bluuebunny/crossref_metadata_2025 huggingface dataset:
Enhanced reaction rates in NDP analysis with neutron scattering
Authors: Downing R. Gregory
Published: April 2014

Neutron depth profiling (NDP) makes accessible quantitative information on a few isotopic concentration profiles ranging from the surface into the sample a few micrometers. Because the candidate analytes for NDP are few, there is little interference encountered. Furthermore, neutrons have no charge so mixed chemical states in the sample are of no direct concern. There are a few nuclides that exhibit large probabilities for neutron scattering. The effect of neutron scattering on NDP measurements has not previously been evaluated as a basis for either enhancing the reaction rates or as a source of measurement error. Hydrogen is a common element exhibiting large neutron scattering probability found in or around sample volumes being analyzed by NDP. A systematic study was conducted to determine the degree of signal change when neutron scattering occurs during analysis. The relative signal perturbation was evaluated for materials of varied neutron scattering probability, concentration, total mass, and geometry. Signal enhancements up to 50% are observed when the hydrogen density is high and in close proximity to the region of analysis with neutron beams of sub thermal energies. Greater signal enhancements for the same neutron number density are reported for thermal neutron beams. Even adhesive tape used to position the sample produces a measureable signal enhancement. Because of the shallow volume, negligible distortion of the NDP measured profile shape is encountered from neutron scattering.
Dynamics of coarsening in multicomponent lipid vesicles with non-uniform mechanical properties
Authors: Funkhouser Chloe M. , Solis Francisco J. , Thornton K.
Published: April 2014

Multicomponent lipid vesicles are commonly used as a model system for the complex plasma membrane. One phenomenon that is studied using such model systems is phase separation. Vesicles composed of simple lipid mixtures can phase-separate into liquid-ordered and liquid-disordered phases, and since these phases can have different mechanical properties, this separation can lead to changes in the shape of the vesicle. In this work, we investigate the dynamics of phase separation in multicomponent lipid vesicles, using a model that couples composition to mechanical properties such as bending rigidity and spontaneous curvature. The model allows the vesicle surface to deform while conserving surface area and composition. For vesicles initialized as spheres, we study the effects of phase fraction and spontaneous curvature. We additionally initialize two systems with elongated, spheroidal shapes. Dynamic behavior is contrasted in systems where only one phase has a spontaneous curvature similar to the overall vesicle surface curvature and systems where the spontaneous curvatures of both phases are similar to the overall curvature. The bending energy contribution is typically found to slow the dynamics by stabilizing configurations with multiple domains. Such multiple-domain configurations are found more often in vesicles with spheroidal shapes than in nearly spherical vesicles.
The hydrophobic effect in a simple isotropic water-like model: Monte Carlo study
Authors: Huš Matej , Urbic Tomaz
Published: April 2014

Using Monte Carlo computer simulations, we show that a simple isotropic water-like model with two characteristic lengths can reproduce the hydrophobic effect and the solvation properties of small and large non-polar solutes. Influence of temperature, pressure, and solute size on the thermodynamic properties of apolar solute solvation in a water model was systematically studied, showing two different solvation regimes. Small particles can fit into the cavities around the solvent particles, inducing additional order in the system and lowering the overall entropy. Large particles force the solvent to disrupt their network, increasing the entropy of the system. At low temperatures, the ordering effect of small solutes is very pronounced. Above the cross-over temperature, which strongly depends on the solute size, the entropy change becomes strictly positive. Pressure dependence was also investigated, showing a “cross-over pressure” where the entropy and enthalpy of solvation are the lowest. These results suggest two fundamentally different solvation mechanisms, as observed experimentally in water and computationally in various water-like models.
Magnetic scanning gate microscopy of graphene Hall devices (invited)
Authors: Rajkumar R. K. , Asenjo A. , Panchal V. , Manzin A. , Iglesias-Freire Ó. , Kazakova O.
Published: April 2014

We have performed sensitivity mapping of graphene Hall devices with the width of 0.6–15 μm operating in the diffusive regime under non-uniform, local magnetic and electric fields induced by a scanning metallic magnetic probe. The transverse voltage was recorded, while tuning the magnitude and orientation of the bias current, the probe-sample distance, and orientation of the probe magnetization. A strong two-fold symmetry pattern has been observed, as a consequence of capacitive coupling between the probe and the sample. The effect is particularly pronounced in small devices (<1 μm), where the dominating electric field contribution significantly lowers the effective area of the magnetic sensor. We show that implementation of the Kelvin probe feedback loop in the standard scanning gate microscopy setup drastically reduces parasitic electric field effects and improves magnetic sensitivity.
Second-order perturbative corrections to the restricted active space configuration interaction with the hole and particle approach
Authors: Casanova David
Published: April 2014

Second-order corrections to the restricted active space configuration interaction (RASCI) with the hole and particle truncation of the excitation operator are developed. Theoretically, the computational cost of the implemented perturbative approach, abbreviated as RASCI(2), grows like its single reference counterpart in MP2. Two different forms of RASCI(2) have been explored, that is the generalized Davidson-Kapuy and the Epstein-Nesbet partitions of the Hamiltonian. The preliminary results indicate that the use of energy level shift of a few tenths of a Hartree might systematically improve the accuracy of the RASCI(2) energies. The method has been tested in the computation of the ground state energy profiles along the dissociation of the hydrogen fluoride and N2 molecules, the computation of correlation energy in the G2/97 molecular test set, and in the computation of excitation energies to low-lying states in small organic molecules.
Cross-talk artefacts in Kelvin probe force microscopy imaging: A comprehensive study
Authors: Barbet S. , Popoff M. , Diesinger H. , Deresmes D. , Théron D. , Mélin T.
Published: April 2014

