bluuebunny/crossref_metadata_2025 huggingface dataset:
The Impact of Insulin Resistance and Inflammation on the Association Between Sarcopenic Obesity and Physical Functioning
Authors: Levine Morgan E. , Crimmins Eileen M.
Published: February 2012

Age associated increases in visceral adiposity and decreases in muscle mass (sarcopenia) have been shown to contribute to disability in late life. Furthermore, there is evidence that obesity‐related physiological states, such as insulin resistance and systemic inflammation, may exacerbate physical functioning problems. Both conditions have been shown to prompt hypercatabolism and impair the anabolic effect of muscles, ultimately stimulating protein breakdown and suppressing muscle synthesis. This cross‐sectional study investigates whether insulin resistance and inflammation partially account for the associations between decreased physical functioning and sarcopenic obesity. Subjects include 2,287 males and females aged 60 and older without diagnosed diabetes from the National Health and Nutrition Examination Survey (NHANES 1999–2004). Body composition measurements indicating waist circumference and appendicular skeletal muscle mass, measured by dual‐energy X‐ray absorptiometry (DXA), were used to construct four body composition categories—healthy, sarcopenic nonobese, nonsarcopenic obese, and sarcopenic obese. Physical functioning was measured using self‐reports of difficulty performing six activities. The homeostasis model assessment (IRHOMA) was used to measure insulin resistance, while inflammatory state was assessed through measurement of serum C‐reactive protein (CRP). Modified Poisson regression models were used to examine the association between physical functioning and body composition, and to evaluate whether differences in insulin resistance or inflammation partially explained this relationship. In the analysis, we controlled for possible confounders such as age, education, sex, height, and race/ethnicity. Findings suggest that physical functioning problems are increased in those with sarcopenic obesity, sarcopenic nonobesity and nonsarcopenic obesity. Furthermore, these associations may be influenced by differences in insulin resistance among different body composition phenotypes.
Employing Wiki for Knowledge Management as a Collaborative Information Repository: An NBC Universal Case
Authors: Bibbo Danielle , Michelich James , Sprehe Eric , Lee Young Eun
Published: February 2012

The Web 2.0 era is nourished by the emergence of collaboration-conducive web applications, such as blogs, social networks, and wikis. Among these, Wiki has particularly revolutionized the way information is created and shared within a wide variety of organizations, such as educational institutions, research centers, and business enterprises. The technically undemanding nature of Wiki alleviates the burden of mastering cumbersome or complicated technologies, thereby encouraging personnel to share and archive valuable tacit knowledge with other members of the organization. As a result, Wiki helps mitigate the reluctance of members to share knowledge, resolving one of the most pronounced challenges in managerial efforts to capture, transfer, and store knowledge for the firm. This case study presents the inception of a wiki by the NBC Universal Software Engineering and Delivery Team and the expansion of the wiki to other departments in the firm, in particular to Peacock Productions, which specializes in programming of documentary TV programs. The Peacock Productions case demonstrates that Wiki can be a powerful tool for managing knowledge in business corporations, which must adapt quickly to changing market demands.
Recent progress on the superconducting ion source VENUS
Authors: Benitez J. Y. , Franzen K. Y. , Hodgkinson A. , Loew T. , Lyneis C. M. , Phair L. , Saba J. , Strohmeier M. , Tarvainen O.
Published: February 2012

The 28 GHz Ion Source VENUS (versatile ECR for nuclear science) is back in operation after the superconducting sextupole leads were repaired and a fourth cryocooler was added. VENUS serves as an R&D device to explore the limits of electron cyclotron resonance source performance at 28 GHz with its 10 kW gryotron and optimum magnetic fields and as an ion source to increase the capabilities of the 88-Inch Cyclotron both for nuclear physics research and applications. The development and testing of ovens and sputtering techniques cover a wide range of applications. Recent experiments on bismuth demonstrated stable operation at 300 eμA of Bi31+, which is in the intensity range of interest for high performance heavy-ion drivers such as FRIB (Facility for Rare Isotope Beams). In addition, the space radiation effects testing program at the cyclotron relies on the production of a cocktail beam with many species produced simultaneously in the ion source and this can be done with a combination of gases, sputter probes, and an oven. These capabilities are being developed with VENUS by adding a low temperature oven, sputter probes, as well as studying the RF coupling into the source.
Laser ion source development at Holifield Radioactive Ion Beam Facility
Authors: Liu Y. , Gottwald T. , Havener C. C. , Howe J. Y. , Kiggans J. , Mattolat C. , Vane C. R. , Wendt K. , Beene J. R.
Published: February 2012

This report describes the efforts made to develop a resonant-ionization laser ion source based on tunable Ti:sapphire lasers for nuclear physics and astrophysics research at Holifield Radioactive Ion Beam Facility. Three Ti:sapphire lasers have been upgraded with individual pump lasers to eliminate laser power losses due to synchronization delays. Ionization schemes for 14 elements have been obtained. Off-line studies show that the overall efficiency of the laser ion source can be as high as 40%. TaC surface coatings have been investigated for minimizing surface and bulk trapping of the atoms of interest.
The effect of gas mixing and biased disc voltage on the preglow transient of electron cyclotron resonance ion source
Authors: Tarvainen O. , Toivanen V. , Komppula J. , Kalvas T. , Koivisto H.
Published: February 2012

