bluuebunny/crossref_metadata_2025 huggingface dataset:
Properties of bubbled gases transportation in a bromothymol blue aqueous solution under gradient magnetic fields
Authors: Iwasaka M. , Kurita S. , Owada N.
Published: March 2012

A new system for the observation of the transport process of dissolved oxygen and carbon-dioxide gases is proposed that utilizes a water-containing column with an optical monitoring unit under gradient magnetic fields of up to 5 T. The system consists of a column for liquid chromatography with “branching flow” tubing at the center of a vertical bore of a superconducting magnet of 5 T. By utilizing bromothymol blue (BTB) as a CO2 concentration indicator, CO2 concentration in the bifurcated liquid stream from the gradient magnetic fields was measured by a time-resolved spectrophotometer in the range of 550 nm-660 nm. The results indicated that the gradient magnetic fields of up to 5 T accelerated the pushing-out of the CO2-rich BTB solution from the branched inlet of the column. Comparing the effects of O2-gas bubbling with He-gas bubbling, it was found that the oxygen gases dissolved in a BTB aqueous solution controlled the transport of CO2 gases in the solution under gradient magnetic fields of up to 5 T. By monitoring the chromatogram pattern of oxygen-gas-bubbled water flow in a straight flow system at the UV band, it was indicated that the paramagnetic oxygen-gas-bubbles stay longer in the magnetic field center of the magnet. The proposed method with the branch flow can enhance the condensation of carbon dioxide gases in a room temperature liquid by the assistance of oxygen-gas in water under gradient magnetic fields of up to 5 T.
Magnetic and magnetotransport properties of misfit cobaltate Ca3Co3.93O9+δ
Authors: Hejtmánek J. , Knížek K. , Maryško M. , Jirák Z. , Sedmidubský D. , Jankovský O. , Huber Š. , Masschelein P. , Lenoir B.
Published: March 2012

Samples of Ca3Co3.93O9+δ, prepared by classical ceramic route (CCR) and spark plasma sintering (SPS), were characterized by means of magnetic, electrical, and thermal experiments in a broad temperature range. The low temperature specific heat measured down to 0.3 K, reveals two important electronic contributions: the first one, dominated by magnetic excitations, that can be suppressed by an external magnetic field, and the second, due to band-like carriers, characterized by γ ∼ 50 mJ mol−1 K−1 for both samples. The ferrimagnetism, associated with the long-range magnetic order of IS Co3+ species in rock-salt blocks detected below TF ∼15 K in the CCR samples, is absent in the SPS samples. Similarly, the specific heat peaks detected for the CCR sample at 410 and 840 K are not reproduced in the case of the SPS sample. In both samples the low temperature thermoelectric power is quantitatively explained by supposing the strongly correlated carriers are carrying the spin entropy. The lower hole concentration in the SPS than in the CCR sample is likely responsible for its higher thermopower, namely, at high temperatures where the configuration entropy of hopping carriers dominates.
Effects of notch shape on the magnetic domain wall motion in nanowires with in-plane or perpendicular magnetic anisotropy
Authors: Noh Su Jung , Miyamoto Yasuyoshi , Okuda Mitsunobu , Hayashi Naoto , Keun Kim Young
Published: March 2012

Magnetic domain walls (DWs) in nanowires have been extensively investigated for potential applications in spintronic devices. For the precise storage of magnetic data, the control of DW pinning and depinning is critical. Here, we report upon the micromagnetic modeling results of the DW motion behaviors in notched or anti-notched nanowires possessing in-plane magnetic anisotropy (IMA) or perpendicular-to-the-plane magnetic anisotropy (PMA). In the nanowires with IMA, the energy of the DW in nanowires with anti-notches was lower compared to that of the nanowires with normal notches. Easier DW depinning motions were observed in the anti-notched nanowires. Unlike in the IMA case, the DW energy in the nanowires with PMA was lower with normal notches. Thus, the DW was able to move faster and easier through the normal notches compared to the anti-notches in the nanowire with the PMA at the same current density.
Size dependence of spin-torque induced magnetic switching in CoFeB-based perpendicular magnetization tunnel junctions (invited)
Authors: Sun J. Z. , Trouilloud P. L. , Gajek M. J. , Nowak J. , Robertazzi R. P. , Hu G. , Abraham D. W. , Gaidis M. C. , Brown S. L. , O’Sullivan E. J. , Gallagher W. J. , Worledge D. C.
Published: March 2012

CoFeB-based magnetic tunnel junctions with perpendicular magnetic anisotropy are used as a model system for studies of size dependence in spin-torque–induced magnetic switching. For integrated solid-state memory applications, it is important to understand the magnetic and electrical characteristics of these magnetic tunnel junctions as they scale with tunnel junction size. Size-dependent magnetic anisotropy energy, switching voltage, apparent damping, and anisotropy field are systematically compared for devices with different materials and fabrication treatments. Results reveal the presence of sub-volume thermal fluctuation and reversal, with a characteristic length-scale of the order of approximately 40 nm, depending on the strength of the perpendicular magnetic anisotropy and exchange stiffness. To have the best spin-torque switching efficiency and best stability against thermal activation, it is desirable to optimize the perpendicular anisotropy strength with the junction size for intended use. It also is important to ensure strong exchange-stiffness across the magnetic thin film. These combine to give an exchange length that is comparable or larger than the lateral device size for efficient spin-torque switching.
Charge-transfer induced ferromagnetism in nanostructured ZnO/Al powders: An x-ray absorption near edge structure study
Authors: Chen S. J. , Garitaonandia J. S. , Suzuki K.
Published: March 2012

