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Sample records for molecular magnets composed

  1. Permanent magnets composed of high temperature superconductors

    NASA Technical Reports Server (NTRS)

    Weinstein, Roy; Chen, In-Gann; Liu, Jay; Lau, Kwong

    1991-01-01

    A study of persistent, trapped magnetic field has been pursued with high-temperature superconducting (HTS) materials. The main effort is to study the feasibility of utilization of HTS to fabricate magnets for various devices. The trapped field, when not in saturation, is proportional to the applied field. Thus, it should be possible to replicate complicated field configurations with melt-textured YBa2Cu3O7 (MT-Y123) material, bypassing the need for HTS wires. Presently, materials have been developed from which magnets of 1.5 T, at 77 K, can be fabricated. Much higher field is available at lower operating temperature. Stability of a few percent per year is readily attainable. Results of studies on prototype motors and minimagnets are reported.

  2. Designing magnetic superlattices that are composed of single domain nanomagnets

    PubMed Central

    Kusmartsev, Feodor V; Kovács, Endre

    2014-01-01

    Summary Background: The complex nature of the magnetic interactions between any number of nanosized elements of a magnetic superlattice can be described by the generic behavior that is presented here. The hysteresis characteristics of interacting elliptical nanomagnets are described by a quasi-static method that identifies the critical boundaries between magnetic phases. A full dynamical analysis is conducted in complement to this and the deviations from the quasi-static analysis are highlighted. Each phase is defined by the configuration of the magnetic moments of the chain of single domain nanomagnets and correspondingly the existence of parallel, anti-parallel and canting average magnetization states. Results: We give examples of the phase diagrams in terms of anisotropy and coupling strength for two, three and four magnetic layers. Each phase diagrams character is defined by the shape of the magnetic hysteresis profile for a system in an applied magnetic field. We present the analytical solutions that enable one to define the “phase” boundaries between the emergence of spin-flop, anti-parallel and parallel configurations. The shape of the hysteresis profile is a function of the coupling strength between the nanomagnets and examples are given of how it dictates a systems magnetic response. Many different paths between metastable states can exist and this can lead to instabilities and fluctuations in the magnetization. Conclusion: With these phase diagrams one can find the most stable magnetic configurations against perturbations so as to create magnetic devices. On the other hand, one may require a magnetic system that can easily be switched between phases, and so one can use the information herein to design superlattices of the required shape and character by choosing parameters close to the phase boundaries. This work will be useful when designing future spintronic devices, especially those manipulating the properties of CoFeB compounds. PMID:25161831

  3. Photonic crystals composed of virtual pillars with magnetic walls: Photonic band gaps and double Dirac cones

    NASA Astrophysics Data System (ADS)

    Kim, Seong-Han; Kim, Soeun; Kee, Chul-Sik

    2016-08-01

    Photonic crystals composed of virtual pillars with magnetic walls are proposed. A virtual pillar with a magnetic wall can be created inside a parallel perfect electric conductor plate waveguide by introducing a circular perfect magnetic conductor patch in the upper perfect electric conductor plate of the waveguide. The virtual pillar mimics a perfect magnetic conductor pillar with a radius less than that of the circular patch because electromagnetic waves can slightly penetrate the wall. Furthermore, the photonic band structures of a triangular photonic crystal composed of virtual pillars for the transverse electromagnetic modes of the waveguide are investigated. They are very similar to those of a triangular photonic crystal composed of infinitely long perfect electric conductor cylinders for transverse magnetic modes. The similarity between the two different photonic crystals is well understood by the boundary conditions of perfect electric and magnetic conductor surfaces. A double Dirac cone at the center of the Brillouin zone is observed and thus the virtual pillar triangular photonic crystal can act a zero-refractive-index material at the Dirac point frequency.

  4. Magnetic properties of bimetallic clusters composed of Gd and transition metals

    NASA Astrophysics Data System (ADS)

    Mukherjee, Prajna; Gupta, Bikash C.; Jena, Puru

    2016-02-01

    Gadolinium, a rare earth metal, is ferromagnetic, while Mn, a transition metal atom, is antiferromagnetic in the bulk phase. Clusters of these elements, however, share some common properties; both exhibit ferrimagnetic behavior and maintain magnetic moments close to their free atomic value. Using density functional theory and generalized gradient approximation for exchange and correlation, we have studied the magnetic properties of bimetallic clusters composed of Gd and Mn to see if they show unusual behavior. The coupling between Gd and Mn spins is found to be antiferromagnetic, while that between Mn atoms is ferromagnetic. Moreover, the bonding between Gd and Mn atoms is stronger than that between the Gd atoms or Mn atoms, thus enabling the possibility of creating more stable magnetic particles. A systematic study of the magnetic and binding properties of clusters composed of Gd atom and other transition metal atoms such as V, Sc, Ti, Cr, Fe, and Co is also carried out to probe the effect of 3d-orbital occupation on magnetic coupling.

  5. Conductance of a single flexible molecular wire composed of alternating donor and acceptor units

    PubMed Central

    Nacci, Christophe; Ample, Francisco; Bleger, David; Hecht, Stefan; Joachim, Christian; Grill, Leonhard

    2015-01-01

    Molecular-scale electronics is mainly concerned by understanding charge transport through individual molecules. A key issue here is the charge transport capability through a single—typically linear—molecule, characterized by the current decay with increasing length. To improve the conductance of individual polymers, molecular design often either involves the use of rigid ribbon/ladder-type structures, thereby sacrificing for flexibility of the molecular wire, or a zero band gap, typically associated with chemical instability. Here we show that a conjugated polymer composed of alternating donor and acceptor repeat units, synthesized directly by an on-surface polymerization, exhibits a very high conductance while maintaining both its flexible structure and a finite band gap. Importantly, electronic delocalization along the wire does not seem to be necessary as proven by spatial mapping of the electronic states along individual molecular wires. Our approach should facilitate the realization of flexible ‘soft' molecular-scale circuitry, for example, on bendable substrates. PMID:26145188

  6. An invitation to molecular magnetism.

    PubMed

    Pinkowicz, Dawid; Chorazy, Szymon; Stefańczyk, Olaf

    2011-01-01

    Molecular magnetism is a new and extremely fascinating field on the borders of chemistry, physics and materials science. The design and synthesis of molecule-based magnets requires the chemist to exert considerable control over the molecules to arrange them appropriately. It also demands the development of new theories to explain the complex magneto-structural behaviour of these intriguing solids. Molecular magnetism is still at a very early stage of development. The main challenge is to increase the strength of the magnetic interactions between spin carriers so the resulting materials can be usable at room temperature. However molecular magnets exhibit true potential to become multifunctional materials. They show some considerable advantages over conventional magnets: optical transparency, chemical sensitivity and low weight to name just a few. The following article is not a complete review of the field. Its aim is rather to show how beautiful and versatile magnetic molecular solids can be, and to encourage the in-depth study of the subject. PMID:21805910

  7. Characteristic Examination of New Synchronous Motor that Composes Craw Teeth of Soft Magnetic Composite

    NASA Astrophysics Data System (ADS)

    Enomoto, Yuji; Ito, Motoya; Masaki, Ryozo; Asaka, Kazuo

    We examined the claw type teeth motor as one application of the soft magnetic composite to a motor core. In order to understand quantitatively the characteristics of the claw type teeth motor, we used the 3-dimensional electromagnetic field analysis to predict its characteristics in advance and manufactured a trial motor to estimate it. And we examined the advantages of the claw type teeth motor comparing with a conventional slot type motor. The results are: 1. By using the 3-dimensional electromagnetic field analysis, it is able to estimate with high accuracy the characteristics of the 3-phase permanent magnet synchronous claw type teeth motor having a core composed of the soft magnetic composite. 2. The claw type teeth motor is able to achieve about 20% higher output than a conventional slot type motor having an electromagnetic steel core, while both volumes are equal. 3. The motor efficiency of the claw type teeth motor is about 3.5% higher than the conventional motor.

  8. Metallic, magnetic and molecular nanocontacts.

    PubMed

    Requist, Ryan; Baruselli, Pier Paolo; Smogunov, Alexander; Fabrizio, Michele; Modesti, Silvio; Tosatti, Erio

    2016-06-01

    Scanning tunnelling microscopy and break-junction experiments realize metallic and molecular nanocontacts that act as ideal one-dimensional channels between macroscopic electrodes. Emergent nanoscale phenomena typical of these systems encompass structural, mechanical, electronic, transport, and magnetic properties. This Review focuses on the theoretical explanation of some of these properties obtained with the help of first-principles methods. By tracing parallel theoretical and experimental developments from the discovery of nanowire formation and conductance quantization in gold nanowires to recent observations of emergent magnetism and Kondo correlations, we exemplify the main concepts and ingredients needed to bring together ab initio calculations and physical observations. It can be anticipated that diode, sensor, spin-valve and spin-filter functionalities relevant for spintronics and molecular electronics applications will benefit from the physical understanding thus obtained. PMID:27272139

  9. Metallic, magnetic and molecular nanocontacts

    NASA Astrophysics Data System (ADS)

    Requist, Ryan; Baruselli, Pier Paolo; Smogunov, Alexander; Fabrizio, Michele; Modesti, Silvio; Tosatti, Erio

    2016-06-01

    Scanning tunnelling microscopy and break-junction experiments realize metallic and molecular nanocontacts that act as ideal one-dimensional channels between macroscopic electrodes. Emergent nanoscale phenomena typical of these systems encompass structural, mechanical, electronic, transport, and magnetic properties. This Review focuses on the theoretical explanation of some of these properties obtained with the help of first-principles methods. By tracing parallel theoretical and experimental developments from the discovery of nanowire formation and conductance quantization in gold nanowires to recent observations of emergent magnetism and Kondo correlations, we exemplify the main concepts and ingredients needed to bring together ab initio calculations and physical observations. It can be anticipated that diode, sensor, spin-valve and spin-filter functionalities relevant for spintronics and molecular electronics applications will benefit from the physical understanding thus obtained.

  10. Multiscale Modeling of Molecular Magnets

    SciTech Connect

    Ramasesha, S.; Raghunathan, Rajamani

    2007-11-29

    Here, we present an overview of methods of modeling Molecular Magnets in different length scales. First, we discuss a microscopic model to understand the nature of superexchange interaction in binuclear transition metal complexes of different geometry viz. A-B, A-B-A, B-A-B, linear A-B-A-B, and cyclic A-B-A-B systems. We obtain the quantum phase diagrams along various planes in the parameter space and identify the various model parameters which control the nature of superexchange in these systems. We also obtain contours of effective superexchange constants. In the next section we discuss the method of full symmetry adaptation in Valence Bond method to obtain the low-lying eigenstates of the Heisenberg spin Hamiltonian of large systems. The third part of this article deals with the calculation of the magnetic anisotropy parameters (D{sub M} and E{sub M}) of Single Molecule Magnets (SMMs). We use the single ion anisotropy values to obtain D{sub M} and E{sub M} values of the SMM, using a perturbative approach. We first solve the unperturbed Hamiltonian which is a simple spin Heisenberg Hamiltonian. Then we introduce the perturbing term H{sub 1} consisting of the single ion anisotropy. We then solve for the molecular anisotropy parameters by equating two different ways for computing the matrix elements of the perturbation term, from knowledge of the spin-spin correlation functions and the direction of orientation of the single ion anisotropies.

  11. Molecular model of biaxial ordering in nematic liquid crystals composed of flat molecules with four mesogenic groups

    NASA Astrophysics Data System (ADS)

    Gorkunov, M. V.; Osipov, M. A.; Kocot, A.; Vij, J. K.

    2010-06-01

    Relative stability of uniaxial and biaxial nematic phases is analyzed in a model nematic liquid crystal composed of flat molecules of C2h symmetry with four mesogenic groups rigidly linked to the same center. The generalized effective quadrupole mean-field potential is proposed and its constants are evaluated numerically for the pair intermolecular potential based on Gay-Berne interaction between mesogenic groups. The dependencies of the constants on molecular shape parameters are systematically analyzed. Order parameters of the uniaxial and biaxial nematic phases are evaluated by direct minimization of the free energy at different temperatures. The corresponding phase diagrams are obtained enabling one to study the effects of molecular model parameters on the stability regions of uniaxial and biaxial phases. The results are used to clarify the nature of experimentally observed biaxial ordering in nematic liquid crystals composed of tetrapode molecules with the same symmetry.

  12. Molecular model of biaxial ordering in nematic liquid crystals composed of flat molecules with four mesogenic groups.

    PubMed

    Gorkunov, M V; Osipov, M A; Kocot, A; Vij, J K

    2010-06-01

    Relative stability of uniaxial and biaxial nematic phases is analyzed in a model nematic liquid crystal composed of flat molecules of C2h symmetry with four mesogenic groups rigidly linked to the same center. The generalized effective quadrupole mean-field potential is proposed and its constants are evaluated numerically for the pair intermolecular potential based on Gay-Berne interaction between mesogenic groups. The dependencies of the constants on molecular shape parameters are systematically analyzed. Order parameters of the uniaxial and biaxial nematic phases are evaluated by direct minimization of the free energy at different temperatures. The corresponding phase diagrams are obtained enabling one to study the effects of molecular model parameters on the stability regions of uniaxial and biaxial phases. The results are used to clarify the nature of experimentally observed biaxial ordering in nematic liquid crystals composed of tetrapode molecules with the same symmetry. PMID:20866427

  13. Molecular rectifier composed of DNA with high rectification ratio enabled by intercalation

    NASA Astrophysics Data System (ADS)

    Guo, Cunlan; Wang, Kun; Zerah-Harush, Elinor; Hamill, Joseph; Wang, Bin; Dubi, Yonatan; Xu, Bingqian

    2016-05-01

    The predictability, diversity and programmability of DNA make it a leading candidate for the design of functional electronic devices that use single molecules, yet its electron transport properties have not been fully elucidated. This is primarily because of a poor understanding of how the structure of DNA determines its electron transport. Here, we demonstrate a DNA-based molecular rectifier constructed by site-specific intercalation of small molecules (coralyne) into a custom-designed 11-base-pair DNA duplex. Measured current–voltage curves of the DNA–coralyne molecular junction show unexpectedly large rectification with a rectification ratio of about 15 at 1.1 V, a counter-intuitive finding considering the seemingly symmetrical molecular structure of the junction. A non-equilibrium Green's function-based model—parameterized by density functional theory calculations—revealed that the coralyne-induced spatial asymmetry in the electron state distribution caused the observed rectification. This inherent asymmetry leads to changes in the coupling of the molecular HOMO‑1 level to the electrodes when an external voltage is applied, resulting in an asymmetric change in transmission.

  14. Molecular rectifier composed of DNA with high rectification ratio enabled by intercalation.

    PubMed

    Guo, Cunlan; Wang, Kun; Zerah-Harush, Elinor; Hamill, Joseph; Wang, Bin; Dubi, Yonatan; Xu, Bingqian

    2016-05-01

    The predictability, diversity and programmability of DNA make it a leading candidate for the design of functional electronic devices that use single molecules, yet its electron transport properties have not been fully elucidated. This is primarily because of a poor understanding of how the structure of DNA determines its electron transport. Here, we demonstrate a DNA-based molecular rectifier constructed by site-specific intercalation of small molecules (coralyne) into a custom-designed 11-base-pair DNA duplex. Measured current-voltage curves of the DNA-coralyne molecular junction show unexpectedly large rectification with a rectification ratio of about 15 at 1.1 V, a counter-intuitive finding considering the seemingly symmetrical molecular structure of the junction. A non-equilibrium Green's function-based model-parameterized by density functional theory calculations-revealed that the coralyne-induced spatial asymmetry in the electron state distribution caused the observed rectification. This inherent asymmetry leads to changes in the coupling of the molecular HOMO-1 level to the electrodes when an external voltage is applied, resulting in an asymmetric change in transmission. PMID:27102683

  15. A probe molecule composed of seventeen percent of total diffracting matter gives correct solutions in molecular replacement.

    PubMed

    Oh, B H

    1995-03-01

    It is often found in the crystallization of enzyme-inhibitor complexes that an inhibitor causes crystal packing which is different to that of native protein. This is the case for crystals of human non-pancreatic secreted phospholipase A(2) (124 residues) containing six molecules in the asymmetric unit when the protein is complexed with a potential acylamino analogue of a phospholid. The hexameric structure was determined by molecular replacement using the structure of monomeric native protein as a probe. As an extension to the experiment, it was tested whether a backbone polypeptide composed of 17% of a known monomeric structure could find its correct position on a target molecule in molecular replacement. A probe model composed of the backbone atoms of the N-terminal 77 residues of lysine-, arginine-, ornithine-binding protein (LAO, a total of 238 residues) liganded with lysine correctly finds its position on LAO liganded with histidine which crystallizes as a monomer in the asymmetric unit. The results indicate that as little as 17% of total diffracting matter can be used in molecular replacement to solve crystal structures or to obtain phase information which can be combined with phases obtained by the isomorphous-replacement method. PMID:15299314

  16. Coordination-Cluster-Based Molecular Magnetic Refrigerants.

    PubMed

    Zhang, Shaowei; Cheng, Peng

    2016-08-01

    Coordination polymers serving as molecular magnetic refrigerants have been attracting great interest. In particular, coordination cluster compounds that demonstrate their apparent advantages on cryogenic magnetic refrigerants have attracted more attention in the last five years. Herein, we mainly focus on depicting aspects of syntheses, structures, and magnetothermal properties of coordination clusters that serve as magnetic refrigerants on account of the magnetocaloric effect. The documented molecular magnetic refrigerants are classified into two primary categories according to the types of metal centers, namely, homo- and heterometallic clusters. Every section is further divided into several subgroups based on the metal nuclearity and their dimensionalities, including discrete molecular clusters and those with extended structures constructed from molecular clusters. The objective is to present a rough overview of recent progress in coordination-cluster-based molecular magnetic refrigerants and provide a tutorial for researchers who are interested in the field. PMID:27381662

  17. Core-shell composite particles composed of biodegradable polymer particles and magnetic iron oxide nanoparticles for targeted drug delivery

    NASA Astrophysics Data System (ADS)

    Oka, Chiemi; Ushimaru, Kazunori; Horiishi, Nanao; Tsuge, Takeharu; Kitamoto, Yoshitaka

    2015-05-01

    Core-shell composite particles with biodegradability and superparamagnetic behavior were prepared using a Pickering emulsion for targeted drug delivery based on magnetic guidance. The composite particles were composed of a core of biodegradable polymer and a shell of assembled magnetic iron oxide nanoparticles. It was found that the dispersibility of the nanoparticles is crucial for controlling the core-shell structure. The addition of a small amount of dispersant into the nanoparticle's suspension could improve the dispersibility and led to the formation of composite particles with a thin magnetic shell covering a polymeric core. The composite particles were also fabricated with a model drug loaded into the core, which was released via hydrolysis of the core under strong alkaline conditions. Because the core can also be biodegraded by lipase, this result suggests that the slow release of the drug from the composite particles should occur inside the body.

  18. Nature Utilizes Unusual High London Dispersion Interactions for Compact Membranes Composed of Molecular Ladders.

    PubMed

    Wagner, J Philipp; Schreiner, Peter R

    2014-03-11

    London dispersion interactions play a key role in nature, in particular, in membranes that constitute natural barriers. Here we demonstrate that the spatial alignment of "molecular ladders" ([n]ladderanes), i.e., highly unusual and strained all-trans-fused cyclobutane moieties, leads to much larger attractive dispersion interactions as compared to alkyl chains of the same length. This provides a rationale for the occurrence of peculiar ladderane fatty acids in the dense cell walls of anammox bacteria. Despite the energetic penalty paid for the assembly of such strained polycycles, the advantage lies in significantly higher, dispersion-dominated interaction energies as compared to straight-chain hydrocarbon moieties commonly found in fatty acids. We discern the dispersion contributions to the total interaction energies using a variety of computational methods including modern dispersion-corrected density functional theory and high level ab initio approaches. Utilizing larger assemblies, we also show that the intermolecular interactions behave additively. PMID:26580198

  19. A Cascade-Reaction Nanoreactor Composed of a Bifunctional Molecularly Imprinted Polymer that Contains Pt Nanoparticles.

    PubMed

    Wang, Jiao; Zhu, Maiyong; Shen, Xiaojuan; Li, Songjun

    2015-05-11

    This study was aimed at addressing the present challenge of cascade reactions, namely, how to furnish the catalysts with desired and hierarchical catalytic ability. This issue was addressed by constructing a cascade-reaction nanoreactor made of a bifunctional molecularly imprinted polymer containing acidic catalytic sites and Pt nanoparticles. The acidic catalytic sites within the imprinted polymer allowed one specified reaction, whereas the encapsulated Pt nanoparticles were responsible for another coupled reaction. To that end, the unique imprinted polymer was fabricated by using two well-coupled templates, that is, 4-nitrophenyl acetate and 4-nitrophenol. The catalytic hydrolysis of the former compound at the acidic catalytic sites led to the formation of the latter compound, which was further reduced by the encapsulated Pt nanoparticles to 4-aminophenol. Therefore, this nanoreactor demonstrated a catalytic-cascade ability. This protocol opens up the opportunity to develop functional catalysts for complicated chemical processes. PMID:25846700

  20. Lanthanides in the frame of Molecular Magnetism

    NASA Astrophysics Data System (ADS)

    Gatteschi, D.

    2014-07-01

    Molecular magnetism is producing new types of materials which cover up to date aspects of basic science together with possible applications. This article highlights recent results from the point of view of lanthanides which are now intensively used to produce single molecule magnets, single chain and single ion magnets. After a short introduction reminding the main steps of development of molecular magnetism, the basic properties of lanthanides will be covered highlighting important features which are enhanced by the electronic structure of lanthanides, like spin frustration and chirality, anisotropy and non collinear axes in zero and one dimensional materials. A paragraph of conclusions will discuss what has been done and theperspectives to be expected.

  1. Test equipment for a flywheel energy storage system using a magnetic bearing composed of superconducting coils and superconducting bulks

    NASA Astrophysics Data System (ADS)

    Ogata, M.; Matsue, H.; Yamashita, T.; Hasegawa, H.; Nagashima, K.; Maeda, T.; Matsuoka, T.; Mukoyama, S.; Shimizu, H.; Horiuchi, S.

    2016-05-01

    Energy storage systems are necessary for renewable energy sources such as solar power in order to stabilize their output power, which fluctuates widely depending on the weather. Since ‘flywheel energy storage systems’ (FWSSs) do not use chemical reactions, they do not deteriorate due to charge or discharge. This is an advantage of FWSSs in applications for renewable energy plants. A conventional FWSS has capacity limitation because of the mechanical bearings used to support the flywheel. Therefore, we have designed a superconducting magnetic bearing composed of a superconducting coil stator and a superconducting bulk rotor in order to solve this problem, and have experimentally manufactured a large scale FWSS with a capacity of 100 kWh and an output power of 300 kW. The superconducting magnetic bearing can levitate 4 tons and enables the flywheel to rotate smoothly. A performance confirmation test will be started soon. An overview of the superconducting FWSS is presented in this paper.

  2. Molecular Design for Cryogenic Magnetic Coolants.

    PubMed

    Liu, Jun-Liang; Chen, Yan-Cong; Tong, Ming-Liang

    2016-04-01

    The area of molecular magnetic coolants has developed rapidly in recent years. A large number of competitive candidates have been reported, with the cooling performances chasing each other. In this account, four explicit strategies, namely, increasing ground-state spin, reducing magnetic anisotropy, weakening magnetic interactions, and lowering the molecular weight, are proposed from the theoretical viewpoint towards improving the magnetocaloric effect (MCE). According to this guidance, these successful strategies are discussed to pursue excellent magnetic coolants. This is accompanied by a discussion of the representative examples reported by our group. The magnetic entropy change increases from one compound to another, which in the most pronounced cases is suggestive of being the largest MCE in magnetic coolants. PMID:26929130

  3. Magnetic Splitting of Molecular Lines in Sunspot

    NASA Astrophysics Data System (ADS)

    Berdyugina, S. V.; Frutiger, C.; Solanki, S. K.

    A study of molecular lines in sunspots is of particular interest because of their high temperature and pressure sensitivity. Many of them are also magnetically sensitive, but this was not yet widely investigated. With high-resolution, high signal-to-noise Fourier spectroscopy in four Stokes parameters now available, the use of molecular lines for studying the structure of sunspots brings real gains. One is the extension of spot models, including magnetic field, up to layers, where atomic lines suffer from NLTE effects but molecules can still be treated in the LTE approximation. Equally important is the fact that since molecular lines are extremely temperature sensitive they can be used to probe the thermal and magnetic structure of the coolest parts of sunspots. We present calculations of splitting and the Stokes parameters for a number of molecular lines in the visible and near-infrared regions. Our first selections are the green system of MgH A2Π-X2σ and the TiO triplet α, γ' and γ systems as the most studied band systems in the sunspot spectrum. The calculations involve different regimes of the molecular Zeeman effect, up to the complete Paschen-Back effect for individual lines. We look for molecular lines which can be used along with atomic lines to derive magnetic, thermal and dynamic properties of the umbra.

  4. Magnetic sensing technology for molecular analyses

    PubMed Central

    Issadore, D.; Park, Y. I.; Shao, H.; Min, C.; Lee, K.; Liong, M.; Weissleder, R.; Lee, H.

    2014-01-01

    Magnetic biosensors, based on nanomaterials and miniature electronics, have emerged as a powerful diagnostic platform. Benefiting from the inherently negligible magnetic background of biological objects, magnetic detection is highly selective even in complex biological media. The sensing thus requires minimal sample purification, and yet achieves high signal-to-background contrast. Moreover, magnetic sensors are also well-suited for miniaturization to match the size of biological targets, which enables sensitive detection of rare cells and small amounts of molecular markers. We herein summarize recent advances in magnetic sensing technologies, with an emphasis on clinical applications in point-of-care settings. Key components of sensors, including magnetic nanomaterials, labeling strategies and magnetometry, are reviewed. PMID:24887807

  5. Molecular magnetic resonance imaging in cancer.

    PubMed

    Haris, Mohammad; Yadav, Santosh K; Rizwan, Arshi; Singh, Anup; Wang, Ena; Hariharan, Hari; Reddy, Ravinder; Marincola, Francesco M

    2015-01-01

    The ability to identify key biomolecules and molecular changes associated with cancer malignancy and the capacity to monitor the therapeutic outcome against these targets is critically important for cancer treatment. Recent developments in molecular imaging based on magnetic resonance (MR) techniques have provided researchers and clinicians with new tools to improve most facets of cancer care. Molecular imaging is broadly described as imaging techniques used to detect molecular signature at the cellular and gene expression levels. This article reviews both established and emerging molecular MR techniques in oncology and discusses the potential of these techniques in improving the clinical cancer care. It also discusses how molecular MR, in conjunction with other structural and functional MR imaging techniques, paves the way for developing tailored treatment strategies to enhance cancer care. PMID:26394751

  6. Molecular mechanism of magnet formation in bacteria.

    PubMed

    Matsunaga, T; Sakaguchi, T

    2000-01-01

    Magnetic bacteria have an ability to synthesize intracellular ferromagnetic crystalline particles consisting of magnetite (Fe3O4) or greigite (Fe3S4) which occur within a specific size range (50-100 nm). Bacterial magnetic particles (BMPs) can be distinguished by the regular morphology and the presence of an thin organic membrane enveloping crystals from abiologically formed magnetite. The particle is the smallest magnetic crystal that has a regular morphology within the single domain size. Therefore, BMPs have an unfathomable amount of potential value for various technological applications not only scientific interests. However, the molecular and genetic mechanism of magnetite biomineralization is hardly understood although iron oxide formation occurs widely in many higher animals as well as microorganisms. In order to elucidate the molecular and genetic mechanisms of magnetite biomineralization, a magnetic bacterium Magnetospirillum sp. AMB-1, for which gene transfer and transposon mutagenesis techniques had been recently developed, has been used as a model organism. Several findings and information on the BMPs formation process have been obtained within this decade by means of studies with this model organism and its related one. Biomineralization mechanism and potential availability in biotechnology of bacterial magnets have been elucidated through molecular and genetic approach. PMID:16232810

  7. Recorder Composer

    ERIC Educational Resources Information Center

    Stephenson, Kimberly

    2012-01-01

    The best moments happen when students begin to realize how much power they have and use that power to create. Composing as they master different instrumental stages helps students make composition and performance a natural step in learning. A step-by-step process (rhythm notation, add pitches, copy to a five-line staff, check work, and play) keeps…

  8. Magnetic properties and microstructure of Sm-Co/α-Fe nanocomposite thick film-magnets composed of multi-layers over 700 layers

    SciTech Connect

    Tou, A. Morimura, T.; Nakano, M.; Yamai, T.; Fukunaga, H.

    2014-05-07

    We synthesized Sm-Co/α-Fe nanocomposite film-magnets, approximately 10 μm in thickness, composed of 780 layers by the pulse laser deposition method. Transmission electron microscopic observations revealed that the synthesized film is composed of Sm-Co and α-Fe layers with the well-controlled α-Fe thickness of approximately 10–20 nm, which is suitable one predicted by the micromagnetic simulation. In spite of the enhanced interlayer diffusion of Fe and Co by annealing for crystallization, the (BH){sub max} value of 100 kJ/m{sup 3} was obtained at the averaged compositions of Sm/(Sm + Co) = 0.16 and Fe/(Sm + Co + Fe) = 0.47. The α-Fe fraction for obtaining the highest (BH){sub max} value was smaller than that expected from the micromagnetic simulation. Although the annealing for crystallization lay the easy direction of magnetization in the plane, the film is not expected to have strong crystallographic texture.

  9. Quantum entanglement and coherence in molecular magnets

    NASA Astrophysics Data System (ADS)

    Shiddiq, Muhandis

    Quantum computers are predicted to outperform classical computers in certain tasks, such as factoring large numbers and searching databases. The construction of a computer whose operation is based on the principles of quantum mechanics appears extremely challenging. Solid state approaches offer the potential to answer this challenge by tailor-making novel nanomaterials for quantum information processing (QIP). Molecular magnets, which are materials whose energy levels and magnetic quantum states are well defined at the molecular level, have been identified as a class of material with properties that make them attractive for quantum computing purpose. In this dissertation, I explore the possibilities and challenges for molecular magnets to be used in quantum computing architecture. The properties of molecular magnets that are critical for applications in quantum computing, i.e., quantum entanglement and coherence, are comprehensively investigated to probe the feasibility of molecular magnets to be used as quantum bits (qubits). Interactions of qubits with photons are at the core of QIP. Photons can be used to detect and manipulate qubits, after which information can then be transferred over long distances. As a potential candidate for qubits, the interactions between Fe8 single-molecule magnets (SMMs) and cavity photons were studied. An earlier report described that a cavity mode splitting was observed in a spectrum of a cavity filled with a single-crystal of Fe8 SMMs. This splitting was interpreted as a vacuum Rabi splitting (VRS), which is a signature of an entanglement between a large number of SMMs and a cavity photon. However, find that large absorption and dispersion of the magnetic susceptibility are the reasons for this splitting. This finding highlights the fact that an observation of a peak splitting in a cavity transmission spectrum neither represents an unambiguous indication of quantum coherence in a large number of spins, nor a signature of

  10. Magnetic deflagration in the molecular magnet manganese-12-ac

    NASA Astrophysics Data System (ADS)

    McHugh, Sean

    In 1995, Paulsen and Park [1, 2] observed abrupt spontaneous reversals of the magnetization in crystals of the molecular magnet Mn12-ac, which they dubbed "magnetic avalanches". They suggested that the magnetic avalanches were a thermal runaway process where the reversing spins release heat stimulating further relaxation. Various exotic phenomena were proposed as an alternative explanations [3]. In 2005, Suzuki et al. [4] established that this spontaneous magnetic relaxation occurs as a "front" separating regions of opposing magnetization that propagates at a constant speed through the crystal. They suggested that this propagating front is analogous to a flame in chemical deflagration and introduced the thermal relaxation process, magnetic deflagration. The analysis presented there was limited by lack of data. A more thorough comparison with the theory would require the ability to trigger avalanches in a more controlled way rather than wait for their spontaneous occurrence. The work presented in this thesis is a continuation of the program initiated by Suzuki [4, 5]. Significant progress experimental progress has been made allowing us to trigger avalanches over a wide range of conditions. The magnetization dynamics and the ignition temperatures are studied in detail using an array of micro-sized Hall sensors and Germanium thermometers. In addition, we report the existence of a new species of avalanches consisting only of the fast-relaxing isomers of Mn12-ac, the so-called "minor species". We explore avalanches of both species, as well as the interaction between them. Finally, a detailed analysis is performed to compare the experiment with the theory of magnetic deflagration [6]. We find the theory of magnetic deflagration to be consistent with the data and extract values for the key physical quantities: the thermal diffusivity and avalanche front temperatures. Agreement between our predicted values and an independent measurement of these quantities would provide

  11. ANCHORING MAGNETIC FIELD IN TURBULENT MOLECULAR CLOUDS

    SciTech Connect

    Li Huabai; Goodman, Alyssa; Darren Dowell, C.; Hildebrand, Roger; Novak, Giles

    2009-10-20

    One of the key problems in star formation research is to determine the role of magnetic fields. Starting from the atomic intercloud medium which has density n {sub H} approx 1 cm{sup -3}, gas must accumulate from a volume several hundred pc across in order to form a typical molecular cloud. Star formation usually occurs in cloud cores, which have linear sizes below 1 pc and densities n {sub H2} > 10{sup 5} cm{sup -3}. With current technologies, it is hard to probe magnetic fields at scales lying between the accumulation length and the size of cloud cores, a range corresponds to many levels of turbulent eddy cascade, and many orders of magnitude of density amplification. For field directions detected from the two extremes, however, we show here that a significant correlation is found. Comparing this result with molecular cloud simulations, only the sub-Alfvenic cases result in field orientations consistent with our observations.

