Magnetics Research Papers - Academia.edu (original) (raw)

A remote magnetic navigation system (MNS) is available and has been used with a 4-mm-tip magnetic catheter for radiofrequency (RF) ablation of some supraventricular and ventricular arrhythmias; however, it has not been evaluated for the ablation of cavotricuspid isthmus-dependent right atrial flutter (AFL). The present study evaluates the feasibility and efficiency of this system and the newly available 8-mm-tip magnetic catheter to perform RF ablation in patients with AFL. Twenty-six consecutive patients (23 men, mean age 64.6 +/- 9.6 years) underwent RF ablation using a remote MNS. RF ablation was performed with an 8-mm-tip magnetic catheter (70 degrees C, maximum power 70 W, 90 seconds). The endpoint of ablation was complete bidirectional isthmus block. To assess a possible learning curve, procedural data were compared between the first 14 (group 1) and the rest (group 2) of the patients. The initial rhythm during ablation was AFL in 20 (19 counterclockwise and 1 clockwise) and s...

- by
- •
- Biomedical Engineering, Treatment Outcome, Feasibility Studies, Clinical Sciences

A recent fMRI study showed that dorsolateral prefrontal cortex (DLPFC) exerts an inhibitory control on pain pathways in humans. We investigated whether high-frequency rTMS over left DLPFC could ameliorate chronic migraine. Treatment consisted of 12 rTMS sessions, delivered in alternate days over left DLPFC. Sham rTMS was used as placebo. Eleven patients were randomly assigned to the rTMS (n=6) or to the placebo (n=5) treatment. Measures of attack frequency, headache index, number of abortive medications (outcome measures) were recorded in the month before, during and in the month after treatment. Subjects treated by rTMS showed a significant reduction of the outcome measures during and in the month after the treatment as compared to the month before treatment. No significant differences in the outcome measures were observed in the placebo group. High-frequency rTMS over left DLPFC was able to ameliorate chronic migraine. This is in agreement with the suggested role of DLPFC in pain control.

- by Antonio Palermo
- •
- Medicine, High Frequency, Chronic Disease, Migraine
- by Fernando Romeiro
- •
- Drug delivery, Pharmaceutical, Solubility, Magnetics

CaP ceramic has been widely used as coating on metals in orthopedics and oral dentistry. Variations in CaP composition can lead to different dissolution/precipitation behavior and may also affect the bone response. In the present study calcium pyrophosphate and hydroxylapatite coatings were successfully prepared by RF magnetron sputtering deposition. The phase composition, morphological properties, and the dissolution in SBF were characterized by using XRD, FTIR, EDS, SEM, and spectrophotometry. The results showed that all the sputtered coatings were amorphous and changed into a crystal structure after IR-radiation. The temperature for the crystallization of the amor-phous coatings is lower for the hydroxylapatite coating (550°C), compared to the calcium pyrophosphate coating (650°C). All sputtered amorphous coatings were instable in SBF and dissolved partially within 4 wks of incubation. The heat-treated coatings appeared to be stable after incubation. These results showed that magnetron sputtering of calcium pyrophosphate coating is a promising method for forming a biocompatible ceramic coating.

- by Joop Wolke
- •
- Engineering, Scanning Electron Microscopy, Biological Sciences, Crystal structure

We describe herein the case of a 3-year-old child in whom a jejunoileal fistula was caused by the ingestion of magnets. This case report demonstrates that if more than one magnet is found as a foreign body in the intestine, they should not be left untreated even if there are no sharp edges and, it seems they could be evacuated spontaneously. This recommendation is made because the magnets will attract each other and hold the intestinal walls between them, causing necrosis and resulting in intestinal perforation or a fistula.

- by Hisashi Urata
- •
- Case Report, Jejunum, Clinical Sciences, Magnetics

Objective: Biodegradable polycaprolactone/starch composites can be used for bone tissue engineering applications. The effect of the ratio of components on composite properties is of tremendous importance. Methods: Polycaprolactone/starch composite of 80/20 and 70/30 ratios were fabricated by dissolving them in chloroform followed by evaporation of the solvent. Results: The composites were characterized by fourier transform infrared spectroscopy. Their bioactivity was evaluated by studying the apatite formation ability after immersing the specimens in simulated body fluid. The results of compressive test on samples showed that the composite's modulus and strength approximated that of human trabecular bone. Mass loss in distilled water and starch degradation rate in PBS was evaluated, which showed that the starch ratio was effective in composite degradation. MTT analysis and alkaline phosphatase levels showed that this composite had no toxicity and could increase G-299 cell line osteoblastic activities. Conclusion: The increase in cellular osteoblastic activities and the ability for apatite formation on the composite surface, in addition to the polycaprolactone/starch samples' mechanical properties shows their capability to be used as substitutes for bone. Because this composite degradation rate is controlled by changing the starch ratio, it has the potential for use in bone tissue engineering applications. Samples that have a 70/30 ratio are considered optimal due to their enhanced cellular response and better mechanical properties.

- by Mehran Solati-Hashjin
- •
- Engineering, Materials Engineering, Chemical Engineering, Thermodynamics

Dedicated and specialized radiofrequency coils are critical for high quality musculoskeletal magnetic resonance imaging (MRI). Dedicated coils improve the signal to noise ratio, allowing for faster or higher resolution examinations. Transmit-receive coils can reduce heating at high field strength. Finally, novel radiofrequency coils can be used for assessment of tissue biochemistry, as seen with sodium MRI.