The correlation between the x-ray absorption spectra and the magnetic properties for Al doped ZnO nanostructures prepared by mechanical alloying has been studied in order to clarify the origin of the room-temperature ferromagnetism in the Al doped ZnO nanostructures. Room-temperature ferromagnetism is induced in nanostructured ZnO-Al powders by milling without any ferromagnetic dopant. The O and Al K-edge x-ray absorption spectra acquired from the ferromagnetic ZnO-Al powders indicate a clear sign of a charge transfer from Al to O on ZnO. The comparison of the florescence yield and total electron yield spectra suggests that this charge transfer takes place mostly at the surface of ZnO particles. Our results show that the surface charge transfer between Al and O plays an important role in the induction of spontaneous magnetization in the Al doped ZnO.
A study of the perpendicular magnetic microstructure of the L10 FePt epitaxial film using electron holography
Authors: Park J. K. , Lee W. H. , Yoo J. H. , Yang J. M.
Published: March 2012

The magnetic microstructure of the L10 FePt perpendicular magnetic film, grown epitaxially on MgO substrate, was studied using high-resolution electron holography. It was shown that the hologram-fringe information of stray-fields can be used to determine the sense of stray-fields and thus, the sense of perpendicular magnetizations inside the film. Furthermore, we were able to directly reveal the detailed perpendicular magnetic structure of L10 FePt epitaxial film by constructing unwrapped phase-image and induction mapping. The perpendicular induction-strength was varying with the domain size. The variation of induction-strength was due to a variation of the degree of ordering in the weakly ordered film.
Coercivity enhancement in anisotropic Pr13Fe79.4B7Nb0.3Ga0.3 powders
Authors: Lin Zhong , Han Jingzhi , Liu Shunquan , Xing Meiying , Zhang Yan , Wang Changsheng , Yang Jinbo , Yang Yingchang
Published: March 2012

Highly anisotropic Pr13Fe79.4B7Nb0.3Ga0.3 powders with a residual magnetization of 1.4 T, an intrinsic coercivity of 10 kOe, and a maximum energy product of 32 MGOe were obtained by a modified hydrogenation disproportionation desorption recombination (HDDR) process. It was found that self-organized rod-like disproprotionation microstructure is helpful for the formation of anisotropy (the crystal texture). To further improve the coercivity, the HDDR treated powders were mixed with Pr68Cu32 powders and then were heated in vacuum. As a result, the coercivity of the HDDR powders was enhanced from 10 kOe to 14 kOe. Microstructure investigations show that after heat treatment, the grain-boundary phase becomes thicker and is rich in Pr and Cu elements. The modified grain-boundary layer may cause a stronger magnetic decoupling effect among Pr2Fe14B grains and is helpful for the enhancement of coercivity.
Room temperature spontaneous magnetization in calcined trioctylphosphine-ZnO nanoparticles
Authors: Ortega D. , Chen S. J. , Suzuki K. , Garitaonandia J. S.
Published: March 2012

In this work, it is demonstrated that capping with trioctylphosphine oxide (TOPO) induces a ferromagnetic response in free-standing ZnO nanoparticles upon calcination without the necessity of metallic doping. Samples were synthesized by precipitation of zinc acetate solutions in a basic medium followed by capping with TOPO and heat treatment in static aerobic conditions. Nanoparticles show a wurtzite-type structure with an average size of 14 nm, and magnetization measurements evidence a spontaneous magnetic moment at room temperature for calcined nanoparticles, in contrast with the diamagnetic response observed in non-calcined TOPO-capped nanoparticles. Giving the absence of any magnetic impurity or metal dopant that could account for the total magnetization, it is proposed that the magnetism would be consistent with a charge transfer mechanism promoted by a phosphorous doping upon calcination of TOPO over the nanoparticles. This situation leads to a spontaneous magnetic moment by the local fulfillment of Stoner’s criterion for ferromagnetism at the nanoparticles surface.
Angular dependence of current perpendicular to plane giant magnetoresistance in multilayer nanowire
Authors: Qu Tao , Victora R. H.
Published: March 2012

We use incoherent scattering matrices to calculate the angle dependent magnetoresistance and find analytic expressions for a tri-layer current-perpendicular-to-plane nanowire. We find that the non-linearity of magnetoresistance versus β = cos2(θ/2) can be quantitatively explained by reflected electrons using only experimental spin polarization as input. We extend this model to a multilayer nanowire and find the simulation approximately matches experiment.
Effects of Ag additions on melt-spun RE2Fe14B microstructure and texture
Authors: Oster N. T. , Cavanaugh D. T. , Dennis K. W. , Kramer M. J. , McCallum R. W. , Anderson I. E.
Published: March 2012

