bluuebunny/crossref_metadata_2025 huggingface dataset:
Cyclophilin D: Knocking On Death’s Door
Authors: Schneider Michael D.
Published: June 2005

Two recent genetic studies have identified a critical role for cyclophilin D, a component of the mitochondrial membrane permeability transition pore, in cell death induced by calcium, reactive oxygen species, and cardiac ischemia-reperfusion injury. Transgenic mice lacking cyclophilin D developed normally but showed reduced infarct size after coronary artery ligation and reperfusion. Cells from the knockout mice were resistant to death imposed by excess calcium and H
2
O
2
, but not to death from x-irradiation, staurosporine, tumor necrosis factor–α, or forced expression of proapoptotic proteins. These data raise questions about the relationship between apoptotic and necrotic cell death, and they also highlight cyclophilin D as a potential therapeutic target in myocardial infarction.
Focus Issue: Women’s Health
Authors: Ray L. Bryan , Adler Elizabeth M. , Gough Nancy R.
Published: June 2005

This week’s issues of
Science
and
Science’
s STKE concern health-related issues that are specifically pertinent to women. Topics at STKE include cell signaling pathways through which human papillomaviruses promote the development of cervical cancer and the role of membrane-associated signaling pathways in the anti-inflammatory effects of estrogen and the beneficial actions of estrogen on cardiovascular function.
Crossroads of Estrogen Receptor and NF-κB Signaling
Authors: Biswas Debajit K. , Singh Sindhu , Shi Qian , Pardee Arthur B. , Iglehart J. Dirk
Published: June 2005

Cellular homeostasis in higher organisms is maintained by balancing cell growth, differentiation, and death. Two important systems that transmit extracellular signals into the machinery of the cell nucleus are the signaling pathways that activate nuclear factor κB (NF-κΒ) and estrogen receptor (ER). These two transcription factors induce expression of genes that control cell fates, including proliferation and cell death (apoptosis). However, ER has anti-inflammatory effects, whereas activated NF-κB initiates and maintains cellular inflammatory responses. Recent investigations elucidated a nonclassical and nongenomic effect of ER: inhibition of NF-κB activation and the inflammatory response. In breast cancer, antiestrogen therapy might cause reactivation of NF-κB, potentially rerouting a proliferative signal to breast cancer cells and contributing to hormone resistance. Thus, ER ligands that selectively block NF-κB activation could provide specific potential therapy for hormone-resistant ER-positive breast cancers.
Rapid, Estrogen Receptor–Mediated Signaling: Why Is the Endothelium So Special?
Authors: Kim Kyung Hee , Bender Jeffrey R.
Published: June 2005

Classical, ligand-activated genomic effects of estrogen receptors (ERs) were once thought to mediate all estrogen responses. It is now accepted that rapid, nongenomic responses, mediated by ER-containing membrane complexes, occur in many tissues. The endothelium is a major target of such responses and is the critical regulatory tissue that, when normally functional, determines a state of "vascular health." When dysfunctional, the phenotypic and functional alterations result in vascular pathology, the most common form of which is atherosclerosis. Nitric oxide (NO) is a vascular protective substance generated by endothelial NO synthase (eNOS) in endothelial cells. The engagement of membrane ERs by 17β-estradiol (E2) is a potent stimulus to eNOS activation and NO release. Here, we describe the multimolecular components of ER-containing membrane complex assembly and the mechanisms directing ER targeting to caveolae microdomains in the plasma membrane. We discuss the possibility that various ERα splice forms, expressed in endothelial cells, may be particularly efficient signal transducers and may use classical receptor domains for membrane targeting and insertion. Finally, we discuss the biomedical ramifications of ER-mediated endothelial activation, including the controversies surrounding hormone replacement therapy and cardiovascular disease.
Human Papillomaviruses and Cell Signaling
Authors: McCance Dennis J.
Published: June 2005

Human papillomaviruses cause cancer of the stratified epithelium, and the incidence of infection with these viruses in the genital tract is high. The alterations in the biology of normal epithelial cells that lead to malignancy are a consequence of the activity of certain viral proteins, whose function is to create an environment conducive to the replication of the viral genome through inhibition of epithelial cell differentiation and stimulation of proliferation.
Oxygen Sensing: Getting Pumped by Sterols
Authors: Emerling Brooke M. , Chandel Navdeep S.
Published: June 2005

Oxygen plays a pivotal role in the maintenance of life for all eukaryotes, with the exception of strict anaerobes. Eukaryotes have developed mechanisms to sense and respond to decreased oxygen levels. How eukaryotes sense oxygen is still not fully understood. What is (or are) the oxygen sensor(s)? This question has vital physiological and pathophysiological implications, because all living aerobic organisms have adaptive mechanisms to maintain oxygen homeostasis. A recent report describes a novel eukaryotic oxygen-sensing mechanism in the fission yeast
Schizosaccharomyces pombe
, involving the depletion of sterols as a trigger to induce gene expression in response to decreased oxygen levels. It is not yet clear whether this mechanism is involved in the mammalian response to hypoxia, possibly in conjunction with activation of one or both of the hypoxia-inducible factor (HIF-1 or HIF-2) transcription factors.
A Moving New Role for the Sodium Pump in Epithelial Cells and Carcinomas
Authors: Kaplan Jack H.
Published: June 2005