We provide in this article a comprehensive study of the role of ac cross-talk effects in Kelvin Probe Force Microscopy (KPFM), and their consequences onto KPFM imaging. The dependence of KPFM signals upon internal parameters such as the cantilever excitation frequency and the projection angle of the KPFM feedback loop is reviewed, and compared with an analytical model. We show that ac cross-talks affect the measured KPFM signals as a function of the tip-substrate distance, and thus hamper the measurement of three-dimensional KPFM signals. The influence of ac cross-talks is also demonstrated onto KPFM images, in the form of topography footprints onto KPFM images, especially in the constant distance (lift) imaging mode. Our analysis is applied to unambiguously probe charging effects in tobacco mosaic viruses (TMVs) in ambient air. TMVs are demonstrated to be electrically neutral when deposited on silicon dioxide surfaces, but inhomogeneously negatively charged when deposited on a gold surface.
Moissanite anvil cell design for giga-pascal nuclear magnetic resonance
Authors: Meier Thomas , Herzig Tobias , Haase Jürgen
Published: April 2014

A new design of a non-magnetic high-pressure anvil cell for nuclear magnetic resonance (NMR) experiments at Giga-Pascal pressures is presented, which uses a micro-coil inside the pressurized region for high-sensitivity NMR. The comparably small cell has a length of 22 mm and a diameter of 18 mm, so it can be used with most NMR magnets. The performance of the cell is demonstrated with external-force vs. internal-pressure experiments, and the cell is shown to perform well at pressures up to 23.5 GPa using 800 μm 6H-SiC large cone Boehler-type anvils. 1H, 23Na, 27Al, 69Ga, and 71Ga NMR test measurements are presented, which show a resolution of better than 4.5 ppm, and an almost maximum possible signal-to-noise ratio.
Stability of bubbly liquids and its connection to the process of cavitation inception
Authors: Fuster D. , Pham K. , Zaleski S.
Published: April 2014

This paper presents a potential energy approach for the investigation of the stability of bubbly liquids. Using the system's free energy variations with respect to the void fraction as a stability criterion for the whole system, we consider that sudden bubble expansion occurs only when the bubble cluster expansion is energetically favorable. The results obtained provide new insight into the behavior of pre-nucleated liquids when the inception point is reached as well as a simple method to estimate the energy exchanges between a bubble cluster and its environment when the kinetic energy is negligible compared to the elastic energy stored during tension and compression processes. In addition to the radius of the initial nuclei, the concentration and polydispersity are shown to exert an important influence on the response of the system after inception.
Fullerene mixtures enhance the thermal stability of a non-crystalline polymer solar cell blend
Authors: Lindqvist Camilla , Bergqvist Jonas , Bäcke Olof , Gustafsson Stefan , Wang Ergang , Olsson Eva , Inganäs Olle , Andersson Mats R. , Müller Christian
Published: April 2014

Printing of polymer:fullerene solar cells at high speed requires annealing at temperatures up to 140 °C. However, bulk-heterojunction blends that comprise a non-crystalline donor polymer often suffer from insufficient thermal stability and hence rapidly coarsen upon annealing above the glass transition temperature of the blend. In addition, micrometer-sized fullerene crystals grow, which are detrimental for the solar cell performance. In this manuscript, we present a strategy to limit fullerene crystallization, which is based on the use of fullerene mixtures of the two most common derivatives, PC61BM and PC71BM, as the acceptor material. Blends of this fullerene mixture and a non-crystalline thiophene-quinoxaline copolymer display considerably enhanced thermal stability and largely retain their photovoltaic performance upon annealing at elevated temperatures as high as 170 °C.
Modulating emission intensity of GaN-based green light emitting diodes on c-plane sapphire
Authors: Du Chunhua , Ma Ziguang , Zhou Junming , Lu Taiping , Jiang Yang , Jia Haiqiang , Liu Wuming , Chen Hong
Published: April 2014

The asymmetric dual-wavelength (green/blue) coupled InGaN/GaN multiple quantum wells were proposed to modulate the green emission intensity. Electroluminescent measurements demonstrate the conspicuous increment of the green light intensity by decreasing the coupled barrier thickness. This was partly attributed to capture of more carriers when holes tunnel across the thinner barrier from the blue quantum wells, as a hole reservoir, to the green quantum wells. While lower effective barrier height of the blue quantum wells benefits improved hole transportation from p-GaN to the active region. Efficiency droop of the green quantum wells was partially alleviated due to the enhanced injection efficiency of holes.
Communication: Determining the structure of the N2Ar van der Waals complex with laser-based channel-selected Coulomb explosion
Authors: Wu Chengyin , Wu Cong , Song Di , Su Hongmei , Xie Xiguo , Li Min , Deng Yongkai , Liu Yunquan , Gong Qihuang
Published: April 2014