  12. Pauli spin blockade in double molecular magnets

    NASA Astrophysics Data System (ADS)

    Płomińska, Anna; Weymann, Ireneusz

    2016-07-01

    The Pauli spin blockade effect in transport through two, coupled in series, single molecular magnets weakly attached to external leads is considered theoretically. By using the real-time diagrammatic technique in the lowest-order perturbation theory with respect to the coupling strength, the behavior of the current and the shot noise is studied in the nonlinear response regime. It is shown that the current suppression occurs due to the occupation of highest-weight spin states of the system. Moreover, transport properties are found to strongly depend on parameters of the double molecular magnet, such as the magnitude of spin, internal exchange interaction and the hopping between the molecules. It is also demonstrated that the current suppression may be accompanied by negative differential conductance and a large super-Poissonian shot noise. The mechanisms leading to those effects are discussed.

  13. Molecular Magnetism in MnTe Clusters

    NASA Astrophysics Data System (ADS)

    Chen, Jia; Nanduri, Arun; Choi, Bonnie; Millis, Andrew; Reichman, David; Roy, Xavier

    Electron correlation in recently synthesized molecular clusters with Mn4Te4 cores in cubane structures and ligand exteriors are studied experimentally and theoretically. We used density functional theory with on-site Coulomb interactions (DFT+U) to construct effective spin Hamiltonians and estimate the dependence of parameters on choice of ligand. The lack of inversion symmetry combined with the heavy tellurium ions leads to a significant Dzyaloshinskii-Moriya (DM) interaction. Comparison of measurements to the magnetic susceptibility calculated from the spin model is used to validate the results. We also extend this work to more complex clusters with more than one cubanes, where interesting high-spin ground state may occur. It has been measured recently, Fe8Te8 in dicubane structure has ground state with magnetization of12μB, which makes it promising candidate for single molecular magnets. A.J.M. acknowledges support from NSF under Contract DMR-1308236. J.C. is supported by the NSF MRSEC program through Columbia in the Center for Precision Assembly of Superstratic and Superatomic Solids under Grant No.DMR-1420634.

  14. Magnetic molecularly imprinted polymer for aspirin recognition and controlled release

    NASA Astrophysics Data System (ADS)

    Kan, Xianwen; Geng, Zhirong; Zhao, Yao; Wang, Zhilin; Zhu, Jun-Jie

    2009-04-01

    Core-shell structural magnetic molecularly imprinted polymers (magnetic MIPs) with combined properties of molecular recognition and controlled release were prepared and characterized. Magnetic MIPs were synthesized by the co-polymerization of methacrylic acid (MAA) and trimethylolpropane trimethacrylate (TRIM) around aspirin (ASP) at the surface of double-bond-functionalized Fe3O4 nanoparticles in chloroform. The obtained spherical magnetic MIPs with diameters of about 500 nm had obvious superparamagnetism and could be separated quickly by an external magnetic field. Binding experiments were carried out to evaluate the properties of magnetic MIPs and magnetic non-molecularly imprinted polymers (magnetic NIPs). The results demonstrated that the magnetic MIPs had high adsorption capacity and selectivity to ASP. Moreover, release profiles and release rate of ASP from the ASP-loaded magnetic MIPs indicated that the magnetic MIPs also had potential applications in drug controlled release.

  15. Molecular structure and motion in zero field magnetic resonance

    SciTech Connect

    Jarvie, T.P.

    1989-10-01

    Zero field magnetic resonance is well suited for the determination of molecular structure and the study of motion in disordered materials. Experiments performed in zero applied magnetic field avoid the anisotropic broadening in high field nuclear magnetic resonance (NMR) experiments. As a result, molecular structure and subtle effects of motion are more readily observed.

  16. Electromagnetically induced grating in a crystal of molecular magnets system

    NASA Astrophysics Data System (ADS)

    Liu, Jibing; Liu, Na; Shan, Chuanjia; Liu, Tangkun; Li, Hong; Zheng, Anshou; Xie, Xiao-Tao

    2016-07-01

    We investigate the response of the molecular system to the magnetic field modulation. Molecular magnets are subjected to a strong standing ac magnetic field and a weak probe magnetic field. The transmission and absorption of the weak probe magnetic field can be changed due to quantum coherence and the spatially modulating of the standing field. And a electromagnetically induced grating is formed in the crystal of molecular magnets via electromagnetically induced transparency (EIT). The diffraction efficiency of the grating can be adjusted efficiently by tuning the intensity of the standing wave field and the single photon detuning.

  17. Magnetic hysteresis in a lanthanide molecular magnet dimer system

    NASA Astrophysics Data System (ADS)

    Atkinson, James; Cebulka, Rebecca; Del Barco, Enrique; Roubeau, Olivier; Velasco, Veronica; Barrios, Leo; Aromi, Guillem

    Molecular magnets present a wonderful means for studying the dynamics of spin. Often synthesized as a crystal lattice of identical systems, ensemble measurements enable thorough detailing of the internal degrees of freedom. Here we present the results of characterization performed on a dimer system, CeTm(HL)2(H2L)NO3pyH2O (L = ligand, C45H31O15N3), consisting of two lanthanide spins (Cerium and Thulium) with expected local axial anisotropies tilted with respect to each other. Microwave EPR spectroscopy at low temperature reveals hysteresis in observed absorption features, with angle dependence studies indicating the presence of several ``easy axis'' orientations. We attempt to understand this system through modelling via a spin Hamiltonian, and to determine the strength and nature of the coupling between the lanthanide centers. This research was funded through NSF Grant # 24086159.

  18. Properties of Strain Compensated Symmetrical Triangular Quantum Wells Composed of InGaAs/InAs Chirped Superlattice Grown Using Gas Source Molecular Beam Epitaxy

    NASA Astrophysics Data System (ADS)

    Gu, Yi; Zhang, Yong-Gang

    2008-02-01

    We investigate the properties of symmetrical triangular quantum wells composed of InGaAs/InAs chirped superlattice, which is grown by gas source molecular beam epitaxy via digital alloy method. In the quantum well structure tensile AlInGaAs are used as barriers to partially compensate for the significant compressive strain in the wells, the strain compensation effects are confirmed by x-ray measurement. The photoluminescence spectra of the sample are dominated by the excitonic recombination peak in the whole temperature range. The thermal quenching, peak energy shift and line-width broadening of the PL spectra are analysed in detail, the mechanisms are discussed.

  19. Enhancement of conduction noise absorption by hybrid absorbers composed of indium-tin-oxide thin film and magnetic composite sheet on a microstrip line

    NASA Astrophysics Data System (ADS)

    Kim, Sun-Hong; Kim, Sung-Soo

    2014-05-01

    In order to develop wide-band noise absorbers with a focused design for low frequency performance, this study investigates hybrid absorbers that are composed of conductive indium-tin-oxide (ITO) thin film and magnetic composite sheets. The ITO films prepared via reactive sputtering exhibit a typical value of electrical resistivity of ≃10-4 Ω m. Rubber composites with flaky Fe-Si-Al particles are used as the magnetic sheet with a high permeability and high permittivity. For the ITO film with a low surface resistance and covered by the magnetic sheet, approximately 90% power absorption can be obtained at 1 GHz, which is significantly higher than that of the original magnetic sheet or ITO film. The high power absorption of the hybrid absorber is attributed to the enhanced ohmic loss of the ITO film through increased electric field strength bounded by the upper magnetic composite sheet. However, for the reverse layering sequence of the ITO film, the electric field experienced by ITO film is very weak due to the electromagnetic shielding by the under layer of magnetic sheet, which does not result in enhanced power absorption.

  20. Enhancement of conduction noise absorption by hybrid absorbers composed of indium-tin-oxide thin film and magnetic composite sheet on a microstrip line

    SciTech Connect

    Kim, Sun-Hong; Kim, Sung-Soo

    2014-05-05

    In order to develop wide-band noise absorbers with a focused design for low frequency performance, this study investigates hybrid absorbers that are composed of conductive indium-tin-oxide (ITO) thin film and magnetic composite sheets. The ITO films prepared via reactive sputtering exhibit a typical value of electrical resistivity of ≃10{sup −4} Ω m. Rubber composites with flaky Fe-Si-Al particles are used as the magnetic sheet with a high permeability and high permittivity. For the ITO film with a low surface resistance and covered by the magnetic sheet, approximately 90% power absorption can be obtained at 1 GHz, which is significantly higher than that of the original magnetic sheet or ITO film. The high power absorption of the hybrid absorber is attributed to the enhanced ohmic loss of the ITO film through increased electric field strength bounded by the upper magnetic composite sheet. However, for the reverse layering sequence of the ITO film, the electric field experienced by ITO film is very weak due to the electromagnetic shielding by the under layer of magnetic sheet, which does not result in enhanced power absorption.

  1. Hydrogen production on a hybrid photocatalytic system composed of ultrathin CdS nanosheets and a molecular nickel complex.

    PubMed

    Xu, You; Yin, Xuguang; Huang, Yi; Du, Pingwu; Zhang, Bin

    2015-03-16

    The production of clean and renewable hydrogen through water splitting by using solar energy has received much attention due to the increasing global energy demand. We report an economic and artificial photosynthetic system free of noble metals, consisting of ultrathin CdS nanosheets as a photosensitizer and nickel-based complex as a molecular catalyst. Emission quenching and flash photolysis studies reveal that this hybrid system allows for effective electron transfer from the excited CdS nanosheets to the nickel-based complex to generate reduced intermediate species for efficient hydrogen evolution. Notably, the unique morphological and structural features of the ultrathin CdS nanosheets contribute to the highly efficient photocatalytic performance. As a consequence, the resulting system shows exceptional activity and stability for photocatalytic hydrogen evolution in aqueous solution with a turnover number (TON) of about 28,000 versus catalyst and a lifetime of over 90 h under visible light irradiation. PMID:25663129

  2. (Photo)physical Properties of New Molecular Glasses End-Capped with Thiophene Rings Composed of Diimide and Imine Units

    PubMed Central

    2014-01-01

    New symmetrical arylene bisimide derivatives formed by using electron-donating–electron-accepting systems were synthesized. They consist of a phthalic diimide or naphthalenediimide core and imine linkages and are end-capped with thiophene, bithiophene, and (ethylenedioxy)thiophene units. Moreover, polymers were obtained from a new diamine, N,N′-bis(5-aminonaphthalenyl)naphthalene-1,4,5,8-dicarboximide and 2,5-thiophenedicarboxaldehyde or 2,2′-bithiophene-5,5′-dicarboxaldehyde. The prepared azomethine diimides exhibited glass-forming properties. The obtained compounds emitted blue light with the emission maximum at 470 nm. The value of the absorption coefficient was determined as a function of the photon energy using spectroscopic ellipsometry. All compounds are electrochemically active and undergo reversible electrochemical reduction and irreversible oxidation processes as was found in cyclic voltammetry and differential pulse voltammetry (DPV) studies. They exhibited a low electrochemically (DPV) calculated energy band gap (Eg) from 1.14 to 1.70 eV. The highest occupied molecular orbital and lowest unoccupied molecular orbital levels and Eg were additionally calculated theoretically by density functional theory at the B3LYP/6-31G(d,p) level. The photovoltaic properties of two model compounds as the active layer in organic solar cells in the configuration indium tin oxide/poly(3,4-(ethylenedioxy)thiophene):poly(styrenesulfonate)/active layer/Al under an illumination of 1.3 mW/cm2 were studied. The device comprising poly(3-hexylthiophene) with the compound end-capped with bithiophene rings showed the highest value of Voc (above 1 V). The conversion efficiency of the fabricated solar cell was in the range of 0.69–0.90%. PMID:24966893

  3. (Photo)physical Properties of New Molecular Glasses End-Capped with Thiophene Rings Composed of Diimide and Imine Units.

    PubMed

    Grucela-Zajac, Marzena; Bijak, Katarzyna; Kula, Slawomir; Filapek, Michal; Wiacek, Malgorzata; Janeczek, Henryk; Skorka, Lukasz; Gasiorowski, Jacek; Hingerl, Kurt; Sariciftci, Niyazi Serdar; Nosidlak, Natalia; Lewinska, Gabriela; Sanetra, Jerzy; Schab-Balcerzak, Ewa

    2014-06-19

    New symmetrical arylene bisimide derivatives formed by using electron-donating-electron-accepting systems were synthesized. They consist of a phthalic diimide or naphthalenediimide core and imine linkages and are end-capped with thiophene, bithiophene, and (ethylenedioxy)thiophene units. Moreover, polymers were obtained from a new diamine, N,N'-bis(5-aminonaphthalenyl)naphthalene-1,4,5,8-dicarboximide and 2,5-thiophenedicarboxaldehyde or 2,2'-bithiophene-5,5'-dicarboxaldehyde. The prepared azomethine diimides exhibited glass-forming properties. The obtained compounds emitted blue light with the emission maximum at 470 nm. The value of the absorption coefficient was determined as a function of the photon energy using spectroscopic ellipsometry. All compounds are electrochemically active and undergo reversible electrochemical reduction and irreversible oxidation processes as was found in cyclic voltammetry and differential pulse voltammetry (DPV) studies. They exhibited a low electrochemically (DPV) calculated energy band gap (E g) from 1.14 to 1.70 eV. The highest occupied molecular orbital and lowest unoccupied molecular orbital levels and E g were additionally calculated theoretically by density functional theory at the B3LYP/6-31G(d,p) level. The photovoltaic properties of two model compounds as the active layer in organic solar cells in the configuration indium tin oxide/poly(3,4-(ethylenedioxy)thiophene):poly(styrenesulfonate)/active layer/Al under an illumination of 1.3 mW/cm(2) were studied. The device comprising poly(3-hexylthiophene) with the compound end-capped with bithiophene rings showed the highest value of V oc (above 1 V). The conversion efficiency of the fabricated solar cell was in the range of 0.69-0.90%. PMID:24966893

  4. In situ forming hydrogels composed of oxidized high molecular weight hyaluronic acid and gelatin for nucleus pulposus regeneration.

    PubMed

    Chen, Yu-Chun; Su, Wen-Yu; Yang, Shu-Hua; Gefen, Amit; Lin, Feng-Huei

    2013-02-01

    Encapsulation of nucleus pulposus (NP) cells within in situ forming hydrogels is a novel biological treatment for early stage intervertebral disc degeneration. The procedure aims to prolong the life of the degenerating discs and to regenerate damaged tissue. In this study we developed an injectable oxidized hyaluronic acid-gelatin-adipic acid dihydrazide (oxi-HAG-ADH) hydrogel. High molecular weight (1900 kDa) hyaluronic acid was crosslinked with various concentrations of gelatin to synthesize the hydrogels and their viscoelastic properties were analyzed. Interactions between the hydrogels, NP cells, and the extracellular matrix (ECM) were also evaluated, as were the effects of the hydrogels on NP cell gene expression. The hydrogels possess several clinical advantages, including sterilizability, low viscosity for injection, and ease of use. The viscoelastic properties of the hydrogels were similar to native tissue, as reflected in the complex shear modulus (∼11-14 kPa for hydrogels, 11.3 kPa for native NP). Cultured NP cells not only attached to the hydrogels but also survived, proliferated, and maintained their round morphology. Importantly, we found that hydrogels increased NP cell expression of several crucial ECM-related genes, such as COL2A1, AGN, SOX-9, and HIF-1A. PMID:23041783

  5. Hybrid absorbers composed of Fe3O4 thin film and magnetic composite sheet and enhancement of conduction noise absorption on a microstrip line

    NASA Astrophysics Data System (ADS)

    Kim, Sung-Soo

    2015-05-01

    In response to develop wide-band noise absorbers with an improved low-frequency performance, this study investigates hybrid absorbers that are composed of conductive Fe3O4 thin film and magnetic composite sheets. The Fe3O4 films prepared via reactive sputtering exhibit a typical value of electrical resistivity of ≃10-4 Ωm. Rubber composites with flaky Fe-Si-Al particles of a high permeability and high permittivity are used as the magnetic sheet functioning as an electromagnetic shield barrier. Microstrip lines with a characteristic impedance of 50 Ω are used to measure the noise absorbing properties. For the Fe3O4 film with a low surface resistance and covered by the magnetic sheet, approximately 80% power absorption can be obtained at 1 GHz, which is significantly higher than that of the original magnetic sheet or Fe3O4 film. The high power absorption of the hybrid absorber is attributed to the enhanced ohmic loss of the Fe3O4 film through increased electric field strength bounded by the upper magnetic composite sheet. The noise absorption is further enhanced through increasing the electrical conductivity of the film containing more conductive phase (Fe3O4 + Fe), which can be prepared in a reduced oxygen partial pressure during reactive sputtering.

  6. Molecular topology tuning of bipolar host materials composed of fluorene-bridged benzimidazole and carbazole for highly efficient electrophosphorescence.

    PubMed

    Mondal, Ejabul; Hung, Wen-Yi; Chen, Yang-Huei; Cheng, Ming-Hung; Wong, Ken-Tsung

    2013-08-01

    Two new molecules, CzFCBI and CzFNBI, have been tailor-made to serve as bipolar host materials to realize high-efficiency electrophosphorescent devices. The molecular design is configured with carbazole as the hole-transporting block and N-phenylbenzimidazole as the electron-transporting block hybridized through the saturated bridge center (C9) and meta-conjugation site (C3) of fluorene, respectively. With structural topology tuning of the connecting manner between N-phenylbenzimidazole and the fluorene core, the resulting physical properties can be subtly modulated. Bipolar host CzFCBI with a C connectivity between phenylbenzimidazole and the fluorene bridge exhibited extended π conjugation; therefore, a low triplet energy of 2.52 eV was observed, which is insufficient to confine blue phosphorescence. However, the monochromatic devices indicate that the matched energy-level alignment allows CzFCBI to outperform its N-connected counterpart CzFNBI while employing other long-wavelength-emitting phosphorescent guests. In contrast, the high triplet energy (2.72 eV) of CzFNBI imparted by the N connectivity ensures its utilization as a universal bipolar host for blue-to-red phosphors. With a common device configuration, CzFNBI has been utilized to achieve highly efficient and low-roll-off devices with external quantum efficiency as high as 14 % blue, 17.8 % green, 16.6 % yellowish-green, 19.5 % yellow, and 18.6 % red. In addition, by combining yellowish-green with a sky-blue emitter and a red emitter, a CzFNBI-hosted single-emitting-layer all-phosphor three-color-based white electrophosphorescent device was successfully achieved with high efficiencies (18.4 %, 36.3 cd A(-1) , 28.3 lm W(-1) ) and highly stable chromaticity (CIE x=0.43-0.46 and CIE y=0.43) at an applied voltage of 8 to 12 V, and a high color-rendering index of 91.6. PMID:23788214

  7. Dynamics of molecular superrotors in an external magnetic field

    NASA Astrophysics Data System (ADS)

    Korobenko, Aleksey; Milner, Valery

    2015-08-01

    We excite diatomic oxygen and nitrogen to high rotational states with an optical centrifuge and study their dynamics in an external magnetic field. Ion imaging is employed to directly visualize, and follow in time, the rotation plane of the molecular superrotors. The two different mechanisms of interaction between the magnetic field and the molecular angular momentum in paramagnetic oxygen and non-magnetic nitrogen lead to qualitatively different behaviour. In nitrogen, we observe the precession of the molecular angular momentum around the field vector. In oxygen, strong spin-rotation coupling results in faster and richer dynamics, encompassing the splitting of the rotation plane into three separate components. As the centrifuged molecules evolve with no significant dispersion of the molecular wave function, the observed magnetic interaction presents an efficient mechanism for controlling the plane of molecular rotation.

  8. Design and Realization of a Three Degrees of Freedom Displacement Measurement System Composed of Hall Sensors Based on Magnetic Field Fitting by an Elliptic Function

    PubMed Central

    Zhao, Bo; Wang, Lei; Tan, Jiu-Bin

    2015-01-01

    This paper presents the design and realization of a three degrees of freedom (DOFs) displacement measurement system composed of Hall sensors, which is built for the XYθz displacement measurement of the short stroke stage of the reticle stage of lithography. The measurement system consists of three pairs of permanent magnets mounted on the same plane on the short stroke stage along the Y, Y, X directions, and three single axis Hall sensors correspondingly mounted on the frame of the reticle stage. The emphasis is placed on the decoupling and magnetic field fitting of the three DOFs measurement system. The model of the measurement system is illustrated, and the XY positions and θZ rotation of the short stroke stage can be obtained by decoupling the sensor outputs. A magnetic field fitting by an elliptic function-based compensation method is proposed. The practical field intensity of a permanent magnet at a certain plane height can be substituted for the output voltage of a Hall sensors, which can be expressed by the elliptic function through experimental data as the crucial issue to calculate the three DOFs displacement. Experimental results of the Hall sensor displacement measurement system are presented to validate the proposed three DOFs measurement system. PMID:26370993

  9. Design and Realization of a Three Degrees of Freedom Displacement Measurement System Composed of Hall Sensors Based on Magnetic Field Fitting by an Elliptic Function.

    PubMed

    Zhao, Bo; Wang, Lei; Tan, Jiu-Bin

    2015-01-01

    This paper presents the design and realization of a three degrees of freedom (DOFs) displacement measurement system composed of Hall sensors, which is built for the XYθz displacement measurement of the short stroke stage of the reticle stage of lithography. The measurement system consists of three pairs of permanent magnets mounted on the same plane on the short stroke stage along the Y, Y, X directions, and three single axis Hall sensors correspondingly mounted on the frame of the reticle stage. The emphasis is placed on the decoupling and magnetic field fitting of the three DOFs measurement system. The model of the measurement system is illustrated, and the XY positions and θZ rotation of the short stroke stage can be obtained by decoupling the sensor outputs. A magnetic field fitting by an elliptic function-based compensation method is proposed. The practical field intensity of a permanent magnet at a certain plane height can be substituted for the output voltage of a Hall sensors, which can be expressed by the elliptic function through experimental data as the crucial issue to calculate the three DOFs displacement. Experimental results of the Hall sensor displacement measurement system are presented to validate the proposed three DOFs measurement system. PMID:26370993

  10. Composing and Arranging Careers

    ERIC Educational Resources Information Center

    Schwartz, Elliott; And Others

    1977-01-01

    With the inspiration, the originality, the skill and craftsmanship, the business acumen, the patience, and the luck, it's possible to become a classical composer, pop/rock/country composer, jingle composer, or educational composer. Describes these careers. (Editor/RK)

  11. Magnetic and microwave absorption properties of self-assemblies composed of core-shell cobalt-cobalt oxide nanocrystals.

    PubMed

    Wang, Zhongzhu; Bi, Hong; Wang, Peihong; Wang, Min; Liu, Zhiwei; Shen, Lei; Liu, Xiansong

    2015-02-01

    Core-shell structure cobalt-cobalt oxide nanocomposites were directly synthesized via annealing Co nanocrystals in air at 300 °C. Their microstructure and magnetic properties were characterized by XRD, TEM, XPS and VSM, respectively. The microwave absorbing properties of the nanocomposite powders by dispersing them in wax were investigated in the 2-18 GHz frequency range. The sample that was annealed for 1 h exhibits the maximum reflection loss of -30.5 dB and a bandwidth of less than -10 dB covering the 12.6-17.3 GHz range with the coating thickness of only 1.7 mm. At the same thickness, the sample annealed for 3 h exhibits the maximum reflection loss of -24 dB and a bandwidth that almost covers the whole X-band (8-11.5 GHz). With increase in the insulating cobalt oxide shell, the enhanced permeability could contribute to the decrease of eddy current loss, and the permittivity could be easily adjusted; thus, the microwave absorption properties of the cobalt oxide nanocrystals could be easily adjusted. PMID:25559407

  12. Magnetic surfactants as molecular based-magnets with spin glass-like properties.

    PubMed

    Brown, Paul; Smith, Gregory N; Hernández, Eduardo Padrón; James, Craig; Eastoe, Julian; Nunes, Wallace C; Settens, Charles M; Hatton, T Alan; Baker, Peter J

    2016-05-01

    This paper reports the use of muon spin relaxation spectroscopy to study how the aggregation behavior of magnetic surfactants containing lanthanide counterions may be exploited to create spin glass-like materials. Surfactants provide a unique approach to building in randomness, frustration and competing interactions into magnetic materials without requiring a lattice of ordered magnetic species or intervening ligands and elements. We demonstrate that this magnetic behavior may also be manipulated via formation of micelles rather than simple dilution, as well as via design of surfactant molecular architecture. This somewhat unexpected result indicates the potential of using novel magnetic surfactants for the generation and tuning of molecular magnets. PMID:27028571

  13. Magnetic surfactants as molecular based-magnets with spin glass-like properties

    NASA Astrophysics Data System (ADS)

    Brown, Paul; Smith, Gregory N.; Padrón Hernández, Eduardo; James, Craig; Eastoe, Julian; Nunes, Wallace C.; Settens, Charles M.; Hatton, T. Alan; Baker, Peter J.

    2016-05-01

    This paper reports the use of muon spin relaxation spectroscopy to study how the aggregation behavior of magnetic surfactants containing lanthanide counterions may be exploited to create spin glass-like materials. Surfactants provide a unique approach to building in randomness, frustration and competing interactions into magnetic materials without requiring a lattice of ordered magnetic species or intervening ligands and elements. We demonstrate that this magnetic behavior may also be manipulated via formation of micelles rather than simple dilution, as well as via design of surfactant molecular architecture. This somewhat unexpected result indicates the potential of using novel magnetic surfactants for the generation and tuning of molecular magnets.

  14. Tracing the Magnetic Field Morphology of the Lupus I Molecular Cloud

    NASA Astrophysics Data System (ADS)

    Franco, G. A. P.; Alves, F. O.

    2015-07-01

    Deep R-band CCD linear polarimetry collected for fields with lines of sight toward the Lupus I molecular cloud is used to investigate the properties of the magnetic field within this molecular cloud. The observed sample contains about 7000 stars, almost 2000 of them with a polarization signal-to-noise ratio larger than 5. These data cover almost the entire main molecular cloud and also sample two diffuse infrared patches in the neighborhood of Lupus I. The large-scale pattern of the plane-of-sky projection of the magnetic field is perpendicular to the main axis of Lupus I, but parallel to the two diffuse infrared patches. A detailed analysis of our polarization data combined with the Herschel/SPIRE 350 μm dust emission map shows that the principal filament of Lupus I is constituted by three main clumps that are acted on by magnetic fields that have different large-scale structural properties. These differences may be the reason for the observed distribution of pre- and protostellar objects along the molecular cloud and the cloud’s apparent evolutionary stage. On the other hand, assuming that the magnetic field is composed of large-scale and turbulent components, we find that the latter is rather similar in all three clumps. The estimated plane-of-sky component of the large-scale magnetic field ranges from about 70 to 200 μG in these clumps. The intensity increases toward the Galactic plane. The mass-to-magnetic flux ratio is much smaller than unity, implying that Lupus I is magnetically supported on large scales. Based on observations collected at the Observatório do Pico dos Dias, operated by Laboratório Nacional de Astrofísica (LNA/MCTI, Brazil).

  15. Intensifying magnetic dark modes in the antisymmetric plasmonic quadrumer composed of Al/Al2O3 nanodisks with the placement of silicon nanospheres

    NASA Astrophysics Data System (ADS)

    Ahmadivand, Arash; Karabiyik, Mustafa; Pala, Nezih

    2015-03-01

    In this study, a quadrumer cluster composed of Al nanodisks in both symmetric and antisymmetric orientations has been utilized to generate magnetic hot-spots by using coil-type Fano resonances. Determining the accurate geometrical sizes for the examined cluster, we calculated the spectral response of the structure numerically. Utilizing strong plasmon resonance hybridization between Al/Al2O3 nanodisks that are suited in a close proximity to each other, such a finite and simple nanocluster yields intensified hidden magnetic fields |H| as a dark mode and electric |E| as a bright modes. Using and placement of silicon nanospheres in the unoccupied gap distance between proximal Al nanodisks give rise to significant enhancement in the energy and quality of the induced multiple Fano dips. Appearing of multiple Fano resonant modes in a coil-type regime in the UV and visible spectrum helps us to optimize the energy of generated magnetic hot-spots, significantly. Ultimately, we examined the sensitivity of the proposed final quadrumer by considering the behavior of Fano minima. We plotted the linear figure of merit (FoM) based on the Fano resonance energy differences in various conditions over the refractive index. Quantifying the FoM for the studied nanostructure, then we compared the quality of structure with the analogous nanoclusters. This work paves novel methods toward the utilization of Al/Al2O3 nanoparticles as a potential substance to employ in designing nanoclusters that are able to support strong dark resonances as well as bright modes. Wide-range working region, optimized electric and magnetic fields, multiple and high quality Fano dips, high FoM and low-costs are the superior features of the proposed artificial structure in comparison to analogous configurations.

  16. My Career: Composer

    ERIC Educational Resources Information Center

    Morganelli, Patrick

    2013-01-01

    In this article, the author talks about his career as a composer and offers some advice for aspiring composers. The author works as a composer in the movie industry, creating music that supports a film's story. Other composers work on television shows, and some do both television and film. The composer uses music to tell the audience what kind of…

  17. Enhanced magnetic fluid hyperthermia by micellar magnetic nanoclusters composed of Mn(x)Zn(1-x)Fe(2)O(4) nanoparticles for induced tumor cell apoptosis.

    PubMed

    Qu, Yang; Li, Jianbo; Ren, Jie; Leng, Junzhao; Lin, Chao; Shi, Donglu

    2014-10-01

    Monodispersed MnxZn1-xFe2O4 magnetic nanoparticles of 8 nm are synthesized and encapsulated in amphiphilic block copolymer for development of the hydrophilic magnetic nanoclusters (MNCs). These MNCs exhibit superparamagnetic characteristics, high specific absorption rate (SAR), large saturation magnetization (Ms), excellent stability, and good biocompatibility. MnFe2O4 and Mn0.6Zn0.4Fe2O4 are selected as optimum compositions for the MNCs (MnFe2O4/MNC and Mn0.6Zn0.4Fe2O4/MNC) and employed for magnetic fluid hyperthermia (MFH) in vitro. To ensure biosafety of MFH, the parameters of alternating magnetic field (AMF) and exposure time are optimized with low frequency, f, and strength of applied magnetic field, Happlied. Under optimized conditions, MFH of MnFe2O4/MNC and Mn0.6Zn0.4Fe2O4/MNC result in cancer cell death rate up to 90% within 15 min. The pathway of cancer cell death is identified as apoptosis, which occurs in mild hyperthermia near 43 °C. Both MnFe2O4/MNC and Mn0.6Zn0.4Fe2O4/MNC show similar efficiencies on drug-sensitive and drug-resistant cancer cells. On the basis of these findings, those MnxZn1-xFe2O4 nanoclusters can serve as a promising candidate for effective targeting, diagnosis, and therapy of cancers. The multimodal cancer treatment is also possible as amphiphilic block copolymer can encapsulate, in a similar fashion, different nanoparticles, hydrophobic drugs, and other functional molecules. PMID:25204363

  18. Molecular complex composed of β-cyclodextrin-grafted Chitosan and pH-sensitive amphipathic peptide for enhancing cellular cholesterol efflux under acidic pH.