The Na,K-ATPase, or sodium pump, is a ubiquitous plasma membrane protein in higher eukaryotes, including humans, that carries out the coupled active transport of Na
+
ions out of the cell and of K
+
ions into the cell, using the energy of hydrolysis of adenosine triphosphate. In recent years, it has been suggested that that this protein may also be involved in various other functions, such as transducing information from the extracellular milieu to intracellular signaling pathways, much like a growth factor receptor. It has also been suggested that the sodium pump may be essential to the formation and function of junctional complexes in epithelial cells, and, most recently, it has been shown to play a role in epithelial cell motility. Maloney sarcoma virus–transformed Madin Darby canine kidney cells have depressed Na,K-ATPase β subunit abundance and enhanced motility as compared with untransformed cells. Repletion of Na,K-ATPase β subunits in the transformed cells results in suppression of motility. The most recent work, discussed here, demonstrates that the Na,K-ATPase α and β subunits play distinct and separate roles, interacting with proteins in the phosphatidylinositol 3-kinase pathway and leading to the remodeling of the cytoskeleton and lamellipodia formation. The sodium pump subunits thus seem to play a role in regulating carcinoma cell motility and may be involved in cell motility suppression in many epithelial cells.
Nuclear Transactivators and Repressors
Authors: Pan Zhen-Qiang
Published: June 2005

This Teaching Resource provides lecture notes and slides for a class covering the mechanism and regulation of eukaryotic gene transcription machinery and is part of the course "Cell Signaling Systems: A Course for Graduate Students." This lecture begins with an overview of eukaryotic gene transcription and provides discussions regarding the current models of mechanisms of transcription by RNA Polymerase II (Pol II). Recent views on the action of Mediator will also be discussed. Finally, a detailed study will be presented to provide evidence for a role for enhancer-promoter communication in gene activation.
Mutagenesis Analysis of a Conserved Region Involved in Acetyl Coenzyme A Binding in the Aminoglycoside 6′-
N
-Acetyltransferase Type Ib Encoded by Plasmid pJHCMW1
Authors: Pourreza Atousa , Witherspoon Mavee , Fox Jessica , Newmark Jason , Bui Duyen , Tolmasky Marcelo E.
Published: June 2005

Alanine scanning of motif A in the pJHCMW1-encoded aminoglycoside 6′-
N
-acetyltransferase type Ib identified amino acids important for the ability of the enzyme to confer wild-type levels of resistance to kanamycin and amikacin. The replacement of two amino acids, D117 or L120, with alanine residues resulted in complete loss of the resistance phenotype.
Association between Resistance to Erythromycin and the Presence of the Fibronectin Binding Protein F1 Gene,
prtF1
, in
Streptococcus pyogenes
Isolates from German Pediatric Patients
Authors: Haller Maria , Fluegge Kirsten , Arri Sandra Jasminder , Adams Brit , Berner Reinhard
Published: June 2005

A total of 301 German pediatric group A streptococcus isolates were screened for the presence of macrolide resistance and the fibronectin binding protein F1 gene (
prtF1
) encoding an adhesin and cell invasiveness protein. The
prtF1
gene was present significantly more often among macrolide-resistant isolates. The majority of these were not clonally related.
In Vitro Activity of an Oral Streptogramin Antimicrobial, XRP2868, against Gram-Positive Bacteria
Authors: Eliopoulos G. M. , Ferraro M. J. , Wennersten C. B. , Moellering R. C.
Published: June 2005

The comparative in vitro potency of XRP2868, a new oral semisynthetic streptogramin antibiotic, was evaluated against gram-positive bacteria. XRP2868 inhibited all staphylococci at ≤1 μg/ml and all nonpneumococcal streptococci at ≤0.25 μg/ml and was fourfold more potent than quinupristin-dalfopristin against
Staphylococcus aureus
and
Enterococcus faecium
.
Cooperative Uptake of Microcin E492 by Receptors FepA, Fiu, and Cir and Inhibition by the Siderophore Enterochelin and Its Dimeric and Trimeric Hydrolysis Products
Authors: Strahsburger Erwin , Baeza Marcelo , Monasterio Octavio , Lagos Rosalba
Published: June 2005

Microcin E492 uptake by FepA, Fiu, and Cir is cooperative, with FepA being the main receptor. No TonB-mediated interaction with the ferric catecholate receptors is needed for microcin to exert action at the cytoplasmic membrane. Microcin E492 uptake by the receptors is inhibited by the dimer and trimer of dihydroxybenzoylserine.
EQUILIBRIUM STATES AND THEIR ENTROPY DENSITIES IN GAUGE-INVARIANT C*-SYSTEMS
Authors: AKIHO NOBUYUKI , HIAI FUMIO , PETZ DÉNES
Published: June 2005

A gauge-invariant C*-system is obtained as the fixed point subalgebra of the infinite tensor product of full matrix algebras under the tensor product unitary action of a compact group. In this paper, thermodynamics is studied in such systems and the chemical potential theory developed by Araki, Haag, Kastler and Takesaki is used. As a generalization of quantum spin system, the equivalence of the KMS condition, the Gibbs condition and the variational principle is shown for translation-invariant states. The entropy density of extremal equilibrium states is also investigated in relation to macroscopic uniformity.
QUANTIZATION METHODS: A GUIDE FOR PHYSICISTS AND ANALYSTS
Authors: ALI S. TWAREQUE , ENGLIŠ MIROSLAV
Published: June 2005