We experimentally reconstructed the structure of the N2Ar van der Waals complex with the technique of laser-based channel-selected Coulomb explosion imaging. The internuclear distance between the N2 center of mass and the Ar atom, i.e., the length of the van der Waals bond, was determined to be 3.88 Å from the two-body explosion channels. The angle between the van der Waals bond and the N2 principal axis was determined to be 90° from the three-body explosion channels. The reconstructed structure was contrasted with our high level ab initio calculations. The agreement demonstrated the potential application of laser-based Coulomb explosion in imaging transient molecular structure, particularly for floppy van der Waals complexes, whose structures remain difficult to be determined by conventional spectroscopic methods.
Comparison of Sn-doped and nonstoichiometric vertical-Bridgman-grown crystals of the topological insulator Bi2Te2Se
Authors: Kushwaha S. K. , Gibson Q. D. , Xiong J. , Pletikosic I. , Weber A. P. , Fedorov A. V. , Ong N. P. , Valla T. , Cava R. J.
Published: April 2014

A comparative study of the properties of topological insulator Bi2Te2Se (BTS) crystals grown by the vertical Bridgeman method is described. Two defect mechanisms that create acceptor impurities to compensate for the native n-type carriers are compared: Bi excess, and light Sn doping. Both methods yield low carrier concentrations and an n-p crossover over the length of the grown crystal boules, but lower carrier concentrations and higher resistivities are obtained for the Sn-doped crystals, which reach carrier concentrations as low as 8 × 1014 cm−3. Further, the temperature dependent resistivities for the Sn-doped crystals display strongly activated behavior at high temperatures, with a characteristic energy of half the bulk band gap. The (001) cleaved Sn-doped BTS crystals display high quality Shubnikov de Haas (SdH) quantum oscillations due to the topological surface state electrons. Angle resolved photoelectron spectroscopy (ARPES) characterization shows that the Fermi energy (EF) for the Sn-doped crystals falls cleanly in the surface states with no interference from the bulk bands, which the Dirac point for the surface states lies approximately 60 meV below the top of the bulk valence band maximum, and allows for a determination of the bulk and surface state carrier concentrations as a function of Energy near EF. Electronic structure calculations that compare Bi excess and Sn dopants in BTS demonstrate that Sn acts as a special impurity, with a localized impurity band that acts as a charge buffer occurring inside the bulk band gap. We propose that the special resonant level character of Sn in BTS gives rise to the exceptionally low carrier concentrations and activated resistivities observed.
Ultralow-light-level all-optical transistor in rubidium vapor
Authors: Jing Jietai , Zhou Zhifan , Liu Cunjin , Qin Zhongzhong , Fang Yami , Zhou Jun , Zhang Weiping
Published: April 2014

An all-optical transistor (AOT) is a device in which one light beam can efficiently manipulate another. It is the foundational component of an all-optical communication network. An AOT that can operate at ultralow light levels is especially attractive for its potential application in the quantum information field. Here, we demonstrate an AOT driven by a weak light beam with an energy density of 2.5 × 10−5 photons/(λ2/2π) (corresponding to 6  yJ/(λ2/2π) and about 800 total photons) using the double-Λ four-wave mixing process in hot rubidium vapor. This makes it a promising candidate for ultralow-light-level optical communication and quantum information science.
Anisotropic transport property anomaly in K0.8Fe1.65Se2 crystal
Authors: Teng M. L. , Yin Y. W. , Dong S. N. , Su T. S. , Zhang M. J. , Huang W. C. , Li X. G.
Published: April 2014

The anisotropic transport properties of K0.8Fe1.65Se2 crystal have been investigated with the angle θ (between the magnetic field H and c-axis) varied from 0° to 180°. It is found that the angle dependencies of the mixed state resistivities near Tc0 show a small anomalous peak on the resistive valley for H//ab, probably due to the kinked vortex structure with a lower pinning energy in the phase-separated crystal. In the normal state, the resistivities increase with increasing angles and take a maximum at H//ab, which may be related to the larger resistivity when carriers move along the c-axis driven by Lorentz force.
Cascade luminescent solar concentrators
Authors: Flores Daorta Sthy , Proto Antonio , Fusco Roberto , Claudio Andreani Lucio , Liscidini Marco
Published: April 2014

We propose a luminescent solar concentrator (LSC) characterized by a strong enhancement of the concentration factor in which the area covered by photovoltaic cells is independent of the area over which sunlight is collected. We name this device cascade-LSC (c-LSC), as sunlight is both geometrically and spectrally concentrated by cascading absorption and emission into different LSCs. We demonstrate a prototype and measure the generated photocurrent. The results are in good agreement with those predicted by our numerical model based on Monte Carlo simulations.
Nanomaterials synthesis by a novel phenomenon: The nanoscale Rayleigh-Taylor instability
Authors: Yadavali S. , Kalyanaraman R.
Published: April 2014

