bluuebunny/crossref_metadata_2025 huggingface dataset:
Spreading of overflow water from the Greenland to the Labrador Sea
Authors: Tanhua Toste , Bulsiewicz Klaus , Rhein Monika
Published: May 2005

In 1996, about 320 kg of SF6 were introduced in the center of the Greenland Sea gyre. We use this signal together with the CFC distribution to follow the spreading of Greenland gyre water from the Denmark Strait through the Irminger Basin and the Labrador Sea to the Grand Banks. In the summer of 2003 Denmark Strait Overflow Water tagged with deliberately released SF6 could be traced throughout the Irminger Basin to the central Labrador Sea, confirming that water with potential density of 28.045 contributes to the Denmark Strait Overflow. The upper limit of the transfer time from the central Greenland Sea to the Labrador Sea was found to be 7 years. This study suggests that roughly 4 kg of excess SF6 has been transported over the Denmark Strait and confirm earlier reported transport through the Faroe Bank Channel. These results should be considered when using SF6 as a transient tracer.
Reflection and tunneling of ocean waves observed at a submarine canyon
Authors: Thomson Jim , Elgar Steve , Herbers T. H. C.
Published: May 2005

Ocean surface gravity waves with periods between 20 and 200 s were observed to reflect from a steep‐walled submarine canyon. Observations of pressure and velocity on each side of the canyon were decomposed into incident waves arriving from distant sources, waves reflected by the canyon, and waves transmitted across the canyon. The observed reflection is consistent with long‐wave theory, and distinguishes between cases of normal and oblique angles of incidence. As much as 60% of the energy of waves approaching the canyon normal to its axis was reflected, except for waves twice as long as the canyon width, which were transmitted across with no reflection. Although waves approaching the canyon at oblique angles cannot propagate over the canyon, total reflection was observed only at frequencies higher than 20 mHz, with lower frequency energy partially transmitted across, analogous to the quantum tunneling of a free particle through a classically impenetrable barrier.
Key roles of hydrophobic rings of TM2 in gating of the α9α10 nicotinic cholinergic receptor
Authors: Plazas Paola V , De Rosa María J , Gomez‐Casati María E , Verbitsky Miguel , Weisstaub Noelia , Katz Eleonora , Bouzat Cecilia , Elgoyhen Ana Belén
Published: May 2005

We have performed a systematic mutagenesis of three hydrophobic rings (17′, 13′ and 9′) within transmembrane region (TM) 2 of the α9α10 nicotinic cholinergic receptor (nAChR) to a hydrophilic (threonine) residue and compared the properties of mutant receptors reconstituted in Xenopus laevis oocytes.

Phenotypic changes in α9α10 mutant receptors were evidenced by a decrease in the desensitization rate, an increase in both the EC50 for ACh as well as the efficacy of partial agonists and the reduction of the allosteric modulation by extracellular Ca2+.

Mutated receptors exhibited spontaneous openings and, at the single‐channel level, an increased apparent mean open time with no major changes in channel conductance, thus suggesting an increase in gating of the channel as the underlying mechanism.

Overall, the degrees of the phenotypes of mutant receptors were more overt in the case of the centrally located V13′T mutant.

Based on the atomic model of the pore of the electric organ of the Torpedo ray, we can propose that the interactions of side chains at positions 13′ and 9′ are key ones in creating an energetic barrier to ion permeation.

In spite of the fact that the roles of the TM2 residues are mostly conserved in the distant α9α10 member of the nAChR family, their mechanistic contributions to channel gating show significant differences when compared to other nAChRs. These differences might be originated from slight differential intramolecular rearrangements during gating for the different receptors and might lead each nAChR to be in tune with their physiological roles.

British Journal of Pharmacology (2005) 145, 963–974. doi:10.1038/sj.bjp.0706224
Lipids modulate ligand binding to sulphonylurea receptors
Authors: Klein Alexander , Lichtenberg Jochen , Stephan Damian , Quast Ulrich
Published: May 2005

ATP‐sensitive K+ channels (KATP channels) are complexes of inwardly rectifying K+ channels (Kir6.x) and sulphonylurea receptors (SURs). Kir6.2‐containing channels are closed by ATP binding to Kir6.2, and opened by MgADP binding to SUR. Channel activity is modulated by synthetic compounds such as the channel‐blocking sulphonylureas and the KATP channel openers, which both act by binding to SUR. By interacting with Kir6.2, phosphatidylinositol‐4,5‐bisphosphate (PIP2) and oleoyl‐coenzyme A (OCoA) decrease the ATP‐sensitivity of the channel and abolish the effect of the synthetic channel modulators. Here, we have investigated whether lipids and related compounds interfered with the binding of the sulphonylurea, glibenclamide (GBC) and of the opener, N‐cyano‐N′‐(1,1‐dimethylpropyl)‐N″‐3‐pyridylguanidine (P1075), to the SUR subtypes.

Lipids (100–300 μM) inhibited binding of [3H]GBC and [3H]P1075 to SUR subtypes in the rank order OCoA>dioleylglycerol‐succinyl‐nitriloacetic acid (DOGS‐NTA)>oleate>malonyl‐CoA>PIP2.

OCoA inhibited radioligand binding to SUR completely, with IC50 values ranging from 6 to 44 μM. Inhibition was reversed by increasing the concentration of the radioligands in agreement with an essentially competitive mechanism. MgATP and coexpression with Kir6.2 decreased the potency of OCoA.

