bluuebunny/crossref_metadata_2025 huggingface dataset:
Towards a Relational Understanding of the Performance Ecosystem
Authors: Davis Tom
Published: June 2011

This article seeks to form a deeper understanding of the performance ecosystem by drawing parallels with Bourriaud's Relational Aesthetics and Guattari's conception of subjectivity as outlined in Chaosmosis. Through an examination of participation within performance, and a recognition of the mutability of the roles of performer, listener, instrument and environment in the creation of the music event, this article examines the place of subjectivity, the capacity for self-creation, in the formation of a group aesthetic. Such a concept places the creation of meaning not within the individual participant but rather within the relationship between participants in a situation, a relationship that recognises the interaction between individuals, societies and institutions in its production. Such a discussion helps further our understanding of the performance ecosystem as a conceptual tool.
Real-time Composition as Performance Ecosystem
Authors: Eigenfeldt Arne
Published: June 2011

This article proposes that real-time composition can be considered a new performance ecosystem. Rather than an extension of electroacoustic instruments that are used within improvisatory environments, real-time composition systems are produced by composers interested in gestural interactions between musical agents, with or without real-time control. They are a subclass of interactive systems, specifically a genre of interactive composition systems that share compositional control between composer and system. Designing the complexity of interactions between agents is a compositional act, and its outcomes are realised during performance – more so than most interactive systems, the new performance ecosystem is compositional in nature.
Flutes, Voices and Maskenfreiheit: Traversing performative layers
Authors: Penny Jean
Published: June 2011

Researching the inside story of music performance, the core of the performative act, is a journey of infinite discovery of self- and musical connection. Establishing the discourse for such an investigation can, indeed, present its challenges. Do we focus on fundamental research methodologies, strive to fit within empirical investigations, or search for new forms of articulation as we choose what to observe and share, and decide what meanings, presences, dialogues or ‘folding in of new substances’ (Schroeder and Rebelo 2009: 137) we wish to pursue in the quest for new understanding? In this paper I will focus on performance for flute with electronics, the influence of voice, and the play with Maskenfreiheit,1 as I investigate performative layers as they have emerged in my own performances of selected notated works. The influence of the electronics is integral to these encounters with extended acoustic instrument, the place of the performer's voice and the ambiguities of projection, through narrative and reflection.
Konflikte zwischen Arbeit und Familie
Authors: Wolff Hans-Georg , Höge Thomas
Published: June 2011

Der vorliegende Beitrag berichtet über die Adaptation des sechsfaktoriellen englischsprachigen Fragebogens zur Messung von Konflikten zwischen Beruf und Familie von Carlson, Kacmar und Williams (2000) . In Anlehnung an den theoretischen Ansatz von Greenhaus und Beutell (1985) differenziert das Instrument zwischen zwei Konfliktrichtungen (Arbeit → Familie, Familie → Arbeit) und drei Konfliktformen (zeit-, beanspruchungs- und verhaltensbasiert), durch deren Kreuzung sich sechs Subskalen ergeben. Die deutsche Adaptation wurde mittels Parallelübersetzung erstellt und in zwei Studien geprüft. In beiden Studien ergeben sich befriedigende interne Konsistenzen und konfirmatorische Faktorenanalysen zeigen, dass die sechsfaktorielle Struktur des Originals die Daten beider Studien angemessen abbildet. In beiden Studien wurden außerdem weitere Validierungskriterien im Selbsturteil (Studie 1) und im Fremdurteil (Studie 2) erhoben. Elf mehrheitlich auf metaanalytischen Befunden basierende Validierungshypothesen können überwiegend bestätigt werden und stützen die Validität der Skalen.
Kohärenzerleben im Arbeitskontext
Authors: Eberz Stefan , Becker Ralf , Antoni Conny H.
Published: June 2011

Das gesundheitspsychologische Konstrukt sense of coherence (Kohärenzerleben; SoC) liefert eine Erklärung dafür, warum Menschen–trotz widriger Umstände–gesund bleiben. In diesem Artikel wird erstmals untersucht, ob eine bereichsspezifische, auf den Arbeitsplatz bezogene Konzeptualisierung (Work-SoC) einen über das globale Kohärenzerleben hinausgehenden Erklärungswert hat und ob sich dieses Konstrukt im Sinne einer Meta-Ressource interpretieren lässt. Für die Studie wurden 93 Pfarrsekretärinnen befragt. Insgesamt weisen die Ergebnisse darauf hin, dass es sich bei dem Kohärenzerleben am Arbeitsplatz um ein für die ABO-Psychologie nützliches Konstrukt handelt: Das Work-SoC klärt zusätzliche Varianz arbeitsbedingter Beanspruchungen auf und erweist sich als stärkerer Prädiktor als das globale SoC. Das Konstrukt lässt sich darüber hinaus im Sinne einer Meta-Ressource interpretieren, die pathogene Einflüsse von Stressoren am Arbeitsplatz reduziert und eine integrative Erklärung dafür liefert, warum personale und externale Widerstandsressourcen am Arbeitsplatz arbeitsbedingte Beanspruchungen reduzieren.
Transmission of galactic cosmic rays through Mars atmosphere
Authors: Townsend L. W. , PourArsalan M. , Cucinotta F. A. , Kim M. Y. , Schwadron N. A.
Published: June 2011

