Fri, 04 Jul 2008 23:52:45 BST CiteULike: Tag magnetic http://www.citeulike.org/tag/magnetic CiteULike.org en-gb Copyright © 2004-2008 citeulike.org http://www.citeulike.org/user/zwang/article/2569274 <i>RNA, Vol. 10, No. 10. (1 October 2004), pp. 1595-1608.</i><br /><br />Ribonuclease P (RNase P) is a ribonucleoprotein complex that catalyzes the cleavage of the 5' end of precursor tRNA. To characterize the interface between the Bacillus subtilis RNA (PRNA) and protein (P protein) components, the intraholoenzyme KD is determined as a function of ionic strength using a magnetocapture-based assay. Three distinct phases are evident. At low ionic strength, the affinity of PRNA for P protein is enhanced as the ionic strength increases mainly due to stabilization of the PRNA structure by cations. Lithium substitution in lieu of potassium enhances the affinity at low ionic strength, whereas the addition of ATP, known to stabilize the structure of P protein, does not affect the affinity. At high ionic strength, the observed affinity decreases as the ionic strength increases, consistent with disruption of ionic interactions. These data indicate that three to four ions are released on formation of holoenzyme, reflecting the number of ion pairs that occur between the P protein and PRNA. At moderate ionic strength, the two effects balance so that the apparent KD is not dependent on the ionic strength. The KD between the catalytic domain (C domain) and P protein has a similar triphasic dependence on ionic strength. Furthermore, the intraholoenzyme KD is identical to or tighter than that of full-length PRNA, demonstrating that the P protein binds solely to the C domain. Finally, pre-tRNAasp (but not tRNAasp) stabilizes the PRNA*P protein complex, as predicted by the direct interaction between the P protein and pre-tRNA leader. 10.1261/rna.7550104 Ionic interactions between PRNA and P protein in Bacillus subtilis RNase P characterized using a magnetocapture-based assay Jeremy Day-Storms S Niranjanakumari Carol Fierke doi:10.1261/rna.7550104 RNA, Vol. 10, No. 10. (1 October 2004), pp. 1595-1608. 2008-03-21T07:55:24-00:00 2004 RNA 10 10 1595 1608 bacterial interaction magnetic protein rna rnasep http://www.citeulike.org/user/yavanna/article/2236570 <i>Proceedings of the National Academy of Sciences, Vol. 105, No. 2. (15 January 2008), pp. 698-703.</i><br /><br />A cell delivery strategy was investigated that was hypothesized to enable magnetic targeting of endothelial cells to the steel surfaces of intraarterial stents because of the following mechanisms: (i) preloading cells with biodegradable polymeric superparamagnetic nanoparticles (MNPs), thereby rendering the cells magnetically responsive; and (ii) the induction of both magnetic field gradients around the wires of a steel stent and magnetic moments within MNPs because of a uniform external magnetic field, thereby targeting MNP-laden cells to the stent wires. In vitro studies demonstrated that MNP-loaded bovine aortic endothelial cells (BAECs) could be magnetically targeted to steel stent wires. In vivo MNP-loaded BAECs transduced with adenoviruses expressing luciferase (Luc) were targeted to stents deployed in rat carotid arteries in the presence of a uniform magnetic field with significantly greater Luc expression, detected by in vivo optical imaging, than nonmagnetic controls. 10.1073/pnas.0708338105 High field gradient targeting of magnetic nanoparticle-loaded endothelial cells to the surfaces of steel stents Boris Polyak Ilia Fishbein Michael Chorny Ivan Alferiev Darryl Williams Ben Yellen Gary Friedman Robert Levy doi:10.1073/pnas.0708338105 Proceedings of the National Academy of Sciences, Vol. 105, No. 2. (15 January 2008), pp. 698-703. 2008-01-15T22:39:52-00:00 2008 Proceedings of the National Academy of Sciences 105 2 698 703 endothelial_cell magnetic medical_science http://www.citeulike.org/user/vdbroekw/article/1430090 <i>Am J Psychiatry, Vol. 164, No. 7. (1 July 2007), 1118.</i><br /><br />10.1176/appi.ajp.164.7.1118 Repetitive Transcranial Magnetic Stimulation Versus Electroconvulsive Therapy: Efficacy of Treatment in Nonpsychotic Patients With Depression Philip Janicak Sheila Dowd Jeffrey Rado Mary Welch Louis Fogg Johnny O'Reardon David Avery Edward Coffey Shirlene Sampson Nash Boutros doi:10.1176/appi.ajp.164.7.1118 Am J Psychiatry, Vol. 164, No. 7. (1 July 2007), 1118. 2007-07-03T06:38:20-00:00 2007 Am J Psychiatry 164 7 1118 depression ect electroconvulsive electroshock magnetic stimulation therapy transcranial http://www.citeulike.org/user/sverzijl/article/1523344 <i>Science, Vol. 317, No. 5834. (6 July 2007), pp. 83-86.</i><br /><br />Using self-resonant coils in a strongly coupled regime, we experimentally demonstrated efficient nonradiative power transfer over distances up to 8 times the radius of the coils. We were able to transfer 60 watts with [~]40% efficiency over distances in excess of 2 meters. We present a quantitative model describing the power transfer, which matches the experimental results to within 5%. We discuss the practical applicability of this system and suggest directions for further study. 10.1126/science.1143254 Wireless Power Transfer via Strongly Coupled Magnetic Resonances Andre Kurs Aristeidis Karalis Robert Moffatt JD Joannopoulos Peter Fisher Marin Soljacic doi:10.1126/science.1143254 Science, Vol. 317, No. 5834. (6 July 2007), pp. 83-86. 2007-07-31T01:21:44-00:00 2007 Science 317 5834 83 86 magnetic power resonance wireless http://www.citeulike.org/user/sndwchmn/article/1554639 <i>New Scientist (10 August 2007)</i><br /><br />One of the few scientific success stories of the International Space Station has been its use to grow large, pure crystals in microgravity (see Space station unlocks new world of crystals[30]). Magnetic gravity trick grows perfect crystals Kurt Kleiner New Scientist (10 August 2007) 2007-08-11T22:27:27-00:00 2007 New Scientist magnetic microgravity http://www.citeulike.org/user/skoch3/article/1106506 <i>Journal of Micromechanics and Microengineering, Vol. 15, No. 1. (2005), pp. 109-117.</i><br /><br />A micromachine-based DNA manipulation platform for stretching and rotation of a single DNA molecule is reported. The DNA molecule with a 2 nm diameter could be successfully manipulated using magnetic forces generated by arrayed microcoils fabricated by MEMS (micro-electro-mechanical systems) technology. Key platform technologies including localized DNA immobilization, microcoil fabrication and microfluidics, have been integrated to form the DNA magnetic tweezers. One end of a single DNA molecule is specifically bonded onto a magnetic bead and the other end onto a gold surface. It is then manipulated under a magnetic field generated by built-in hexagonally aligned microcoils. Design and simulation of the magnetic tweezers are carried out by using numerical software. A highly effective and strong binding method for the construction of two sticky ends of a DNA is developed, which is compatible with MEMS technologies. To quantify the magnitude of magnetic forces acting on the DNA, force calibration is performed and further verified by the worm-like chain (WLC) model. The measured DNA stretching forces are found to be in reasonable agreement with the theoretical values. We have successfully demonstrated the stretching and rotation of the tethered-bead DNA molecule linked to a gold pattern using the developed method. The spring constant of the DNA molecule is experimentally found to be about 10$^&minus;8$&ndash;10$^&minus;7$ N m$^&minus;1$. The development of the proposed method could be useful for investigation of DNA biophysical properties. A micromachined DNA manipulation platform for the stretching and rotation of a single DNA molecule The preliminary results of the current paper were presented at the IEEE 17th International MEMS Conference (IEEE MEMS 2004), Maastricht, Netherlands, 25&ndash;29 Jan. 2004. Chi Chiou Gwo Lee doi:10.1088/0960-1317/15/1/017 Journal of Micromechanics and Microengineering, Vol. 15, No. 1. (2005), pp. 109-117. 