- by Neal Bangerter
- •
- Magnetic Resonance Imaging, Molecular Imaging, Magnetics, Image Enhancement

Objective: To compare the electrophysiological excitability characteristics of the facial nucleus and related structures in hemifacial spasm (HFS), post-facial palsy synkinesis (PFPS) and facial myokymia (FM). Methods: Facial F-waves, blink reflex recoveries and magnetically elicited silent periods (SP) were prospectively studied in 17 HFS, 17 PFPS, 8 FM cases and in 13 controls. Earlier unpublished observations on abnormal impulse transmission in 36 HFS and 29 PFPS cases were also included. Results: Enhanced F-waves were recorded on the symptomatic side in PFPS and HFS cases with a tendency to be more pronounced in PFPS. HFS and PFPS groups both showed an earlier blink reflex recovery, more prominent in PFPS patients, when stimulated and/or recorded on the symptomatic side. Unelicitable SPs were encountered after 24/39 stimulations in 5 patients with PFPS and rarely in HFS cases. Duration of elicitable SPs did not change remarkably. FM group had similar characteristics as normal controls in the 3 electrophysiological tests. Latencies of the lateral and synkinetic spread responses were significantly prolonged in the earlier PFPS group as compared to HFS. In twopoint stimulation, both groups showed a greater latency shift in late responses, again more pronounced in PFPS. Conclusions: PFPS and HFS cases had similar enhanced excitability patterns at the facial nucleus and related brain-stem structures, more marked on the symptomatic side and more obvious in the PFPS group. Findings elicited in the FM group were thought to be caused by asynchronous hyperactivity of facial motoneurons. Significance: In this comparative electrophysiological study, similar excitability patterns were found in HFS and PFPS groups, albeit with different intensities.

- by A. Öge
- •
- Engineering, Facial Paralysis, Adolescent, Electromyography
- by Susan Frost
- •
- Analytical Chemistry, Adipose tissue, Mice, Cell Fractionation
- by Carsten Enevoldsen
- •
- Cattle, Magnetics, Veterinary Sciences, Wounds and Injuries
- by Dominik Heyers and +1
- •
- Psychology, Cognitive Science, Animal Behavior, Navigation

In this study, we present evidence for the perception of diVerent magnetic Weld parameters in a facultative anadromous Wsh species of the family Salmonidae. Magnetic Weld perception of the rainbow trout, Oncorhynchus mykiss, was demonstrated with a heartbeat conditioning test. The electrocardiogram was measured with subcutaneously inserted silver wire electrodes in freely swimming Wsh. We demonstrate a conditioned response (i.e. a signiWcant longer interval between two heartbeats) to an intensity/inclination shift for three adult and two juvenile rainbow trouts. Moreover, a conditioned response to a 90° direction shift was demonstrated for three adult and two juvenile trouts. These Wndings support the hypothesis that the rainbow trout is able to perceive diVerent magnetic Weld parameters. Furthermore, the study demonstrates magnetosensation in diVerent developmental stages in the rainbow trout, i.e. juvenile and adult Wsh.

- by Klaus-peter Hoffmann
- •
- Perception, Animal Behavior, Magnetic field, Electrocardiography

communities, values of b i,j were selected from uniform distributions between 0 and 20.1 (plant-plant competition), 20.3 (herbivores ! plants; that is, the effect of herbivores on plants), 0.1 (plants ! herbivores), 20.1 (predators ! herbivores), and 0.05 (herbivores ! predators). Intraspecific interactions were selected at random between 20.1 and 20.2 for plants, and set to 20.2 for herbivores and predators. For competitive communities, interspecific values of b i,j were selected uniformly between 0 and 20.1, and intraspecific values between 20.06 and 20.16. For the arbitrary topology, the probability of any pair of species interacting was 0.5, and of the interacting pairs of species 45% were competitors, 45% were prey and predators, and 10% were mutualists. The magnitudes of interspecific values of b i,j were selected uniformly between 0 and 0.1, with sign dictated by type of interaction, and intraspecific values were selected between 20.06 and 20.16.

- by Wolfgang Wiltschko
- •
- Geography, Multidisciplinary, Nature, Magnetic field

The nanoparticles are superparamagnetic at room temperature and display a blocking temperature of 17.6 K. Their anisotropy (2.7 10 5 J m À3) is determined to be more than two orders of magnitude higher than that of the bulk NiFe alloy (10 3 J m À3) and is close to that determined for Fe nanoparticles of the same size. Still, they display a magnetization of (1.69 AE 0.05) m B per metallic atom, identical to that of the bulk NiFe alloy. Combining the results from X-ray absorption and Mçssbauer studies, we evidence a progressive enrichment in iron atoms from the core to the surface of the nanoparticles. These results are discussed in relation to both size and chemical effects. They show the main role played by the enriched Fe surface on the magnetic properties and address the feasibility of soft magnetic materials at the nanoscale.

- by Pierre Lecante
- •
- Crystallization, Nanoparticles, Nanotechnology, Multidisciplinary

This paper illustrates the use of the impedance method to calculate the electric fields and current densities induced in millimetre resolution anatomic models of the human body, namely an adult and 10-and 5-year-old children, for exposure to nonuniform magnetic fields typical of two assumed but representative electronic article surveillance (EAS) devices at 1 and 30 kHz, respectively. The devices assumed for the calculations are a solenoid type magnetic deactivator used at store checkouts and a pass-by panel-type EAS system consisting of two overlapping rectangular current-carrying coils used at entry and exit from a store. The impedance method code is modified to obtain induced current densities averaged over a cross section of 1 cm 2 perpendicular to the direction of induced currents. This is done to compare the peak current densities with the limits or the basic restrictions given in the ICNIRP safety guidelines. Because of the stronger magnetic fields at lower heights for both the assumed devices, the peak 1 cm 2 area-averaged current densities for the CNS tissues such as the brain and the spinal cord are increasingly larger for smaller models and are the highest for the model of the 5-year-old child. For both the EAS devices, the maximum 1 cm 2 area-averaged current densities for the brain of the model of the adult are lower than the ICNIRP safety guideline, but may approach or exceed the ICNIRP basic restrictions for models of 10-and 5-year-old children if sufficiently strong magnetic fields are used.