    PubMed

    Takechi-Haraya, Yuki; Tanaka, Kento; Tsuji, Kohei; Asami, Yasuo; Izawa, Hironori; Shigenaga, Akira; Otaka, Akira; Saito, Hiroyuki; Kawakami, Kohsaku

    2015-03-18

    Excess of cholesterol in peripheral cells is known to lead to atherosclerosis. In this study, a molecular complex composed of β-cyclodextrin-grafted chitosan (BCC) and cellular cholesterol efflux enhancing peptide (CEEP), synthesized by modifying pH sensitive amphipathic GALA peptide, is introduced with the eventual aim of treating atherosclerosis. BCC has a markedly enhanced ability to induce cholesterol efflux from cell membranes compared to β-cyclodextrin, and the BCC-CEEP complex exhibited a 2-fold increase in cellular cholesterol efflux compared to BCC alone under weakly acidic conditions. Isothermal titration calorimetry and fluorescence spectroscopy measurements demonstrated that the random coil structure of CEEP at neutral pH converted to the α-helical structure at acidic pH, resulting in a three-order larger binding constant to BCC (K = 3.7 × 10(7) at pH 5.5) compared to that at pH 7.4 (K = 7.9 × 10(4)). Such high-affinity binding of CEEP to BCC at acidic pH leads to the formation of 100-nm-sized aggregate with positive surface charge, which would efficiently interact with cell membranes and induce cholesterol efflux. Since the cholesterol efflux ability of HDL is thought to be impaired under acidic environments in advanced atherosclerotic lesions, the BCC-CEEP complex might serve as a novel nanomaterial for treating atherosclerosis. PMID:25705984

  19. Deflagration, fronts of tunneling, and dipolar ordering in molecular magnets

    NASA Astrophysics Data System (ADS)

    Garanin, Dmitry

    2011-03-01

    Although there is no exchange interaction in crystals of molecular magnets characterized by a giant effective spin S (S = 10 for Mn 12 , and Fe 8) , magnetic field B (D) generated by magnetic moments g μ B S of magnetic molecules creates energy bias W (D) = 2 Sg μ BB (D) on a molecule that largely exceeds the tunnelling splitting Δ of matching quantum states on different sides of the anisotropy barrier. Thus the dipolar field has a profound influence on the processes of tunnelling and relaxation in molecular magnets. Both theoretical and experimental works showed a slow non-exponential relaxation of the magnetization in both initially ordered and completely disordered states since most of the spins are off tunneling resonance at any time. Recently a new mode of relaxation via tunneling has been found, the so-called fronts of tunneling, in which (within a 1 d theoretical model) dipolar field adjusts so that spins are on resonance within the broad front core. In this ``laminar'' regime fronts of tunnelling are moving fast at speeds that can exceed that of the temperature-driven magnetic deflagration, if a sufficiently strong transverse field is applied. However, a ``non-laminar'' regime has also been found in which instability causes spins to go off resonance and the front speed drops. In a combination with magnetic deflagration, the laminar regime becomes more stable and exists in the whole dipolar window 0 <= W <=W (D) on the external bias W , where the deflagration speed strongly increases. Another dipolar effect in molecular magnets is dipolar ordering below 1 K that has recently been shown to be non-uniform because of formation of magnetic domains. An object of current research is possible non-uniformity of magnetic deflagration and tunneling fronts via domain instability that could influence their speed.

  20. DISPERSION OF MAGNETIC FIELDS IN MOLECULAR CLOUDS. II

    SciTech Connect

    Houde, Martin; Chitsazzadeh, Shadi; Vaillancourt, John E.; Hildebrand, Roger H.; Kirby, Larry

    2009-12-01

    We expand our study on the dispersion of polarization angles in molecular clouds. We show how the effect of signal integration through the thickness of the cloud as well as across the area subtended by the telescope beam inherent to dust continuum measurements can be incorporated in our analysis to correctly account for its effect on the measured angular dispersion and inferred turbulent to large-scale magnetic field strength ratio. We further show how to evaluate the turbulent magnetic field correlation scale from polarization data of sufficient spatial resolution and high enough spatial sampling rate. We apply our results to the molecular cloud OMC-1, where we find a turbulent correlation length of delta approx 16 mpc, a turbulent to large-scale magnetic field strength ratio of approximately 0.5, and a plane-of-the-sky large-scale magnetic field strength of approximately 760 muG.

  1. DISPERSION OF MAGNETIC FIELDS IN MOLECULAR CLOUDS. I

    SciTech Connect

    Hildebrand, Roger H.; Kirby, Larry; Dotson, Jessie L.; Houde, Martin; Vaillancourt, John E.

    2009-05-01

    We describe a method for determining the dispersion of magnetic field vectors about large-scale fields in turbulent molecular clouds. The method is designed to avoid inaccurate estimates of magnetohydrodynamic or turbulent dispersion-and help avoiding inaccurate estimates of field strengths-due to a large-scale, nonturbulent field structure when using the well known method of Chandrasekhar and Fermi. Our method also provides accurate, independent estimates of the turbulent to large-scale magnetic field strength ratio. We discuss applications to the molecular clouds OMC-1, M17, and DR21(Main)

  2. Molecular magnetic dichroism in spectra of white dwarfs.

    PubMed

    Berdyugina, S V; Berdyugin, A V; Piirola, V

    2007-08-31

    We present novel calculations of the magnetic dichroism appearing in molecular bands in the presence of a strong magnetic field, which perturbs the internal structure of the molecule and results in net polarization due to the Paschen-Back effect. Based on that, we analyze new spectropolarimetric observations of the cool magnetic helium-rich white dwarf G99-37, which shows strongly polarized molecular bands in its spectrum. In addition to previously known molecular bands of the C2 Swan and CH A-X systems, we find a firm evidence for the violet CH B-X bands at 390 nm and C2 Deslandres-d'Azambuja bands at 360 nm. Combining the polarimetric observations with our model calculations, we deduce a dipole magnetic field of 7.5+/-0.5 MG with the positive pole pointing towards the Earth. We conclude that the developed technique is an excellent tool for studying magnetic fields on cool magnetic stars. PMID:17930997

  3. High-nuclearity magnetic clusters: Magnetic interactions in clusters encapsulated by molecular metal oxides

    NASA Astrophysics Data System (ADS)

    Borras-Almenar, Juan José; Coronado, Eugenio; Galan-Mascaros, Jose Ramón; Gómez-García, Carlos J.

    1995-02-01

    The ability of the molecular metal oxides derived from the Keggin anion [PW 12O 40] 3- to accommodate magnetic ions at specific sites, giving rise to polymetallic clusters with increasing spin nuclearities is discussed. Examples of magnetic clusters with three, four and nine metal ions exhibiting ferromagnetic exchange couplings or a coexistence of ferro- and antiferromagnetic couplings are reported.

  4. OH Zeeman Studies of Magnetic Field Strengths in Molecular Clouds

    NASA Astrophysics Data System (ADS)

    Thompson, Kristen L.; Troland, Thomas H.; Heiles, Carl E.

    2016-01-01

    Although stars have long been known to form in the gravitational collapse of molecular clouds, the details of the formation process are not well understood. There are many questions surrounding the formation mechanism of the clouds and the timescales on which they collapse. Star formation within the Galaxy has been found to be extremely inefficient, with stars forming at only 1-3% of the expected rate. Multiple theories addressing this inefficiency have emerged, placing varying degrees of emphasis on the magnetic fields and turbulence within the interstellar medium. One major difference in leading theories is the strength of the magnetic fields permeating the clouds and the extent to which they can provide support against cloud collapse. One way to determine the effect of magnetic fields is to determine the ratio between the gravitational and magnetic energies, called the mass-to-flux ratio, within the clouds to determine whether they are magnetically subcritical or supercritical. Much work has been done to determine this ratio in the cores of molecular clouds, but little is currently known about the fields in the envelopes of the clouds where most of the mass resides. We present the results of an extensive observational survey aimed at characterizing the fields in molecular clouds as a whole. We use the Arecibo telescope to determine mass-to-flux ratios in clouds distributed throughout the sky via the Zeeman effect in 18 cm OH absorption lines. This statistical study provides magnetic field and mass-to-flux results for 41 clouds located along 22 lines-of-sight. We find the first evidence for subcritical molecular gas along individual lines-of-sight, and a statistical analysis suggests that the mass-to-flux ratio in the envelopes of molecular clouds is approximately critical overall.

  5. Magnetic Behavior of a Dy8 Molecular Nanomagnet

    NASA Astrophysics Data System (ADS)

    Zhang, Qing; Sarachik, Myriam; Baker, Michael; Chen, Yizhang; Kent, Andrew; Stamatatos, Theocharis

    2015-03-01

    As part of a study of quantum tunneling in a newly synthesized family of dysprosium-based molecular magnets that exhibit a chiral spin structure, we report initial investigations of the magnetic response of a Dy8 cluster with the formula (Et4N)4[Dy8O(nd)8(NO3)10(H2O)2] .2MeCN. The molecular complex contains triangular arrangements of exchange coupled Dy(III) ions. The compound forms an approximate snub-square Archimedean lattice unit. The measured magnetization of this network of four triangles suggests the presence of multiple spin chiral vortexes. Single crystal susceptibility and magnetization measurements indicate the presence of a hard-axis direction and an easy plane. These principal orientations have been investigated in magnetic fields up to 5 Tesla for temperatures between 1.8 and 100 K using a SQUID-based Quantum Design MPMS magnetometer. Complex easy plane magnetic hysteresis loops emerge at lower temperatures measured using Hall probe magnetometry at sub 1 K temperatures. The analysis of these measurements will be discussed and compared with results of theoretical calculations. Work supported by ARO W911NF-13-1-1025 (CCNY), NSF-DMR-1309202 (NYU); the synthesis of the Dy8 cluster was supported by NSERC (Discovery grant to Th.C.S.).

  6. Low-temperature magnetization dynamics of magnetic molecular solids in a swept field

    NASA Astrophysics Data System (ADS)

    Lenferink, Erik; Vijayaraghavan, Avinash; Garg, Anupam

    2015-05-01

    The swept-field experiments on magnetic molecular solids such as Fe8 are studied using Monte Carlo simulations, and a kinetic equation developed to understand collective magnetization phenomena in such solids, where the collective aspects arise from dipole-dipole interactions between different molecules. Because of these interactions, the classic Landau-Zener-Stückelberg theory proves inadequate, as does another widely used model constructed by Kayanuma. It is found that the simulations provide a quantitatively accurate account of the experiments. The kinetic equation provides a similarly accurate account except at very low sweep velocities, where it fails modestly. This failure is attributed to the neglect of short-range correlations between the dipolar magnetic fields seen by the molecular spins. The simulations and the kinetic equation both provide a good understanding of the distribution of these dipolar fields, although analytic expressions for the final magnetization remain elusive.

  7. Low-temperature magnetization dynamics of magnetic molecular solids in a swept field

    SciTech Connect

    Lenferink, Erik; Vijayaraghavan, Avinash; Garg, Anupam

    2015-05-15

    The swept-field experiments on magnetic molecular solids such as Fe{sub 8} are studied using Monte Carlo simulations, and a kinetic equation developed to understand collective magnetization phenomena in such solids, where the collective aspects arise from dipole–dipole interactions between different molecules. Because of these interactions, the classic Landau–Zener–Stückelberg theory proves inadequate, as does another widely used model constructed by Kayanuma. It is found that the simulations provide a quantitatively accurate account of the experiments. The kinetic equation provides a similarly accurate account except at very low sweep velocities, where it fails modestly. This failure is attributed to the neglect of short-range correlations between the dipolar magnetic fields seen by the molecular spins. The simulations and the kinetic equation both provide a good understanding of the distribution of these dipolar fields, although analytic expressions for the final magnetization remain elusive.

  8. Molecular imaging using a targeted magnetic resonance hyperpolarized biosensor.

    PubMed

    Schröder, Leif; Lowery, Thomas J; Hilty, Christian; Wemmer, David E; Pines, Alexander

    2006-10-20

    A magnetic resonance approach is presented that enables high-sensitivity, high-contrast molecular imaging by exploiting xenon biosensors. These sensors link xenon atoms to specific biomolecular targets, coupling the high sensitivity of hyperpolarized nuclei with the specificity of biochemical interactions. We demonstrated spatial resolution of a specific target protein in vitro at micromolar concentration, with a readout scheme that reduces the required acquisition time by >3300-fold relative to direct detection. This technique uses the signal of free hyperpolarized xenon to dramatically amplify the sensor signal via chemical exchange saturation transfer (CEST). Because it is approximately 10,000 times more sensitive than previous CEST methods and other molecular magnetic resonance imaging techniques, it marks a critical step toward the application of xenon biosensors as selective contrast agents in biomedical applications. PMID:17053143

  9. Magnetic quantum coherence effect in Ni4 molecular transistors.

    PubMed

    González, Gabriel; Leuenberger, Michael N

    2014-07-01

    We present a theoretical study of electron transport in Ni4 molecular transistors in the presence of Zeeman spin splitting and magnetic quantum coherence (MQC). The Zeeman interaction is extended along the leads which produces gaps in the energy spectrum which allow electron transport with spin polarized along a certain direction. We show that the coherent states in resonance with the spin up or down states in the leads induces an effective coupling between localized spin states and continuum spin states in the single molecule magnet and leads, respectively. We investigate the conductance at zero temperature as a function of the applied bias and magnetic field by means of the Landauer formula, and show that the MQC is responsible for the appearence of resonances. Accordingly, we name them MQC resonances. PMID:24918902

  10. Two Models of Magnetic Support for Photoevaporated Molecular Clouds

    SciTech Connect

    Ryutov, D; Kane, J; Mizuta, A; Pound, M; Remington, B

    2004-05-05

    The thermal pressure inside molecular clouds is insufficient for maintaining the pressure balance at an ablation front at the cloud surface illuminated by nearby UV stars. Most probably, the required stiffness is provided by the magnetic pressure. After surveying existing models of this type, we concentrate on two of them: the model of a quasi-homogeneous magnetic field and the recently proposed model of a ''magnetostatic turbulence''. We discuss observational consequences of the two models, in particular, the structure and the strength of the magnetic field inside the cloud and in the ionized outflow. We comment on the possible role of reconnection events and their observational signatures. We mention laboratory experiments where the most significant features of the models can be tested.

  11. Ionization-regulated star formation in magnetized molecular clouds

    NASA Astrophysics Data System (ADS)

    Pudritz, Ralph E.; Silk, Joseph

    1987-05-01

    The authors present a theory for the early evolution of contracting magnetized flattened clouds in molecular clouds which undergo magnetic braking and field slip (ambipolar diffusion). If magnetic torques are the means by which angular momentum is removed from disks, then accretion rates and protostellar masses depend on how efficient braking is with respect to field line slip and hence can depend sensitively on ionization conditions. The authors discuss homologously evolving structures and calculate the evolution of the disk rotation frequency, toroidal field, accretion velocity, accretion rate, and core mass. It is found that cores which accrete out of very weakly ionized pancakes may have their masses increased by factors of 5 - 10 by increasing the ionization rate of the material by a decade.

  12. Anatomical, functional and molecular biomarker applications of magnetic resonance neuroimaging

    PubMed Central

    Liu, Christina H

    2015-01-01

    MRI and magnetic resonance spectroscopy (MRS) along with computed tomography and PET are the most common imaging modalities used in the clinics to detect structural abnormalities and pathological conditions in the brain. MRI generates superb image resolution/contrast without radiation exposure that is associated with computed tomography and PET; MRS and spectroscopic imaging technologies allow us to measure changes in brain biochemistry. Increasingly, neurobiologists and MRI scientists are collaborating to solve neuroscience problems across sub-cellular through anatomical levels. To achieve successful cross-disciplinary collaborations, neurobiologists must have sufficient knowledge of magnetic resonance principles and applications in order to effectively communicate with their MRI colleagues. This review provides an overview of magnetic resonance techniques and how they can be used to gain insight into the active brain at the anatomical, functional and molecular levels with the goal of encouraging neurobiologists to include MRI/MRS as a research tool in their endeavors. PMID:25774094

  13. Molecular lanthanide single-ion magnets: from bulk to submonolayers.

    PubMed

    Dreiser, J

    2015-05-13

    Single-ion magnets (SIMs) are mononuclear molecular complexes exhibiting slow relaxation of magnetization. They are currently attracting a lot of interest because of potential applications in spintronics and quantum information processing. However, exploiting SIMs in, e.g. molecule-inorganic hybrid devices requires a fundamental understanding of the effects of molecule-substrate interactions on the SIM magnetic properties. In this review the properties of lanthanide SIMs in the bulk crystalline phase and deposited on surfaces in the (sub)monolayer regime are discussed. As a starting point trivalent lanthanide ions in a ligand field will be described, and the challenges in characterizing the ligand field are illustrated with a focus on several spectroscopic techniques which are able to give direct information on the ligand-field split energy levels. Moreover, the dominant mechanisms of magnetization relaxation in the bulk phase are discussed followed by an overview of SIMs relevant for surface deposition. Further, a short introduction will be given on x-ray absorption spectroscopy, x-ray magnetic circular dichroism and scanning tunneling microscopy. Finally, the recent experiments on surface-deposited SIMs will be reviewed, along with a discussion of future perspectives. PMID:25893740

  14. Simulations of Supersonic Turbulence in Magnetized Molecular Clouds

    NASA Astrophysics Data System (ADS)

    Kritsuk, Alexei; Ustyugov, S. D.; Norman, M. L.; Padoan, P.

    2009-01-01

    We report first results from three-dimensional numerical simulations of supersonic magnetohydrodynamic (MHD) turbulence with the Piecewise Parabolic Method on Local Stencil (PPML, Popov & Ustyugov 2008). PPML is a multi-dimensional higher-order Godunov scheme that preserves monotonicity of solutions in the vicinity of strong discontinuities, and maintains zero divergence of the magnetic field through a constrained transport approach. The method is very accurate, extremely low-dissipation, and perfectly stable for super-Alfv'enic turbulence, where many other MHD schemes experience difficulties. We solve the equations of ideal MHD in a periodic domain on Cartesian grids of up to 1024^3 points. Our models describe driven turbulence at Mach 10 and assume an isothermal equation of state to mimic the conditions in molecular clouds. We start with uniform gas density and uniform magnetic field aligned with one of the coordinate directions and apply large-scale solenoidal force to develop a saturated turbulent state in a statistical equilibrium. Depending on the initial field strength, B_0, a saturation is reached within three-to-six dynamical times of driving. We then collect the turbulence statistics and compare those for different models. As predicted by Kritsuk et al. (2007), for weak initial fields we get Kolmogorov spectra for the density-weighted velocities ρ^{1/3}u. With stronger fields, the spectra tend to get shallower, but the -5/3 scaling still appears to hold (even in these highly compressible, magnetized flows) for a combination of kinetic and magnetic variables constructed in the spirit of Politano & Pouquet (1998). We compare PDFs, structure functions, and power spectra from runs with different B_0 and discuss the signature of magnetic field in the statistical properties of molecular cloud turbulence and their role in overall flow dynamics. This research was partially supported by NSF grants AST0607675, AST0808184, and by NRAC allocation MCA07S014. We

  15. Magnetic and electronic properties of porphyrin-based molecular nanowires

    NASA Astrophysics Data System (ADS)

    Zheng, Jia-Jia; Li, Qiao-Zhi; Dang, Jing-Shuang; Wang, Wei-Wei; Zhao, Xiang

    2016-01-01

    Using spin-polarized density functional theory calculations, we performed theoretical investigations on the electronic and magnetic properties of transition metal embedded porphyrin-based nanowires (TM-PNWs, TM = Cr, Mn, Co, Ni, Cu, and Zn). Our results indicate that Ni-PNW and Zn-PNW are nonmagnetic while the rest species are magnetic, and the magnetic moments in TM-PNWs and their corresponding isolated monomer structures are found to be the same. In addition, the spin coupling in the magnetic nanowires can be ignored leading to their degenerate AFM and FM states. These results can be ascribed to the weak intermetallic interactions because of the relatively large distances between neighbor TM atoms. Among all TM-PNW structures considered here, only Mn-PNW shows a half-metallic property while the others are predicted to be semiconducting. The present work paves a new way of obtaining ferromagnetic porphyrin-based nanowires with TM atoms distributed separately and orderly, which are expected to be good candidates for catalysts, energy storage and molecular spintronics.

  16. Molecular Magnetic Resonance Imaging of Tumor Response to Therapy

    PubMed Central

    Shuhendler, Adam J.; Ye, Deju; Brewer, Kimberly D.; Bazalova-Carter, Magdalena; Lee, Kyung-Hyun; Kempen, Paul; Dane Wittrup, K.; Graves, Edward E.; Rutt, Brian; Rao, Jianghong

    2015-01-01

    Personalized cancer medicine requires measurement of therapeutic efficacy as early as possible, which is optimally achieved by three-dimensional imaging given the heterogeneity of cancer. Magnetic resonance imaging (MRI) can obtain images of both anatomy and cellular responses, if acquired with a molecular imaging contrast agent. The poor sensitivity of MRI has limited the development of activatable molecular MR contrast agents. To overcome this limitation of molecular MRI, a novel implementation of our caspase-3-sensitive nanoaggregation MRI (C-SNAM) contrast agent is reported. C-SNAM is triggered to self-assemble into nanoparticles in apoptotic tumor cells, and effectively amplifies molecular level changes through nanoaggregation, enhancing tissue retention and spin-lattice relaxivity. At one-tenth the current clinical dose of contrast agent, and following a single imaging session, C-SNAM MRI accurately measured the response of tumors to either metronomic chemotherapy or radiation therapy, where the degree of signal enhancement is prognostic of long-term therapeutic efficacy. Importantly, C-SNAM is inert to immune activation, permitting radiation therapy monitoring. PMID:26440059

  17. Unskilled Writers as Composers.

    ERIC Educational Resources Information Center

    Perl, Sondra

    1979-01-01

    Composition is not a straightforward, linear process; it involves a creative search for meaning that becomes clear only as the writer engages in the composing process. This suggests that teaching not dwell on the correctness of the finished product. (Author/SJL)

  18. Decomposing Composing Conventions.

    ERIC Educational Resources Information Center

    Beers, Terry

    Recent research has invited critiques of the authoritative descriptions of composing found in many rhetoric textbooks. The concept of "convention" may be especially useful in rethinking the teleological basis of these textbook descriptions. Conventions found in composition textbooks need to be unmasked as arbitrary concepts which serve to…

  19. Composing a Research Life

    ERIC Educational Resources Information Center

    Cochran-Smith, Marilyn

    2012-01-01

    In this article about her early career development and the experiences that shaped her life as a scholar and researcher, the author describes the work lives of university-based teacher educators and what it means to compose a research life in this field. This article draws on the author's 30 years as a university-based teacher educator. In it, she…

  20. Molecular Cardiovascular Magnetic Resonance: Current Status and Future Prospects.

    PubMed

    Bender, Yvonne Y; Pfeifer, Andreas; Ebersberger, Hans U; Diederichs, Gerd; Hoppe, Peter; Hamm, Bernd; Botnar, René M; Makowski, Marcus R

    2016-05-01

    In the Western world and developing countries, the number one causes of mortality and morbidity result from cardiovascular diseases. Cardiovascular diseases represent a wide range of pathologies, including myocardial infarction, peripheral vascular disease, and cerebrovascular disease, which are all linked by a common cause - atherosclerosis. Currently, the diagnosis of atherosclerosis is in most cases established at the end stage of the disease, when patients are administered to the emergency room due to a myocardial infarction or stroke. Even though cardiovascular diseases have an enormous impact on society, there are still limitations in the early diagnosis and the prevention of the disease. Current imaging methods mainly focus on morphological changes that occur at an advanced disease stage, e.g., degree of stenosis. Cardiovascular magnetic resonance imaging and specifically molecular cardiovascular magnetic resonance imaging are capable to reveal pathophysiological changes already occurring during early atherosclerotic plaque formation. This allows for the assessment of cardiovascular disease on a level, which goes beyond morphological or anatomical criteria. In this review, we will introduce promising MR-based molecular imaging strategies for the non-invasive assessment of cardiovascular disease. PMID:27038612

  1. Light absorption and plasmon - exciton interaction in three-layer nanorods with a gold core and outer shell composed of molecular J- and H-aggregates of dyes

    NASA Astrophysics Data System (ADS)

    Shapiro, B. I.; Tyshkunova, E. S.; Kondorskiy, A. D.; Lebedev, V. S.

    2015-12-01

    Optical properties of hybrid rod-like nanoparticles, consisting of a gold core, an intermediate passive organic layer (spacer) and outer layer of ordered molecular cyanine dye aggregates, are experimentally and theoretically investigated. It is shown that these dyes can form not only ordered J-aggregates but also H-aggregates (differing by the packing angle of dye molecules in an aggregate and having other spectral characteristics) in the outer shell of the hybrid nanostructure. Absorption spectra of synthesised three-layer nanorods are recorded, and their sizes are determined. The optical properties of the composite nanostructures under study are found to differ significantly, depending on the type of the molecular aggregate formed in the outer shell. The experimental data are quantitatively explained based on computer simulation using the finite-difference time-domain (FDTD) method, and characteristic features of the plasmon - exciton interaction in the systems under study are revealed.

  2. Molecular cloud formation in high-shear, magnetized colliding flows

    NASA Astrophysics Data System (ADS)

    Fogerty, E.; Frank, A.; Heitsch, F.; Carroll-Nellenback, J.; Haig, C.; Adams, M.

    2016-08-01

    The colliding flows (CF) model is a well-supported mechanism for generating molecular clouds. However, to-date most CF simulations have focused on the formation of clouds in the normal-shock layer between head-on colliding flows. We performed simulations of magnetized colliding flows that instead meet at an oblique-shock layer. Oblique shocks generate shear in the post-shock environment, and this shear creates inhospitable environments for star formation. As the degree of shear increases (i.e. the obliquity of the shock increases), we find that it takes longer for sink particles to form, they form in lower numbers, and they tend to be less massive. With regard to magnetic fields, we find that even a weak field stalls gravitational collapse within forming clouds. Additionally, an initially oblique collision interface tends to reorient over time in the presence of a magnetic field, so that it becomes normal to the oncoming flows. This was demonstrated by our most oblique shock interface, which became fully normal by the end of the simulation.

  3. Molecular magnetic resonance imaging of brain–immune interactions

    PubMed Central

    Gauberti, Maxime; Montagne, Axel; Quenault, Aurélien; Vivien, Denis

    2014-01-01

    Although the blood–brain barrier (BBB) was thought to protect the brain from the effects of the immune system, immune cells can nevertheless migrate from the blood to the brain, either as a cause or as a consequence of central nervous system (CNS) diseases, thus contributing to their evolution and outcome. Accordingly, as the interface between the CNS and the peripheral immune system, the BBB is critical during neuroinflammatory processes. In particular, endothelial cells are involved in the brain response to systemic or local inflammatory stimuli by regulating the cellular movement between the circulation and the brain parenchyma. While neuropathological conditions differ in etiology and in the way in which the inflammatory response is mounted and resolved, cellular mechanisms of neuroinflammation are probably similar. Accordingly, neuroinflammation is a hallmark and a decisive player of many CNS diseases. Thus, molecular magnetic resonance imaging (MRI) of inflammatory processes is a central theme of research in several neurological disorders focusing on a set of molecules expressed by endothelial cells, such as adhesion molecules (VCAM-1, ICAM-1, P-selectin, E-selectin, …), which emerge as therapeutic targets and biomarkers for neurological diseases. In this review, we will present the most recent advances in the field of preclinical molecular MRI. Moreover, we will discuss the possible translation of molecular MRI to the clinical setting with a particular emphasis on myeloperoxidase imaging, autologous cell tracking, and targeted iron oxide particles (USPIO, MPIO). PMID:25505871

  4. Signatures of molecular magnetism in single-molecule transport spectroscopy.

    PubMed

    Jo, Moon-Ho; Grose, Jacob E; Baheti, Kanhayalal; Deshmukh, Mandar M; Sokol, Jennifer J; Rumberger, Evan M; Hendrickson, David N; Long, Jeffrey R; Park, Hongkun; Ralph, D C

    2006-09-01

    We report single-molecule-transistor measurements on devices incorporating magnetic molecules. By studying the electron-tunneling spectrum as a function of magnetic field, we are able to identify signatures of magnetic states and their associated magnetic anisotropy. A comparison of the data to simulations also suggests that sequential electron tunneling may enhance the magnetic relaxation of the magnetic molecule. PMID:16968018

  5. Spin-polarized current of a transistor in single Mn12 molecular magnets.

    PubMed

    Park, Joonho; Yang, Heok; Park, K S; Lee, Eok-Kyun

    2007-11-01

    Focusing on the framework of how to realize the molecular spintronics in a single molecular magnet, we present theoretical studies on the spin-polarized quantum transport behavior through a single Mn12 molecular magnet. Our theoretical results were obtained by carrying out density functional theoretical calculation within the Keldysh nonequilibrium Green function formalism. The ultimate goal of the molecular spintronics is to develop single molecule transistors which generate spin-polarized currents through the molecular magnet. We obtained the density of states, the transmission coefficients and the characteristic features of the current-voltage (I-V) on the spin-polarized transport properties of Mn12 by the theoretical calculation. These results show the possibility for the realization of molecular spintroinics using single molecular magnets. PMID:18047130

  6. Synthesis and characterization of low-dimensional molecular magnetic materials

    NASA Astrophysics Data System (ADS)

    Liu, Chen

    This dissertation presents experimental results from the synthesis and structural, magnetic characterization of representative low-dimensional molecule-based magnetic materials. Most of the materials reported in this dissertation, both coordination polymers and cuprate, are obtained as the result of synthesizing and characterizing spin ladder systems; except the material studied in Chapter 2, ferricenyl(III)trisferrocenyl(II)borate, which is not related to the spin ladder project. The interest in spin ladder systems is due to the discovery of high-temperature superconductivity in doped cuprates possessing ladder-like structures, and it is hoped that investigation of the magnetic behavior of ladder-like structures will help us understand the mechanism of high-temperature superconductivity. Chapter 1 reviews fundamental knowledge of molecular magnetism, general synthetic strategies for low-dimensional coordination polymers, and a brief introduction to the current status of research on spin ladder systems. Chapter 2 presents a modified synthetic procedure of a previously known monomeric complex, ferricenyl(III)trisferrocenyl(II)borate, 1. Its magnetic properties were characterized and previous results have been disproved. Chapter 3 investigates the magnetism of [CuCl2(CH3CN)] 2, 2, a cuprate whose structure consists of isolated noninterpenetrating ladders formed by the stacking of Cu(II) dimers. This material presents an unexpected ferromagnetic interaction both within the dimeric units and between the dimers, and this behavior has been rationalized based on the effect of its terminal nonbridging ligands. In Chapter 4, the synthesis and magnetism of two ladder-like coordination polymers, [Co(NO3)2(4,4'-bipyridine) 1.5(MeCN)]n, 3, and Ni2(2,6-pyridinedicarboxylic acid)2(H2O)4(pyrazine), 4, are reported. Compound 3 possesses a covalent one-dimensional ladder structure in which Co(II) ions are bridged through bipyridine molecules. Compared to the materials discussed in

  7. DISPERSION OF MAGNETIC FIELDS IN MOLECULAR CLOUDS. III

    SciTech Connect

    Houde, Martin; Rao, Ramprasad; Vaillancourt, John E.; Hildebrand, Roger H.

    2011-06-01

    We apply our technique on the dispersion of magnetic fields in molecular clouds to high spatial resolution Submillimeter Array polarization data obtained for Orion KL in OMC-1, IRAS 16293, and NGC 1333 IRAS 4A. We show how one can take advantage of such high-resolution data to characterize the magnetized turbulence power spectrum in the inertial and dissipation ranges. For Orion KL we determine that in the inertial range the spectrum can be approximately fitted with a power law k{sup -(2.9{+-}0.9)} and we report a value of 9.9 mpc for {lambda}{sub AD}, the high spatial frequency cutoff presumably due to turbulent ambipolar diffusion. For the same parameters we have {approx}k{sup -(1.4{+-}0.4)} and a tentative value of {lambda}{sub AD} {approx_equal} 2.2 mpc for NGC 1333 IRAS 4A, and {approx}k{sup -(1.8{+-}0.3)} with an upper limit of {lambda}{sub AD} {approx}< 1.8 mpc for IRAS 16293. We also discuss the application of the technique to interferometry measurements and the effects of the inherent spatial filtering process on the interpretation of the results.

  8. Magnetic fingerprint of individual Fe4 molecular magnets under compression by a scanning tunnelling microscope.

    PubMed

    Burgess, Jacob A J; Malavolti, Luigi; Lanzilotto, Valeria; Mannini, Matteo; Yan, Shichao; Ninova, Silviya; Totti, Federico; Rolf-Pissarczyk, Steffen; Cornia, Andrea; Sessoli, Roberta; Loth, Sebastian

    2015-01-01

    Single-molecule magnets (SMMs) present a promising avenue to develop spintronic technologies. Addressing individual molecules with electrical leads in SMM-based spintronic devices remains a ubiquitous challenge: interactions with metallic electrodes can drastically modify the SMM's properties by charge transfer or through changes in the molecular structure. Here, we probe electrical transport through individual Fe4 SMMs using a scanning tunnelling microscope at 0.5 K. Correlation of topographic and spectroscopic information permits identification of the spin excitation fingerprint of intact Fe4 molecules. Building from this, we find that the exchange coupling strength within the molecule's magnetic core is significantly enhanced. First-principles calculations support the conclusion that this is the result of confinement of the molecule in the two-contact junction formed by the microscope tip and the sample surface. PMID:26359203

  9. Magnetic fingerprint of individual Fe4 molecular magnets under compression by a scanning tunnelling microscope

    NASA Astrophysics Data System (ADS)

    Burgess, Jacob A. J.; Malavolti, Luigi; Lanzilotto, Valeria; Mannini, Matteo; Yan, Shichao; Ninova, Silviya; Totti, Federico; Rolf-Pissarczyk, Steffen; Cornia, Andrea; Sessoli, Roberta; Loth, Sebastian

    2015-09-01

    Single-molecule magnets (SMMs) present a promising avenue to develop spintronic technologies. Addressing individual molecules with electrical leads in SMM-based spintronic devices remains a ubiquitous challenge: interactions with metallic electrodes can drastically modify the SMM's properties by charge transfer or through changes in the molecular structure. Here, we probe electrical transport through individual Fe4 SMMs using a scanning tunnelling microscope at 0.5 K. Correlation of topographic and spectroscopic information permits identification of the spin excitation fingerprint of intact Fe4 molecules. Building from this, we find that the exchange coupling strength within the molecule's magnetic core is significantly enhanced. First-principles calculations support the conclusion that this is the result of confinement of the molecule in the two-contact junction formed by the microscope tip and the sample surface.

