bluuebunny/crossref_metadata_2025 huggingface dataset:
A model for estimating cross‐shore surface transport with application to the New Jersey Shelf
Authors: Jiang L. , Breaker L. C. , Yan X.‐H.
Published: April 2010

A one‐dimensional, steady state numerical model is developed for estimating cross‐shore surface transport in shallow waters, where the water depth is comparable to boundary layer thickness. The model is used to solve a momentum equation which describes the cross‐shore balance. To validate the model, acoustic Doppler current profiler (ADCP) current data collected during an experiment off the New Jersey shelf in the summer of 1996 are used to estimate the cross‐shore surface transport during that period and then compared with model predictions based on the local wind. The success of the model in estimating the cross‐shore surface transport leads to an improved version of the conventional upwelling index (i.e., the Bakun Index), particularly for coastal areas with wide and shallow shelves, such as the east coast of the United States. Finally, the model, because of its simplicity, is well suited for operational applications where computational resources may be limited.
Analysis of the tropical tropopause layer using the Nonhydrostatic Icosahedral Atmospheric Model (NICAM): Aqua planet experiments
Authors: Kubokawa H. , Fujiwara M. , Nasuno T. , Satoh M.
Published: April 2010

The dynamical characteristics of the tropical tropopause layer (TTL) are investigated using the Nonhydrostatic Icosahedral Atmospheric Model (NICAM) run on the Earth Simulator under an aqua planet condition. Two experiments are performed: one with a 3.5 km horizontal spacing and a three‐dimensional snapshot output and another with a 7 km horizontal spacing and 3‐hourly averages for 1 month. The number of vertical levels is 54 and the model top is at 40 km; the vertical spacing in and around the TTL is ∼700 m. Large‐scale organized convection associated with convectively coupled equatorial Kelvin waves prevails around the equator. The zonal mean vertical distribution of cloud top height near the equator shows a realistic trimodal structure. The simulation results reveal that cumulus clouds penetrate the lapse‐rate tropopause and the bottom boundary of the TTL (defined as the lapse rate minimum) for ∼0.1% and ∼25%, respectively, in the equatorial area. The frequency distribution of vertical wind may provide a good indicator of the TTL bottom boundary. A significant reduction in the speed of strong vertical winds is observed at ∼16 km. High variability in temperature and the water vapor mixing ratio observed around the tropopause is mainly caused by equatorial Kelvin waves generated by the organized convection in these experiments. Horizontal variability in tropopause height over a large‐scale convective system is much smaller than that in the area of Kelvin waves. The gravity waves generated by this large‐scale convective system locally control the temperature around the tropopause. In addition, large‐amplitude gravity waves with a scale of 600 km are superimposed on the cold phase of Kelvin waves, producing one of the coldest regions around the tropopause. It is suggested that the combination of Kelvin waves and gravity waves may be one of the most effective dehydration processes in the TTL.
Relation between intraseasonal and interannual variability of the South Asian monsoon in the National Centers for Environmental Predictions forecast systems
Authors: Achuthavarier Deepthi , Krishnamurthy V.
Published: April 2010

This study has investigated the extent to which the state‐of‐the‐art general circulation models are able to reproduce the observed relation between the intraseasonal and interannual variability of the South Asian monsoon. Long simulations from two coupled models with different horizontal resolutions and one uncoupled model of the National Centers for Environmental Prediction Climate Forecast System are analyzed. Specifically, the observed feature that the interannual variability of the seasonal monsoon is largely determined by large‐scale seasonally persistent modes rather than the nature and frequency of the intraseasonal oscillations has been examined in the model simulations. The importance of ocean‐atmosphere interaction has also been examined by comparing the coupled and uncoupled model simulations. The models simulate the spatial structure of the mean and variability of the monsoon fairly well, although the details over the Indian land region are inadequate in all simulations. The variability of the rainfall is overestimated in the models, especially in the uncoupled version. The coupled simulations produce more realistic precipitation and circulation patterns, while the improvement in the mean and variability due to higher horizontal resolution is marginal. Composite and pattern correlation analyses indicate the presence of a large‐scale seasonally persistent structure that largely determines the interannual variability of the seasonal mean monsoon. Consistent with the observations, the probability distributions of the pattern correlations indicate that the nature and frequency of the intraseasonal oscillations remain unchanged between strong and weak monsoon years. Similar to the observations, the model results provide hope for seasonal prediction of monsoon.
Evaluation of the orogenic belt hypothesis for the formation of the Thaumasia Highlands, Mars
Authors: Nahm Amanda L. , Schultz Richard A.
Published: April 2010

Thrust faults along the southern margin of the Thaumasia Highlands, Mars, comprise a set of discrete subparallel south verging structures. Previous work proposed that the faults collectively define a narrow Earth‐like orogenic belt composed of a deformed lithospheric section translating southward through Tharsis above a regional décollement. This hypothesis is tested here by comparing topographic slopes across the Thaumasia Highlands to the values required by thrust faulting in a critical taper wedge setting. In general, topographic slopes across the Thaumasia Highlands, 0.418–1.017°, are too shallow for the Martian lithosphere to have deformed as a critical taper wedge, assuming reasonable values for pore fluid pressure ratios and frictional strengths of the wedge material and putative décollement. Combined with the absence of a mechanism to provide the necessary values of horizontal shortening (hundreds of km), nearly lithostatic pore fluid pressure ratios, and nearly frictionless décollements over regional scales on Mars that would be necessary for lithospheric translation as a wedge, the results are consistent with thrust fault deformation across Mars that is not integrated at depth into subhorizontal structures, but which function instead as discrete structures.
A new midlatitude ionosphere electrodynamics coupling model (MIECO): Latitudinal dependence and propagation of medium‐scale traveling ionospheric disturbances
Authors: Yokoyama Tatsuhiro , Hysell David L.
Published: April 2010