2007-02-14T06:58:48-00:00 2005 Journal of Micromechanics and Microengineering 15 1 109 117 beads biomems biophysics dna force magnetic mems microspheres single-molecule http://www.citeulike.org/user/skoch3/article/1237423 <i>Review of Scientific Instruments, Vol. 76, No. 5. (2005)</i><br /><br />We report here the development of a three-dimensional (3D) magnetic force microscope for applying forces to and measuring responses of biological systems and materials. This instrument combines a conventional optical microscope with a free-floating or specifically bound magnetic bead used as a mechanical probe. Forces can be applied by the bead to microscopic structures of interest (specimens), while the reaction displacement of the bead is measured. This enables 3D mechanical manipulations and measurements to be performed on specimens in fluids. Force is generated by the magnetically permeable bead in reaction to fields produced by external electromagnets. The displacement is measured by interferometry using forward light scattered by the bead from a focused laser beam. The far-field interference pattern is imaged on a quadrant photodetector from which the 3D displacement can be computed over a limited range about the focal point. The bead and specimen are mounted on a 3D translation stage and feedback techniques are used to keep the bead within this limited range. We demonstrate the system with application to beads attached to cilia in human lung cell cultures. ©2005 American Institute of Physics Three-dimensional force microscope: A nanometric optical tracking and magnetic manipulation system for the biomedical sciences JK Fisher JR Cummings KV Desai L Vicci B Wilde K Keller C Weigle G Bishop RM Taylor Ii CW Davis RC Boucher Timothy O'Brien R Superfine doi:10.1063/1.1914777 Review of Scientific Instruments, Vol. 76, No. 5. (2005) 2007-04-19T18:12:46-00:00 2005 Review of Scientific Instruments 76 5 AIP 3d biophysics force magnetic microscope nanomanipulation spectroscopy http://www.citeulike.org/user/skoch3/article/1237415 <i>Review of Scientific Instruments, Vol. 77, No. 2. (2006)</i><br /><br />Forces play a key role in a wide range of biological phenomena from single-protein conformational dynamics to transcription and cell division, to name a few. The majority of existing microbiological force application methods can be divided into two categories: those that can apply relatively high forces through the use of a physical connection to a probe and those that apply smaller forces with a detached probe. Existing magnetic manipulators utilizing high fields and high field gradients have been able to reduce this gap in maximum applicable force, but the size of such devices has limited their use in applications where high force and high-numerical-aperture (NA) microscopy must be combined. We have developed a magnetic manipulation system that is capable of applying forces in excess of 700  pN on a 1  µm paramagnetic particle and 13  nN on a 4.5  µm paramagnetic particle, forces over the full 4  sr, and a bandwidth in excess of 3  kHz while remaining compatible with a commercially available high-NA microscope objective. Our system design separates the pole tips from the flux coils so that the magnetic-field geometry at the sample is determined by removable thin-foil pole plates, allowing easy change from experiment to experiment. In addition, we have combined the magnetic manipulator with a feedback-enhanced, high-resolution (2.4  nm), high-bandwidth (10  kHz), long-range (100  µm xyz range) laser tracking system. We demonstrate the usefulness of this system in a study of the role of forces in higher-order chromosome structure and function. ©2006 American Institute of Physics Thin-foil magnetic force system for high-numerical-aperture microscopy JK Fisher J Cribb KV Desai L Vicci B Wilde K Keller RM Taylor Ii J Haase K Bloom Timothy O'Brien R Superfine doi:10.1063/1.2166509 Review of Scientific Instruments, Vol. 77, No. 2. (2006) 2007-04-19T18:08:44-00:00 2006 Review of Scientific Instruments 77 2 AIP biophysics force magnetic microfabricated pieces pole spectroscopy http://www.citeulike.org/user/skoch3/article/1085854 <i>Applied Physics Letters, Vol. 89, No. 17. (2006)</i><br /><br />We describe a micromachined force sensor that is able to measure forces as small as 1  pN in both air and water. First, we measured the force field produced by an electromagnet on individual 2.8  µm magnetic beads glued to the sensor. By repeating with 11 different beads, we measured a 9% standard deviation in saturation magnetization. We next demonstrated that the sensor was fully functional when immersed in physiological buffer. These results show that the force sensors can be useful for magnetic force calibration and also for measurement of biophysical forces on chip. ©2006 American Institute of Physics Micromachined piconewton force sensor for biophysics investigations Steven Koch Gayle Thayer Alex Corwin Maarten de Boer doi:10.1063/1.2364118 Applied Physics Letters, Vol. 89, No. 17. (2006) 2007-02-03T09:23:18-00:00 2006 Applied Physics Letters 89 17 AIP beads biomems biophysics electromagnet force magnetic mems micromachined microspheres sensor summit http://www.citeulike.org/user/silverplasma/article/1639418 <i>Applied Physics Letters, Vol. 88 (March 2006), 4107.</i><br /><br />We show that the interaction between magnetic microspheres, fabricated by coating glass microspheres with a layer of nickel, can be controlled by varying the frequency of the applied magnetic field. By floating two such microspheres on the meniscus of glycerin and applying an ac magnetic field, it is shown that the spheres achieve an equilibrium separation owing to the balance between the repulsive dipole-dipole interaction and the “attractive” force due to the weight of the particles. A monotonic decrease of the magnetorheological effect with frequency increasing is observed. Good agreement between theory and experiment is observed. Frequency-controlled interaction between magnetic microspheres X Zhang L Liu Y Qi Z Liu J Shi W Wen doi:10.1063/1.2189830 Applied Physics Letters, Vol. 88 (March 2006), 4107. 2007-09-09T18:14:55-00:00 2006 Applied Physics Letters 88 4107 frequency magnetic nickel nonlinear rotation http://www.citeulike.org/user/sidkshatriya/article/2089124 <i>American Journal of Physics, Vol. 61, No. 4. (1993), pp. 304-309.</i><br /><br />A three dimensional magnetic confinement system is presented which will trap both macroscopic and atomic magnetic dipoles. The dipole is confined by dc and oscillating magnetic fields, and its motion is described by the Mathieu equation. Most aspects of the dynamics of the trapped objects depend only on the ratio of the magnetic moment to the mass of the dipole. Similar motion was observed for masses varying over 21 orders of magnitude (from 1 atom to 0.2 g). The trap is constructed from inexpensive permanent magnets and small coils which are driven by 60 Hz line current. The design of the trap as well as the behavior of the trapped particle are discussed herein. ©1993 American Association of Physics Teachers A magnetic suspension system for atoms and bar magnets C Sackett E Cornell C Monroe C Wieman doi:10.1119/1.17261 American Journal of Physics, Vol. 61, No. 4. (1993), pp. 304-309. 2007-12-11T10:49:29-00:00 1993 American Journal of Physics 61 4 304 309 AAPT atomic-physics experimental-project magnetic trap http://www.citeulike.org/user/sdhauck/article/463775 <i>Earth and Planetary Science Letters, Vol. 241, No. 1-2. (15 January 2006), pp. 2-10.