This survey is an overview of some of the better known quantization techniques (for systems with finite numbers of degrees-of-freedom) including in particular canonical quantization and the related Dirac scheme, introduced in the early days of quantum mechanics, Segal and Borel quantizations, geometric quantization, various ramifications of deformation quantization, Berezin and Berezin–Toeplitz quantizations, prime quantization and coherent state quantization. We have attempted to give an account sufficiently in depth to convey the general picture, as well as to indicate the mutual relationships between various methods, their relative successes and shortcomings, mentioning also open problems in the area. Finally, even for approaches for which lack of space or expertise prevented us from treating them to the extent they would deserve, we have tried to provide ample references to the existing literature on the subject. In all cases, we have made an effort to keep the discussion accessible both to physicists and to mathematicians, including non-specialists in the field.
ELECTRORHEOLOGY OF MONODISPERSE CORE/SHELL STRUCTURED PARTICLE SUSPENSIONS
Authors: CHOI H. J. , CHO M. S. , LEE I. S.
Published: June 2005

As a novel candidate of electrorheological (ER) material, core/shell composite particles (PAPMMA) of poly(methyl methacrylate) (PMMA) core and polyaniline (PANI) shell were prepared and adopted as a dispersed phase. PAPMMA particles, obtained by a dispersion polymerization method, were spherical and possessed a monodisperse particle size distribution, in which the PANI shell was introduced on the surface of PMMA via an in-situ polymerization of aniline by adding an oxidant in an aqueous acidic solution. Yield stress of the PAPMMA suspensions under an applied electric field was observed to be increased with a particle size. In addition, monodisperse acrylic microspheres with aniline moiety on the surface were prepared by a seeded emulsion method, and then composite particles possessing chemically bonded PANI shell (PA-PGMA) were prepared via an in-situ polymerization of aniline. Their ER characteristics were also examined.
ELECTRORHEOLOGICAL FLUIDS BASED ON MODIFIED POLYACRYLONITRILE
Authors: KRZTON-MAZIOPA ANNA , TUROWSKI MICHAL , PLOCHARSKI JANUSZ
Published: June 2005

An electrorheological (ER) effect in suspensions of solid particles is related to electric polarization processes within the bulk of grains of the solid phase or/and on their surface. The nature of these processes is governed by dopants, functional groups or structure of the solid particles and the solid-liquid interface. The purpose of our investigations was to find correlations between material properties of the solid phase and the parameters of the ER effect. We focused on the role of electrical conductivity and permittivity of the dispersed phase as well as chemical nature of surface groups. As the solid phase we chose an acrylic copolymer whose properties were modified by pyrolysis in controlled conditions or by doping with a salt, and silicone oil as the liquid matrix. The prepared materials were characterized by physical and chemical methods. The impedance spectroscopy was applied to estimate the electric conductivity and permittivity of the prepared materials. The characterized powders were then dispersed in silicone oil and their flow curves in the presence of electric field were recorded. The values of yield stress of the ER fluids containing pyrolized materials ranged from 40 Pa to 300 Pa at 3kV/mm for 15% w/w concentrations of solids. The ER effect of the ionic material suspensions was strongly influenced by salt concentration in the polymer. It was also found that samples of higher electronic conductivity exhibited higher currents in comparison to other samples but not higher shear stresses. The current densities in the ionic materials suspensions were significantly lower than in the annealed samples. Pyrolized and oxidized polyacrylonitrile samples contained polar functional groups. Some of the samples were chemically treated in order to modify polarity of the functional groups and the influence of this treatment on the ER effect was studied.
CONJUGATED POLYMERS AS ACTIVE COMPONENTS OF ELECTRORHEOLOGICAL FLUIDS
Authors: PLOCHARSKI JANUSZ , GOZDALIK ANNA , KRZTON-MAZIOPA ANNA , WYCISLIK HENRYK
Published: June 2005

ER properties of suspensions of four conjugated polymers - polyaniline, polyphenylene, polythiophene and pyrolysed polyacrylonitrile - in relation to their electric properties and chemical nature were studied. The polymer samples were synthesized and characterized by various methods and flow curves of their mixtures with silicone oil were recorded under electric field. It was found that the ER activity resulted from surface polarization processes due to presence of polar species (polyaniline and pyrolysed polyacrylonitrile) or bulk polarization related to mobile ions (polyphenylene). Polythiophene, despite its conjugation, showed only residual ER effect. The main conclusion is that many conducting (conjugated) polymers exhibit ER activity but the most characteristic and important feature of these materials – the conjugated system of multiple bonds – does not seem to be responsible for that. The electronic conductivity resulting from the conjugation contributes to higher currents which is unfavourable for technical applications. Conjugated polymers are ER active due to the enhanced mobility of ions within the bulk of particles dispersed in a liquid matrix and/or polar groups present on their surface.
THE EFFECT OF POLYANILINE CONTENT DEPOSITED ON SILICA GEL PARTICLES ON THE ELECTRORHEOLOGY OF SILICONE-OIL SUSPENSIONS
Authors: PAVLÍNEK V. , SÁHA P. , KITANO T. , HROMÁDKOVÁ J. , STEJSKAL J. , QUADRAT O.
Published: June 2005

Investigation of the electrorheological effect of silicone-oil suspensions of silica particles coated with polyaniline base in a DC electric field revealed that breaking stress, as a criterion the intensity of the electrorheological phenomenon, steeply increased at first with coating thickness. At relatively low polyaniline content (volume fraction ≈ 0.05), it has reached a value several times higher than that with suspension of pure silica. Then they became virtually constant or slightly increased. The frequency spectra of dielectric characteristics of these systems reflect high relaxation times. The results suggest that the interfacial polarization of particles is predominantly controlled by polarizability of their surface layer, and the influence of the thickness is of secondary importance.
TIO2BASED ELECTRORHEOLOGICAL FLUID WITH HIGH YIELD STRESS
Authors: SHEN RONG , WANG XUEZHAO , WEN WEIJIA , LU KUNQUAN
Published: June 2005