The effect of gas mixing and biased disc voltage on the preglow of electron cyclotron resonance ion source plasma has been studied with the AECR-U type 14 GHz ion source. It was found that gas mixing has a significant effect on the preglow. The extracted transient beam currents and efficiency of the heavier species increase, while the currents and efficiency of the lighter species decrease when gas mixing is applied. The effect of the biased disc was found to be pronounced in continuous operation mode in comparison to preglow. The data provide information on the time scales of the plasma processes explaining the effects of gas mixing and biased disc. The results also have implications on production of radioactive ion beams in preglow mode for the proposed Beta Beam neutrino factory.
Production of rare isotope beams at the Texas A&M University Cyclotron Institute
Authors: Tabacaru G. , May D. P. , Arje J. , Chubarian G. , Clark H. , Kim G. J. , Tribble R. E.
Published: February 2012

The Cyclotron Institute at Texas A&M is currently configuring a scheme for the production of radioactive-ion beams that incorporates a light-ion guide and a heavy-ion guide coupled with an electron-cyclotron-resonance ion source constructed for charge-breeding. This scheme is part of an upgrade to the facility and is intended to produce radioactive beams suitable for injection into the K500 superconducting cyclotron. The current status of the project and details on the ion sources used in the project is presented.
1s2p resonant inelastic x-ray scattering-magnetic circular dichroism: A sensitive probe of 3d magnetic moments using hard x-ray photons
Authors: Sikora M. , Juhin A. , Simon G. , Zając M. , Biernacka K. , Kapusta Cz. , Morellon L. , Ibarra M. R. , Glatzel P.
Published: February 2012

We investigated the magnetic properties of thin magnetite and iron films grown on MgO(001) by means of hard x-ray photon-in photon-out probe, namely, 1s2p resonant inelastic x-ray scattering-magnetic circular dichroism (RIXS-MCD). A comparison of the spectra acquired from bulk and thin layer magnetite samples reveals their nearly identical shape. Hysteresis loops measured with RIXS-MCD also show a close similarity to the vibrating sample magnetometer profiles supporting the conclusion that the technique can be applied for the quantitative analysis of element and site specific magnetization in buried films containing transition metal elements. We show that Fe 1s2p RIXS-MCD is insensitive to the magnetic signal of iron impurities naturally dispersed in monocrystalline MgO substrates. The latter, combined with a unique feature of resonant inelastic x-ray scattering, namely the ability to tune incident and emitted photon (transfer) energy, allows us to separate the dichroic signal of metal layers from that of ferrite and, thus, to independently probe the magnetization of metal and oxide layers in multilayer systems.
Domain structure and magnetization loss in a toroidal core based on an Fe-based amorphous alloy
Authors: Azuma Daichi , Hasegawa Ryusuke , Saito Shin , Takahashi Migaku
Published: February 2012

By utilizing a wide-view Kerr-effect magnetic domain observation system designed for domain observation on curved surfaces, domain images were taken on the surface of a toroidal core based on an Fe-based amorphous alloy. The results of the observation are discussed in terms of Bertotti’s eddy-current loss model, helping to clarify the concept of magnetic objects proposed by the model.
Behavior of magnetic field–annealed Galfenol steel
Authors: Brooks Michael , Summers Eric , Restorff J. B. , Wun-Fogle M.
Published: February 2012

An attractive feature of the Galfenol alloy system is the ability to impart enough uniaxial anisotropy into the alloy such that no pre-load mechanism is required to attain saturation magnetostriction. Stress annealing is typically employed to generate this anisotropy. Recent published results indicate that magnetic field annealing could generate sufficient anisotropy to provide full magnetostriction with no prestress, which will suffice for the majority of applications. The magnetic field annealing apparatus used in these experiments applies a constant 1 T magnetic field at a temperature between 300 °C and 700 °C in a 7.6 cm square × 15.2-cm-long cavity. The magnetic behavior of field-annealed Galfenol is compared to stress-annealed samples. Field-annealed Galfenol rods behave differently than stress-annealed rods. While the saturation strain values are equivalent, the magnetic field required to saturate the Galfenol is much less, 60 Oe versus 200 Oe, in the field-annealed state. This behavior is also exhibited in the flux density versus field. Both curves have a significant impact on device design. The type (mechanical or magnetic) and magnitude of stored energy largely determines the optimum magnetic bias point and impacts operational efficiency.
Emergent magnetic monopoles, disorder, and avalanches in artificial kagome spin ice (invited)
Authors: Hügli R. V. , Duff G. , O’Conchuir B. , Mengotti E. , Heyderman L. J. , Rodríguez A. Fraile , Nolting F. , Braun H. B.
Published: February 2012

We study artificial spin ice with isolated elongated nanoscale islands arranged in a kagome lattice and solely interacting via long range dipolar fields. The artificial kagome spin ice displays a phenomenology similar to the microscopic pyrochlore system, where excitations at sub-Kelvin temperatures consist of emergent monopole quasiparticles that are connected via a solenoidal flux line, a classical and observable version of the Dirac string. We show that magnetization reversal in kagome spin ice is fundamentally different from the nucleation and extensive domain growth scenario expected for a generic 2D system. Here, the magnetization reverses in a strictly 1D fashion: After nucleation, a monopole-antimonopole dissociates along a 1D path, leaving a (Dirac) string of islands with reversed magnetization in its wake. Since the 2D artificial spin ice spontaneously decays into a 1D subsystem, magnetization reversal in kagome spin ice provides an example of dimensional reduction via frustration.
Nonlinear entropy transfer via zonal flows in gyrokinetic plasma turbulence
Authors: Nakata M. , Watanabe T.-H. , Sugama H.
Published: February 2012