The Rayleigh-Taylor (RT) interfacial instability has been attributed to physical phenomenon in a wide variety of macroscopic systems, including black holes, laser generated plasmas, and thick fluids. However, evidence for its existence in the nanoscale is lacking. Here we first show theoretically that this instability can occur in films with thickness negligible compared to the capillary length when they are heated rapidly inside a bulk fluid. Pressure gradients developed in the evaporated fluid region produce large forces causing the instability. Experiments were performed by melting Au films inside glycerol fluid by nanosecond laser pulses. The ensuing nanoparticles had highly monomodal size distributions. Importantly, the spacing of the nanoparticles was independent of the film thickness and could be tuned by the magnitude of the pressure gradients. Therefore, this instability can overcome some of the limitations of conventional thin self-organization techniques that rely on film thickness to control length scales.
Enhanced Pt performance with H2O plasma modified carbon nanofiber support
Authors: Hu Jue , Jiang Lin , Zhang Chengxu , Zhang Xiaodong , Meng Yuedong , Wang Xiangke
Published: April 2014

The insufficient durability and catalytic activity in low loading of platinum (Pt) are main obstacles to the development of low-temperature fuel cells. Our study demonstrated an efficient way to simultaneously improve the durability and electro-catalytic activity of Pt catalysts on carbon supports by water vapor (H2O) plasma functionalization. We report the finding that H2O plasma modification can introduce hydroxyl groups on carbon nanofiber (CNF) surface, and at the same time, highly preserve the microstructure of carbon support. Pt/CNF-H2O electrode possesses ultra-low Pt loading and superior electro-catalytic activity, poisoning-resistance ability and stability, suggesting a good candidate for fuel cell applications.
Modeling and experimental characterization of stepped and v-shaped {311} defects in silicon
Authors: Marqués Luis A. , Aboy María , Dudeck Karleen J. , Botton Gianluigi A. , Knights Andrew P. , Gwilliam Russell M.
Published: April 2014

We propose an atomistic model to describe extended {311} defects in silicon. It is based on the combination of interstitial and bond defect chains. The model is able to accurately reproduce not only planar {311} defects but also defect structures that show steps, bends, or both. We use molecular dynamics techniques to show that these interstitial and bond defect chains spontaneously transform into extended {311} defects. Simulations are validated by comparing with precise experimental measurements on actual {311} defects. The excellent agreement between the simulated and experimentally derived structures, regarding individual atomic positions and shape of the distinct structural {311} defect units, provides strong evidence for the robustness of the proposed model.
Electronic confinement in modulation doped quantum dots
Authors: Puthen Veettil B. , König D. , Patterson R. , Smyth S. , Conibeer G.
Published: April 2014

Modulation doping, an effective way to dope quantum dots (QDs), modifies the confinement energy levels in the QDs. We present a self-consistent full multi-grid solver to analyze the effect of modulation doping on the confinement energy levels in large-area structures containing Si QDs in SiO2 and Si3N4 dielectrics. The confinement energy was found to be significantly lower when QDs were in close proximity to dopant ions in the dielectric. This effect was found to be smaller in Si3N4, while smaller QDs in SiO2 were highly susceptible to energy reduction. The energy reduction was found to follow a power law relationship with the QD size.
Deposition order dependent magnetization reversal in pressure graded Co/Pd films
Authors: Greene P. K. , Kirby B. J. , Lau J. W. , Borchers J. A. , Fitzsimmons M. R. , Liu Kai
Published: April 2014

Magnetization reversal mechanisms and depth-dependent magnetic profile have been investigated in Co/Pd thin films magnetron-sputtered under continuously varying pressure with opposite deposition orders. For samples grown under increasing pressure, magnetization reversal is dominated by domain nucleation, propagation, and annihilation; an anisotropy gradient is effectively established, along with a pronounced depth-dependent magnetization profile. However, in films grown under decreasing pressure, disorders propagate vertically from the bottom high-pressure region into the top low-pressure region, impeding domain wall motion and forcing magnetization reversal via rotation; depth-dependent magnetization varies in an inverted order, but the spread is much suppressed.
Magnetic field induced insulating state in bilayer graphene at charge neutral point
Authors: Zhou Yang-Bo , Zhang Liang , Yu Da-Peng , Liao Zhi-Min
Published: April 2014

We investigate magnetotransport in the vicinity of the charge neutral point (CNP) in bilayer graphene at low temperatures. The CNP is found to vary with applied magnetic fields. Through measuring the transfer curves under different magnetic fields and at different temperatures, the temperature dependence of the peak resistivity at the CNP and under a fixed magnetic field is extracted. At low temperatures, it is found that the peak resistivity at the CNP increases exponentially with decreasing temperature under 14 T, which indicates the gap opening in zero-energy Landau level. The origins of such magnetic field induced insulating behavior are discussed.
Shape Recognition Elicited by Microsecond Flashes is Not Based on Photon Quantity
Authors: Greene Ernest
Published: April 2014

It is generally thought that the perceptual impact of a brief flash of light is determined by the quantity of photons the flash delivers. This means that only the total quantity of photons is important below a critical duration of about 30–100 ms. Recent findings have challenged this concept and the present work provides additional evidence that it is not correct. The first experiment reported here delivered a given quantity of photons in under 200 μs, either as a single threshold-intensity flash or as multiple flashes at the same intensity. The single flash was ineffective at eliciting recognition, but multiple flashes became progressively more effective as the number of flashes was increased. A second experiment varied the number of 10 μs flashes. The effectiveness of multiple flashes was far higher than would be expected on the basis of the total quantity of photons being delivered. The results of both experiments suggest that the brief transitions of intensity provided by the flashes are far more important than the quantity of photons. A final experiment examined the combined impact from two threshold-intensity flashes as the interstimulus interval was increased. The pair members were able to combine their influence for at least 100 ms. These results call for more attention to how very brief light flashes generate signals that convey image content.
Transformation of the cerebellum into more ventral brainstem fates causes cerebellar agenesis in the absence of
Ptf1a
function
Authors: Millen Kathleen J. , Steshina Ekaterina Y. , Iskusnykh Igor Y. , Chizhikov Victor V.
Published: April 2014