We have fabricated several TiO2based ER fluids with doping and without designed doping, which exhibit the high yield stress up to more than 100kPa. The titanium oxide nanoparticles were synthesized by using wet chemical method. The ER effect of those materials is dominated by the special additives, such as amide or its ramification, as well as the remained molecules or ions in the sample preparation. It is found that the yield stress is also strongly dependent on the viscosity of the oil. The prepared ER fluids possess other attractive characters, for instance the current density is low and against sedimentation.
HIGH PERFORMANCE CALCIUM TITANATE NANOPARTICLE ER FLUIDS
Authors: WANG XUEZHAO , SHEN RONG , WEN WEIJIA , LU KUNQUAN
Published: June 2005

A type of calcium titanate (CTO) nanoparticles was synthesized by means of wet chemical method [1] without coating on the particles. The CTO/silicone oil ER fluid exhibits excellent electrorheological properties: high shear stress (~50-100 kPa ) under dc electric field, a low current density (less than 2μA/cm2 at 5kV/mm), and long term stability against sedimentation. Although there are not special additives in the ER fluids, it is found from the chemical analysis that a trace of alkyl group, hydroxyl group, carbonyl group and some ions is remained in the particles which may dominate the ER response.
PREPARATION AND ABRASION PROPERTIES OF MAGNETO-RHEOLOGICAL FLUID OF DISPERSED SILICA-COATED IRON
Authors: SHIBAYAMA A. , OTOMO T. , AKAGAMI Y. , SHIMADA K. , FUJITA T.
Published: June 2005

In this study, a magneto-rheological fluid dispersed by silica-coated iron was developed and its properties such as fluid viscosity (shear stress or shear rate) and abrasion were investigated. The metallic iron coated by silica dispersed in magneto-rheological fluid was prepared by H 2 reducing of precipitated magnetite ( Fe 3 O 4). Then, the magneto-rheological fluid (MR fluid) for the seal was prepared with silica-coated iron or carbonyl iron (HQ type; diameter of 1.6-1.9 10-6m) and two solvent oils i.e. silicon oil (SH200cv, 10000cSt) and CVT oil (T-CVTF, automobile transmission oil). It was observed that the MR fluid viscosity of CVT oil with HQ particles is lower in every fluid condition. Furthermore, the surface roughness of polyvinyl plate after abrasion test for MR fluid with silica coated iron and CVT oil as solvent was higher compared to the other types of MR fluids. The results indicated that carbonyl iron (spherical particles) and silica-coated iron particles dispersed in silicon oil are feasible to be used where the low abrasion in mechanics is required.
ELECTRORHEOLOGICAL RESPONSE OF POLYANILINE-TIO2 COMPOSITE SUSPENSIONS
Authors: SUNG J. H. , LEE I. , CHOI H. J. , CHOI S. B.
Published: June 2005

As an organic/inorganic hybrid possessing advantages from the combination of their own unique properties, conducting polyaniline (PANI)-titanium dioxide ( TiO 2) hybrid particles were synthesized by an oxidation polymerization of aniline, and their ER characteristics were examined. Our aim was to study the ER behavior of highly potential ER-active particles using conducting polymer and TiO 2 nanoparticle with relatively high dielectric constant. In addition, we also investigated its ER behavior as a function of particle fraction of TiO 2 under an applied electric field. The result was interpreted in terms of the dielectric relaxation mismatch. The fast relaxation time of PANI/TiO 2 hybrid was considered to enhance electrostatic force over shear force under a hydrodynamic flow, showing its improved ER performance.
ELECTRORHEOLOGICAL EFFECT OF CONDUCTIVE POLYMERS DISPERSED IN LIQUID CRYSTALLINE MATRIX
Authors: CISZEWSKA MONIKA , PLOCHARSKI JANUSZ
Published: June 2005

Hybrid electrorheological fluids comprising powdered conjugated polymers dispersed in solutions of a liquid crystalline polymer were prepared and studied. FeCl 3 doped poly(p-phenylene) and pyrolised polyacrylonitrile were chosen as the dispersed phase and poly(n-hexyl isocyanate) dissolved in xylene was used as the active liquid matrix. All the component materials were extensively characterized by various methods. Flow curves of the hybrid ER fluids were recorded under electric field and compared with analogous curves obtained for dispersions of the powders in silicone oil and with homogeneous solutions of the LC polymer in xylene. A very significant enhancement of the ER effect in the studied hybrid fluids was observed.
MAGNETORHEOLOGICAL CHARACTERIZATION OF ORGANOCLAY ADDED CARBONYL-IRON SUSPENSIONS
Authors: LIM S. T. , CHO M. S. , CHOI H. J. , JHON M. S.
Published: June 2005

Carbonyl-iron (CI) based magnetorheological (MR) fluid containing submicron-sized additive particles was prepared. The flow behavior at steady and oscillatory shear modes was investigated by comparing flow properties of CI-mineral oil suspensions without an additive via precise control of magnetic field strength. To enhance the dispersion stability and to examine submicron-sized filler effect for the CI suspensions, organically modified montmorillonite (organoclay) was added to the CI suspensions. In addition, with the precision control of magnetic field strength, we examined the novel features of submicron-sized particle filled CI suspensions, especially under weak magnetic field strengths, in steady shear modes; a temporal decrease of steady shear viscosity in sweeping magnetic field strengths was observed.
SYNTHESIS AND ELECTRORHEOLOGY OF PHOSPHORIC ACID DOPED POLYANILINE SUSPENSIONS
Authors: HONG C. H. , CHOI H. J.
Published: June 2005