Nonlinear entropy transfer processes in toroidal ion temperature gradient (ITG) and electron temperature gradient (ETG) driven turbulence are investigated based on the gyrokinetic entropy balance relations for zonal and non-zonal modes, which are coupled through the entropy transfer function regarded as a kinetic extension of the zonal-flow production due to the Reynolds stress. Spectral analyses of the “triad” entropy transfer function introduced in this study reveal not only the nonlinear interactions among the zonal and non-zonal modes, but also their effects on the turbulent transport level. Different types of the entropy transfer processes between the ITG and ETG turbulence are found: the entropy transfer from non-zonal to zonal modes is substantial in the saturation phase of the ITG instability, while, once the strong zonal flow is generated, the entropy transfer to the zonal modes becomes quite weak in the steady turbulence state. Instead, the zonal flows mediate the entropy transfer from non-zonal modes with low radial-wavenumbers (with contribution to the heat flux) to the other non-zonal modes with higher radial-wavenumbers (but with less contribution to the heat flux) through the triad interaction. The successive entropy transfer processes to the higher radial-wavenumber modes are associated with transport regulation in the steady turbulence state. In contrast, in both the instability-saturation and steady phases of the ETG turbulence, the entropy transfer processes among low-wavenumber non-zonal modes are dominant rather than the transfer via zonal modes.
High performance ferroelectric relaxor-PbTiO3 single crystals: Status and perspective
Authors: Zhang Shujun , Li Fei
Published: February 2012

Ferroelectrics are essential components in a wide range of applications, including ultrasonic transducers, sensors, and actuators. In the single crystal form, relaxor-PbTiO3 (PT) piezoelectric materials have been extensively studied due to their ultrahigh piezoelectric and electromechanical properties. In this article, a perspective and future development of relaxor-PT crystals are given. Initially, various techniques for the growth of relaxor-PT crystals are reviewed, with crystals up to 100 mm in diameter and 200 mm in length being readily achievable using the Bridgman technique. Second, the characterizations of dielectric and electromechanical properties are surveyed. Boundary conditions, including temperature, electric field, and stress, are discussed in relation to device limitations. Third, the physical origins of the high piezoelectric properties and unique loss characteristics in relaxor-PT crystals are discussed with respect to their crystal structure, phase, engineered domain configuration, macrosymmetry, and domain size. Finally, relaxor-PT single crystals are reviewed with respect to specific applications and contrasted to conventional piezoelectric ceramics.
Formation of dodecagonal quasicrystals in two-dimensional systems of patchy particles
Authors: van der Linden Marjolein N. , Doye Jonathan P. K. , Louis Ard A.
Published: February 2012

The behaviour of two-dimensional patchy particles with five and seven regularly arranged patches is investigated by computer simulation. For higher pressures and wider patch widths, hexagonal crystals have the lowest enthalpy, whereas at lower pressures and for narrower patches, lower density crystals with five nearest neighbours that are based on the (32,4,3,4) tiling of squares and triangles become lower in enthalpy. Interestingly, in regions of parameter space near to that where the hexagonal crystals become stable, quasicrystalline structures with dodecagonal symmetry form on cooling from high temperature. These quasicrystals can be considered as tilings of squares and triangles and are probably stabilized by the large configurational entropy associated with all the different possible such tilings. The potential for experimentally realizing such structures using DNA multi-arm motifs is also discussed.
Exploring the competition between localization and delocalization of the neutral soliton defect in polyenyl chains with the orbital optimized second order opposite spin method
Authors: Kurlancheek Westin , Lochan Rohini , Lawler Keith , Head-Gordon Martin
Published: February 2012

Theory and implementation of the analytical nuclear gradient is presented for orbital optimized scaled opposite-spin perturbation theory (O2). Evaluation of the O2 analytical gradient scales with the 4th power of molecular size, like the O2 energy. Since the O2 method permits optimization of the orbitals in the presence of wavefunction-based electron correlation, it is suitable for problems where correlation effects determine the competition between localization and delocalization of an odd electron, or hole. One such problem is the description of a neutral soliton defect on an all-trans polyacetylene chain with an odd number of carbon atoms. We show that the results of the O2 method compare well to benchmark values for small polyenyl radicals. O2 is also efficient enough to be applied to longer chains where benchmark coupled cluster methods are unfeasible. For C41H43, unrestricted orbital O2 calculations yield a soliton length of about 9 carbon atoms, while other unrestricted orbital methods such as Hartree-Fock, and the B3LYP and ωB97X-D density functionals, delocalize the soliton defect over the entire chain. The O2 result is about half the width inferred experimentally.
Quasi-variational coupled cluster theory
Authors: Robinson James B. , Knowles Peter J.
Published: February 2012

We extend our previous work on the construction of new approximations of the variational coupled cluster method. By combining several linked pair functional transformations in such a way as to give appropriately balanced infinite-order contributions, in order to approximate \documentclass[12pt]{minimal}\begin{document}$\langle e^{\hat{T}^\dagger } \hat{H}e^{\hat{T}}\rangle _L$\end{document}⟨eT̂†ĤeT̂⟩L well at all orders, we formulate a new quantum chemical method, which we name quasi-variational coupled cluster. We demonstrate this method to be particularly robust in the regime of strong static electron correlation, improving significantly on our earlier approximate variational coupled cluster approach.
Pilot-scale cooling tower to evaluate corrosion, scaling, and biofouling control strategies for cooling system makeup water
Authors: Chien S. H. , Hsieh M. K. , Li H. , Monnell J. , Dzombak D. , Vidic R.
Published: February 2012