- by Om Gandhi
- •
- Biophysics, Biomedical Engineering, Child, Radiation Effects

Oral administration is the most convenient route for drug therapy. The knowledge of the gastrointestinal transit and specific site for drug delivery is a prerequisite for development of dosage forms. The aim of this work was to demonstrate that is possible to monitor the disintegration process of film-coated magnetic tablets by multi-sensor alternate current Biosusceptometry (ACB) in vivo and in vitro. This method is based on the recording of signals produced by the magnetic tablet using a seven sensors array and signal-processing techniques. The disintegration was confirmed by signals analysis in healthy human volunteers' measurements and in vitro experiments. Results showed that ACB is efficient to characterize the disintegration of dosage forms in the stomach, being a research tool for the development of new pharmaceutical dosage forms. q

- by Jose Miranda
- •
- Signal Processing, Drug delivery, Signal Analysis, Drug Delivery Systems
- by Bert Kohlmann
- •
- Management, Engineering, Ecological Engineering, Bioinformatics

Sixteen multiparous nonpregnant lactating Holstein cows (each weighing 662 { 65 kg in 150.4 { 40 day of lactation) were confined to wooden metabolic cages with 12:12 h light:dark cycle during the experiment. The cows were divided into two sequences of eight cows each and exposed to electric and magnetic fields (EMF) in an exposure chamber. This chamber produced a vertical electric field of 10 kV/m and a uniform horizontal magnetic field of 30 mT at 60 Hz. One sequence was exposed for three estrous cycles of 24 to 27 days. During the first estrous cycle, the electric and magnetic fields were off; during the second estrous cycle, they were on; and during the third estrous cycle, they were off. The second sequence was also exposed for three 24 to 26 days estrous cycles, but the exposure to the fields was reversed (first estrous cycle, on; second estrous cycle, off; third estrous cycle, on). The length of each exposure period (21 to 27 days) varied according to the estrous cycle length. No differences were detected in plasma progesterone concentrations and area under the progesterone curve during estrous cycles between EMF nonexposed and exposed periods (2.28 { 0.17 and 2.25 { 0.17; and 24.5 { 1.9 vs. 26.4 { 1.9 ng/ml, respectively). However, estrous cycle length, determined by the presence of a functional corpus luteum detected by concentrations of progesterone equal to or more than 1 ng/ml plasma, was shorter in nonexposed cows than when they were exposed to EMF (22.0 { 0.9 vs. 25.3 { 1.4 days).

- by Duc Hai Nguyen
- •
- Engineering, Bioelectromagnetics, Electricity, Biological Sciences

- by Duc Hai Nguyen
- •
- Engineering, Bioelectromagnetics, Electricity, Biological Sciences

Isolation of mitochondria by current methods relies mainly on their physicochemical properties. Here we describe an alternative approach to obtain functional mitochondria from human cells in a fast, reproducible, and standardized procedure. The new approach is based on superparamagnetic microbeads conjugated to anti-TOM22 antibody. The bead conjugates label the cytoplasmic part of the human mitochondrial membrane protein TOM22 and, thus, allow for a gentle isolation of mitochondria in a high gradient magnetic field. By comparing the MACS (magnetic cell separation) approach with mitochondria isolation methods using differential centrifugation and ultracentrifugation we demonstrate that the MACS approach provides the highest yield of isolated mitochondria. The quality, enrichment, and purity of mitochondria isolated with this protocol are comparable to mitochondria obtained using the ultracentrifuge method, and a typical separation procedure takes only approximately 1 to 2 h from initial cell homogenization. Mitochondria isolated with the new approach are sufficient for protein import, blue native gel electrophoresis, and other mitochondrial assays.

- by Rudolf Wiesner and +1
- •
- Analytical Chemistry, Flow Cytometry, Membrane Proteins, Mitochondria

To test whether the mandible opens more during deep sleep and whether the mandibular position is aected by body position during sleep, the vertical mandibular position was recorded intraorally using a magnet sensor at the same time as a standard sleep study in seven normal healthy male adults. Measurements were recorded during the period before sleep onset (WAKE) and during sleep. Two-way ANOVA showed that vertical mandibular position was signi®cantly aected by sleep stage but not by body position (supine vs lateral recumbent). The proportion of time during which the mandible was in a near-closed position (0±2.5 mm) signi®cantly and progressively decreased, and signi®cantly more time was spent at wider gapes (2.5±5 mm) as non-rapid-eye-movement (NREM) sleep deepened. In REM sleep, the proportion of time during which the mandible was at wider gapes was signi®cantly greater than in WAKE and stage 1 (but not later stages) of NREM sleep. It was concluded that mandibular posture during sleep in healthy adults is signi®cantly in¯uenced by sleep stage but not by body position. Mandibular opening progressively increases with the depth of NREM sleep stage, and the mandible is more open in REM sleep than in light NREM sleep. #

- by Alan Lowe
- •
- Zoology, Dentistry, Biomedical Engineering, Mandible

Using the eye-coil/magnetic field method, we measured horizontal and vertical movements of both eyes in four patients with monocular loss of vision while they attempted steady, binocular fixation of a visual target. We also measured gaze stability in two normal subjects while they fixed upon a target monocularly, and in one patient with congenital, bilateral blindness. In the patients with monocular visual loss, gaze instability was greater in the blind eye, both vertically and horizontally, compared either with their seeing eye or with nonviewing eyes of control subjects. Gaze instability due to monocular blindness resulted from: (1) low-frequency, low-amplitude, bidirectional drifts that were more prominent vertically; and (2) unidirectional drifts, with nystagmus, that were more prominent in the horizontal plane. Gaze-evoked nystagmus, however, was not a feature of monocular blindness. Thus, the gaze instability of monocular blindness may reflect disruption of: (1) a monocular vi...