Semiconducting phosphoric acid doped polyaniline ( PANI-H 3 PO 4) particles were synthesized by chemical oxidation polymerization, and their chemical structure and particle size were examined via Fourier transform IR spectroscopy (FT-IR) and scanning electron microscopy (SEM), respectively. Electrorheological (ER) fluids were prepared by dispersing the synthesized PANI-H 3 PO 4 particles in kerosine, and their steady shear rheological properties under applied electric fields were investigated using a rotational rheometer with a high-voltage generator. The PANI-H 3 PO 4 synthesized in this study possesses a typical ER behavior: large increase of shear stress with applied electric field strengths.
MECHANISM OF THE GIANT ELECTRORHEOLOGICAL EFFECT
Authors: SHENG PING
Published: June 2005

We propose a model of surface saturation polarization as the mechanism for the giant electrorheological (GER) effect, recently discovered in suspensions of coated nanoparticles dispersed in silicone oil. On the basis of this model, the distinguishing features of the GER fluid, such as the extremely high value of the static yield stress (exceeding the theoretical upper-bound) and its linear field-dependence, can be explained quantitatively. The current-field relation and the particle size-scaling effect are also addressed. The agreement between theory and experiments is excellent. We give a brief discussion on the role of electrowetting effect in the formation of surface aligned dipole layer(s).
DYNAMIC ELECTRORHEOLOGICAL EFFECTS OF ROTATING PARTICLES: A BRIEF REVIEW
Authors: YU K. W. , GU G. Q. , HUANG J. P. , XIAO J. J.
Published: June 2005

Particle rotation leads to a steady-state which is different from the equilibrium state in the absence of rotational motion. The change of the polarization of the particle due to the rotational motion is called the dynamic electrorheological effect (DER). There are three cases to be considered: rotating particles in a dc field, particle rotation due to a rotating field and spontaneous rotation of particle in dc field (Quincke rotation). In the DER of rotating particles, the particle rotational motion generally reduces the interparticle force between the particles. The effect becomes pronounced when the frequency is on the order of the relaxation rate of the surface charges. In the electrorotation of particles, the mutual interaction between approaching particles will change the electrorotation spectrum significantly. The electrorotation spectrum depends strongly on the medium conductivity as well as the conductivity contrast between the particle and the medium. In the collective behaviors of Quincke rotors, the mutual interactions between the individual rotors lead to the assembly of chain-like structures which make an angle with the applied field. This has an implication of a new class of material.
VAN DER WAALS INTERACTION IN COLLOIDAL GIANT ELECTRORHEOLOGICAL SYSTEMS
Authors: SHEN M. , CAO J. G. , ZHU J. T. , XUE H. T. , ZHOU L. W. , XIONG X. M.
Published: June 2005

An alternative explanation of the giant eletrorheological (GER) effect is proposed using the van der Waals interaction which can lead to a yield stress of at least 50 kPa when the gap between two colloid spheres 60 nm in diameter is about 0.1 nm. This effect is in addition to the saturation dipole polarization in. When the electric field is removed, an elastic force would allow the colloid particle system to balance in a new position, which makes a larger gap than the one under the field, and the van der Waals force decreases dramatically. When the Laplace equation and the van der Waals interaction are considered, it is proposed that the gap between the colloidal ER particles would change with the external electric field to match the experimental result of the giant ER effect. An attempt is also shown to understand the size effect, base oil effect and tailing phenomenon of GER effect.
MEASUREMENT OF INTERACTIVE SURFACE FORCE OF SUSPENDED PARTICLES IN ER AND MR SUSPENSIONS UNDER ELECTRIC AND MAGNETIC FIELD
Authors: SHIBAYAMA A. , OTOMO T. , SHIMADA K. , FUJITA T.
Published: June 2005

Interactive surface force between each particle in suspension is very important to explain the dispersion and flocculation phenomena in fluid. The new equipment has been developed to measure the interactive surface force of particles, which was calculated by using Derjaguin's formula, in Electro-Rheological (ER) Fluid and Magneto-Rheological (MR) Suspensions/fluids under electric and magnetic fields, respectively. Firstly, the interactive force of particles in ER fluid dispersed by melamine particles under electric fields was measured. Secondly, the interactive force of particles in MR suspensions dispersed by carbonyl iron particles under magnetic field was investigated. Considering the measurement of interactive surface force of ER and MR fluids, they have a original characteristic frequency due to the attractive and repulsive force of particles interactions initiated by the electric, magnetic and compressive force. Moreover, clusters formed according to the size of particles, particles movement model and formation are estimated by the characteristic frequency of ER fluid and MR suspensions under various electrical and magnetic fields. It indicates that these estimation models might be lead to the interaction kinetics of suspended particles in ER/MR under electrical and magnetic fields.
EFFECTS OF PREPARATION PROCEDURE AND ELECTRIC FIELD FREQUENCY ON THE DIELECTRIC CONSTANTS AND ELECTRORHEOLOGY OF A ZEOLITE/SILICONE OIL SUSPENSION
Authors: McNEISH D. , JUNG K. , BALIK C. M. , CONRAD H.
Published: June 2005

Determined were the effects of preparation procedure and electric field frequency f = dc to 105 Hz on the dielectric constants and ER response (shear rate [Formula: see text]) of a suspension in silicone oil of 23 wt.% zeolite particles originally containing 19 wt.% H 2 O . Heating the oil and the zeolite particles at 110°C both prior to, and following, mixing decreased the conductivity of the suspension more than simply heating the suspension following mixing. The double heating procedure reduced the complex dielectric constant [Formula: see text] of the particles and the complex mismatch parameter β*. The ER shear stress τ E was proportional to [Formula: see text] for the single heating and [Formula: see text] for the double heating, where [Formula: see text] is the complex dielectric constant of the silicone oil. The lower exponent corresponds to a higher water content and in turn higher conductivity of the suspension. Erratic ER response occurred for f =10 Hz in tests with [Formula: see text], but not in tests with [Formula: see text].
LINEAR VISCOELASTICITY OF MR FLUIDS: DEPENDENCE ON MAGNETIC FIELDS
Authors: LI W. H. , ZHANG P. Q. , GONG X. L. , KOSASIH P. B.
Published: June 2005