For human operations on the surface of Mars, methods of estimating radiation exposures from galactic cosmic rays (GCRs) are needed. To facilitate making estimates of human radiation exposures for crew operations in the Martian atmosphere, lookup tables have been generated that provide doses for critical body organs and effective doses for exposures from galactic cosmic rays anywhere on the surface of Mars. The organ doses and effective doses are tabulated for carbon dioxide atmospheric shielding areal densities ranging from 0 to 300 g cm−2 followed by aluminum spacecraft or habitat shield areal densities ranging from 0 to 100 g cm−2. The Badhwar‐O'Neill GCR model for interplanetary magnetic field potentials, ranging from the most probable solar minimum (currently 417 MV) to solar maximum conditions (1800 MV) in the solar cycle, is used as input into the calculations. This model is the standard one used for space operations at the Space Radiation Analysis Group at NASA Johnson Space Center. Use of the tables is illustrated for an environment consisting of the current galactic cosmic radiation spectrum impinging on an aluminum habitat on the surface of Mars.
Above‐normal Atlantic basin hurricane season forecast
Authors: Showstack Randy
Published: June 2011

Between three and six major hurricanes with winds of 111 miles per hour and greater could whip across the Atlantic basin during what is forecast to be an above‐normal 2011 hurricane season, according to the U.S. National Oceanic and Atmospheric Administration's Climate Prediction Center (NOAA CPC). Including those, there could be a total of 6–10 hurricanes with winds of 74 miles per hour or greater and 12–18 named storms with winds of 39 miles per hour or greater during the hurricane season, which officially begins on 1 June and lasts for 6 months, NOAA administrator Jane Lubchenco said at a 19 May briefing. There is a 70% likelihood for these ranges occurring, according to NOAA.
Iceland's Grímsvötn volcano erupts
Authors: Showstack Randy
Published: June 2011

About 13 months after Iceland's Eyjafjallajökull volcano began erupting on 14 April 2010, which led to extensive air traffic closures over Europe, Grímsvötn volcano in southeastern took its turn. Iceland's most active volcano, which last erupted in 2004 and lies largely beneath the Vatnajökull ice cap, began its eruption activity on 21 May, with the ash plume initially reaching about 20 kilometers in altitude, according to the Icelandic Meteorological Office. Volcanic ash from Grímsvötn has cancelled hundreds of airplane flights and prompted U.S. president Barack Obama to cut short his visit to Ireland. As Eos went to press, activity at the volcano was beginning to subside.
Anti‐inflammatory effects of apocynin, an inhibitor of NADPH oxidase, in airway inflammation
Authors: Kim So Yong , Moon Keun‐Ai , Jo Hee‐Yeon , Jeong Sookyung , Seon Seung‐Han , Jung Eunyu , Cho You Sook , Chun Eunyoung , Lee Ki‐Young
Published: June 2011

Oxidative stress is implicated in the pathogenesis of allergic asthma and remains an attractive target for the prevention of the disease. Herein, we investigated the anti‐inflammatory effects of apocynin, a NADPH oxidase (NOX) inhibitor, in both in vitro and in vivo allergen‐induced experimental asthma mediated by Th2 hyperresponsiveness. Apocynin showed potential antioxidant activities and inhibitory effects on the activation of redox‐sensitive transcription factors, such as NF‐κB and AP‐1, induced by pro‐inflammatory stimuli, such as TNF‐α, lipopolysaccharide and Poly I:C, and that inhibited the production of pro‐inflammatory cytokines, such as TNF‐α, IL‐1β and IL‐6. In in vivo experimental asthma model, moreover, apocynin significantly attenuated ovalbumin‐induced airway hyperresponsiveness and inflammation, as shown by the attenuation of total inflammatory cell and soluble product influx into bronchoalveolar lavage fluid, such as macrophages, eosinophils, IL‐4, IL‐5, IL‐12, IL‐13 and TNF‐α. Apocynin also significantly reduced lung inflammation in the tissues. Altogether, these results suggest that apocynin may be useful in the treatment of inflammatory diseases induced by oxidative stress through NOX activity.
Insilico based designing of short peptide and ligands for calcineurin receptor
Authors: Bhandare Vishwamhabr , Jagtap T. G. , Pillai M. M. , Patil P. S.
Published: June 2011

Calcineurin is a target protein for Cyclosporin A (CsA) an immunosuppressive drug which prevents transplant rejection. CsA has complex structure of 11 amino acids, a cyclic structure with uncommon amino acids, and can’t be chemically synthesized. CsA can be synthesized commercially by using fermentation. One report shows chemical synthesis of CsA with partial success (Jason and Diver, 2002). In view of this it is proposed to model a peptide and ligand as an alternate for CsA with the same function and can be chemically synthesized. The target for Cyclosporin is Cyclophilin which forms a ternary complex with calcineurin (CN). An in silico study concludes that all four peptides (1 wild + 3 mutant) were found to bind in the catalytic site of calcineurin. Out of this, mutant3 shows better binding than the rest of the peptides with CN. Two experimental ligand molecules were selected using a virtual screening technique. Further, molecular properties and drug likeliness followed by ADMETox prediction were studied. The designed biomolecule will have great commercial value in pharmaceutical and clinical fields, and could serve as an alternative for natural Cyclosporin A obtained from biological resources. Chemosynthesis of the designed molecule will be economically feasible, and could be produced in adequate amount.
From collective periodic running states to completely chaotic synchronised states in coupled particle dynamics
Authors: Hennig D. , Burbanks A. D. , Osbaldestin A. H. , Mulhern C.
Published: June 2011