  10. Magnetic fingerprint of individual Fe4 molecular magnets under compression by a scanning tunnelling microscope

    PubMed Central

    Burgess, Jacob A.J.; Malavolti, Luigi; Lanzilotto, Valeria; Mannini, Matteo; Yan, Shichao; Ninova, Silviya; Totti, Federico; Rolf-Pissarczyk, Steffen; Cornia, Andrea; Sessoli, Roberta; Loth, Sebastian

    2015-01-01

    Single-molecule magnets (SMMs) present a promising avenue to develop spintronic technologies. Addressing individual molecules with electrical leads in SMM-based spintronic devices remains a ubiquitous challenge: interactions with metallic electrodes can drastically modify the SMM's properties by charge transfer or through changes in the molecular structure. Here, we probe electrical transport through individual Fe4 SMMs using a scanning tunnelling microscope at 0.5 K. Correlation of topographic and spectroscopic information permits identification of the spin excitation fingerprint of intact Fe4 molecules. Building from this, we find that the exchange coupling strength within the molecule's magnetic core is significantly enhanced. First-principles calculations support the conclusion that this is the result of confinement of the molecule in the two-contact junction formed by the microscope tip and the sample surface. PMID:26359203

  11. Process of timbral composing

    NASA Astrophysics Data System (ADS)

    Withrow, Sam

    In this paper, I discuss the techniques and processes of timbral organization I developed while writing my chamber work, Afterimage. I compare my techniques with illustrative examples by other composers to place my work in historical context. I examine three elements of my composition process. The first is the process of indexing and cataloging basic sonic materials. The second consists of the techniques and mechanics of manipulating and assembling these collections into larger scale phrases, textures, and overall form in a musical work. The third element is the more elusive, and often extra-musical, source of inspiration and motivation. The evocative power of tone color is both immediately evident yet difficult to explain. What is timbre? This question cannot be answered solely in scientific terms; subjective factors affect our perception of it.

  12. High temperature spin dynamics in linear magnetic chains, molecular rings, and segments by nuclear magnetic resonance

    SciTech Connect

    Adelnia, Fatemeh; Lascialfari, Alessandro; Mariani, Manuel; Ammannato, Luca; Caneschi, Andrea; Rovai, Donella; Winpenny, Richard; Timco, Grigore; Corti, Maurizio Borsa, Ferdinando

    2015-05-07

    We present the room temperature proton nuclear magnetic resonance (NMR) nuclear spin-lattice relaxation rate (NSLR) results in two 1D spin chains: the Heisenberg antiferromagnetic (AFM) Eu(hfac){sub 3}NITEt and the magnetically frustrated Gd(hfac){sub 3}NITEt. The NSLR as a function of external magnetic field can be interpreted very well in terms of high temperature spin dynamics dominated by a long time persistence of the decay of the two-spin correlation function due to the conservation of the total spin value for isotropic Heisenberg chains. The high temperature spin dynamics are also investigated in Heisenberg AFM molecular rings. In both Cr{sub 8} closed ring and in Cr{sub 7}Cd and Cr{sub 8}Zn open rings, i.e., model systems for a finite spin segment, an enhancement of the low frequency spectral density is found consistent with spin diffusion but the high cut-off frequency due to intermolecular anisotropic interactions prevents a detailed analysis of the spin diffusion regime.

  13. Toxoplasma gondii DNA detection with a magnetic molecular beacon probe

    NASA Astrophysics Data System (ADS)

    Xu, Shichao; Yao, Cuicui; Wei, Shuoming; Zhang, Jimei; Dai, Zhao; Zheng, Guo; Sun, Bo; Han, Qing; Hu, Fei; Zhou, Hongming

    2008-12-01

    Toxoplasma Gondii infection is widespread in humans worldwide and reported infection rates range from 3%-70%, depending on the populations or geographic areas, and it has been recognized as a potential food safety hazard in our daily life. A magnetic molecular beacon probe (mMBP), based on theory of fluorescence resonance energy transfer (FRET), was currently reported to detect Toxoplasma Gondii DNA. Nano-sized Fe3O4 were primarily prepared by coprecipitation method in aqueous phase with NaOH as precipitator, and was used as magnetic core. The qualified coreshell magnetic quantum dots (mQDs), i.e. CdTe(symbol)Fe3O4, were then achieved by layer-by-layer method when mol ratio of Fe3O4/CdTe is 1/3, pH at 6.0, 30 °C, and reactant solution was refluxed for 30 min, the size of mQDs were determined to be 12-15 nm via transmission electron microscopy (TEM). Over 70% overlap between emission spectrum of mQDs and absorbance spectrum of BHQ-2 was observed, this result suggests the synthesized mQDs and BHQ-2 can be utilized as energy donor and energy acceptor, respectively. The sensing probe was fabricated and a stem-loop Toxoplasma Gondii DNA oligonucleotide was labeled with mQDs at the 5' end and BHQ-2 at 3' end, respectively. Target Toxoplasma gondii DNA was detected under conditions of 37 °C, hybridization for 2h, at pH8.0 in Tris-HCl buffer. About 30% recovery of fluorescence intensity was observed via fluorescence spectrum (FS) after the Toxoplasma gondii DNA was added, which suggested that the Toxoplasma Gondii DNA was successfully detected. Specificity investigation of the mMBP indicated that relative low recovery of fluorescence intensity was obtained when the target DNA with one-base pair mismatch was added, this result indicated the high specificity of the sensing probe. Our research simultaneously indicated that mMBP can be conveniently separated from the unhybridized stem-loop DNA and target DNA, which will be meaningful in DNA sensing and purification process.

  14. Molecular dynamics and composition of crude oil by low-field nuclear magnetic resonance.

    PubMed

    Jia, Zijian; Xiao, Lizhi; Wang, Zhizhan; Liao, Guangzhi; Zhang, Yan; Liang, Can

    2016-08-01

    Nuclear magnetic resonance (NMR) techniques are widely used to identify pure substances and probe protein dynamics. Oil is a complex mixture composed of hydrocarbons, which have a wide range of molecular size distribution. Previous work show that empirical correlations of relaxation times and diffusion coefficients were found for simple alkane mixtures, and also the shape of the relaxation and diffusion distribution functions are related to the composition of the fluids. The 2D NMR is a promising qualitative evaluation method for oil composition. But uncertainty in the interpretation of crude oil indicated further study was required. In this research, the effect of each composition on relaxation distribution functions is analyzed in detail. We also suggest a new method for prediction of the rotational correlation time distribution of crude oil molecules using low field NMR (LF-NMR) relaxation time distributions. A set of down-hole NMR fluid analysis system is independently designed and developed for fluid measurement. We illustrate this with relaxation-relaxation correlation experiments and rotational correlation time distributions on a series of hydrocarbon mixtures that employ our laboratory-designed downhole NMR fluid analyzer. The LF-NMR is a useful tool for detecting oil composition and monitoring oil property changes. Copyright © 2016 John Wiley & Sons, Ltd. PMID:26990450

  15. Molecular nanomagnets as contrast agents for Magnetic Resonance Imaging

    NASA Astrophysics Data System (ADS)

    Rodríguez, Elisenda; Roig, Anna; Molins, Elies; Arús, Carles; Cabañas, Miquel; Quintero, María Rosa; Cerdán, Sebastián; Sanfeliu, Coral

    2003-03-01

    Magnetic resonance imaging (MRI) is a non-invasive technique used in medicine to produce high quality images of human body slices. In order to enhance the contrast between different organs or to reveal altered portions of them such necrosis or tumors, the administration of a contrast agent is highly convenient. Currently Gd-DTPA, a paramagnetic complex, is the most widely administered compound. In this context, we have assayed molecular nanomagnets as MRI contrast agents. The complex [(tacn)_6Fe_8(μ_3-O)_2(μ_2-OH)_12]Br_8·9H_2O^1(Fe8 in brief) has been evaluated and shorter relaxation times, T1 and T_2, have been obtained for Fe8 than those obtained for the commercial Gd-DTPA. No toxic effects have been observed at concentrations up to 1 mM of Fe8 in cultured cells. Phantom studies with T_1-weighted MRI at 9.4 Tesla suggest that Fe8 can have potentiality as T_1-contrast agent. ^1Wieghardt K Angew Chem Intl Ed Engl 23 1 (1984) 77

  16. Solid-State Molecular Nanomagnet Inclusion into a Magnetic Metal-Organic Framework: Interplay of the Magnetic Properties.

    PubMed

    Mon, Marta; Pascual-Álvarez, Alejandro; Grancha, Thais; Cano, Joan; Ferrando-Soria, Jesús; Lloret, Francesc; Gascon, Jorge; Pasán, Jorge; Armentano, Donatella; Pardo, Emilio

    2016-01-11

    Single-ion magnets (SIMs) are the smallest possible magnetic devices and are a controllable, bottom-up approach to nanoscale magnetism with potential applications in quantum computing and high-density information storage. In this work, we take advantage of the promising, but yet insufficiently explored, solid-state chemistry of metal-organic frameworks (MOFs) to report the single-crystal to single-crystal inclusion of such molecular nanomagnets within the pores of a magnetic MOF. The resulting host-guest supramolecular aggregate is used as a playground in the first in-depth study on the interplay between the internal magnetic field created by the long-range magnetic ordering of the structured MOF and the slow magnetic relaxation of the SIM. PMID:26603579

  17. Colloidal Suspensions of Rodlike Nanocrystals and Magnetic Spheres under an External Magnetic Stimulus: Experiment and Molecular Dynamics Simulation.

    PubMed

    May, Kathrin; Eremin, Alexey; Stannarius, Ralf; Peroukidis, Stavros D; Klapp, Sabine H L; Klein, Susanne

    2016-05-24

    Using experiments and molecular dynamics simulations, we explore magnetic field-induced phase transformations in suspensions of nonmagnetic rodlike and magnetic sphere-shaped particles. We experimentally demonstrate that an external uniform magnetic field causes the formation of small, stable clusters of magnetic particles that, in turn, induce and control the orientational order of the nonmagnetic subphase. Optical birefringence was studied as a function of the magnetic field and the volume fractions of each particle type. Steric transfer of the orientational order was investigated by molecular dynamics (MD) simulations; the results are in qualitative agreement with the experimental observations. By reproducing the general experimental trends, the MD simulation offers a cohesive bottom-up interpretation of the physical behavior of such systems, and it can also be regarded as a guide for further experimental research. PMID:27119202

  18. Teaching Composing with an Identity as a Teacher-Composer

    ERIC Educational Resources Information Center

    Francis, Jennie

    2012-01-01

    I enjoy composing and feel able to write songs that I like and which feel significant to me. This has not always been the case and the change had nothing to do with my school education or my degree. Composing at secondary school did not move beyond Bach and Handel pastiche. I did not take any composing courses during my degree. What did influence…

  19. Unconventional Magnetic and Resistive Hysteresis in an Iodine-Bonded Molecular Conductor.

    PubMed

    Kawaguchi, Genta; Maesato, Mitsuhiko; Komatsu, Tokutaro; Kitagawa, Hiroshi; Imakubo, Tatsuro; Kiswandhi, Andhika; Graf, David; Brooks, James S

    2015-08-24

    Simultaneous manipulation of both spin and charge is a crucial issue in magnetic conductors. We report on a strong correlation between magnetism and conductivity in the iodine-bonded molecular conductor (DIETSe)2 FeBr2 Cl2 [DIETSe=diiodo(ethylenedithio)tetraselenafulvalene], which is the first molecular conductor showing a large hysteresis in both magnetic moment and magnetoresistance associated with a spin-flop transition. Utilizing a mixed-anion approach and iodine bonding interactions, we tailored a molecular conductor with random exchange interactions exhibiting unforeseen physical properties. PMID:26179678

  20. Magnetic proximity effect in ferrimagnetic-ferromagnetic core-shell Prussian blue analogues molecular magnet

    NASA Astrophysics Data System (ADS)

    Bhatt, Pramod; Kumar, Amit; Meena, S. S.; Mukadam, M. D.; Yusuf, S. M.

    2016-05-01

    A magnetic proximity effect has been observed in core-shell structure of molecular magnet, Mn1.5[Cr(CN)6]·mH2O@Ni1.5[Cr(CN)6]·nH2O, synthesized using a ferrimagnetic core of Mn1.5[Cr(CN)6]·7.5H2O surrounded by a ferromagnetic shell of Ni1.5[Cr(CN)6]·7.5H2O. The values of Curie temperature (TC) are found to be of ∼65 and ∼60 K for the bare-core and bare-shell compounds, respectively. However, an enhanced TC (∼70 K) has been observed for the core-shell structure. The proximity effect (due to presence of interface exchange coupling) between core and shell is responsible for the observed enhancement of TC. A neutron depolarization study also confirms finite depolarization below ∼70 K.

  1. Composing the Curriculum: Teacher Identity

    ERIC Educational Resources Information Center

    Lewis, Rebecca

    2012-01-01

    What is composing and how is it valued? What does a good education in composing look like; what constraints hinder it and is it possible to overcome such constraints? Can composing be a personal, creative and valuable activity for the school student? What role does the teacher play in all of this? These are questions that I discuss in this…

  2. Electronic and magnetic properties of silicon supported organometallic molecular wires: a density functional theory (DFT) study.

    PubMed

    Liu, Xia; Tan, Yingzi; Li, Xiuling; Wu, Xiaojun; Pei, Yong

    2015-08-28

    The electronic and magnetic properties of transition metal (TM = Sc, Ti, V, Cr and Mn) atom incorporated single and double one-dimensional (1D) styrene molecular wires confined on the hydrogen-terminated Si(100) surface are explored for the first time by means of spin-polarized density functional theory, denoted as Si-[TM(styrene)]. It is unveiled that TM atoms bind asymmetrically to the adjacent phenyl rings, which leads to novel electronic and magnetic properties in stark contrast to the well-studied gas phase TM-benzene molecular wires. Si-[Mn(styrene)]∞ and Si-[Cr(styrene)]∞ single molecular wires (SMWs) are a ferromagnetic semiconductor and half metal, respectively. Creation of H-atom defects on the silicon surface can introduce an impurity metallic band, which leads to novel half-metallic magnetism of a Si-[Mn(styrene)]∞ system. Moreover, double molecular wires (DMWs) containing two identical or hetero SMWs are theoretically designed. The [Mn(styrene)]∞-[Cr(styrene)]∞ DMW exhibits half-metallic magnetism where the spin-up and spin-down channels are contributed by two single molecular wires. Finally, we demonstrate that introducing a TM-defect may significantly affect the electronic structure and magnetic properties of molecular wires. These studies provide new insights into the structure and properties of surface supported 1-D sandwiched molecular wires and may inspire the future experimental synthesis of substrate confined organometallic sandwiched molecular wires. PMID:26219748

  3. A wide-open molecular magnetic trap for collision studies

    NASA Astrophysics Data System (ADS)

    Stuhl, Benjamin; Sawyer, Brian; Yeo, Mark; Wang, Dajun; Lev, Benjamin; Ye, Jun

    2008-05-01

    Cold molecular collision studies hold the potential of revolutionizing our understanding of chemical and molecular dynamics, both on Earth and astrophysically. Toward this end, we have developed and implemented a magneto-electrostatic trap with near-360 circumferential access for optical or molecular beam probes. The trap has demonstrated almost optimal loading efficiency, yielding a trapped density of 10^6 cm-3 at a temperature of 70 mK. We also report further progress towards the goal of cold molecular collisions.

  4. TOPICAL REVIEW: New aspects of π-d interactions in magnetic molecular conductors

    NASA Astrophysics Data System (ADS)

    Sugimoto, Toyonari; Fujiwara, Hideki; Noguchi, Satoru; Murata, Keizo

    2009-04-01

    The 2 : 1 cation radical salts of bent donor molecules of ethylenedithio-tetrathiafulvalenoquinone-1,3-dithiolemethide (EDT-TTFVO), ethylenedithio-diselenadithiafulvalenoquinone-1,3-dithiolemethide (EDT-DSDTFVO), ethylenedithio-diselenadithiafulvalenothioquinone-1,3-diselenolemethide (EDT-DSDTFVSDS), ethylenedioxy-tetrathiafulvalenoquinone-1,3-dithiolemethide (EDO-TTFVO) and ethylenedioxy-tetrathiafulvalenoquinone-1,3-diselenolemethide (EDO-TTFVODS) with FeX4- (X = Cl, Br) ions are prepared by electrocrystallization. The crystal structures of these salts are composed of alternately stacked donor molecule and magnetic anion layers. The band structures of the donor molecule layers are calculated using the overlap integrals between neighboring donor molecules and are compared with the observed electronic transport properties. The magnetic ordering of the Fe(III) d spins of FeX4- ions is determined from magnetization and heat capacity measurements. The magnetic ordering temperatures are estimated by considering a combination of a direct d-d interaction between the d spins and an indirect π-d interaction between the conduction π electron and the d spins, whose magnitudes are separately calculated from the crystal structures with an extended Hückel molecular orbital method. The occurrence of a π-d interaction is proved by the negative magnetoresistance, and the magnitude of magnetoresistance reflects the strength of the π-d interaction. The effect of pressure on the magnetoresistance is studied, and the result indicates that the magnitude of magnetoresistance increases, namely, the π-d interaction is enhanced with increasing pressure. From these experimental results it is shown that (EDT-TTFVO)2•FeBr4 is a ferromagnetic semiconductor, (EDT-DSDTFVO)2•FeX4 (X = Cl, Br) and (EDT-DSDTFVSDS)2•FeBr4 are metals exhibiting antiferromagnetic ordering of the d spins, and (EDO-TTFVO)2•FeCl4 and (EDO-TTFVODS)2•FeBr4•(DCE)0.5 (DCE =-dichloroethane) are genuine

  5. Magnetic bistability and thermochromism in a molecular Cu(II) chain.

    PubMed

    Setifi, Fatima; Benmansour, Samia; Marchivie, Mathieu; Dupouy, Gaëlle; Triki, Smail; Sala-Pala, Jean; Salaün, Jean-Yves; Gómez-García, Carlos J; Pillet, Sébastien; Lecomte, Claude; Ruiz, Eliseo

    2009-02-16

    An original magnetic bistability and a thermochromic transition are observed in a new Cu(II) molecular chain. Thermal structural studies reveal changes in the Cu(II) coordination sphere, driven by a more pronounced Jahn-Teller effect at low temperature. These distortions provoke a gradual color change. The structural study at 10 K shows a dimerization of the molecular chain, in agreement with the abrupt magnetic transition observed at 30 K. PMID:19166286

  6. Exchange bias and room-temperature magnetic order in molecular layers

    NASA Astrophysics Data System (ADS)

    Gruber, Manuel; Ibrahim, Fatima; Boukari, Samy; Isshiki, Hironari; Joly, Loïc; Peter, Moritz; Studniarek, Michał; da Costa, Victor; Jabbar, Hashim; Davesne, Vincent; Halisdemir, Ufuk; Chen, Jinjie; Arabski, Jacek; Otero, Edwige; Choueikani, Fadi; Chen, Kai; Ohresser, Philippe; Wulfhekel, Wulf; Scheurer, Fabrice; Weber, Wolfgang; Alouani, Mebarek; Beaurepaire, Eric; Bowen, Martin

    2015-10-01

    Molecular semiconductors may exhibit antiferromagnetic correlations well below room temperature. Although inorganic antiferromagnetic layers may exchange bias single-molecule magnets, the reciprocal effect of an antiferromagnetic molecular layer magnetically pinning an inorganic ferromagnetic layer through exchange bias has so far not been observed. We report on the magnetic interplay, extending beyond the interface, between a cobalt ferromagnetic layer and a paramagnetic organic manganese phthalocyanine (MnPc) layer. These ferromagnetic/organic interfaces are called spinterfaces because spin polarization arises on them. The robust magnetism of the Co/MnPc spinterface stabilizes antiferromagnetic ordering at room temperature within subsequent MnPc monolayers away from the interface. The inferred magnetic coupling strength is much larger than that found in similar bulk, thin or ultrathin systems. In addition, at lower temperature, the antiferromagnetic MnPc layer induces an exchange bias on the Co film, which is magnetically pinned. These findings create new routes towards designing organic spintronic devices.

  7. Synthesis and properties of core-shell magnetic molecular imprinted polymers

    NASA Astrophysics Data System (ADS)

    Chang, Limin; Chen, Shaona; Li, Xin

    2012-06-01

    A general fabricating protocol for the preparation of core-shell magnetic molecularly imprinted polymers (MIPs) for chlorinated phenols recognition is described. In this protocol, Fe3O4 magnetic nanoparticles were first prepared using the chemical co-precipitation method. Then, the obtained magnetic nanoparticles were coated with a silica shell through modified Stöber method. Finally, MIP films were coated onto the surface of silica-modified magnetic nanoparticles by surface molecular imprinting technique. The resultant polymers showed a high saturation magnetization value (31.350 emu g-1), and short response time (30 s). Meanwhile, the as-synthesized magnetic MIPs showed an excellent recognition and selection properties toward imprinted molecule over structurally related compounds.

  8. Preparation and Application of Novel Magnetic Molecularly Imprinted Composites for Recognition of Sulfadimethoxine in Feed Samples.

    PubMed

    Feng, Min; Li, Hengye; Zhang, Lin; Zhang, Jingyou; Dai, Jianping; Wang, Xiaojin; Zhang, Lingli; Wei, Yunji

    2016-01-01

    Novel magnetic molecularly imprinted composites were prepared through a facile method using sulfadimethoxine (SDM) as template. The inorganic magnetic nanoparticles were linked with the organic molecularly imprinted polymer (MIP) through irreversibly covalent bond. So, the resulted composites showed excellent stability and reusability under acidic elution conditions. The magnetic MIP composites showed good selectivity, high binding capacity and excellent kinetics toward SDM. Adopting the magnetic MIP composites as extraction material, an off-line magnetic solid-phase extraction (SPE)/high performance liquid chromatography (HPLC) method was established. The calibration curve was linear in the range of 0.05 - 15 mg kg(-1) (r(2) = 0.9976). The LOD and LOQ were 0.016 and 0.052 mg kg(-1), respectively, while the recoveries were in the range of 89.3 - 107.0%. These novel magnetic MIP composites may become a powerful tool for the extraction of template from complex samples with good efficiency. PMID:27169650

  9. Formation of giant molecular clouds and helical magnetic fields by the Parker instability

    NASA Astrophysics Data System (ADS)

    Shibata, Kazunari; Matsumoto, Ryoji

    1991-10-01

    It is suggested that the Orion molecular cloud complex formed through the Parker instability (the buoyancy of a magnetic field entrained in matter) and that the helical filament found by Uchida et al. (1991) in the L1641 in the Orion cloud complex is the result of spinning gas falling along the magnetic field and twisting it. The twisted magnetic field, unlike a purely planar field, suppresses the Parker instability on small scales, allowing the generation of finite clouds rather than general turbulence.

  10. Synthesis and characterization of montmorillonite clay intercalated with molecular magnetic compounds

    SciTech Connect

    Martins, Marcel G.; Martins, Daniel O.T.A.; Carvalho, Beatriz L.C. de; Mercante, Luiza A.; Soriano, Stéphane; Andruh, Marius; Vieira, Méri D.; Vaz, Maria G.F.

    2015-08-15

    In this work montmorillonite (MMT) clay, whose matrix was modified with an ammonium salt (hexadecyltrimethylammonium bromide – CTAB), was employed as an inorganic host for the intercalation of three different molecular magnetic compounds through ion exchange: a nitronyl nitroxide derivative 2-[4-(N-ethyl)-pyridinium]-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (p-EtRad{sup +}) and two binuclear coordination compounds, [Ni(valpn)Ln]{sup 3+}, where H{sub 2}valpn stands for 1,3-propanediyl-bis(2-iminomethylene-6-methoxy-phenol), and Ln=Gd{sup III}; Dy{sup III}. The pristine MMT and the intercalated materials were characterized by X-ray powder diffraction (XRD), infrared spectroscopy (IR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and magnetic measurements. The X-ray diffraction data analysis showed an increase of the interlamellar space of the intercalated MMT, indicating the intercalation of the magnetic compounds. Furthermore, the magnetic properties of the hybrid compounds were investigated, showing similar behavior as the pure magnetic guest species. - Graphical abstract: Montmorillonite clay was employed as inorganic host for the intercalation of three different molecular magnetic compounds through ion exchange - Highlights: • Montmorillonite was employed as a host material. • Three molecular magnetic compounds were intercalated through ion exchange. • The compounds were successful intercalated maintaining the layered structure. • The hybrid materials exhibited similar magnetic behavior as the pure magnetic guest.

  11. How Composers Compose: In Search of the Questions

    ERIC Educational Resources Information Center

    Andrews, Bernard W.

    2004-01-01

    The Genesis Project is a multi-phase research project designed for the purpose of developing an in-depth understanding of the nature of musical creativity by investigating how composers compose. In this first phase of the project, an understanding of the four dimensions of musical creativity: (1) the "person", (2) the compositional "process", (3)…

  12. Dragging human mesenchymal stem cells with the aid of supramolecular assemblies of single-walled carbon nanotubes, molecular magnets, and peptides in a magnetic field.

    PubMed

    de Paula, Ana Cláudia C; Sáfar, Gustavo A M; Góes, Alfredo M; Bemquerer, Marcelo P; Ribeiro, Marcos A; Stumpf, Humberto O

    2015-01-01

    Human adipose-derived stem cells (hASCs) are an attractive cell source for therapeutic applicability in diverse fields for the repair and regeneration of damaged or malfunctioning tissues and organs. There is a growing number of cell therapies using stem cells due to their characteristics of modulation of immune system and reduction of acute rejection. So a challenge in stem cells therapy is the delivery of cells to the organ of interest, a specific site. The aim of this paper was to investigate the effects of a supramolecular assembly composed of single-walled carbon nanotubes (SWCNT), molecular magnets (lawsone-Co-phenanthroline), and a synthetic peptide (FWYANHYWFHNAFWYANHYWFHNA) in the hASCs cultures. The hASCs were isolated, characterized, expanded, and cultured with the SWCNT supramolecular assembly (SWCNT-MA). The assembly developed did not impair the cell characteristics, viability, or proliferation. During growth, the cells were strongly attached to the assembly and they could be dragged by an applied magnetic field of less than 0.3 T. These assemblies were narrower than their related allotropic forms, that is, multiwalled carbon nanotubes, and they could therefore be used to guide cells through thin blood capillaries within the human body. This strategy seems to be useful as noninvasive and nontoxic stem cells delivery/guidance and tracking during cell therapy. PMID:25688350

  13. Dragging Human Mesenchymal Stem Cells with the Aid of Supramolecular Assemblies of Single-Walled Carbon Nanotubes, Molecular Magnets, and Peptides in a Magnetic Field

    PubMed Central

    de Paula, Ana Cláudia C.; Sáfar, Gustavo A. M.; Góes, Alfredo M.; Bemquerer, Marcelo P.; Ribeiro, Marcos A.; Stumpf, Humberto O.

    2015-01-01

    Human adipose-derived stem cells (hASCs) are an attractive cell source for therapeutic applicability in diverse fields for the repair and regeneration of damaged or malfunctioning tissues and organs. There is a growing number of cell therapies using stem cells due to their characteristics of modulation of immune system and reduction of acute rejection. So a challenge in stem cells therapy is the delivery of cells to the organ of interest, a specific site. The aim of this paper was to investigate the effects of a supramolecular assembly composed of single-walled carbon nanotubes (SWCNT), molecular magnets (lawsone-Co-phenanthroline), and a synthetic peptide (FWYANHYWFHNAFWYANHYWFHNA) in the hASCs cultures. The hASCs were isolated, characterized, expanded, and cultured with the SWCNT supramolecular assembly (SWCNT-MA). The assembly developed did not impair the cell characteristics, viability, or proliferation. During growth, the cells were strongly attached to the assembly and they could be dragged by an applied magnetic field of less than 0.3 T. These assemblies were narrower than their related allotropic forms, that is, multiwalled carbon nanotubes, and they could therefore be used to guide cells through thin blood capillaries within the human body. This strategy seems to be useful as noninvasive and nontoxic stem cells delivery/guidance and tracking during cell therapy. PMID:25688350

  14. Rhenium-phthalocyanine molecular nanojunction with high magnetic anisotropy and high spin filtering efficiency

    SciTech Connect

    Li, J.; Hu, J.; Wang, H.; Wu, R. Q.

    2015-07-20

    Using the density functional and non-equilibrium Green's function approaches, we studied the magnetic anisotropy and spin-filtering properties of various transition metal-Phthalocyanine molecular junctions across two Au electrodes. Our important finding is that the Au-RePc-Au junction has both large spin filtering efficiency (>80%) and large magnetic anisotropy energy, which makes it suitable for device applications. To provide insights for the further experimental work, we discussed the correlation between the transport property, magnetic anisotropy, and wave function features of the RePc molecule, and we also illustrated the possibility of controlling its magnetic state.

  15. Quantum engineering of spin and anisotropy in magnetic molecular junctions

    PubMed Central

    Jacobson, Peter; Herden, Tobias; Muenks, Matthias; Laskin, Gennadii; Brovko, Oleg; Stepanyuk, Valeri; Ternes, Markus; Kern, Klaus

    2015-01-01

    Single molecule magnets and single spin centres can be individually addressed when coupled to contacts forming an electrical junction. To control and engineer the magnetism of quantum devices, it is necessary to quantify how the structural and chemical environment of the junction affects the spin centre. Metrics such as coordination number or symmetry provide a simple method to quantify the local environment, but neglect the many-body interactions of an impurity spin coupled to contacts. Here, we utilize a highly corrugated hexagonal boron nitride monolayer to mediate the coupling between a cobalt spin in CoHx (x=1,2) complexes and the metal contact. While hydrogen controls the total effective spin, the corrugation smoothly tunes the Kondo exchange interaction between the spin and the underlying metal. Using scanning tunnelling microscopy and spectroscopy together with numerical simulations, we quantitatively demonstrate how the Kondo exchange interaction mimics chemical tailoring and changes the magnetic anisotropy. PMID:26456084

  16. Quantum engineering of spin and anisotropy in magnetic molecular junctions.

    PubMed

    Jacobson, Peter; Herden, Tobias; Muenks, Matthias; Laskin, Gennadii; Brovko, Oleg; Stepanyuk, Valeri; Ternes, Markus; Kern, Klaus

    2015-01-01

    Single molecule magnets and single spin centres can be individually addressed when coupled to contacts forming an electrical junction. To control and engineer the magnetism of quantum devices, it is necessary to quantify how the structural and chemical environment of the junction affects the spin centre. Metrics such as coordination number or symmetry provide a simple method to quantify the local environment, but neglect the many-body interactions of an impurity spin coupled to contacts. Here, we utilize a highly corrugated hexagonal boron nitride monolayer to mediate the coupling between a cobalt spin in CoHx (x=1,2) complexes and the metal contact. While hydrogen controls the total effective spin, the corrugation smoothly tunes the Kondo exchange interaction between the spin and the underlying metal. Using scanning tunnelling microscopy and spectroscopy together with numerical simulations, we quantitatively demonstrate how the Kondo exchange interaction mimics chemical tailoring and changes the magnetic anisotropy. PMID:26456084

  17. Quantum engineering of spin and anisotropy in magnetic molecular junctions

    NASA Astrophysics Data System (ADS)

    Jacobson, Peter; Herden, Tobias; Muenks, Matthias; Laskin, Gennadii; Brovko, Oleg; Stepanyuk, Valeri; Ternes, Markus; Kern, Klaus

    2015-10-01

    Single molecule magnets and single spin centres can be individually addressed when coupled to contacts forming an electrical junction. To control and engineer the magnetism of quantum devices, it is necessary to quantify how the structural and chemical environment of the junction affects the spin centre. Metrics such as coordination number or symmetry provide a simple method to quantify the local environment, but neglect the many-body interactions of an impurity spin coupled to contacts. Here, we utilize a highly corrugated hexagonal boron nitride monolayer to mediate the coupling between a cobalt spin in CoHx (x=1,2) complexes and the metal contact. While hydrogen controls the total effective spin, the corrugation smoothly tunes the Kondo exchange interaction between the spin and the underlying metal. Using scanning tunnelling microscopy and spectroscopy together with numerical simulations, we quantitatively demonstrate how the Kondo exchange interaction mimics chemical tailoring and changes the magnetic anisotropy.