</i><br /><br />Surface heat flows are calculated from elastic lithosphere thicknesses for the heavy cratered highlands of Mars, in terms of the fraction of the surface heat flow derived from crustal heat sources. Previous heat flow estimations for Mars used linear thermal gradients, which is equivalent to ignoring the existence of heat sources within the crust. We compute surface heat flows following a methodology that relates effective thickness and curvature of an elastic plate with the strength envelope of the lithosphere, and assuming crustal heat sources homogeneously distributed in a radioactive element-rich layer 20 or 60 km thick. The obtained results show that the surface heat flow increases with the proportion of heat sources within the crust, and with the decrease of both radioactive element-rich layer thickness and surface temperature. Also, the results permit us to calculate representative temperatures for the crust base, rock strength for the upper mantle, and lower and upper limits to the crustal magnetization depth and intensity, respectively. For Terra Cimmeria, an effective elastic thickness of 12 km implies between 30% and 80% of heat sources located within the crust. In this case the uppermost mantle would be weak at the time of loading, and temperatures in the lower crust cold enough to favor unrelaxed crustal thickness variations and to permit deep Curie depths in the highlands, as suggested by the observational evidence. The early thermal and magnetic state of the cratered highlands of Mars Javier Ruiz Patrick Mcgovern Rosa Tejero doi:10.1016/j.epsl.2005.10.016 Earth and Planetary Science Letters, Vol. 241, No. 1-2. (15 January 2006), pp. 2-10. 2006-01-13T00:57:45-00:00 2006 Earth and Planetary Science Letters 241 1-2 2 10 crust flexure flow heat lithosphere magnetic mars http://www.citeulike.org/user/rolayo/article/2295251 <i>Polymer, Vol. 46, No. 13. (17 June 2005), pp. 4596-4603.</i><br /><br />This is a second paper in the series concerning the synthesis and characterization of composite polymeric particles with encapsulated magnetic iron oxide and bearing reactive [beta]-diketone groups on the surface. Composite particles have been prepared by two-step method in which first step requires preparation of the iron oxide nano-particles and during second step iron oxide was encapsulated into formed poly(styrene/acetoacetoxyethyl methacrylate) (PS-AAEM) particles directly during polymerization process. It has been found that the modification of the iron oxide nano-particle surface with sodium oleate improves significantly the encapsulation during polymerization process. This procedure gives a possibility to obtain composite particles with raspberry morphology and both the particle size and iron oxide content can be varied. Change of monomer to iron oxide ratio gives a possibility to change effectively the morphology of hybrid particles, however, polydispersity of composite particles increases at higher content of magnetic particles in the system. Variation of AAEM concentration in reaction mixture at constant iron oxide particles concentration gives a possibility to control the particle size of formed hybrid microspheres. Composite particles were characterized by dynamic light scattering and electron microscopy (SEM) with respect to their particle size and morphology of the surface layer. X-ray diffraction (XRD) and magnetization measurements indicate presence of maghemite ([gamma]-Fe2O3) in composite particles. Composite magnetic particles: 2. Encapsulation of iron oxide by surfactant-free emulsion polymerization A Pich S Bhattacharya A Ghosh HJP Adler doi:10.1016/j.polymer.2005.01.017 Polymer, Vol. 46, No. 13. (17 June 2005), pp. 4596-4603. 2008-01-27T19:06:51-00:00 2005 Polymer 46 13 4596 4603 magnetic nanoparticles http://www.citeulike.org/user/rolayo/article/2295232 <i>International Journal of Pharmaceutics, Vol. 338, No. 1-2. (29 June 2007), pp. 248-257.</i><br /><br />Oleic acid-coated magnetite has been encapsulated in biocompatible magnetic nanoparticles (MNP) by a simple emulsion evaporation method. The different parameters influencing the particles size were studied. Between these parameters, the stirring speed and the polymer concentration were found to influence positively or negatively, respectively, the MNP size which varied between 320 and 1500 nm. The magnetite encapsulation efficacy was about than 90% yielding a high magnetite loading of up to 30% (w/w). X-ray diffraction showed that magnetite crystalline pattern was not modified after emulsification and solvent evaporation. The X-ray photoelectron spectroscopy (XPS) results indicated the presence of less than 0.1% of iron atoms at the nanoparticles surface. Vibration simple magnetometer (VSM) showed a superparamagnetic behaviour of the MNP and a saturation magnetization increasing with the increased magnetite amount used in formulation. Moreover, T1 and T2 relaxivities of MNP (4.7 T, 20 [degree sign]C) were 1.7 +/- 0.1 and 228.3 +/- 13.1 s-1 mM-1, respectively, rendering them in the same category of known negative contrast agents which shorten the T2 relaxation time. Therefore, by using an appropriate anticancer drug in their formulation, these magnetic nanoparticles can present a promising mean for simultaneous tumor imaging, drug delivery and real time monitoring of therapeutic effect. Elaboration of PLLA-based superparamagnetic nanoparticles: Characterization, magnetic behaviour study and in vitro relaxivity evaluation Misara Hamoudeh Achraf Faraj Emmanuelle Canet-Soulas Francois Bessueille Didier Leonard Hatem Fessi doi:10.1016/j.ijpharm.2007.01.023 International Journal of Pharmaceutics, Vol. 338, No. 1-2. (29 June 2007), pp. 248-257. 2008-01-27T18:47:22-00:00 2007 International Journal of Pharmaceutics 338 1-2 248 257 magnetic nanoparticles polylactide http://www.citeulike.org/user/rolayo/article/2295164 <i>Journal of Polymer Science Part A: Polymer Chemistry, Vol. 43, No. 15. (2005), pp. 3221-3231.</i><br /><br />Superparamagnetic and biodegradable/biocompatible core-corona nanocomposite particles were prepared by ring-opening polymerization of &epsi;-caprolactone initiated from the surface of maghemite. As was done in a previous work, an aminosilane coupling agent was chosen as the coinitiator and immobilized at the surface of the maghemite particles to allow the growth of the poly(&epsi;-caprolactone) (PCL) chains from the solid surface. Two different catalytic systems based on aluminum and tin alkoxides were investigated. Whatever the catalyst used, diffuse reflectance Fourier transform spectroscopy brought evidence for polymer anchoring through a covalent bond, whereas thermogravimetric analysis attested to the presence of high amounts of PCL around the maghemite. Magnetization measurements proved that the nanocomposites kept their superparamagnetic properties after coating. The polymer contents obtained by this grafting-from route were compared with the results obtained by a more classical grafting-to process. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3221-3231, 2005 Synthesis of colloidal superparamagnetic nanocomposites by grafting poly(&epsi;-caprolactone) from the surface of organosilane-modified maghemite nanoparticles C Flesch E Bourgeat-Lami S Mornet E Duguet C Delaite P Dumas doi:10.1002/pola.20772 Journal of Polymer Science Part A: Polymer Chemistry, Vol. 43, No. 15. (2005), pp. 3221-3231. 2008-01-27T17:36:06-00:00 2005 Journal of Polymer Science Part A: Polymer Chemistry 43 15 3221 3231 magnetic nanoparticles polycaprolactone http://www.citeulike.org/user/rolayo/article/2295114 <i>International Journal of Pharmaceutics, Vol. 324, No. 2. (6 November 2006), pp. 185-190.</i><br /><br />Magnetic poly [var epsilon]-caprolactone (PCL) nanoparticles were prepared in a well shaped spherical form by the o/w emulsion method. The influence of some preparative variables on the size and surface property was investigated. Nanoparticles were smooth, well individualized and homogeneous in size. The presence of magnetite and its superparamagnetic characteristic were confirmed by transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FT-IR) and vibrating sample magnetometer (VSM), respectively. The anti-cancer drug was encapsulated in the magnetic nanoparticle during preparation. A typical release behavior was observed for 30 days. In vitro experiment of magnetic susceptibility under external magnetic field demonstrated that the magnetic PCL nanoparticles have sufficient magnetic susceptibility for a potential magnetic drug carrier for targeted delivery. Preparation of poly [var epsilon]-caprolactone nanoparticles containing magnetite for magnetic drug carrier J Yang SB Park Ho-Geun Yoon YM Huh S Haam doi:10.1016/j.ijpharm.2006.06.029 International Journal of Pharmaceutics, Vol. 324, No. 2. (6 November 2006), pp. 185-190. 