a diagnostic of the coronal heating function. We also show that the power-law index of the heating function is effectively preserved when a line is observed by a wide-band imaging instrument rather than a spectromenter

Reciprocity-Enhanced Optical Communication Through Atmospheric Turbulence—Part II: Communication Architectures and Performance

Free-space optical (FSO) communication provides rapidly deployable, dynamic communication links that are capable of very high data rates compared with those of radio-frequency systems. As such, FSO communication is ideal for mobile platforms, for platforms that require the additional security afforded by the narrow divergence of a laser beam, and for systems that must be deployed in a relatively short time frame. In clear-weather conditions the data rate and utility of FSO communication links are primarily limited by fading caused by microscale atmospheric temperature variations that create parts-per-million refractive-index fluctuations known as atmospheric turbulence. Typical communication techniques to overcome turbulence-induced fading, such as interleavers with sophisticated codes, lose viability as the data rate is driven higher or the delay tolerance is driven lower. This paper, along with its companion [J. Opt. Commun. Netw. 4, 947 (2012)], present communication systems and techniques that exploit atmospheric reciprocity to overcome turbulence that are viable for high data rate and low delay tolerance systems. Part I proves that reciprocity is exhibited under rather general conditions and derives the optimal power-transfer phase compensation for far-field operation. Part II presents capacity-achieving architectures that exploit reciprocity to overcome the complexity and delay issues that limit state-of-the-art FSO communications.United States. National Aeronautics and Space Administration (Air Force Contract #FA8721-05-C-0002

New spatial mechanisms for the kinematic analysis of the tibiotalar joint

In virtually unloaded conditions, the tibiotalar (ankle) joint behaves as a single degree-of-freedom system, and two fibres within the calcaneal-fibular and tibio-calcaneal ligaments remain nearly isometric throughout the flexion arc. A relevant theoretical model also showed that three articular surfaces and two ligaments act together as a mechanism to control the passive kinematics. Two equivalent spatial parallel mechanisms were formulated, with ligament fibres assumed isometric and articulating surfaces assumed rigid, either as three sphere-plane contacts, or as a single spherical pair. Predicted and measured motion in three specimens compared fairly well. Important enhancement of this previous work is here presented, with more accurate experimental data, more anatomical model surfaces, and a more robust mathematical model

Phallostethid fishes

12 p. : ill. ; 26 cm.Includes bibliographical references (p. 11-12)."The Phallostethidae (including Neostethidae) is a family comprised of approximately 20 species of small, fresh, brackish, and occasionally salt-water atherinomorph fishes of Indo-Australia. Phallostethids have variously been suggested as closest relatives of the atherinoid or cyprinodontiform fishes among the atherinomorphs, or of the polynemids or gobioids among the percomorphs. Phallostethids uniquely share several derived characters of the jaws and the anal fin with a group of Indo-Australian and Pacific atherinoids. The western Pacific Dentatherina Patten and Ivantsoff is proposed as the sister group of the Phallostethidae. The anatomy of Phallostethus Regan, the type genus, is poorly known because of the scarcity and unsatisfactory condition of available material. A report on the anatomy of Phallostethus dunckeri Regan, the sole species of the genus, based on examination of the syntypes and on unpublished notes and sketches is also included"--P. [1]

Cyprinodontiform fishes

p. [337]-557 : ill., maps ; 26 cm.Thesis (Ph. D.)--City University of New York.Includes bibliographical references (p. 547-557)."The cyprinodontiforms, or killifishes, are a large and diverse group of 900 fresh- and brackish-water species with a pantropical and temperate Laurasian distribution. Traditionally, it has been classified in five families: the worldwide, oviparous Cyprinodontidae, and four New World viviparous families: the Poeciliidae, Anablepidae, Jenynsiidae, and Goodeidae. Fishes of the diverse Cyprinodontidae, in turn, have been divided into as many as eight subfamilies. The objectives of the present study are to: (1) determine if the cyprinodontiform fishes as a whole form a monophyletic group; (2) determine if each of the five families is monophyletic; (3) define the major subgroups of cyprinodontiforms, concentrating on the genera of the Cyprinodontidae; (4) determine the interrelationships of the subgroups; (5) present a comprehensive classification of the cyprinodontiforms that reflects the interrelationships; and (6) provide a hypothesis for the distribution of the group. The following general results were obtained by using the methods of phylogenetic systematics and vicariance biogeography: (1) the cyprinodontiforms are considered to be monophyletic by their sharing derived characters of the caudal skeleton, upper jaw, gill arches, position of the first pleural rib, pectoral girdle, and aspects of breeding and development; (2) the family Cyprinodontidae is nonmonophyletic as it contains some of the most primitive and derived cyprinodontiforms; (3) each of the four viviparous families is monophyletic; however, their previous definitions in terms of uniquely derived characters have been altered; (4) the development of an annual habit, exhibited by members of the aplocheiloid killifishes and possibly some cyprinodontoids, includes derived reproductive traits exhibited to some degree by all killifishes; therefore, the annual habit does not define a monophyletic group of killifishes; (5) similarly, viviparity is not hypothesized to be a uniquely derived character, but has apparently arisen at least three times within the group; and (6) the interrelationships of cyprinodontiforms correspond, in part, with a pattern of the break-up of Pangea, except for an Andean-Eurasian sister group pair. A scheme of interrelationships of cyprinodontiforms as well as of monophyletic subgroups is presented in the form of cladograms, of which the former is transformed into a comprehensive classification of the group. The fishes under study are recognized as comprising the order Cyprinodontiformes Berg and divided into two suborders, the Aplocheiloidei (which previously comprised, in part, the Cyprinodontidae), and the Cyprinodontoidei (comprising all other cyprinodontiforms as well as the four viviparous families). In order to minimize the number of named empty categories, a numbering system is incorporated into a traditional naming system to create the new classification"--P. [341]