Control of microstructure and texture is of critical importance in forming rare earth (RE)-iron-boron particulate suitable for anisotropic polymer-bonded permanent magnets and anisotropic sintered permanent magnets. In this study, the selected approach to controlling grain size, while maintaining texture, is through stabilization and refinement of directional growth in melt-spun ribbons. Varying concentrations of Ag were added to melt-spun ribbons of composition (Y0.55Nd0.45)2.2Fe14B1.1. Effects on microstructure and texture were observed through scanning electron microscopy (SEM) and x-ray diffraction (XRD). It was determined that Ag stabilized columnar growth (compared to alloys with no Ag added) with additions as small as 0.3 at. %, but the Ag also produced a unique texture in the ribbons. In RE-Fe-B ribbons without Ag, strong <00l> texture is observed at the free surface and a mechanism has been established. In all Ag-containing ribbons, the observed texture is canted to both the c- and a-axes, but the mechanism remains unclear.
Note: Experiments in hard x-ray chemistry: In situ production of molecular hydrogen and x-ray induced combustion
Authors: Pravica Michael , Bai Ligang , Park Changyong , Liu Yu , Galley Martin , Robinson John , Hatchett David
Published: March 2012

We have successfully loaded H2 into a diamond anvil cell at high pressure using the synchrotron x-ray induced decomposition of NH3BH3. In a second set of studies, radiation-assisted release of O2 from KCLO3, H2 release from NH3BH3, and reaction of these gases in a mixture of the reactants to form liquid water using x-rays at ambient conditions was observed. Similar observations were made using a KCLO3 and NaBH4 mixture. Depending on reaction conditions, an explosive or far slower reaction producing water was observed.
Annealing effect on the excess conductivity of Cu0.5Tl0.25M0.25Ba2Ca2Cu3O10−δ (M = K, Na, Li, Tl) superconductors
Authors: Hassan Najmul , Irfan M. , Khan Nawazish A. , Khan Salah , Shakoor A. , Majid A. , Jadoon Atif M. , Hayyat Sardar Sikander
Published: March 2012

The effect of oxygen annealing on the excess conductivity of Cu0.5Tl0.25M0.25Ba2Ca2Cu3O10−δ (M = K, Na, Li, Tl) samples is investigated. From the analysis of results, we have evaluated the exponents, the coherence length, the crossover temperature, and interlayer coupling strength (J) of the samples. These studies show that the K-doped post-annealed sample has shown narrow transition width with improvement in 2D and 3D conductivities. Oxygen annealing has also enhanced the coherence length and interlayer coupling strength of the material. Na- and Li-doped post-annealed samples have shown increased transition width, poor 2D and 3D conductivities within narrow temperature windows. After annealing, reduction in coherence length and the interlayer coupling strength is also observed. While in Tl-doped sample, oxygen annealing has not caused much deviation in fluctuation induced conductivity (FIC) parameters. The underlying cause of improved behavior of post-annealed K-doped sample is also discussed.
Enhancement of thermoelectric efficiency and violation of the Wiedemann-Franz law due to Fano effect
Authors: Gómez-Silva G. , Ávalos-Ovando O. , Ladrón de Guevara M. L. , Orellana P. A.
Published: March 2012

We consider the thermoelectric properties of a double-quantum-dot molecule coupled in parallel to metal electrodes with a magnetic flux threading the ring. By means of the Sommerfeld expansion we obtain analytical expressions for the electric and thermal conductances, thermopower and figure of merit for arbitrary values of the magnetic flux. We neglect electronic correlations. The Fano antiresonances in transmission demand that terms usually discarded in the Sommerfeld expansion are taken into account. We also explore the behavior of the Lorenz ratio L = κ/σT, where κ and σ are the thermal and electrical conductances and T the absolute temperature, and we discuss the reasons why the Wiedemann-Franz law fails in presence of Fano antiresonances.
Biaxial order and a rotation of the minor director in the nematic phase of an organo-siloxane tetrapode by the electric field
Authors: Merkel K. , Nagaraj M. , Kocot A. , Kohlmeier A. , Mehl G. H. , Vij J. K.
Published: March 2012

Biaxiality in the nematic phase for a liquid crystalline tetrapode made up of organo-siloxanes mesogens is investigated using polarized infrared spectroscopy. An ordering of the minor director for the homeotropically aligned sample is found to depend on the amplitude of the in-plane electric field. On increasing the in-plane electric field, the minor director, lying initially along the rubbing direction, rotates to the direction of the applied field. The scalar order parameters of the second rank tensor are found to depend significantly on the strength of the electric field. A most significant increase is found in the nematic order parameter and in the parameter that characterizes the phase biaxiality.
Polarization consistent basis sets. VII. The elements K, Ca, Ga, Ge, As, Se, Br, and Kr
Authors: Jensen Frank
Published: March 2012

Polarization consistent basis sets, optimized for density functional calculations, are proposed for the elements K, Ca, Ga, Ge, As, Se, Br, and Kr. The basis set composition in terms of number of primitive functions and the contraction is defined based on energetic analyses of atoms and molecules along the lines used in previous work and on the performance for molecular systems. The performance for atomization energies and dipole moments is compared to other widely used basis sets, and it is shown that the new basis sets allow a systematic reduction of basis set errors and in general perform better than existing ones.
Conversion of parahydrogen induced longitudinal two-spin order to evenly distributed single spin polarisation by optimal control pulse sequences
Authors: Bretschneider Christian , Karabanov Alexander , Nielsen Niels Chr. , Köckenberger Walter
Published: March 2012

Strongly enhanced spin polarization in the form of longitudinal spin order can be generated on target molecules by using parahydrogen in a catalyzed hydrogenation reaction. An optimal control algorithm was used to generate radiofrequency pulse sequences which convert the arising longitudinal two-spin order into single-spin Zeeman order with high efficiency and distribute it evenly between three coupled spins within the same molecule. The pulses are designed to be very robust towards variations in the B0 and B1 fields. Furthermore, this strategy is applied to enhance the NMR signal in an ultrafast gradient assisted single excitation two-dimensional spectroscopy experiment.
Optimal transport by omni-potential flow and cosmological reconstruction
Authors: Frisch Uriel , Podvigina Olga , Villone Barbara , Zheligovsky Vladislav
Published: March 2012