DOGS‐NTA inhibited radioligand binding to SUR by 40–88%, with IC50 values ranging from 38 to 120 μM.

Poly‐lysine increased radioligand binding to SUR by up to 30% but did not affect much the inhibition of ligand binding by OCoA and DOGS‐NTA.

Radioligand binding to SUR2A but not to the other SUR subtypes was slightly (10–20%) stimulated by lipids at concentrations ∼10 × lower than required for inhibition.

The data show that certain lipids, at high concentrations, interact with SUR and inhibit the binding of GBC and P1075; with SUR2A, a modest stimulation of ligand binding precedes inhibition. Regarding KATP channel activity, these effects will be overruled by the interaction of the lipids with Kir6.2 at lower (physiological) concentrations. They are, however, of pharmacological importance and must be taken into account if high concentrations of these compounds (e.g. OCoA>10 μM) are used to interfere with the action of sulphonylureas and openers on KATP channel activity.

British Journal of Pharmacology (2005) 145, 907–915. doi:10.1038/sj.bjp.0706252
Bradykinin‐induced, endothelium‐dependent responses in porcine coronary arteries: involvement of potassium channel activation and epoxyeicosatrienoic acids
Authors: Weston Arthur H , Félétou Michel , Vanhoutte Paul M , Falck John R , Campbell William B , Edwards Gillian
Published: May 2005

In coronary arteries, bradykinin opens endothelial intermediate‐ and small‐conductance Ca2+‐sensitive K+ channels (IKCa and SKCa) and, additionally, releases epoxyeicosatrienoic acids (EETs) from the endothelium. To clarify the involvement of these pathways in endothelium‐dependent myocyte hyperpolarization, bradykinin‐induced electrical changes in endothelial cells and myocytes of porcine coronary arteries (following nitric oxide (NO) synthase and cyclooxygenase inhibition) were measured using sharp microelectrodes.

Hyperpolarization of endothelial cells by bradykinin (27.0±0.9 mV, n=4) was partially inhibited (74%) by blockade of IKCa and SKCa channels using 10 μM TRAM‐39 (2‐(2‐chlorophenyl)‐2,2‐diphenylacetonitrile) plus 100 nM apamin (leaving an iberiotoxin‐sensitive component), whereas the response to substance P was abolished.

After gap junction blockade with HEPES, (N‐(2‐hydroxyethyl)piperazine‐N′‐(2‐ethanesulphonic acid)) hyperpolarization of the endothelium by 100 nM bradykinin was abolished by TRAM‐39 plus apamin, whereas myocyte hyperpolarization still occurred (12.9±1.0 mV, n=4). The residual hyperpolarizations to 100 nM bradykinin were antagonized by the EET antagonist, 14,15‐EEZE (14,15‐epoxyeicosa‐5(Z)‐enoic acid) (10 μM), and abolished by iberiotoxin. Bradykinin‐induced myocyte hyperpolarizations were also reduced by 14,15‐EEZE‐mSI (14,15‐EEZE‐methylsulfonylimide) (5,6‐ and 14,15‐EET antagonist), whereas those to exogenous 11,12‐EET were unaffected.

These data show that bradykinin‐induced hyperpolarization of endothelial cells (due to the opening of IKCa and SKCa channels) is electrotonically transferred to the myocytes via gap junctions. Bradykinin (but not substance P) also hyperpolarizes myocytes by a mechanism (independent of endothelial cell hyperpolarization) which involves endothelial cell production of EETs (most likely 14,15‐ and/or 11,12‐EET). These open endothelial IKCa and SKCa channels and also activate large‐conductance calcium‐sensitive K+ channels (BKCa) on the surrounding myocytes.

British Journal of Pharmacology (2005) 145, 775–784. doi:10.1038/sj.bjp.0706256
New insights into adenosine‐mediated myocardial protection
Authors: Lasley Robert D
Published: May 2005

British Journal of Pharmacology (2005) 145, 701–702. doi:10.1038/sj.bjp.0706262
Metabolic and vascular actions of endothelin‐1 are inhibited by insulin‐mediated vasodilation in perfused rat hindlimb muscle
Authors: Kolka Cathryn M , Rattigan Stephen , Richards Stephen , Clark Michael G
Published: May 2005

Endothelin‐1 (ET‐1) is a potent endothelium‐derived vasoactive peptide and may be involved in the microvascular actions of insulin for the normal delivery of nutrients to muscle, although higher levels may be antagonistic.

Our aim was to observe the interaction between ET‐1 and insulin. Initially, we attempted to distinguish the vascular from the metabolic effects of ET‐1 in the constant‐flow pump‐perfused rat hindlimb by using various doses of ET‐1 and measuring changes in perfusion pressure (PP), oxygen consumption (VO2), glucose uptake (GU) and lactate release (LR). Sodium nitroprusside (SNP) was used to block vasoconstriction and to thus assess the relationship between vascular and metabolic effects. Insulin was included in later experiments to determine the interaction between insulin and ET‐1 on the above parameters.

ET‐1 caused a dose‐dependent increase in PP. Effects on VO2 were biphasic, with low doses increasing VO2, and higher doses leading to a net inhibition. GU and LR were increased at lower doses (ET‐1 1 nM), but this effect was lost at higher doses (10 nM ET‐1).