We consider the damped and driven dynamics of two interacting particles evolving in a symmetric and spatially periodic potential. The latter is exerted to a time-periodic modulation of its inclination. Our interest is twofold: First, we deal with the issue of chaotic motion in the higher-dimensional phase space. To this end, a homoclinic Melnikov analysis is utilised assuring the presence of transverse homoclinic orbits and homoclinic bifurcations for weak coupling allowing also for the emergence of hyperchaos. In contrast, we also prove that the time evolution of the two coupled particles attains a completely synchronised (chaotic) state for strong enough coupling between them. The resulting “freezing of dimensionality” rules out the occurrence of hyperchaos. Second, we address coherent collective particle transport provided by regular periodic motion. A subharmonic Melnikov analysis is utilised to investigate persistence of periodic orbits. For directed particle transport mediated by rotating periodic motion, we present exact results regarding the collective character of the running solutions entailing the emergence of a current. We show that coordinated energy exchange between the particles takes place in such a manner that they are enabled to overcome—one particle followed by the other—consecutive barriers of the periodic potential resulting in collective directed motion.
The semiclassical small-ℏ limit of loci of roots of subdominant solutions for polynomial potentials
Authors: Giller Stefan
Published: June 2011

In this paper, a description of the small-ℏ limit of loci of zeros of subdominant solutions for polynomial potentials is given called as fundamental solutions in our earlier papers. The considered potentials are those which provide us with the simple turning points only. Three types of Stokes graphs (SG’s) associated with the potentials are investigated – the general non-critical ones, the general critical ones but with only single internal Stokes line (SL), and the Stokes graphs corresponding to arbitrary multiple-well real even degree polynomial potentials with internal Stokes lines distributed on the real axis only. All these cases are considered in their both versions of the quantized and not quantized ℏ. In particular due to the fact that the small-ℏ limit is semiclassical it is shown that loci of roots of subdominant solutions in the cases considered are collected along Stokes lines. There are infinitely many roots of subdominant solutions on such lines escaping to infinity and a finite number of them on internal Stokes lines.
A new “spectroscopic” potential energy surface for formaldehyde in its ground electronic state
Authors: Yachmenev Andrey , Yurchenko Sergei N. , Jensen Per , Thiel Walter
Published: June 2011

We report a new “spectroscopic” potential energy surface (PES) of formaldehyde (H212C16O) in its ground electronic state, obtained by refining an ab initio PES in a least-squares fitting to the experimental spectroscopic data for formaldehyde currently available in the literature. The ab initio PES was computed using the CCSD(T)/aug-cc-pVQZ method at 30 840 geometries that cover the energy range up to 44 000 cm−1 above equilibrium. Ro-vibrational energies of formaldehyde were determined variationally for this ab initio PES by means of the program TROVE [Theoretical ROtation-Vibration Energies; S. N. Yurchenko, W. Thiel, and P. Jensen, J. Mol. Spectrosc. 245, 126 (2007)]10.1016/j.jms.2007.07.009. The parameter values in the analytical representation of the PES were optimized in fittings to 319 ro-vibrational energies with J = 0, 1, 2, and 5. The initial parameter values in the fittings were those of the ab initio PES, the ro-vibrational eigenfunctions obtained from this PES served as a basis set during the fitting process, and constraints were imposed to ensure that the refined PES does not deviate unphysically from the ab initio one in regions of configuration space not sampled by the experimental data. The resulting refined PES, referred to as H2CO-2011, reproduces the available experimental J ⩽ 5 data with a root-mean-square error of 0.04 cm−1.
A high-repetition rate scheme for synchrotron-based picosecond laser pump/x-ray probe experiments on chemical and biological systems in solution
Authors: Lima Frederico A. , Milne Christopher J. , Amarasinghe Dimali C. V. , Rittmann-Frank Mercedes Hannelore , Veen Renske M. van der , Reinhard Marco , Pham Van-Thai , Karlsson Susanne , Johnson Steven L. , Grolimund Daniel , Borca Camelia , Huthwelker Thomas , Janousch Markus , van Mourik Frank , Abela Rafael , Chergui Majed
Published: June 2011

We present the extension of time-resolved optical pump/x-ray absorption spectroscopy (XAS) probe experiments towards data collection at MHz repetition rates. The use of a high-power picosecond laser operating at an integer fraction of the repetition rate of the storage ring allows exploitation of up to two orders of magnitude more x-ray photons than in previous schemes based on the use of kHz lasers. Consequently, we demonstrate an order of magnitude increase in the signal-to-noise of time-resolved XAS of molecular systems in solution. This makes it possible to investigate highly dilute samples at concentrations approaching physiological conditions for biological systems. The simplicity and compactness of the scheme allows for straightforward implementation at any synchrotron beamline and for a wide range of x-ray probe techniques, such as time-resolved diffraction or x-ray emission studies.
A hybrid identification scheme combining singular entropy with ERA for wind turbine systems
Authors: Li Peng , Song Yongduan , Li Danyong , Liu Wei , Qin Ming
Published: June 2011

