bluuebunny/crossref_metadata_2025 huggingface dataset:
The Wrangel Island Polynya in early summer: Trends and relationships to other polynyas and the Beaufort Sea High
Authors: Moore G. W. K. , Pickart R. S.
Published: February 2012

Polynyas, regions of reduced sea ice concentration relative to their surroundings, are important features of the polar climate system in which enhanced fluxes of heat, moisture, and momentum can occur between the atmosphere and ocean. As such, they play a significant role in many atmospheric, oceanographic and biological processes. There are concerns that in a warming climate, in which there is a trend towards a reduction in sea ice cover, that the location, size and duration of many polynyas may change resulting in climatological and ecological impacts. In this paper, we identify an early summer manifestation of the Wrangel Island polynya that forms in the western Chuckchi Sea. We show that over the past 30 years there has been an increased frequency of occurrence as well as a doubling in the size of the polynya. The polynya is shown to form when there is an enhanced easterly flow over the Chukchi Sea that is associated with an anomalously intense Beaufort Sea High (BSH), a closed anti‐cyclonic atmospheric circulation that forms over the Beaufort Sea. We also show that there has been a concomitant trend towards a more intense BSH over the same time period and we propose that this trend is responsible for the observed changes in the Wrangel Island polynya. Given its large and increasing size, the early summer polynya may also play an important and unaccounted role in the physical and biological oceanography of the western Chukchi Sea.
Ambient‐field Green's functions from asynchronous seismic observations
Authors: Ma Shuo , Beroza Gregory C.
Published: February 2012

We demonstrate that the coda of station‐to‐station Green's functions extracted from the ambient seismic field in southern California reach stability in the microseism band (5–10 s) after correlating six months of noise data. The coda stability makes it possible to retrieve Green's functions between stations that operate asynchronously through scattered waves as recorded by a network of fiducial stations. The Green's functions extracted from asynchronous and synchronous data have comparable quality as long as stable virtual coda are used, and both show good convergence to the Green's functions extracted from 1 year of seismic noise with ∼50 fiducial stations. This approach suggests that Green's functions can be extracted across seismic stations regardless of whether or not they are occupied simultaneously, which raises the prospect of a new mode for seismic experiments that seek to constrain Earth structure.
Global network of slow solar wind
Authors: Crooker N. U. , Antiochos S. K. , Zhao X. , Neugebauer M.
Published: February 2012

The streamer belt region surrounding the heliospheric current sheet (HCS) is generally treated as the primary or sole source of the slow solar wind. Synoptic maps of solar wind speed predicted by the Wang‐Sheeley‐Arge model during selected periods of solar cycle 23, however, show many areas of slow wind displaced from the streamer belt. These areas commonly have the form of an arc that is connected to the streamer belt at both ends. The arcs mark the boundaries between fields emanating from different coronal holes of the same polarity and thus trace the paths of belts of pseudostreamers, i.e., unipolar streamers that form over double arcades and lack current sheets. The arc pattern is consistent with the predicted topological mapping of the narrow open corridor or singular separator line that must connect the holes and, thus, consistent with the separatrix‐web model of the slow solar wind. Near solar maximum, pseudostreamer belts stray far from the HCS‐associated streamer belt and, together with it, form a global‐wide web of slow wind. Recognition of pseudostreamer belts as prominent sources of slow wind provides a new template for understanding solar wind stream structure, especially near solar maximum.
Modeling winter circulation under landfast ice: The interaction of winds with landfast ice
Authors: Kasper Jeremy L. , Weingartner Thomas J.
Published: February 2012

Idealized models and a simple vertically averaged vorticity equation illustrate the effects of an upwelling favorable wind and a spatially variable landfast ice cover on the circulation beneath landfast ice. For the case of no along‐shore variations in ice, upwelling favorable winds seaward of the ice edge result in vortex squashing beneath the landfast ice leading to (1) large decreases in coastal and ice edge sea levels, (2) cross‐shore sea level slopes and weak (<∼.05 m s−1) under‐ice currents flowing upwind, (3) strong downwind ice edge jets, and (4) offshore transport in the under‐ice and bottom boundary layers of the landfast ice zone. The upwind under‐ice current accelerates quickly within 2–4 days and then slows as cross‐shore transport gradually decreases the cross‐shore sea level slope. Near the ice edge, bottom boundary layer convergence produces ice edge upwelling. Cross‐ice edge exchanges occur in the surface and above the bottom boundary layer and reduce the under‐ice shelf volume by 15% in 10 days. Under‐ice along‐shore pressure gradients established by along‐ and cross‐shore variations in ice width and/or under‐ice friction alter this basic circulation pattern. For a landfast ice zone of finite width and length, upwelling‐favorable winds blowing seaward of and transverse to the ice boundaries induce downwind flow beneath the ice and generate vorticity waves that propagate along‐shore in the Kelvin wave direction. Our results imply that landfast ice dynamics, not included explicitly herein, can effectively convert the long‐wavelength forcing of the wind into shorter‐scale ocean motions beneath the landfast ice.
Rhizoplegma boreale (Radiolaria): A tracer for mesoscale eddies from coastal areas
Authors: Ikenoue Takahito , Ueno Hiromichi , Takahashi Kozo
Published: February 2012