SNP (50 μM) fully blocked the increase in pressure and metabolism due to low‐dose ET‐1 and partly blocked both pressure and metabolic responses by the high dose. ET‐1 vasodilatory activity was minimal at high or low dose. Insulin (15 nM) alone caused GU, which was not affected by ET‐1. Of the other parameters measured, insulin behaved essentially the same as SNP, inhibiting the pressure and oxygen effects.

Overall, these results show that ET‐1 has a biphasic dose‐dependent vasoconstrictor effect on hindlimb blood vessels, able to modulate flow to cause both the stimulation and inhibition of metabolism, although these effects are blocked by insulin, which is able to vasodilate against both low and high doses of ET‐1.

British Journal of Pharmacology (2005) 145, 992–1000. doi:10.1038/sj.bjp.0706263
Embedded magnetics for microprocessor and multichip modules integrated power
Authors: Roshen Waseem A. , Korman Charlie S. , Daum Wolfgang
Published: May 2005

A new transformer/inductor technology is introduced which is suitable for integrated power for multichip modules (MCM) and microprocessors. The transformer/inductor is embedded within the ceramic substrate, as are the chips and other components. For core, multipole core structures are employed in order to meet extremely low height requirements. The windings are constructed using high-density interconnect techniques such as laminating dielectric layers and depositing winding metals using sputtering followed by electroplating. Winding patterns are etched using photoresist and wet etching techniques, and multiple vias are used to connect different primary and secondary winding layers. A conformal metal mask is used to laser-drill through (large) holes for the posts of the top part of the core. An experimental 50-W, six-pole embedded transformer is described. It operates at 1.0 MHz with an efficiency approaching 98.7% and has a net height of less than 0.09 in. It provides for extremely tight secondary side circuit layouts with very low and fixed leakage inductance.
Dynamic following of off-centered hard disk tracks in spin-stand imaging
Authors: Tseng C. , Mayergoyz I. , Tse C. , McAvoy P. , Krafft C.
Published: May 2005

A dynamic track-following technique has been developed that enables real-time reading of on-track data from off-centered hard disks on a spin stand. The technique makes use of piezoelectric transducers (PZT’s) to dynamically control the radial displacement of the read head to follow off-centered tracks. Controlling algorithms based on the Preisach model of hysteresis have been devised to compensate for the hysteretic effects of the PZT. Techniques for extracting the trajectories of off-centered hard disk tracks and special methods of selecting the initial phase of these tracks and locking the phase thereafter have also been developed. The track-following technique has been demonstrated to dynamically follow off-centered commercial hard disks with a track density of 90kilotrackperinch mounted on a spin stand.
Magneto-optic studies of garnets subject to rotating magnetic fields
Authors: Nistor Iulian , Mayergoyz I. D. , Krafft C.
Published: May 2005

This paper presents the study of the magneto-optical effects in garnets with in-plane magnetization under rotating magnetic fields. The samples are garnets of composition (LuBi)3(FeGa)5O12 epitaxially grown on (100) substrates. It is shown that the optical response of the samples can be used to precisely determine the orientation of the crystallographic axes. In addition, an optical method is presented to quantitatively measure the cubic crystalline anisotropy field.
Magnetoelectric effect in sputtered composites
Authors: Stein Simon , Wuttig Manfred , Viehland Dwight , Quandt Eckhard
Published: May 2005

The magnetoelectric effect in millimeter size PMN-PT∕Terfenol-D composites is known. In an effort towards miniaturization, we report on the magnetoelectric effect in micrometer-size sputtered composites. Multilayers of TbFe∕FeCo with a thickness of 4μm were sputter deposited on both sides of PMN-PT piezoelectric single crystals. The magnetoelectric voltage of samples was measured and reached values of 13mV∕(Oecm) at dc bias fields of 2mT, a linear dependence of magnetoelectric voltage on ac amplitude was detected in the range from 1mT to 1nT.
Gd
5
(
Si
,
Ge
)
4
and Gd2C compounds: Candidates for hyperthermia treatment of cancer
Authors: Ahmad S. N. , Akin Y. , Shaheen S. A.
Published: May 2005

A number of Gd based compounds have been investigated for their potential for use in hyperthermia treatment of cancer. The use of magnetic nanoparticles for producing local heating via alternating magnetic fields in cancer affected areas of the body has been an object of numerous studies in recent years. Whereas most studies have focused on using Fe and Co based nanoparticles, we have investigated a number of Gd compounds and alloys for their possible applications in hyperthermia treatment of cancer. Our results suggest that several of these alloys exhibit desired properties for such applications and may have advantages over Fe and Co based alloys for such applications.
Biocompatible suspension of nanosized γ-Fe2O3 synthesized by novel methods
Authors: Prasad N. K. , Panda D. , Singh S. , Mukadam M. D. , Yusuf S. M. , Bahadur D.
Published: May 2005

The present work deals with the synthesis of nanosized γ-Fe2O3 by methods and its suspension in a biocompatible fluid consisting of cellulose in water whose properties seem different from the conventional ferrofluid and magnetic rheological fluid. From TEM and x-ray diffractions line broadening particle size has been estimated in the nanometer range. Mössbauer and magnetic measurements have been done to investigate the relaxation behavior of these nanoparticles which consists of significant amount of surface spins. Biocompatibilities of suspensions have been confirmed using HeLa cell lines and can be suitable for different bioapplications.
Use of microscale coplanar striplines with indium tin oxide windows in optical ferromagnetic resonance measurements
Authors: Keatley P. S. , Kruglyak V. V. , Barman A. , Ladak S. , Hicken R. J. , Scott J. , Rahman M.
Published: May 2005