Significance

The contribution of cell fate misspecification to human brain disorders is poorly understood. The cerebellum, a major center of motor and sensory coordination, is frequently malformed in humans. During development it arises from dorsal hindbrain, but a long-standing question has been how the cerebellum is established along the dorsal–ventral axis of the neural tube. Here we identified the gene encoding pancreatic transcription factor PTF1A, which is inactivated in patients with cerebellar agenesis, as the first gene regulating the ventral limit of the cerebellum. We describe transformation of cerebellar neurons into more ventral extracerebellar fates as a novel mechanism of cerebellar agenesis. Our data provide some of the strongest evidence reported to date for a critical role of cell fate misspecification in a human brain developmental phenotype.
Toward a better understanding and quantification of methane emissions from shale gas development
Authors: Caulton Dana R. , Shepson Paul B. , Santoro Renee L. , Sparks Jed P. , Howarth Robert W. , Ingraffea Anthony R. , Cambaliza Maria O. L. , Sweeney Colm , Karion Anna , Davis Kenneth J. , Stirm Brian H. , Montzka Stephen A. , Miller Ben R.
Published: April 2014

Significance

We identified a significant regional flux of methane over a large area of shale gas wells in southwestern Pennsylvania in the Marcellus formation and further identified several pads with high methane emissions. These shale gas pads were identified as in the drilling process, a preproduction stage not previously associated with high methane emissions. This work emphasizes the need for top-down identification and component level and event driven measurements of methane leaks to properly inventory the combined methane emissions of natural gas extraction and combustion to better define the impacts of our nation’s increasing reliance on natural gas to meet our energy needs.
Avirulent strains of
Toxoplasma gondii
infect macrophages by active invasion from the phagosome
Authors: Zhao Yanlin , Marple Andrew H. , Ferguson David J. P. , Bzik David J. , Yap George S.
Published: April 2014

Significance

The classical active penetration model for
Toxoplasma
invasion was established in studies of infection of nonphagocytic host cells by virulent strains of the parasite. Here, we show that avirulent
Toxoplasma
parasites use a noncanonical invasion pathway when infecting macrophages. Instead of active penetration at cell surface, avirulent
Toxoplasma
parasites are initially phagocytosed by macrophages and, subsequently, form a parasite vacuole from a phagosomal compartment. This phagosome to vacuole invasion (PTVI) pathway is associated with more efficient infection of macrophages. We hypothesize that PTVI represents a Trojan horse strategy for phagocyte infection and may lead to enhanced systemic dissemination and immune stimulation, acute infection control, and chronic infection establishment.
Arthritogenic alphaviral infection perturbs osteoblast function and triggers pathologic bone loss
Authors: Chen Weiqiang , Foo Suan-Sin , Rulli Nestor E. , Taylor Adam , Sheng Kuo-Ching , Herrero Lara J. , Herring Belinda L. , Lidbury Brett A. , Li Rachel W. , Walsh Nicole C. , Sims Natalie A. , Smith Paul N. , Mahalingam Suresh
Published: April 2014

Significance

Persistent polyarthritis, which occurs in 30–40% of alphavirus-infected patients, has been proposed to be caused by proinflammatory mediators such as IL-6. In the present study we investigated the susceptibility and response of primary human osteoblasts to Ross River virus (RRV) infection and determined whether infection could result in bone pathology. RRV infection of osteoblasts resulted in increased receptor activator of nuclear factor-kappaB ligand (RANKL) but decreased osteoprotegerin (OPG). We are the first to report that alphavirus infection results in bone loss in an established RRV murine model and that this bone loss is prevented by IL-6 inhibition. These findings reveal that RRV can disrupt bone homeostasis and that osteoblasts play an important role in alphavirus-induced arthritis by regulating IL-6 and contribute to bone loss by disrupting the RANKL/OPG balance.
Optogenetic control of chemokine receptor signal and T-cell migration
Authors: Xu Yuexin , Hyun Young-Min , Lim Kihong , Lee Hyunwook , Cummings Ryan J. , Gerber Scott A. , Bae Seyeon , Cho Thomas Yoonsang , Lord Edith M. , Kim Minsoo
Published: April 2014