- by Douglas Lanska
- •
- Blindness, Binocular vision, Biological Sciences, Magnetics

The main parameters of magnetoelastic resonators in the detection of chemical (i.e., salts, gases, etc.) or biological (i.e., bacteria, phages, etc.) agents are the sensitivity S (or external agent change magnitude per Hz change in the resonance frequency) and the quality factor Q of the resonance. We present an extensive study on the experimental determination of the Q factor in such magnetoelastic resonant platforms, using three different strategies: (a) analyzing the real and imaginary components of the susceptibility at resonance; (b) numerical fitting of the modulus of the susceptibility; (c) using an exact mathematical expression for the real part of the susceptibility. Q values obtained by the three methods are analyzed and discussed, aiming to establish the most adequate one to accurately determine the quality factor of the magnetoelastic resonance.

- by Virginia Muto
- •
- Analytical Chemistry, Bacteriophages, Elasticity, Sensors

Large unilamellar magnetoliposomes (MLs) with encapsulated doxorubicin (DOX) (anticancer drug) were prepared by reverse-phase evaporation. They were exposed to an alternating magnetic field with a frequency of 3.5 MHz and an induction of 1.5 mT produced in threeturn pancake coil. The results showed that magnetoliposomes could be specifically heated to 42°C (phase transition temperature of a used lipid) in a few minutes and during this, the encapsulated doxorubicin is massively released.

- by Cestmir Altaner
- •
- Bioelectrochemistry, Magnetic field, Cancer Therapy, Liposomes

Magnetic separation combined with adsorption by activated carbon has been found to be a useful method for removing pollutants. In this paper, the use of palm shell as a source of activated carbon for the removal and recovery of oil from palm oil mill effluent (POME) is studied. In the first part of the study, the properties of samples of activated carbon prepared from palm shell under a variety of different conditions were characterized for their hydrophobicity, surface areas and pore size distribution. The most effective of the activated carbon samples was prepared by impregnation with ZnCl 2 followed by combined physical/chemical activation under carbon dioxide flow at 800 C. Four grams of these samples adsorbed 90% of the oil from 50 mL POME. In the second part, the palm shell-based carbon samples were given magnetic properties by the technique of iron oxide deposition. Ninety-four percent of the activated carbon/iron oxide composite containing the adsorbed oil could be extracted from the POME by a magnetic bar of 0.15 T. Four grams of the composite can remove 85% of oil from 50 mL POME and a total of 67% of the initial oil can then be recovered by hexane extraction. Powder X-ray diffractometry showed the presence of magnetite and maghemite in the activated carbon/iron oxide composite.

- by Chantaraporn Phalakornkule
- •
- Carbon Dioxide, Carbon, Environmental Management, Multidisciplinary

A lthough nanoparticle (NP) assemblies are at the beginning of their development, their unique geometrical shapes and media-responsive optical, electronic, and magnetic properties have attracted significant interest. Nanoscale assembly bridges multiple levels of hierarchy of materials: individual nanoparticles, discrete molecule-like or virus-like nanoscale agglomerates, microscale devices, and macroscale materials. The capacity to self-assemble can greatly facilitate the integration of nanotechnology with other technologies and, in particular, with microscale fabrication. In this Account, we describe developments in the emerging field of dynamic NP assemblies, which are spontaneously form superstructures containing more than two inorganic nanoscale particles that display the ability to change their geometrical, physical, chemical, and other attributes. In many ways, dynamic assemblies can represent a bottleneck in the "bottom-up" fabrication of NP-based devices because they can produce a much greater variety of assemblies, but they also provide a convenient tool for variation of geometries and dimensions of nanoparticle assemblies.

- by Nicholas Kotov
- •
- Electronics, Nanoparticles, Nanotechnology, Anisotropy

W e conducted a double-blind placebo-controlled randomized clinical trial in which 30 patients with pain attributed to carpal tunnel syndrome had either a 1000 gauss magnet or a placebo metal disk applied to the carpal tunnel area using a... more

- by Cheryl Aspy and +1
- •
- Family Practice, Carpal Tunnel Syndrome, Magnetics, Public health systems and services research

The spatiotemporal evolution of field-induced structures in very dilute polarizable colloidal suspensions subject to rotating magnetic fields has been experimentally studied using video microscopy. We found that there is a crossover Mason number ͑ratio of viscous to magnetic forces͒ above which the rotation of the field prevents the particle aggregation to form chains. Therefore, at these high Mason numbers, more isotropic clusters and isolated particles appear. The same behavior was also found in recent scattering dichroism experiments developed in more concentrated suspensions, which seems to indicate that the dynamics does not depend on the volume fraction. Scattering dichroism experiments have been used to study the role played by the volume fraction in suspensions with low concentration. As expected, we found that the crossover Mason number does not depend on the volume fraction. Brownian particle dynamics simulations are also reported, showing good agreement with the experiments.

- by Oscar Santoyo Calderon
- •
- Engineering, Kinetics, Rheology, Anisotropy
- by Edgar Osorio
- •
- Engineering, Magnetic Materials, Nanoparticles, Polymers

Element selective X-ray Detected Magnetic Resonance (XDMR) was measured on exciting the Fe K-edge and Y L-edges in a high quality Yttrium Iron Garnet (YIG) thin film. Resonant pumping at high microwave power was achieved in the nonlinear foldover regime and X-ray Magnetic Circular Dichroism (XMCD) was used to probe the time-invariant change of the magnetization ∆M z due to the precession of the relevant magnetization components at the Fe or Y sites. This challenging experiment required us to design a specific instrumentation. Emphasis is to be laid on the pure orbital character of the effective operators responsible for a K-edge XMCD signal: the XDMR experiment measured at the Fe K-edge thus produces a direct evidence of the forced precession of orbital magnetization DOS.