In order to study nighttime medium‐scale traveling ionospheric disturbances (MSTIDs), we have developed a new midlatitude ionosphere electrodynamics coupling model (MIECO) which can model the coupling process between the E and F regions with dipole magnetic field lines. Using the new model, MSTID structure is reproduced from random perturbation on an Es layer by the coupled Perkins and sporadic‐E (Es)‐layer instabilities in a wide latitudinal range. A typical wavelength of ∼150 km, larger amplitude, and smaller MSTID's tilt angles at lower latitudes are consistent with observations. It is shown that the polarization process in the E region driven by neutral winds is essentially important for the full development of MSTIDs as well as the seeding of NW–SE perturbation in the F region.
Precursory signals in analysis ensemble spread
Authors: Enomoto Takeshi , Hattori Miki , Miyoshi Takemasa , Yamane Shozo
Published: April 2010

Time evolution of the ensemble spread of an experimental ensemble atmospheric reanalysis ALERA is examined in relation to various meteorological phenomena. The analysis ensemble spread increases about two days prior to westerly bursts in the eastern Indian Ocean. Precursory signals are also found in the monsoon onset. The analysis ensemble spread is large at the leading edge of the Somali jet and it grows as the jet extends eastward. Over Vietnam analysis ensemble spread is maximized several weeks before the maximum of the monsoon westerlies. In the stratosphere the analysis ensemble spread takes the maximum value a few days prior to a sudden warming. Our findings indicate that the ensemble analysis contains additional information on atmospheric uncertainty of scientific interest, which may also have practical value.
Twentieth century bipolar seesaw of the Arctic and Antarctic surface air temperatures
Authors: Chylek Petr , Folland Chris K. , Lesins Glen , Dubey Manvendra K.
Published: April 2010

Understanding the phase relationship between climate changes in the Arctic and Antarctic regions is essential for our understanding of the dynamics of the Earth's climate system. In this paper we show that the 20th century de‐trended Arctic and Antarctic temperatures vary in anti‐phase seesaw pattern – when the Arctic warms the Antarctica cools and visa versa. This is the first time that a bi‐polar seesaw pattern has been identified in the 20th century Arctic and Antarctic temperature records. The Arctic (Antarctic) de‐trended temperatures are highly correlated (anti‐correlated) with the Atlantic Multi‐decadal Oscillation (AMO) index suggesting the Atlantic Ocean as a possible link between the climate variability of the Arctic and Antarctic regions. Recent accelerated warming of the Arctic results from a positive reinforcement of the linear warming trend (due to an increasing concentration of greenhouse gases and other possible forcings) by the warming phase of the multidecadal climate variability (due to fluctuations of the Atlantic Ocean circulation).
MRI Estimation of Global Brain Oxygen Consumption Rate
Authors: Jain Varsha , Langham Michael C , Wehrli Felix W
Published: April 2010

Measuring the global cerebral metabolic rate of oxygen ( CMRO2) is a valuable tool for assessing brain vitality and function. Measurement of blood oxygen saturation ( HbO2) and flow in the major cerebral outflow and inflow vessels can provide a global estimate of CMRO2. We demonstrate a rapid noninvasive method for quantifying CMRO2 by simultaneously measuring venous oxygen saturation in the superior sagittal sinus with magnetic resonance susceptometry-based oximetry, a technique that exploits the intrinsic susceptibility of deoxygenated hemoglobin, and the average blood inflow rate with phase-contrast magnetic resonance imaging. The average venous HbO2, cerebral blood flow, and global CMRO2 values in eight healthy, normal study subjects were 64%±4%, 45.2±3.2 mL per 100 g per minute, and 127±7 μmol per 100 g per minute, respectively. These values are in good agreement with those reported in literature. The technique described is noninvasive, robust, and reproducible for in vivo applications, making it ideal for use in clinical settings for assessing the pathologies associated with dysregulation of cerebral metabolism. In addition, the short acquisition time (∼30 seconds) makes the technique suitable for studying the temporal variations in CMRO2 in response to physiologic challenges.
ACE Inhibition Reduces Infarction in Normotensive but Not Hypertensive Rats: Correlation with Cortical ACE Activity
Authors: Porritt Michelle J , Chen Michelle , Rewell Sarah SJ , Dean Rachael G , Burrell Louise M , Howells David W
Published: April 2010

Angiotensin-converting enzyme (ACE) inhibition can reduce stroke risk by up to 43% in humans and reduce the associated disability, and hence understanding the mechanism of improvement is important. In animals and humans, these effects may be independent of the blood pressure-lowering effects of ACE inhibition. Normotensive (Wistar–Kyoto (WKY)) and hypertensive (spontaneously hypertensive rat (SHR)) animals were treated with the ACE inhibitors ramipril or lisinopril for 7 or 42 days before 2 hours of transient middle cerebral artery occlusion (MCAo). Blood pressure, serum ACE, and blood glucose levels were measured and stroke infarct volume was recorded 24 hours after stroke. Despite greater reductions in blood pressure, infarct size was not improved by ACE inhibition in hypertensive animals. Short-term ACE inhibition produced only a modest reduction in blood pressure, but WKY rats showed marked reductions in infarct volume. Long-term ACE inhibition had additional reductions in blood pressure; however, infarct volumes in WKY rats did not improve further but worsened. WKY rats differed from SHR in having marked cortical ACE activity that was highly sensitive to ACE inhibition. The beneficial effects of ACE inhibition on infarct volume in normotensive rats do not correlate with changes in blood pressure. However, WKY rats have ACE inhibitor-sensitive cortical ACE activity that is lacking in the SHR.
Microdialysis with Radiometric Monitoring of L-[β-11C]DOPA to Assess Dopaminergic Metabolism: Effect of Inhibitors of L-Amino Acid Decarboxylase, Monoamine Oxidase, and Catechol-O-Methyltransferase on Rat Striatal Dialysate
Authors: Okada Maki , Nakao Ryuji , Hosoi Rie , Zhang Ming-Rong , Fukumura Toshimitsu , Suzuki Kazutoshi , Inoue Osamu
Published: April 2010