Significance

Precise regulation of chemokine signal is critical for directional migration of cells. In the study of complex cell behavior, it remains difficult to manipulate chemokine activity at precise times and places within living animals, and it is not possible to study different chemokine effects on defined cell types over a range of timescales. Furthermore, a given chemokine can activate multiple chemokine receptors and vice versa. Here we developed a photoactivatable chemokine receptor that can induce highly specific chemokine signals and guide cell migration toward the light stimulation. This work will advance our understanding of the cell migration process with a number of previously unidentified findings. Clinically, our photoactivatable chemokine receptor approach may have broad applications for adoptive cell transfer therapy.
Horizontal transfer of an adaptive chimeric photoreceptor from bryophytes to ferns
Authors: Li Fay-Wei , Villarreal Juan Carlos , Kelly Steven , Rothfels Carl J. , Melkonian Michael , Frangedakis Eftychios , Ruhsam Markus , Sigel Erin M. , Der Joshua P. , Pittermann Jarmila , Burge Dylan O. , Pokorny Lisa , Larsson Anders , Chen Tao , Weststrand Stina , Thomas Philip , Carpenter Eric , Zhang Yong , Tian Zhijian , Chen Li , Yan Zhixiang , Zhu Ying , Sun Xiao , Wang Jun , Stevenson Dennis W. , Crandall-Stotler Barbara J. , Shaw A. Jonathan , Deyholos Michael K. , Soltis Douglas E. , Graham Sean W. , Windham Michael D. , Langdale Jane A. , Wong Gane Ka-Shu , Mathews Sarah , Pryer Kathleen M.
Published: April 2014

Significance

Despite being one of the oldest groups of land plants, the majority of living ferns resulted from a relatively recent diversification following the rise of angiosperms. To exploit fully the new habitats created by angiosperm-dominated ecosystems, ferns had to evolve novel adaptive strategies to cope with the low-light conditions exerted by the angiosperm canopy. Neochrome, an unconventional photoreceptor that allows ferns to “see the light” better, was likely part of the solution. Surprisingly, we discovered that fern neochrome was derived from a bryophyte lineage via horizontal gene transfer (HGT). This finding not only provides the first evidence that a plant-to-plant HGT can have a profound evolutionary impact but also has implications for the evolution of photosensory systems in plants.
Rapidly reversible redox transformation in nanophase manganese oxides at room temperature triggered by changes in hydration
Authors: Birkner Nancy , Navrotsky Alexandra
Published: April 2014

Significance

In the present work, we find rapid and reversible transformations between nanoscale Mn2O3(more oxidized) and Mn3O4(more reduced) at room temperature as a function of changing hydration level. These phase transformations are controlled by a thermodynamic factor (difference in surface energy). Redox reactive Mn-oxide phases may be sensitive markers, on short time scales, of variations in water activity as well as oxygen fugacity in the local environment. Hydration-induced phase transformation has applications to geochemistry, planetary science, and technology.
Control of vacuolar dynamics and regulation of stomatal aperture by tonoplast potassium uptake
Authors: Andrés Zaida , Pérez-Hormaeche Javier , Leidi Eduardo O. , Schlücking Kathrin , Steinhorst Leonie , McLachlan Deirdre H. , Schumacher Karin , Hetherington Alistair M. , Kudla Jörg , Cubero Beatriz , Pardo José M.
Published: April 2014

Significance

Rapid fluxes of K
+
and other osmolytes in guard cells control the opening and closing of stomata and thereby gas exchange and transpiration of plants. Despite the well-established role of the plasma membrane of guard cells in stomatal function, osmolyte uptake into the cytosol represents only a transient step to the vacuole, as more than 90% of the solutes accumulate in these organelles. We show that the tonoplast-localized K
+
/H
+
exchangers mediate the vacuolar accumulation of K
+
in guard cells, and that activity of these transporters controls not only stomatal opening but also stomatal closure. We also establish vacuolar K
+
/H
+
exchange as a critical component involved in vacuolar remodeling and the regulation of vacuolar pH during stomatal movements.
MicroRNAs are critical regulators of tuberous sclerosis complex and mTORC1 activity in the size control of the
Xenopus
kidney
Authors: Romaker Daniel , Kumar Vikash , Cerqueira Débora M. , Cox Ryan M. , Wessely Oliver
Published: April 2014

Significance

The kidney is an essential organ to remove metabolic waste products and retain essential nutrients. To successfully execute these processes, the kidney and its functional unit, the nephron, must be correctly proportioned. Surprisingly, little is known about the processes governing kidney size. Here, we use the amphibian pronephric kidney as a paradigm to study the molecular mechanisms regulating size control. We show for the first time, to our knowledge, that growth factors belonging to the Insulin growth factor family are critically important in establishing kidney size. Moreover, we demonstrate that the strength of the signal is dependent on the presence of small noncoding RNAs termed microRNAs. These provide robustness to size control and ascertain that the kidney develops properly.
Brf1 posttranscriptionally regulates pluripotency and differentiation responses downstream of Erk MAP kinase
Authors: Tan Frederick E. , Elowitz Michael B.
Published: April 2014

Significance

Intercellular signaling pathways strongly regulate gene expression in uncommitted precursor stem cells, but the mechanisms through which these signaling pathways regulate gene targets often remain unclear. We address this question in mouse embryonic stem cells (mESCs) and highlight the importance of AU-rich element mRNA-binding proteins as regulatory intermediates of intercellular signaling. We show that the FGF/Erk MAP kinase signaling pathway strongly influences the expression of Brf1, a member of the Zfp36 protein family that is known to bind and destabilize its mRNA targets. Brf1 physically binds many pluripotency and differentiation-associated mRNAs. Moderate changes in its expression compromise self-renewal capacity and bias fate commitment, thus providing a posttranscriptional link between intercellular signaling activity and gene expression in mESCs.
Reactive cysteine persulfides and S-polythiolation regulate oxidative stress and redox signaling
Authors: Ida Tomoaki , Sawa Tomohiro , Ihara Hideshi , Tsuchiya Yukihiro , Watanabe Yasuo , Kumagai Yoshito , Suematsu Makoto , Motohashi Hozumi , Fujii Shigemoto , Matsunaga Tetsuro , Yamamoto Masayuki , Ono Katsuhiko , Devarie-Baez Nelmi O. , Xian Ming , Fukuto Jon M. , Akaike Takaaki
Published: April 2014