It is shown that a coplanar stripline structure containing indium tin oxide windows can be used to perform optical ferromagnetic resonance measurements on a sample grown on an opaque substrate, using a pulsed magnetic field of any desired orientation. The technique is demonstrated by applying it to a thin film of permalloy grown on a Si substrate. The measured precession frequency was found to be in good agreement with macrospin simulations. The phase of the oscillatory Kerr response was observed to vary as the probe spot was scanned across the coplanar stripline structure, confirming that the orientation of the pulsed field varied from parallel to perpendicular relative to the plane of the sample.
Effect of spin-valve sensor magnetostatic fields on nanobead detection for biochip applications
Authors: Ferreira H. A. , Feliciano N. , Graham D. L. , Freitas P. P.
Published: May 2005

Spin valves are being used in biochip applications via the detection of biomolecular recognition using magnetic nanoparticles as labels. The magnetic moment of the labels and the sensor response depend on the magnetic fields involved. A calculation based on an external magnetizing field, incorporating the contribution from the magnetostatic fields created by the free and pinned layers of the sensor and the field due to the sensing current, showed that these fields are important. Experimental detection signals of high particle numbers agree with the model, showing that reasonable detection signals are possible even in the absence of an external field.
Enhancing the force capability of permanent magnet latching actuators for electromechanical valve actuation systems
Authors: Rens J. , Clark R. E. , Jewell G. W. , Howe D.
Published: May 2005

This article introduces a topology of parallel-polarized permanent magnet latching actuator for use in electromagnetic valve actuation systems for internal combustion engines. The actuator has a number of advantages over reluctance actuators, commonly employed in such systems, in terms of reduced starting currents and fail-safe capability. The influence of a number of design features on actuator performance, such as tooth tapering, additional magnets to improve the main magnet flux path and prevent the onset of saturation, and mechanical clearances required to protect the permanent magnet from shock loads are investigated. The design study findings are verified by measurements on a prototype actuator.
Optimal design of fine magnetic pole pitch fabricated on printed circuit board
Authors: Chiu Kuo-Chi , Huang Der-Ray , Shieh Han-Ping D.
Published: May 2005

Using traditional methods, a permanent magnet multipole component magnetized with a magnetic pole pitch of less than 1mm is very difficult to achieve and a costly, complicated magnetization system is required. In this paper, the optimal design of a fine magnetic pole pitch of less than 1mm fabricated on a printed circuit board has been successfully investigated and demonstrated. An optimal magnetic pole pitch having large variation and strength in magnetic-flux density was obtained. The characteristics of the optimal magnetic pole pitch are good for signal detection and processing. The measured values of the magnetic-flux density in the z component are in agreement with the calculated values.
Investigation of pheophorbide∕magnetic fluid complex as a promising system for early cancer detection and treatment
Authors: Macaroff Patrícia P. , Oliveira Daniela M. , Lacava Zulmira G. M. , Lima Emília C. D. , Morais Paulo C. , Tedesco Antonio C.
Published: May 2005

The present work reports on a class of materials for the combined action of photodynamic therapy (PDT) and hyperthermia therapy (HPT). These materials are designed to work in a synergic way, leading to an expected enhancement of the tumor damage after minimum doses of heat dissipation and∕or light photosensitization. Pheophorbide-a (Pheo) has been studied and used for PDT with total absence of dark toxicity to cell by itself. Studies using biocompatible magnetic fluids (MFs) also indicate absence of toxicity without the application of ac magnetic field. The spectroscopic and photophysical properties of the Pheo∕MF were investigated to evaluate their photodynamic and HPT characteristics. The results clearly indicate that Pheo presents similar spectroscopic properties associated or not with the MF sample, working efficiently as a photodynamic drug in both conditions.
Electrochemical deposition of Fe1−xGax nanowire arrays
Authors: McGary P. D. , Stadler B. J. H.
Published: May 2005

Nanowires of the Fe–Ga alloy system, Fe1−xGax (0.1⩽x⩽0.25at.%), were fabricated using electrochemical deposition into nanoporous anodic alumina. Fe–Ga alloys are magnetically soft, mechanically robust, ductile, and have large magnetostriction. High aspect ratio nanowires with varying diameters and lengths were fabricated in arrays and were collectively and individually characterized using scanning electron microscopy and energy dispersive spectroscopy. The magnetic response of the array was also measured using vibrating-sample magnetometry. The Ga composition was controlled by optimizing deposition parameters such as ion concentration, buffer acids, agitation, and applied voltage. Through the analysis of pure Fe and pure Ga depositions, it was predicted that the Ga3+ ions would be depleted more quickly from the electrolyte than the Fe2+ ions. This hypothesis was supported by compositional analysis along alloy wires showing that the Ga composition decreased along the length of the wires.
Self-forming, quasi-two-dimensional, magnetic-fluid patterns with applied in-plane-rotating and dc-axial magnetic fields
Authors: Elborai S. , Kim D.-K. , He X. , Lee S.-H. , Rhodes S. , Zahn M.
Published: May 2005