The paper presents investigation of dynamic properties of MR fluids by using a rheometer with parallel-plate geometry. The sample is reduced iron powder based MR suspensions. Linear viscoelastic properties of such sample, which can be variably controlled using a magnetic field, are obtained and summarized based on oscillatory tests. Four field-induced regimes, I, II, III, and IV, are found in the system, which are defined by three critical field strengths: BC1< BC2< BC3. MR fluids in regime I through IV experience four typical structural convolutions: coexisting of particles and random chains; coexisting of chains and random clusters; coexisting of clusters and chains; stable clusters. Such results are in good accord with experimental results achieved by Liu's group using light scattering techniques.
MAGNETIC BODY FORCE
Authors: BAKUZIS A. F. , CHEN KEZHENG , LUO WEILI , ZHUANG HONGZHANG
Published: June 2005

We have studied magnetic force on sperical magnetic fluid samples with a wide range of concentrations by pendulum method. The results demonstrate good agreement with Kelvin body force and show that other force expressions clearly deviate from experimental data for large sussceptibility values.
ELECTRIC FIELD-INDUCED INTERACTION FORCE BETWEEN TWO SPHERES
Authors: WANG ZHIYONG , SHEN RONG , WANG XUEZHAO , SUN GANG , LU KUNQUAN , WEN WEIJIA
Published: June 2005

An apparatus is developed to study field-induced forces between two spheres. The mutual forces of a couple of identical spheres made of different materials in various media have been measured precisely as the function of inter-spherical spacing, field strength and field frequency. The respective dependences of the forces on inter-spherical spacing, field strength, field frequency and sphere size are obtained. By comparing the measured results with available theoretical calculations we conclude that a further improvement on the theoretical model should be carried out for explaining the most experimental results when the particle nearly contact.
INTERACTIONS BETWEEN TWO ROTATING POLARIZED SPHERES
Authors: TAO R. , LAN Y. C.
Published: June 2005

Precise measurement of the attracting force between two spheres inside an electric field indicates that the rotation of one sphere along the axis perpendicular to the electric field reduces the attracting force between them. This reduction becomes smaller as the distance between the two spheres increases. In the limit of infinite rotational speed, the attracting force seems to tend to a non-zero constant.
DYNAMIC ANALYSIS OF ROTATING ELECTRORHEOLOGICAL COMPOSITE BEAMS
Authors: WEI KEXIANG , MENG GUANG , LU HONGQUAN , ZHU SHISHA
Published: June 2005

The modeling and vibration properties of rotating electrorheological (ER) sandwich beams are discussed. The proposed beam is composed of three layers with ER fluids sandwiched between two elastic layers. Based on the Hamilton's principle and finite element method (FEM), the equations of motion of ER beam are derived. The effects of different electric fields, rotating speed and thickness ration on the resonant frequencies and modal loss factors are presented. The results of numerical simulation show that the model loss factor of rotating ER beam can be substantially increased when applied an electric field. The ER materials have a significant effect on the vibration suppression of rotating composite beam.
DIFFUSING WAVE SPECTROSCOPY STUDY OF TAILING PHENOMENON OF COLLOIDAL ELECTRORHEOLOGY FLUIDS
Authors: MA Y. H. , GUO L. M. , ZHONG L. , ZHOU L. W.
Published: June 2005

Back scattering of diffusing wave spectroscopy (DWS) method is employed to measure the mean square displacements of the colloidal particles in electrorheological fluid systems right after an electric field is applied and removed. An electrorheological fluid consisting of colloidal particles 30-40 nm in size shows a tailing phenomenon, namely the clusters of the colloidal ER particles do not return to their original state of Brownian motion as soon as the electric filed is removed. The DWS results of above ER fluid shows that the mean square displacement remains small and changes slowly with time right after the electric field is removed. The Van der Waals attractive force between colloidal particles is used to explain this tailing phenomenon.
OSCILLATORY SQUEEZE FLOW OF ELECTRORHEOLOGICAL FLUID WITH TRANSITIONAL ELECTRIC FIELD
Authors: PENG JIE , ZHU KE-QIN
Published: June 2005

The oscillatory squeeze flow of electrorheological (ER) fluid between two parallel discal electrode with transitional electric field is studied numerically in this paper. The ER fluid is modeled as Bingham-like fluid with the continuous modification model proposed by Papanastasiou. The numerical solutions based on the Navier-Stokes equations are presented by using the finite volume methods on the deforming grid. The force transmitted across the fluid under dc and ac electric fields are calculated. The effects of the electric field frequency and the phase difference between the ac electric field and mechanical oscillation are studied. The magnitude and the shape of the transmitted forces is shown to be not only a function of the applied voltage and the mechanical frequency but also the phase difference.
TOTAL FORCE CALCULATION METHOD FOR ER EFFECT OF LIQUID CRYSTALLINE POLYMER ON ONE-SIDED PATTERNED ELECTRODE SYSTEM
Authors: KIKUCHI TAKEHITO , FURUSHO JUNJI , INOUE AKIO
Published: June 2005