Significance

Reactive sulfur-containing compounds, such as
l
-cysteine hydropersulfide (CysSSH), reportedly form in mammals. However, the biological relevance of these reactive sulfur species remains unclear. We determined that CysSSH was synthesized from cystine by cystathionine β-synthase and cystathionine γ-lyase, which in turn may contribute to high levels of glutathione hydropersulfide (>100 μM) and other CysSSH derivatives of peptides/proteins formed in cells, tissues, and plasma from mice and humans. Compared with glutathione and hydrogen sulfide, CysSSH derivatives were superior nucleophiles and reductants and capable of regulating electrophilic cell signaling mediated by 8-nitroguanosine 3′,5′-cyclic monophosphate. Altogether, it is proposed that reactive Cys persulfides and S-polythiolation have critical regulatory functions in redox cell signaling.
Gq/5-HT
2c
receptor signals activate a local GABAergic inhibitory feedback circuit to modulate serotonergic firing and anxiety in mice
Authors: Spoida Katharina , Masseck Olivia A. , Deneris Evan S. , Herlitze Stefan
Published: April 2014

Significance

Serotonin is an important modulator of anxious states. Serotonergic neurotransmission in the dorsal raphe nuclei is known to be regulated by different presynaptic and postsynaptic feedback mechanisms involving G protein-coupled receptor signals, but the influence of such feedback mechanisms on anxiety-related behavior has not been investigated until now. We found that optogenetic activation of the Gq-coupled receptor signals in 5-HT
2c
receptor locations in GABAergic neurons in dorsal raphe nuclei decreases the activity of 5-HT neurons and relieves anxiety in mice. 5-HT
2c
receptors are drug targets for mental disorders. Our results demonstrate a previously unidentified negative feedback mechanism by 5-HT
2c
/Gq signals for the fine-tuning of anxiety behavior, and point to a promising therapeutic strategy for treating anxiety-related disorders.
Tumor microenvironment-based feed-forward regulation of NOS2 in breast cancer progression
Authors: Heinecke Julie L. , Ridnour Lisa A. , Cheng Robert Y. S. , Switzer Christopher H. , Lizardo Michael M. , Khanna Chand , Glynn Sharon A. , Hussain S. Perwez , Young Howard A. , Ambs Stefan , Wink David A.
Published: April 2014

Significance

More than 92% of ER−breast cancer patients die with moderate to high NOS2. In this report, we show that tumor cell NOS2, through formation of a specific flux of NO, drives ER−disease to a more aggressive phenotype. Correlation between NOS2-related genes from patient cohorts, in vitro, and animal experiments show an inflammatory loop mediated by NOS2 that makes ER−breast cancer an aggressive disease.
Single bacterial strain capable of significant contribution to carbon cycling in the surface ocean
Authors: Pedler Byron E. , Aluwihare Lihini I. , Azam Farooq
Published: April 2014

Significance

Primary production generates a reservoir of dissolved organic carbon (DOC) in the ocean as large as the global inventory of atmospheric CO
2
. Once formed, DOC accumulates on timescales from less than 1 hour to millennia. Bacteria are important contributors to the respiration of DOC to CO
2
and the conversion of DOC to refractory biopolymers. Yet, the quantitative contribution of individual species within diverse consortia to DOC cycling remains unknown. We report that a single bacterial strain can consume as much DOC as diverse free-living microbial communities. This taxon is commonly observed in seawater when labile carbon is available, and may serve a key ecosystem function by rapidly recycling and regulating the level of DOC while also supporting ocean food webs.
PDGFRβ reverses EphB4 signaling in alveolar rhabdomyosarcoma
Authors: Aslam M. Imran , Abraham Jinu , Mansoor Atiya , Druker Brian J. , Tyner Jeffrey W. , Keller Charles
Published: April 2014

Significance

Effective targeted therapies to complement already intensive chemotherapy are much needed for the childhood muscle cancer rhabdomyosarcoma, yet few targeted agents have been identified that improve long-term survival. In particular, the alveolar subtype of rhabdomyosarcoma accounts for disproportionate mortality. Herein, the receptor tyrosine kinase EphB4 is identified as a potential two-way switch for alveolar rhabdomyosarcoma. Whereas the typical EphB4 ligand, EphrinB2, drives tumor cells toward apoptosis, the interaction between EphB4 and another receptor tyrosine kinase, PDGFRβ, drives tumors to proliferate in the presence of the PDGFRβ ligand, PDGF-BB. The Food and Drug Administration-approved dual EphB4-PDGFRβ inhibitor, dasatinib, is found to have significant preclinical activity, which is clinically relevant because EphB4 and PDGFRβ are independent poor prognostic factors in this childhood disease.
Secretion of von Willebrand factor by endothelial cells links sodium to hypercoagulability and thrombosis
Authors: Dmitrieva Natalia I. , Burg Maurice B.
Published: April 2014