We report flow instabilities with simultaneous, in-plane-rotating and dc-axial uniform magnetic fields. In uniform dc-axial magnetic fields, a ferrofluid drop in a Hele-Shaw cell with an∼1.0-mm gap forms the familiar labyrinth pattern. With subsequent application of an ∼100-G rms in-plane, 20–40-Hz rotating uniform magnetic field, smooth spirals form. If the rotating magnetic field is applied first, the drop holds together for low dc-axial magnetic fields and no labyrinth pattern develops. If the dc magnetic field is subsequently increased above a threshold value, the ferrofluid drop abruptly transforms into many ferrofluid droplets arranged in a regular pattern.
Static and dynamic properties of magnetic nanowires in nematic fluids (invited)
Authors: Lapointe C. , Cappallo N. , Reich D. H. , Leheny R. L.
Published: May 2005

Microscopy experiments are employed to characterize the elastic interactions of magnetic nickel nanowires suspended in a nematic liquid crystal. The nematic imposes a torque on an isolated wire that increases linearly with the angle between the wire and the nematic director in a manner quantitatively consistent with predictions based on an analogy between the nematic elasticity and electrostatics. An extension of this analogy also explains a measured orientation-dependent repulsive force between a wire and a wall. The angular relaxation of a wire in response to the elastic torque displays a nonexponential time dependence from which effective viscosities for the fluid are determined. The behavior of a wire in a twisted nematic cell further demonstrates how spatial variations in the director can convert the torque to a controlled translational force that levitates a wire to a specified height.
Defect detection in aluminum laser welds using an anisotropic magnetoresistive sensor array
Authors: Allweins K. , von Kreutzbruck M. , Gierelt G.
Published: May 2005

For the detection of defects in aluminum laser welds an anisotropic magnetoresistive (AMR) sensor array was implemented in an eddy current testing system. The reliability of weld testing is strongly influenced by the texture of the laser weld whose field response significantly superimposes the defect’s magnetic signature. A finite-element model was used to determine the influence of the weld’s topology on the detection of defects such as porosities and inclusions hosted in the aluminum matrix. When using an AMR sensor array with field sensitivity of better than 1nT∕√Hz defects with a radius smaller than 100μm could be detected and classified.
Optimal magnet shape to improve torque characteristics of interior permanent magnet synchronous motor
Authors: Lee Kab-jae , Kim KiChan , Kim Sol , Ahn Joon-Seon , Lim SeongYeop , Lee Ju
Published: May 2005

Permanent magnet (PM) motor is the best choice in the application to a hybrid vehicle. PM configuration is one of the critical design points for the application. This paper presents the effect of PM shapes on the motor performance, especially sinusoidal induced voltage. The proposed design by finite element method has been confirmed by comparing emf wave form, harmonics, reluctance torque, and rated torque between conventional and models. Quantitative comparison of the characteristics for interior permanent magnet synchronous motor of four models is shown. The four models are lateral magnet, V-shape magnet, modified V-shape magnet, and C-shape magnet.
Dynamic susceptibility investigation of biocompatible magnetic fluids: The surface coating effect
Authors: Morais P. C. , Santos J. G. , Silveira L. B. , Oliveira A. C.
Published: May 2005

In this study room-temperature dynamic susceptibility measurements were used to investigate magnetite nanoparticles surface-coated with dextran and dimercaptosuccinic acid, both dispersed as biocompatible magnetic fluids. Multicomponent susceptibility curves were associated with the presence of monomers and dimers in the sample. Transmission electron microscopy data have been used to support the analysis carried out with the susceptibility data. The field dependence of the peak position of the imaginary component of the dynamical susceptibility was analyzed within the picture of an asymmetric double-well potential for the relaxation of the magnetic moment associated with the magnetite nanoparticle. The nanoparticle size dependence of the susceptibility peak position was taken into account in the data analysis. Nanoparticle-size parameters obtained from the analysis of the susceptibility data of the two samples (3.7 and 6.1nm) are in very good agreement with the values obtained from the fitting of the electron microscopy data (3.1 and 5.6nm).
Comparison of performance of the axial-field and radial-field permanent magnet brushless direct current motors using computer aided design and finite element methods
Authors: Upadhyay P. R. , Rajagopal K. R.
Published: May 2005

In this article, performance of 70 W, 350 rpm, axial-field and radial-field permanent magnet brushless dc motors is compared using computer aided design (CAD) and finite element (FE) methods. The design variables like number of poles, slots per pole per phase, airgap length, airgap flux density, slot electric loading, stator flux density, and the permanent magnet material are changed one at a time and the performances are calculated using the developed CAD program. The CAD results are validated by carrying out two-dimensional and three-dimensional FE analyses. It is observed that the axial-field motor gives higher efficiency, whereas the radial-field motor has less weight.
Development of a highly efficient hard disk drive spindle motor with a passive magnetic thrust bearing and a hydrodynamic journal bearing
Authors: Jang G. H. , Park J. S.
Published: May 2005

This article presents a highly efficient hard disk drive (HDD) spindle motor with a passive magnetic thrust bearing and a hydrodynamic journal bearing. It eliminates the mechanical friction loss of a thrust bearing which is around 14% of total power consumption of a 3.5 in. HDD spindle motor, by replacing a conventional hydrodynamic thrust bearing with a passive magnetic thrust bearing. The passive magnetic thrust bearing using permanent magnets is inherently unstable in radial direction. However, the radial hydrodynamic force of the hydrodynamic journal bearing counterbalances the radial magnetic force of magnetic thrust bearing to achieve the stability as the motor spins up. Numerical analysis is performed to verify feasibility of the proposed system.
Role of organic coating on carbonyl iron suspended particles in magnetorheological fluids
Authors: Jang I. B. , Kim H. B. , Lee J. Y. , You J. L. , Choi H. J. , Jhon M. S.
Published: May 2005