This paper presents an approach for identification of wind power conversion systems based on related real data from the wind farm supervisory control and data acquisition (SCADA) module. The proposed method is able to determine the order of the system more accurately and identify the system parameters more effectively, and such improvement is accomplished in two steps. The first step is to use a “hybrid” algorithm based on singular entropy increment (SEI) and weighted criterion to overcome the uncertainty and arbitrariness of traditional data based order determination methods. The second step is to blend SEI analysis and eigensystem realization algorithm (ERA) with Kalman filter to improve the parameter estimation accuracy in the presence of white noise inevitable in wind turbine systems. As a validation of the developed method, the SKYSTREAM 3.7 is used as a benchmark for simulation experiments, which demonstrate that the proposed hybrid scheme leads to good performance in wind power system order determination and parameter identification.
Improved endurance of resistive switching TiO2 thin film by hourglass shaped Magnéli filaments
Authors: Hwan Kim Gun , Ho Lee Jong , Yeong Seok Jun , Ji Song Seul , Ho Yoon Jung , Jean Yoon Kyung , Hwan Lee Min , Min Kim Kyung , Dong Lee Hyung , Wook Ryu Seung , Joo Park Tae , Seong Hwang Cheol
Published: June 2011

A modified biasing scheme was adopted to improve the electrical endurance characteristics of conducting filamentary resistive switching (RS) in a Pt/TiO2/Pt RS cell. The modified bias scheme included the application of bias voltages with alternating polarity, even though RS proceeds in non-polar mode, which results in the stable distribution of each resistance states as well as improved endurance. This was attributed to the minimized consumption of oxygen ions in the TiO2 film, which can be induced by the formation of hourglass-shaped conducting filament (HSCF). The presence of a HSCF was confirmed by high-resolution transmission electron microscopy.
Comprehensive investigation of Ge–Si bonded interfaces using oxygen radical activation
Authors: Byun Ki Yeol , Fleming Pete , Bennett Nick , Gity Farzan , McNally Patrick , Morris Michael , Ferain Isabelle , Colinge Cindy
Published: June 2011

In this work, we investigate the directly bonded germanium-silicon interfaces to facilitate the development of high quality germanium silicon hetero integration at the wafer scale. X-ray photoelectron spectroscopy data is presented which provides the chemical composition of the germanium surfaces as a function of the hydrophilic bonding reaction at the interface. The bonding process induced long range deformation is detected by synchrotron x-ray topography. The hetero-interface is characterized by measuring forward and reverse current, and by high resolution transmission electron microscopy.
Wave functions of log-periodic oscillators
Authors: Bessa V. , Guedes I.
Published: June 2011

We use the Lewis and Riesenfeld invariant method [J. Math. Phys. 10, 1458 (1969)]10.1063/1.1664991 and a unitary transformation to obtain the exact Schrödinger wave functions for time-dependent harmonic oscillators exhibiting log-periodic-type behavior. For each oscillator we calculate the quantum fluctuations in the coordinate and momentum as well as the quantum correlations between the coordinate and momentum. We observe that the oscillator with m = m0t/t0 and ω = ω0t0/t, which exhibits an exact log-periodic oscillation, behaves as the harmonic oscillator with m and ω constant.
In-plane light polarization in nonpolar m-plane CdxZn1−xO/ZnO quantum wells
Authors: Matsui Hiroaki , Tabata Hitoshi
Published: June 2011

We studied polarized photoluminescence (PL) as a function of both temperature and excitation power from m-plane CdxZn1−xO/ZnO single quantum wells having different Cd contents. The polarized PL properties at 300 K were enhanced as the Cd content increased. This enhancement is due to the anisotropic compressive strains induced within the well layers. These results are linked to the modifications of the valence band (VB) structure resulting from a change in the crystalline symmetry of CdxZn1−xO. Furthermore, there is an exception to the polarization selection rules due to excitonic localization because of a mixing of the upper VB states at low temperatures.
Interplay between temperature and composition effects on the martensitic transformation in Ni2+xMn1−xGa alloys
Authors: Li Chun-Mei , Hu Qing-Miao , Yang Rui , Johansson Börje , Vitos Levente
Published: June 2011

Martensitic transformation in Ni2+xMn1−xGa alloys is known to be controlled by the soft tetragonal elastic constant C′ of the high-temperature austenitic phase. The temperature (T) and composition (x) dependence of C′(T, x) are calculated using the first-principles exact muffin-tin orbitals method. We show that the temperature factor of C′ is dominated by the phonon-smearing term. The competition between the negative alloying effect (∂C′/∂x < 0) and the positive temperature effect (∂C′/∂T > 0) is found to lead to nearly constant C′(TM(x), x) at the critical temperature TM(x). We demonstrate that a proper account of the temperature and composition dependence of C′(T, x) is indispensable for reasonable theoretical TM(x) values.
Dramatic enhancement of thermoelectric power factor in PbTe:Cr co-doped with iodine
Authors: Paul Biplab , Rawat P. K. , Banerji P.
Published: June 2011