The impact of mesoscale eddies on the production of radiolarian species Rhizoplegma boreale in the central subarctic Pacific was investigated through analysis of sinking particle fluxes collected using sediment‐trap and altimetry data from satellite observations. Altimetry observations provided the locations of mesoscale eddies in time and space and indicated that mesoscale eddies propagating around sediment trap Station SA were closely related to the high R. boreale fluxes at the station. The mesoscale eddies likely provided the deep‐sea region of the central subarctic Pacific with coastal nutrient‐rich waters derived from the region around the Aleutian Islands, and influenced the productivity of microzooplankton groups at Station SA.
The Continual Intercomparison of Radiation Codes: Results from Phase I
Authors: Oreopoulos Lazaros , Mlawer Eli , Delamere Jennifer , Shippert Timothy , Cole Jason , Fomin Boris , Iacono Michael , Jin Zhonghai , Li Jiangnan , Manners James , Räisänen Petri , Rose Fred , Zhang Yuanchong , Wilson Michael J. , Rossow William B.
Published: February 2012

We present results from Phase I of the Continual Intercomparison of Radiation Codes (CIRC), intended as an evolving and regularly updated reference source for evaluation of radiative transfer (RT) codes used in global climate models and other atmospheric applications. CIRC differs from previous intercomparisons in that it relies on an observationally validated catalog of cases. The seven CIRC Phase I baseline cases, five cloud free and two with overcast liquid clouds, are built around observations by the Atmospheric Radiation Measurements program that satisfy the goals of Phase I, namely, to examine RT model performance in realistic, yet not overly complex, atmospheric conditions. Besides the seven baseline cases, additional idealized “subcases” are also employed to facilitate interpretation of model errors. In addition to quantifying individual model performance with respect to reference line‐by‐line calculations, we also highlight RT code behavior for conditions of doubled CO2, issues arising from spectral specification of surface albedo, and the impact of cloud scattering in the thermal infrared. Our analysis suggests that improvements in the calculation of diffuse shortwave flux, shortwave absorption, and shortwave CO2 forcing as well as in the treatment of spectral surface albedo should be considered for many RT codes. On the other hand, longwave calculations are generally in agreement with the reference results. By expanding the range of conditions under which participating codes are tested, future CIRC phases will hopefully allow even more rigorous examination of RT codes.
Arctic low cloud changes as observed by MISR and CALIOP: Implication for the enhanced autumnal warming and sea ice loss
Authors: Wu Dong L. , Lee Jae N.
Published: February 2012

Retreat of Arctic sea ice extent has led to more evaporation over open water in summer and subsequent cloud changes in autumn. Studying recent satellite cloud data over the Arctic Ocean, we find that low (0.5–2 km) cloud cover in October has been increasing significantly during 2000–2010 over the Beaufort and East Siberian Sea (BESS). This change is consistent with the expected boundary layer cloud response to the increasing Arctic evaporation accumulated during summer. Because low clouds have a net warming effect at the surface, October cloud increases may be responsible for the enhanced autumnal warming in surface air temperature, which effectively prolong the melt season and lead to a positive feedback to Arctic sea ice loss. Thus, the new satellite observations provide a critical support for the hypothesized positive feedback involving interactions between boundary layer cloud, water vapor, temperature, and sea ice in the Arctic Ocean.
Time‐series analysis of high‐resolution ebullition fluxes from a stratified, freshwater lake
Authors: Varadharajan Charuleka , Hemond Harold F.
Published: February 2012

Freshwater lakes can emit significant quantities of methane to the atmosphere by bubbling. The high spatial and temporal heterogeneity of ebullition, combined with a lack of high‐resolution field measurements, has made it difficult to accurately estimate methane fluxes or determine the underlying mechanisms for bubble release. We use a high‐temporal resolution data set of ebullitive fluxes from the eutrophic Upper Mystic Lake, Massachusetts to understand the triggers that lead to bubbling from submerged sediments. A wavelet approach is introduced to detect ebullition events for multiple time‐scales, and is complemented with traditional statistical methods for data analyses. We show that bubble release from lake sediments occurred synchronously at several sites, and was closely associated with small, aperiodic drops in total hydrostatic pressure. Such results are essential to constrain mechanistic models and to design future measurement schemes, particularly with respect to the temporal scales that are needed to accurately observe and quantify ebullition in aquatic ecosystems.
Sea‐surface temperature records of Termination 1 in the Gulf of California: Challenges for seasonal and interannual analogues of tropical Pacific climate change
Authors: McClymont Erin L. , Ganeshram Raja S. , Pichevin Laetitia E. , Talbot Helen M. , van Dongen Bart E. , Thunell Robert C. , Haywood Alan M. , Singarayer Joy S. , Valdes Paul J.
Published: February 2012

Centennial‐scale records of sea‐surface temperature and opal composition spanning the Last Glacial Maximum and Termination 1 (circa 25–6 ka) are presented here from Guaymas Basin in the Gulf of California. Through the application of two organic geochemistry proxies, the U37K′index and the TEX86Hindex, we present evidence for rapid, stepped changes in temperatures during deglaciation. These occur in both temperature proxies at 13 ka (∼3°C increase in 270 years), 10.0 ka (∼2°C decrease over ∼250 years) and at 8.2 ka (3°C increase in <200 years). An additional rapid warming step is also observed in TEX86Hat 11.5 ka. In comparing the two temperature proxies and opal content, we consider the potential for upwelling intensity to be recorded and link this millennial‐scale variability to shifting Intertropical Convergence Zone position and variations in the strength of the Subtropical High. The onset of the deglacial warming from 17 to 18 ka is comparable to a “southern hemisphere” signal, although the opal record mimics the ice‐rafting events of the north Atlantic (Heinrich events). Neither the modern seasonal cycle nor El Niño/Southern Oscillation patterns provide valid analogues for the trends we observe in comparison with other regional records. Fully coupled climate model simulations confirm this result, and in combination we question whether the seasonal or interannual climate variations of the modern climate are valid analogues for the glacial and deglacial tropical Pacific.
Estimation of radio refractivity using a multiple angle clutter model
Authors: Karimian Ali , Yardim Caglar , Hodgkiss William S. , Gerstoft Peter , Barrios Amalia E.
Published: February 2012