2008-01-27T16:48:07-00:00 2006 International Journal of Pharmaceutics 324 2 185 190 magnetic nanoparticles polycaprolactone http://www.citeulike.org/user/rodney/article/2295820 <i>Biophys. J., Vol. 76, No. 1. (1 January 1999), pp. 573-579.</i><br /><br />We measured the viscoelastic properties of the cytoplasm of J774 macrophages with a recently developed microrheometer. Ferromagnetic beads (1.3 microm in diameter) were used to determine the local viscoelastic moduli. Step-force pulses were applied to the magnetic beads and the displacement was observed by single particle tracking. By analyzing the creep response curves in terms of a triphasic mechanical equivalent circuit, we measured the shear elastic modulus, the effective viscosities, and the strain relaxation time. The values of the shear modulus vary by more than an order of magnitude within the cell population (range, 20-735 Pa; average, 343 Pa) and by a factor of 2 within single cells. The effective viscosity of the cytoplasm exhibits a relatively sharp distribution about an average of [eta] = 210 Pa s (+/- 143 Pa s). We measured the displacement field generated by the local forces by observing the induced motion of nonmagnetic beads. Even at distances of the order of 1 microm, no induced motion was seen, suggesting that the cytoplasm is composed of clusters of densely packed and cross-linked filaments separated by soft regions. In another series of experiments we analyzed the magnetophoretic motion of the ferromagnetic beads at a constant magnetic force. Measuring the bead velocity parallel and perpendicular to the applied force showed that local active forces on the beads varied from 50 to 900 pN. Measurement of Local Viscoelasticity and Forces in Living Cells by Magnetic Tweezers Andreas Bausch Winfried Moller Erich Sackmann Biophys. J., Vol. 76, No. 1. (1 January 1999), pp. 573-579. 2008-01-28T02:37:28-00:00 1999 Biophys. J. 76 1 573 579 forces intracellular magnetic tweezers viscoelasticity http://www.citeulike.org/user/rodney/article/2295799 <i>Review of Scientific Instruments, Vol. 67, No. 3. (1996), pp. 818-827.</i><br /><br />  A magnetic manipulator for studying local rheology and micromechanical properties of biological systems Fran\ccois Amblard Bernard Yurke Andrew Pargellis Stanislas Leibler Review of Scientific Instruments, Vol. 67, No. 3. (1996), pp. 818-827. 2008-01-28T02:29:02-00:00 1996 Review of Scientific Instruments 67 3 818 827 AIP magnetic microrheology tweezers http://www.citeulike.org/user/rodney/article/2295784 <i>Science, Vol. 271 (March 1996), pp. 1835-1837.</i><br /><br />Single linear DNA molecules were bound at multiple sites at one extremity to a treated glass cover slip and at the other to a magnetic bead. The DNA was therefore torsionally constrained. A magnetic field was used to rotate the beads and thus to coil and pull the DNA. The stretching force was determined by analysis of the Brownian fluctuations of the bead. Here, the elastic behavior of individual lambda DNA molecules over-and underwound by up to 500 turns was studied. A sharp transition was discovered from a low to a high extension state at a force of ~0.45 piconewtons for underwound molecules and at a force of ~3 piconewtons for overwound ones. These transitions, probably reflecting the formation of alternative structure in stretched coiled DNA molecules, might be relevant for DNA transcription and replication. The Elasticity of a Single Supercoiled DNA Molecule TR Strick JF Allemand D Bensimon A Bensimon V Croquette Science, Vol. 271 (March 1996), pp. 1835-1837. 2008-01-28T02:17:45-00:00 1996 Science 271 1835 1837 dna elasticity magnetic supercoiled tweezers http://www.citeulike.org/user/rodney/article/1280180 <i>Nano Lett., Vol. 7, No. 4. (11 April 2007), pp. 1010-1012.</i><br /><br />Abstract: Overdamped magnetic nanorod-gyroscopes driven by a rotating magnetic field undergo a series of reorientations when sedimenting on top of a surface in a viscous liquid. By changing the amplitude and the rotation frequency of the driving magnetic field, the nanorod-gyroscope either synchronizes or desynchronizes with the field and rotates either around its long or short axis. The different regimes of motion are explained theoretically by coupling the nanorod-gyroscopes motion to the creeping flow equations of the surrounding fluid. It is shown that friction anisotropy plays an important role for the orientation of the nanorod-gyroscopes. Orientations of Overdamped Magnetic Nanorod-Gyroscopes P Dhar CD Swayne TM Fischer T Kline A Sen doi:10.1021/nl0701556 Nano Lett., Vol. 7, No. 4. (11 April 2007), pp. 1010-1012. 2007-05-06T03:41:15-00:00 2007 Nano Lett. 7 4 1010 1012 gyroscope magnetic nanorod http://www.citeulike.org/user/rodney/article/2295738 <i>Biophys. J., Vol. 88, No. 3. (1 March 2005), pp. 2137-2144.</i><br /><br />This study reports the design, realization, and characterization of a multi-pole magnetic tweezers that enables us to maneuver small magnetic probes inside living cells. So far, magnetic tweezers can be divided into two categories: I), tweezers that allow the exertion of high forces but consist of only one or two poles and therefore are capable of only exerting forces in one direction; and II), tweezers that consist of multiple poles and allow exertion of forces in multiple directions but at very low forces. The magnetic tweezers described here combines both aspects in a single apparatus: high forces in a controllable direction. To this end, micron scale magnetic structures are fabricated using cleanroom technologies. With these tweezers, magnetic flux gradients of nablaB = 8 x 103 T m-1 can be achieved over the dimensions of a single cell. This allows exertion of forces up to 12 pN on paramagnetic probes with a diameter of 350 nm, enabling us to maneuver them through the cytoplasm of a living cell. It is expected that with the current tweezers, picoNewton forces can be exerted on beads as small as 100 nm. 10.1529/biophysj.104.052035 Micro Magnetic Tweezers for Nanomanipulation Inside Live Cells Anthony de Vries Bea Krenn Roel van Driel Johannes Kanger doi:10.1529/biophysj.104.052035 Biophys. J., Vol. 88, No. 3. (1 March 2005), pp. 2137-2144. 2008-01-28T01:37:31-00:00 2005 Biophys. J. 88 3 2137 2144 cells intracellular magnetic trap tweezers http://www.citeulike.org/user/rodney/article/1445059 <i>Physical Review, Vol. 61, No. 9-10. (1 May 1942), 631.</i><br /><br />Observations on the change of light transmission through magnetite suspensions under the influence of alternating magnetic fields show that the orientation of the particles is not exclusively of dipolar origin; as was assumed by Heaps and Elmore. Fields of frequencies between 500 and 15;000 cycles per sec. produce a steady change of absorption. In fields of lower frequencies ω the change consists of a steady and a fluctuating part. The wave form of the latter is studied with a photo-cell amplifier and an oscillograph. In general; it is given by an equation of the form: A cosω t + B cos2ω t . By varying the field intensity; the frequency or the viscosity; either A or B can be made to vanish. This behavior is shown to be characteristic of polar anisotropic particles; for which the torque on the induced dipole is of the same order of magnitude as that due to the permanent dipole. Included is a survey of the work done on the magneto- and electro-optical properties of numerous other colloids and suspensions. Magneto-Optical Properties of Ferromagnetic Suspensions Hans Mueller Morris Shamos doi:10.1103/PhysRev.61.631 Physical Review, Vol. 61, No. 9-10. (1 May 1942), 631. 2007-07-09T23:16:38-00:00 1942 Physical Review 61 9-10 631 American Physical Society dipole ferromagnetic induced magnetic optical permanent http://www.citeulike.org/user/rodney/article/1881924 <i>Reports on Progress in Physics, Vol. 30, No. 2. (1967), pp. 615-730.