  18. Electronic and magnetic properties of silicon supported organometallic molecular wires: a density functional theory (DFT) study

    NASA Astrophysics Data System (ADS)

    Liu, Xia; Tan, Yingzi; Li, Xiuling; Wu, Xiaojun; Pei, Yong

    2015-08-01

    The electronic and magnetic properties of transition metal (TM = Sc, Ti, V, Cr and Mn) atom incorporated single and double one-dimensional (1D) styrene molecular wires confined on the hydrogen-terminated Si(100) surface are explored for the first time by means of spin-polarized density functional theory, denoted as Si-[TM(styrene)]. It is unveiled that TM atoms bind asymmetrically to the adjacent phenyl rings, which leads to novel electronic and magnetic properties in stark contrast to the well-studied gas phase TM-benzene molecular wires. Si-[Mn(styrene)]∞ and Si-[Cr(styrene)]∞ single molecular wires (SMWs) are a ferromagnetic semiconductor and half metal, respectively. Creation of H-atom defects on the silicon surface can introduce an impurity metallic band, which leads to novel half-metallic magnetism of a Si-[Mn(styrene)]∞ system. Moreover, double molecular wires (DMWs) containing two identical or hetero SMWs are theoretically designed. The [Mn(styrene)]∞-[Cr(styrene)]∞ DMW exhibits half-metallic magnetism where the spin-up and spin-down channels are contributed by two single molecular wires. Finally, we demonstrate that introducing a TM-defect may significantly affect the electronic structure and magnetic properties of molecular wires. These studies provide new insights into the structure and properties of surface supported 1-D sandwiched molecular wires and may inspire the future experimental synthesis of substrate confined organometallic sandwiched molecular wires.The electronic and magnetic properties of transition metal (TM = Sc, Ti, V, Cr and Mn) atom incorporated single and double one-dimensional (1D) styrene molecular wires confined on the hydrogen-terminated Si(100) surface are explored for the first time by means of spin-polarized density functional theory, denoted as Si-[TM(styrene)]. It is unveiled that TM atoms bind asymmetrically to the adjacent phenyl rings, which leads to novel electronic and magnetic properties in stark contrast to

  19. Iron Oxide Nanoparticle-Micelles (ION-Micelles) for Sensitive (Molecular) Magnetic Particle Imaging and Magnetic Resonance Imaging

    PubMed Central

    Starmans, Lucas W. E.; Burdinski, Dirk; Haex, Nicole P. M.; Moonen, Rik P. M.; Strijkers, Gustav J.; Nicolay, Klaas; Grüll, Holger

    2013-01-01

    Background Iron oxide nanoparticles (IONs) are a promising nanoplatform for contrast-enhanced MRI. Recently, magnetic particle imaging (MPI) was introduced as a new imaging modality, which is able to directly visualize magnetic particles and could serve as a more sensitive and quantitative alternative to MRI. However, MPI requires magnetic particles with specific magnetic properties for optimal use. Current commercially available iron oxide formulations perform suboptimal in MPI, which is triggering research into optimized synthesis strategies. Most synthesis procedures aim at size control of iron oxide nanoparticles rather than control over the magnetic properties. In this study, we report on the synthesis, characterization and application of a novel ION platform for sensitive MPI and MRI. Methods and Results IONs were synthesized using a thermal-decomposition method and subsequently phase-transferred by encapsulation into lipidic micelles (ION-Micelles). Next, the material and magnetic properties of the ION-Micelles were analyzed. Most notably, vibrating sample magnetometry measurements showed that the effective magnetic core size of the IONs is 16 nm. In addition, magnetic particle spectrometry (MPS) measurements were performed. MPS is essentially zero-dimensional MPI and therefore allows to probe the potential of iron oxide formulations for MPI. ION-Micelles induced up to 200 times higher signal in MPS measurements than commercially available iron oxide formulations (Endorem, Resovist and Sinerem) and thus likely allow for significantly more sensitive MPI. In addition, the potential of the ION-Micelle platform for molecular MPI and MRI was showcased by MPS and MRI measurements of fibrin-binding peptide functionalized ION-Micelles (FibPep-ION-Micelles) bound to blood clots. Conclusions The presented data underlines the potential of the ION-Micelle nanoplatform for sensitive (molecular) MPI and warrants further investigation of the FibPep-ION-Micelle platform for

  20. Stochastic jumps of magnetization in [Mn{(R/S)-pn}]2[Mn{(R/S)-pn}2(H2O)][Cr(CN)6]2 molecular magnet

    NASA Astrophysics Data System (ADS)

    Kirman, M. V.; Talantsev, A. D.; Koplak, O. V.; Morgunov, R. B.

    2015-03-01

    Series of stochastic jumps of the magnetic moment (up to five individual jumps) have been observed at the demagnetization of single crystals of [Mn{(R/S)-pn}]2[Mn{(R/S)-pn}2(H2O)][Cr(CN)6]2 molecular magnet in a narrow range of magnetic fields near the coercive force ( H c = 7.5 Oe). The magnetic field at which jumps of the magnetization arise decreases with an increase in the temperature.

  1. A molecular chemical approach to the magnetic multilayers

    NASA Astrophysics Data System (ADS)

    Coronado, E.; Galán-Mascarós, J. R.; Gómez-García, C. J.; Burriel, R.

    1999-05-01

    Using the bi-dimensional bimetallic networks based upon oxalate complexes, it is possible to prepare new multilayered materials by insertion of 'electroactive' molecules in between these layers. According to this approach a new family of compounds presenting alternating ferromagnetic—paramagnetic layers have been successfully prepared. Here we present the magnetic and specific heat characterization.

  2. Tropes of the Composing Process.

    ERIC Educational Resources Information Center

    Arrington, Phillip K.

    1986-01-01

    Offers a montage of the most important revisions of the four master tropes--metaphor, metonymy, synecdoche, and irony--for the composing process itself. Discusses the capacity of tropes to prefigure ideological stances toward language and writing. (EL)

  3. Temperature-controlled molecular depolarization gates in nuclear magnetic resonance

    SciTech Connect

    Schroder, Leif; Schroder, Leif; Chavez, Lana; Meldrum, Tyler; Smith, Monica; Lowery, Thomas J.; E. Wemmer, David; Pines, Alexander

    2008-02-27

    Down the drain: Cryptophane cages in combination with selective radiofrequency spin labeling can be used as molecular 'transpletor' units for transferring depletion of spin polarization from a hyperpolarized 'source' spin ensemble to a 'drain' ensemble. The flow of nuclei through the gate is adjustable by the ambient temperature, thereby enabling controlled consumption of hyperpolarization.

  4. [Molecular/polymeric magnetism]. Progress report, [March 15--December 31, 1993

    SciTech Connect

    Not Available

    1993-12-31

    Accomplishments during this past grant period span three areas of research. (1) Following models the authors and others have proposed, they have synthesized numerous new materials to test the generality of magnetism in molecular/polymeric systems. This activity is capped by their disclosure of the first room temperature molecular based magnet V(TCNE){sub x} y(solvent). (2) They have extensively studied the magnetic transitions and related phenomena in decamethylferrocenium tetracyanoethanide, [FeCp{sup *}{sub 2}][TCNE]. V(TCNE){sub x}{center_dot}y(solvent), and related materials, and developed an initial understanding of the key roles played by disorder, anisotropy, dimensionality, and spin magnitude. (3) They have tested theirs and others` models for the origin of magnetic exchange between local sites, and models for control of {Tc}, determining successes and shortcomings. They briefly summarize here the major breakthroughs, accomplishments, and discoveries that have occurred during this period.

  5. Magnetic micro-barcodes for molecular tagging applications

    NASA Astrophysics Data System (ADS)

    Hayward, T. J.; Hong, B.; Vyas, K. N.; Palfreyman, J. J.; Cooper, J. F. K.; Jiang, Z.; Jeong, J. R.; Llandro, J.; Mitrelias, T.; Bland, J. A. C.; Barnes, C. H. W.

    2010-05-01

    We present proof-of-principle experiments and simulations that demonstrate a new biological assay technology in which microscopic tags carrying multi-bit magnetic codes are used to label probe biomolecules. It is demonstrated that these 'micro-barcode tags' can be encoded, transported using micro-fluidics and are compatible with surface chemistry. We also present simulations and experimental results which suggest the feasibility of decoding the micro-barcode tags using magnetoresistive sensors. Together, these results demonstrate substantial progress towards meeting the critical requirements of a magnetically encoded, high-throughput and portable biological assay platform. We also show that an extension of our technology could potentially be used to label libraries consisting of ~104 distinct probe molecules, and could therefore have a strong impact on mainstream medical diagnostics.

  6. Conduction mechanism of nitronyl-nitroxide molecular magnetic compounds

    NASA Astrophysics Data System (ADS)

    Dotti, N.; Heintze, E.; Slota, M.; Hübner, R.; Wang, F.; Nuss, J.; Dressel, M.; Bogani, L.

    2016-04-01

    We investigate the conduction mechanisms of nitronyl-nitroxide (NIT) molecular radicals, as useful for the creation of nanoscopic molecular spintronic devices, finding that it does not correspond to standard Mott behavior, as previously postulated. We provide a complete investigation using transport measurements, low-energy, sub-THz spectroscopy and introducing differently substituted phenyl appendages. We show that a nontrivial surface-charge-limited regime is present in addition to the standard low-voltage Ohmic conductance. Scaling analysis allows one to determine all the main transport parameters for the compounds and highlights the presence of charge-trapping effects. Comparison among the different compounds shows the relevance of intermolecular stacking between the aromatic ring of the phenyl appendix and the NIT motif in the creation of useful electron transport channels. The importance of intermolecular pathways is further highlighted by electronic structure calculations, which clarify the nature of the electronic channels and their effect on the Mott character of the compounds.

  7. Toward Molecular 4f Single-Ion Magnet Qubits.

    PubMed

    Pedersen, Kasper S; Ariciu, Ana-Maria; McAdams, Simon; Weihe, Høgni; Bendix, Jesper; Tuna, Floriana; Piligkos, Stergios

    2016-05-11

    Quantum coherence is detected in the 4f single-ion magnet (SIM) Yb(trensal), by isotope selective pulsed EPR spectroscopy on an oriented single crystal. At X-band, the spin-lattice relaxation (T1) and phase memory (Tm) times are found to be independent of the nuclei bearing, or not, a nuclear spin. The observation of Rabi oscillations of the spin echo demonstrates the possibility to coherently manipulate the system for more than 70 rotations. This renders Yb(trensal), a sublimable and chemically modifiable SIM, an excellent candidate for quantum information processing. PMID:27105449

  8. Structural, magnetic and optical properties of two concomitant molecular crystals

    NASA Astrophysics Data System (ADS)

    Silva, Manuela Ramos; Milne, Bruce; Coutinho, Joana T.; Pereira, Laura C. J.; Martín-Ramos, Pablo; Pereira da Silva, Pedro S.; Martín-Gil, Jesús

    2016-03-01

    A new 1D complex has been prepared and characterized. X-ray single crystal structure confirms that the Cu(II) ions assemble in alternating chains with Cu … Cu distances of 2.5685(4) and 3.1760(4) Å. The temperature dependence of the magnetic susceptibility reveals an antiferromagnetic interaction between the paddle-wheel copper centers with an exchange of -300 cm-1. The exchange integral was also determined by quantum chemical ab-initio calculations, using polarised and unpolarised basis sets reproducing well the experimental value. The second harmonic generation efficiency of a concomitantly crystallized material was evaluated and was found to be comparable to urea.

  9. Nuclear magnetic resonance studies on the rotational and translational motions of ionic liquids composed of 1-ethyl-3-methylimidazolium cation and bis(trifluoromethanesulfonyl)amide and bis(fluorosulfonyl)amide anions and their binary systems including lithium salts

    NASA Astrophysics Data System (ADS)

    Hayamizu, Kikuko; Tsuzuki, Seiji; Seki, Shiro; Umebayashi, Yasuhiro

    2011-08-01

    Room temperature ionic liquids (ILs) are stable liquids composed of anions and cations. 1-ethyl-3-methyl-imidazolium (EMIm, EMI) is a popular and important cation that produces thermally stable ILs with various anions. In this study two amide-type anions, bis(trifluoro-methanesulfonyl)amide [N(SO2CF3)2, TFSA, TFSI, NTf2, or Tf2N] and bis(fluorosulfonyl)amide [(N(SO2F)2, FSA, or FSI] were investigated by multinuclear NMR spectroscopy. In addition to EMIm-TFSA and EMIm-FSA, lithium-salt-doped binary systems were prepared (EMIm-TFSA-Li and EMIm-FSA-Li). The spin-lattice relaxation times (T1) were measured by 1H, 19F, and 7Li NMR spectroscopy and the correlation times of 1H NMR, τc(EMIm) (8 × 10-10 to 3 × 10-11 s) for the librational molecular motion of EMIm and those of 7Li NMR, τc(Li) (5 × 10-9 to 2 × 10-10 s) for a lithium jump were evaluated in the temperature range between 253 and 353 K. We found that the bulk viscosity (η) versus τc(EMIm) and cation diffusion coefficient DEMIm versus the rate 1/τc(EMIm) have good relationships. Similarly, linear relations were obtained for the η versus τc(Li) and the lithium diffusion coefficient DLi versus the rate 1/τc(Li). The mean one-jump distances of Li were calculated from τc(Li) and DLi. The experimental values for the diffusion coefficients, ionic conductivity, viscosity, and density in our previous paper were analyzed by the Stokes-Einstein, Nernst-Einstein, and Stokes-Einstein-Debye equations for the neat and binary ILs to clarify the physicochemical properties and mobility of individual ions. The deviations from the classical equations are discussed.

  10. Magnetocaloric effect and critical behavior in Mn2-imidazole-[Nb(CN)8] molecular magnetic sponge

    NASA Astrophysics Data System (ADS)

    Fitta, Magdalena; Pełka, Robert; Gajewski, Marcin; Mihalik, Marian; Zentkova, Maria; Pinkowicz, Dawid; Sieklucka, Barbara; Bałanda, Maria

    2015-12-01

    A comprehensive study of magnetocaloric effect (MCE) and critical behavior in the {Mn2(imH)2(H2O)4[Nb(CN)8]·4H2O}n molecular magnet is reported. The compound is an example of a magnetic sponge, where structural changes provoked by dehydration process lead to the increase of Tc critical temperature from 25 K for the as-synthesized sample (1) up to 60 K for the anhydrous one (2). MCE and critical behavior were investigated by magnetization measurements. The maximum value of magnetic entropy change ΔS, determined by the magnetization measurements for 1 is 6.70 J mol-1 K-1 (8.95 J kg-1 K-1) at μ0ΔH=5 T, while for 2 it is equal to 4.02 J mol-1 K-1 (7.73 J kg-1 K-1) at the same magnetic field change. The field dependence of MCE at Tc for 1 and 2 was consistent with critical exponents, which allowed to classify both phases to 3D Heisenberg universality class. The Tc-2/3 dependence of the maximum entropy change has been tested using data of 1 and 2 together with MCE data previously reported for other members of the ferrimagnetic Mn2-L-[Nb(CN)8] (L=imidazole, pyridazine and pyrazole) series. Experimental MCE results have been compared with the spin contribution to the magnetic entropy change estimated using a molecular field approximation.

  11. Ultrafast quantum spin-state switching in the Co-octaethylporphyrin molecular magnet with a terahertz pulsed magnetic field

    NASA Astrophysics Data System (ADS)

    Farberovich, Oleg V.; Mazalova, Victoria L.

    2016-05-01

    Molecular spin crossover switches are the objects of intense theoretical and experimental studies in recent years. This interest is due to the fact that these systems allow one to control their spin state by applying an external photo-, thermo-, piezo-, or magnetic stimuli. The greatest amount of research is currently devoted to the study of the effect of the photoexcitation on the bi-stable states of spin crossover single molecular magnets (SMMs). The main limitation of photo-induced bi-stable states is their short lifetime. In this paper we present the results of a study of the spin dynamics of the Co-octaethylporphyrin (CoOEP) molecule in the Low Spin (LS) state and the High Spin (HS) state induced by applying the magnetic pulse of 36.8 T. We show that the spin switching in case of the HS state of the CoOEP molecule is characterized by a long lifetime and is dependent on the magnitude and duration of the applied field. Thus, after applying an external stimuli the system in the LS state after the spin switching reverts to its ground state, whereas the system in the HS state remains in the excited state for a long time. We found that the temperature dependency of magnetic susceptibility shows an abrupt thermal spin transition between two spin states at 40 K. Here the proposed theoretical approach opens the way to create modern devices for spintronics with the controllable spin switching process.

  12. Protective Effect of Ascorbic Acid on Molecular Behavior Changes of Hemoglobin Induced by Magnetic Field

    NASA Astrophysics Data System (ADS)

    Hassan, Nahed S.; Abou Aiad, T. H. M.

    With the use of electricity and industrialization of societies, humans are commonly exposed to static magnetic field induced by electric currents. The putative mechanisms by which Static Magnetic Field (SMF) may affect biological systems is that of increasing free radical life span in organisms. To test this hypothesis, we investigate the effect of ascorbic acid (Vitamin C) treatment on the changes in the molecular behavior of hemoglobin as a result of exposure of the animals to magnetic field in the occupation levels. By measuring the relative permittivity, dielectric loss, relaxation time, conductivity, radius and diffusion coefficient of aqueous solutions of hemoglobin. These measurements were calculated in the frequency range of (100 Hz-100 kHz) to give more information about molecular behavior. Twenty four male albino rats were equally divided into four groups 1, 2, 3 and 4. Animals of group 1, were used as control, animals of group 2, were exposed to (0.2T) magnetic field and that of group 3, 4, were treated with Ascorbic Acid by two doses group 3 (20 mg kg-1 body weight), group 4 (50 mg kg-1 body weight) orally half hour before exposure to magnetic field. The sub chronic exposure expanded (1 h day-1) for 30 consecutive days. The results indicated that exposure of animals to magnetic field resulted in changes in the molecular behavior of hemoglobin molecule while treatment with ascorbic acid afforded comparatively more significant amelioration in these molecular changes, via decreasing the radical pair interaction of magnetic field with biological molecules.

  13. Quantum tunneling of two coupled single-molecular magnets

    NASA Astrophysics Data System (ADS)

    Hu, Jianming; Chen, Zhide; Shen, Shunqing

    2003-03-01

    Jian-Ming Hu, Zhi-De Chen and Shun-Qing Shen Department of Physics, The University of Hong Kong Pokfulam Road, Hong Kong December 02, 2002 Very recently a supramolecular dimer of two single-molecule magnets (SMM) was reported to be synthesized successfully. Two single-molecule magnets are coupled antiferromagnetically to form a supramolecule dimer. We study the coupling effect and tunneling process by the numerical exact diagonalization method. The sweeping rate effect in the derivatives of hysteresis loops has been quantitatively investigated using the modified Landau-Zener model. In addiction we find that exchange coupling between the two SMMs provides a biased field to expel the tunneling between SMMs to two new resonant points via an intermediate state, and direct tunneling is prohibited. The model parameters are calculated for the dimer based on the tunneling process. The outcome indicates that the coupling effect will not change the parameters of each SMM too much at all. This work is supported by a CRCG grant of The University of Hong Kong.

  14. Molecular magnets based on homometallic hexanuclear lanthanide(III) complexes.

    PubMed

    Das, Sourav; Hossain, Sakiat; Dey, Atanu; Biswas, Sourav; Sutter, Jean-Pascal; Chandrasekhar, Vadapalli

    2014-05-19

    The reaction of lanthanide(III) chloride salts (Gd(III), Dy(III), Tb(III), and Ho(III)) with the hetero donor chelating ligand N'-(2-hydroxy-3-methoxybenzylidene)-6-(hydroxymethyl)picolinohydrazide (LH3) in the presence of triethylamine afforded the hexanuclear Ln(III) complexes [{Ln6(L)2(LH)2}(μ3-OH)4][MeOH]p[H2O]q[Cl]4·xH2O·yCH3OH (1, Ln = Gd(III), p = 4, q = 4, x = 8, y = 2; 2, Ln = Dy(III), p = 2, q = 6, x = 8, y = 4; 3, Ln = Tb(III), p = 2, q = 6, x = 10, y = 4; 4, Ln = Ho(III), p = 2, q = 6, x = 10, y = 2). X-ray diffraction studies revealed that these compounds possess a hexanuclear [Ln6(OH)4](14+) core consisting of four fused [Ln3(OH)](8+) subunits. Both static (dc) and dynamic (ac) magnetic properties of 1-4 have been studied. Single-molecule magnetic behavior has been observed in compound 2 with an effective energy barrier and relaxation time pre-exponential parameters of Δ/kB = 46.2 K and τ0 = 2.85 × 10(-7) s, respectively. PMID:24766539

  15. Recent Advances in Molecular Magnetic Resonance Imaging of Liver Fibrosis

    PubMed Central

    Li, Zhiming; Sun, Jihong; Yang, Xiaoming

    2015-01-01

    Liver fibrosis is a life-threatening disease with high morbidity and mortality owing to its diverse causes. Liver biopsy, as the current gold standard for diagnosing and staging liver fibrosis, has a number of limitations, including sample variability, relatively high cost, an invasive nature, and the potential of complications. Most importantly, in clinical practice, patients often reject additional liver biopsies after initiating treatment despite their being necessary for long-term follow-up. To resolve these problems, a number of different noninvasive imaging-based methods have been developed for accurate diagnosis of liver fibrosis. However, these techniques only reflect morphological or perfusion-related alterations in the liver, and thus they are generally only useful for the diagnosis of late-stage liver fibrosis (liver cirrhosis), which is already characterized by “irreversible” anatomic and hemodynamic changes. Thus, it is essential that new approaches are developed for accurately diagnosing early-stage liver fibrosis as at this stage the disease may be “reversed” by active treatment. The development of molecular MR imaging technology has potential in this regard, as it facilitates noninvasive, target-specific imaging of liver fibrosis. We provide an overview of recent advances in molecular MR imaging for the diagnosis and staging of liver fibrosis and we compare novel technologies with conventional MR imaging techniques. PMID:25874221

  16. Magnetic susceptibility anisotropy of human brain in vivo and its molecular underpinnings.

    PubMed

    Li, Wei; Wu, Bing; Avram, Alexandru V; Liu, Chunlei

    2012-02-01

    Frequency shift of gradient-echo MRI provides valuable information for assessing brain tissues. Recent studies suggest that the frequency and susceptibility contrast depend on white matter fiber orientation. However, the molecular underpinning of the orientation dependence is unclear. In this study, we investigated the orientation dependence of susceptibility of human brain in vivo and mouse brains ex vivo. The source of susceptibility anisotropy in white matter is likely to be myelin as evidenced by the loss of anisotropy in the dysmyelinating shiverer mouse brain. A biophysical model is developed to investigate the effect of the molecular susceptibility anisotropy of myelin components, especially myelin lipids, on the bulk anisotropy observed by MRI. This model provides a consistent interpretation of the orientation dependence of macroscopic magnetic susceptibility in normal mouse brain ex vivo and human brain in vivo and the microscopic origin of anisotropic susceptibility. It is predicted by the theoretical model and illustrated by the experimental data that the magnetic susceptibility of the white matter is least diamagnetic along the fiber direction. This relationship allows an efficient extraction of fiber orientation using susceptibility tensor imaging. These results suggest that anisotropy on the molecular level can be observed on the macroscopic level when the molecules are aligned in a highly ordered manner. Similar to the utilization of magnetic susceptibility anisotropy in elucidating molecular structures, imaging magnetic susceptibility anisotropy may also provide a useful tool for elucidating the microstructure of ordered biological tissues. PMID:22036681

  17. Rotational energy of the hydrogen molecular ion in a magnetic field

    SciTech Connect

    Maluendes, S.A.; Fernandez, F.M.; Castro, E.A.

    1983-10-01

    A general method which combines hypervirial relations with the Hellmann-Feynman theorem and perturbation theory is applied in order to calculate the rotational eigenvalues of the hydrogen molecular ion in a magnetic field. Analytical expressions as well as numerical results are presented for both low and high field strengths.

  18. Nuclear magnetic resonance spectral analysis and molecular properties of berberine

    NASA Astrophysics Data System (ADS)

    Huang, Ming-Ju; Lee, Ken S.; Hurley, Sharon J.

    An extensive theoretical study of berberine has been performed at the ab initio HF/6-31G**, HF/6-311G**, and B3LYP/6-311G** levels with and without solvent effects. The optimized structures are compared with X-ray data. We found that the optimized structures with solvent effects are in slightly better agreement with X-ray data than those without solvent effects. The 1H and 13C nuclear magnetic resonance (NMR) chemical shifts of berberine were calculated by using the gauge-independent atomic orbital (GIAO) (with and without solvent effects), CSGT, and IGAIM methods. The calculated chemical shifts were compared with the two-dimensional NMR experimental data. Overall, the calculated chemical shifts show very good agreement with the experimental results. The harmonic vibrational frequencies for berberine were calculated at the B3LYP/6-311G** level.

  19. Magnetic interaction between a radical spin and a single-molecule magnet in a molecular spin-valve.

    PubMed

    Urdampilleta, Matias; Klayatskaya, Svetlana; Ruben, Mario; Wernsdorfer, Wolfgang

    2015-04-28

    Molecular spintronics using single molecule magnets (SMMs) is a fast growing field of nanoscience that proposes to manipulate the magnetic and quantum information stored in these molecules. Herein we report evidence of a strong magnetic coupling between a metallic ion and a radical spin in one of the most extensively studied SMMs: the bis(phtalocyaninato)terbium(III) complex (TbPc2). For that we use an original multiterminal device comprising a carbon nanotube laterally coupled to the SMMs. The current through the device, sensitive to magnetic interactions, is used to probe the magnetization of a single Tb ion. Combining this electronic read-out with the transverse field technique has allowed us to measure the interaction between the terbium ion, its nuclear spin, and a single electron located on the phtalocyanine ligands. We show that the coupling between the Tb and this radical is strong enough to give extra resonances in the hysteresis loop that are not observed in the anionic form of the complex. The experimental results are then modeled by diagonalization of a three-spins Hamiltonian. This strong coupling offers perspectives for implementing nuclear and electron spin resonance techniques to perform basic quantum operations in TbPc2. PMID:25858088

  20. Suppression of quantum phase interference in the molecular magnet Fe8 with dipolar-dipolar interaction

    NASA Astrophysics Data System (ADS)

    Chen, Zhi-De; Liang, J.-Q.; Shen, Shun-Qing

    2002-09-01

    Renormalized tunnel splitting with a finite distribution in the biaxial spin model for molecular magnets is obtained by taking into account the dipolar interaction of enviromental spins. Oscillation of the resonant tunnel splitting with a transverse magnetic field along the hard axis is smeared by the finite distribution, which subsequently affects the quantum steps of the hysteresis curve evaluated in terms of the modified Landau-Zener model of spin flipping induced by the sweeping field. We conclude that the dipolar-dipolar interaction drives decoherence of quantum tunneling in the molecular magnet Fe8, which explains why the quenching points of tunnel splitting between odd and even resonant tunneling predicted theoretically were not observed experimentally.

  1. Classical Magnetic Dipole Moments for the Simulation of Vibrational Circular Dichroism by ab Initio Molecular Dynamics.

    PubMed

    Thomas, Martin; Kirchner, Barbara

    2016-02-01

    We present a new approach for calculating vibrational circular dichroism spectra by ab initio molecular dynamics. In the context of molecular dynamics, these spectra are given by the Fourier transform of the cross-correlation function of magnetic dipole moment and electric dipole moment. We obtain the magnetic dipole moment from the electric current density according to the classical definition. The electric current density is computed by solving a partial differential equation derived from the continuity equation and the condition that eddy currents should be absent. In combination with a radical Voronoi tessellation, this yields an individual magnetic dipole moment for each molecule in a bulk phase simulation. Using the chiral alcohol 2-butanol as an example, we show that experimental spectra are reproduced very well. Our approach requires knowing only the electron density in each simulation step, and it is not restricted to any particular electronic structure method. PMID:26771403

  2. The quest for rationalizing the magnetism in purely organic semiquinone-bridged bisdithiazolyl molecular magnets.

    PubMed

    Fumanal, Maria; Deumal, Mercè

    2016-07-27

    Semiquinone-bridged bisdithiazolyl-based radicals (XBBO) are appealing purely organic magnetic building blocks for the synthesis of new functional materials. Remarkably, for the phenyl-derivative PhBBO, the rationalization of its magnetism becomes a proof of concept that DFT can dramatically fail to evaluate JAB magnetic interactions between purely organic radical pairs. Instead, wavefunction-based methods are required. Once JAB's are fully characterized, the magnetic topology of PhBBO is disclosed to consist of ferromagnetic FM π-stacks that are very weakly coupled (by FM and AFM JAB interactions). The magnetic susceptibility χT(T) and magnetization M(H) of PhBBO are then calculated using a first-principles bottom-up approach. The study of the unit cell contraction upon cooling from room temperature to zero-Kelvin is relevant to propose a suitable model for the phase transition that occurs at 4.5 K. A simplistic picture tells us that the antiparallel-aligned 1D-FM-chains convert into domains of weakly either FM- or AFM-coupled 1D-FM-chains. Accordingly, the presence of these domains may introduce geometrical spin frustration below 4.5 K. PMID:27412491

  3. Guidelines for Coaching Student Composers.

    ERIC Educational Resources Information Center

    Wilson, Dana

    2001-01-01

    Focuses on teaching students how to compose music. Addresses issues, such as how to get the students started and types of questions to ask students about their compositions. Discusses the musical elements involved in composition, such as melody, harmony, rhythm and meter, timbre, texture, and formal design. (CMK)

  4. Transient magnetic tunneling mediated by a molecular bridge in the junction region

    NASA Astrophysics Data System (ADS)

    Kalvová, A.; Špička, V.; Velický, B.

    2014-07-01

    This paper extends our recent theoretical study of transient currents in molecular bridge junctions [1] to magnetic tunneling. Presently, we calculate the excess magnetic tunneling through the molecular bridge shunting the junction. The system is represented by two ferromagnetic electrodes bridged by a molecular size island with one electronic level and a local Hubbard type correlation. The island is linked with the electrodes by tunneling junctions whose coupling strength is assumed to undergo rapid changes affecting the connectivity of the system. We employ the non-equilibrium Green's functions. The numerical solution is obtained solving the real-time Dyson equation in the integro-differential form self-consistently. The switching events controlling the junctions give rise to transient changes of magnetisation of the island. They strongly depend on the static galvanic bias between the electrodes, mutual alignment of their magnetisation and on the time scale of the switching.

  5. Exploiting the magnetomechanical interaction for cooling magnetic molecular junctions by spin-polarized currents

    NASA Astrophysics Data System (ADS)

    Brüggemann, J.; Weiss, S.; Nalbach, P.; Thorwart, M.

    2016-02-01

    We present a scheme for cooling a vibrational mode of a magnetic molecular nanojunction by a spin-polarized charge current upon exploiting the interaction between its magnetic moment and the vibration. The spin-polarized charge current polarizes the magnetic moment of the nanoisland, thereby lowering its energy. A small but finite coupling between the vibration and the magnetic moment permits a direct exchange of energy such that vibrational energy can be transferred into the magnetic state. For positive bias voltages, this generates an effective cooling of the molecular vibrational mode. We determine parameter regimes for the cooling of the vibration to be optimal. Although the flowing charge current inevitably heats up the vibrational mode via Ohmic energy losses, we show that due to the magnetomechanical coupling, the vibrational energy (i.e, the effective phonon temperature) can be lowered below 50% of its initial value, when the two leads are polarized anti-parallel. In contrast to the cooling effect for positive bias voltages, net heating of the vibrational mode occurs for negative bias voltages. The cooling effect is enhanced for a stronger anti-parallel magnetic polarization of the leads, while the heating is stronger for a larger parallel polarization. Yet, dynamical cooling is also possible with parallel lead alignments when the two tunneling barriers are asymmetric.

  6. Molecular dynamics simulation of Lorentz force microscopy in magnetic nano-disks

    NASA Astrophysics Data System (ADS)

    Dias, R. A.; Mello, E. P.; Coura, P. Z.; Leonel, S. A.; Maciel, I. O.; Toscano, D.; Rocha, J. C. S.; Costa, B. V.

    2013-04-01

    In this paper, we present a molecular dynamics simulation to model the Lorentz force microscopy experiment. Experimentally, this technique consists in the scattering of electrons by magnetic structures in surfaces and gases. Here, we will explore the behavior of electrons colliding with nano-magnetic disks. The computational molecular dynamics experiment allows us to follow the trajectory of individual electrons all along the experiment. In order to compare our results with the experimental one reported in literature, we model the experimental electron detectors in a simplified way: a photo-sensitive screen is simulated in such way that it counts the number of electrons that collide at a certain position. The information is organized to give in grey scale the image information about the magnetic properties of the structure in the target. Computationally, the sensor is modeled as a square matrix in which we count how many electrons collide at each specific point after being scattered by the magnetic structure. We have used several configurations of the magnetic nano-disks to understand the behavior of the scattered electrons, changing the orientation direction of the magnetic moments in the nano-disk in several ways. Our results match very well with the experiments, showing that this simulation can become a powerful technique to help to interpret experimental results.