The common occurrence of a marine boundary layer in coastal regions can affect radio wave propagation significantly. Refractivity from clutter (RFC) techniques are aimed at estimating the refractivity profile of the ambient environment based on the received radar clutter. While most previous RFC work has not considered the dependence of RFC inversions on a variable grazing angle, this study investigates incorporation of the grazing angle information into the clutter model. A newly proposed clutter model based on multiple incident angles at each range is used here. The inversion performance of the multiple angle clutter model is compared to that of other models. Synthetic examples of a range‐independent surface‐based duct and a range‐dependent evaporation duct are investigated for a S‐band radar. Finally, a comparison of inversions on one set of experimental measurements from the SPANDAR 1998 data set is provided, using single and multiple grazing angle clutter models, and the previously used model based on grazing angle independent sea surface reflectivity.
Determination of and evidence for non‐core‐shell structure of particles containing black carbon using the Single‐Particle Soot Photometer (SP2)
Authors: Sedlacek Arthur J. , Lewis Ernie R. , Kleinman Lawrence , Xu Jianzhong , Zhang Qi
Published: February 2012

The large uncertainty associated with black carbon (BC) direct forcing is due, in part, to the dependence of light absorption of BC‐containing particles on the position of the BC within the particle. It is predicted that this absorption will be greatest for an idealized core‐shell configuration in which the BC is a sphere at the center of the particle whereas much less absorption should be observed for particles in which the BC is located near or on the surface. Such microphysical information on BC‐containing particles has previously been provided only by labor‐intensive microscopy techniques, thus often requiring that climate modelers make assumptions about the location of the BC within the particle that are based more on mathematical simplicity than physical reality. The present paper describes a novel analysis method that utilizes the temporal behavior of the scattering and incandescence signals from individual particles containing refractory BC (rBC) measured by the Single‐Particle Soot Photometer (SP2) to distinguish particles with rBC near the surface from those that have structures more closely resembling the core‐shell configuration. This approach permits collection of a high‐time‐resolution data set of the fraction of rBC‐containing particles with rBC near the surface. By application of this method to a plume containing tracers for biomass burning, it was determined that this fraction was greater than 60%. Such a data set will not only provide previously unavailable information to the climate modeling community, allowing greater accuracy in calculating rBC radiative forcing, but also will yield insight into aerosol processes.
Deletion of the trpc4 gene and its role in simple and complex strategic learning
Authors: Collins Marissa , Drish Abby , Swenson Laura , Ostertag Eric , Klipec William , Nguyen Phuong , Deeney Bridget , Williamson Claire , Wenzel Kami , Cooper Donald , Stumme Jessica
Published: February 2012

The TRPC4 ion channel is expressed extensively in corticolimbic and a subpopulation of midbrain dopamine neurons. While TRPC4 knockout (KO) rats exhibit reduced sociability and social exploration, little is known about the role of TRPC4 in motivation and learning. To identify a function for TRPC4 channels in learning processes  we tested TRPC4 KO and normal wild type (WT) rats. TRPC4 KO and WT rats exhibited no differences in Y--maze learning or simple discrimination learning. Furthermore, on a more complex serial reversal shift task designed  to assess strategic learning where the reward and non--reward cues were repeatedly reversed between training sessions both TRPC4 KO and WT rats   performed equally well. Finally, we found no   performance differences when using a conditional reversal shift task where a tone signals the reversal of reward and non-reward cues within sessions. These data suggest that although TRPC4 channels may play a role in social interaction/anxiety  they exert a minimal role in simple and complex strategic learning.
Grid Potential Analysis and Docking Studies on a Dataset of N-Arylsulfonyl-3-AcetylIndoles as Anti-HIV Agent
Authors: Kumar Surendra , Tiwari Meena
Published: February 2012

A grid potential analysis employing the AutoGPA module in MOE2009.10 was performed on a dataset of 42 molecules of N-arylsulfonyl-3-acetylindoles as anti-HIV agent. The molecular docking simulations were also employed to position the inhibitors to their binding site to determine the most appropriate binding mode for different conformations of molecule. The uniqueness of AutoGPA module is that it automatically builds the 3D-QSAR model on the pharmacophore based molecular alignment. The best AutoGPA 3D-QSAR model obtained in the present study gives the cross-validated q2 value of 0.588 and r2pred value of 0.701 among the fifty six 3D-QSAR model developed. Furthermore, the steric and electrostatic contour maps for AutoGPA model along with the 3D structure of protein (binding residue of active site) inlaid were obtained to better understand the structural requirements against HIV and interaction between binding residues of protein and inhibitors. The study shows that hydrophobic and hydrogen bonding potential groups are favorable for optimization of parent nucleus for better activity.
Longer-acting and highly potent chimaeric inhibitors of excessive exocytosis created with domains from botulinum neurotoxin A and B
Authors: Wang Jiafu , Zurawski Tomas H. , Bodeker MacDara O. , Meng Jianghui , Boddul Sanjay , Aoki K. Roger , Dolly J. Oliver
Published: February 2012