</i><br /><br />The theory of critical phenomena in systems at equilibrium is reviewed at an introductory level with special emphasis on the values of the critical point exponents a, b, g,..., and their interrelations. The experimental observations are surveyed and the analogies between different physical systems - fluids, magnets, superfluids, binary alloys, etc. - are developed phenomenologically. An exact theoretical basis for the analogies follows from the equivalence between classical and quantal `lattice gases' and the Ising and Heisenberg-Ising magnetic models. General rigorous inequalities for critical exponents at and below Tc are derived. The nature and validity of the `classical' (phenomenological and mean field) theories are discussed, their predictions being contrasted with the exact results for plane Ising models, which are summarized concisely. Pade approximant and ratio techniques applied to appropriate series expansions lead to precise critical-point estimates for the three-dimensional Heisenberg and Ising models (tables of data are presented). With this background a critique is presented of recent theoretical ideas: namely, the `droplet' picture of the critical point and the `homogeneity' and `scaling' hypotheses. These lead to a `law of corresponding states' near a critical point and to relations between the various exponents which suggest that perhaps only two or three exponents might be algebraically independent for any system. The theory of equilibrium critical phenomena ME Fisher doi:10.1088/0034-4885/30/2/306 Reports on Progress in Physics, Vol. 30, No. 2. (1967), pp. 615-730. 2007-11-07T23:58:25-00:00 1967 Reports on Progress in Physics 30 2 615 730 capacity critical curie equilibrium ferromagnetic heat magnetic temperature http://www.citeulike.org/user/rodney/article/341577 <i>Nature, Vol. 437, No. 7060., pp. 862-865.</i> Microscopic artificial swimmers Rémi Dreyfus Jean Baudry Marcus Roper Marc Fermigier Howard Stone Jérôme Bibette doi:10.1038/nature04090 Nature, Vol. 437, No. 7060., pp. 862-865. 2005-10-05T22:35:21-00:00 Nature 0028-0836 437 7060 862 865 Nature Publishing Group colloidal dna magnetic microparticles microscopy microswimmer http://www.citeulike.org/user/rodney/article/1876148 <i>AIP Conference Proceedings, Vol. 850, No. 1. (2006), pp. 1153-1154.</i><br /><br />Chromium dioxide CrO2 nanoparticles with size below 4 nm were chemically synthesized. In contrast to the bulk compound, which undergoes a ferromagnetic transition at 390 K, SQUID data of the highly-disordered nanoparticles follow approximately a Curie-Weiss fit. The low temperature specific heat is dominated by a much larger ferromagnetic spin-wave term than that of bulk CrO2. A spin-glass-type transition occurs near 6.5 K, based on the observation of a cusp in the temperature dependence of the ac susceptibility, accompanied by a small specific heat anomaly. Magnetic and Spin-glass-like Behavior of CrO[sub 2] Nanoparticles CR Wang DS Yang YY Chen JC Ho doi:10.1063/1.2355112 AIP Conference Proceedings, Vol. 850, No. 1. (2006), pp. 1153-1154. 2007-11-07T03:34:00-00:00 2006 AIP Conference Proceedings 850 1 1153 1154 AIP chromium cro2 dioxide ferromagnetic magnetic nanoparticles http://www.citeulike.org/user/rodney/article/1342737 <i>Journal of Applied Physics, Vol. 93, No. 10. (2003), pp. 6698-6700.</i><br /><br />Aspherical magnetic particles orient in a magnetic field due to magnetic shape anisotropy. They also emit different fluxes of light from their different geometric faces due to self-absorption and total internal reflection within the particles. The particles rotate in response to rotating magnetic fields and appear to blink as they rotate. We have made pancake and chain shaped particles and magnetically modulated their fluorescent intensities. Demodulating the signal extracts the probe fluorescence from electronic and optical backgrounds dramatically increasing signal to noise ratios. The probes have applications in sensitive and rapid immunoassays, improved intracellular sensors, and inexpensive single molecule analysis. Aspherical magnetically modulated optical nanoprobes (MagMOONs) Jeffrey Anker Caleb Behrend Raoul Kopelman doi:10.1063/1.1556926 Journal of Applied Physics, Vol. 93, No. 10. (2003), pp. 6698-6700. 2007-05-30T12:29:06-00:00 2003 Journal of Applied Physics 93 10 6698 6700 AIP aspherical magnetic http://www.citeulike.org/user/rodney/article/2298082 <i>Methods Cell Biol, Vol. 83 (2007), pp. 473-493.</i><br /><br />We discuss herein the theory as well as some design considerations of magnetic tweezers. This method of generating force on magnetic particles bound to biological entities is shown to have a number of advantages over other techniques: forces are exerted in noncontact mode, they can be large in magnitude (order of 10 nanonewtons), and adjustable in direction, static or oscillatory. One apparatus built in our laboratory is described in detail, along with examples of experimental applications and results. Magnetic tweezers in cell biology. M Tanase N Biais M Sheetz doi:10.1016/S0091-679X(07)83020-2 Methods Cell Biol, Vol. 83 (2007), pp. 473-493. 2008-01-28T15:14:33-00:00 2007 Methods Cell Biol 0091-679X 83 473 493 cells magnetic review tweezers http://www.citeulike.org/user/rodney/article/1875884 <i>Macromolecular Materials and Engineering, Vol. 289, No. 4. (2004), pp. 341-348.</i><br /><br />Summary: A magnetite-based colloid was obtained by chemical co-precipitation of iron(II) and iron(III) salts in alkaline medium and stabilized with oleic acid. Magnetic micron-size poly(2-hydroxyethyl methacrylate) (PHEMA)-based latex particles of narrow size distribution were prepared by dispersion polymerization in toluene/2-methylpropan-1-ol in the presence of three kinds of ferrimagnetic nanoparticles: chromium dioxide, maghemite, and magnetite. Cellulose acetate butyrate and dibenzoyl peroxide were used as the stabilizer and the initiator, respectively. The magnetic characteristics were examined with respect to behavior in the magnetic field and thermal stability. Our results show that chromium dioxide and derived PHEMA particles are magnetically stable in moderate temperatures up to about 100 °C. Maghemite particles are thermally stable up to 500 °C. Measurements of the hysteresis loops and remanent magnetization showed that embedment of magnetic particles in organic polymer has practically no effect on their magnetic hysteresis. All the samples reached magnetic saturation in fields below 0.3 T (saturation of magnetite). Regarding separation by the magnetic field, ultrafine, superparamagnetic magnetite particles show the best performance because of their magnetic susceptibility, the highest measured here, and the absence of coercive force.co Magnetic Characteristics of Ferrimagnetic Microspheres Prepared by Dispersion Polymerization Daniel Horák František Lednický Eduard Petrovský Aleš Kapička doi:10.1002/mame.200300271 Macromolecular Materials and Engineering, Vol. 289, No. 4. (2004), pp. 341-348. 2007-11-07T01:36:10-00:00 2004 Macromolecular Materials and Engineering 289 4 341 348 chromium cro2 dioxide dispersion ferromagnetic magnetic microspheres susceptibility http://www.citeulike.org/user/rodney/article/1444771 <i>Physical Review Letters, Vol. 51, No. 25. (19 December 1983), 2306.</i><br /><br />Holes are produced inside a thin layer of magnetic fluid with use of monodisperse polystyrene spheres with diameters in the micrometer range. With an external magnetic field an apparent magnetic dipole will be associated with each hole as a result of the displaced fluid. The apparent dipolar interactions between the spheres may be made attractive or repulsive. This Letter presents the first direct microscopic observations of the crystallization of magnetic holes forming a variety of different lattices. One- and Two-Dimensional Crystallization of Magnetic Holes AT Skjeltorp doi:10.1103/PhysRevLett.51.2306 Physical Review Letters, Vol. 51, No. 25. (19 December 1983), 2306. 2007-07-09T19:38:29-00:00 1983 Physical Review Letters 51 25 2306 American Physical Society crystallization holes magnetic http://www.citeulike.org/user/rodney/article/1871092 <i>Physical Review Letters, Vol. 89, No. 17. (4 October 2002), 177402.