Carbonyl iron (CI) has been widely used as a suspended particle in magnetorheological (MR) fluids. However, pristine CI-based MR fluids have several drawbacks, including severe sedimentation of the CI particles due to the large density difference with the carrier liquid, difficulties in redispersion after caking, abrasion of device surfaces during long-term operation, and rust of iron by oxidation. To overcome these shortcomings, we coated the CI particles with a poly(vinyl butyral) (PVB) shell. CI and CI-PVB particles were suspended in mineral oil and their MR characteristics were examined via a rotational rheometer in a parallel plate geometry equipped with a magnetic field supplier. Yield stress and flow response (shear stress and shear viscosity) were investigated at magnetic field strengths ranging from 0to343kA∕m. Although the MR properties, such as yield stress and shear viscosity of CI-PVB based MR fluids, changed slightly compared with those of the pristine CI based MR fluid, the dispersion qualities (e.g., sedimentation stability) were noticeably improved.
Magnetoelastic bending of Galfenol for sensor applications
Authors: Downey P. R. , Flatau A. B.
Published: May 2005

This project investigates the behavior of iron–gallium (Galfenol) alloys in elastic bending to facilitate the design concepts for using Galfenol in novel sensor applications at the macro to nanoscale. A series of experiments are conducted on the magnetic response of cantilevered beams to dynamic bending loads. The samples studied include polycrystalline and single crystal rods of varied dimension with compositions ranging from 16to21at%Ga. Results of initial testing show that sinusoidal bending produces measurable induction that increases with applied magnetic bias. Other results examine the effect of material composition and sensor location, as well as the broadband response.
Design and fabrication of a gold electroplated electromagnetic and electrostatic hybrid MEMS relay
Authors: Guan Shan , Vollmers Karl , Subramanian Arunkumar , Nelson Bradley J.
Published: May 2005

This paper reports on a gold electroplated hybrid microrelay that combines the advantages offered by electromagnetic and electrostatic actuation mechanisms. The microrelay design achieves signal by out-of-plane motion of a contact cross-bar fabricated on a diaphragm fixed at both ends to short the isolated input and output contacts. Major factors influencing the design approach include low contact resistance in the closed state, high signal isolation in the open state, latching upon loss of power, and fabrication robustness and cost. The MEMS device is surface micromachined with structures fabricated by electroplating gold through photoresist masks. Experimental results show that 95% of the devices can be actuated and ≈50% of them pass signal. The average contact resistance is about 170mΩ and the system isolation is 70dB at 20MHz when a gold ground plane is added.
Imaging of the dielectric resonance effect in high field magnetic resonance imaging
Authors: Mihara Hiroaki , Iriguchi Norio , Ueno Shoogo
Published: May 2005

At a high field magnetic resonance imaging (MRI), the interactions between the RF pulse and the high permittivity samples, which cause the B1 field inhomogeneity, can no longer be negligible. We present a postprocessing method of compensating the B1 field inhomogeneity mainly caused by the dielectric resonance. The intensity of the transmitted B1 field is calculated using two spin echo images of the water phantom obtained with different flip angles 45° and 90°. Applying the proposed method, the dielectric resonance of the water in high field MRI is visualized as a quantitative map of the B1 field. The corrected image compensating the B1 field inhomogeneity was also calculated.
Influence of slot number and pole number in fault-tolerant brushless dc motors having unequal tooth widths
Authors: Ishak D. , Zhu Z. Q. , Howe D.
Published: May 2005

The electromagnetic performance of fault-tolerant three-phase permanent magnet brushless dc motors, in which the wound teeth are wider than the unwound teeth and their tooth tips span approximately one pole pitch and which have similar numbers of slots and poles, is investigated. It is shown that they have a more trapezoidal phase back-emf wave form, a higher torque capability, and a lower torque ripple than similar fault-tolerant machines with equal tooth widths. However, these benefits gradually diminish as the pole number is increased, due to the effect of interpole leakage flux.
Iron loss prediction under pulse width modulated conditions
Authors: Moses I. A. J. , Leicht J.
Published: May 2005

This paper illustrates the state of art of magnetic testing of electrical steels under distorted flux wave forms, gives comparisons of performance of various motor steels and introduces a loss prediction approach based on the linear relationship between iron loss produced under sinusoidal flux and that produced under pulse width modulated (PWM) excitation. Results are very promising showing agreement between measured and predicted losses in a wide range of electrical steels magnetized under various PWM wave forms to within 5%.
Mechanical work associated with the creation of circumferentially polarized bands
Authors: Garshelis Ivan J. , Tollens Stijn P. L.
Published: May 2005

The relationship between mechanical work expended in rotating a steel shaft in the field of a proximate magnet and the intensity and homogeneity of the resulting circumferential remanent magnetization in peripheral regions of the shaft is explored. The work, manifested as a drag torque on the shaft, is shown to supply the hysteretic energy lost within affected regions of the shaft. The torque arises from the tangential force accompanying the rotation induced magnetization asymmetry. The force is universally found to rise during an initial small angular rotation and subsequently diminish to a stable value over some number of shaft revolutions.
Terfenol-D tooth phone performance characterization and optimization
Authors: Staley Mark E. , Flatau Alison B.
Published: May 2005