Various human neurogenic hyper-excitability disorders are successfully treated with type A or B BoNT (botulinum neurotoxin). The BoNT/A complex is widely used because of its longer-lasting benefits; also, autonomic side-effects are more often reported for BoNT/B. To establish if this distinct effect of BoNT/B could be exploited therapeutically, BoNT/A was modified so that it would bind the more abundant BoNT/B acceptor in rodents while retaining its desirable persistent action. The advantageous protease and translocation domain of BoNT/A were recombinantly combined with the acceptor-binding moiety of type B [HC/B (C-terminal half of BoNT/B heavy chain)], creating the chimaera AB. This purified protein bound the BoNT/B acceptor, displayed enhanced capability relative to type A for intraneuronally delivering its protease, cleaved SNAP-25 (synaptosome-associated protein of 25 kDa) and induced a more prolonged neuromuscular paralysis than BoNT/A in mice. The BA chimaera, generated by substituting HC/A (C-terminal half of BoNT/A heavy chain) into BoNT/B, exhibited an extremely high specific activity, delivered the BoNT/B protease via the BoNT/A acceptor into neurons, or fibroblast-like synoviocytes that lack SNAP-25, cleaving the requisite isoforms of VAMP (vesicle-associated membrane protein). Both chimaeras inhibited neurotransmission in murine bladder smooth muscle. BA has the unique ability to reduce exocytosis from non-neuronal cells expressing the BoNT/A-acceptor and utilising VAMP, but not SNAP-25, in exocytosis.
Relationship between TWIST expression and epithelial—mesenchymal transition of oesophageal squamous cell carcinoma
Authors: Gao Yuan , Xuan Xiao‐Yan , Zhang Hong‐Yan , Wang Feng , Zeng Qing‐Ru , Wang Zhi‐Qiang , Li Shan‐Shan
Published: February 2012

We have investigated mRNA and protein expression of TWIST, Vimentin and E‐cadherin in ESCC (oesophageal squamous cell carcinoma) and explored their relationship with tumour's infiltration and metastasis. RT—PCR (reverse transcriptase—PCR) was used to evaluate mRNA expression of TWIST, E‐cadherin and Vimentin in 40 cases of ESCC. The protein expression of the genes was examined by immunohistochemical staining in each specimen. Expression of TWIST, E‐cadherin and Vimentin mRNA and protein with clinicopathologic parameters were analysed. mRNAs of TWIST, Vimentin and E‐cadherin were expressed in 75, 55 and 35% respectively of ESCC, i.e. significantly different from that in normal oesophageal mucosa (15, 0 and 85% respectively; P<0.01). In ESCC with LN (lymph node) metastasis, expression of TWIST and Vimentin mRNA, but not E‐cadherin mRNA was significantly higher (100 and 83%) than in ESCC without LN metastasis (64 and 43%, P=0.018) respectively. Levels of mRNA expression of the 3 genes followed similar patterns to their above‐mentioned frequencies. Protein expression of TWIST, E‐cadherin and Vimentin were observed in 70, 35 and 50% respectively of ESCC, which were significantly different from normal mucosa (15, 80 and 0%; P<0.001). In ESCC with LN metastasis, protein expression of TWIST and Vimentin, but not E‐cadherin, were significantly higher (100 and 75%) than in ESCC without LN metastasis (61 and 39%). Protein expression of TWIST was positively correlated with Vimentin (r=0.327, P=0.039), but negatively correlated with E‐cadherin (r= −0.633, P=0.000). Thus, both mRNAs and proteins of TWIST and Vimentin were significantly overexpressed in ESCC, especially ESCC with LN metastasis. The mRNA and protein of E‐cadherin were down‐regulated in ESCC. These results suggest potential roles of TWIST as the promoter of tumour invasion and metastasis associated with down‐regulation of E‐cadherin.
Improvement of the nuclear transfer efficiency by using the same genetic background of recipient oocytes as the somatic donor cells in goats
Authors: Liu Hai‐jun , Xue Jun , Li Kui , Ying Zheng‐Zhou , Zheng Zi , Wang Ru
Published: February 2012

We have compared the effect of the genetic background of recipient oocytes on the in vitro and in vivo development of nuclear transfer reconstructed embryos in goats. Adult fibroblast cells from Boer goats were used as donor cells, and recipient oocytes were obtained from Boer goats and Boer cross‐breeds (Boer♂ × Huanghuai♀). Nuclear transfer reconstructed embryos were cultured in vitro, or transferred into recipient goats. The mitochondrial origin of 2 cloned Boer goats was investigated by analysing the D‐loop region based on polymorphisms via DNA sequencing. There was no significant difference in the fusion rate and cleavage rate of reconstructed embryos (P>0.05), when using Boer and cross‐breeding goat oocytes as recipient cytoplast respectively. However, in vitro morula development of reconstructed embryos from Boer oocytes was significantly higher than that of cross‐breeding embryos (34.1% versus 19.1%, P<0.05). There was no significant difference in the rate of pregnancy and foetus loss between the 2 breeds. However, the live‐birth rate was significantly higher with Boer goat oocyte recipients than the cross‐breeds (3.1% versus 0.8%, P<0.05). Mitochondrial analysis showed that the 2 cloned goats were similar to their respective oocyte donor goats, and significantly different from the nucleus donor. In conclusion, genetic background of recipient oocytes affected in vitro and in vivo development of reconstructed embryos, with the homologous background of cytoplast and nuclear donor benefiting development of reconstructed embryos. The mitochondrial origin of the 2 cloned Boer goats came from recipient oocytes, not donors.
Bilingual Children With Nonsyndromic Cleft Lip and/or Palate: Language and Memory Skills
Authors: Young Selena Ee-Li , Purcell Alison Anne , Ballard Kirrie Jane , Rickard Liow Susan Jane , Da Silva Ramos Sara , Heard Robert
Published: February 2012

Purpose

Research shows that monolingual children with cleft lip and/or palate (CLP) have a higher incidence of cognitive-linguistic deficits, but it is not clear whether bilingual preschool children with CLP are especially vulnerable because they need to acquire 2 languages. We tested the hypothesis that bilingual children with CLP score lower than bilingual children with typical development (TD) on receptive vocabulary, verbal memory, and visuospatial memory.