We report thermoelectric properties of PbTe doubly doped with chromium (Cr) and iodine (I). Cr is found to create a local enhancement of density of states (DOS) in the conduction band of PbTe, and I is found to tune the position of the Fermi level. The coincidence of the Fermi level with the enhanced DOS is found to produce up to 135% enhancement in thermopower leading to a high power factor (PF) of 56.16 × 10−4 Wm−1K−2 at 500 K. Such high value of power factor can produce thermoelectric figure of merit (ZT) above 2.
Ferrohydrodynamic relaxometry for magnetic particle imaging
Authors: Goodwill P. W. , Tamrazian A. , Croft L. R. , Lu C. D. , Johnson E. M. , Pidaparthi R. , Ferguson R. M. , Khandhar A. P. , Krishnan K. M. , Conolly S. M.
Published: June 2011

The ferrohydrodynamic properties of magnetic nanoparticles govern resolution and signal strength in magnetic particle imaging (MPI), a medical imaging modality with applications in small animals and humans. Here, we discuss the development and key results of a magnetic particle relaxometer that measures the core diameter and relaxation constant of magnetic nanoparticles. This instrument enables us to directly measure the one-dimensional MPI point spread function. To elucidate our results, we develop a simplified ferrohydrodynamic model that assumes nanoparticles respond to time varying magnetic fields according to a Debeye model of Brownian relaxation, which we verify with experimental data.
An integrated microfluidic array system for evaluating toxicity and teratogenicity of drugs on embryonic zebrafish developmental dynamics
Authors: Yang Fan , Chen Zuanguang , Pan Jianbin , Li Xinchun , Feng Jun , Yang Hui
Published: June 2011

Seeking potential toxic and side effects for clinically available drugs is considerably beneficial in pharmaceutical safety evaluation. In this article, the authors developed an integrated microfluidic array system for phenotype-based evaluation of toxic and teratogenic potentials of clinical drugs by using zebrafish (Danio rerio) embryos as organism models. The microfluidic chip consists of a concentration gradient generator from upstream and an array of open embryonic culture structures by offering continuous stimulation in gradients and providing guiding, cultivation and exposure to the embryos, respectively. The open culture reservoirs are amenable to long-term embryonic culturing. Gradient test substances were delivered in a continuous or a developmental stage-specific manner, to induce embryos to generate dynamic developmental toxicity and teratogenicity. Developmental toxicity of doxorubicin on zebrafish eggs were quantitatively assessed via heart rate, and teratological effects were characterized by pericardial impairment, tail fin, notochord, and SV-BA distance /body length. By scoring the teratogenic severity, we precisely evaluated the time- and dose-dependent damage on the chemical-exposed embryos. The simple and easily operated method presented herein demonstrates that zebrafish embryo-based pharmaceutic assessment could be performed using microfluidic systems and holds a great potential in high-throughput screening for new compounds at single animal resolution.
Electrostatic effects on contacts to carbon nanotube transistors
Authors: Cummings Aron W. , Léonard François
Published: June 2011

We use numerical simulations to investigate the effect of electrostatics on the source and drain contacts of carbon nanotube field-effect transistors. We find that unscreened charge on the nanotube at the contact-channel interface leads to a potential barrier that can significantly hamper transport through the device. This effect is largest for intermediate gate voltages and for contacts near the ohmic-Schottky crossover, but can be mitigated with a reduction in the gate oxide thickness. These results help to elucidate the important role that contact geometry plays in the performance of carbon nanotube electronic devices.
Terrestrial planet formation
Authors: Righter K. , O’Brien D. P.
Published: June 2011

Advances in our understanding of terrestrial planet formation have come from a multidisciplinary approach. Studies of the ages and compositions of primitive meteorites with compositions similar to the Sun have helped to constrain the nature of the building blocks of planets. This information helps to guide numerical models for the three stages of planet formation from dust to planetesimals (∼10
6
 y), followed by planetesimals to embryos (lunar to Mars-sized objects; few × 10
6
 y), and finally embryos to planets (10
7
–10
8
 y). Defining the role of turbulence in the early nebula is a key to understanding the growth of solids larger than meter size. The initiation of runaway growth of embryos from planetesimals ultimately leads to the growth of large terrestrial planets via large impacts. Dynamical models can produce inner Solar System configurations that closely resemble our Solar System, especially when the orbital effects of large planets (Jupiter and Saturn) and damping mechanisms, such as gas drag, are included. Experimental studies of terrestrial planet interiors provide additional constraints on the conditions of differentiation and, therefore, origin. A more complete understanding of terrestrial planet formation might be possible via a combination of chemical and physical modeling, as well as obtaining samples and new geophysical data from other planets (Venus, Mars, or Mercury) and asteroids.
Development of a spinal locomotor rheostat
Authors: Zhang Hong-Yan , Issberner Jon , Sillar Keith T.
Published: June 2011