</i><br /><br />We have applied photoexcitation by ultrashort laser pulses to single crystal thin CrO 2 films to trigger coherent transient magnetization rotation on a subnanosecond time scale; in macroscale single domains. Moreover; by applying the photoexcitation by pairs of temporally separated pump pulses; the transient precession of the magnetization can be phase controlled; depending on the time separation between the pulses. The mechanism behind the photoexcitation originates from the modulation of the magnetocrystalline anisotropy by nonthermal hot electron spins. Coherent Magnetization Rotation and Phase Control by Ultrashort Optical Pulses in CrO_2 Thin Films Qiang Zhang AV Nurmikko A Anguelouch G Xiao A Gupta doi:10.1103/PhysRevLett.89.177402 Physical Review Letters, Vol. 89, No. 17. (4 October 2002), 177402. 2007-11-06T01:12:26-00:00 2002 Physical Review Letters 89 17 177402 American Physical Society cro2 ferromagnetic magnetic magnetization optical phase rotation ultrafast http://www.citeulike.org/user/rodney/article/1871086 <i>Physica Status Solidi Applied Research, Vol. 202 (January 2005), pp. 144-150.</i><br /><br />Resistivity of cold-pressed CrO2 powder has been measured over the temperature range of 2 to 350 K with a magnetic field up of to 50 kOe. High resolution transmission electron microscopy (HRTEM) images show that the CrO2 particles are needle-shaped with an aspect ratio of 7:1 and have an average length of 200 nm, and are covered with an ultra-thin (2.5 nm) native Cr2O3 layer. Temperature dependent conductivity can be well described by the expression below 55 K, a feature of electron tunneling, and by the higher-order hopping for temperature above 55 K. The magnetoresistance, , reaches 33.5% at 2 K and decreases to nearly zero at room temperature. Temperature dependent saturation magnetization follows well the relation below 240 K. The spin-wave stiffness constant, D, is estimated to be 91 meV Å2. By fitting the specific heat measured in the temperature range of 1.8-34 K by the relation , we obtained the electronic specific heat coefficient = 1.7 mJ/mol K2, this corresponds to a density of states at the Fermi level of 0.73 states/eV, which is in good accordance with the theoretical value of 0.69 states/eV. Transport and magnetotransport properties of cold-pressed CrO2 powder H Liu RK Zheng Y Wang HL Bai XX Zhang Physica Status Solidi Applied Research, Vol. 202 (January 2005), pp. 144-150. 2007-11-06T01:09:43-00:00 2005 Physica Status Solidi Applied Research 202 144 150 cro2 ferromagnetic magnetic powder http://www.citeulike.org/user/rodney/article/2020118 <i>Applied Physics Letters, Vol. 91, No. 22. (2007), pp. 224105-224105-3.</i><br /><br />  Single bacterial cell detection with nonlinear rotational frequency shifts of driven magnetic microspheres Brandon Mcnaughton Rodney Agayan Roy Clarke Ron Smith Raoul Kopelman Applied Physics Letters, Vol. 91, No. 22. (2007), pp. 224105-224105-3. 2007-11-29T23:06:00-00:00 2007 Applied Physics Letters 91 22 224105 224105-3 AIP bacteria cell citedby detection magnetic microspheres nonlinear nonuniform rotational single http://www.citeulike.org/user/rodney/article/1397899 <i>Opt. Lett., Vol. 26, No. 17. (2001), pp. 1359-1361.</i><br /><br />A magneto-optic trap for micro-objects is described. Magnetic beads were trapped by optical tweezers while being rotated by a new integrated magnetic manipulator. Rotation was achieved with eight electromagnets with tip-pole geometry. The time orbital potential technique was used to achieve rotation of magnetic beads. Trapping in three dimensions and rotation of magnetic beads on three axes are demonstrated with forces up to 230 pN and force momenta of up to 10 16 N m. A position-detection apparatus based on an interferometric scheme provides nanometer sensitivities in a few milliseconds. © 2001 Optical Society of America. Three-dimensional magneto-optic trap for micro-object manipulation L Sacconi G Romano R Ballerini M Capitanio M De Pas M Giuntini D Dunlap L Finzi FS Pavone Opt. Lett., Vol. 26, No. 17. (2001), pp. 1359-1361. 2007-06-19T01:42:04-00:00 2001 Opt. Lett. 26 17 1359 1361 3-d magnetic manipulation microparticles optical trap tweezers http://www.citeulike.org/user/rodney/article/1397898 <i>Physical Review A (Atomic, Molecular, and Optical Physics), Vol. 70, No. 5. (2004), 053829.</i><br /><br />Laser beams exert torque on microparticles through very different physical mechanisms. In this paper, optical angular momentum transferred by laser light to a trapped absorbing superparamagnetic microsphere has been studied, distinguishing between different contributions. We have found the main contribution to the torque arising from the transfer of the spin angular momentum carried by absorbed laser light. Detailed polarization status contribution of the laser light to the momentum transfer has been then analyzed. A general method to separate and quantify contributions to the optical angular momentum transferred has been developed. We have thus quantified contributions due to radiation pressure, through an effect similar to the wind on a windmill, and contributions arising from magneto-optic effects. Spin absorption, windmill, and magneto-optic effects in optical angular momentum transfer Davide Normanno Marco Capitanio Francesco Pavone doi:10.1103/PhysRevA.70.053829 Physical Review A (Atomic, Molecular, and Optical Physics), Vol. 70, No. 5. (2004), 053829. 2007-06-19T01:35:13-00:00 2004 Physical Review A (Atomic, Molecular, and Optical Physics) 70 5 053829 APS absorption angular magnetic momentum optical rotation spin torque windmill http://www.citeulike.org/user/rodney/article/2954890 <i>Applied Physics Letters, Vol. 92, No. 23. (2008)</i> Magnetostatic interactions between carbon nanotubes filled with magnetic nanoparticles Konstantin Kornev Derek Halverson Guzeliya Korneva Yury Gogotsi Gary Friedman Applied Physics Letters, Vol. 92, No. 23. (2008) 2008-07-03T03:28:32-00:00 2008 Applied Physics Letters 92 23 AIP carbon magnetic magnetostatic nanoparticles nanotubes http://www.citeulike.org/user/rodney/article/1719883 <i>Journal of Applied Physics, Vol. 102, No. 5. (2007)</i><br /><br />Properties of magnetic nanoparticles in the Brownian relaxation region were studied. Using the magnetic nanoparticles that exhibit remanence, we measured the magnetic properties, such as static magnetization, magnetic relaxation, and alternating current susceptibility, in a solution. Comprehensive comparisons were made between the experimental results and the theoretical ones predicted from the Brownian relaxation. From the comparison, the distributions of the particle parameters, i.e., the magnetic moment and the relaxation time, were estimated. It was shown that all the magnetic properties can be well explained when we take into account the parameter distributions in the sample. ©2007 American Institute of Physics Properties of magnetic nanoparticles in the Brownian relaxation range for liquid phase immunoassays K Enpuku T Tanaka T Matsuda F Dang N Enomoto J Hojo K Yoshinaga F Ludwig F Ghaffari E Heim M Schilling doi:10.1063/1.2775882 Journal of Applied Physics, Vol. 102, No. 5. (2007) 2007-10-02T15:13:17-00:00 2007 Journal of Applied Physics 102 5 AIP brownian immunoassays magnetic nanoparticles relaxation http://www.citeulike.org/user/rodney/article/1719828 <i>The Journal of Chemical Physics, Vol. 127, No. 10. (2007)</i><br /><br />The polymer properties of canine mucus were investigated through the method of rotating magnetic particle microrheometry. Mucus is visualized as a physically entangled biopolymer of low polydispersity in a water-based solution. Mucus was modeled according to the constitutive law of a Doi-Edwards fluid. The magnetic-particle equation of rotational motion is analytically solved in the linear viscoelastic limit rendering theoretical flow profiles which are used to fit the experimental trace signals of the particle remanent-magnetic-field decay. The zero-shear-rate viscosity was found to be 18  000  P and the relaxation time at