Pilot-scale cooling towers can be used to evaluate corrosion, scaling, and biofouling control strategies when using particular cooling system makeup water and particular operating conditions. To study the potential for using a number of different impaired waters as makeup water, a pilot-scale system capable of generating 27 000 kJ/h heat load and maintaining recirculating water flow with a Reynolds number of 1.92 × 104 was designed to study these critical processes under conditions that are similar to full-scale systems. The pilot-scale cooling tower was equipped with an automatic makeup water control system, automatic blowdown control system, semi-automatic biocide feeding system, and corrosion, scaling, and biofouling monitoring systems. Observed operational data revealed that the major operating parameters, including temperature change (6.6 °C), cycles of concentration (N = 4.6), water flow velocity (0.66 m/s), and air mass velocity (3660 kg/h m2), were controlled quite well for an extended period of time (up to 2 months). Overall, the performance of the pilot-scale cooling towers using treated municipal wastewater was shown to be suitable to study critical processes (corrosion, scaling, biofouling) and evaluate cooling water management strategies for makeup waters of complex quality.
Effects of magnetic shear on magneto-Rayleigh-Taylor instability
Authors: Zhang Peng , Lau Y. Y. , Rittersdorf I. M. , Weis M. R. , Gilgenbach R. M. , Chalenski D. , Slutz S. A.
Published: February 2012

The magnetized liner inertial fusion concept [S. A. Slutz et al., Phys. Plasmas 17, 056303 (2010)] consists of a cylindrical metal liner enclosing a preheated plasma that is embedded in an axial magnetic field. Because of its diffusion into the liner, the pulsed azimuthal magnetic field may exhibit a strong magnetic shear within the liner, offering the interesting possibility of shear stabilization of the magneto-Rayleigh-Taylor (MRT) instability. Here, we use the ideal MHD model to study this effect of magnetic shear in a finite slab. It is found that magnetic shear reduces the MRT growth rate in general. The feedthrough factor is virtually independent of magnetic shear. In the limit of infinite magnetic shear, all MRT modes are stable if bu > 1, where bu is the ratio of the perturbed magnetic tension in the liner’s interior region to the acceleration during implosion.
Magneto-resistance of organic spin valves due to spin-polarized tunnel injection and extraction of charge carriers
Authors: Goswami A. , Yunus M. , Ruden P. P. , Smith D. L.
Published: February 2012

Spin-polarized tunnel injection and extraction of charge carriers can give rise to magneto-resistance in organic spin valves. To describe this magneto-resistance, the tunneling process is modeled as a transfer of electrons through a thin insulating layer between a ferromagnetic contact and an organic semiconductor. Transition rates between extended states in the metal and model “molecular” orbitals localized at the semiconductor/insulator interface are calculated based on a transfer Hamiltonian. The transition rates are then used in a rate equation model to calculate the injected current for the two spin types and the associated magneto-resistance of organic spin valves. Consistent with experimental data, it is found that the magneto-resistance can be of either sign and its magnitude strongly decreases with the applied bias.
The electronic spectrum of the C
s-C11H3 radical
Authors: Zhao Dongfeng , Linnartz Harold , Ubachs Wim
Published: February 2012

The electronic gas-phase absorption spectrum of the bent carbon-chain radical, HC4CHC6H with Cs symmetry, is recorded in the 595 nm region by cavity ring-down spectroscopy through an expanding hydrogen plasma. An unambiguous spectroscopic identification becomes possible from a systematic deuterium labeling experiment. A comparison of the results with recently reported spectra of the nonlinear HC4CHC4H and HC4C(C2H)C4H radicals with C2v symmetry provides a more comprehensive understanding of the molecular behavior of π-conjugated bent carbon-chain systems upon electronic excitation. We find that the electronic excitation in the bent carbon-chain HC4CHC2nH (n = 1–4) series exhibits a similar trend as in the linear HC2n+1H (n = 3–6) series, shifting optical absorptions towards longer wavelengths for increasing overall bent chain lengths. The π-conjugation in bent HC4CHC2nH (n = 1–4) chains is found to be generally smaller than in the linear HC2n+1H (n = 3–6) case for equivalent numbers of C-atoms. The addition of an electron-donating group to the bent chain causes a slight decrease of the effective conjugation.
Thermocapillary motion of a slender viscous droplet in a channel
Authors: Katz E. , Haj M. , Leshansky A. M. , Nepomnyashchy A.
Published: February 2012