A Terfenol-D transducer has been developed for use as a tooth phone with both sensing and actuating capabilities by Audiodontics, Inc. This research focuses on characterizing the sensitivity of the tooth phone’s magnetostrictive Terfenol-D rod performance in both sensor and actuator modes to changes in the initial prestress of the device. A test apparatus was designed to allow prestress variability while operating the transducer as either a sensor or an actuator. To assess the sensor-mode performance, a force-feedback loop control system was used to excite the tooth phone with a constant force from a mechanical shaker at the tooth–tooth phone interface surface while measuring the voltage generated in the transducer’s coil. The shaker was driven with a 200Hzto7kHz swept sine at various dynamics force loadings for prestresses ranging from 0.25to3.5ksi. The results indicate a prestress of 2ksi offers the best sensor-mode performance. To assess the actuator performance, a accelerometer was attached to the tooth–tooth phone interface surface and output acceleration was recorded while sweeping the tooth phone excitation frequency from 200Hzto7kHz with zero-to-peak voltages of 0.1, 0.3, and 0.5V. The prestress settings were varied from 0.3to3.25ksi. As an actuator, no prestress offered a significant broadband performance advantage. Finally, comparisons were made of the tooth phone and an accelerometer for measuring tooth vibrations induced during humming. They perform similarly and capture much of the frequency content found in concurrently recorded microphone data.
The influence of various coatings on the electronic, magnetic, and geometric properties of cobalt nanoparticles (invited)
Authors: Hormes J. , Modrow H. , Bönnemann H. , Kumar C. S. S. R.
Published: May 2005

From the results reported here for Co nanoparticles coated with 3-(N,N-dimethyl-dodecylammonium)- propanesulfonate (SB12), Cu, or Au, and from experimental and theoretical results published by several other groups there is strong evidence that the various coatings (organic as well as inorganic) not just influence but even determine the properties of small metallic nanoparticles. In an empirical manner, the core-coating interaction is already used to influence the size and the shape of nanoparticles. Based on previously published results and some experiments, in this paper the influence is described that various coatings have on the geometric, electronic, and magnetic properties of cobalt nanoparticles with diameters smaller than 10nm. The results indicate that there is an interdependence of various properties (e.g., size and electronic properties of a particle with the same coating) so that is seems to be difficult to vary one property in a systematic way without changing others.
Computation of current densities in the receiving mode of electromagnetic acoustic transducers
Authors: Jafari Shapoorabadi R. , Konrad A. , Sinclair A. N.
Published: May 2005

This paper presents in detail the mathematical equations describing electrodynamic current densities in receiving electromagnetic acoustic transducers (EMATs) in Cartesian coordinates and employs the finite element method to calculate the dynamic magnetic field produced by these current densities. The current densities generated in EMAT receivers are basically functions of the static magnetic-field and particle displacement vector components. Past attempts to analyze EMATs with ferromagnetic specimens failed to account for skin and proximity effects. In this paper, skin and proximity effects are properly taken into account in the modeling of EMAT receivers.
Computer aided design of multi-phase switched reluctance motor
Authors: Sheth N. K. , Rajagopal K. R.
Published: May 2005

In this paper, a comprehensive computer-aided design (CAD) procedure of multiphase switched reluctance motor (SRM) is presented. Better approach for calculation of the outer dimensions, phase inductance, flux linkage and losses, and also a different concept for calculating the average torque of the motor are incorporated in the CAD program. The average torque is calculated based on the most effective 15° (for 8∕6 SRM) of the static torque profile of the motor. A sample design of a 5hp SRM is presented in detail and the design is validated by conducting a two-dimensional finite element analysis of the motor.
Vector characterization of soft magnetic materials
Authors: Lin Z. W. , Lu H. W. , Zhu J. G. , Zhong J. J. , Wang X. L. , Ding S. Y.
Published: May 2005

A three-dimensional (3D) magnetic property testing system has been completed and successfully used to measure 3D hysteresis loci of soft magnetic material. This paper presents the techniques to characterize soft magnetic materials under 3D magnetic excitations in detail. Using three couples of excitation coils controlled by a computer to generate the magnetic fields in three orthogonal axes, various types of flux density loci, such as circular or elliptical rotating vectors of flux density with any given orientations in 3D space, can be obtained. Based on 3D finite element analysis and a comparative study, a sandwich arrangement comprising a sample, guard pieces, and search coils with double-layer structure was proposed. Compared with the conventional surface search coils, this arrangement can significantly improve the accuracy of measurement. The comprehensive calibration process and the experimental results of the 3D hysteresis loci of soft magnetic composite materials are also presented.
Crystallographic analysis of CoPtCr-SiO2 perpendicular recording media with high anisotropy using synchrotron radiation x-ray diffraction
Authors: Kubo T. , Kuboki Y. , Ohsawa M. , Tanuma R. , Saito A. , Oikawa T. , Uwazumi H. , Shimatsu T.
Published: May 2005

A CoPtCr-SiO2 film is a potential material for high-density perpendicular recording media due to their high magnetic anisotropy constant Ku. However, the value of Ku decreases in high levels of Pt content. In this study, this phenomenon was analyzed by synchrotron radiation grazing incidence x-ray diffraction and transmission electron microscopy techniques. Although the CoPtCr-SiO2 films contained almost no fcc phase at 20at.% Pt or less, it increased remarkably at 30at.% Pt. This result coincided with the variations of Ku with respect to the Pt content for the CoPtCr-SiO2 films. We consider that the fcc phase formation at Pt content levels in the vicinity of 30at.% is an influential factor of the Ku reduction. Our techniques proved to be sensitive for the detection of fcc regions in the CoPtCr-SiO2 films.
Preparation and electrical properties of oil-based magnetic fluids
Authors: Sartoratto P. P. C. , Neto A. V. S. , Lima E. C. D. , Rodrigues de Sá A. L. C. , Morais P. C.
Published: May 2005