- by Nicolas Jaouen and +1
- •
- Condensed Matter Physics, Magnetic Resonance Spectroscopy, Synchrotron Radiation, X Rays

Hepatitis A virus (HAV) is an important cause of foodborne disease worldwide. The detection of this virus in naturally contaminated food products is complicated by the absence of a reliable culture method, low levels of contamination, and the presence of matrix-associated compounds which inhibit molecular detection. In this study, we report a novel method to concentrate HAV from foods prior to the application of reverse transcription-PCR (RT-PCR) for detection. Specifically, we used cationically charged magnetic particles with an automated capture system (Pathatrix TM ) to concentrate the virus from 25 g samples of artificially contaminated lettuce, strawberries, green onions, deli-turkey, oysters, and cake with frosting. Detection limits varied according to the product but in most cases, the virus could be consistently detected at input levels corresponding to 10 2 PFU/25 g food sample. For some products, detection was possible at levels as low as 10 −1 PFU/25 g. The assay was applied by a second independent laboratory and was also used to confirm viral contamination of produce items associated with a recent HAV outbreak. Parallel infectivity assays demonstrated that the cationically charged particles bound approximately 50% of the input virus. This is the first application of the automated magnetic capture technology to the concentration of viruses from foods, and it offers promise for facilitating the rapid detection of HAV from naturally contaminated products.

- by Jeffrey Farber
- •
- Microbiology, Medical Microbiology, Food, Cell line

Published clinical evidence has led us to hypothesize that there are parallel pathways which lead to the striate (VI) and prestriate cortex in the human brain. We have used the technique of visually evoked EEC coupled to magnetoencephalography (MEG) to test our hypothesis, by detecting the timing of arrival of signals into these visual areas, using published PET evidence to guide us in the location of the evoked response sources. We found that, if the moving stimulus has a speed of 22° s~', signals arrive in V5 before VI; with speeds of <6° s ', signals arrive in VI first. We conclude that, in addition to the classical picture of a sequential input to prestriate cortex through VI, there is also a fast parallel input which bypasses VI. The parallelism manifests itself only as a function of the characteristics of the visual stimulus, a phenomenon we describe as dynamic parallelism. The results obtained help us explain the residual motion vision of patients with lesions in VI or V5.

- by Semir Zeki
- •
- Magnetoencephalography, Visual perception, Electroencephalography, Motion perception

Magnetotactic bacteria (MTB) are distributed ubiquitously in sediments from coastal environments to the deep sea. The Pacific Manganese Nodule Province contains numerous polymetallic nodules mainly composed of manganese, iron, cobalt, copper and nickel. In the present study we used Illumina MiSeq sequencing technology to assess the communities of putative MTB in deep sea surface sediments at nine stations in the east Pacific Manganese Nodule Province. A total of 402 sequence reads from MTB were classified into six OTUs. Among these, OTU113 and OTU759 were affiliated with the genus Magnetospira, OTU2224 and OTU2794 were affiliated with the genus Magnetococcus and Magnetovibrio, respectively, OTU3017 had no known genus affiliation, and OTU2556 was most similar to Candidatus Magnetananas. Interestingly, OTU759 was widely distributed, occurring at all study sites. Magnetism measurements revealed that all sediments were dominated by low coercivity, non-interacting single domain magnetic ...

- by wuchang zhang
- •
- Microbiology, Minerals, Locomotion, Ecology

Surfactants responsive to pH, temperature, CO 2 , and light are well known. Here we report for the first time ionic liquid surfactants that are magneto-responsive, thus offering the potential to perturb liquid emulsions simply by the application of an external magnetic field. Although ionic liquids (ILs) containing transition metal complexes have been known for some time, [5] it had always been assumed that the metallic centers were isolated, lacking long-range interactions and communication necessary to be magnetically active. Only recently have ionic liquids containing magneto-active metal complex anions, such as 1-methyl-3-butylimidazolium tetrachloroferrate ([bmim]FeCl 4 ), been reported. These magnetic ionic liquids (mag-ILs) are especially interesting as they are molecular liquids, rather than typical magnetic fluids (ferrofluids) which comprise magnetic colloidal particles (! 10 nm) dispersed in a carrier fluid. The nanoparticle-free mag-ILs are themselves paramagnetic. As such they contain high effective concentrations of metal centers and allow physico-chemical properties (hydrophobicity, electrical conductivity, melting point, etc.) to be controlled by external magnetic fields. Furthermore, because mag-ILs and magnetic ionic liquid surfactants (MILSs) are non-volatile they offer advantages over conventional ferrofluids which often employ flammable organic solvents.

- by Annette Schmidt and +1
- •
- Ionic Liquids, CHEMICAL SCIENCES, Magnetics, Surface Tension

Magnetic tunnel junctions sandwiching a superlattice thin film of iron oxide nanocrystals (NCs) have been investigated. The transport was found to be controlled by Coulomb blockade and single-electron tunneling, already at room temperature. A good correlation was identified to hold between the tunnel magnetoresistance (TMR), the expected magnetic properties of the NC arrays, the charging energies evaluated from current-voltage curves, and the temperature dependence of the junction resistance. Notably, for the first time, a switching from negative to positive TMR was observed across the Verwey transition, with a strong enhancement of TMR at low temperatures.

- by chaitanya indira
- •
- Semiconductors, Multidisciplinary, Nanostructures, Magnetics

This paper presents a new Epstein frame optimized for high frequencies and high flux densities. The design philosophy and test results at high power frequencies are presented. The frame achieves high frequency and high flux density performance because of reduced number of turns and reduced number of samples, while using standard 25-cm Epstein samples. For the current application, only the 0.0140-inch (0.36 mm) M45 was used. Measured results obtained show good agreement with the core loss data provided by the steel manufacturers measured using the old frames, at 200 Hz, 300 Hz and 400 Hz. Results at 600 Hz and 1.0 kHz are also presented for the M45 samples along with the test bench used.

- by Tsakani Mthombeni
- •
- High Frequency, High Power, Magnetics, Laminations

Many organisms spanning from bacteria to mammals orient to the earth's magnetic field. For a few animals, central neurons responsive to earth-strength magnetic fields have been identified; however, magnetosensory neurons have yet to be identified in any animal. We show that the nematode Caenorhabditis elegans orients to the earth's magnetic field during vertical burrowing migrations. Well-fed worms migrated up, while starved worms migrated down. Populations isolated from around the world, migrated at angles to the magnetic vector that would optimize vertical translation in their native soil, with northern- and southern-hemisphere worms displaying opposite migratory preferences. Magnetic orientation and vertical migrations required the TAX-4 cyclic nucleotide-gated ion channel in the AFD sensory neuron pair. Calcium imaging showed that these neurons respond to magnetic fields even without synaptic input. C. elegans may have adapted magnetic orientation to simplify their verti...