One of the simplest models used in studying the dynamics of large-scale structure in cosmology, known as the Zeldovich approximation, is equivalent to the three-dimensional inviscid Burgers equation for potential flow. For smooth initial data and sufficiently short times it has the property that the mapping of the positions of fluid particles at any time t1 to their positions at any time t2 ⩾ t1 is the gradient of a convex potential, a property we call omni-potentiality. Are there other flows with this property that are not straightforward generalizations of Zeldovich flows? This is answered in the affirmative in both two and three dimensions. How general are such flows? Using a WKB technique we show that in two dimensions, for sufficiently short times, there are omni-potential flows with arbitrary smooth initial velocity. Mappings with a convex potential are known to be associated with the quadratic-cost optimal transport problem. This has important implications for the problem of reconstructing the dynamical history of the universe from the knowledge of the present mass distribution.
Plasmonic quantum dot solar cells for enhanced infrared response
Authors: Feng Lu Hao , Mokkapati Sudha , Fu Lan , Jolley Greg , Hoe Tan Hark , Jagadish Chennupati
Published: March 2012

Enhanced near infrared photoresponse in plasmonic InGaAs/GaAs quantum dot solar cells (QDSC) is demonstrated. Long wavelength light absorption in the wetting-layer and quantum-dot region of the quantum dot solar cell is enhanced through scattering of light by silver nanoparticles deposited on the solar cell surface. Plasmonic light trapping results in simultaneous increase in short-circuit current density by 5.3% and open circuit voltage by 0.9% in the QDSC, leading to an overall efficiency enhancement of 7.6%.
Flexible solid-state paper based carbon nanotube supercapacitor
Authors: Hu Shan , Rajamani Rajesh , Yu Xun
Published: March 2012

This paper presents a flexible solid-state supercapacitor of high energy density. The electrodes of the supercapacitor are made of porous and absorbent cotton paper coated with single-wall carbon nanotubes. To ensure all solid-state configuration, a solid-state polymer-based electrolyte (poly (vinyl alcohol)/phosphoric acid) is used. The as-fabricated supercapacitor can be charged to over 3 V. It has high specific capacitance and high energy density of 115.8301 F/g carbon and 48.8587 Wh/kg carbon. Its performance is comparable to that of commercial supercapacitors, which need to utilize liquid electrolytes. Flexible solid-state supercapacitors offer several significant advantages for use in hybrid electric vehicles.
Elliptically polarized harmonic emission in a quantum dot
Authors: Xie Yan , Duan Suqing , Zhang Wei , Chen Jing , Chu Weidong
Published: March 2012

We study the polarization of harmonic emission in a V-type three-level system formed in a real asymmetrical quantum dot. It is found that the polarization property of harmonics can be strongly modulated by the intensity of linearly polarized driving field. Under the modulation of the field, elliptically polarized emissions with large ellipticity are produced and the interesting linear-to-elliptical polarization conversion happens. By mapping the optical process to a particle transport process of a three-chain system, we reveal the fact that the phenomenon of polarization conversion results from the coherent destruction of transitions induced by emission photons in the dynamic process. Our work provides a method to control the polarization of harmonics and is helpful for understanding the interference in harmonic emission of multilevel systems.
Angular dependence of pinning potential, upper critical field, and irreversibility field in underdoped BaFe1.9Co0.1As2 single crystal
Authors: Shahbazi M. , Wang X. L. , Ghorbani S. R. , Dou S. X. , Choi K. Y.
Published: March 2012

Underdoped BaFe1.9Co0.1As2 single crystal was studied by angular dependence of magneto-transport at fields up to 13 T over a wide range of temperature. Our results show that pinning potential, Uo, decreases slightly for θ ≤ 45° and remains constant for θ ≥ 45°, while the upper critical field, Hc2, and the irreversibility field, Hirr, increase with θ. According to anisotropic Ginzburg-Landau theory, the anisotropy was determined by scaling the resistivity under different magnetic fields below the superconducting critical temperature, Tc. Anisotropy, Γ, in the underdoped crystal is found to be temperature dependent and decreases from 2.1 to 1.8 for as T is reduced from 17 to 12.5 K.
Standoff detection of ozone in an open environment using photoacoustic spectroscopy technique
Authors: Chien Hual-Te , Wang Ke , Sheen Shuh-Haw , Raptis Apostolos C.
Published: March 2012

The current work reports a practical photoacoustic spectroscopy (PAS) technique that can be applied for the standoff detection of ozone in an open environment. The developed PAS detection system consists of a laser, a parabolic acoustic reflector, and an acoustic resonator that acts as a lock-in amplifier to extract only the signals resonating with the laser chopping frequency. The design of the acoustic resonator is described, and a detection capability of 700 ppb ozone at 2 m distance in the ambient air is demonstrated. The system would have broad applications for open-air detection of chemicals in various forms.
Microfluidic sorting of microtissues
Authors: Buschke D. G. , Resto P. , Schumacher N. , Cox B. , Tallavajhula A. , Vivekanandan A. , Eliceiri K. W. , Williams J. C. , Ogle B. M.
Published: March 2012