Method

Participants were 86 bilingual CLP children and 100 TD children 3–6 years of age, dominant in English or Mandarin. Each child completed assessments of English and Mandarin vocabulary, verbal and visuospatial short-term and working memory, hearing, and articulation.

Results

With analysis of covariance controlling for age and dominant language, no group differences were found between the CLP and TD bilingual children, although a correlational analysis indicated discrepancies in the relationship between variables.

Conclusions

The findings do not support the hypothesis that preschool children with CLP score lower than preschool children with TD on receptive vocabulary and memory measures. Longitudinal research examining literacy skill development is needed to establish whether the deficits reported for school-age monolingual children with CLP become more obvious in bilingual children in later years, especially when the medium of instruction is the child’s nondominant language.
Chemical pressure and electron doping effects in SrPd2Ge2 single crystals
Authors: Sung N. H. , Roh C. J. , Kang B. Y. , Cho B. K.
Published: February 2012

Sr(Pd1−xPtx)2Ge2, SrPd2(Ge1−xSix)2, and Sr(Pd1−xAgx)2Ge2 single crystals were synthesized using a self−flux method to examine the effects of chemical pressure and electron doping on the superconductivity of SrPd2Ge2 superconductors. The highest enhanced superconducting phase transition temperature (Tc) was 3.26 K, which was observed in Sr(Pd1−xPtx)2Ge2 at x = 0.0618. In contrast, the Tc of SrPd2(Ge1−xSix)2 remained nearly constant as the amount of dopant increased, and electron doping in Sr(Pd1−xAgx)2Ge2 suppressed the superconductivity. In addition, for x ≤ 0.0657, the superconducting upper critical field (Hc2) increased linearly with an increase in the value of x in Sr(Pd1−xPtx)2Ge2, while Hc2 remained nearly constant in SrPd2(Ge1−xSix)2. The results of the present study were compared with those of pnictide compounds with a ThCr2Si2−type structure.
Impacts of enhanced electronic correlation in anion p-orbitals on electronic structure and magnetic properties of nitrogen or carbon doped zinc oxide
Authors: Zhang Yao-fang , Liu Hong , Wu Jian , Zuo Xu
Published: February 2012

The electronic structure and magnetic properties of nitrogen or carbon doped zinc oxide are studied by using ab initio calculation, where the electronic correlation in anion p-orbitals are enhanced by adding the on-site Coulomb repulsion. The calculation shows that the enhanced electronic correlation can result in an insulating density of state and negligible exchange coupling beyond the next nearest neighbor, both of which question the possibility of hole-induced ferromagnetism in these materials.
Dependence of spin-transfer switching characteristics in magnetic tunnel junctions with synthetic free layers on coupling strength
Authors: Nishimura Masayuki , Oogane Mikihiko , Naganuma Hiroshi , Inami Nobuhito , Morita Tadashi , Ando Yasuo
Published: February 2012

Dependence of spin-transfer switching characteristics on the interlayer exchange coupling strength in the MTJs with synthetic free layers of Co90Fe10/Ru/Co40Fe40B20 with strong coupling strength was investigated. In the MTJ with the relatively weakly coupled synthetic ferrimagnetic free layer, larger thermal stability (Δ0) and lower intrinsic critical current density (Jc0) than those of the MTJ with the single free layer were observed. Meanwhile, in the MTJs with the strongly coupled synthetic ferri- or ferromagnetic free layers, very large Δ0 and high Jc0 were observed probably due to high effective magnetic energy barrier. It was found that the MTJ with the relatively weakly coupled synthetic ferrimagnetic free layer is suitable for the STTRAM application.
Effects of nitrogen deficiency on the magnetostructural properties of antiperovskite manganese nitrides
Authors: Kasugai D. , Ozawa A. , Inagaki T. , Takenaka K.
Published: February 2012

Giant negative thermal expansion in antiperovskite manganese nitrides Mn3AN (A = Zn, Ga, etc.) is achieved by substituting Ge for A as a “relaxant” to the sharp volume change associated with the magnetic transition. We have studied the effects of nitrogen deficiency on the broadening of volume change. Although the broadening increases with decreasing nitrogen content for Mn3Cu0.5Ge0.5N1-δ, the sharp volume change is robust against nitrogen deficiency in Ge-free Mn3GaN1-δ. Nitrogen deficiency probably does not broaden the volume change by itself; rather it probably assists the broadening in conjunction with the Ge dopant. The origin of the broadening is discussed in terms of local lattice distortion of the Mn6N octahedra.
New magnetic configuration in paramagnetic phase of HoCo2
Authors: Bonilla C. M. , Calvo I. , Herrero-Albillos J. , Figueroa A. I. , Castan-Guerrero C. , Bartolomé J. , Rodriguez-Velamazan J. A. , Schmitz D. , Weschke E. , Paudyal D. , Pecharsky V. K. , Gschneidner K. A. , Bartolomé F. , García L. M.
Published: February 2012