Significance

Cardiovascular thrombotic events are a leading cause of mortality and morbidity worldwide. Hypercoagulability increases the risk of thrombosis. This study shows that elevated sodium concentration stimulates endothelial production of a key initiator of the clotting cascade, von Willebrand factor, leading to increased coagulation and thrombogenesis. In everyday life, increases in blood sodium often occur as the result of insufficient drinking, excessive water loss, or high salt intake. Therefore, our results indicate that water and salt intake are modifiable factors affecting coagulability and risk of thrombosis. In clinical practice, sustained elevation of plasma sodium is a part of widely used hypertonic saline therapy. Our results suggest that monitoring of coagulation during the therapy might be beneficial to prevent thrombotic complications.
Prosodic enhancers of humorous effect in political speeches
Authors: Sayenko Tetyana
Published: April 2014

Oral delivery remains one of the crucial factors determining the final effect of a potentially humorous remark. Nevertheless, there is almost no research on the prosodic features of humor used in public speaking. In order to understand what kind of prosodic arrangement makes a potentially humorous message funny, the author conducted a communicative-pragmatic and experimental-phonetic analysis of the original recordings of six political addresses delivered by British and American leaders. The research results show that specific changes in tempo-rhythm, pauses, and expressive intonation can serve as enhancers of humorous effect in speech. The findings also support the hypothesis about the dominant role of timing in using humor effectively. Prosodic marking of humorous remarks, however, depends upon their type and function in the argumentative structure of the whole speech.
US National Security Strategy
Authors: Degano Chiara
Published: April 2014

The paper analyzes strategic maneuvering in National Security Strategy reports, crucial documents within the repertoire of US presidential discourse, whereby the Administration’s plans for security are laid out before the Congress and the world. Building on the pragma-dialectical approach, and drawing at the same time on the linguistic-oriented discourse analytic frame, the study contributes to testing the viability of putting the quantitative tools of corpus linguistics to use for the analysis of argumentation.
Findings show that while maintaining substantial generic integrity, and sharing to a certain extent a common set of values, NSS reports produced by different administrations differ greatly in terms of topical selection, adaptation to the audience and presentational devices.
Coarticulation and Sound Change in Romance
Authors: Recasens Daniel
Published: April 2014

This volume should be of great interest to phoneticians, phonologists, and both historical and cognitive linguists. Using data from the Romance languages for the most part, the book explores the phonetic motivation of several sound changes, e.g., glide insertions and elisions, vowel and consonant insertions, elisions, assimilations and dissimilations. Within the framework of the DAC (degree of articulatory constraint) model of coarticulation, it clearly demonstrates that the typology and direction of these sound changes may very largely be accounted for by the coarticulatory effects occurring between adjacent or neighbouring phonetic segments, and by the degrees of articulatory constraint imposed by speakers on the production of vowels and consonants. The phonetically-based explanations presented here are formulated on the basis of coarticulation data from speech production and perception research carried out during the last fifty years and are complemented with data on the co-occurrence of phonetic segments in lexical forms of the languages being considered. Attention is also paid to the role that positional and prosodic factors play in sound change implementation, as well as to the cognitive and peripheral strategies involved in segmental replacements, elisions and insertions.
Prosodic Licensing and the development of phonological and morphological representations
Authors: Demuth Katherine
Published: April 2014

One of the challenges for understanding the processes underlying the acquisition of phonology has been the variability found in early speech productions. Our recent research suggests that much of this is due to the phonological (or prosodic) context in which words (and their segments) appear. This paper explores some of the recent findings on children’s acquisition of phonological/prosodic units as a function of syllable and word structure, showing how acoustic analysis provides evidence of children’s developing phonological representations from their first words. It then shows that similar processes can account for the variable emergence of early grammatical morphemes, suggesting that these are also Prosodically Licensed. These findings are discussed in terms of a developmental model of language planning and production.
Covert contrast in the acquisition of second language phonology
Authors: Eckman Fred , Iverson Gregory , Song Jae Yung
Published: April 2014

This paper reports results on the acquisition of the English /s/ – /z/ phonemic contrast by native speakers of Spanish. The central finding is that some of the research participants exhibited a covert contrast between these segments in their interlanguage productions. Acoustic analysis revealed that four of the participants produced a statistically reliable distinction between English [s] and [z], however, this difference was not perceived by the transcribers who were phonetically trained, native speakers of English. The existence of a stage of covert contrast in L2 phonology is eminently plausible, given the progressive nature of phonological acquisition, and brings the learning of second-language contrasts into conformity with findings in the areas of L1 acquisition and phonologically disordered speech.
Sibling rivalry
Authors: Ingram David , Dubasik Virginia L.
Published: April 2014

Ingram, Dubasik, Liceras & Fernández Fuertes (2011) developed a measure of phonological similarity that compares phonological samples across 4 levels (whole words, word shapes (syllables), consonant inventories, consonant correctness), using 9 measures in total. The present study used the similarity measure to compare 4 dyads of children: identical twins, non-identical twins, non-twin siblings born 2 years apart, non-twin siblings born 5 years apart. Results indicated that phonological similarity decreased across the 4 dyads, providing evidence for genetic and environmental effects. The differences across dyads varied by phonological level, thus, indicating the importance of conducting multi-dimensional phonological analyses.