- by Andrés Vidal-Gadea
- •
- Neuroethology, Sensory Neuroscience, Animal Behavior, Caenorhabditis elegans

The constant growth in generation of solid wastes stimulates studies of recycling processes. The electronic scrap is part of this universe of obsolete and/or defective materials that need to be disposed of more appropriately, or then recycled. In this work, printed circuit boards, that are part of electronic scrap and are found in almost all electro-electronic equipments, were studied. Printed circuit boards were collected in obsolete or defective personal computers that are the largest source of this kind of waste. Printed circuit boards are composed of different materials such as polymers, ceramics and metals, which makes the process more difficult. However, the presence of metals, such as copper and precious metals encourage recycling studies. Also the presence of heavy metals, as Pb and Cd turns this scrap into dangerous residues. This demonstrates the need to search for solutions of this kind of residue, in order to have it disposed in a proper way, without harming the environment. At the first stage of this work, mechanical processing was used, as comminution followed by size, magnetic and electrostatic separation. By this process it was possible to obtain a concentrated fraction in metals (mainly Cu, Pb and Sn) and another fraction containing polymers and ceramics. The copper content reached more than 50% in mass in most of the conductive fractions and significant content of Pb and Sn. At the second stage, the fraction concentrated in metals was dissolved with acids and treated in an electrochemical process in order to recover the metals separately, especially copper. The results demonstrate the technical viability of recovering copper using mechanical processing followed by an electrometallurgical technique. The copper content in solution decayed quickly in all the experiments and the copper obtained by electrowinning is above 98% in most of the tests.

- by Jane Zoppas Ferreira
- •
- Engineering, Materials Science, Electrochemistry, Recycling

It is essential to determine the biodistribution, clearance, and biocompatibility of magnetic nanoparticles (MNPs) for in vivo biomedical applications to ensure their safe clinical use. We have studied these aspects with our novel iron oxide MNP formulation, which can be used as a magnetic resonance imaging (MRI) agent and a drug carrier system. Changes in serum and tissue iron levels were analyzed over 3 weeks after intravenous administration of MNPs to rats. Serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (AKP) levels, and total iron-binding capacity (TIBC) were also measured with time to assess the effect of MNPs on liver function. Selected tissues were also analyzed for oxidative stress and studied histologically to determine biocompatibility of MNPs. Serum iron levels gradually increased for up to 1 week but levels slowly declined thereafter. Biodistribution of iron in various body tissues changed with time but greater fraction of the injected iron localized in the liver and spleen than in the brain, heart, kidney, and lung. Magnetization measurements of the liver and spleen samples showed a steady decrease over 3 weeks, suggesting particle degradation. Serum showed a transient increase in ALT, AST, AKP levels, and TIBC over a period of 6-24 h following MNP injection. The increase in oxidative stress was tissue dependent, reaching a peak at ∼3 days and then slowly declining thereafter. Histological analyses of liver, spleen, and kidney samples collected at 1 and 7 days showed no apparent abnormal changes. In conclusion, our MNPs did not cause long-term changes in the liver enzyme levels or induce oxidative stress and thus can be safely used for drug delivery and imaging applications.

- by Marco Morales
- •
- Magnetic Resonance Imaging, Nanoparticles, Oxidative Stress, Molecular

In this paper are reported experimental results on the effect of a magnetic field on the precipitation process of calcium carbonate scale from a hard water. Carbonically pure water was circulated at a constant flow rate in a magnetic field. After this treatment, calcium carbonate precipitation was induced by degassing dissolved carbonic gas. The nucleation time was identified from the variations of the pH and the Ca 2+ concentration. The ratio between homogeneous and heterogeneous nucleation was determined from the measurement of the mass of precipitated calcium carbonate. It is shown that the magnetic treatment increases the total amount of precipitate. This effect depends on the solution pH, the flow rate and the duration of the treatment. In addition, the magnetic treatment modifies the ratio between homogeneous/heterogeneous nucleation. Homogeneous nucleation is promoted by an increasing the pH of water, the flow rate as well as the residence time. The magnetic treatment enhances these effects with a maximum for a 15 min treatment time. It is shown that the presence of calcium carbonate colloid particles is not necessary. It is advanced that the main magnetic effects concern the associations of ionic species which are present in the solution and which are involved in the nucleation process of calcium carbonate precipitation

- by gabrielli claude
- •
- Chemistry, Water, Carbon Dioxide, Water Purification

Temperature dependencies of thermal expansion coefficients for the alloys of Pd-Ag, Pd-Cu and Pd-Co binary systems were measured at temperatures up to 900•Ž, with heating and cooling rates of 5•Ž/min. The coefficient of thermal expansion of alloys with no transformation in the temperature range of interest in porcelain firing was well approximated by a linear equation of temperature. The constants in the equation were shown as a function of the weight for the added element. Thermal expansion of the palladium-based alloy with no transformation was well estimated at any temperature range and at any composition by using the constants represented here. The coefficients of thermal expansion before and after order-disorder transformation and magnetic transformation were measured in Pd-Cu and Pd-Co alloys, respectively. The results suggest that transient and residual stresses in porcelain-fused-to-metal restorations can be effectively controlled by making use of transformation of the alloy.