Increasingly, invitro culture of adherent cell types utilizes three-dimensional (3D) scaffolds or aggregate culture strategies to mimic tissue-like, microenvironmental conditions. In parallel, new flow cytometry-based technologies are emerging to accurately analyze the composition and function of these microtissues (i.e., large particles) in a non-invasive and high-throughput way. Lacking, however, is an accessible platform that can be used to effectively sort or purify large particles based on analysis parameters. Here we describe a microfluidic-based, electromechanical approach to sort large particles. Specifically, sheath-less asymmetric curving channels were employed to separate and hydrodynamically focus particles to be analyzed and subsequently sorted. This design was developed and characterized based on wall shear stress, tortuosity of the flow path, vorticity of the fluid in the channel, sorting efficiency and enrichment ratio. The large particle sorting device was capable of purifying fluorescently labelled embryoid bodies (EBs) from unlabelled EBs with an efficiency of 87.3% ± 13.5%, and enrichment ratio of 12.2 ± 8.4 (n = 8), while preserving cell viability, differentiation potential, and long-term function.
Near infrared electroluminescence from n-InN/p-GaN light-emitting diodes
Authors: Wu Guo-Guang , Li Wan-Cheng , Shen Chun-Sheng , Gao Fu-Bin , Liang Hong-Wei , Wang Hui , Song Li-Jun , Du Guo-Tong
Published: March 2012

Undoped InN thin film was grown on p-GaN/Al2O3 (0001) template by molecular beam epitaxy. Near-infrared (NIR) electroluminescence (EL) that overlapped the optical communication wavelength range was realized using the n-InN/p-GaN heterojunction structure. The light emitting diode showed typical rectification characteristics with a turn-on voltage of around 0.8 V. A dominant narrow NIR emission peak was achieved from the InN side under applied forward bias. By comparing with the photoluminescence spectrum, the EL emission peak at 1573 nm was attributed to the band-edge emission of the InN film.
Helical flows of fractionalized Burgers' fluids
Authors: Jamil Muhammad , Khan Najeeb Alam
Published: March 2012

The unsteady flows of Burgers’ fluid with fractional derivatives model, through a circular cylinder, is studied by means of the Laplace and finite Hankel transforms. The motion is produced by the cylinder that at the initial moment begins to rotate around its axis with an angular velocity Ωt, and to slide along the same axis with linear velocity Ut. The solutions that have been obtained, presented in series form in terms of the generalized Ga,b,c(•, t) functions, satisfy all imposed initial and boundary conditions. Moreover, the corresponding solutions for fractionalized Oldroyd-B, Maxwell and second grade fluids appear as special cases of the present results. Furthermore, the solutions for ordinary Burgers’, Oldroyd-B, Maxwell, second grade and Newtonian performing the same motion, are also obtained as special cases of general solutions by substituting fractional parameters α = β = 1. Finally, the influence of the pertinent parameters on the fluid motion, as well as a comparison among models, is shown by graphical illustrations.
Differences in morpho-physiological leaf traits reflect the response of growth to drought in a seeder but not in a resprouter Mediterranean species
Authors: Ramírez David A. , Parra Antonio , Resco de Dios Víctor , Moreno José M.
Published: March 2012

Understanding the mechanisms underlying the response of different plant functional types to current and projected changes in rainfall is particularly important in drought-prone areas like the Mediterranean. Here, we report the responses of two species with contrasting leaf characteristics and post-fire regeneration strategies (Cistus ladanifer L., malacophyllous, seeder; Erica arborea L., sclerophyllous, resprouter) to a manipulative field experiment that simulated a severe drought (45% reduction of historical average rainfall). We measured monthly changes in relative growth rate (RGR), specific leaf area (SLA), bulk leaf carbon isotope composition (δ13C), predawn water potential (Ψpd), photosynthetic gas exchange, bulk modulus of elasticity and osmotic potential at maximum turgor (π). Temporal (monthly) changes in RGR of C. ladanifer were correlated with all measured leaf traits (except π) and followed Ψpd variation. However, the temporal pattern of RGR in E. arborea was largely unrelated to water availability. SLA monthly variation reflected RGR variation reasonably well in C. ladanifer, but not in E. arborea, in which shoot growth and δ13C increased at the time of maximum water stress in late summer. The relationship between water availability, and RGR and carbon assimilation in C. ladanifer, and the lack of any relationship in E. arborea suggest that the former has an enhanced capacity to harness unpredictable rainfall pulses compared with the latter. These contrasting responses to water availability indicate that the projected changes in rainfall with global warming could alter the competitive ability of these two species, and contribute to changes in plant dominance in Mediterranean shrublands.
Attitudes towards credit and finances among college students in China and the United States
Authors: Norvilitis Jill M. , Mao Yingmei
Published: March 2012

Although there is growing concern about the issue of credit card debt among college students in China, little research has examined attitudes to money and debt among that group. The present study compared financial self‐confidence, perceived financial wellbeing, attitudes to debt, and parent education about money and debt in 410 college students from the US and China. Although college students in China reported fewer credit cards and less debt, they also reported lower levels of financial self‐confidence and financial wellbeing. In both cultures, delay of gratification and parental education predicted both self‐confidence and financial wellbeing.
A VE-cadherin–PAR3–α-catenin complex regulates the Golgi localization and activity of cytosolic phospholipase A2α in endothelial cells
Authors: Odell Adam F. , Hollstein Monica , Ponnambalam Sreenivasan , Walker John H.
Published: March 2012