In most studies, a bilateral electrode system in which an electrorheological fluid (ERF) is filled between a pair of electrodes has been used for application of the ERF. Some troubles exist in this configuration of the electrodes, for example a short-circuit. We have, therefore, proposed "one-sided pattern electrodes", or "OSPE" that are arranged on the only one-side surface. In order to use efficiently them for any controllable systems, characteristics of the ERF on OSPE should be cleared and a design procedure for it will be needed. In this paper, we proposed a total force calculation method for the one-sided patterned electrode (OSPE) system in which a liquid crystalline polymer (type-A LCP) was used. Experimental results and simulation results are compared on a force transmission system using the OSPE. In the proposed simulation method, we improved a mathematical model of the characteristics of the type-A LCP, "two phased viscosity model". By using this model, we improved the accuracy of a simulation result. These simulation methods will enables to design an optimal electrode pattern.
THE CONCOMITANT-EFFECT OF ELECTRORHEOLOGICAL FLUID IN A CONTROL FLOW FIELD
Authors: ZHU Shi-sha , FUJITA Toyohisa , WANG Qi-xin , LIU Kejun , DODBIBA Gjergj
Published: June 2005

The description of ER response in a flow field is a key issue in researching control technology of ER fluid. In this paper, an experimental work on controlling flow field in fluid power transmission has been carried out. The results of research show that the control flow field differs from the rotary shearing flow field in an experimental instrument. Besides the ER effect there is a concomitant-effect of ER response called "capture effect" in the field, which is unbeneficial to the control on fluid power transmission.
STUDY OF THE EFFECT OF MAGNETIC FIELD ON MR SUSPENSIONS BASED ON JET IMAGES
Authors: FILHO I. LATERZA , SABADINI EDVALDO , ALKSCHBIRS M. I. , VOLPE P. L. O. , BOMBARD ANTONIO J. F.
Published: June 2005

Suspensions of carbonyl iron powder in oil (CIP/O) have a very promising application on controlled fluids processes, as a very high local viscosity can be produced in the region in which the magnetic field is applied, allowing some control of the flow. In experiments performed in tube viscometers the flow can be completely stopped in some circumstances, such as specific pressure, magnetic field strength and particles concentration. This work presents our initial results of the jet morphology produced at the tip of the tube of a CIP/O, in terms of the applied pressure or of the applied magnetic field. A 3-CCD camera positioned in front of the jet collected "frozen" pictures of the jets produced in different conditions. Morphologic parameters of the jet such as the angle of the cone and the amplitude of the jet oscillation can be measured. Thus, the effect of the magnetic field on the fluid can be visualized and parameterized. It was observed that the perturbation due to the application of the magnetic field on the tip of the tube causes large changes on the jet oscillation. The amplitudes of the oscillations are very sensitive to the parameters described above.
ANALYSIS OF MR FLUIDS FLOW IN A RECTANGULAR CHANNEL CONSIDERING MAGNETO-RHEOLOGICAL PROPERTIES
Authors: NISHIYAMA HIDEYA , WATANABE MASAHIRO , YAMAGUCHI HIROSHI
Published: June 2005

Governing equations of MR fluids using improved Bingham model and considering anisotropic rheological properties in the applied magnetic field are proposed to analyze MR fluids flow in a rectangular channel. It is found that the flow rate decreases linearly with magnetic field intensity, which is remarkable for large anisotropic parameter of shear stress and small aspect ratio of channel cross section in the strong magnetic field intensity and small pressure gradient. The pressure gradient becomes steep in the applied magnetic field region, which results from large viscous drag force caused by increasing yield stress. The pressure distribution shows the same tendency as experimental result.
VISCOSITY REDUCTION IN LIQUID SUSPENSIONS BY ELECTRIC OR MAGNETIC FIELDS
Authors: TAO R. , XU X.
Published: June 2005

Reducing the viscosity of liquid suspensions is of great importance in science and engineering. We present a theory and experiments that a suitable electric or magnetic field pulse can effectively reduce the viscosity for several hours with no appreciable change of temperature. Positive experimental results with magnetorheological fluids and crude oil suggest a broad range of practical applications.
IMPORTANCE OF CONTROLLING INTERPARTICLE GAPS FOR NOVEL MATERIAL PROPERTIES
Authors: METAYER C. , COQUELLE E. , STERLIGOV V. A. , MEUNIER A. , BOSSIS G. , PERSELLO J.
Published: June 2005

Measurement of average interparticle gap in chains of colloidal particles is realized by means of light scattering in silica suspensions or dynamic mechanical analysis in MR elastomers. For a silica volume fraction of 10% we find that the mean distance between particles inside chains drop off sharply with the increase of field; this behavior is attributed to the presence of a long range ionic repulsive force. We show that this experiment allows to obtain information about interparticle forces between colloidal particles. On the other hand the transmitted light is very sensitive to the size of the particles in the chain and to the gap between particles. In an other domain, namely elastomers containing chains of magnetic particles, the magnetostriction is also found to be determined by the interparticle gap.
FRICTION FACTOR OF MAGNETO-RHEOLOGICAL FLUID FLOW IN GROOVED CHANNELS
Authors: GORDANINEJAD F. , KAVLICOGLU B. M. , WANG X.
Published: June 2005