- by Kenzo Asaoka
- •
- Dentistry, Biomedical Engineering, Dental Materials, Copper

The synthesis and characterization of new two-dimensional (2D) cyanide-bridged iron(II)-gold(I) bimetallic coordination polymers formulated, {Fe(3-Xpy) 2 [Au(CN) 2 ] 2 } (py ) pyridine; X ) F (1), Cl (2), Br (3), and I (4)) and the clathrate derivative {Fe(3-Ipy) 2 [Au(CN) 2 ] 2 } · 1/2(3-Ipy) (5), are reported. The iron(II) ion lies in pseudoctahedral [FeN 6 ] sites defined by four [Au(CN) 2 ]bridging ligands and two 3-Xpy ligands occupying the equatorial and axial positions, respectively. Although only compounds 2 and 4 can be considered strictly isostructurals, all of the components of this family are made up of parallel stacks of corrugated {Fe[Au(CN) 2 ] 2 } n grids. The grids are formed by edge sharing of {Fe 4 [Au(CN) 2 ] 4 } pseudosquare moieties. The stacks are constituted of double layers sustained by short aurophilic contacts ranging from 3.016(2) to 3.1580(8) Å. The Au · · · Au distances between consecutive double layers are in the range of 5.9562(9)-8.790(2) Å. Compound 5, considered a clathrate derivative of 4, includes one-half of a 3-Ipy molecule per iron(II) atom between the double layers. Compound 1 undergoes a half-spin transition with critical temperatures T c V ) 140 K and T c v ) 145 K. The corresponding thermodynamic parameters derived from differential scanning calorimetry (DSC) are ∆H ) 9.8 ( 0.4 kJ mol -1 and ∆S ) 68.2 ( 3 J K mol -1 . This spin transition is accompanied by a crystallographic phase transition from the monoclinic P2 1 /c space group to the triclinic P1 space group. At high temperatures, where 1 is 100% high-spin, there is only one crystallographically independent iron(II) site. In contrast, the low temperature structural analysis shows the occurrence of two crystallographically independent iron(II) sites with equal population, one high-spin and the other low-spin. Furthermore, 1 undergoes a complete two-step spin transition at pressures as high as 0.26 GPa. Compounds 2-4 are high-spin iron(II) complexes according to their magnetic and [FeN 6 ] structural characteristics. Compound 5, characterized for having two different iron(II) sites, displays a two-step spin transition with critical temperatures of T c 1 ) 155 K, T c 2 V ) 97 K, and T c 2 v ) 110 K. This change of spin state takes place in both sites simultaneously. All of these results are compared and discussed in the context of other {Fe(L) x [M I (CN) 2 ]} coordination polymers, particularly those belonging to the homologous compounds {Fe(3-Xpy) 2 [Ag(CN) 2 ] 2 } and their corresponding clathrate derivatives.

In recent years, techniques have been developed to study and manipulate single molecules of DNA and other biopolymers. In one such technique, the magnetic trap, a single DNA molecule is bound at one end to a glass surface and at the other to a magnetic microbead. Small magnets, whose position and rotation can be controlled, pull on and rotate the microbead. This provides a simple method to stretch and twist the molecule. The system allows one to apply and measure forces ranging from 10(-3) to >100 picoNewtons (pN). In contrast to other techniques, the force measurement is absolute and does not require calibration of the sensor. This protocol describes a procedure for building and using a magnetic trap. It gives a method for constructing a microchamber suitable for magnetic tweezers studies, including antibody coating and passivation. It also describes a series of simple steps to achieve end-labeling of DNA anchoring fragments. One anchoring fragment is biotin-labeled and the othe...

- by Terence R Strick
- •
- Nanotechnology, DNA, Biotin, Magnetics

Saxitoxin (STX) is a low molecular weight neurotoxin mainly produced by certain marine dinoflagellates that, along with its family of similarly related paralytic shellfish toxins, may cause the potentially fatal intoxication known as paralytic shellfish poisoning. Illness and fatality rates are low due to the effective monitoring programs that determine when toxins exceed the established regulatory action level and effectuate shellfish harvesting closures accordingly. Such monitoring programs rely on the ability to rapidly screen large volumes of samples. Many of the screening assays currently available employ antibodies or live animals. This research focused on developing an analytical recognition element that would eliminate the challenges associated with the limited availability of antibodies and the use of animals. Here we report the discovery of a DNA aptamer that targets STX. Concentration-dependent and selective binding of the aptamer to STX was determined using a surface plasmon resonance sensor. Not only does this work represent the first reported aptamer to STX, but also the first aptamer to any marine biotoxin. A novel strategy of using a toxin-protein conjugate for DNA aptamer selection was successfully implemented to overcome the challenges associated with aptamer selection to small molecules. Taking advantage of such an approach could lead to increased diversity and accessibility of aptamers to low molecular weight toxins, which could then be incorporated as analytical recognition elements in diagnostic assays for foodborne toxin detection. The selected STX aptamer sequence is provided here, making it available to any investigator for use in assay development for the detection of STX.

- by Katrina Campbell
- •
- Protein Folding, Calibration, Surface plasmon resonance, Proteins

Several species of magnetotactic bacteria were discovered in the lakes and ponds of Georgia. Electron microscopic analysis of the bacteria showed a great variety of microbial forms as well as magnetosome arrangements. Pyramidal, cubical or hexagonal magnetic grains could be seen in different species of bacteria. The linear organization of magnetic particles was prevailing, although gathered magnetosomes were also seen. Magnetometric measurement of magnetic particles obtained from coccoid bacteria was performed. Remnent acquisition curves, as well as thermomagnetic curves of investigated material showed that the magnetosomes under study contained pure single-domain magnetite. Magnetotactic bacteria, first discovered more than 15 years ago by BLAKEMORE (1975), still remain one of the most intriguing organisms of the microbial world. In the years since their discovery several groups of scientists have studied some of the biochemical and morphophysiological properties of these bacteria. These studies have determined several

- by Teymuras Kurzchalia
- •
- Microbiology, Medical Microbiology, Bacteria, Magnetotactic Bacteria