We extend the previously developed low-capillary-number asymptotic theory of thermocapillary motion of a long bubble and a moderately viscous droplet in a channel [S. K. Wilson, “The effect of an axial temperature gradient on the steady motion of a large droplet in a tube,” J. Eng. Math. 29, 205 (1995)10.1007/BF00042854; A. Mazouchi and G. M. Homsy, “Thermocapillary migration of long bubbles in cylindrical capillary tubes,” Phys. Fluids 12, 542 (2000)10.1063/1.870260] toward droplets with an arbitrary viscosity. A generalized modified Landau-Levich-Bretherton equation, governing the thickness of the carrier liquid film entrained between the droplet and the channel wall in the transition region between constant thickness film and constant curvature cap, is solved numerically. The resulting droplet velocity is determined applying the mass balance and it is a function of two dimensionless parameters, the modified capillary number, Δσ*, equal to the surface tension variance over a distance of channel half-width scaled with the mean surface tension, and the inner-to-outer liquid viscosity ratio, λ. It is found that the droplet speed decreases with the increase in droplet viscosity, as expected, while this retardation becomes more operative upon the increase in Δσ*.
Four-mode plasmonic structure based on a prism-grating anticrossing bandgap
Authors: Chuliá-Jordán R. , Santamaría-Pérez D.
Published: February 2012

We have developed a plasmonic structure based on an anticrossing bandgap prism-grating coupling technique. We observe that up to four surface plasmons can be excited simultaneously in this plasmonic structure. Initial experiments confirm that such a plasmonic structure can improve sensor performance by tuning the amplitude of the grating. From numerical simulations, we conclude that plasmon modes with equal propagation constants at a different wavelength can only be excited at different grating amplitudes of our plasmonic structure, in such a way that the increase of wavelength implies the increase of the amplitude for a fixed propagation constant.
Spontaneous induction of the uniform lying helix alignment in bimesogenic liquid crystals for the flexoelectro-optic effect
Authors: Gardiner Damian J. , Morris Stephen M. , Hands Philip J. W. , Castles Flynn , Qasim Malik M. , Kim Wook-Sung , Seok Choi Su , Wilkinson Timothy D. , Coles Harry J.
Published: February 2012

Using in-plane electric fields, the electrical induction of the uniform lying helix (ULH) alignment in chiral nematic liquid crystals is reported. This process permits spontaneous induction of the ULH alignment to give an in-plane optic axis, without the need for complex processing. Flexoelectro-optic switching is subsequently obtained by holding the in-plane electrodes at a common voltage and addressing via a third, plane-parallel electrode on a second, or upper, substrate to give a field across the device in the viewing direction. For this device, in optimized bimesogenic materials, we demonstrate full intensity modulation and sub-millisecond response times at typical device temperatures.
Metal contact to graphene nanoribbon
Authors: Seol Gyungseon , Guo Jing
Published: February 2012

Metal to graphene nanoribbon (GNR) contact is explored by self-consistent numerical simulations. The Schottky barrier height of the GNR contact can be modulated by either the gate voltage or the workfunction of the metal contact. An Ohmic contact with multiple-subband injection can be achieved with increase of the GNR width. The contact resistance normalized by the GNR width is smaller than that of the two-dimensional graphene, and the effect of the quasi-one-dimensional subbands for GNRs is manifested when the GNR is narrower than about 5 nm.
Suppression of photoconductivity by magnetic field in epitaxial manganite thin films
Authors: Guo E. J. , Wang L. , Lu H. B. , Guo H. Z. , He M. , Jin K. J. , Yang G. Z. , Gao J.
Published: February 2012

The erasure of photoinduced resistance (PR) by the magnetic field was investigated in manganite films. The PR was significantly suppressed when a magnetic field was introduced at low temperature. The decrease (or increase) of PR with increment of magnetic field was observed in ferromagnetic (or paramagnetic) phases of films, respectively. Our results are suggested to be the coaction of two effects under magnetic fields: (i) the reorientation of domains and spin directions of photoexcited carriers and (ii) electrons trapped around oxygen vacancies released and recombined with majority carriers in films. The interplay of the external fields is a good demonstration of the strong coupling between spins and charges in colossal magnetoresistance materials.
The weak π − π interaction originated resonant tunneling and fast switching in the carbon based electronic devices
Authors: He Jun , Chen Ke-Qiu , Sun Chang Q.
Published: February 2012

By means of the nonequilibrium Green's functions and the density functional theory, we have investigated the electronic transport properties of C60 based electronic device with different intermolecular interactions. It is found that the electronic transport properties vary with the types of the interaction between two C60 molecules. A fast electrical switching behavior based on negative differential resistance has been found when two molecules are coupled by the weak π − π interaction. Compared to the solid bonding, the weak interaction is found to induce resonant tunneling, which is responsible for the fast response to the applied electric field and hence the velocity of switching.
Dominant eukaryotic export production during ocean anoxic events reflects the importance of recycled NH
4
+
Authors: Higgins Meytal B. , Robinson Rebecca S. , Husson Jonathan M. , Carter Susan J. , Pearson Ann
Published: February 2012

The Mesozoic is marked by several widespread occurrences of intense organic matter burial. Sediments from the largest of these events, the Cenomanian–Turonian Oceanic Anoxic Event (OAE 2) are characterized by lower nitrogen isotope ratios than are seen in modern marine settings. It has remained a challenge to describe a nitrogen cycle that could achieve such isotopic depletion. Here we use nitrogen-isotope ratios of porphyrins to show that eukaryotes contributed the quantitative majority of export production throughout OAE 2, whereas cyanobacteria contributed on average approximately 20%. Such data require that any explanation for the OAE nitrogen cycle and its isotopic values be consistent with a eukaryote-dominated ecosystem. Our results agree with models that suggest the OAEs were high-productivity events, supported by vigorous upwelling. Upwelling of anoxic deep waters would have supplied reduced N species (i.e.,

) to primary producers. We propose that new production during OAE 2 primarily was driven by direct