  7. High-capacity magnetic hollow porous molecularly imprinted polymers for specific extraction of protocatechuic acid.

    PubMed

    Li, Hui; Hu, Xin; Zhang, Yuping; Shi, Shuyun; Jiang, Xinyu; Chen, Xiaoqin

    2015-07-24

    Magnetic hollow porous molecularly imprinted polymers (HPMIPs) with high binding capacity, fast mass transfer, and easy magnetic separation have been fabricated for the first time. In this method, HPMIPs was firstly synthesized using protocatechuic acid (PCA) as template, 4-vinylpyridine (4-VP) as functional monomer, glycidilmethacrylate (GMA) as co-monomer, and MCM-48 as sacrificial support. After that, epoxide ring of GMA was opened for chemisorbing Fe3O4 nanoparticles to prepare magnetic HPMIPs. The results of characterization indicated that magnetic HPMIPs exhibited large surface area (548m(2)/g) with hollow porous structure and magnetic sensitivity (magnetic saturation at 2.9emu/g). The following adsorption characteristics investigation exhibited surprisingly higher adsorption capacity (37.7mg/g), and faster kinetic binding (25min) than any previously reported PCA imprinted MIPs by traditional or surface imprinting technology. The equilibrium data fitted well to Langmuir equation and the adsorption process could be described by pseudo-second order model. The selective recognition experiments also demonstrated the high selectivity of magnetic HPMIPs towards PCA over analogues. The results of the real sample analysis confirmed the superiority of the proposed magnetic HPMIPs for selective and efficient enrichment of trace PCA from complex matrices. PMID:26044378

  8. Progressive Transformation between Two Magnetic Ground States for One Crystal Structure of a Chiral Molecular Magnet.

    PubMed

    Li, Li; Nishihara, Sadafumi; Inoue, Katsuya; Kurmoo, Mohamedally

    2016-03-21

    We report the exceptional observation of two different magnetic ground states (MGS), spin glass (SG, T(B) = 7 K) and ferrimagnet (FI, T(C) = 18 K), for one crystal structure of [{Mn(II)(D/L-NH2ala)}3{Mn(III)(CN)6}]·3H2O obtained from [Mn(CN)6](3-) and D/L-aminoalanine, in contrast to one MGS for [{Mn(II)(L-NH2ala)}3{Cr(III)(CN)6}]·3H2O. They consist of three Mn(NH2ala) helical chains bridged by M(III)(CN)6 to give the framework with disordered water molecules in channels and between the M(III)(CN)6. Both MGS are characterized by a negative Weiss constant, bifurcation in ZFC-FC magnetizations, blocking of the moments, both components of the ac susceptibilities, and hysteresis. They differ in the critical temperatures, absolute magnetization for 5 Oe FC (lack of spontaneous magnetization for the SG), and the shapes of the hysteresis and coercive fields. While isotropic pressure increases both T(crit) and the magnetizations linearly and reversibly in each case, dehydration progressively transforms the FI into the SG as followed by concerted in situ magnetic measurements and single-crystal diffraction. The relative strengths of the two moderate Mn(III)-CN-Mn(II) antiferromagnetic (J1 and J2), the weak Mn(II)-OCO-Mn(II) (J3), and Dzyaloshinkii-Moriya antisymmetric (DM) interactions generate the two sets of characters. Examination of the bond lengths and angles for several crystals and their corresponding magnetic properties reveals a correlation between the distortion of Mn(III)(CN)6 and the MGS. SG is favored by higher magnetic anisotropy by less distorted Mn(III)(CN)6 in good accordance with the Mn-Cr system. This conclusion is also born out of the magnetization measurements on orientated single crystals with fields parallel and perpendicular to the unique c axis of the hexagonal space group. PMID:26893217

  9. An enzyme-free and resettable platform for the construction of advanced molecular logic devices based on magnetic beads and DNA.

    PubMed

    Zhang, Siqi; Wang, Kun; Huang, Congcong; Li, Zhenyu; Sun, Ting; Han, De-Man

    2016-08-25

    A series of multiple logic circuits based on magnetic beads and DNA are constructed to perform resettable nonarithmetic functions, including a digital comparator, 4-to-2 encoder and 2-to-3 decoder, 2-to-1 encoder and 1-to-2 decoder. The signal reporter is composed of a G-quadruplex/NMM complex and a AuNP-surface immobilized molecular beacon. It is the first time that the designed DNA-based nonarithmetic nanodevices can share the same DNA platform with a reset function, which has great potential application in information processing at the molecular level. Another novel feature of the designed system is that the developed nanodevices are operated on a simple DNA/magnetic bead platform and share a constant threshold setpoint without the assistance of any negative logic conversion. The reset function is realized by heating the output system and the magnetic separation of the computing modules. Due to the biocompatibility and design flexibility of DNA, these investigations may provide a new route towards the development of resettable advanced logic circuits in biological and biomedical fields. PMID:27524500

  10. Nontrivial magnetoresistive behavior of a single-wall carbon nanotube with an attached molecular magnet

    NASA Astrophysics Data System (ADS)

    Płomińska, Anna; Weymann, Ireneusz

    2015-11-01

    The spin-resolved transport properties of a single-wall carbon nanotube quantum dot, with an attached single molecular magnet, are studied theoretically. With the aid of the real-time diagrammatic technique in the lowest-order perturbation expansion with respect to the tunnel coupling, the current, differential conductance, and the tunnel magnetoresistance (TMR) are determined in both the linear and nonlinear response regimes. It is shown that transport properties depend greatly on both the shell filling sequence of the carbon nanotube and the type of exchange interaction between the molecular magnet and nanotube. This results in highly nontrivial behavior of the TMR, which is especially visible in the low bias voltage regime. Depending on the gate voltage and parameters of the system, we find transport regimes where either a greatly enhanced or negative TMR develops. The mechanism leading to such behavior is associated with nonequilibrium spin accumulation, which builds up in the antiparallel magnetic configuration of the device. We show that it is crucial whether the spin accumulation occurs in the highest-weight spin states or in states with lower spin values. While in the former case it leads to enhanced TMR, in the latter case it may result in negative tunnel magnetoresistance. In addition, we analyze how the above effects depend on the magnitude of the molecular magnet's spin, and show that this dependence is generally nonmonotonic.

  11. Magnetic deep eutectic solvents molecularly imprinted polymers for the selective recognition and separation of protein.

    PubMed

    Liu, Yanjin; Wang, Yuzhi; Dai, Qingzhou; Zhou, Yigang

    2016-09-14

    A novel and facile magnetic deep eutectic solvents (DES) molecularly imprinted polymers (MIPs) for the selective recognition and separation of Bovine hemoglobin (BHb) was prepared. The new-type DES was adopted as the functional monomer which would bring molecular imprinted technology to a new direction. The amounts of DES were optimized. The obtained magnetic DES-MIPs were characterized with fourier transform infrared spectrometry (FT-IR), thermogravimetric analysis (TGA), field emission scanning electron microscope (FESEM), dynamic light scattering (DLS), elemental analysis and vibrating sample magnetometer (VSM). The results suggested that the imprinted polymers were successfully formed and possessed a charming magnetism. The maximum adsorption capability (Qmax) and dissociation constant (KL) were analyzed by Langmuir isotherms (R(2) = 0.9983) and the value were estimated to be 175.44 mg/g and 0.035 mg/mL for the imprinted particles. And the imprinted particles showed a high imprinting factor of 4.77. In addition, the magnetic DES-MIPs presented outstanding recognition specificity and selectivity so that it can be utilized to separate template protein from the mixture of proteins and real samples. Last but not least, the combination of deep eutectic solvents and molecular imprinted technology in this paper provides a new perspective for the recognition and separation of proteins. PMID:27566352

  12. Effects of electronic correlations and magnetic field on a molecular ring out of equilibrium

    NASA Astrophysics Data System (ADS)

    Nuss, Martin; von der Linden, Wolfgang; Arrigoni, Enrico

    2014-04-01

    We study the effects of electron-electron interactions on the steady-state characteristics of a hexagonal molecular ring in a magnetic field as a model for a benzene molecular junction. The system is driven out of equilibrium by applying a bias voltage across two metallic leads. We employ a model Hamiltonian approach to evaluate the effects of on-site as well as nearest-neighbor density-density-type interactions in a physically relevant parameter regime. Results for the steady-state current, charge density, and magnetization in three different junction setups (para, meta, and ortho) are presented. Our findings indicate that interactions beyond the mean-field level renormalize voltage thresholds as well as current plateaus. Electron-electron interactions lead to substantial charge redistribution as compared to the mean-field results. We identify a strong response of the circular current on the electronic structure of the metallic leads. Our results are obtained by steady-state cluster perturbation theory, a systematically improvable approximation to study interacting molecular junctions out of equilibrium, even in magnetic fields. Within this framework, general expressions for the current, charge density, and magnetization in the steady state are derived. The method is flexible and fast and can straightforwardly be applied to effective models as obtained from ab initio calculations.

  13. Molecular Imaging of Activated Platelets Allows the Detection of Pulmonary Embolism with Magnetic Resonance Imaging

    PubMed Central

    Heidt, Timo; Ehrismann, Simon; Hövener, Jan-Bernd; Neudorfer, Irene; Hilgendorf, Ingo; Reisert, Marco; Hagemeyer, Christoph E.; Zirlik, Andreas; Reinöhl, Jochen; Bode, Christoph; Peter, Karlheinz; von Elverfeldt, Dominik; von zur Muhlen, Constantin

    2016-01-01

    Early and reliable detection of pulmonary embolism (PE) is critical for improving patient morbidity and mortality. The desire for low-threshold screening for pulmonary embolism is contradicted by unfavorable radiation of currently used computed tomography or nuclear techniques, while standard magnetic resonance imaging still struggles to provide sufficient diagnostic sensitivity in the lung. In this study we evaluate a molecular-targeted contrast agent against activated platelets for non-invasive detection of murine pulmonary thromboembolism using magnetic resonance imaging. By intravenous injection of human thrombin, pulmonary thromboembolism were consistently induced as confirmed by immunohistochemistry of the lung. Magnetic resonance imaging after thrombin injection showed local tissue edema in weighted images which co-localized with the histological presence of pulmonary thromboembolism. Furthermore, injection of a functionalized contrast agent targeting activated platelets provided sensitive evidence of focal accumulation of activated platelets within the edematous area, which, ex vivo, correlated well with the size of the pulmonary embolism. In summary, we here show delivery and specific binding of a functionalized molecular contrast agent against activated platelets for targeting pulmonary thromboembolism. Going forward, molecular imaging may provide new opportunities to increase sensitivity of magnetic resonance imaging for detection of pulmonary embolism. PMID:27138487

  14. Molecular Imaging of Activated Platelets Allows the Detection of Pulmonary Embolism with Magnetic Resonance Imaging.

    PubMed

    Heidt, Timo; Ehrismann, Simon; Hövener, Jan-Bernd; Neudorfer, Irene; Hilgendorf, Ingo; Reisert, Marco; Hagemeyer, Christoph E; Zirlik, Andreas; Reinöhl, Jochen; Bode, Christoph; Peter, Karlheinz; von Elverfeldt, Dominik; von Zur Muhlen, Constantin

    2016-01-01

    Early and reliable detection of pulmonary embolism (PE) is critical for improving patient morbidity and mortality. The desire for low-threshold screening for pulmonary embolism is contradicted by unfavorable radiation of currently used computed tomography or nuclear techniques, while standard magnetic resonance imaging still struggles to provide sufficient diagnostic sensitivity in the lung. In this study we evaluate a molecular-targeted contrast agent against activated platelets for non-invasive detection of murine pulmonary thromboembolism using magnetic resonance imaging. By intravenous injection of human thrombin, pulmonary thromboembolism were consistently induced as confirmed by immunohistochemistry of the lung. Magnetic resonance imaging after thrombin injection showed local tissue edema in weighted images which co-localized with the histological presence of pulmonary thromboembolism. Furthermore, injection of a functionalized contrast agent targeting activated platelets provided sensitive evidence of focal accumulation of activated platelets within the edematous area, which, ex vivo, correlated well with the size of the pulmonary embolism. In summary, we here show delivery and specific binding of a functionalized molecular contrast agent against activated platelets for targeting pulmonary thromboembolism. Going forward, molecular imaging may provide new opportunities to increase sensitivity of magnetic resonance imaging for detection of pulmonary embolism. PMID:27138487

  15. On the valve nature of a monolayer of aligned molecular magnets in tunneling spin-polarized electrons: Towards organic molecular spintronics

    SciTech Connect

    Chakrabarti, Sudipto; Pal, Amlan J.

    2014-01-06

    We form a monolayer of magnetic organic molecules and immobilize their moments pointing either upwards or downwards with respect to the substrate through an electrostatic-binding process. Such a monolayer is probed with a scanning tunneling microscope tip, which is also magnetized with the magnetization vector pointing towards (or away from) apex of the tip. From spin-polarized tunneling current, we show that the current was higher when magnetization vectors of the tip and molecules were parallel as compared to that when they were anti-parallel. We show that for tunneling of spin-polarized electrons, aligned organic molecular magnets can act as a valve.

  16. Multicolor well-composed pictures

    NASA Astrophysics Data System (ADS)

    Latecki, Longin J.

    1995-01-01

    As was noted early in the history of computer vision, using the same adjacency relation for the entire digital picture leads to so-called `paradoxes' related to the Jordan Curve Theorem. The most popular idea to avoid these paradoxes in binary images was using different adjacency relations for the foreground and the background: 8-adjacency for black points and 4-adjacency for white points, or vice versa. This idea cannot be extended in a straightforward way to multicolor pictures. In this paper a solution is presented which guarantees avoidance of the connectivity paradoxes related to the Jordan Curve Theorem for all multicolor pictures. Only one connectedness relation is used for the entire digital picture, i.e., for every component of every color. The idea is not to allow a certain `critical configuration' which can be detected locally to occur in digital pictures; such pictures are called `well-composed.' Well-composed pictures have very nice topological properties. For example, the Jordan Curve Theorem holds and the Euler characteristic is locally computable. This implies that properties of algorithms used in computer vision can be stated and proved in a clear way, and that the algorithms themselves become simpler and faster. Moreover, if a digitization process is guaranteed to preserve topology, then the obtained digital pictures must be well-composed.

  17. On-chip magnetic separation of superparamagnetic beads for integrated molecular analysis

    NASA Astrophysics Data System (ADS)

    Florescu, Octavian; Wang, Kevan; Au, Patrick; Tang, Jimmy; Harris, Eva; Beatty, P. Robert; Boser, Bernhard E.

    2010-03-01

    We have demonstrated a postprocessed complementary metal oxide semiconductor (CMOS) integrated circuit (IC) capable of on-chip magnetic separation, i.e., removing via magnetic forces the nonspecifically bound magnetic beads from the detection area on the surface of the chip. Initially, 4.5 μm wide superparamagnetic beads sedimenting out of solution due to gravity were attracted to the detection area by a magnetic concentration force generated by flowing current through a conductor embedded in the IC. After sedimentation, the magnetic beads that did not bind strongly to the functionalized surface of the IC through a specific biochemical complex were removed by a magnetic separation force generated by flowing current through another conductor placed laterally to the detection area. As the spherical bead pivoted on the surface of the chip, the lateral magnetic force was further amplified by mechanical leveraging, and 50 mA of current flowing through the separation conductor placed 18 μm away from the bead resulted in 7.5 pN of tensile force on the biomolecular tether immobilizing the bead. This force proved high enough to break nonspecific interactions while leaving specific antibody-antigen bonds intact. A sandwich capture immunoassay on purified human immunoglobulin G showed strong correlation with a control enzyme linked immunosorbent assay and a detection limit of 10 ng/ml or 70 pM. The beads bound to the detection area after on-chip magnetic separation were detected optically. To implement a fully integrated molecular diagnostics platform, the on-chip magnetic separation functionality presented in this work can be readily combine with state-of-the art CMOS-based magnetic bead detection technology.

  18. Spectroscopic Investigation of the Origin of Magnetic Bistability in Molecular Nanomagnets

    NASA Astrophysics Data System (ADS)

    van Slageren, Joris

    Molecular nanomagnets (MNMs) are coordination complexes consisting of one of more transition metal and/or f-element ions bridged and surrounded by organic ligands. Some of these can be magnetized in a magnetic field, and remain magnetized after the field is switched off. Because of this, MNMs have been proposed for magnetic data storage applications, where up to 1000 times higher data densities than currently possible can be obtained. Other MNMs were shown to display quantum coherence, and, as a consequence, are suitable as quantum bits. Quantum bits are the building blocks of a quantum computer, which will be able to carry out calculations that will never be possible with a conventional computer. The magnetic bistability of MNMs originates from the magnetic anisotropy of the magnetic ions, which creates an energy barrier between up and down orientations of the magnetic moment. Currently, most work in the area focuses on complexes of either lanthanide ions or low-coordinate transition metal ions. Synthetic chemical efforts have led to a large number of novel materials, but the rate of improvement has been slow. Therefore a better understanding of the origin of the magnetic anisotropy is clearly necessary. To this end we have applied a wide range of advanced spectroscopic techniques, ranging from different electron spin resonance techniques at frequencies up to the terahertz domain to optical techniques, including luminescence and magnetic circular dichroism spectroscopy. We will discuss two examples, one from the area of lanthanide MNMs, one a transition metal MNM (unpublished). This work was financially supported by DFG, DAAD and COST CM1006 EUFEN.

  19. Magnetic trapping with simultaneous photoacoustic detection of molecularly targeted rare circulating tumor cells

    NASA Astrophysics Data System (ADS)

    Wei, Chen-Wei; Xia, Jinjun; Pelivanov, Ivan M.; Hu, Xiaoge; Gao, Xiaohu; O'Donnell, Matthew

    2013-03-01

    Photoacoustic (PA) imaging has been widely used in molecular imaging to detect diseased cells by targeting them with nanoparticle-based contrast agents. However, the sensitivity and specificity are easily degraded because contrast agent signals can be masked by the background. Magnetomotive photoacoustic imaging uses a new type of multifunctional composite particle combining an optically absorptive gold nanorod core and magnetic nanospheres, which can potentially accumulate and concentrate targeted cells while simultaneously enhancing their specific contrast compared to background signals. In this study, HeLa cells molecularly targeted using nanocomposites with folic acid mimicking targeted rare circulating tumor cells (CTCs) were circulated at a 6 ml/min flow rate for trapping and imaging studies. Preliminary results show that the cells accumulate rapidly in the presence of an externally applied magnetic field produced by a dual magnet system. The sensitivity of the current system can reach up to 1 cell/ml in clear water. By manipulating the trapped cells magnetically, the specificity of detecting cells in highly absorptive ink solution can be enhanced with 16.98 dB background suppression by applying motion filtering on PA signals to remove unwanted background signals insensitive to the magnetic field. The results appear promising for future preclinical studies on a small animal model and ultimate clinical detection of rare CTCs in the vasculature.

  20. Enhancing the magnetic anisotropy of maghemite nanoparticles via the surface coordination of molecular complexes

    NASA Astrophysics Data System (ADS)

    Prado, Yoann; Daffé, Niéli; Michel, Aude; Georgelin, Thomas; Yaacoub, Nader; Grenèche, Jean-Marc; Choueikani, Fadi; Otero, Edwige; Ohresser, Philippe; Arrio, Marie-Anne; Cartier-Dit-Moulin, Christophe; Sainctavit, Philippe; Fleury, Benoit; Dupuis, Vincent; Lisnard, Laurent; Fresnais, Jérôme

    2015-12-01

    Superparamagnetic nanoparticles are promising objects for data storage or medical applications. In the smallest--and more attractive--systems, the properties are governed by the magnetic anisotropy. Here we report a molecule-based synthetic strategy to enhance this anisotropy in sub-10-nm nanoparticles. It consists of the fabrication of composite materials where anisotropic molecular complexes are coordinated to the surface of the nanoparticles. Reacting 5 nm γ-Fe2O3 nanoparticles with the [CoII(TPMA)Cl2] complex (TPMA: tris(2-pyridylmethyl)amine) leads to the desired composite materials and the characterization of the functionalized nanoparticles evidences the successful coordination--without nanoparticle aggregation and without complex dissociation--of the molecular complexes to the nanoparticles surface. Magnetic measurements indicate the significant enhancement of the anisotropy in the final objects. Indeed, the functionalized nanoparticles show a threefold increase of the blocking temperature and a coercive field increased by one order of magnitude.

  1. Magnetic molecularly imprinted polymers for spectrophotometric quantification of curcumin in food.

    PubMed

    Liu, Xiuying; Zhu, Lijie; Gao, Xue; Wang, Yuxin; Lu, Haixia; Tang, Yiwei; Li, Jianrong

    2016-07-01

    Herein, we present a simple and rapid method for monitoring curcumin in food samples using a magnetic molecularly imprinted technique combined with ultraviolet-visible (UV-Vis) spectrophotometry. Magnetic molecularly imprinted polymers (mag-MIPs) were first synthesized by fabricating MIPs on to the surface of Fe3O4 nanobeads using curcumin as a template and methacrylic acid as a functional monomer. The obtained mag-MIPs were evaluated in detail with different techniques (such as binding isotherm, Scatchard analysis, and selectivity) and various adsorption experiments. Finally, mag-MIPs were constructed and UV-Vis spectrophotometry was used to quantify curcumin under optimized conditions. Good recoveries between 79.37% and 88.89% were obtained with the limits of detection and quantification of 1.31 and 4.38μg/mL, respectively. PMID:26920299

  2. EFFECTS OF MAGNETIC FIELD STRENGTH AND ORIENTATION ON MOLECULAR CLOUD FORMATION

    SciTech Connect

    Heitsch, Fabian; Hartmann, Lee W.; Stone, James M.

    2009-04-10

    We present a set of numerical simulations addressing the effects of magnetic field strength and orientation on the flow-driven formation of molecular clouds. Fields perpendicular to the flows sweeping up the cloud can efficiently prevent the formation of massive clouds but permit the buildup of cold, diffuse filaments. Fields aligned with the flows lead to substantial clouds, whose degree of fragmentation and turbulence strongly depends on the background field strength. Adding a random field component leads to a 'selection effect' for molecular cloud formation: high column densities are only reached at locations where the field component perpendicular to the flows is vanishing. Searching for signatures of colliding flows should focus on the diffuse, warm gas, since the cold gas phase making up the cloud will have lost the information about the original flow direction because the magnetic fields redistribute the kinetic energy of the inflows.

  3. Spatial distribution of phases during gradual magnetostructural transitions in copper(II)-nitroxide based molecular magnets.

    PubMed

    Fedin, Matvey V; Veber, Sergey L; Bagryanskaya, Elena G; Romanenko, Galina V; Ovcharenko, Victor I

    2015-11-21

    Copper(ii)-nitroxide based molecular magnets Cu(hfac)2L(R) exhibit thermally-induced transitions between high- and low-temperature (HT/LT) magnetostructural states. In this work we report the first study on the spatial distribution of HT/LT phases during gradual transitions in these compounds. We explore the possibility of domain formation at intermediate temperatures, which has never been addressed before. For this purpose, we reexamine the available electron paramagnetic resonance (EPR) and X-ray diffraction data, and perform numerical calculations of EPR spectra for different models of exchange-coupled networks. A thorough analysis shows that during gradual transitions, molecular magnets Cu(hfac)2L(R) represent solid solutions of disordered HT and LT phases, and the formation of single-phase domains larger than a few nanometers in size is unlikely. PMID:26461851

  4. Evidence for entanglement at high temperatures in an engineered molecular magnet

    SciTech Connect

    Reis, Mario S; Soriano, Stephane; Moreira Dos Santos, Antonio F; Sales, Brian C; Soares-Pinto, D O; Brandao, Paula

    2012-01-01

    The molecular compound [Fe-2(mu(2)-oxo)(C3H4N2)(6)(C2O4)(2)] was designed and synthesized for the first time and its structure was determined using single-crystal X-ray diffraction. The magnetic susceptibility of this compound was measured from 2 to 300 K. The analysis of the susceptibility data using protocols developed for other spin singlet ground-state systems indicates that the quantum entanglement would remain at temperatures up to 732 K, significantly above the highest entanglement temperature reported to date. The large gap between the ground state and the first-excited state (282 K) suggests that the spin system may be somewhat immune to decohering mechanisms. Our measurements strongly suggest that molecular magnets are promising candidate platforms for quantum information processing.

  5. New OH Zeeman Measurements of Magnetic Field Strengths in Molecular Clouds

    NASA Astrophysics Data System (ADS)

    Bourke, Tyler L.; Myers, Philip C.; Robinson, Garry; Hyland, A. R.

    2001-06-01

    We present the results of a new survey of 23 molecular clouds for the Zeeman effect in OH undertaken with the Australia Telescope National Facility Parkes 64 m radio telescope and the National Radio Astronomy Observatory Green Bank 43 m radio telescope. The Zeeman effect was clearly detected in the cloud associated with the H II region RCW 38, with a field strength of 38+/-3 μG, and possibly detected in a cloud associated with the H II region RCW 57, with a field strength of -203+/-24 μG. The remaining 21 measurements give formal upper limits to the magnetic field strength, with typical 1 σ sensitivities less than 20 μG. For 22 of the molecular clouds we are also able to determine the column density of the gas in which we have made a sensitive search for the Zeeman effect. We combine these results with previous Zeeman studies of 29 molecular clouds, most of which were compiled by Crutcher, for a comparison of theoretical models with the data. This comparison implies that if the clouds can be modeled as initially spherical with uniform magnetic fields and densities that evolve to their final equilibrium state assuming flux freezing, then the typical cloud is magnetically supercritical, as was found by Crutcher. If the clouds can be modeled as highly flattened sheets threaded by uniform perpendicular fields, then the typical cloud is approximately magnetically critical, in agreement with Shu et al., but only if the true values of the field for the nondetections are close to the 3 σ upper limits. If instead these values are significantly lower (for example, similar to the 1 σ limits), then the typical cloud is generally magnetically supercritical. When all observations of the Zeeman effect are considered, the single-dish detection rate of the OH Zeeman effect is relatively low. This result may be due to low mean field strengths, but a more realistic explanation may be significant field structure within the beam. As an example, for clouds associated with H II

  6. [Preparation and characterization of core-shell structural magnetic molecularly imprinted polymers for nafcillin].

    PubMed

    Chen, Langxing; Liu, Yuxing; He, Xiwen; Zhang, Yukui

    2015-05-01

    The uniform core-shell nanostructured magnetic molecularly imprinted polymers (MIPs) were synthesized using antibiotic nafcillin as a template. In this protocol, the magnetite nanoparticles (NPs) were synthesized by the solvothermal reaction firstly. Subsequently, the vinyl groups were grated onto silica-modified Fe3O4 surface by 3-methacryloyloxypropyltrimethoxysilane via sol-gel method. Finally, the nafcillin-MIPs film was formed on the surface of Fe3O4 @ SiO2 by the copolymerization of vinyl end group with functional monomer, methacrylic acid, cross-linking agent, ethylene glycol dimethacrylate, the initiator azo-bis-isobutyronitrile and template molecule. The morphological and magnetic characteristics of the MIPs were characterized by transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction and vibrating sample magnetometer. The obtained spherical magnetic MIPs with diameters of about 320 nm had good monodispersity. The static binding experiment was carried out to evaluate the properties of magnetic MIPs and non imprinted polymers (NIPs). The results demonstrated that the magnetic MIPs had high adsorption capacity to template and good selectivity. The imprinting factor and the maximum adsorption capacity of Fe3O4 @ MIPs to nafcillin were 2.46 and 50.7 mg/g, respectively. It is expected that the prepared magnetic MIPs could be used for the enrichment of nafcillin in complex samples. PMID:26387205

  7. Structural and Magnetic Characterization of EuTe/SnTe Superlattices Grown by Molecular Beam Epitaxy

    SciTech Connect

    Diaz, B.; Abramof, E.; Rappl, P. H. O.; Granado, E.; Chitta, V. A.; Henriques, A. B.; Oliveira, N. F. Jr.

    2010-01-04

    Here we investigate the structural and magnetic properties of 24 repetitions EuTe/SnTe superlattices (SLs), with 3 monolayers (ML) EuTe films and SnTe thicknesses between 13 and 36 ML. The SLs were grown by molecular beam epitaxy on 3 {mu}m SnTe buffer layers, grown on top of (111)BaF{sub 2} substrates. High resolution x-ray diffraction measurements indicated that the SLs with thicker SnTe layers have higher structural quality. This is due to the SnTe growth mode on EuTe, which starts in islands and evolves to layer-by-layer. The magnetic diffraction peak observed for the higher quality SLs proved the existence of antiferromagnetic order within the individual EuTe layers. Decreasing the width of the non-magnetic SnTe layers resulted in rougher interfaces, and the fading of the magnetic peak signal. The magnetization versus applied field curves indicated that the magnetic moments of SLs with thinner SnTe layers were also harder to align along the field direction. We interpret our results considering the loss of Eu neighbors, related with the increasing roughness of the SL interfaces.

  8. Hybrid Molecular and Spin Dynamics Simulations for Ensembles of Magnetic Nanoparticles for Magnetoresistive Systems

    PubMed Central

    Teich, Lisa; Schröder, Christian

    2015-01-01

    The development of magnetoresistive sensors based on magnetic nanoparticles which are immersed in conductive gel matrices requires detailed information about the corresponding magnetoresistive properties in order to obtain optimal sensor sensitivities. Here, crucial parameters are the particle concentration, the viscosity of the gel matrix and the particle structure. Experimentally, it is not possible to obtain detailed information about the magnetic microstructure, i.e., orientations of the magnetic moments of the particles that define the magnetoresistive properties, however, by using numerical simulations one can study the magnetic microstructure theoretically, although this requires performing classical spin dynamics and molecular dynamics simulations simultaneously. Here, we present such an approach which allows us to calculate the orientation and the trajectory of every single magnetic nanoparticle. This enables us to study not only the static magnetic microstructure, but also the dynamics of the structuring process in the gel matrix itself. With our hybrid approach, arbitrary sensor configurations can be investigated and their magnetoresistive properties can be optimized. PMID:26580623

  9. Molecular Location Sensing Approach by Anisotropic Magnetism of an Endohedral Metallofullerene.

    PubMed

    Takano, Yuta; Tashita, Ryo; Suzuki, Mitsuaki; Nagase, Shigeru; Imahori, Hiroshi; Akasaka, Takeshi

    2016-06-29

    Location recognition at the molecular scale provides valuable information about the nature of functional molecular materials. This study presents a novel location sensing approach based on an endohedral metallofullerene, Ce@C82, using its anisotropic magnetic properties, which lead to temperature-dependent paramagnetic shifts in (1)H NMR spectra. Five site-isomers of Ce@C82CH2-3,5-C6H3Me2 were synthesized to demonstrate the spatial sensing ability of Ce@C82. Single-crystal structures, absorption spectra, and density functional theory calculations were used to select the plausible addition positions in the radical coupling reaction, which preferentially happens on the carbon atoms with high electron density of the singly occupied molecular orbital (SOMO) and positive charge. Temperature-dependent NMR measurements demonstrated unique paramagnetic shifts of the (1)H peaks, which were derived from the anisotropic magnetism of the f-electron in the Ce atom of the isomers. It was found that the magnetic anisotropy axes can be easily predicted by theoretical calculations using the Gaussian 09 package. Further analysis revealed that the temperature-dependent trend in the shifts is clearly predictable from the distance and relative position of the proton from the Ce atom. Hence, the Ce-encapsulated metallofullerene Ce@C82 can provide spatial location information about nearby atoms through the temperature-dependent paramagnetic shifts of its NMR signals. It can act as a molecular probe for location sensing by utilizing the anisotropic magnetism of the encapsulated Ce atom. The potentially low toxicity and stability of the endohedral fullerene would make Ce@C82 suitable for applications in biology and material science. PMID:27314267

  10. [Preparation and applications of 4-methyl imidazole magnetic surface molecularly imprinted polymers].

    PubMed

    Qi, Yuxia; Zhao, Lijuan; Ma, Meihua; Wei, Chanling; Li, Ya; Li, Wenjing; Gong, Bolin

    2015-12-01

    The magnetic surface molecularly imprinted polymers (MIPs) with specific recognition of 4-methyl imidazole (4-MI) were prepared by using 4-MI as template molecule, methacrylic acid (MAA) as functional monomer and Fe3O4 as magnetic fluid. The polymers were characterized by of Fourier transform infrared spectrometer (FT-IR) analysis, X-ray diffraction (XRD) analysis, transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM). The results demonstrated that an imprinted polymer layer was successfully coated onto the surface of modified Fe3O4 nanomaterials, resulting in a narrow diameter distribution and good magnetic responsibility. The ultraviolet (UV) spectrophotometry was used to demonstrate the interaction between 4-MI and MAA. It was found that one 4-MI molecule was entrapped by one MAA molecule, which was the main existing form of subject and object. By UV spectrophotometric method to study the adsorption performance of magnetic molecularly imprinted polymers, the specific adsorption equilibrium and selectivity were evaluated by batch rebinding studies. The Scatchard analysis showed that there were two kinds of binding sites in the Fe3O4 @ (4-MI-MIP). The corresponding maximum adsorption capacities of 4-MI onto Fe3O4 @ (4-MI-MIP) were 40.31 mg/g and 23.07 mg/g, and the dissociation constants were 64.85 mg/L and 30.41 mg/L, respectively. The kinetic experimental data were correlated with second-order kinetic model. The magnetic molecularly imprinted polymers were used for the adsorption of 4-methyl imidazole in environmental water samples, and good results were obtained. PMID:27097456

  11. M S MOLECULARES Rumo aos limites da miniaturiza o - (Molecular Magnets - towards the limits of miniaturization)

    SciTech Connect

    Reis, Mario S; Moreira Dos Santos, Antonio F

    2010-01-01

    Por s culos, acreditou-se que o magnetismo s se manifestava em metais, como aqueles contendo ferro; hoje, a imagem mais comum de um m talvez seja a daquelas plaquinhas flex veis coladas geladeira com propagandas dos mais diversos tipos. O leitor conseguiria imaginar um material puramente org nico daqueles que formam os seres vivos como magn tico? E m s do tamanho de mol culas? fato: ambos existem. Esses novos materiais, conhecidos como magnetos moleculares, descobertos e desenvolvidos em v rios laborat rios do mundo, j re nem longa lista de aplica es, do tratamento do c ncer a refrigeradores ecol gicos, passando pela transmiss o de eletricidade sem perda de calor e a fabrica o de computadores extremamente velozes.