This paper describes an improvement in the preparation of magnetic fluids for electrical transformers. The samples are based on surface-coated maghemite nanoparticles dispersed in transformer insulating oil. Colloidal stability at 90°C was higher for oleate-grafted maghemite-based magnetic fluid, whereas decanoate and dodecanoate-grafted samples were very unstable. Electrical properties were evaluated for samples containing 0.80%–0.0040% maghemite volume fractions. Relative permittivity varied from 8.8 to 2.1 and the minimum value of the loss factor was 12% for the most diluted sample. The resistivity falls in the range of 0.7–2.5×1010Ωm, whereas the ac dielectric strength varied from 70to79kV. These physical characteristics reveal remarkable step forward in the properties of the magnetic fluid samples and may result in better operation of electrical transformers.
Monitoring the fatigue state of steel by evaluating the quasistatic and dynamic magnetic behavior
Authors: Vandenbossche Lode , Dupré Luc , Melkebeek Jan
Published: May 2005

For the evaluation of fatigue damage progression the application of quasistatic and dynamic magnetic measurements combined with the Preisach hysteresis model and the statistical loss theory is investigated. Throughout the fatigue lifetime hysteresis and excess magnetic behavior, both known to be sensitive to microstructural variations, are monitored. The magnetic evaluation results for fatigue tests executed on two steels depend on their initial microstructure and chemical composition. In addition the effect of low stress amplitude cyclic loading on the magnetic properties of electrical steel is investigated: after 1000cycles the excess losses are slightly decreased, while hysteresis properties stay invariant.
Development of high permeability nanocrystalline permalloy by electrodeposition
Authors: Seet H. L. , Li X. P. , Zhao Z. J. , Kong Y. K. , Zheng H. M. , Ng W. C.
Published: May 2005

In this study, for developing microsensors for weak magnetic field, methods for developing high permeability nanocrystalline permalloy by electrodeposition and the relationship between the grain size and magnetic properties of the nanocrystalline permalloy are investigated. By dc plating with and without saccharin added and pulse plating with saccharin added, permalloy samples of grain sizes from 52 nm to 11 nm are obtained. The coercivity and magnetoimpedance (MI) ratio of the samples are tested against the grain size variation. Results show that the coercivity decreases rapidly and MI ratio increases greatly with grain size decrease from 52 nm to 11 nm.
Critical-field curves for switching toggle mode magnetoresistance random access memory devices (invited)
Authors: Fujiwara H. , Wang S.-Y. , Sun M.
Published: May 2005

The magnetization behavior of generalized synthetic antiferromagnet (SAF) is investigated by analytic/numeric method, applying Stoner–Wohlfarth model to each layer. Critical conditions for toggle-mode switching are given using the critical-field curves obtained from the field trajectories giving a constant value to the average angle of the magnetizations of the two layers or to the angle between the two, leaving the other variable. The critical fields for the toggle operation are found to be expressed by analytical formulas including only controllable element parameters, facilitating the parameter optimization for the memory element. The results obtained for the generalized SAF are useful in determining the tolerance for the parameter imbalance. Half-select disturb effect is still one of the important issues to be taken into account in designing the memory element.
Nondegenerate ultrametric diffusion
Authors: Kozyrev S. V. , Osipov V. Al. , Avetisov V. A.
Published: May 2005

The general non-degenerate p-adic operators of ultrametric diffusion are introduced. Bases of eigenvectors for the introduced operators are constructed and the corresponding eigenvalues are computed. The long-time relaxation behavior of the ultrametric diffusion generated by the introduced operators are investigated.
Slanted and saw-toothed stator poles for improved performance of doubly salient permanent magnet motor
Authors: Babu A. R. C. Sekhar , Rajagopal K. R.
Published: May 2005

This paper presents the results of extensive finite element analyses conducted on doubly salient permanent magnet motor (DSPM) for improving the torque characteristics by novel methods; namely (i) slanted stator pole and (ii) saw-toothed stator pole. In the first method, stator poles are given a slant at the pole face; the slant in a direction opposite to the rotation of the motor has resulted in 7.33% and 71.45% increase in the average and maximum torques, respectively, when compared with the motor with original stator poles. With appropriate saw-tooth shaped stator poles, various permanent magnet torque and static torque profiles can be achieved.
Magnetic materials for finite-temperature quantum computing
Authors: Skomski R. , Zhou J. , Istomin A. Y. , Starace A. F. , Sellmyer D. J.
Published: May 2005

The potential use of interacting magnetic nanodots for quantum computing (qubit) operations is investigated by model calculations. The quantum entanglement of the low-lying ferromagnetic states, as quantified by the concurrence, exhibits a resonant peak whose position and width depend on parameters such as dot anisotropy, interdot exchange, and external field gradient. The maximum operation temperature is proportional to the magnetocrystalline anisotropy of the dot material. A specific condition is that the dots are sufficiently small so that the interatomic exchange ensures a coherent magnetization state and quantum coherence at finite temperatures. From a material point of view, there is a quite rigid upper limit of about 100 K, but to avoid decoherence it will be necessary to sacrifice a substantial fraction of this temperature, probably at least one order of magnitude.