-assimilation supplemented by diazotrophy, whereas chemocline denitrification and anammox quantitatively consumed

and

. A marine nitrogen reservoir dominated by

, in combination with known kinetic isotope effects, could lead to eukaryotic biomass depleted in
15
N.
Transcription factor LIM homeobox 7 (Lhx7) maintains subtype identity of cholinergic interneurons in the mammalian striatum
Authors: Lopes Rita , Verhey van Wijk Nicole , Neves Guilherme , Pachnis Vassilis
Published: February 2012

The generation and maintenance of a plethora of neuronal subtypes is essential for normal brain function. Nevertheless, little is known about the molecular mechanisms that maintain the defining characteristics of neurons following their initial postmitotic specification. Using conditional gene ablation in mice, we demonstrate here that the homeodomain protein LIM homeobox (Lhx)7 is essential for maintaining the morphological and molecular characteristics of cholinergic interneurons of the striatum. Lhx7-depleted cholinergic interneurons extinguish expression of several subtype-specific markers, including choline acetyl transferase and Isl1, and are respecified into Lhx6-expressing mature GABAergic interneurons. Additional expression studies support a model where Lhx7 controls the choice between cholinergic or GABAergic identity by gating a cross inhibitory regulation between Isl1 and Lhx6. By demonstrating that the switch between alternative striatal interneuron fates depends on persistent activity of a single transcription factor, we provide evidence that the intrinsic plasticity of mammalian forebrain neuronal subtypes is maintained after the initial specification and lineage commitment and possibly throughout life.
Essential requirement for β-arrestin2 in mouse intestinal tumors with elevated Wnt signaling
Authors: Bonnans Caroline , Flacelière Maud , Grillet Fanny , Dantec Christelle , Desvignes Jean-Pierre , Pannequin Julie , Severac Dany , Dubois Emeric , Bibeau Frédéric , Escriou Virginie , Crespy Philippe , Journot Laurent , Hollande Frédéric , Joubert Dominique
Published: February 2012

β-Arrestins (Arrb) participate in the regulation of multiple signaling pathways, including Wnt/β-catenin, the major actor in human colorectal cancer initiation. To better understand the roles of Arrb in intestinal tumorigenesis, a reverse genetic approach (
Arrb
−/−
) and in vivo siRNA treatment were used in
Apc
Δ14/+
mice. Mice with Arrb2 depletion (knockout and siRNA) developed only 33% of the tumors detected in their
Arrb2
-WT littermates, whereas Arrb1 depletion remained without significant effect. These remaining tumors grow normally and are essentially Arrb2–independent. Unsupervised hierarchical clustering analysis showed that they clustered with 25% of
Apc
Δ14/+
;Arrb
2
+/+
tumors. Genes overexpressed in this subset reflect a high interaction with the immune system, whereas those overexpressed in Arrb2–dependent tumors are predominantly involved in Wnt signaling, cell adhesion, migration, and extracellular matrix remodeling. The involvement of Arrb2 in intestinal tumor development via the regulation of the Wnt pathway is supported by ex vivo and in vitro experiments using either tumors from
Apc
Δ14/+
mice or murine
Apc
Min/+
cells. Indeed, Arrb2 siRNAs decreased the expression of Wnt target genes in cells isolated from 12 of 18 tumors from
Apc
Δ14/+
mice. In
Apc
Min/+
cells, Arrb2 siRNAs completely reversed the increased Wnt activity and colony formation in soft agar induced by Apc siRNA treatment, whereas they did not affect these parameters in basal conditions or in cells expressing constitutively active β-catenin. We demonstrate that Arrb2 is essential for the initiation and growth of intestinal tumors displaying elevated Wnt pathway activity and identify a previously unsuspected molecular heterogeneity among tumors induced by truncating
Apc
mutations.
Aberration-free three-dimensional multiphoton imaging of neuronal activity at kHz rates
Authors: Botcherby Edward J. , Smith Christopher W. , Kohl Michael M. , Débarre Delphine , Booth Martin J. , Juškaitis Rimas , Paulsen Ole , Wilson Tony
Published: February 2012

Multiphoton microscopy is a powerful tool in neuroscience, promising to deliver important data on the spatiotemporal activity within individual neurons as well as in networks of neurons. A major limitation of current technologies is the relatively slow scan rates along the
z
direction compared to the kHz rates obtainable in the
x
and
y
directions. Here, we describe a custom-built microscope system based on an architecture that allows kHz scan rates over hundreds of microns in all three dimensions without introducing aberration. We further demonstrate how this high-speed 3D multiphoton imaging system can be used to study neuronal activity at millisecond resolution at the subcellular as well as the population level.
The heterogeneous motility of the Lyme disease spirochete in gelatin mimics dissemination through tissue
Authors: Harman Michael W. , Dunham-Ems Star M. , Caimano Melissa J. , Belperron Alexia A. , Bockenstedt Linda K. , Fu Henry C. , Radolf Justin D. , Wolgemuth Charles W.
Published: February 2012