X-ray magnetic circular dichroism (XMCD) measurements on HoCo2 reveal the inversion of Co moment at temperatures higher than the critical temperature, Tc, showing that the net magnetization under a field of the Ho and Co sublattices remain antiparallel even above Tc. The Ho moment also changes its orientation to align antiparallel to the applied field at high temperature giving rise to a new magnetic configuration in the paramagnetic regime. Transverse susceptibility (TS) and small angle neutron scattering (SANS) measurements performed above Tc indicate the existence of sizable magnetic short-range correlated regions in HoCo2. First principles calculations based on spin polarized local-density approximation, LSDA+U havebeen performed to obtain insights on the origin of the short-range correlated volume.
Structural and magnetic properties of Mn2+δTiSn
Authors: Kharel P. , Huh Y. , Shah V. R. , Li X. Z. , Al-Aqtash N. , Tarawneh K. , Krage E. S. , Sabirianov R. F. , Skomski R. , Sellmyer D. J.
Published: February 2012

The structural and magnetic properties of Mn2+δTiSn prepared by arc melting and annealing have been investigated. Structural studies show that the compound crystallizes in the hexagonal Ni3Sn-type structure with a = 5.70 Å and c = 4.55 Å. The phase stability of Mn2TiSn in the hexagonal structure is supported by the first-principle electronic structure calculations where the total energy per unit-cell volume in the hexagonal structure is smaller than that in the cubic structure. Field and temperature dependence of magnetization show that the sample is magnetically ordered with a Curie temperature around 400 K. The anisotropy energy calculated from the high-field data is 4.0 × 105 ergs/cm3 at 300 K but increases by a factor of two (8.6 × 105 ergs/cm3) as temperature decreases to 10 K. The observed magnetic properties are explained as the consequences of competing ferromagnetic and antiferromagnetic interactions between different magnetic sublattices.
A wavelet approach for the identification of surface cracks using current injection perturbation
Authors: Adly A. A. , Abd-El-Hafiz S. K.
Published: February 2012

The non-destructive identification of surface cracks in steel parts has always been an issue of great industrial interest. Among the non-destructive crack inspection approaches proposed in the past is field measurement resulting from impressed current crack perturbation. Obviously, crack detection becomes more challenging as the active sensor dimensions and/or surface clearance become large in comparison to the crack itself. In this paper, the wavelets approach is utilized in crack volume and location detection using impressed current differential measurements involving relatively large sensing elements. Detailed methodology and results demonstrating the advantages of the proposed approach are given in the paper.
Modeling the effects of nanosized precipitates on magnetic hysteresis and Barkhausen effect signal
Authors: Lo C. C. H.
Published: February 2012

A model has been developed for describing the effects of randomly distributed precipitates on magnetic hysteresis and Barkhausen emissions based on a hysteretic-stochastic process model of domain wall dynamics. The pinning of magnetic domain walls by spherical precipitates is described in terms of the pinning strength, which is proportional to the number density and cross-sectional area of the precipitates, and of the interaction range, which depends on the particle spacing and grain size. The model was used to simulate hysteresis loops and Barkhausen effect signals of a series of thermally aged FeCu samples with different number densities and sizes of Cu-rich precipitates. The linear dependence of the coercivity on the sample hardness was reproduced in the simulations. The rms values and pulse height distributions of the measured and modeled Barkhausen signals show similar dependence on the aging time, which can be interpreted by considering the effects of varying the precipitate size and spacing on the strength and interaction range of domain wall pinning.
Analytical magnetic torque calculations and experimental testing of radial flux permanent magnet-type eddy current brakes
Authors: Choi Jang-Young , Jang Seok-Myeong
Published: February 2012

This paper reports on analytical magnetic torque calculations and experimental tests of a radial flux permanent magnet (RFPM)-type eddy current brake (ECB). Analytical solutions for permanent magnet-generated magnetic fields that consider the eddy current reaction are obtained by using a magnetic vector potential and a two dimensional (2D) polar coordinate system. On the basis of these solutions, the analytical expressions for a magnetic torque are also derived. All analytical results are validated extensively by non-linear finite element calculations. In particular, magnetic torque measurements are obtained in tests to confirm the analyses. Finally, practical issues related to the analytical study of RFPM-type ECBs are fully discussed.
Density of states, magnetic and transport properties of Nd doped two dimensional perovskite compound Sr2CoO4
Authors: Yao Qiwen , Kimura Hideo , Wang X. L. , Konstantinov Kosta , Zhao Hongyang , Qiu Hai , Tanahashi Rumi , Ozawa Kiyoshi , Dou S. X.
Published: February 2012

Structures, transport, magnetic properties, and first principle calculation results will be reported for the two dimensional layered structured perovskite compounds Sr2-xNdxCoO4 (x = 0.5, 0.75, 1, 1.25). Structure refinement results revealed that these compounds crystallized in K2NiF4-type structures with space group I4/mmm. The temperature dependence of resistivity showed semiconductor like behavior for these samples. It was found that the lattice parameter c decreases as the doping level x increases. The compounds exhibited a paramagnetic to ferromagnetic transition at temperatures of about 170, 125 K for the x = 1 and 0.75 samples, respectively. The temperature dependence of resistivity for the samples can be well fitted by the 2D variable hoping (VRH) model ρ = ρo exp(T0/T)1/3 (where ρo is a material specific characteristic conductance, with unit Ω−1, T0 is a material specific characteristic temperature in K) over the whole measured temperature range. First principles calculations indicated that the Nd doped Sr2CoO4 compounds show high spin polarization.
Substrate effect on the resistive switching in BiFeO3 thin films
Authors: Shuai Yao , Ou Xin , Wu Chuangui , Zhang Wanli , Zhou Shengqiang , Bürger Danilo , Reuther Helfried , Slesazeck Stefan , Mikolajick Thomas , Helm Manfred , Schmidt Heidemarie
Published: February 2012