The catecholamine, dopamine (DA), is synthesized from 3,4-dihydroxy-L-phenylalanine (L-DOPA) by aromatic L-amino acid decarboxylase (AADC). Dopamine metabolism is regulated by monoamine oxidase (MAO) and catechol- O-methyltransferase (COMT). To measure dopaminergic metabolism, we used microdialysis with radiometric detection to monitor L-[β-11C]DOPA metabolites in the extracellular space of the rat striatum. We also evaluated the effects of AADC, MAO, and COMT inhibitors on metabolite profiles. The major early species measured after administration of L-[β-11C]DOPA were [11C]3,4-dihydroxyphenylacetic acid ([11C]DOPAC) and [11C]homovanillic acid ([11C]HVA) in a 1:1 ratio, which shifted toward [11C]HVA with time. An AADC inhibitor increased the uptake of L-[β-11C]DOPA and L-3- O-methyl-[11C]DOPA and delayed the accumulation of [11C]DOPAC and [11C]HVA. The MAO and COMT inhibitors increased the production of [11C]3-methoxytyramine and [11C]DOPAC, respectively. These results reflect the L-DOPA metabolic pathway, suggesting that this method may be useful for assessing dopaminergic metabolism.
Neuroprotection by Dimethyloxalylglycine following Permanent and Transient Focal Cerebral Ischemia in Rats
Authors: Nagel Simon , Papadakis Michalis , Chen Ruoli , Hoyte Lisa C , Brooks Keith J , Gallichan Daniel , Sibson Nicola R , Pugh Chris , Buchan Alastair M
Published: April 2010

Dimethyloxalylglycine (DMOG) is an inhibitor of prolyl-4-hydroxylase domain (PHD) enzymes that regulate the stability of hypoxia-inducible factor (HIF). We investigated the effect of DMOG on the outcome after permanent and transient middle cerebral artery occlusion (p/tMCAO) in the rat. Before and after pMCAO, rats were treated with 40 mg/kg, 200 mg/kg DMOG, or vehicle, and with 40 mg/kg or vehicle after tMCAO. Serial magnetic resonance imaging (MRI) was performed to assess infarct evolution and regional cerebral blood flow (rCBF). Both doses significantly reduced infarct volumes, but only 40 mg/kg improved the behavior after 24 hours of pMCAO. Animals receiving 40 mg/kg were more likely to maintain rCBF values above 30% from the contralateral hemisphere within 24 hours of pMCAO. DMOG after tMCAO significantly reduced the infarct volumes and improved behavior at 24 hours and 8 days and also improved the rCBF after 24 hours. A consistent and significant upregulation of both mRNA and protein levels of vascular endothelial growth factor (VEGF) and endothelial nitric oxide synthase (eNOS) was associated with the observed neuroprotection, although this was not consistently related to HIF-1α levels at 24 hours and 8 days. Thus, DMOG afforded neuroprotection both at 24 hours after pMCAO and at 24 hours and 8 days after tMCAO. This effect was associated with an increase of VEGF and eNOS and was mediated by improved rCBF after DMOG treatment.
Dependence of sensitivity of biosensor for carbon nanotube field-effect transistor with top-gate structures
Authors: Abe Masuhiro , Murata Katsuyuki , Matsumoto Kazuhiko
Published: April 2010

In this study, we used biosensors that employ a top-gate-type carbon nanotube field-effect transistor (CNT-FET) for detecting target proteins in a solution. The dependence of the sensitivity of the biosensor on structural characteristics of the top gate, such as the thicknesses of its insulator and electrode and the relative permittivity of the insulator, was examined by simulations and by experiment which change the thickness of the insulator. Results of calculations performed by the finite element method showed that a thin insulator with a relative permittivity greater than 20 would lead to high sensitivity of the CNT-FET biosensor. Experimental investigation supported this result. The transconductance of a CNT-FET with a 20-nm-thick insulating layer was found to be approximately six times higher than that with 50-nm-thick and 80-nm-thick insulating layers. Moreover, the sensitivity of the CNT-FET biosensor with the 20-nm-thick insulating layer was also higher than that of a CNT-FET with a thicker insulating layer. By the experimental measurements, the influence of insulator thickness on the sensitivity of the biosensor was elucidated for the first time.
Time-resolved study of polyimide absorption layers for blister-actuated laser-induced forward transfer
Authors: Brown Matthew S. , Kattamis Nicholas T. , Arnold Craig B.
Published: April 2010

Blister-actuated laser-induced forward transfer (BA-LIFT) is a versatile, direct-write process capable of printing high-resolution patterns from a variety of sensitive donor materials without damage to their functionality. In this work, we use time-resolved imaging to study the laser-induced formation of blisters on polyimide films in order to understand and optimize their role in BA-LIFT. We find that the initial blister expansion occurs very rapidly (<100 ns), followed by a brief oscillation (100–500 ns), and then a longer time contraction to steady-state dimensions (0.5–50 μs). This behavior is explained by kinetic and thermal effects that occur during the process. We further probe the influence of polyimide thickness, laser beam diameter, and laser fluence on blister formation characteristics. Results indicate that the presence of a thin layer of donor material on the polyimide surface does not have a significant effect on the size and shape of the blisters which form.
Synthesis of submicron sized Fe20Ni80 particles and their magnetic properties
Authors: Kodama Daisuke , Shinoda Kozo , Kasuya Ryo , Tohji Kazuyuki , Doi Masaaki , Balachandran Jeyadevan
Published: April 2010