The Lyme disease spirochete
Borrelia burgdorferi
exists in nature in an enzootic cycle that involves the arthropod vector
Ixodes scapularis
and mammalian reservoirs. To disseminate within and between these hosts, spirochetes must migrate through complex, polymeric environments such as the basement membrane of the tick midgut and the dermis of the mammal. To date, most research on the motility of
B. burgdorferi
has been done in media that do not resemble the tissue milieus that
B. burgdorferi
encounter in vivo. Here we show that the motility of
Borrelia
in gelatin matrices in vitro resembles the pathogen's movements in the chronically infected mouse dermis imaged by intravital microscopy. More specifically,
B. burgdorferi
motility in mouse dermis and gelatin is heterogeneous, with the bacteria transitioning between at least three different motility states that depend on transient adhesions to the matrix. We also show that
B. burgdorferi
is able to penetrate matrices with pore sizes much smaller than the diameter of the bacterium. We find a complex relationship between the swimming behavior of
B. burgdorferi
and the rheological properties of the gelatin, which cannot be accounted for by recent theoretical predictions for microorganism swimming in gels. Our results also emphasize the importance of considering borrelial adhesion as a dynamic rather than a static process.
Sweet taste receptor signaling in beta cells mediates fructose-induced potentiation of glucose-stimulated insulin secretion
Authors: Kyriazis George A. , Soundarapandian Mangala M. , Tyrberg Björn
Published: February 2012

Postprandial insulin release is regulated by glucose, but other circulating nutrients may target beta cells and potentiate glucose-stimulated insulin secretion via distinct signaling pathways. We demonstrate that fructose activates sweet taste receptors (TRs) on beta cells and synergizes with glucose to amplify insulin release in human and mouse islets. Genetic ablation of the sweet TR protein T1R2 obliterates fructose-induced insulin release and its potentiating effects on glucose-stimulated insulin secretion in vitro and in vivo. TR signaling in beta cells is triggered, at least in part, in parallel with the glucose metabolic pathway and leads to increases in intracellular calcium that are dependent on the activation of phospholipase C (PLC) and transient receptor potential cation channel, subfamily M, member 5 (TRPM5). Our results unveil a pathway for the regulation of insulin release by postprandial nutrients that involves beta cell sweet TR signaling.
The molecular basis for selective inhibition of unconventional mRNA splicing by an IRE1-binding small molecule
Authors: Cross Benedict C. S. , Bond Peter J. , Sadowski Pawel G. , Jha Babal Kant , Zak Jaroslav , Goodman Jonathan M. , Silverman Robert H. , Neubert Thomas A. , Baxendale Ian R. , Ron David , Harding Heather P.
Published: February 2012

IRE1 couples endoplasmic reticulum unfolded protein load to RNA cleavage events that culminate in the sequence-specific splicing of the
Xbp1
mRNA and in the regulated degradation of diverse membrane-bound mRNAs. We report on the identification of a small molecule inhibitor that attains its selectivity by forming an unusually stable Schiff base with lysine 907 in the IRE1 endonuclease domain, explained by solvent inaccessibility of the imine bond in the enzyme-inhibitor complex. The inhibitor (abbreviated 4μ8C) blocks substrate access to the active site of IRE1 and selectively inactivates both
Xbp1
splicing and IRE1-mediated mRNA degradation. Surprisingly, inhibition of IRE1 endonuclease activity does not sensitize cells to the consequences of acute endoplasmic reticulum stress, but rather interferes with the expansion of secretory capacity. Thus, the chemical reactivity and sterics of a unique residue in the endonuclease active site of IRE1 can be exploited by selective inhibitors to interfere with protein secretion in pathological settings.
Plasmacytoid dendritic cells control T-cell response to chronic viral infection
Authors: Cervantes-Barragan Luisa , Lewis Kanako L. , Firner Sonja , Thiel Volker , Hugues Stephanie , Reith Walter , Ludewig Burkhard , Reizis Boris
Published: February 2012

Infections with persistent viruses are a frequent cause of immunosuppression, autoimmune sequelae, and/or neoplastic disease. Plasmacytoid dendritic cells (pDCs) are innate immune cells that produce type I interferon (IFN-I) and other cytokines in response to virus-derived nucleic acids. Persistent viruses often cause depletion or functional impairment of pDCs, but the role of pDCs in the control of these viruses remains unclear. We used conditional targeting of pDC-specific transcription factor E2-2 to generate mice that constitutively lack pDCs in peripheral lymphoid organs and tissues. The profound impact of pDC deficiency on innate antiviral responses was revealed by the failure to control acute infection with the cytopathic mouse hepatitis virus. Furthermore, pDC-deficient animals failed to clear lymphocytic choriomeningitis virus (LCMV) from hematopoietic organs during persistent LCMV infection. This failure was associated with reduced numbers and functionality of LCMV-specific CD4+helper T cells and impaired antiviral CD8+T-cell responses. Adoptive transfer of LCMV-specific T cells revealed that both CD4+and CD8+T cells required IFN-I for expansion, but only CD4+T cells required the presence of pDCs. In contrast, mice with pDC-specific loss of MHC class II expression supported normal CD4+T-cell response to LCMV. These data suggest that pDCs facilitate CD4+helper T-cell responses to persistent viruses independently of direct antigen presentation. Thus pDCs provide an essential link between innate and adaptive immunity to chronic viral infection, likely through the secretion of IFN-I and other cytokines.
Wing stridulation in a Jurassic katydid (Insecta, Orthoptera) produced low-pitched musical calls to attract females
Authors: Gu Jun-Jie , Montealegre-Z Fernando , Robert Daniel , Engel Michael S. , Qiao Ge-Xia , Ren Dong
Published: February 2012