Locomotion in immature animals is often inflexible, but gradually acquires versatility to enable animals to maneuver efficiently through their environment. Locomotor activity in adults is produced by complex spinal cord networks that develop from simpler precursors. How does complexity and plasticity emerge during development to bestow flexibility upon motor behavior? And how does this complexity map onto the peripheral innervation fields of motorneurons during development? We show in postembryonic
Xenopus laevis
frog tadpoles that swim motorneurons initially form a homogenous pool discharging single action potential per swim cycle and innervating most of the dorsoventral extent of the swimming muscles. However, during early larval life, in the prelude to a free-swimming existence, the innervation fields of motorneurons become restricted to a more limited sector of each muscle block, with individual motorneurons reaching predominantly ventral, medial, or dorsal regions. Larval motorneurons then can also discharge multiple action potentials in each cycle of swimming and differentiate in terms of their firing reliability during swimming into relatively high-, medium-, or low-probability members. Many motorneurons fall silent during swimming but can be recruited with increasing locomotor frequency and intensity. Each region of the myotome is served by motorneurons spanning the full range of firing probabilities. This unfolding developmental plan, which occurs in the absence of movement, probably equips the organism with the neuronal substrate to bend, pitch, roll, and accelerate during swimming in ways that will be important for survival during the period of free-swimming larval life that ensues.
Emergence of social cohesion in a model society of greedy, mobile individuals
Authors: Roca Carlos P. , Helbing Dirk
Published: June 2011

Human wellbeing in modern societies relies on social cohesion, which can be characterized by high levels of cooperation and a large number of social ties. Both features, however, are frequently challenged by individual self-interest. In fact, the stability of social and economic systems can suddenly break down as the recent financial crisis and outbreaks of civil wars illustrate. To understand the conditions for the emergence and robustness of social cohesion, we simulate the creation of public goods among mobile agents, assuming that behavioral changes are determined by individual satisfaction. Specifically, we study a generalized win-stay-lose-shift learning model, which is only based on previous experience and rules out greenbeard effects that would allow individuals to guess future gains. The most noteworthy aspect of this model is that it promotes cooperation in social dilemma situations despite very low information requirements and without assuming imitation, a shadow of the future, reputation effects, signaling, or punishment. We find that moderate greediness favors social cohesionby a coevolution between cooperation and spatial organization, additionally showing that those cooperation-enforcing levels of greediness can be evolutionarily selected. However, a maladaptive trend of increasing greediness, although enhancing individuals’ returns in the beginning, eventually causes cooperation and social relationships to fall apart. Our model is, therefore, expected to shed light on the long-standing problem of the emergence and stability of cooperative behavior.
Repeating patterns of virioplankton production within an estuarine ecosystem
Authors: Winget Danielle M. , Helton Rebekah R. , Williamson Kurt E. , Bench Shellie R. , Williamson Shannon J. , Wommack K. Eric
Published: June 2011

The Chesapeake Bay, a seasonally variable temperate estuary, provides a natural laboratory for examining the fluctuations and impacts of viral lysis on aquatic microorganisms. Viral abundance (VA) and viral production (VP) were monitored in the Chesapeake Bay over 4 1/2 annual cycles, producing a unique, long-term, interannual study of virioplankton production. High and dynamic VP rates, averaging 7.9 × 10
6
viruses per mL per h, indicate that viral lysis impacts a significant fraction of microorganisms in the Chesapeake. Viral-mediated bacterial mortality, VA, VP, and organic carbon release all displayed similar interannual and seasonal trends with higher values in 2003 and 2006 than in 2004 and 2005 and peaks in early spring and summer. Surprisingly, higher rates of viral lysis occurred in winter, resulting in a magnified effect of viral lysis on bacterioplankton during times of reduced productivity. Viral lysis directly impacted the organic carbon pool, contributing on average 76 μg of C per L per d, an amount capable of sustaining ∼55% of Chesapeake Bay bacterial production. The observed repeating interannual patterns of VP and lysis are likely interlinked with seasonal cycles of host abundance and diversity, which are in turn driven by annual cycles in environmental conditions, emphasizing the complex interplay of seasonality and microbial ecology in the Chesapeake Bay.
miR-23a regulation of X-linked inhibitor of apoptosis (XIAP) contributes to sex differences in the response to cerebral ischemia
Authors: Siegel Chad , Li Jun , Liu Fudong , Benashski Sharon E. , McCullough Louise D.
Published: June 2011

It is increasingly recognized that the mechanisms underlying ischemic cell death are sexually dimorphic. Stroke-induced cell death in males is initiated by the mitochondrial release of apoptosis-inducing factor, resulting in caspase-independent cell death. In contrast, ischemic cell death in females is primarily triggered by mitochondrial cytochrome
c
release with subsequent caspase activation. Because X-linked inhibitor of apoptosis (XIAP) is the primary endogenous inhibitor of caspases, its regulation may play a unique role in the response to injury in females. XIAP mRNA levels were higher in females at baseline. Stroke induced a significant decrease in XIAP mRNA in females, whereas no changes were seen in the male brain. However, XIAP protein levels were decreased in both sexes after stroke. MicroRNAs (miRNAs) predominantly induce translational repression and are emerging as a major regulators of mRNA and subsequent protein expression after ischemia. The miRNA miR-23a was predicted to bind XIAP mRNA. miR-23a directly bound the 3′ UTR of XIAP, and miR-23a inhibition led to an increase in XIAP mRNA in vitro, demonstrating that XIAP is a previously uncharacterized target for miR-23a. miR-23a levels differed in male and female ischemic brains, providing evidence for sex-specific miRNA expression in stroke. Embelin, a small-molecule inhibitor of XIAP, decreased the interaction between XIAP and caspase-3 and led to enhanced caspase activity. Embelin treatment significantly exacerbated stroke-induced injury in females but had no effect in males, demonstrating that XIAP is an important mediator of sex-specific responses after stroke.
Rapid increase in clusters of synaptophysin at onset of homosynaptic potentiation in
Aplysia
Authors: Jin Iksung , Udo Hiroshi , Hawkins Robert D.
Published: June 2011