Phospholipase A2enzymes hydrolyze phospholipids to liberate arachidonic acid for the biosynthesis of prostaglandins and leukotrienes. In the vascular endothelium, group IV phospholipase A2α (cPLA2α) enzyme activity is regulated by reversible association with the Golgi apparatus. Here we provide evidence for a plasma membrane cell adhesion complex that regulates endothelial cell confluence and simultaneously controls cPLA2α localization and enzymatic activity. Confluent endothelial cells display pronounced accumulation of vascular endothelial cadherin (VE-cadherin) at cell–cell junctions, and mechanical wounding of the monolayer stimulates VE-cadherin complex disassembly and cPLA2α release from the Golgi apparatus. VE-cadherin depletion inhibits both recruitment of cPLA2α to the Golgi and formation of tubules by endothelial cells. Perturbing VE-cadherin and increasing the soluble cPLA2α fraction also stimulated arachidonic acid and prostaglandin production. Of importance, reverse genetics shows that α-catenin and δ-catenin, but not β-catenin, regulates cPLA2α Golgi localization linked to cell confluence. Furthermore, cPLA2α Golgi localization also required partitioning defective protein 3 (PAR3) and annexin A1. Disruption of F-actin internalizes VE-cadherin and releases cPLA2α from the adhesion complex and Golgi apparatus. Finally, depletion of either PAR3 or α-catenin promotes cPLA2α-dependent endothelial tubule formation. Thus a VE-cadherin–PAR3–α-catenin adhesion complex regulates cPLA2α recruitment to the Golgi apparatus, with functional consequences for vascular physiology.
Axonal and dendritic synaptotagmin isoforms revealed by a pHluorin-syt functional screen
Authors: Dean Camin , Dunning F. Mark , Liu Huisheng , Bomba-Warczak Ewa , Martens Henrik , Bharat Vinita , Ahmed Saheeb , Chapman Edwin R.
Published: March 2012

The synaptotagmins (syts) are a family of molecules that regulate membrane fusion. There are 17 mammalian syt isoforms, most of which are expressed in the brain. However, little is known regarding the subcellular location and function of the majority of these syts in neurons, largely due to a lack of isoform-specific antibodies. Here we generated pHluorin-syt constructs harboring a luminal domain pH sensor, which reports localization, pH of organelles to which syts are targeted, and the kinetics and sites of exocytosis and endocytosis. Of interest, only syt-1 and 2 are targeted to synaptic vesicles, whereas other isoforms selectively recycle in dendrites (syt-3 and 11), axons (syt-5, 7, 10, and 17), or both axons and dendrites (syt-4, 6, 9, and 12), where they undergo exocytosis and endocytosis with distinctive kinetics. Hence most syt isoforms localize to distinct secretory organelles in both axons and dendrites and may regulate neuropeptide/neurotrophin release to modulate neuronal function.
Localized accumulation of tubulin during semi-open mitosis in theCaenorhabditis elegansembryo
Authors: Hayashi Hanako , Kimura Kenji , Kimura Akatsuki
Published: March 2012

The assembly of microtubules inside the cell is controlled both spatially and temporally. During mitosis, microtubule assembly must be activated locally at the nascent spindle region for mitotic spindle assembly to occur efficiently. In this paper, we report that mitotic spindle components, such as free tubulin subunits, accumulated in the nascent spindle region, independent of spindle formation in the Caenorhabditis elegans embryo. This accumulation coincided with nuclear envelope permeabilization, suggesting that permeabilization might trigger the accumulation. When permeabilization was induced earlier by knockdown of lamin, tubulin also accumulated earlier. The boundaries of the region of accumulation coincided with the remnant nuclear envelope, which remains after nuclear envelope breakdown in cells that undergo semi-open mitosis, such as those of C. elegans. Ran, a small GTPase protein, was required for tubulin accumulation. Fluorescence recovery after photobleaching analysis revealed that the accumulation was accompanied by an increase in the immobile fraction of free tubulin inside the remnant nuclear envelope. We propose that this newly identified mechanism of accumulation of free tubulin—and probably of other molecules—at the nascent spindle region contributes to efficient assembly of the mitotic spindle in the C. elegans embryo.
Molecular motor function in axonal transport in vivo probed by genetic and computational analysis inDrosophila
Authors: Reis Gerald F. , Yang Ge , Szpankowski Lukasz , Weaver Carole , Shah Sameer B. , Robinson John T. , Hays Thomas S. , Danuser Gaudenz , Goldstein Lawrence S. B.
Published: March 2012

Bidirectional axonal transport driven by kinesin and dynein along microtubules is critical to neuronal viability and function. To evaluate axonal transport mechanisms, we developed a high-resolution imaging system to track the movement of amyloid precursor protein (APP) vesicles in Drosophila segmental nerve axons. Computational analyses of a large number of moving vesicles in defined genetic backgrounds with partial reduction or overexpression of motor proteins enabled us to test with high precision existing and new models of motor activity and coordination in vivo. We discovered several previously unknown features of vesicle movement, including a surprising dependence of anterograde APP vesicle movement velocity on the amount of kinesin-1. This finding is largely incompatible with the biophysical properties of kinesin-1 derived from in vitro analyses. Our data also suggest kinesin-1 and cytoplasmic dynein motors assemble in stable mixtures on APP vesicles and their direction and velocity are controlled at least in part by dynein intermediate chain.
The apoptotic engulfment protein Ced-6 participates in clathrin-mediated yolk uptake inDrosophilaegg chambers
Authors: Jha Anupma , Watkins Simon C. , Traub Linton M.
Published: March 2012