The focus of this work is to study surface effects on the friction factor a magneto-rheological (MR) fluid flowing through a grooved channel under various magnetic fields and volumetric flow rates. Based on the experimental data, a relation is developed for the friction factor of MR fluid in channel flow in terms of Mason number evaluated at the surface, and the depth of the grooves. Using this relation, the pressure loss of a MR fluid flowing through a channel with grooved walls can be determined without implementing a constitutive model for MR fluids or utilizing the concept of shear yield stress. Several grooves with different configurations in channel walls have been considered. From the experimental results it has been demonstrated that under an applied magnetic field, the grooved surface would increase the friction factor of MR fluid flow significantly when comparing to the surface without grooving. The depth of grooves plays an important role in this increment.
STUDY OF MECHANICAL BEHAVIOR AND MICROSTRUCTURE OF MAGNETORHEOLOGICAL ELASTOMERS
Authors: GONG X. L. , ZHANG X. Z. , ZHANG P. Q.
Published: June 2005

Magnetorheological elastomers' mechanical property is greatly influenced by the microstructure of magnetizable particles embedded in the rubber matrix. When synthesizing magnetorheological elastomers, usually the mixture is cured in the presence of a magnetic field and particles are arranged in chainlike or columnar structure after the crosslink, in order to get remarkable effect controlled by the magnetic field. However curing under the magnetic field will face some problems, e.g. the preparation will become not convenient.

In this paper magnetorheological elastomers are prepared in various volume fractions in the absence of a magnetic field. Their dynamic viscoelastic properties are tested by a system designed by ourselves. Their microstructures are observed by scan electronic microscope. Finally the inherent relation is revealed between the magnetoviscoelasticity and the distribution of particles in the matrix as well as the components of the mixture and the chemical technique. A kind of typical microstructure is found to be relative to the magnetoviscoelasticity of magnetorheological elastomers prepared in the absence of a magnetic field. This study also provides a guide when designing and preparing this kind of smart materials.
CHARACTERIZING THE EFFECT OF TEMPERATURE AND MAGNETIC FIELD STRENGTHS ON THE COMPLEX SHEAR MODULUS PROPERTIES OF MAGNETORHEOLOGICAL (MR) FLUIDS
Authors: CHOOI W. W. , OYADIJI S. O.
Published: June 2005

When a magnetic field is applied across MR fluids, a yield stress is developed, and their rheological properties can then be categorized into two distinct regimes; pre-yield and post-yield. This paper concerns the viscoelastic behaviour of MR fluids in the pre-yield region. Oscillatory tests were carried out to determine the complex shear modulus properties of MR fluids between the temperature range of -20°C and +50°C. The test results show that the storage modulus and loss modulus increased in value as the excitation frequency was increased from 5Hz to 50Hz. The complex modulus was also found to be influenced by changes in temperature; the higher the temperature, the lower the complex modulus. This is consistent with the behaviour of viscoelastic polymers. The sets of temperature-dependent and frequency-dependent data were subsequently condensed using the method of reduced variables into master curves of complex modulus which effectively extended the frequency coverage of the data at the reference temperature.
PREISACH MODEL OF ER FLUIDS CONSIDERING TEMPERATURE VARIATIONS
Authors: HAN Y. M. , CHOI S. B. , CHOI H. J.
Published: June 2005

This paper presents a new approach for hysteresis modeling of an electro-rheological (ER) fluid. The Preisach model is adopted to describe change of an ER fluid hysteresis with temperature, and its applicability is experimentally proved by examining two significant properties under two dominant temperature conditions. As a first step, the polymethylaniline (PMA)-based ER fluid is made by dispersing the chemically synthesized PMA particles into non-conducting oil. Then, using the Couette type electroviscometer, multiple first order descending (FOD) curves are constructed to consider temperature variations in the model. Subsequently, a nonlinear hysteresis model of the ER fluid is formulated between input (electric field) and output (yield stress). A compensation strategy is also formulated in a discrete manner through the Preisach model inversion to attain desired shear stress of the ER fluid. In order to demonstrate the effectiveness of the identified hysteresis model and the tracking performance of the control strategy, the field-dependent hysteresis loop and tracking error responses are experimentally evaluated in time domain and compared with responses obtained from Bingham model.
EXPERIMENTAL STUDY OF MR SUSPENSIONS OF CARBONYL IRON POWDERS WITH DIFFERENT PARTICLE SIZES
Authors: BOMBARD A. J. F. , ALCÂNTARA M. R. , KNOBEL M. , VOLPE P. L. O.
Published: June 2005

Magnetorheological suspensions (MRS) based on mixtures of two commercial carbonyl iron powders (BASF grades CL and SU) as magnetic phase and hydrocarbon oil as liquid phase were prepared. CL and SU are both soft magnetic powders, but CL is a coarse powder, while SU is a fine one. The total mass fraction of iron was 80% w/w each formulation. Hydrophilic fumed silica (5% w/w of Aerosil® 200) was used to reduce the settling. The mixing ratios were: CL 0%, CL 20%, CL 40%, CL 60%, CL 80% and CL 100%. A MRS, the mixture CL 80%, showed considerable reduction of the plastic viscosity without field, in the range of 100 – 500 s-1, when compared to the MRS with just one powder. The yield stress values under applied field H ~ 340 kA/m were: 18.1 kPa for the MRS CL 0%, 18.3 kPa for the MRS's CL 20% and CL 40%, 20.0 kPa for the MRS CL 60%, 22.3 kPa for the MRS CL 80% and 23.3 kPa for the MRS CL 100%, respectively. For comparison, a sample of commercial MRF-132LD (Lord Corp.) in the same conditions showed yield value of 21.2 ± 0.6 kPa. On the other hand, another MRS, CL 60%, showed an increment of ~ 33% on the normal force, with relation to the MRS prepared with just CL or just SU powders, above 150 kA/m. Therefore, mixing carbonyl iron powders with different particle sizes can improve the performance of MRS, decreasing the 'off' plastic viscosity, and increasing the MR effect.