The IkB kinase inhibitor nuclear factor-kB essential modulator–binding domain peptide for inhibition of balloon injury-induced neointimal formation

Objective—The activation of nuclear factor-kB (NF-kB) is a crucial step in the arterial wall’s response to injury. The identification and characterization of the NF-kB essential modulator– binding domain (NBD) peptide, which can block the activation of the IkB kinase complex, have provided an opportunity to selectively abrogate the inflammation-induced activation of NF-kB. The aim of the present study was to evaluate the effect of the NBD peptide on neointimal formation.<br></br> Methods and Results—In the rat carotid artery balloon angioplasty model, local treatment with the NBD peptide (300 microg/site) significantly reduced the number of proliferating cells at day 7 (by 40%; P<0.01) and reduced injury-induced neointimal formation (by 50%; P<0.001) at day 14. These effects were associated with a significant reduction of NF-kB activation and monocyte chemotactic protein-1 expression in the carotid arteries of rats treated with the peptide. In addition, the NBD peptide (0.01 to 1 micromol/L) reduced rat smooth muscle cell proliferation, migration, and invasion in vitro. Similar results were observed in apolipoprotein E-/-, mice in which the NBD peptide (150 microg/site) reduced wire-induced neointimal formation at day 28 (by 47%; P<0.01).<br></br> Conclusion—The NBD peptide reduces neointimal formation and smooth muscle cell proliferation/migration, both effects associated with the inhibition of NF-kB activation

Equation of state at high densities and modern compact star observations

Recently, observations of compact stars have provided new data of high accuracy which put strong constraints on the high-density behaviour of the equation of state of strongly interacting matter otherwise not accessible in terrestrial laboratories. The evidence for neutron stars with high mass (M =2.1 +/- 0.2 M_sun for PSR J0751+1807) and large radii (R > 12 km for RX J1856-3754) rules out soft equations of state and has provoked a debate whether the occurence of quark matter in compact stars can be excluded as well. In this contribution it is shown that modern quantum field theoretical approaches to quark matter including color superconductivity and a vector meanfield allow a microscopic description of hybrid stars which fulfill the new, strong constraints. The deconfinement transition in the resulting stiff hybrid equation of state is weakly first order so that signals of it have to be expected due to specific changes in transport properties governing the rotational and cooling evolution caused by the color superconductivity of quark matter. A similar conclusion holds for the investigation of quark deconfinement in future generations of nucleus-nucleus collision experiments at low temperatures and high baryon densities such as CBM @ FAIR.Comment: 6 pages, 2 figures, accepted for publication in J. Phys. G. (Special Issue

Compliant actuation based on dielectric elastomers for a force-feedback device: modeling and experimental evaluation

Thanks to their large power densities, low costs and shock-insensitivity, Dielectric Elastomers (DE)seem to be a promising technology for the implementation of light and compact force-feedback devices such as,for instance, haptic interfaces. Nonetheless, the development of these kinds of DE-based systems is not trivialowing to the relevant dissipative phenomena that affect the DE when subjected to rapidly changingdeformations. In this context, the present paper addresses the development of a force feedback controller foran agonist-antagonist linear actuator composed of a couple of conically-shaped DE films and a compliantmechanism behaving as a negative-rate bias spring. The actuator is firstly modeled accounting for the viscohyperelasticnature of the DE material. The model is then linearized and employed for the design of a forcecontroller. The controller employs a position sensor, which determines the actuator configuration, and a forcesensor, which measures the interaction force that the actuator exchanges with the environment. In addition, anoptimum full-state observer is also implemented, which enables both accurate estimation of the time-dependentbehavior of the elastomeric material and adequate suppression of the sensor measurement noise. Preliminaryexperimental results are provided to validate the proposed actuator-controller architectur