Fe–Ni alloy nanoparticles were synthesized by polyol process using hydrazine as a reduction assist reagent. Particle size, crystallite size, and crystal phases varied with the type of polyol. The saturation magnetizations of the as-synthesized Fe–Ni particles synthesized in ethylene glycol (EG) and 1-heptanol were similar to the bulk and were 73 emu/g and 83 emu/g, respectively. On the other hand, the coercivities of the same were 41 and 123 Oe. The coercivity of the Fe–Ni particles synthesized in EG decreased to 27 Oe after heat treatment. Though the magnetic properties were very similar irrespective of the polyol used in this study, the Mössbauer spectroscopic measurements revealed that Fe–Ni particles with single permalloy phase was synthesized only when EG was used.
Effect of the M/Co substitution on magnetocrystalline anisotropy and magnetization in SmCo5−xMx compounds (M=Ga;Al)
Authors: Laslo A. , Colin C. V. , Isnard O. , Guillot M.
Published: April 2010

The isothermal magnetization curves were carried out on magnetically aligned powder of the SmCo4Ga and SmCo4Al samples; they have been measured at 4.2 K in applied field up to 33 T produced by a water-cooled resistive magnet. The intrinsic magnetic properties such as saturation magnetization, anisotropy constant, and anisotropy field have been derived. Whereas some properties, such as the saturation magnetization or the Curie temperature are found to be strongly reduced upon Ga or Al for Co substitution, on the contrary the magnetocrystalline anisotropy is much larger for the substituted compounds. Hysteresis cycles are presented also and coercivity ranging from 4.5 to 6 T are reported. The mechanism at the origin of the coercivity is also modified from a nucleation type for SmCo5 to a pinning type for the Ga or Al containing compounds.
Structural, electrical, magnetic, and thermal studies of Cr-doped La0.7Ca0.3Mn1−xCrxO3 (≤x≤1) manganites
Authors: Kumar Neeraj , Kishan H. , Rao Ashok , Awana V. P. S.
Published: April 2010

We report detailed structural, electrical, magnetic, and specific heat studies on La0.7Ca0.3Mn1−xCrxO3 manganites. Rietveld analysis of fitted and observed x-ray diffraction patterns exhibited the single-phase nature of all the studied materials, which crystallize in Pbnm space group. Successive substitution of Cr at Mn-site in La0.7Ca0.3Mn1−xCrxO3 manganites increases the electrical resistivity and decreases the characteristic insulator-metal transition temperature (TIM) of the parent compound along with a humplike feature for higher Cr-content (x>0.06) samples. The hump structure basically signifies the onset of antiferromagnetic (AFM) interactions as inferred by both the magnetic and infrared (IR) spectroscopy studies. The systematic suppression of FM state results in a spin glass (SG)-like behavior. IR studies revealed that the vibration mode at 413 cm−1 being associated with internal bending of MnO6 octahedra, becomes softer, indicating an increase in distortion and hence the possible SG behavior. The critical exponents (α, β, and γ) are calculated from the heat capacity (CP) data near the TIM/TFM. The same exhibited variations of their values with doping. In particular, the value of β increases from 0.37(x=0.0) to 0.43(x=0.04), clearly indicating the coexistence of both long and short range magnetic orders, i.e., tendency toward SG state for Cr-doped samples. On the basis of present results, it is suggested that Cr dilutes double-exchange based FM and rather promotes the AFM based superexchange interactions via Cr3+/Mn4+ ions. Substitution of Cr systematically destroys both the metallic state and long range FM order.
Density approach to ballistic anomalous diffusion: An exact analytical treatment
Authors: Bologna Mauro , Ascolani Gianluca , Grigolini Paolo
Published: April 2010

This paper addresses the problem of deriving the probability distribution density of a diffusion process generated by a nonergodic dichotomous fluctuation using the Liouville equation (density method). The velocity of the diffusing particles fluctuates from the value of 1 to the value of −1, and back, with the distribution density of time durations τ of the two states proportional to 1/τμ in the asymptotic time limit. The adopted density method allows us to establish an exact analytical expression for the probability distribution density of the diffusion process generated by these fluctuations. Contrary to intuitive expectations, the central part of the diffusion distribution density is not left empty when moving from μ>2 (ergodic condition) to μ<2 (nonergodic condition). The intuitive expectation is realized for μ<μcr, with μcr≈1.6. For values of μ>μcr, the monomodal distribution density with a minimum at the origin is turned into a bimodal one, with a central bump whose intensity increases for μ→2. The exact theoretical treatment applies to the asymptotic time limit, which establishes for the diffusion process the ballistic scaling value δ=1. To assess the time evolution toward this asymptotic time condition, we use a numerical approach which relates the emergence of the central bump at μ=μcr with the generation of the ordinary scaling δ=0.5, which lasts for larger and larger times for μ coming closer and closer to the critical value μ=2. We assign to the waiting time distribution density two different analytical forms: one derived from the Manneville intermittence (MI) theory and one from the Mittag-Leffler (ML) survival probability. The adoption of the ML waiting time distribution density generates an exact analytical prediction, whereas the MI method allows us to get the same asymptotic time limit as the ML one for μ<2 as a result of an approximation. The joint adoption of these two waiting time distribution densities sheds light into the critical nature of the condition μ=2 and into why this is the critical point for the MI process, representing the phase transition from the nonergodic to the ergodic regime. Our main result can be interpreted as a new derivation of Lamperti distribution.
Effects of C addition in Fe65Co35 and Fe9.5Co90.5 soft magnetic films
Authors: Edon V. , Dubourg S. , Vernières J. , Warot-Fonrose B. , Bobo J. F.
Published: April 2010