Imaging studies have shown that even the earliest phases of long-term plasticity are accompanied by the rapid recruitment of synaptic components, which generally requires actin polymerization and may be one of the first steps in a program that can lead to the formation of new stable synapses during late-phase plasticity. However, most of those results come from studies of long-term potentiation in rodent hippocampus and might not generalize to other forms of synaptic plasticity or plasticity in other brain areas and species. For example, recruitment of presynaptic proteins during long-term facilitation by 5HT in
Aplysia
is delayed for several hours, suggesting that whereas activity-dependent forms of plasticity, such as long-term potentiation, involve rapid recruitment of presynaptic proteins, neuromodulatory forms of plasticity, such as facilitation by 5HT, involve more delayed recruitment. To begin to explore this hypothesis, we examined an activity-dependent form of plasticity, homosynaptic potentiation produced by tetanic stimulation of the presynaptic neuron in
Aplysia
. We found that homosynaptic potentiation involves presynaptic but not postsynaptic actin and a rapid (under 10 min) increase in the number of clusters of the presynaptic vesicle-associated protein synaptophysin. These results indicate that rapid recruitment of synaptic components is not limited to hippocampal potentiation and support the hypothesis that activity-dependent types of plasticity involve rapid recruitment of presynaptic proteins, whereas neuromodulatory types of plasticity involve more delayed recruitment.
Genetic diversity and population structure of the endangered marsupial
Sarcophilus harrisii
(Tasmanian devil)
Authors: Miller Webb , Hayes Vanessa M. , Ratan Aakrosh , Petersen Desiree C. , Wittekindt Nicola E. , Miller Jason , Walenz Brian , Knight James , Qi Ji , Zhao Fangqing , Wang Qingyu , Bedoya-Reina Oscar C. , Katiyar Neerja , Tomsho Lynn P. , Kasson Lindsay McClellan , Hardie Rae-Anne , Woodbridge Paula , Tindall Elizabeth A. , Bertelsen Mads Frost , Dixon Dale , Pyecroft Stephen , Helgen Kristofer M. , Lesk Arthur M. , Pringle Thomas H. , Patterson Nick , Zhang Yu , Kreiss Alexandre , Woods Gregory M. , Jones Menna E. , Schuster Stephan C.
Published: June 2011

The Tasmanian devil (
Sarcophilus harrisii
) is threatened with extinction because of a contagious cancer known as Devil Facial Tumor Disease. The inability to mount an immune response and to reject these tumors might be caused by a lack of genetic diversity within a dwindling population. Here we report a whole-genome analysis of two animals originating from extreme northwest and southeast Tasmania, the maximal geographic spread, together with the genome from a tumor taken from one of them. A 3.3-Gb de novo assembly of the sequence data from two complementary next-generation sequencing platforms was used to identify 1 million polymorphic genomic positions, roughly one-quarter of the number observed between two genetically distant human genomes. Analysis of 14 complete mitochondrial genomes from current and museum specimens, as well as mitochondrial and nuclear SNP markers in 175 animals, suggests that the observed low genetic diversity in today's population preceded the Devil Facial Tumor Disease disease outbreak by at least 100 y. Using a genetically characterized breeding stock based on the genome sequence will enable preservation of the extant genetic diversity in future Tasmanian devil populations.
Adjacent visual representations of self-motion in different reference frames
Authors: Arnoldussen David Mattijs , Goossens Jeroen , van den Berg Albert V.
Published: June 2011

Recent investigations indicate that retinal motion is not directly available for perception when moving around [Souman JL, et al. (2010)
J Vis
10:14], possibly pointing to suppression of retinal speed sensitivity in motion areas. Here, we investigated the distribution of retinocentric and head-centric representations of self-rotation in human lower-tier visual motion areas. Functional MRI responses were measured to a set of visual self-motion stimuli with different levels of simulated gaze and simulated head rotation. A parametric generalized linear model analysis of the blood oxygen level-dependent responses revealed subregions of accessory V3 area, V6
+
area, middle temporal area, and medial superior temporal area that were specifically modulated by the speed of the rotational flow relative to the eye and head. Pursuit signals, which link the two reference frames, were also identified in these areas. To our knowledge, these results are the first demonstration of multiple visual representations of self-motion in these areas. The existence of such adjacent representations points to early transformations of the reference frame for visual self-motion signals and a topography by visual reference frame in lower-order motion-sensitive areas. This suggests that visual decisions for action and perception may take into account retinal and head-centric motion signals according to task requirements.
PW1
gene/paternally expressed gene 3 (PW1/Peg3) identifies multiple adult stem and progenitor cell populations
Authors: Besson Vanessa , Smeriglio Piera , Wegener Amélie , Relaix Frédéric , Nait Oumesmar Brahim , Sassoon David A. , Marazzi Giovanna
Published: June 2011