A series of surface-modified clays containing nanophase (np) iron oxide/oxyhydroxides of extremely small particle sizes, with total iron contents as high as found in Mars soil, were prepared by iron deposition on the clay surface from ferrous chloride solution. Comprehensive studies of the iron mineralogy in these "Mars-soil analogs" were conducted using chemical extractions, solubility analyses, pH and redox, x ray and electron diffractometry, electron microscopic imaging, specific surface area and particle size determinations, differential thermal analyses, magnetic properties characterization, spectral reflectance, and Viking biology simulation experiments. The clay matrix and the procedure used for synthesis produced nanophase iron oxides containing a certain proportion of divalent iron, which slowly converts to more stable, fully oxidized iron minerals. The clay acted as an effective matrix, both chemically and sterically, preventing the major part of the synthesized iron oxides from ripening, i.e., growing and developing larger crystals. The precipitated iron oxides appear as isodiametric or slightly elongated particles in the size range 1-10 nm, having large specific surface area. The noncrystalline nature of the iron compounds precipitated on the surface of the clay was verified by their complete extractability in oxalate. Lepidocrocite (3,-FeOOH) was detected by selected area electron diffraction. It is formed from a double iron Fe(II)/Fe(III) hydroxy mineral such as "green rust," or ferrosic hydroxide. Magnetic measurements suggested that lepidocrocite converted to the more stable maghemite (3,-Fe203) by mild heat treatment and then to nanophase hematite (a-Fe203) by extensive heat treatment. After mild heating, the iron-enriched clay became slightly magnetic, to the extent that it adheres to a hand-held magnet, as was observed with Mars soil. The chemical reactivity of the iron-enriched clays strongly resembles, and offers a plausible mechanism for, the somewhat puzzling observations of the Viking biology experiments. Their unique chemical reactivities are attributed to the combined catalytic effects of the iron oxide/oxyhydroxide and silicate phase surfaces. The reflectance spectrum of the clay-iron preparations in the visible range is generally similar to the reflectance curves of bright regions on Mars. This strengthens the evidence for the predominance of nanophase iron oxides/oxyhydroxides in Mars soil. The mode of formation of these nanophase iron oxides on Mars is still unknown. It is puzzling that despite the long period of time since aqueous weathering took place on Mars, they have not developed from their transitory stage to well-crystallized end-members. The possibility is suggested that these phases represent a continuously on-going, extremely slow weathering process. 20,831 20,832 BANIN ET AL.: NANOPHASE IRON MINERALS IN MA•S SOIL detection systems during the 1988-1990 oppositions [Bell et al., 1990; Roush et al., 1993; Singer et al., 1990]. Yet the mineralogical nature of the soil is far from being understood, nor are its time of formation and weathering processes known.

- by David Blake
- •
- Mars, Electron Diffraction, Heat Treatment, Multidisciplinary

In 1 split-brain patient and 13 patients with circumscript surgical lesions within different parts of the corpus callosum (CC), the topography of fibers within the CC mediating an interhemispheric inhibition between the motor cortices was investigated in the phase of a stable disconnection syndrome. The aim of the study was to characterize the system of callosal fibers activated by transcranial magnetic brain stimulation in more detail as a basis for a diagnostic application of this technique. The locations and areas of the lesions were measured on sagittal magnetic resonance (MR) slices and attributed to five segments of the CC, because the borders of the anatomic subdivisions of the CC are not clearly defined. Transcallosal inhibition (TI) of tonic electromyographical hand muscle activity was elicited by focal transcranial magnetic stimulation over the primary motor cortex. In a reference group of normal subjects, TI started after 35.8 * 3.6 msec had a duration of 24.8 2 2.7 msec and an estimated transcallosal conduction time of 15.5 & 3.0 msec (range, 10.2-20.0 msec, n = 24 hands). No significant differences were found for the TI originating from the right and left motor cortices. From the absence and presence of TI in patients with lesions in different parts of the CC it can be concluded that most of the fibers mediating TI pass through the posterior third and anterior fourth segment of the CC, that is, through the posterior half of the trunk of the CC. The clinical findings suggest a role for TI in the performance of fast and complex hand motor tasks. Meyer B-U, Roricht S, Woiciechowsky C. Topography of fibers in the human corpus callosum mediating interhemispheric inhibition benveen the motor cortices. A n n Neurol 1998;43:360 -369 Different approaches using transcranial electrical and magnetic brain stimulation have previously been used to investigate interhemispheric connections in intact and unanesthetized humans. Transcranial stimulation over the frontal cortex elicited a surface positive evoked potential over homologous cortical areas of the other hemisphere that was attributed to transfers along fibers passing through the corpus callosum (CC). 1,2 Because of difficulties with artifacts when recording evoked potentials only 10 to 15 cm from the stimulation site, this technique was not found to be useful for a routine diagnostic testing of the function of callosal fibers. Another more simple and practical approach to a neurophysiological testing of interhemispheric transfers is based on the observation that brief magnetoelectric stimuli applied focally to the primary motor cortex of one hemisphere were found to suppress ongoing voluntary electromyographical (EMG) activity in ipsilat-era1 hand This inhibition begins 10 to 20 msec after the minimum corticospinal conduction time and lasts, on average, 25 msec. That this inhibition is mediated by callosal fibers and then by contralaterally projecting corticospinal connections and not by ipsilaterally projecting descending pathways could be shown in patients with capsular infarcts5 and complete agenesis of the CC.6 Previous studies of patients with partial agenesis of the C C did not supply reliable information about the topography of fibers mediating transcallosal inhibition (TI), because organizational changes of callosal connections have to be expected in such patients.' To characterize the anatomical structures involved in the generation of TI in more detail and by this to establish a basis for a more widespread diagnostic use of this approach, we investigated the topography of fibers within the CC mediating this phenomenon. For this, patients with surgical lesions in different parts of the CC were examined. The lesions were localized on magnetic resonance (MR) images and then attributed to five segments of the CC' because the borders of the rostrum, genu, truncus, and splenium are not clearly defined anatomically.' A few aspects of this work have previously been published in abstract form.' From the

- by Christian Woiciechowsky
- •
- Magnetic Resonance Imaging, Adolescent, Child, Corpus Callosum