Fe 65 Co 35 and Fe9.5Co90.5 thin films with carbon addition were deposited by reactive sputtering and investigated in terms of static and dynamic magnetic properties. The acetylene rate was adjusted in order to deposit nanocrystalline soft magnetic films, with a high saturation magnetization, a high resistivity, and a low coercivity. The transition of the crystalline structure to a nanocrystalline or amorphous arrangement—giving rise to soft magnetic properties—depended on the Fe/Co ratio and the C content. The lowest coercivity of 0.4 Oe was obtained for a Fe9.5Co90.5 film with 0.95% of C2H2, whereas a Fe65Co35 film with 0.75% of C2H2 exhibited a coercivity of 0.7 Oe. The microwave properties of the Fe65Co35 layers remained stable over this C2H2 content whereas the resonance frequency of the Fe9.5Co90.5 films decreased with the C2H2/Ar ratio. A difference in the manner that the carbon was incorporated, depending on the Fe/Co ratio, may explain the observed magnetic properties.
Whole-heart magnetic resonance coronary angiography with multiple breath-holds and automatic breathing-level tracking
Authors: Kuhara Shigehide , Ninomiya Ayako , Okada Tomohisa , Kanao Shotaro , Kamae Toshikazu , Togashi Kaori
Published: April 2010

Whole-heart (WH) magnetic resonance coronary angiography (MRCA) studies are usually performed during free breathing while monitoring the position of the diaphragm with real-time motion correction. However, this results in a long scan time and the patient’s breathing pattern may change, causing the study to be aborted. Alternatively, WH MRCA can be performed with multiple breath-holds (mBH). However, one problem in the mBH method is that patients cannot hold their breath at the same position every time, leading to image degradation. We have developed a new WH MRCA imaging method that employs both the mBH method and automatic breathing-level tracking to permit automatic tracking of the changes in breathing or breath-hold levels. Evaluation of its effects on WH MRCA image quality showed that this method can provide high-quality images within a shorter scan time. This proposed method is expected to be very useful in clinical WH MRCA studies.
Perpendicular magnetic tunnel junctions using Co-based multilayers
Authors: Tadisina Z. R. , Natarajarathinam A. , Clark B. D. , Highsmith A. L. , Mewes T. , Gupta S. , Chen E. , Wang S.
Published: April 2010

CoFeB/MgO/CoFeB magnetic tunnel junctions (MTJs) with perpendicular magnetic anisotropy (PMA) free and reference layers composed of Co/M (where M=Pd or Ni) multilayers have been optimized for high PMA and high tunneling magnetoresistance (TMR). The effects of Co thickness, Pd thickness, and the number of Co/Pd bilayers on the anisotropy and coercivity of the [Co/Pd]n multilayer films have been studied for both free and reference layers. The damping parameter α of CoFeB capped multilayers was determined using broadband ferromagnetic resonance. The transport properties of the patterned MTJ stacks were measured from 10 to 400 K. A maximum TMR of 10% at 10 K (5%–10% at 300 K) was obtained for these perpendicular MTJs, regardless of whether or not they were magnetically annealed for MgO–CoFeB crystallization. This indicates that the fcc-bcc-fcc transitions from the fcc multilayers to the bcc CoFeB/MgO/CoFeB do not promote the “giant MgO TMR effect” caused by symmetry filtering.
Magnetically tunable properties related with carriers density in self-doped La1−xMnO3/y wt %Nb–SrTiO3 heteroepitaxial junctions
Authors: Wang Z. H. , Yu G. L. , Qiu L. , Wu X. S. , Wang L. , Gao J.
Published: April 2010

The self-doped La1−xMnO3 (x=0.1 and 0.3) thin films deposited on Nb-doped (wt % y) SrTiO3 (y=0.05 and 0.8) crystals to form heteroepitaxial junctions have been prepared by the pulse laser deposition method. The current-voltage loops of junction were measured at several fixed magnetic fields for the temperature from 10 to 300 K. We have focused on the effects of doping level and annealing time on the magnetically tunable property of the junction. The results show that these junctions have a typical temperature-dependent rectifying characteristics and asymmetrical hysteresis. The magnetically tunable property of the junction was related with the annealing time for the self-doped La1−xMnO3−δ thin film and the doping level in the Nb-doped SrTiO3 (STON) crystal. In the self-doped La0.9MnO3/0.05-STON junction annealed at 900 °C for 5 h, the relative ratio of voltage [Vb(0)−Vb(H)]/Vb(0) is about 70% at H=6 T and T=70 K for I=0.1 mA, showing a large magnetically tunable property. These results reveal the great potential of the manganites in configuring artificial devices.
Magnetorheology and sedimentation behavior of an aqueous suspension of surface modified carbonyl iron particles
Authors: Cheng H. B. , Zuo L. , Song J. H. , Zhang Q. J. , Wereley N. M.
Published: April 2010

Surface modified carbonyl iron particles (SMCIPs) were synthesized by coating carbonyl iron particles with an organic reagent (N-polyether, N, N, N,-acetyloxy) 2, 6-aminion-1, 3, 4-thiadiazole dimer. The properties of these SMCIPs, including morphology, structure, and magnetic behavior, were characterized using scanning electron microscopy and a vibrating sample magnetometer. Aqueous magnetorheological (MR) fluids were prepared using SMCIPs. MR properties were measured via a strain-controlled parallel disk rheometer equipped with a magnetic field source. Addition of the organic surface coating layer was found to greatly improve sedimentation stability of the aqueous MR fluids at a small cost of a reduction in field dependent yield stress.
On linear differential equations with variable coefficients involving a para-Grassmann variable
Authors: Mansour Toufik , Schork Matthias
Published: April 2010