BiFeO3 thin films have been deposited on Pt/sapphire and Pt/Ti/SiO2/Si substrates with pulsed laser deposition using the same growth conditions. Au was sputtered as the top electrode. The microscopic structure of the thin film varies by changing the underlying substrate. Thin films on Pt/sapphire are not resistively switchable due to the formation of Schottky contacts at both the top and the bottom interfaces. However, thin films on Pt/Ti/SiO2/Si exhibit an obvious resistive switching behavior under forward bias. The conduction mechanisms in BiFeO3 thin films on Pt/sapphire and Pt/Ti/SiO2/Si substrates are discussed to understand the different resistive switching behaviors.
Thermoelectric efficiency of topological insulators in a magnetic field
Authors: Tretiakov O. A. , Abanov Ar. , Sinova Jairo
Published: February 2012

We study the thermoelectric properties of three-dimensional topological insulators in magnetic fields with many holes (or pores) in the bulk. We find that at a high density of these holes in the transport direction the thermoelectric figure of merit, ZT, can be large due to the contribution of the topologically protected conducting surfaces and the suppressed phonon thermal conductivity. By applying an external magnetic field, a subgap can be induced in the surface states’ spectrum. We show that the thermoelectric efficiency can be controlled by this tunable subgap leading to values of ZT much greater than 1. Such high values of ZT for reasonable system parameters and its tunability by a magnetic field make this system a strong candidate for applications in the heat management of nanodevices, especially at low temperatures.
Enhanced coercivity of half-metallic La0.7Sr0.3MnO3 by Ru substitution under in-plane uniaxial strain
Authors: Shigematsu K. , Chikamatsu A. , Hirose Y. , Fukumura T. , Hasegawa T.
Published: February 2012

In this paper, La0.7Sr0.3Mn1-yRuyO3 (y = 0, 0.05, and 0.1) (001) epitaxial thin films were grown on NdGaO3 (110) substrates with in-plane uniaxial strain, and the coercivity (Hc) and in-plane magnetic anisotropy were evaluated. The coercivity of the epitaxial film grown on the NdGaO3 substrate, in which the easy and hard axes correspond to the NdGaO3 [11¯0] and NdGaO3 [001] directions, respectively, was significantly increased in comparison with a corresponding film grown on the SrTiO3 (001) substrate. With increasing Ru content, the Hc along NdGaO3 [11¯0] was almost twice as large as that along NdGaO3 [001], due to enhanced antiferromagnetic coupling by Ru substitution under the uniaxial strain.
Design and analysis of new fault-tolerant permanent magnet motors for four-wheel-driving electric vehicles
Authors: Liu Guohai , Gong Wensheng , Chen Qian , Jian Linni , Shen Yue , Zhao Wenxiang
Published: February 2012

In this paper, a novel in-wheel permanent-magnet (PM) motor for four-wheel-driving electrical vehicles is proposed. It adopts an outer-rotor topology, which can help generate a large drive torque, in order to achieve prominent dynamic performance of the vehicle. Moreover, by adopting single-layer concentrated-windings, fault-tolerant teeth, and the optimal combination of slot and pole numbers, the proposed motor inherently offers negligible electromagnetic coupling between different phase windings, hence, it possesses a fault-tolerant characteristic. Meanwhile, the phase back electromotive force waveforms can be designed to be sinusoidal by employing PMs with a trapezoidal shape, eccentric armature teeth, and unequal tooth widths. The electromagnetic performance is comprehensively investigated and the optimal design is conducted by using the finite-element method.
Comparison of specific absorption rate induced in brain tissues of a child and an adult using mobile phone
Authors: Lu Mai , Ueno Shoogo
Published: February 2012

The steady increase of mobile phone usage, especially mobile phones by children, has led to a rising concern about the possible adverse health effects of radio frequency electromagnetic field exposure. The objective of this work is to study whether there is a larger radio frequency energy absorption in the brain of a child compared to that of an adult. For this reason, three high-resolution models, two child head models (6 - and 11-year old) and one adult head model (34-year old) have been used in the study. A finite-difference time-domain method was employed to calculate the specific absorption rate (SAR) in the models from exposure to a generic handset at 1750 MHz. The results show that the SAR distributions in the human brain are age-dependent, and there is a deeper penetration of the absorbed SAR in the child’s brain. The induced SAR can be significantly higher in subregions of the child’s brain. In all of the examined cases, the SAR values in the brains of a child and an adult are well below the IEEE safety standard.
The thickness, electric field, and strain effects on the magnetic anisotropy of FeCo/MgO(001) thin films: A first principles study
Authors: He K. H. , Chen J. S.
Published: February 2012

The magnetic anisotropy of the FeCo/MgO(001) thin films with the effects of thickness, the electric field, and the strain of the in-plane lattice constant were investigated by first-principles calculations. The thickness dependence of the magnetic anisotropy of FeCo ultrathin films in the range of one to four monolayers was explored, and the films with one, three, and four FeCo monolayers preferred the in-plane easy axis of magnetization, while the film with two FeCo monolayers occupied the perpendicular anisotropy. In the presence of an electric field, the magnetic anisotropy energies for all four films could be enhanced; moreover, the transition of the easy axis of magnetization from in-plane to out-of-plane also could be obtained, and the transition electric field was related with their thickness. It could be found that the variation of the in-plane lattice constant resulted in the switching from the perpendicular to in-plane anisotropy for the film with two FeCo monolayers.
Time-resolved measurement of spin-wave spectra in CoO capped [Co(t)/Pt(7Å)]n-1 Co(t) multilayer systems
Authors: Pal S. , Rana B. , Saha S. , Mandal R. , Hellwig O. , Romero-Vivas J. , Mamica S. , Klos J. W. , Mruczkiewicz M. , Sokolovskyy M. L. , Krawczyk M. , Barman A.
Published: February 2012