about 42  s. The molecular weight between entanglements for mucins was estimated at 1.7  MDa rendering an estimation of about seven physical cross-links per molecule. Rheological investigations were extended also to diluted and concentrated rations of the normal mucus simulating the conditions found in more physiological extremes. ©2007 American Institute of Physics Rotating magnetic particle microrheometry in biopolymer fluid dynamics: Mucus microrheology George Besseris Donovan Yeates doi:10.1063/1.2766947 The Journal of Chemical Physics, Vol. 127, No. 10. (2007) 2007-10-02T14:56:57-00:00 2007 The Journal of Chemical Physics 127 10 AIP dynamics fluid magnetic microparticles microrheology mucus rheology rheometry rotation http://www.citeulike.org/user/rodney/article/2364205 <i>Journal of Applied Physics, Vol. 100, No. 6. (2006)</i><br /><br />  The effect of the in-plane demagnetizing field on films with weak perpendicular magnetic anisotropy Oscar de Abril Mar\ia Claudio Aroca Journal of Applied Physics, Vol. 100, No. 6. (2006) 2008-02-12T00:23:04-00:00 2006 Journal of Applied Physics 100 6 AIP anisotropy film magnetic http://www.citeulike.org/user/rodney/article/2364203 <i>Journal of Applied Physics, Vol. 102, No. 5. (2007)</i><br /><br />  Magnetophoresis of microspheres covered by magnetic nanoparticles X Zhao LE Helseth Journal of Applied Physics, Vol. 102, No. 5. (2007) 2008-02-12T00:21:04-00:00 2007 Journal of Applied Physics 102 5 AIP magnetic magnetophoresis microspheres nanoparticles http://www.citeulike.org/user/rodney/article/1719786 <i>Proceedings of the National Academy of Sciences, Vol. 104, No. 37. (11 September 2007), pp. 14553-14558.</i><br /><br />Cells respond to mechanical forces whether applied externally or generated internally via the cytoskeleton. To study the cellular response to forces separately, we applied external forces to cells via microfabricated magnetic posts containing cobalt nanowires interspersed among an array of elastomeric posts, which acted as independent sensors to cellular traction forces. A magnetic field induced torque in the nanowires, which deflected the magnetic posts and imparted force to individual adhesions of cells attached to the array. Using this system, we examined the cellular reaction to applied forces and found that applying a step force led to an increase in local focal adhesion size at the site of application but not at nearby nonmagnetic posts. Focal adhesion recruitment was enhanced further when cells were subjected to multiple force actuations within the same time interval. Recording the traction forces in response to such force stimulation revealed two responses: a sudden loss in contractility that occurred within the first minute of stimulation or a gradual decay in contractility over several minutes. For both types of responses, the subcellular distribution of loss in traction forces was not confined to locations near the actuated micropost, nor uniformly across the whole cell, but instead occurred at discrete locations along the cell periphery. Together, these data reveal an important dynamic biological relationship between external and internal forces and demonstrate the utility of this microfabricated system to explore this interaction. 10.1073/pnas.0611613104 From the Cover: Magnetic microposts as an approach to apply forces to living cells Nathan Sniadecki Alexandre Anguelouch Michael Yang Corinne Lamb Zhijun Liu Stuart Kirschner Yaohua Liu Daniel Reich Christopher Chen doi:10.1073/pnas.0611613104 Proceedings of the National Academy of Sciences, Vol. 104, No. 37. (11 September 2007), pp. 14553-14558. 2007-10-02T14:44:23-00:00 2007 Proceedings of the National Academy of Sciences 104 37 14553 14558 cells fabrication forces magnetic micron posts http://www.citeulike.org/user/rodney/article/1145139 <i>Sens Actuators, B Chem, Vol. 121, No. 1. (2007), pp. 330-340.</i><br /><br />Recently, the nonlinear rotation of single magnetic particles has emerged as a tool to measure physical parameters on the micro-scale. In this paper, detailed theoretical analyses are carried out for tailored microprobes that measure (1) local magnetic fields, (2) magnetic particle characteristics, (3) viscosity and (4) chemical binding, along with their corresponding experimental demonstrations. Such new physical measurement methods, using single micro- or nano-particles, in combination with previous chemical nanoparticle sensing methods, lead to a new class of physiochemical micro- and nano-particle sensors that may be of significant biomedical and technological interest. © 2006 Elsevier B.V. All rights reserved. Physiochemical microparticle sensors based on nonlinear magnetic oscillations BH Mcnaughton RR Agayan JX Wang R Kopelman doi:10.1016/j.snb.2006.09.043 Sens Actuators, B Chem, Vol. 121, No. 1. (2007), pp. 330-340. 2007-03-07T04:55:40-00:00 2007 Sens Actuators, B Chem 121 1 330 340 magnetic microparticles nonlinear nonuniform rotation sensors http://www.citeulike.org/user/rodney/article/1614928 <i>Biophys. J., Vol. 58, No. 2. (1 August 1990), pp. 357-362.</i><br /><br />Spherical supported vesicles (SSVs), a new model system consisting of single dimyristoyl phosphatidylcholine (DMPC) bilayers adsorbed to spherical glass beads with a narrow size distribution, were prepared at two different sizes (0.5 and 1.5 microns) and their physical properties were studied by deuterium nuclear magnetic resonance (2H-NMR). Such SSV samples can be prepared at any desired size between 0.3 and 10 microns. The 2H-NMR measurements provide evidence for a strong dependence of the spectra and the transverse relaxation times on the curvature of the SSVs in a diameter range between 0.5 and 1.5 microns. For larger SSVs (1.5 microns diameter) their powder spectra and their calculated oriented spectra are similar to those obtained for multilamellar dispersions of DMPC-d54. The lineshape of the smaller SSVs exhibits a temperature dependence which is not found in multilamellar samples. The SSVs are stable in the liquid crystalline phase over days but irreversibly change to multilamellar vesicles in the gel state. The average thickness of the water layer between the single bilayer and the glass bead surface was estimated by 1H-NMR to e 17 +/- 5 A. Physical properties of single phospholipid bilayers adsorbed to micro glass beads. A new vesicular model system studied by 2H-nuclear magnetic resonance. TM Bayerl M Bloom Biophys. J., Vol. 58, No. 2. (1 August 1990), pp. 357-362. 2007-09-03T01:59:21-00:00 1990 Biophys. J. 58 2 357 362 adsorption beads bilayers glass magnetic membranes microparticles nmr nuclear phospholipid resonance vesicles http://www.citeulike.org/user/rodney/article/1552432 <i>Czechoslovak Journal of Physics, Vol. 43, No. 6. (1 June 1993), pp. 671-681.</i><br /><br />The motion of a pair of uniform interacting spherical mesoscopic particles situated in a viscous fluid under the influence of a rotating magnetic field was studied. The coupling interactions between the particles were chosen as a superposition of steric and dipolar pair potentials (for the dipoles parallel to the external field). The model dynamics consisting of particular rotation and vibration modes is the result of the interplay of viscous and interaction forces. The transition from the synchronous to the asynchronous regime of dimer rotation has been found. The results were discussed from a synergetic point of view. A qualitative picture of behaviour of the effective magnetoviscosity and permittivity for dimerized magnetorheological suspension has been given. Magnetic dimer motion effects in a rotating magnetic field (A qualitative model of magnetoviscosity and permittivity in magnetorheological suspensions) D Horváth P Kopčanský doi:10.1007/BF01591541 Czechoslovak Journal of Physics, Vol. 43, No. 6. (1 June 1993), pp. 671-681. 2007-08-10T18:46:45-00:00 1993 Czechoslovak Journal of Physics 43 6 671 681 dimer magnetic model permittivity rheology rotation viscosity http://www.citeulike.org/user/rodney/article/2138073 <i>Journal of Magnetism and Magnetic Materials, Vol. 311, No. 1. (April 2007), pp. 145-149.