Linear differential equations with constant coefficients involving a para-Grassmann variable have been considered recently in the work of Mansour and Schork [Symmetry, Integr. Geom.: Methods Appl. 5, 73 (2009)]. In the present paper, this treatment is extended to linear differential equations with variable coefficients. For the equation of first order, an explicit formula for the solution is given. For the equations of higher order, it is shown how the solutions may be determined in terms of the solutions of “ordinary” differential equations (i.e., involving only “bosonic” variables). Some examples of these differential equations are discussed and analogs for the trigonometric functions are introduced.
Study of the effect of gas pressure and catalyst droplets number density on silicon nanowires growth, tapering, and gold coverage
Authors: Chen W. H. , Lardé R. , Cadel E. , Xu T. , Grandidier B. , Nys J. P. , Stiévenard D. , Pareige P.
Published: April 2010

We investigated the growth of silicon nanowires from Au-rich catalyst droplets by two different methods: chemical vapor deposition (CVD) and molecular beam epitaxy (MBE). The growth rate is found to be diameter-dependent and increases with increasing precursor partial pressures. The comparison of the experimental results with models shows that the contribution of Si atoms that diffuses from the substrate and the NW sidewalls toward the catalyst droplet can be neglected in CVD for the different pressures used in this study, whereas it is the major source of Si supply for the MBE growth. In addition, by decreasing the number density of catalyst droplet prior to the NW growth in CVD, it is also found that this parameter affects the NWs morphology, increasing the tapering effect when the silane partial pressure is small enough to allow gold atom diffusion from the catalyst droplet.
Magnetic properties and magnetocaloric effect in Nd5Si3 compound
Authors: Tian Guang , Du Honglin , Zhang Yan , Xia Yuanhua , Wang Changsheng , Han Jingzhi , Liu Shunquan , Yang Jinbo
Published: April 2010

The structure and magnetic properties of Nd5Si3 compound have been investigated. A reversible magnetic entropy change was observed at about 112 K accompanied with a second-order magnetic transition from the ferromagnetic to paramagnetic state. The maximum value of −ΔSM is 5.0 J kg−1 K−1 at 112 K for a magnetic field change of 50 kOe. The relatively large magnetic entropy change and broad working-temperature span (about 57 K) of the reversible magnetocaloric effect make the present compound a potential candidate for the practical magnetic refrigeration in this temperature range.
Magnetic properties and magnetocaloric effect in Ho6−xErxMnBi2 compounds
Authors: Wang Fang , Zhang Jian , Yuan Feng-ying , Cao Yang , Gao Chun-jing , Hao Yan-ming , Shen Jun , Sun Ji-rong , Shen Bao-gen
Published: April 2010

Magnetic properties and magnetocaloric effect of compounds Ho6−xErxMnBi2 (x=0,3,6) are investigated experimentally. All the compounds crystallize in the hexagonal Zr6CoAs2-type structure and show a sharp drop in the magnetization around their respective magnetic ordering temperature, which is 201 K (x=0), 147 K (x=3), and 98 K (x=6), respectively. Either thermal or magnetic hysteresis around the phase transition is not observed, suggesting a second order phase transition nature. The magnetic entropy change (ΔSm) calculated from the Maxwell relation using the collected magnetization data is 10.6 (x=6), 7.3 (x=3), and 5.0 J kg−1 K−1 (x=0), respectively. The shape of the ΔSm-T curve has a good symmetry below and above the magnetic ordering temperature, and the value of the magnetic entropy change increases monotonously with increasing field change. The calorimetric technique has also been used for Er6MnBi2 to check the credibility of the magnetic method.
A sign of field-induced first order magnetic state transition and giant reversible magnetocaloric effect in cobalt hydroxide nanosheets
Authors: Shamba P. , Zeng R. , Wang J. Q. , Dou S. X.
Published: April 2010

We report the synthesis of β−Co(OH)2 nanosheets using microwave assisted hydrothermal and conventional chemical reaction methods. A magnetic transition at an onset temperature, T1∼96 K, and a sign of antiferromagnetic state transition at the Néel temperature, TN=9∼10 K, can be determined from M-T curves and M-H curves magnetic properties investigation. It is found that a sign of field-induced first order transition below 9 K, act as a role of reversing the magnetocaloric effect from negative to positive value. The large reversible magnetic-entropy change (ΔSM) of 17 J/kg K around 11 K for a field change of 5 T indicates that this material is useful for refrigeration applications at low temperatures.
The initial growth mode of Co on Cu(311)
Authors: Easton S. , Ionescu A. , Kurebayashi H. , Kim J.-Y. , Barnes C. H. W.
Published: April 2010

We present the results of a systematic investigation of the thickness dependence of ultra-thin Co films on Cu(311) at room temperature using low energy electron diffraction and the magneto-optical Kerr effect. A superparamagnetic-ferromagnetic phase transition was observed to occur at a critical thickness of dc=4.0±0.25 ML and the magnetic susceptibility was to follow a power law with a critical exponent γ=1.103±0.069, in stark disagreement with results for Co on other Cu surfaces.
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electronic and magnetic characteristics in postperovskite CaRuO3
Authors: Zhong G. H. , Li Y. L. , Liu Z. , Lin H. Q.
Published: April 2010

The magnetic and electronic properties of postperovskite CaRuO3 are investigated by performing the first-principles calculation based on generalized gradient approximation plus parameter U method. A Mott–Hubbard insulating ground state with low spin Ru4+ is found, and the A-type antiferromagnetic (AFM) spin ordering is preferred. Ru4+ ions exhibit the spatially anisotropic exchange with the exchange in a-b plane weaker than that along c direction. The large Jahn–Teller distortion lowers the energy of dz2 orbital, leading to the stabilization of low spin Ru4+ and ferromagnetic (FM) orbital ordering. The transitions of metal-insulator and FM-AFM-FM depend on the Hubbard parameter U.
Direct and converse magnetoelectric effects in Ni43Mn41Co5Sn11/Pb(Zr,Ti)O3 laminate
Authors: Chen S. Y. , Ye Q. Y. , Miao W. , Wang D. H. , Wan J. G. , Liu J.-M. , Du Y. W. , Huang Z. G. , Zhou S. Q.
Published: April 2010