A variety of markers are invaluable for identifying and purifying stem/progenitor cells. Here we report the generation of a murine reporter line driven by
Pw1
that reveals cycling and quiescent progenitor/stem cells in all adult tissues thus far examined, including the intestine, blood, testis, central nervous system, bone, skeletal muscle, and skin. Neurospheres generated from the adult PW1-reporter mouse show near 100% reporter-gene expression following a single passage. Furthermore, epidermal stem cells can be purified solely on the basis of reporter-gene expression. These cells are clonogenic, repopulate the epidermal stem-cell niches, and give rise to new hair follicles. Finally, we demonstrate that only PW1 reporter-expressing epidermal cells give rise to follicles that are capable of self-renewal following injury. Our data demonstrate that PW1 serves as an invaluable marker for competent self-renewing stem cells in a wide array of adult tissues, and the PW1-reporter mouse serves as a tool for rapid stem cell isolation and characterization.
Mycosporine-like amino acids are multifunctional molecules in sea hares and their marine community
Authors: Kicklighter Cynthia E. , Kamio Michiya , Nguyen Linh , Germann Markus W. , Derby Charles D.
Published: June 2011

Molecules of keystone significance are relatively rare, yet mediate a variety of interactions between organisms. They influence the distribution and abundance of species, the transfer of energy across multiple trophic levels, and thus they play significant roles in structuring ecosystems. Despite their potential importance in facilitating our understanding of ecological systems, only three molecules thus far have been proposed as molecules of keystone significance: saxitoxin and dimethyl sulfide in marine communities and tetrodotoxin in riparian communities. In the course of studying the neuroecology of chemical defenses, we identified three mycosporine-like amino acids (MAAs)—
N
-ethanol palythine (= asterina-330),
N
-isopropanol palythine (= aplysiapalythine A), and
N
-ethyl palythine (= aplysiapalythine B)—as intraspecific alarm cues for sea hares (
Aplysia californica
). These alarm cues are released in the ink secretion of sea hares and cause avoidance behaviors in neighboring conspecifics. Further, we show that these three bioactive MAAs, two [aplysiapalythine A (APA) and -B (APB)] being previously unknown molecules, are present in the algal diet of sea hares and are concentrated in their defensive secretion as well as in their skin. MAAs are known to be produced by algae, fungi, and cyanobacteria and are acquired by many aquatic animals through trophic interactions. MAAs are widely used as sunscreens, among other uses, but sea hares modify their function to serve a previously undocumented role, as intraspecific chemical cues. Our findings highlight the multifunctionality of MAAs and their role in ecological connectivity, suggesting that they may function as molecules of keystone significance in marine ecosystems.
RefilinB (FAM101B) targets FilaminA to organize perinuclear actin networks and regulates nuclear shape
Authors: Gay Olivia , Gilquin Benoît , Nakamura Fumihiko , Jenkins Zandra A. , McCartney Rosannah , Krakow Deborah , Deshiere Alexandre , Assard Nicole , Hartwig John H. , Robertson Stephen P. , Baudier Jacques
Published: June 2011

The intracellular localization and shape of the nucleus plays a central role in cellular and developmental processes. In fibroblasts, nuclear movement and shape are controlled by a specific perinuclear actin network made of contractile actin filament bundles called transmembrane actin-associated nuclear (TAN) lines that form a structure called the actin cap. The identification of regulatory proteins associated with this specific actin cytoskeletal dynamic is a priority for understanding actin-based changes in nuclear shape and position in normal and pathological situations. Here, we first identify a unique family of actin regulators, the refilin proteins (RefilinA and RefilinB), that stabilize specifically perinuclear actin filament bundles. We next identify the actin-binding filamin A (FLNA) protein as the downstream effector of refilins. Refilins act as molecular switches to convert FLNA from an actin branching protein into one that bundles. In NIH 3T3 fibroblasts, the RefilinB/FLNA complex organizes the perinuclear actin filament bundles forming the actin cap. Finally, we demonstrate that in epithelial normal murine mammary gland (NmuMG) cells, the RefilinB/FLNA complex controls formation of a new perinuclear actin network that accompanies nuclear shape changes during the epithelial–mesenchymal transition (EMT). Our studies open perspectives for further functional analyses of this unique actin-based network and shed light on FLNA function during development and in human syndromes associated with
FLNA
mutations.
Proton transfer via a transient linear water-molecule chain in a membrane protein
Authors: Freier Erik , Wolf Steffen , Gerwert Klaus
Published: June 2011

High-resolution protein ground-state structures of proton pumps and channels have revealed internal protein-bound water molecules. Their possible active involvement in protein function has recently come into focus. An illustration of the formation of a protonated protein-bound water cluster that is actively involved in proton transfer was described for the membrane protein bacteriorhodopsin (bR) [Garczarek F, Gerwert K (2006)
Nature
439:109–112]. Here we show through a combination of time-resolved FTIR spectroscopy and molecular dynamics simulations that three protein-bound water molecules are rearranged by a protein conformational change that resulted in a transient Grotthuss-type proton-transfer chain extending through a hydrophobic protein region of bR. This transient linear water chain facilitates proton transfer at an intermediate conformation only, thereby directing proton transfer within the protein. The rearrangement of protein-bound water molecules that we describe, from inactive positions in the ground state to an active chain in an intermediate state, appears to be energetically favored relative to transient incorporation of water molecules from the bulk. Our discovery provides insight into proton-transfer mechanisms through hydrophobic core regions of ubiquitous membrane spanning proteins such as G-protein coupled receptors or cytochrome C oxidases.