</i><br /><br />A procedure is presented to determine the permanent magnetic dipole moment of composite microspheres containing magnetic nanoparticles with a blocked magnetic dipole moment. The composite particles are dispersed in a solvent, and the complex magnetic susceptibility is measured from 0.1 to 1000 Hz using a highly sensitive new setup. Composite particles with a permanent magnetic dipole moment are revealed by a characteristic frequency that corresponds to the Brownian rotation of the microspheres. From measured susceptibility spectra, we calculate the permanent magnetic dipole moment of recently developed cobalt ferrite-doped silica and latex microspheres. Low-frequency complex magnetic susceptibility of magnetic composite microspheres in colloidal dispersion Ben Erne Maria Claesson Stefano Sacanna Mark Klokkenburg Emile Bakelaar Bonny Kuipers doi:10.1016/j.jmmm.2006.11.169 Journal of Magnetism and Magnetic Materials, Vol. 311, No. 1. (April 2007), pp. 145-149. 2007-12-17T20:04:43-00:00 2007 Journal of Magnetism and Magnetic Materials 311 1 145 149 colloidal composites hybrid magnetic microspheres silica susceptibility http://www.citeulike.org/user/rodney/article/2793283 <i>Small (Weinheim an der Bergstrasse, Germany), Vol. 4, No. 2. (February 2008), pp. 218-224.</i><br /><br />Highly uniform Fe3O4/SiO2 core/shell nanoparticles functionalized by phosphorescent iridium complexes (Ir) have been strategically designed and synthesized. The Fe3O4/SiO2(Ir) nanocomposite demonstrates its versatility in various applications: the magnetic core provides the capability for magnetic resonance imaging and the great enhancement of the spin-orbit coupling in the iridium complex makes it well suited for phosphorescent labeling and simultaneous singlet oxygen generation to induce apoptosis. Iridium-complex-functionalized Fe3O4/SiO2 core/shell nanoparticles: a facile three-in-one system in magnetic resonance imaging, luminescence imaging, and photodynamic therapy. CW Lai YH Wang CH Lai MJ Yang CY Chen PT Chou CS Chan Y Chi YC Chen JK Hsiao doi:10.1002/smll.200700283 Small (Weinheim an der Bergstrasse, Germany), Vol. 4, No. 2. (February 2008), pp. 218-224. 2008-05-13T03:52:32-00:00 2008 Small (Weinheim an der Bergstrasse, Germany) 1613-6829 4 2 218 224 citedby core-shell imaging iridium luminescence magnetic mri nanoparticles pdt photodynamic resonance therapy http://www.citeulike.org/user/rodney/article/2190397 <i>Physical Review E, Vol. 69, No. 4. (30 April 2004), 041406.</i><br /><br />Paramagnetic particles have the unique ability to reversibly form magnetic chains. We have taken advantage of this property by permanently linking the chains with three linking chemistries to create flexible chains whose behavior changes with the application of a magnetic field. We study the behavior of these chains in a rotating magnetic field and model them as elastic rods. Rigid chains rotate as a solid body while flexible chains deform under the influence of magnetic; viscous; and elastic stresses. We find that the shapes chains assume in rotating magnetic fields confirm the chain flexibility determined from previous micromechanics measurements. Rotational dynamics of semiflexible paramagnetic particle chains Sibani Biswal Alice Gast doi:10.1103/PhysRevE.69.041406 Physical Review E, Vol. 69, No. 4. (30 April 2004), 041406. 2008-01-03T01:45:36-00:00 2004 Physical Review E 69 4 041406 American Physical Society chains dynamics magnetic nonuniform paramagnetic rotational semiflexible http://www.citeulike.org/user/rodney/article/1144960 <i>Phys. Rev. E Stat. Nonlinear Soft Matter Phys., Vol. 69, No. 5 1. (2004)</i><br /><br />The use of Mie theory for electromagnetic scattering by a magnetic sphere of arbitrary size and with gyromagnetic permeability tensor was discussed. A set of vector basis functions were constructed for the magnetic induction inside the particles, which were the solution for the wave equation for magnetic induction and extended terms of the usual vector spherical wave functions (VSWF) with different values of wave vector. The relationship between wave vector and the frequency was obtained as the eigenvalues of an eigensystem determined by the permeability tensor. It was observed that the Mie-types formulation for EM scattering with anisotropic permeability serves as the building block for the multiple scattering problems. Art. No.: 056614 Electromagnetic scattering by optically anisotropic magnetic particle Z Lin ST Chui Phys. Rev. E Stat. Nonlinear Soft Matter Phys., Vol. 69, No. 5 1. (2004) 2007-03-07T01:57:43-00:00 2004 Phys. Rev. E Stat. Nonlinear Soft Matter Phys. 69 5 1 anisotropy aspherical magnetic optical scattering http://www.citeulike.org/user/rodney/article/1397650 <i>Opt Commun, Vol. 215, No. 4-6. (2003), pp. 323-331.</i><br /><br />Characterization of optical trapping with laser tweezers of super-paramagnetic beads has been performed for the first time. In particular, we have compared the force action in optical trapping on super-paramagnetic beads with respect to the polystyrene ones. Using a novel magneto-optical manipulator we have developed a direct rotation detection scheme for trapped beads characterized by a high sensitivity and fast time response. Finally a calibration procedure able to directly measure an applied external torque on the trapped bead is shown. This demonstrates the capability of this apparatus to perform direct torque measurement (torsional rigidity) on a single bio-molecule attached to a super-paramagnetic bead. © 2002 Elsevier Science B.V. All rights reserved. Force and torque measurements using magnetic micro beads for single molecule biophysics G Romano L Sacconi M Capitanio FS Pavone doi:http://dx.doi.org/10.1016/S0030-4018(02)02247-2 Opt Commun, Vol. 215, No. 4-6. (2003), pp. 323-331. 2007-06-18T22:36:12-00:00 2003 Opt Commun 215 4-6 323 331 beads forces magnetic microparticles optical single-molecule torque http://www.citeulike.org/user/rodney/article/1870627 <i>physica status solidi (a), Vol. 204, No. 3. (2007), pp. 755-762.</i><br /><br />Rod-shaped CrO2 nanoparticles with an aspect ratio of around 8:1 were studied in this work. The high-frequency properties (complex magnetic permeability, electric permittivity and reflection coefficient) have been measured on a composite consisting of 20 vol% of rod-shaped CrO2 nanoparticles in a non-magnetic epoxy resin matrix. The intrinsic magnetic permeability was calculated using an analytical model derived from the Landau-Lifshitz-Gilbert (LLG) equation. The effective permeability of the composite consisting of rod-shaped CrO2 particles embedded in a nonmagnetic matrix (epoxy resin) was calculated using an effective medium theory for randomly orientated ellipsoidal inclusions. The comparison of the experimental values of the effective permeability with the analytical calculation showed that a relatively good agreement was obtained when the interparticle interactions were taken into the consideration. The results showed that CrO2 have a natural resonance frequency at around 8 GHz. The microwave absorbing properties of the composite of rod-shaped CrO2 nanoparticles and epoxy resin were studied. The calculated results of reflection coefficient indicated that the rod-shaped CrO2 nanoparticles may be interesting for microwave absorption, particularly for the high frequency range around 10 GHz (X-band). (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) Studies of high-frequency magnetic permeability of rod-shaped CrO<SUB><FONT SIZE='-1'>2</FONT></SUB> nanoparticles LZ Wu J Ding CP Neo LF Chen CK Ong doi:10.1002/pssa.200622015 physica status solidi (a), Vol. 204, No. 3. (2007), pp. 755-762. 2007-11-06T00:11:28-00:00 2007 physica status solidi (a) 204 3 755 762 chromium cro2 dioxide ferromagnetic magnetic nanoparticles permeability http://www.citeulike.org/user/rodney/article/1901535 <i>Vol. 85, No. 8. (1999), pp. 5576-5581.</i> Powder magnetoresistance (invited) JMD Coey Vol. 85, No. 8. (1999), pp. 5576-5581. 2007-11-12T07:04:56-00:00 1999 85 8 5576 5581 AIP cro2 ferromagnetic magnetic powder