A ferromagnetic shape memory alloy was utilized to construct a Ni43Mn41Co5Sn11/Pb(Zr,Ti)O3 laminate. Large direct and converse magnetoelectric (ME) effects were observed at resonance frequencies around the martensitic transition temperature of Ni43Mn41Co5Sn11 alloy, and the temperature affects the ME properties remarkably. The ME coefficients respond almost linearly to the applied ac electric or magnetic field. The mechanism of both direct and converse ME effects in the laminate is discussed.
Modifications in magnetic properties of BiMn2O5 multiferroic using swift heavy ion irradiation
Authors: Shukla D. K. , Kumar Ravi , Mollah S. , Choudhary R. J. , Thakur P. , Sharma S. K. , Brookes N. B. , Knobel M.
Published: April 2010

We report the near edge x-ray absorption fine structure (NEXAFS) and x-ray magnetic circular dichroism (XMCD) studies at the Mn L3,2 edge of pulsed laser deposited pristine thin films of multiferroic BiMn2O5. These investigations are furthermore testified for BiMn2O5 thin films irradiated through 200 MeV Ag15+ ions with fluence value 5×1011 ions/cm2. Though the pristine film is primarily antiferromagnetic in nature, irradiation induces ferrimagnetism in it. Element specific characterizations, NEXAFS and XMCD demonstrate the evolution of Mn2+ state piloting to magnetic signal associated with it.
Magnetoelectric behavior of carbonyl iron mixed Mn oxide-coated ferrite nanoparticles
Authors: Ahad Faris B. Abdul , Lee Shang-Fan , Hung Dung-Shing , Yao Yeong-Der , Yang Ruey-Bin , Lin Chung-Kwei , Tsay Chien-Yie
Published: April 2010

The dielectric and magnetic properties of manganese oxide-coated Fe3O4 nanoparticles (NPs) were measured by the cavity perturbation method at x-band microwave frequencies ranging from 7–12.5 GHz with controlled external magnetic field up to 2.2 kOe at room temperature. Different ratios (5%, 10%, and 20% by weight) of coated NPs were prepared by sol-gel method then mixed with carbonyl iron powder in epoxy matrix. The saturation magnetization is inversely proportional to the NPs ratio in the mixture between 150 and 180 emu/g. The real part of the permittivity decreased with increasing NPs concentration, but the permittivity change by magnetic field increased. The tunability behavior is explained by insulator-ferromagnetic interface magnetoelectricity and the large surface volume ratio for the NPs.
A novel multiferroic system: Rare earth chromates
Authors: Cheng Z. X. , Wang X. L. , Dou S. X. , Kimura H. , Ozawa K.
Published: April 2010

In this work, we report on our studies on the multiferroic properties of two rare earth chromates, GdCrO3 and YCrO3. Polycrystalline bulks and thin films have been fabricated using conventional solid state reaction and pulsed laser deposition. Magnetic measurements have revealed that both compounds show weak ferromagnetism below the antiferromagnetic Neel temperature, TN, of 170 and 140 K for GdCrO3 and YCrO3, respectively. However the well-developed ferroelectric polarization electrical field loop was not successfully measured for both samples due to their low resistance. The high conductivity of the samples at room temperature is related to the thermal activation of charge carriers at around 200 K in the samples revealed by temperature dependent dielectric measurement. Capacitance measurement at 77 K within magnetic field of 3000 Oe and zero field for GdCrO3 bulk sample shows an increase in 58% in capacitance at 400 kHz by a magnetic field.
Muon spin relaxation study of the layered magnetoelectric FeTe2O5Br with spin amplitude modulated magnetic structure
Authors: Zorko A. , Pregelj M. , Berger H. , Arčon D.
Published: April 2010

Local-probe weak-transverse-field and zero-field μSR measurements have been employed to investigate magnetic ordering in the new magnetoelectric compound FeTe2O5Br. Below the Néel transition temperature TN=10.6 K a static local magnetic field starts to develop at the μ+ sites. Fast μ+ polarization decay below TN speaks in favor of a broad distribution of internal magnetic fields, in agreement with the incommensurate magnetic structure suggested by neutron diffraction experiments. Above TN the presence of short-range order is detected as high as at 2TN, which suggests only weak interlayer magnetic coupling. On the other hand, strong Fe3+ spin fluctuations likely reflect geometrically frustrated structure of [Fe4O16]20− spin clusters, which are the main building blocks of the layered FeTe2O5Br structure.
Exchange bias associated with magnetic glass state in Gd5Ge4
Authors: Yuan Shujuan , Ge Junyi , Cao Shixun , Yu Liming , Wu Anhua , Xu Jun
Published: April 2010

The exchange bias phenomena associated with the magnetic glass state at low temperatures in Gd5Ge4 are studied. The exchange bias effect originates from the exchange coupling between the ferromagnetic islands and antiferromagnetic matrix in the magnetic glass state. It is found that the exchange bias in Gd5Ge4 is strongly dependent on the measuring field and the cooling field, which indicates that the antiferromagnetic matrix can be easily transformed into ferromagnetic phase under the applied field. The temperature dependence of the exchange bias field shows that the fluctuation of the temperature has less effect on the exchange bias in the low temperature range.
Magnetic phase separation and cluster-spin-glass behavior in LaMn1−xFexO3+y
Authors: de Lima O. F. , Coaquira J. A. H. , de Almeida R. L. , Malik S. K.
Published: April 2010