Behaviors are challenging to reconstruct for extinct species, particularly the nature and origins of acoustic communication. Here we unravel the song ofArchaboilus musicusGu, Engel and Ren sp. nov., a 165 million year old stridulating katydid. From the exceptionally preserved morphology of its stridulatory apparatus in the forewings and phylogenetic comparison with extant species, we reveal thatA. musicusradiated pure-tone (musical) songs using a resonant mechanism tuned at a frequency of 6.4 kHz. Contrary to previous scenarios, musical songs were an early innovation, preceding the broad-bandwidth songs of extant katydids. Providing an accurate insight into paleoacoustic ecology, the low-frequency musical song ofA. musicuswas well-adapted to communication in the lightly cluttered environment of the mid-Jurassic forest produced by coniferous trees and giant ferns, suggesting that reptilian, amphibian, and mammalian insectivores could have also heardA. musicus' song.
On relaxations and aging of various glasses
Authors: Amir Ariel , Oreg Yuval , Imry Yoseph
Published: February 2012

Slow relaxation occurs in many physical and biological systems. “Creep” is an example from everyday life. When stretching a rubber band, for example, the recovery to its equilibrium length is not, as one might think, exponential: The relaxation is slow, in many cases logarithmic, and can still be observed after many hours. The form of the relaxation also depends on the duration of the stretching, the “waiting time.” This ubiquitous phenomenon is called aging, and is abundant both in natural and technological applications. Here, we suggest a general mechanism for slow relaxations and aging, which predicts logarithmic relaxations, and a particular aging dependence on the waiting time. We demonstrate the generality of the approach by comparing our predictions to experimental data on a diverse range of physical phenomena, from conductance in granular metals to disordered insulators and dirty semiconductors, to the low temperature dielectric properties of glasses.
IL-38 binds to the IL-36 receptor and has biological effects on immune cells similar to IL-36 receptor antagonist
Authors: van de Veerdonk Frank L. , Stoeckman Angela K. , Wu Gouping , Boeckermann Aaron N. , Azam Tania , Netea Mihai G. , Joosten Leo A. B. , van der Meer Jos W. M. , Hao Ruyi , Kalabokis Vassili , Dinarello Charles A.
Published: February 2012

The functional role of IL-1 family member 10, recently renamed IL-38, remains unknown. In the present study we aimed to elucidate the biological function of IL-38 and to identify its receptor. Heat-killed
Candida albicans
was used to stimulate memory T-lymphocyte cytokine production in freshly obtained human peripheral blood mononuclear cells from healthy subjects. The addition of recombinant IL-38 (152 amino acids) inhibited the production of T-cell cytokines IL-22 (37% decrease) and IL-17 (39% decrease). The reduction in IL-22 and IL-17 caused by IL-38 was similar to that caused by the naturally occurring IL-36 receptor antagonist (IL-36Ra) in the same peripheral blood mononuclear cells cultures. IL-8 production induced by IL-36γ was reduced by IL-38 (42% decrease) and also was reduced by IL-36Ra (73% decrease). When human blood monocyte-derived dendritic cells were used, IL-38 as well as IL-36Ra increased LPS-induced IL-6 by twofold. We screened immobilized extracellular domains of each member of the IL-1 receptor family, including the IL-36 receptor (also known as “IL-1 receptor-related protein 2”) and observed that IL-38 bound only to the IL-36 receptor, as did IL-36Ra. The dose–response suppression of IL-38 as well as that of IL-36Ra of
Candida
-induced IL-22 and IL-17 was not that of the classic IL-1 receptor antagonist (anakinra), because low concentrations were optimal for inhibiting IL-22 production, whereas higher concentrations modestly increased IL-22. These data provide evidence that IL-38 binds to the IL-36R, as does IL-36Ra, and that IL-38 and IL-36Ra have similar biological effects on immune cells by engaging the IL-36 receptor.
Congenital diaphragmatic hernia candidate genes derived from embryonic transcriptomes
Authors: Russell Meaghan K. , Longoni Mauro , Wells Julie , Maalouf Faouzi I. , Tracy Adam A. , Loscertales Maria , Ackerman Kate G. , Pober Barbara R. , Lage Kasper , Bult Carol J. , Donahoe Patricia K.
Published: February 2012

Congenital diaphragmatic hernia (CDH) is a common (1 in 3,000 live births) major congenital malformation that results in significant morbidity and mortality. The discovery of CDH loci using standard genetic approaches has been hindered by its genetic heterogeneity. We hypothesized that gene expression profiling of developing embryonic diaphragms would help identify genes likely to be associated with diaphragm defects. We generated a time series of whole-transcriptome expression profiles from laser captured embryonic mouse diaphragms at embryonic day (E)11.5 and E12.5 when experimental perturbations lead to CDH phenotypes, and E16.5 when the diaphragm is fully formed. Gene sets defining biologically relevant pathways and temporal expression trends were identified by using a series of bioinformatic algorithms. These developmental sets were then compared with a manually curated list of genes previously shown to cause diaphragm defects in humans and in mouse models. Our integrative filtering strategy identified 27 candidates for CDH. We examined the diaphragms of knockout mice for one of the candidate genes, pre–B-cell leukemia transcription factor 1 (Pbx1), and identified a range of previously undetected diaphragmatic defects. Our study demonstrates the utility of genetic characterization of normal development as an integral part of a disease gene identification and prioritization strategy for CDH, an approach that can be extended to other diseases and developmental anomalies.