  12. Formal relations connecting different approaches to calculate relativistic effects on molecular magnetic properties

    NASA Astrophysics Data System (ADS)

    Zaccari, D. G.; Ruiz de Azúa, M. C.; Melo, J. I.; Giribet, C. G.

    2006-02-01

    In the present work a set of formal relations connecting different approaches to calculate relativistic effects on magnetic molecular properties are proven. The linear response (LR) within the elimination of the small component (ESC), Breit Pauli, and minimal-coupling approaches are compared. To this end, the leading order ESC reduction of operators within the minimal-coupling four-component approach is carried out. The equivalence of all three approaches within the ESC approximation is proven. It is numerically verified for the NMR nuclear-magnetic shielding tensor taking HX and CH3X (X =Br,I) as model compounds. Formal relations proving the gauge origin invariance of the full relativistic effect on the NMR nuclear-magnetic shielding tensor within the LR-ESC approach are presented.

  13. Electron paramagnetic resonance linewidths and line shapes for the molecular magnets Fe8 and Mn12

    NASA Astrophysics Data System (ADS)

    Park, Kyungwha; Novotny, M. A.; Dalal, N. S.; Hill, S.; Rikvold, P. A.

    2002-05-01

    We study theoretically electron paramagnetic resonance (EPR) linewidths for single crystals of the molecular magnets Fe8 and Mn12 as functions of energy eigenstates Ms, frequency, and temperature when a magnetic field along the easy axis is swept at fixed excitation frequency. This work was motivated by recent EPR experiments. To calculate the linewidths, we use density-matrix equations, including dipolar interactions and distributions of the uniaxial anisotropy parameter D and the Landé g factor. Our calculated linewidths agree well with the experimental data. We also examine the line shapes of the EPR spectra due to local rotations of the magnetic anisotropy axes caused by defects in samples. Our preliminary results predict that this effect leads to asymmetry in the EPR spectra.

  14. First MHD simulation of collapse and fragmentation of magnetized molecular cloud cores

    NASA Astrophysics Data System (ADS)

    Machida, Masahiro N.; Tomisaka, Kohji; Matsumoto, Tomoaki

    2004-02-01

    This is the first paper about fragmentation and mass outflow in molecular clouds by using three-dimensional magnetohydrodynamical (MHD) nested-grid simulations. The binary star formation process is studied, paying particular attention to the fragmentation of a rotating magnetized molecular cloud. We assume an isothermal rotating and magnetized cylindrical cloud in hydrostatic balance. Non-axisymmetric as well as axisymmetric perturbations are added to the initial state and the subsequent evolutions are studied. The evolution is characterized by three parameters: the amplitude of the non-axisymmetric perturbations, the rotation speed and the magnetic field strength. As a result, it is found that non-axisymmetry hardly evolves in the early phase, but begins to grow after the gas contracts and forms a thin disc. Disc formation is strongly promoted by the rotation speed and the magnetic field strength. There are two types of fragmentation: that from a ring and that from a bar. Thin adiabatic cores fragment if their thickness is less than 1/4 of the radius. For the fragments to survive, they should be formed in a heavily elongated barred core or a flat round disc. In the models showing fragmentation, outflows from respective fragments are found as well as those driven by the rotating bar or the disc.

  15. LONG-LIVED MAGNETIC-TENSION-DRIVEN MODES IN A MOLECULAR CLOUD

    SciTech Connect

    Basu, Shantanu; Dapp, Wolf B. E-mail: wdapp@uwo.c

    2010-06-10

    We calculate and analyze the longevity of magnetohydrodynamic (MHD) wave modes that occur in the plane of a magnetic thin sheet. Initial turbulent conditions applied to a magnetically subcritical cloud are shown to lead to relatively rapid energy decay if ambipolar diffusion is introduced at a level corresponding to partial ionization primarily by cosmic rays. However, in the flux-freezing limit, as may be applicable to photoionized molecular cloud envelopes, the turbulence persists at 'nonlinear' levels in comparison with the isothermal sound speed c {sub s}, with one-dimensional rms material motions in the range of {approx} 2 c {sub s}-5 c {sub s} for cloud sizes in the range of {approx} 2 pc-16 pc. These fluctuations persist indefinitely, maintaining a significant portion of the initial turbulent kinetic energy. We find the analytic explanation for these persistent fluctuations. They are magnetic-tension-driven modes associated with the interaction of the sheet with the external magnetic field. The phase speed of such modes is quite large, allowing residual motions to persist without dissipation in the flux-freezing limit, even as they are nonlinear with respect to the sound speed. We speculate that long-lived large-scale MHD modes such as these may provide the key to understanding observed supersonic motions in molecular clouds.

  16. Hybrid Materials Based on Magnetic Layered Double Hydroxides: A Molecular Perspective.

    PubMed

    Abellán, Gonzalo; Martí-Gastaldo, Carlos; Ribera, Antonio; Coronado, Eugenio

    2015-06-16

    Design of functional hybrids lies at the very core of synthetic chemistry as it has enabled the development of an unlimited number of solids displaying unprecedented or even improved properties built upon the association at the molecular level of quite disparate components by chemical design. Multifunctional hybrids are a particularly appealing case among hybrid organic/inorganic materials. Here, chemical knowledge is used to deploy molecular components bearing different functionalities within a single solid so that these properties can coexist or event interact leading to unprecedented phenomena. From a molecular perspective, this can be done either by controlled assembly of organic/inorganic molecular tectons into an extended architecture of hybrid nature or by intercalation of organic moieties within the empty channels or interlamellar space offered by inorganic solids with three-dimensional (MOFs, zeolites, and mesoporous hosts) or layered structures (phosphates, silicates, metal dichalcogenides, or anionic clays). This Account specifically illustrates the use of layered double hydroxides (LDHs) in the preparation of magnetic hybrids, in line with the development of soft inorganic chemistry processes (also called "Chimie Douce"), which has significantly contributed to boost the preparation hybrid materials based on solid-state hosts and subsequent development of applications. Several features sustain the importance of LDHs in this context. Their magnetism can be manipulated at a molecular level by adequate choice of constituting metals and interlayer separation for tuning the nature and extent of magnetic interactions across and between planes. They display unparalleled versatility in accommodating a broad range of anionic species in their interlamellar space that encompasses not only simple anions but chemical systems of increasing dimensionality and functionalities. Their swelling characteristics allow for their exfoliation in organic solvents with high

  17. The influence of molecular order and microstructure on the R2* and the magnetic susceptibility tensor.

    PubMed

    Wisnieff, Cynthia; Liu, Tian; Wang, Yi; Spincemaille, Pascal

    2016-06-01

    In this work, we demonstrate that in the presence of ordered sub-voxel structure such as tubular organization, biomaterials with molecular isotropy exhibits only apparent R2* anisotropy, while biomaterials with molecular anisotropy exhibit both apparent R2* and susceptibility anisotropy by means of susceptibility tensor imaging (STI). To this end, R2* and STI from gradient echo magnitude and phase data were examined in phantoms made from carbon fiber and Gadolinium (Gd) solutions with and without intrinsic molecular order and sub-voxel structure as well as in the in vivo brain. Confidence in the tensor reconstructions was evaluated with a wild bootstrap analysis. Carbon fiber showed both apparent anisotropy in R2* and anisotropy in STI, while the Gd filled capillary tubes only showed apparent anisotropy on R2*. Similarly, white matter showed anisotropic R2* and magnetic susceptibility with higher confidence, while the cerebral veins displayed only strong apparent R2* tensor anisotropy. Ordered sub-voxel tissue microstructure leads to apparent R2* anisotropy, which can be found in both white matter tracts and cerebral veins. However, additional molecular anisotropy is required for magnetic susceptibility anisotropy, which can be found in white matter tracts but not in cerebral veins. PMID:26692502

  18. Substituent effect on formation of heterometallic molecular wheels: synthesis, crystal structure, and magnetic properties.

    PubMed

    Ni, Zhong-Hai; Zhang, Li-Fang; Tangoulis, Vassilis; Wernsdorfer, Wolfgang; Cui, Ai-Li; Sato, Osamu; Kou, Hui-Zhong

    2007-07-23

    The reaction of manganese(III) Schiff bases of the type salen(2-) (N,N'-ethylenebis(salicylideneaminato)) with X-substituted (X = CH(3), Cl) pyridinecarboxamide dicyanoferrite(III) [Fe(X-bpb)(CN)(2)](-) gave rise to a series of cyanide-bridged Mn(6)Fe(6) molecular wheels, [Mn(III)(salen)](6)[Fe(III)(bpmb)(CN)(2)](6) x 7H(2)O (1), [Mn(salen)](6)[Fe(bpClb)(CN)(2)](6) x 4H(2)O x 2CH(3)OH (2), [Mn(salen)](6)[Fe(bpdmb)(CN)(2)](6) x 10H(2)O x 5CH(3)OH (3), [Mn(5-Br(salpn))](6)[Fe(bpmb)(CN)(2)](6) x 24H(2)O x 8CH(3)CN (4), and [Mn(5-Cl(salpn))](6)[Fe(bpmb)(CN)(2)](6) x 25H(2)O x 5CH(3)CN (5). Compared with [Fe(bpb)(CN)(2)](-), which always gives rise to 1D or polynuclear species when reacting with Mn(III) Schiff bases, the introduction of substituents (X) to the bpb(2-) ligand has a driving force in formation of the novel wheel structure. Magnetic studies reveal that high-spin ground state S = 15 is present in the wheel compounds originated from the ferromagnetic Mn(III)-Fe(III) coupling. For the first time, the quantum Monte Carlo study has been used to modulate the magnetic susceptibility of the huge Mn(6)Fe(6) metallomacrocycles, showing that the magnetic coupling constants J range from 3.0 to 8.0 K on the basis of the spin Hamiltonian [Formula: see text]. Hysteresis loops for 1 have been observed below 0.8 K, indicative of a single-molecule magnet with a blocking temperature (TB) of 0.8 K. Molecular wheels 2-5 exhibit frequency dependence of alternating-current magnetic susceptibility under zero direct-current magnetic field, signifying the slow magnetization relaxation similar to that of 1. Significantly, an unprecedented archlike Mn(2)Fe(2) cluster, [Mn(5-Cl(salpn))](2)[Fe(bpmb)(CN)(2)](2) x 3H(2)O x CH(3)CN (6), has been isolated as an intermediate of the Mn(6)Fe(6) wheel 5. Ferromagnetic Mn(III)-Fe(III) coupling results in a high-spin S = 5 ground state. Combination of the high-spin state and a negative magnetic anisotropy (D) results in the observation of slow

  19. Organists and organ music composers.

    PubMed

    Foerch, Christian; Hennerici, Michael G

    2015-01-01

    Clinical case reports of patients with exceptional musical talent and education provide clues as to how the brain processes musical ability and aptitude. In this chapter, selected examples from famous and unknown organ players/composers are presented to demonstrate the complexity of modified musical performances as well as the capacities of the brain to preserve artistic abilities: both authors are active organists and academic neurologists with strong clinical experience, practice, and knowledge about the challenges to play such an outstanding instrument and share their interest to explore potentially instrument-related phenomena of brain modulation in specific transient or permanent impairments. We concentrate on the sites of lesions, suggested pathophysiology, separate positive (e.g., seizures, visual or auditory hallucinations, or synesthesia [an involuntary perception produced by stimulation of another sense]) and negative phenomena (e.g., amusia, aphasia, neglect, or sensory-motor deficits) and particularly address aspects of recent concepts of temporary and permanent network disorders. PMID:25684298

  20. Constraining the coordination geometries of lanthanide centers and magnetic building blocks in frameworks: a new strategy for molecular nanomagnets.

    PubMed

    Liu, Ke; Zhang, Xuejing; Meng, Xixi; Shi, Wei; Cheng, Peng; Powell, Annie K

    2016-05-01

    Single-molecule magnets (SMMs) and single-chain magnets (SCMs), also known as molecular nanomagnets, are molecular species of nanoscale proportions with the potential for high information storage density and spintronics applications. Metal-organic frameworks (MOFs) are three-dimensional ordered assemblies of inorganic nodes and organic linkers, featuring structural diversity and multiple chemical and physical properties. The concept of using these frameworks as scaffolds in the study of molecular nanomagnets provides an opportunity to constrain the local coordination geometries of lanthanide centers and organize the individual magnetic building blocks (MBBs, including both transition-metal and lanthanide MBBs) into topologically well-defined arrays that represent two key factors governing the magnetic properties of molecular nanomagnets. In this tutorial review, we summarize recent progress in this newly emerging field. PMID:27009851

  1. Synthesis and characterization of montmorillonite clay intercalated with molecular magnetic compounds

    NASA Astrophysics Data System (ADS)

    Martins, Marcel G.; Martins, Daniel O. T. A.; de Carvalho, Beatriz L. C.; Mercante, Luiza A.; Soriano, Stéphane; Andruh, Marius; Vieira, Méri D.; Vaz, Maria G. F.

    2015-08-01

    In this work montmorillonite (MMT) clay, whose matrix was modified with an ammonium salt (hexadecyltrimethylammonium bromide - CTAB), was employed as an inorganic host for the intercalation of three different molecular magnetic compounds through ion exchange: a nitronyl nitroxide derivative 2-[4-(N-ethyl)-pyridinium]-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (p-EtRad+) and two binuclear coordination compounds, [Ni(valpn)Ln]3+, where H2valpn stands for 1,3-propanediyl-bis(2-iminomethylene-6-methoxy-phenol), and Ln=GdIII; DyIII. The pristine MMT and the intercalated materials were characterized by X-ray powder diffraction (XRD), infrared spectroscopy (IR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and magnetic measurements. The X-ray diffraction data analysis showed an increase of the interlamellar space of the intercalated MMT, indicating the intercalation of the magnetic compounds. Furthermore, the magnetic properties of the hybrid compounds were investigated, showing similar behavior as the pure magnetic guest species.

  2. Magnetically triggered release of molecular cargo from iron oxide nanoparticle loaded microcapsules

    NASA Astrophysics Data System (ADS)

    Carregal-Romero, Susana; Guardia, Pablo; Yu, Xiang; Hartmann, Raimo; Pellegrino, Teresa; Parak, Wolfgang J.

    2014-12-01

    Photothermal release of cargo molecules has been extensively studied for bioapplications. For instance, microcapsules decorated with plasmonic nanoparticles have been widely used in in vitro assays. However, some concerns about their suitability for some in vivo applications cannot be easily overcome, in particular the limited penetration depth of light (even infrared). Magnetic nanoparticles are alternative heat-mediators for local heating, which can be triggered by applying an alternating magnetic field (AMF). AMFs are much less absorbed by tissue than light and thus can penetrate deeper overcoming the above mentioned limitations. Here we present iron oxide nanocube-modified microcapsules as a platform for magnetically triggered molecular release. Layer-by-layer assembled polyelectrolyte microcapsules with 4.6 μm diameter, which had 18 nm diameter iron oxide nanocubes integrated in their walls, were synthesized. The microcapsules were further loaded with an organic fluorescent polymer (Cascade Blue-labelled dextran), which was used as a model of molecular cargo. Through an AMF the magnetic nanoparticles were able to heat their surroundings and destroy the microcapsule walls, leading to a final release of the embedded cargo to the surrounding solution. The cargo release was monitored in solution by measuring the increase in both absorbance and fluorescence signal after the exposure to an AMF. Our results demonstrate that magnetothermal release of the encapsulated material is possible using magnetic nanoparticles with a high heating performance.Photothermal release of cargo molecules has been extensively studied for bioapplications. For instance, microcapsules decorated with plasmonic nanoparticles have been widely used in in vitro assays. However, some concerns about their suitability for some in vivo applications cannot be easily overcome, in particular the limited penetration depth of light (even infrared). Magnetic nanoparticles are alternative heat

  3. MULTI-SCALE ANALYSIS OF MAGNETIC FIELDS IN FILAMENTARY MOLECULAR CLOUDS IN ORION A

    SciTech Connect

    Poidevin, Frederick; Bastien, P.; Jones, T. J. E-mail: Bastien@astro.umontreal.ca

    2011-11-10

    New visible and K-band polarization measurements of stars surrounding molecular clouds in Orion A and stars in the Becklin-Neugebauer (BN) vicinity are presented. Our results confirm that magnetic fields located inside the Orion A molecular clouds and in their close neighborhood are spatially connected. On and around the BN object, we measured the angular offsets between the K-band polarization data and available submillimeter (submm) data. We find high values of the polarization degree, P{sub K} , and of the optical depth, {tau}{sub K}, close to an angular offset position of 90 Degree-Sign whereas lower values of P{sub K} and {tau}{sub K} are observed for smaller angular offsets. We interpret these results as evidence for the presence of various magnetic field components toward lines of sight in the vicinity of BN. On a larger scale, we measured the distribution of angular offsets between available H-band polarization data and the same submm data set. Here we find an increase of (P{sub H}) with angular offset, which we interpret as a rotation of the magnetic field by {approx}< 60 Degree-Sign . This trend generalizes previous results on small scales toward and around lines of sight to BN and is consistent with a twist of the magnetic field on a larger scale toward OMC-1. A comparison of our results with several other studies suggests that a two-component magnetic field, perhaps helical, could be wrapping the OMC-1 filament.

  4. High Magnetic Field Study on Giant Negative Magnetoresistance in the Molecular Conductor TPP[Cr(Pc)(CN)2]2

    NASA Astrophysics Data System (ADS)

    Ikeda, Mitsuo; Kida, Takanori; Tahara, Time; Murakawa, Hiroshi; Nishi, Miki; Matsuda, Masaki; Hagiwara, Masayuki; Inabe, Tamotsu; Hanasaki, Noriaki

    2016-06-01

    We investigated the magnetic and transport properties of the phthalocyanine molecular conductor TPP[Cr(Pc)(CN)2]2 in magnetic fields of up to 54 T. We observed giant negative magnetoresistance which hardly depends on the magnetic field direction owing to the isotropic nature confirmed by electron spin resonance measurements. The magnitude of magnetoresistance [|ρ(μ0H)/ρ(0 T) - 1|] is proportional to the square of magnetization as observed in the case of the spin scattering process, while the proportionality coefficient increases with decreasing the temperature. The magnetization does not saturate even at 53 T, indicating the existence of the large antiferromagnetic exchange interactions between the localized spins. In spite of this antiferromagnetic exchange interaction and low dimensionality, a convex magnetization curve was observed in the low temperature and high magnetic field range. To reproduce this magnetization curve, we proposed a model taking into account the antiferromagnetic exchange interaction between the neighboring π-electron spins.

  5. Molecular quantum magnetism with strong spin-orbit coupling in inorganic solid Ba3Yb2Zn5O11

    NASA Astrophysics Data System (ADS)

    Park, Sang-Youn; Ji, Sungdae; Park, Jae-Hoon; Do, Seunghwan; Choi, Kwang-Yong; Jang, Dongjin; Schmidt, Burkhard; Brando, Manuel; Butch, Nicholas

    The molecular magnet, assembly of finite number of spins which are isolated from environment, is a model system to study the quantum information process such as the qubit or spintronic devices. In past decades, the molecular magnet has been mostly realized in organic material, however, it has difficulty synthesizing materials or controlling their properties, meanwhile tremendous endeavors to search inorganic molecular magnet are continuing. Here, we propose Ba3Yb2Zn5O11 as a candidate of inorganic molecular magnet. This material consists of an alternating 3D-array of small and large tetrahedron containing antiferromagnetically coupled four pseudospin-1/2 Yb ions, and magnetic properties are described by an isolated tetrahedron without long-range magnetic ordering. Inelastic neutron scattering measurement with external magnetic field reveals that extraordinarily huge Dzyaloshinsky-Moriya (DM) interaction originating from strong spin-orbit coupling in Yb isospin is the key to explain energy level of tetrahedron in addition to Heisenberg exchange interaction and Zeeman effect. Magnetization measurement shows the Landau-Zener transition between avoided crossing levels caused by DM interaction.

  6. Spectroscopic Studies of Atomic and Molecular Processes in the Edge Region of Magnetically Confined Fusion Plasmas

    SciTech Connect

    Hey, J. D.; Brezinsek, S.; Mertens, Ph.; Unterberg, B.

    2006-12-01

    Edge plasma studies are of vital importance for understanding plasma-wall interactions in magnetically confined fusion devices. These interactions determine the transport of neutrals into the plasma, and the properties of the plasma discharge. This presentation deals with optical spectroscopic studies of the plasma boundary, and their role in elucidating the prevailing physical conditions. Recorded spectra are of four types: emission spectra of ions and atoms, produced by electron impact excitation and by charge-exchange recombination, atomic spectra arising from electron impact-induced molecular dissociation and ionisation, visible spectra of molecular hydrogen and its isotopic combinations, and laser-induced fluorescence (LIF) spectra. The atomic spectra are strongly influenced by the confining magnetic field (Zeeman and Paschen-Back effects), which produces characteristic features useful for species identification, temperature determination by Doppler broadening, and studies of chemical and physical sputtering. Detailed analysis of the Zeeman components in both optical and LIF spectra shows that atomic hydrogen is produced in various velocity classes, some related to the relevant molecular Franck-Condon energies. The latter reflect the dominant electron collision processes responsible for production of atoms from molecules. This assignment has been verified by gas-puffing experiments through special test limiters. The higher-energy flanks of hydrogen line profiles probably also show the influence of charge-exchange reactions with molecular ions accelerated in the plasma sheath ('scrape-off layer') separating limiter surfaces from the edge plasma, in analogy to acceleration in the cathode-fall region of gas discharges. While electron collisions play a vital role in generating the spectra, ion collisions with excited atomic radiators act through re-distribution of population among the atomic fine-structure sublevels, and momentum transfer to the atomic nuclei via

  7. Preparation of Magnetic Hollow Molecularly Imprinted Polymers for Detection of Triazines in Food Samples.

    PubMed

    Wang, Aixiang; Lu, Hongzhi; Xu, Shoufang

    2016-06-22

    Novel magnetic hollow molecularly imprinted polymers (M-H-MIPs) were proposed for highly selective recognition and fast enrichment of triazines in food samples. M-H-MIPs were prepared on the basis of multi-step swelling polymerization, followed by in situ growth of magnetic Fe3O4 nanoparticles on the surface of hollow molecularly imprinted polymers (H-MIPs). Transmission electron microscopy and scanning electron microscopy confirmed the successful immobilization of Fe3O4 nanoparticles on the surface of H-MIPs. M-H-MIPs could be separated simply using an external magnet. The binding adsorption results indicated that M-H-MIPs displayed high binding capacity and fast mass transfer property and class selective property for triazines. Langmuir isotherm and pseudo-second-order kinetic models fitted the best adsorption models for M-H-MIPs. M-H-MIPs were used to analyze atrazine, simazine, propazine, and terbuthylazine in corn, wheat, and soybean samples. Satisfactory recoveries were in the range of 80.62-101.69%, and relative standard deviation was lower than 5.2%. Limits of detection from 0.16 to 0.39 μg L(-1) were obtained. When the method was applied to test positive samples that were contaminated with triazines, the results agree well with those obtained from an accredited method. Thus, the M-H-MIP-based dispersive solid-phase extraction method proved to be a convenient and practical platform for detection of triazines in food samples. PMID:27257079

  8. Molecular quantum spintronics: supramolecular spin valves based on single-molecule magnets and carbon nanotubes.

    PubMed

    Urdampilleta, Matias; Nguyen, Ngoc-Viet; Cleuziou, Jean-Pierre; Klyatskaya, Svetlana; Ruben, Mario; Wernsdorfer, Wolfgang

    2011-01-01

    We built new hybrid devices consisting of chemical vapor deposition (CVD) grown carbon nanotube (CNT) transistors, decorated with TbPc(2) (Pc = phthalocyanine) rare-earth based single-molecule magnets (SMMs). The drafting was achieved by tailoring supramolecular π-π interactions between CNTs and SMMs. The magnetoresistance hysteresis loop measurements revealed steep steps, which we can relate to the magnetization reversal of individual SMMs. Indeed, we established that the electronic transport properties of these devices depend strongly on the relative magnetization orientations of the grafted SMMs. The SMMs are playing the role of localized spin polarizer and analyzer on the CNT electronic conducting channel. As a result, we measured magneto-resistance ratios up to several hundred percent. We used this spin valve effect to confirm the strong uniaxial anisotropy and the superparamagnetic blocking temperature (T(B) ~ 1 K) of isolated TbPc(2) SMMs. For the first time, the strength of exchange interaction between the different SMMs of the molecular spin valve geometry could be determined. Our results introduce a new design for operable molecular spintronic devices using the quantum effects of individual SMMs. PMID:22072910

  9. Intermolecular shielding from molecular magnetic susceptibility. A new view of intermolecular ring current effects.

    PubMed

    Facelli, Julio C

    2006-03-01

    This paper presents calculations of the NICS (nuclear independent chemical shieldings) in a rectangular grid surrounding the molecules of benzene, naphthalene and coronene. Using the relationship between calculated NICS and the induced magnetic field, the calculated NICS are used to predict intermolecular effects due to molecular magnetic susceptibility or ring current effects. As expected from approximate ring current models, these intermolecular shielding effects are concentrated along the direction perpendicular to the molecular plane and they approach asymptotically to a dipolar functional dependence, i.e. (1-3 cos(2)theta)/r(3)). The deviations from the dipolar functional form require that the calculations of these intermolecular effects be done using a suitable interpolation scheme of the NICS calculated on the grid. The analysis of the NICS tensor components shows that these intermolecular shielding effects should be primarily expected on shielding components of the neighboring molecules nuclei, which are perpendicular to the molecular plane of the aromatic compound generating the induced field. The analysis of the calculated NICS along the series benzene, naphthalene and coronene shows that these intermolecular effects increase monotonically with the number of aromatic rings. PMID:16477673

  10. Magnetically Regulated Star Formation in Three Dimensions: The Case of the Taurus Molecular Cloud Complex

    NASA Astrophysics Data System (ADS)

    Nakamura, Fumitaka; Li, Zhi-Yun

    2008-11-01

    We carry out three-dimensional MHD simulations of star formation in turbulent, magnetized clouds, including ambipolar diffusion and feedback from protostellar outflows. The calculations focus on relatively diffuse clouds threaded by a strong magnetic field capable of resisting severe tangling by turbulent motions and retarding global gravitational contraction in the cross field direction. They are motivated by observations of the Taurus molecular cloud complex (and, to a lesser extent, Pipe Nebula), which shows an ordered large-scale magnetic field, as well as elongated condensations that are generally perpendicular to the large-scale field. We find that stars form in earnest in such clouds when enough material has settled gravitationally along the field lines that the mass-to-flux ratios of the condensations approach the critical value. Only a small fraction (of order 1% or less) of the nearly magnetically critical, condensed material is turned into stars per local free-fall time, however. The slow star formation takes place in condensations that are moderately supersonic; it is regulated primarily by magnetic fields, rather than turbulence. The quiescent condensations are surrounded by diffuse halos that are much more turbulent, as observed in the Taurus complex. Strong support for magnetic regulation of star formation in this complex comes from the extremely slow conversion of the already condensed, relatively quiescent C18O gas into stars, at a rate 2 orders of magnitude below the maximum, free-fall value. We analyze the properties of dense cores, including their mass spectrum, which resembles the stellar initial mass function.

  11. Carboxylate-based molecular magnet: One path toward achieving stable quantum correlations at room temperature

    NASA Astrophysics Data System (ADS)

    Cruz, C.; Soares-Pinto, D. O.; Brandão, P.; dos Santos, A. M.; Reis, M. S.

    2016-02-01

    The control of quantum correlations in solid-state systems by means of material engineering is a broad avenue to be explored, since it makes possible steps toward the limits of quantum mechanics and the design of novel materials with applications on emerging quantum technologies. In this context, this letter explores the potential of molecular magnets to be prototypes of materials for quantum information technology. More precisely, we engineered a material and from its geometric quantum discord we found significant quantum correlations up to 9540 K (even without entanglement); and, in addition, a pure singlet state occupied up to around 80 K (above liquid nitrogen temperature). These results could only be achieved due to the carboxylate group promoting a metal-to-metal huge magnetic interaction.

  12. Characterising the Importance of Magnetic Fields in Star Formation in the Vela Molecular Ridge

    NASA Astrophysics Data System (ADS)

    Fissel, Laura; Lo, Nadia; Jones, Paul; Cunningham, Maria; Fukui, Yasuo; Ward-Thompson, Derek; Minier, Vincent; Olmi, Luca; Schneider, Nicola; Lowe, Vicki; Goodman, Alyssa; Devlin, Mark; Netterfield, Calvin Barth; Novak, Giles; Pascale, Enzo; Podevin, Frederick

    2012-04-01

    In this proposal we are requesting time to map the Vela C complex with the Mopra telescope in 12CO, 13CO and C18O. Our data will be combined with polarised dust emission maps from the BLAST-Pol balloon-borne polarimeter (which maps the cloud magnetic field morphology), observations from an ongoing Mopra survey (M401, PI Vicki Lowe) to map Vela C in dense gas and other kinematic tracers along with data on the protostellar content and filamentary structure of the cloud from Herschel HOBYS. Combining these datasets will allow us to characterise the importance of magnetic fields, turbulence and external triggering in regulating star formation in this nearby massive molecular cloud complex.

  13. Paramagnetic molecule induced strong antiferromagnetic exchange coupling on a magnetic tunnel junction based molecular spintronics device

    NASA Astrophysics Data System (ADS)

    Tyagi, Pawan; Baker, Collin; D'Angelo, Christopher

    2015-07-01

    This paper reports our Monte Carlo (MC) studies aiming to explain the experimentally observed paramagnetic molecule induced antiferromagnetic coupling between ferromagnetic (FM) electrodes. Recently developed magnetic tunnel junction based molecular spintronics devices (MTJMSDs) were prepared by chemically bonding the paramagnetic molecules between the FM electrodes along the tunnel junction’s perimeter. These MTJMSDs exhibited molecule-induced strong antiferromagnetic coupling. We simulated the 3D atomic model analogous to the MTJMSD and studied the effect of molecule’s magnetic couplings with the two FM electrodes. Simulations show that when a molecule established ferromagnetic coupling with one electrode and antiferromagnetic coupling with the other electrode, then theoretical results effectively explained the experimental findings. Our studies suggest that in order to align MTJMSDs’ electrodes antiparallel to each other, the exchange coupling strength between a molecule and FM electrodes should be ˜50% of the interatomic exchange coupling for the FM electrodes.

  14. Paramagnetic molecule induced strong antiferromagnetic exchange coupling on a magnetic tunnel junction based molecular spintronics device.

    PubMed

    Tyagi, Pawan; Baker, Collin; D'Angelo, Christopher

    2015-07-31

    This paper reports our Monte Carlo (MC) studies aiming to explain the experimentally observed paramagnetic molecule induced antiferromagnetic coupling between ferromagnetic (FM) electrodes. Recently developed magnetic tunnel junction based molecular spintronics devices (MTJMSDs) were prepared by chemically bonding the paramagnetic molecules between the FM electrodes along the tunnel junction's perimeter. These MTJMSDs exhibited molecule-induced strong antiferromagnetic coupling. We simulated the 3D atomic model analogous to the MTJMSD and studied the effect of molecule's magnetic couplings with the two FM electrodes. Simulations show that when a molecule established ferromagnetic coupling with one electrode and antiferromagnetic coupling with the other electrode, then theoretical results effectively explained the experimental findings. Our studies suggest that in order to align MTJMSDs' electrodes antiparallel to each other, the exchange coupling strength between a molecule and FM electrodes should be ∼50% of the interatomic exchange coupling for the FM electrodes. PMID:26159362

  15. Combined Molecular Dynamics-Spin Dynamics Simulation of α-Iron in an External Magnetic Field

    NASA Astrophysics Data System (ADS)

    Mudrick, Mark; Perera, Dilina; Landau, David P.