We present an all-optical time-resolved measurement of dipole-exchange spin wave spectra in a series of CoO capped [Co(t)/Pt(7 Å)]n-1 Co(t) multilayer systems, where the total Co moment (n × t) is constant. In general, the spectra consist of two intense peaks and additional lower intensity peaks. The observed spin wave modes are modeled by a discrete dipole approximation. The frequency of the spin wave bands depends significantly upon the magnetic anisotropy and the lattice spacing between planes. Both symmetric and anti-symmetric modes are observed from the calculation of the spin-wave profiles across the multilayer in the out-of-plane direction.
Melt spun and suction cast Nd-Fe-Co-B-Nb hard magnets with high Nd contents
Authors: Cui X. H. , Liu Z. W. , Zhong X. C. , Yu H. Y. , Zeng D. C.
Published: February 2012

Nd-Fe-Co-B-Nb alloys with Nd contents of 9−9.5 at % were prepared by melt spinning and suction casting. It was found from the melt spun ribbon samples that Nb addition enhanced the glass forming ability and Co addition improved the thermal stability. Larger values of Jr and (BH)max were obtained for the ribbon samples than for the bulk ones due to the finer crystalline structure in the former. Nanocrystallite with amorphous structure was found in the suction cast rod samples. The as-cast Nd9Fe71.5B15.5Nb4 rod in a diameter of 2 mm exhibited the best hard magnetic behavior. A remanence of 0.59 T, a coercivity of 1154 kA/m, and a maximum energy product of 54.2 kJ/m3 have been obtained after heat treatment. The distribution of nonmagnetic FeNb phase plays a key role in the improvement of coercivity. Current work suggests that large size Nd2Fe14B/Fe3B nanocomposite magnets with high Nd contents and good magnetic properties can be obtained using a nanocrystalline precursor instead of bulk metallic glass.
Two-soliton precession state in a parametrically driven magnetic wire
Authors: Urzagasti D. , Laroze D. , Clerc M. G. , Coulibaly S. , Pleiner H.
Published: February 2012

The pattern formation in a magnetic wire forced by a time dependent magnetic field is studied. This system is described in the continuum limit by the Landau-Lifshitz-Gilbert equation. The spatio-temporal magnetization field exhibits two-soliton bound state solutions. Close to the parametric resonance instability, an amplitude equation allows us to understand and characterize these localized states.
H− radio frequency source development at the Spallation Neutron Source
Authors: Welton R. F. , Dudnikov V. G. , Gawne K. R. , Han B. X. , Murray S. N. , Pennisi T. R. , Roseberry R. T. , Santana M. , Stockli M. P. , Turvey M. W.
Published: February 2012

The Spallation Neutron Source (SNS) now routinely operates nearly 1 MW of beam power on target with a highly persistent ∼38 mA peak current in the linac and an availability of ∼90%. H− beam pulses (∼1 ms, 60 Hz) are produced by a Cs-enhanced, multicusp ion source closely coupled with an electrostatic low energy beam transport (LEBT), which focuses the 65 kV beam into a radio frequency quadrupole accelerator. The source plasma is generated by RF excitation (2 MHz, ∼60 kW) of a copper antenna that has been encased with a thickness of ∼0.7 mm of porcelain enamel and immersed into the plasma chamber. The ion source and LEBT normally have a combined availability of ∼99%. Recent increases in duty-factor and RF power have made antenna failures a leading cause of downtime. This report first identifies the physical mechanism of antenna failure from a statistical inspection of ∼75 antennas which ran at the SNS, scanning electron microscopy studies of antenna surface, and cross sectional cuts and analysis of calorimetric heating measurements. Failure mitigation efforts are then described which include modifying the antenna geometry and our acceptance/installation criteria. Progress and status of the development of the SNS external antenna source, a long-term solution to the internal antenna problem, are then discussed. Currently, this source is capable of delivering comparable beam currents to the baseline source to the SNS and, an earlier version, has briefly demonstrated unanalyzed currents up to ∼100 mA (1 ms, 60 Hz) on the test stand. In particular, this paper discusses plasma ignition (dc and RF plasma guns), antenna reliability, magnet overheating, and insufficient beam persistence.
Experimental development on the 18 mA, H− multi-cusp ion source at China Institute of Atomic Energy
Authors: Zhang TianJue , Jia XianLu , Qin JiuChang , Lv Yinlong , Zheng Xia
Published: February 2012

The ion source is one of the key devices for the high-intensity cyclotron, which exerts influence on the beam intensity and applications of the machine. The H− multi-cusp ion source developed at China Institute of Atomic Energy has been used to perform experimental study on beam intensity and emittance versus the bias voltage, arc power, lens voltage, and pressure of the ion source. Up to now, 18 mA H− ion beam with emittance of 0.93 πmm mrad (four times RMS normalized emittance) was obtained from this ion source through the in-depth study and optimization on some essential factors affecting the beam intensity and quality. The paper will present the experimental study on the ion source as well as the beam test results.