The crystal structure and some magnetic properties were investigated for polycrystalline samples of LaMn1−xFexO3+y, prepared by solid-state reaction in air. All samples show the ORT-2 orthorhombic structure that suppresses the Jahn–Teller distortion and favors a ferromagnetic (FM) superexchange interaction between Mn3+–O–Mn3+. An evolution from a fairly strong FM phase, for x=0.0, to an antiferromagnetic (AFM) phase, for x=1.0, was observed. For intermediate Fe contents, a magnetic mixed-phase state occurs, with a gradual decrease (increase) in the FM (AFM) phase as x increases. A clear cluster-spin-glass (CG) behavior is observed in our samples for x≤0.1, where FM coupling dominates. In this case, the Vogel–Fulcher law describes very well the CG dynamics, giving reasonable values for the fitted parameters.
Magnetic anisotropy and magnon gap state of SmB4 single crystal
Authors: Kim J. Y. , Sung N. H. , Kang B. Y. , Kim M. S. , Cho B. K. , Rhyee Jong-Soo
Published: April 2010

This paper investigates the magnetic and electronic properties of a single-crystal SmB4. Two magnetic phase transition temperatures at TN=25 K and Tm≈7 K were revealed by the temperature-dependent magnetization for an applied magnetic field perpendicular to the c-axis. Magnetic transition at TN=25 K is caused by the antiferromagnetic order with Sm3+ moments that lie on the ab-plain. However, the antiferromagnetic transition temperature was not observed in a temperature-dependent magnetization for an applied magnetic field along the c-axis. The second transition occurring at Tm≈7 K was observed for directions both parallel and perpendicular to the c-axis and was suppressed by applying magnetic fields. Interestingly, the second transition exhibited local maximum behavior, implying the second order phase transition. Furthermore, temperature-dependant resistivity showed a magnon gap feature below the second magnetic transition temperature T<Tm(=7 K).
Physical properties of β-TmAlB4; an AlB2-type analogous “tiling” compound
Authors: Mori T. , Shishido T. , Yubuta K. , Nakajima K. , Leithe-Jasper A. , Grin Yu.
Published: April 2010

β -TmAlB 4 was synthesized, and the magnetic properties and specific heat investigated in comparison with those of the α-type structure. Recent developments in rare earth aluminoboride compounds with two-dimensional boron layers have attracted interest due to the heavy fermion superconductivity in β-YbAlB4, multiple anomalies manifesting below the Néel temperatures in α-TmAlB4 attributed to intrinsic building defects, and field stable state in Tm2AlB6. Strikingly, despite similarities in the metal-metal nearest neighbor distances and structural motifs, the strength of the magnetic interactions (temperature scale) in β-TmAlB4 was discovered to be approximately 60% stronger that of the alpha phase (i.e., TN=9.2 versus 5.8 K). An anomaly in the specific heat with extreme field stability was also found with a temperature scale significantly higher compared to that of the α-type structure. This anomaly is conjectured to be a precursor to the antiferromagnetic transition and may be a particular feature of these “tiling” compounds with analogy to AlB2-type structure.
Strongly correlated electron behavior in R2Ru3Ga9 (R=Ce and U)
Authors: Kumar Neeraj , Shah K. V. , Nagalakshmi R. , Dhar S. K.
Published: April 2010

Using the techniques of magnetization, resistivity, and specific heat, we show evidence of strong electron correlations in orthorhombic R2Ru3Ga9 (R=Ce and U). U2Ru3Ga9 orders antiferromagnetically with TN=16.5 K, while the Ce analog shows Pauli paramagnetic, mixed valence behavior with a linear coefficient of the electronic heat capacity ∼250 mJ/mol K2. Their resistivity increases with decreasing temperature below 300 K, showing broad peaks in the ∼60–80 K range. Reduced effective paramagnetic moment and magnetic entropy suggest a low-moment state of uranium ions in U2Ru3Ga9 arising due to 5f-conduction electron hybridization. Simultaneously, the heat capacity data indicate an enhanced electronic heat capacity coefficient comparable to that of Ce2Ru3Ga9.
Spin density in frustrated magnets under mechanical stress: Mn-based antiperovskites
Authors: Lukashev Pavel , Sabirianov Renat F.
Published: April 2010

In this paper we present results of first-principle calculations of the noncollinear spin density distribution in the systems with frustrated triangular magnetic structure [Mn-based antiperovskites, Mn3AN (A=Ga,Zn)] in the ground state and under external mechanical biaxial strain. We show that the spin density in the (111)-plane of the unit cell is distinctly nonuniform. In particular, both the direction and the magnitude of spin density depend strongly on the distance from Mn site within atomic sphere. We show that the change of spin density under stress exhibits more diverse features than assumed in the rigid spin model. There are regions within atomic sphere where the spin density rotates in opposite directions under stress.
Exchange interaction in GdT2 (T=Fe,Co,Ni) from first-principles
Authors: Liu X. B. , Altounian Z.
Published: April 2010

The intersites exchange coupling parameters Jij of the Heisenberg model have been studied from a first-principles density functional plus Hubbard U approach calculation and a linear-response method for GdT2 Laves phase with T=Co, Fe, and Ni. The calculated magnetic moments of Gd are well localized and range from 7.3μB to 7.8μB, while the moments of Fe, Co, and Ni are −1.96μB, −1.19μB, and −0.11μB, respectively. The calculated effective exchange interaction parameters J0 of Gd sublattices are 2.62, 1.95, and 1.00 mRy, while those of T sublattices are 6.92, 4.37, and 0.00 mRy for T=Fe, Co, and Ni, respectively. The calculation results indicate that the magnetic ordering is dominated by the Gd sublattice in GdNi2, while the magnetic ordering is mainly determined by the Fe-sublattice in GdFe2.