Clathrin-mediated endocytosis and phagocytosis are both selective surface internalization processes but have little known mechanistic similarity or interdependence. Here we show that the phosphotyrosine-binding (PTB) domain protein Ced-6, a well-established phagocytosis component that operates as a transducer of so-called “eat-me” signals during engulfment of apoptotic cells and microorganisms, is expressed in the female Drosophila germline and that Ced-6 expression correlates with ovarian follicle development. Ced-6 exhibits all the known biochemical properties of a clathrin-associated sorting protein, yet ced-6–null flies are semifertile despite massive accumulation of soluble yolk precursors in the hemolymph. This is because redundant sorting signals within the cytosolic domain of the Drosophila vitellogenin receptor Yolkless, a low density lipoprotein receptor superfamily member, occur; a functional atypical dileucine signal binds to the endocytic AP-2 clathrin adaptor directly. Nonetheless, the Ced-6 PTB domain specifically recognizes the noncanonical Yolkless FXNPXA sorting sequence and in HeLa cells promotes the rapid, clathrin-dependent uptake of a Yolkless chimera lacking the distal dileucine signal. Ced-6 thus operates in vivo as a clathrin adaptor. Because the human Ced-6 orthologue GULP similarly binds to clathrin machinery, localizes to cell surface clathrin-coated structures, and is enriched in placental clathrin-coated vesicles, new possibilities for Ced-6/Gulp operation during phagocytosis must be considered.
Evolutionary inaccuracy of pairwise structural alignments
Authors: Sadowski M. I. , Taylor W. R.
Published: March 2012

Motivation: Structural alignment methods are widely used to generate gold standard alignments for improving multiple sequence alignments and transferring functional annotations, as well as for assigning structural distances between proteins. However, the correctness of the alignments generated by these methods is difficult to assess objectively since little is known about the exact evolutionary history of most proteins. Since homology is an equivalence relation, an upper bound on alignment quality can be found by assessing the consistency of alignments. Measuring the consistency of current methods of structure alignment and determining the causes of inconsistencies can, therefore, provide information on the quality of current methods and suggest possibilities for further improvement.

Results: We analyze the self-consistency of seven widely-used structural alignment methods (SAP, TM-align, Fr-TM-align, MAMMOTH, DALI, CE and FATCAT) on a diverse, non-redundant set of 1863 domains from the SCOP database and demonstrate that even for relatively similar proteins the degree of inconsistency of the alignments on a residue level is high (30%). We further show that levels of consistency vary substantially between methods, with two methods (SAP and Fr-TM-align) producing more consistent alignments than the rest. Inconsistency is found to be higher near gaps and for proteins of low structural complexity, as well as for helices. The ability of the methods to identify good structural alignments is also assessed using geometric measures, for which FATCAT (flexible mode) is found to be the best performer despite being highly inconsistent. We conclude that there is substantial scope for improving the consistency of structural alignment methods.

Contact:  msadows@nimr.mrc.ac.uk

Supplementary information:  Supplementary data are available at Bioinformatics online.
AntigenMap 3D: an online antigenic cartography resource
Authors: Barnett J. Lamar , Yang Jialiang , Cai Zhipeng , Zhang Tong , Wan Xiu-Feng
Published: March 2012

Summary: Antigenic cartography is a useful technique to visualize and minimize errors in immunological data by projecting antigens to 2D or 3D cartography. However, a 2D cartography may not be sufficient to capture the antigenic relationship from high-dimensional immunological data. AntigenMap 3D presents an online, interactive, and robust 3D antigenic cartography construction and visualization resource. AntigenMap 3D can be applied to identify antigenic variants and vaccine strain candidates for pathogens with rapid antigenic variations, such as influenza A virus.

Availability and implementation:  http://sysbio.cvm.msstate.edu/AntigenMap3D

Contact:  wan@cvm.msstate.edu; wanhenry@yahoo.com
Vaxfectin-adjuvanted plasmid DNA vaccine improves protection and immunogenicity in a murine model of genital herpes infection
Authors: Shlapobersky Mark , Marshak Joshua O. , Dong Lichun , Huang Meei-li , Wei Qun , Chu Alice , Rolland Alain , Sullivan Sean , Koelle David M.
Published: March 2012

The herpes simplex type 2 (HSV-2) envelope glycoprotein (gD2) was evaluated as a potential antigen candidate for a plasmid DNA (pDNA)-based HSV-2 vaccine. The pDNA was formulated with Vaxfectin, a cationic lipid-based adjuvant, and tested in a murine HSV-2 lethal challenge model. gD2 was expressed as full-length (FL) and secreted (S) gD2 forms. A 0.1 µg pDNA dose was tested to distinguish treatment conditions for survival and a 100 µg pDNA dose was tested to distinguish treatment conditions for reduction in vaginal and latent HSV-2 copies. Vaxfectin-formulated gD2 pDNA significantly increased serum IgG titres and survival for both FL gD2 and S gD2 compared with gD2 pDNA alone. Mice immunized with FL gD2 formulated with Vaxfectin showed reduction in vaginal and dorsal root ganglia (DRG) HSV-2 copies. The stringency of this protection was further evaluated by testing Vaxfectin-formulated FL gD2 pDNA at a high 500 LD50inoculum. At this high viral challenge, the 0.1 µg dose of FL gD2 Vaxfectin-formulated pDNA yielded 80 % survival compared with no survival for FL gD2 pDNA alone. Vaxfectin-formulated FL gD2 pDNA, administered at a 100 µg pDNA dose, significantly reduced HSV-2 DNA copy number, compared with FL gD2 DNA alone. In addition, 40 % of mice vaccinated with adjuvanted FL pDNA had no detectable HSV-2 viral genomes in the DRG, whereas all mice vaccinated with gD2 pDNA alone were positive for HSV-2 viral genomes. These results show the potential contribution of Vaxfectin-gD2 pDNA to a future multivalent HSV-2 vaccine.
The origin, global distribution, and functional impact of the human 8p23 inversion polymorphism
Authors: Salm Maximilian P.A. , Horswell Stuart D. , Hutchison Claire E. , Speedy Helen E. , Yang Xia , Liang Liming , Schadt Eric E. , Cookson William O. , Wierzbicki Anthony S. , Naoumova Rossi P. , Shoulders Carol C.
Published: March 2012

Genomic inversions are an increasingly recognized source of genetic variation. However, a lack of reliable high-throughput genotyping assays for these structures has precluded a full understanding of an inversion's phylogenetic, phenotypic, and population genetic properties. We characterize these properties for one of the largest polymorphic inversions in man (the ∼4.5-Mb 8p23.1 inversion), a structure that encompasses numerous signals of natural selection and disease association. We developed and validated a flexible bioinformatics tool that utilizes SNP data to enable accurate, high-throughput genotyping of the 8p23.1 inversion. This tool was applied retrospectively to diverse genome-wide data sets, revealing significant population stratification that largely follows a clinal “serial founder effect” distribution model. Phylogenetic analyses establish the inversion's ancestral origin within the Homo lineage, indicating that 8p23.1 inversion has occurred independently in the Pan lineage. The human inversion breakpoint was localized to an inverted pair of human endogenous retrovirus elements within the large, flanking low-copy repeats; experimental validation of this breakpoint confirmed these elements as the likely intermediary substrates that sponsored inversion formation. In five data sets, mRNA levels of disease-associated genes were robustly associated with inversion genotype. Moreover, a haplotype associated with systemic lupus erythematosus was restricted to the derived inversion state. We conclude that the 8p23.1 inversion is an evolutionarily dynamic structure that can now be accommodated into the understanding of human genetic and phenotypic diversity.
The Autoregulation Gene SUNN Mediates Changes in Root Organ Formation in Response to Nitrogen through Alteration of Shoot-to-Root Auxin Transport
Authors: Jin Jian , Watt Michelle , Mathesius Ulrike
Published: March 2012

We tested whether a gene regulating nodule number in Medicago truncatula, Super Numeric Nodules (SUNN ), is involved in root architecture responses to carbon (C) and nitrogen (N) and whether this is mediated by changes in shoot-to-root auxin transport. Nodules and lateral roots are root organs that are under the control of nutrient supply, but how their architecture is regulated in response to nutrients is unclear. We treated wild-type and sunn-1 seedlings with four combinations of low or increased N (as nitrate) and C (as CO2) and determined responses in C/N partitioning, plant growth, root and nodule density, and changes in auxin transport. In both genotypes, nodule density was negatively correlated with tissue N concentration, while only the wild type showed significant correlations between N concentration and lateral root density. Shoot-to-root auxin transport was negatively correlated with shoot N concentration in the wild type but not in the sunn-1 mutant. In addition, the ability of rhizobia to alter auxin transport depended on N and C treatment as well as the SUNN gene. Nodule and lateral root densities were negatively correlated with auxin transport in the wild type but not in the sunn-1 mutant. Our results suggest that SUNN is required for the modulation of shoot-to-root auxin transport in response to altered N tissue concentrations in the absence of rhizobia and that this controls lateral root density in response to N. The control of nodule density in response to N is more likely to occur locally in the root.
Examining Market Information and Brand Equity Through Resource‐Advantage Theory: A Carrier Perspective
Authors: Golicic Susan L. , Fugate Brian S. , Davis Donna F.
Published: March 2012

To survive in this challenging economic environment, transportation providers must differentiate themselves in the eyes of current and potential customers. Consequently, they are seeking to develop superior resources that allow them to build greater awareness of and distinctive images for their brands. Those that are successful achieve higher levels of brand equity and, ultimately, positions of competitive advantage in the logistics services industry. This research applies resource‐advantage theory to investigate the role of market information in creating an informational advantage to build brand equity for transportation providers. Results from a survey of motor carriers indicate that informational advantage mediates the impact of market information resources on the levels of brand image and brand awareness, two dimensions of a firm’s brand equity.
Enhancing Security Through Efficiency Focus—Insights From a Multiple Stakeholder Pilot Implementation
Authors: Sternberg Henrik , Nyquist Camilla , Nilsson Fredrik
Published: March 2012

Efficiency and security are often regarded as opposing factors in transport operations, with increased security causing decreased efficiency. The use of information technology holds the promise of enabling improved efficiency in freight transport operations and this article suggests and elaborates on the proposition that “An increased focus on efficiency will result in improved security for carrier operations.” The research for this article involved a literature review, the collection of empirical data through one in‐depth case study, and elaboration on a proposition through a field pilot implementation. The selected focus was carrier operations in connection with port terminals carrying out RoRo operations on trailers. The article explores and describes how measures to increase efficiency result in increased security.