    Using an atomistic model that treats both translational and spin degrees of freedom, combined molecular and spin dynamics simulations have been performed to study dynamic properties of α-iron. Atomic interactions are described by an empirical many-body potential while spin-spin interactions are handled with a Heisenberg-like Hamiltonian with a coordinate dependent exchange interaction. Each of these interactions are parameterized by first-principles calculations. These simulations numerically solve equations of motion using an algorithm based on the second-order Suzuki-Trotter decomposition for the time evolution operator. Through calculation of the Fourier transform of space-displaced time-displaced correlation functions, vibrational and magnetic excitations have been studied. The application of an external magnetic field up to 10-T has now been included and has been shown to increase the characteristic frequencies of the single-spin-wave excitations. Two-spin-wave interactions have also been investigated.

  16. Kondo peak splitting and Kondo dip in single molecular magnet junctions

    NASA Astrophysics Data System (ADS)

    Niu, Pengbin; Shi, Yunlong; Sun, Zhu; Nie, Yi-Hang; Luo, Hong-Gang

    2016-01-01

    Many factors containing bias, spin-orbit coupling, magnetic fields applied, and so on can strongly influence the Kondo effect, and one of the consequences is Kondo peak splitting (KPS). It is natural that KPS should also appear when another spin degree of freedom is involved. In this work we study the KPS effects of single molecular magnets (SMM) coupled with two metallic leads in low-temperature regime. It is found that the Kondo transport properties are strongly influenced by the exchange coupling and anisotropy of the magnetic core. By employing Green's function method in Hubbard operator representation, we give an analytical expression for local retarded Green's function of SMM and discussed its low-temperature transport properties. We find that the anisotropy term behaves as a magnetic field and the splitting behavior of exchange coupling is quite similar to the spin-orbit coupling. These splitting behaviors are explained by introducing inter-level or intra-level transitions, which account for the seven-peak splitting structure. Moreover, we find a Kondo dip at Fermi level under proper parameters. These Kondo peak splitting behaviors in SMM deepen our understanding to Kondo physics and should be observed in the future experiments.

  17. Broad-band polarization in molecular spectra. [Zeeman effect in magnetic stars

    NASA Technical Reports Server (NTRS)

    Illing, R. M. E.

    1981-01-01

    The rotational lines of the CN(0,0) red system have been observed to show a strongly asymmetric Zeeman profile. Certain molecules are very susceptible to magnetic perturbation because of the weakness of their spin-rotation coupling; a fairly weak magnetic field can cause a complete Paschen-Back effect. The calculation of transition probabilities incorporating this effect into the Hamiltonian is discussed, and the detailed calculation is then given. The resulting transition probabilities are transformed into synthetic line profiles by using the Unno (1956) model of polarized radiation transfer. The dependence of the net polarized flux on magnetic field and equivalent width is investigated. It is shown that entire band systems may be significantly polarized. Broad-band circular polarization of sunspots may be due, in part, to molecular bands. Analysis of the CH G band indicates a magnetic field of 0.25-0.50 x 10 to the 6th gauss in the white dwarf G99-37, an order of magnitude lower than previous estimates.

  18. Molecularly imprinted ionic liquid magnetic microspheres for the rapid isolation of organochlorine pesticides in environmental water.

    PubMed

    Qiao, Fengxia; Gao, Mengmeng; Yan, Hongyuan

    2016-04-01

    A new type of molecularly imprinted ionic liquid magnetic microspheres was synthesized by aqueous suspension polymerization, using 4,4'-dichlorobenzhydrol as a dummy template, and 1-allyl-3-ethylimidazolium hexafluorophosphate and methacrylic acid as co-functional monomers. The results of morphology and magnetic property evaluation of the obtained microspheres demonstrated that it was monodispersed spherical, possessed a rough surface, and an outstanding magnetic properties. Binding experiments revealed that it had a substantial adsorption capacity and strong recognition ability to organochlorine pesticides (OCPs) in aqueous solution. Then the microspheres were applied as an adsorbent of magnetic dispersive solid-phase extraction for the selective recognition and rapid determination of OCPs in environmental water. Under the optimum conditions, good linearity of the three types of OCPs (dicofol, tetradifon, and p,p'-dichlorodiphenyldichloroethane) was achieved in the range of 1.0-100 ng/mL (r ≥ 0.9994). The recoveries at three spiking levels ranged from 82.6 to 100.4% with the RSDs less than 6.9%. PMID:26791136

  19. The ab initio calculation of molecular electric, magnetic and geometric properties.

    PubMed

    Bast, Radovan; Ekström, Ulf; Gao, Bin; Helgaker, Trygve; Ruud, Kenneth; Thorvaldsen, Andreas J

    2011-02-21

    We give an account of some recent advances in the development of ab initio methods for the calculation of molecular response properties, involving electric, magnetic, and geometric perturbations. Particular attention is given to properties in which the basis functions depend explicitly both on time and on the applied perturbations such as perturbations involving nuclear displacements or external magnetic fields when London atomic orbitals are used. We summarize a general framework based on the quasienergy for the calculation of arbitrary-order molecular properties using the elements of the density matrix in the atomic-orbital basis as the basic variables. We demonstrate that the necessary perturbed density matrices of arbitrary order can be determined from a set of linear equations that have the same formal structure as the set of linear equations encountered when determining the linear response equations (or time-dependent self-consistent-field equations). Additional components needed to calculate properties involving perturbation-dependent basis sets are flexible one- and two-electron integral techniques for geometric or magnetic-field differentiated integrals; in Kohn-Sham density-functional theory (KS-DFT), we also need to calculate derivatives of the exchange-correlation functional. We describe a recent proposal for evaluating these contributions based on automatic differentiation. Within this framework, it is now possible to calculate any molecular property for an arbitrary self-consistent-field reference state, including two- and four-component relativistic self-consistent-field wave functions. Examples of calculations that can be performed with this formulation are presented. PMID:21180690

  20. Molecular Structure Laboratory. Fourier Transform Nuclear Magnetic Resonance (FTNMR) Spectrometer and Ancillary Instrumentation at SUNY Geneseo

    SciTech Connect

    Geiger, David K

    2015-12-31

    An Agilent 400-MR nuclear magnetic resonance (NMR) spectrometer and ancillary equipment were purchased, which are being used for molecular structure elucidation.  The instrumentation is housed in a pre-existing facility designed specifically for its use. This instrument package is being used to expand the research and educational efforts of the faculty and students at SUNY-Geneseo and is made available to neighboring educational institutions and business concerns.  Funds were also used for training of College personnel, maintenance of the instrumentation, and installation of the equipment.

  1. Molecular Structure of Aggregated Amyloid-β: Insights from Solid-State Nuclear Magnetic Resonance.

    PubMed

    Tycko, Robert

    2016-01-01

    Amyloid-β (Aβ) peptides aggregate to form polymorphic amyloid fibrils and a variety of intermediate assemblies, including oligomers and protofibrils, both in vitro and in human brain tissue. Since the beginning of the 21st century, considerable progress has been made to characterize the molecular structures of Aβ aggregates. Full molecular structural models based primarily on data from measurements using solid-state nuclear magnetic resonance (ssNMR) have been developed for several in vitro Aβ fibrils and one metastable protofibril. Partial structural characterization of other aggregation intermediates has been achieved. One full structural model for fibrils derived from brain tissue has also been reported. Future work is likely to focus on additional structures from brain tissue and on further clarification of nonfibrillar Aβ aggregates. PMID:27481836

  2. Cyclo-biphenalenyl biradicaloid molecular materials: conformation, rearrangement, magnetism, and thermochromism

    SciTech Connect

    Huang, Jingsong; Sumpter, Bobby G; Meunier, Vincent; Tian, Yong-Hui; Kertesz, Prof. Miklos

    2010-01-01

    Cyclo-biphenalenyl biradicaloid molecular materials with chair- and boat-conformations are studied by restricted and broken-symmetry DFT using the M06 family of meta-GGA functionals. The global minima of these molecular materials are magnetically silent due to the sigma-bond connecting the two phenalenyls, while the sigma-bond may undergo low-barrier sigmatropic rearrangements via pi-pi bonded paramagnetic intermediates. The validation of theory is performed for the chair-conformation by comparing the sigma-bonded structures and the rearrangement barriers with experimental data. The boat-conformation is then studied using the validated functional. The electronic spectra of both chair- and boat-conformations are calculated and their applications in thermochromism are discussed.

  3. Determination of ractopamine in pork using a magnetic molecularly imprinted polymer as adsorbent followed by HPLC.

    PubMed

    Tang, Yiwei; Gao, Jingwen; Liu, Xiuying; Lan, Jianxing; Gao, Xue; Ma, Yong; Li, Min; Li, Jianrong

    2016-06-15

    A new magnetic molecularly imprinted polymers (MMIPs) for separation and concentration of ractopamine (RAC) were prepared using surface molecular imprinting technique with methacryloyl chloride as functional monomer and RAC as template. The MMIPs were characterized using transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and vibrating sample magnetometer. The results of re-binding experiments indicated that the MMIPs had fast adsorption kinetics and could reach binding equilibrium within 20 min, and the adsorption capacity of the MMIPs was 2.87-fold higher than that of the corresponding non-imprinted polymer. The selectivity of the MMIPs was evaluated according to its recognition to RAC and its analogues. The synthesized MMIPs were successfully applied to extraction, followed by high performance liquid chromatography to determine RAC in real food samples. Spiked recoveries ranged from 73.60% to 94.5%, with relative standard deviations of <11.17%. PMID:26868550

  4. Computational simulation and preparation of fluorescent magnetic molecularly imprinted silica nanospheres for ciprofloxacin or norfloxacin sensing.

    PubMed

    Gao, Bo; He, Xin-Ping; Jiang, Yang; Wei, Jia-Tong; Suo, Hui; Zhao, Chun

    2014-12-01

    A magnetic molecularly imprinted fluorescent sensor for the sensitive and convenient determination of ciprofloxacin or norfloxacin in human urine was synthesized and characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, ultraviolet/visible spectroscopy, and fluorescence spectroscopy. Both cadmium telluride quantum dots and ferroferric oxide nanoparticles are introduced into the polymer for the rapid separation and detection of the target molecules. The synthesized molecularly imprinted polymers were applied to detect ciprofloxacin or its structural analog norfloxacin in human urine with the detection limit 130 ng/mL. A computational study was developed to evaluate the template-monomer geometry and interaction energy in the polymerization mixture to determine the reaction molar ratio of the template and monomer molecules. PMID:25311209

  5. Improving the Description of Nonmagnetic and Magnetic Molecular Crystals via the van der Waals Density Functional

    NASA Astrophysics Data System (ADS)

    Obata, Masao; Nakamura, Makoto; Hamada, Ikutaro; Oda, Tatsuki

    2015-02-01

    We have derived and implemented a stress tensor formulation for the van der Waals density functional (vdW-DF) with spin-polarization-dependent gradient correction (GC) recently proposed by the authors [J. Phys. Soc. Jpn. 82, 093701 (2013)] and applied it to nonmagnetic and magnetic molecular crystals under ambient condition. We found that the cell parameters of the molecular crystals obtained with vdW-DF show an overall improvement compared with those obtained using local density and generalized gradient approximations. In particular, the original vdW-DF with GC gives the equilibrium structural parameters of solid oxygen in the α-phase, which are in good agreement with the experiment.

  6. Confinement of the hydrogen molecular ion H2+ under a magnetic field inside a spheroid

    NASA Astrophysics Data System (ADS)

    Molinar, Martin

    2010-03-01

    A study of the confinement of the hydrogen molecular ion H2+ is done. The molecular ion is subject to the action of a magnetic field. In the Born -- Oppenheimer approximation, we solve numerically the Schr"odinger's equation, using trial functions and one algorithm that allows us to calculate the energies for different given values of the confinement parameters. We use the variational method in order to estimate the energy of the ground state. Some properties of the system as the pressure exerted by the confinement, the polarizability in the approximations of Kirkwood and Buckingham and the energies of the vibrational states are calculated. The behavior of the internuclear separation is analyzed for the geometry considered.

  7. Magnetic capture from blood rescues molecular motor function in diagnostic nanodevices

    PubMed Central

    2013-01-01

    Background Introduction of effective point-of-care devices for use in medical diagnostics is part of strategies to combat accelerating health-care costs. Molecular motor driven nanodevices have unique potentials in this regard due to unprecedented level of miniaturization and independence of external pumps. However motor function has been found to be inhibited by body fluids. Results We report here that a unique procedure, combining separation steps that rely on antibody-antigen interactions, magnetic forces applied to magnetic nanoparticles (MPs) and the specificity of the actomyosin bond, can circumvent the deleterious effects of body fluids (e.g. blood serum). The procedure encompasses the following steps: (i) capture of analyte molecules from serum by MP-antibody conjugates, (ii) pelleting of MP-antibody-analyte complexes, using a magnetic field, followed by exchange of serum for optimized biological buffer, (iii) mixing of MP-antibody-analyte complexes with actin filaments conjugated with same polyclonal antibodies as the magnetic nanoparticles. This causes complex formation: MP-antibody-analyte-antibody-actin, and magnetic separation is used to enrich the complexes. Finally (iv) the complexes are introduced into a nanodevice for specific binding via actin filaments to surface adsorbed molecular motors (heavy meromyosin). The number of actin filaments bound to the motors in the latter step was significantly increased above the control value if protein analyte (50–60 nM) was present in serum (in step i) suggesting appreciable formation and enrichment of the MP-antibody-analyte-antibody-actin complexes. Furthermore, addition of ATP demonstrated maintained heavy meromyosin driven propulsion of actin filaments showing that the serum induced inhibition was alleviated. Detailed analysis of the procedure i-iv, using fluorescence microscopy and spectroscopy identified main targets for future optimization. Conclusion The results demonstrate a promising approach for

  8. Magnetized interstellar molecular clouds - I. Comparison between simulations and Zeeman observations

    NASA Astrophysics Data System (ADS)

    Li, Pak Shing; McKee, Christopher F.; Klein, Richard I.

    2015-09-01

    The most accurate measurements of magnetic fields in star-forming gas are based on the Zeeman observations analysed by Crutcher et al. We show that their finding that the 3D magnetic field scales approximately as density0.65 can also be obtained from analysis of the observed line-of-sight fields. We present two large-scale adaptive-mesh-refinement magnetohydrodynamic simulations of several thousand M⊙ of turbulent, isothermal, self-gravitating gas, one with a strong initial magnetic field (Alfvén Mach number M_A,0=1) and one with a weak initial field (M_A,0=10). We construct samples of the 100 most massive clumps in each simulation and show that they exhibit a power-law relation between field strength and density (bar{n}_H) in excellent agreement with the observed one. Our results imply that the average field in molecular clumps in the interstellar medium (ISM) is < B_tot(bar{n}_H) > ≈ 42 bar{n}_{H, 4}^{0.65} μ G. Furthermore, the median value of the ratio of the line-of-sight field to density0.65 in the simulations is within a factor of about (1.3, 1.7) of the observed value for the strong- and weak-field cases, respectively. The median value of the mass-to-flux ratio, normalized to the critical value, is 70 per cent of the line-of-sight value. This is larger than the 50 per cent usually cited for spherical clouds because the actual mass-to-flux ratio depends on the volume-weighted field, whereas the observed one depends on the mass-weighted field. Our results indicate that the typical molecular clump in the ISM is significantly supercritical (˜ factor of 3). The results of our strong-field model are in very good quantitative agreement with the observations of Li et al., which show a strong correlation in field orientation between small and large scales. Because there is a negligible correlation in the weak-field model, we conclude that molecular clouds form from strongly magnetized (although magnetically supercritical) gas, in agreement with the conclusion

  9. Bioengineered Probes for Molecular Magnetic Resonance Imaging in the Nervous System

    PubMed Central

    2012-01-01

    The development of molecular imaging probes has changed the nature of neurobiological research. Some of the most notable successes have involved the use of biological engineering techniques for the creation of fluorescent protein derivatives for optical imaging, but recent work has also led to a number of bioengineered probes for magnetic resonance imaging (MRI), the preeminent technique for noninvasive investigation of brain structure and function. Molecular MRI agents are beginning to be applied for experiments in the nervous system, where they have the potential to bridge from molecular to systems or organismic levels of analysis. Compared with canonical synthetic small molecule agents, biomolecular or semibiosynthetic MRI contrast agents offer special advantages due to their amenability to molecular engineering approaches, their properties in some cases as catalysts, and their specificity in targeting and ligand binding. Here, we discuss an expanding list of instances where biological engineering techniques have aided in the design of MRI contrast agents and reporter systems, examining both advantages and limitations of these types of probes for studies in the central nervous system. PMID:22896803

  10. Investigations on nanoconfinement of low-molecular antineoplastic agents into biocompatible magnetic matrices for drug targeting.

    PubMed

    Tomoiaga, Alina Maria; Cioroiu, Bogdan Ionel; Nica, Valentin; Vasile, Aurelia

    2013-11-01

    Magnetic mesoporous silica nanoparticles are employed as biocompatible matrices to host low-molecular antineoplastic drugs. 5-Fluorouracil is a well-known antimetabolite drug used to treat many malignancies: colon, rectal, breast, head and neck, pancreatic, gastric, esophageal, liver and G-U (bladder, penile, vulva, prostate), skin cancers (basal cell and keratosis). Unfortunately severe gastrointestinal, hematological, neural, cardiac and dermatological toxic effects are often registered due to its cytotoxicity. Thus, this work focuses on development of a magnetic silica nanosystem, capable of hosting high amounts of 5-fluorouracil and delivers it in a targeted manner, under the influence of external magnetic field. There are few reports on nanoconfinement of this particular small molecule antimetabolite on mesoporous silica hosts. Therefore we have investigated different ways to confine high amounts of 5-FU within amino-modified and non-modified mesopores of the silica shell, from water and ethanol, under magnetic stirring and ultrasound irradiation. Also, we have studied the adsorption process from water as a function of pH in order to rationalize drug-support interactions. It is shown that nature of the solvent has great influence on diffusion of small molecules into mesopores, which is slower from alcoholic solutions. More importantly, sonication is proven as an excellent alternative to long adsorption tests, since the time necessary to reach equilibrium is drastically reduced to 1h and higher amounts of drug may be immobilized within the mesopores of amino-modified magnetic silica nanoparticles. These results are highly important for optimization of drug immobilization process in order to attain desired release profile. PMID:23777792

  11. Enhancing the magnetic anisotropy of maghemite nanoparticles via the surface coordination of molecular complexes

    PubMed Central

    Prado, Yoann; Daffé, Niéli; Michel, Aude; Georgelin, Thomas; Yaacoub, Nader; Grenèche, Jean-Marc; Choueikani, Fadi; Otero, Edwige; Ohresser, Philippe; Arrio, Marie-Anne; Cartier-dit-Moulin, Christophe; Sainctavit, Philippe; Fleury, Benoit; Dupuis, Vincent; Lisnard, Laurent; Fresnais, Jérôme

    2015-01-01

    Superparamagnetic nanoparticles are promising objects for data storage or medical applications. In the smallest—and more attractive—systems, the properties are governed by the magnetic anisotropy. Here we report a molecule-based synthetic strategy to enhance this anisotropy in sub-10-nm nanoparticles. It consists of the fabrication of composite materials where anisotropic molecular complexes are coordinated to the surface of the nanoparticles. Reacting 5 nm γ-Fe2O3 nanoparticles with the [CoII(TPMA)Cl2] complex (TPMA: tris(2-pyridylmethyl)amine) leads to the desired composite materials and the characterization of the functionalized nanoparticles evidences the successful coordination—without nanoparticle aggregation and without complex dissociation—of the molecular complexes to the nanoparticles surface. Magnetic measurements indicate the significant enhancement of the anisotropy in the final objects. Indeed, the functionalized nanoparticles show a threefold increase of the blocking temperature and a coercive field increased by one order of magnitude. PMID:26634987

  12. Enhancing the magnetic anisotropy of maghemite nanoparticles via the surface coordination of molecular complexes.

    PubMed

    Prado, Yoann; Daffé, Niéli; Michel, Aude; Georgelin, Thomas; Yaacoub, Nader; Grenèche, Jean-Marc; Choueikani, Fadi; Otero, Edwige; Ohresser, Philippe; Arrio, Marie-Anne; Cartier-dit-Moulin, Christophe; Sainctavit, Philippe; Fleury, Benoit; Dupuis, Vincent; Lisnard, Laurent; Fresnais, Jérôme

    2015-01-01

    Superparamagnetic nanoparticles are promising objects for data storage or medical applications. In the smallest--and more attractive--systems, the properties are governed by the magnetic anisotropy. Here we report a molecule-based synthetic strategy to enhance this anisotropy in sub-10-nm nanoparticles. It consists of the fabrication of composite materials where anisotropic molecular complexes are coordinated to the surface of the nanoparticles. Reacting 5 nm γ-Fe2O3 nanoparticles with the [Co(II)(TPMA)Cl2] complex (TPMA: tris(2-pyridylmethyl)amine) leads to the desired composite materials and the characterization of the functionalized nanoparticles evidences the successful coordination--without nanoparticle aggregation and without complex dissociation--of the molecular complexes to the nanoparticles surface. Magnetic measurements indicate the significant enhancement of the anisotropy in the final objects. Indeed, the functionalized nanoparticles show a threefold increase of the blocking temperature and a coercive field increased by one order of magnitude. PMID:26634987

  13. Preparation of magnetic molecularly imprinted polymer for selective recognition of resveratrol in wine.

    PubMed

    Chen, Fang-Fang; Xie, Xiao-Yu; Shi, Yan-Ping

    2013-07-26

    The magnetic molecularly imprinted polymers (MMIPs) for resveratrol were prepared by using surface molecular imprinting technique with a super paramagnetic core-shell nanoparticle as a supporter. Rhapontigenin, which is the analogues of resveratrol, was selected as dummy template molecules to avoid the leakage of trace amount of resveratrol. Acrylamide and ethylene glycol dimethacrylate were chosen as functional monomers and cross-linker, respectively. The obtained MMIPs were characterized by using scanning electron microscopy, Fourier transform infrared spectrum, X-ray diffraction and vibrating sample magnetometer. High performance liquid chromatography was used to analyze the target analytes. The resulting MMIPs exhibited high saturation magnetization of 53.14emug(-1) leading to the fast separation. The adsorption test showed that the MMIPs had high adsorption capacity for resveratrol and contained homogeneous binding sites. The MMIPs were employed as adsorbent of solid phase extraction for determination of resveratrol in real wine samples, and the recoveries of spiked samples ranged from 79.3% to 90.6% with the limit of detection of 4.42ngmL(-1). The prepared MMIPs could be employed to selectively pre-concentrate and determine resveratrol from wine samples. PMID:23481473

  14. A norepinephrine coated magnetic molecularly imprinted polymer for simultaneous multiple chiral recognition.

    PubMed

    Chen, Juan; Liang, Ru-Ping; Wang, Xiao-Ni; Qiu, Jian-Ding

    2015-08-28

    A newly designed molecularly imprinted polymer (MIP) material was developed and successfully used as recognition element for enantioselective recognition by microchip electrophoresis. In this work, molecularly imprinted polymers were facilely prepared employing Fe3O4 nanoparticles (NPs) as the supporting substrate and norepinephrine as the functional monomer in the presence of template molecule in a weak alkaline solution. After extracting the embedded template molecules, the produced imprinted Fe3O4@polynorepinephrine (MIP-Fe3O4@PNE) NPs have cavities complementary to three dimensional shape of template molecules favoring high binding capacity and magnetism property for easy manipulation. The MIP-Fe3O4@PNE NPs prepared with l-tryptophan, l-valine, l-threonine, Gly-l-Phe, S-(-)-ofloxacin or S-(-)-binaphthol as template molecules were packed in the polydimethylsiloxane microchannel via magnetic field as novel stationary phase to successful enantioseparation of corresponding target analysts. The MIP-Fe3O4@PNE NPs-based microchip electrophoresis system exhibited strong recognition ability, excellent high-performance, admirable reproducibility and stability, which provided a powerful protocol for separation enantiomers within a short analytical time and opened up an avenue for multiplex chiral compound assay in various systems. PMID:26206627

  15. Detailed Magnetic Field Morphology of the Vela C Molecular Cloud from the BLASTPol 2012 flight

    NASA Astrophysics Data System (ADS)

    Fissel, Laura Marion; Ade, Peter; Angilè, Francesco E.; Ashton, Peter; Benton, Steven J.; Devlin, Mark J.; Dober, Bradley; Fukui, Yasuo; Galitzki, Nicholas B.; Gandilo, Natalie; Klein, Jeff; Korotkov, Andrei; Li, Zhi-Yun; Moncelsi, Lorenzo; Matthews, Tristan; nakamura, fumitaka; Barth Netterfield, Calvin; Novak, Giles; Pascale, Enzo; Poidevin, Frédérick; Savini, Giorgio; Pereira Santos, Fábio; Scott, Douglas; Shariff, Jamil; Soler, Juan Diego; Thomas, Nicholas; tucker, carole; Tucker, Gregory S.; Ward-Thompson, Derek

    2015-01-01

    In order to understand the role of magnetic fields in the process of star formation, we require detailed observations of field morphology on scales ranging from clouds to cores. However, ground based millimetre/submillimetre polarimetry is usually limited to small maps of relatively dense regions. BLASTPol, the Balloon-borne Large Aperture Sub-mm Telescope for Polarimetry, maps linear polarization at 250, 350 and 500 microns with arcminute resolution. Its high sensitivity and resolving power allow BLASTPol to bridge the gap in spatial scales between the polarization capabilities of Planck and ALMA.I will present early results from the second flight of BLASTPol, focusing on our observations of the Vela C molecular cloud, an early stage intermediate mass star forming region (d~700 pc). With thousands of independent measurements of magnetic field direction, this is the most detailed sub-mm polarization map of a GMC to date. The field we observe in this elongated cloud exhibits a coherent, large-scale ~ 90 degree bend between its high latitude and low latitude edges. I will discuss what we can learn about star formation in Vela C from the combination of BLASTPol polarization maps and velocity information from molecular line observations, and what the variation of polarization strength across the cloud can tell us about dust grain alignment in GMCs.

  16. Structural specifics of light-induced metastable states in copper(II)-nitroxide molecular magnets.

    PubMed

    Barskaya, I Yu; Veber, S L; Fokin, S V; Tretyakov, E V; Bagryanskaya, E G; Ovcharenko, V I; Fedin, M V

    2015-12-28

    Although light-induced magnetostructural switching in copper(II)-nitroxide molecular magnets Cu(hfac)2L(R) has been known for several years, structural characterization of metastable photoinduced states has not yet been accomplished due to significant technical demands. In this work we apply, for the first time, variable-temperature FTIR spectroscopy with photoexcitation to investigate the structural specifics of light-induced states in the Cu(hfac)2L(R) family represented by (i) Cu(hfac)2L(Me) comprising two-spin copper(II)-nitroxide clusters, and (ii) Cu(hfac)2L(Pr) comprising three-spin nitroxide-copper(II)-nitroxide clusters. The light-induced state of Cu(hfac)2L(Me) manifests the same set of vibrational bands as the corresponding thermally-induced state, implying their similar structures. For the second compound Cu(hfac)2L(Pr), the coordination environment of copper(II) is similar in light- and thermally-induced states, but distinct differences are found for packing of the peripheral n-propyl substituent of nitroxide. Thus, generally the structures of the corresponding thermally- and light-induced states in molecular magnets Cu(hfac)2L(R) might differ, and FTIR spectroscopy provides a useful approach for revealing and elucidating such differences. PMID:26571045

  17. Nuclear magnetic relaxation, correlation time spectrum, and molecular dynamics in a linear polymer

    SciTech Connect

    Chernov, V. M. Krasnopol'skii, G. S.

    2008-08-15

    The pulsed nuclear magnetic resonance (NMR) method at a proton frequency of 25 MHz at temperatures of 22-160{sup o}C is used to detect the transverse magnetization decay in polyisoprene rubbers with various molecular masses, to determine the NMR damping time T{sub 2}, and to measure spin-lattice relaxation time T{sub 1} and time T{sub 2eff} of damping of solid-echo signals under the action of a sequence of MW-4 pulses modified by introducing 180{sup o} pulses. The dispersion dependences of T{sub 2eff} obtained for each temperature are combined into one using the temperature-frequency equivalence principle. On the basis of the combined dispersion dependence of T{sub 2eff} and the data on T{sub 2} and T{sub 1}, the correlation time spectrum of molecular movements is constructed. Analysis of the shape of this spectrum shows that the dynamics of polymer molecules can be described in the first approximation by the Doi-Edwards tube-reptation model.

  18. Nurturing the Careers of Australia's Future Composers

    ERIC Educational Resources Information Center

    Watson, Amanda; Forrest, David

    2008-01-01

    In 1994, the Australian Society for Music Education (ASME) initiated two related projects supporting and acknowledging composition in schools and offering the opportunity for secondary school-aged students to work with prominent Australian composers. These were the Young Composers' Project and the Composer-in-Residence Project. Both projects were…

  19. Composers and Children: A Future Creative Force?

    ERIC Educational Resources Information Center

    Colgrass, Michael

    2004-01-01

    In this article, a professional composer shares his experiences writing music for a middle school band. Michael Colgrass was commissioned, along with fourteen other composers, by the American Composers Forum BandQuest project to write a short piece for eighth-grade band. They were asked to pay a couple of visits to a nearby school to work with…

  20. Heisenberg coupling constant predicted for molecular magnets with pairwise spin-contamination correction

    NASA Astrophysics Data System (ADS)

    Masunov, Artëm E.; Gangopadhyay, Shruba

    2015-12-01

    New method to eliminate the spin-contamination in broken symmetry density functional theory (BS DFT) calculations is introduced. Unlike conventional spin-purification correction, this method is based on canonical Natural Orbitals (NO) for each high/low spin coupled electron pair. We derive an expression to extract the energy of the pure singlet state given in terms of energy of BS DFT solution, the occupation number of the bonding NO, and the energy of the higher spin state built on these bonding and antibonding NOs (not self-consistent Kohn-Sham orbitals of the high spin state). Compared to the other spin-contamination correction schemes, spin-correction is applied to each correlated electron pair individually. We investigate two binuclear Mn(IV) molecular magnets using this pairwise correction. While one of the molecules is described by magnetic orbitals strongly localized on the metal centers, and spin gap is accurately predicted by Noodleman and Yamaguchi schemes, for the other one the gap is predicted poorly by these schemes due to strong delocalization of the magnetic orbitals onto the ligands. We show our new correction to yield more accurate results in both cases.

  1. Properties and catalytic activity of magnetic and acidic ionic liquids: experimental and molecular simulation.

    PubMed

    Zhou, Cunshan; Yu, Xiaojie; Ma, Haile; Huang, Xingyi; Zhang, Henan; Jin, Jian

    2014-05-25

    The exploitation of dual functional magnetic and acidic ionic liquids (MAILs) for hydrolysis of cellulose to platform chemicals can solve some practical challenges through easy separation of products and efficient catalyst recyclability. In this work, seven Cnmim/FeCl4 MAILs were synthesized and investigated with combined experimental and molecular dynamics. The MAILs contained FeCl4(-) anions and exhibited a typical hard magnetic materials behavior with rather strong magnetic susceptibilities. These MAILs were stable up to 250-310°C, the decomposition was started up at 250/310-480-810°C in two steps with the formation of the undecomposed residue. The Gibbs energy for the reaction of glucose/xylose conversion to 5-hydroxymethylfurfural by metal chlorides in the CnmimCl ionic liquid was studied using the density functional theory calculations and the results that C3mim/WCl3 may be the most hopeful catalyst. The MAILs have the potential to open up promising new catalytic systems because of their easy product separation and efficient catalyst recyclability. PMID:24708984

  2. Solvent triggered structural diversity of triple-stranded helicates: single molecular magnets.

    PubMed

    Li, Hongfeng; Chen, Peng; Sun, Wenbin; Zhang, Lei; Yan, Pengfei

    2016-02-21

    Multiple-stranded helicates are of interest in respect of their simplicity in geometry and significance in biology and materials. Bis-β-diketones have shown their advantage in terms of structure and geometry in the construction of multiple-stranded helicates, but further studies on their properties are limited due to their poor crystallization. In this study, solvents are found to play a decisive role in the crystallization of triple-stranded helicates. [Dy2(BTB)3(H2O)4] is used as a precursor to solvent-dependently crystallize three complexes [Dy2(BTB)3(CH3OH)4]·3CH3OH (1), [Dy2(BTB)3(DME)2] (2) and [Dy2(BTB)3(DOA)(H2O)2]·4.5DOA (3) (BTB = 3,3'-bis(4,4,4-trifluoro-1,3-dioxobutyl)biphenyl), where the key structural motif of the triple-stranded helicate, [Dy2(BTB)3], is retained. Four methanol molecules are found to ligate to Dy(3+) ions in 1, while each Dy(3+) ion is chelated by one DME molecule in 2. Interestingly, it is observed that 1,4-dioxane as a bridge ligates to two adjacent Dy(3+) ions, giving rise to the formation of a 1D chain structure. Magnetic measurement shows that 1 and 2 display slow magnetic relaxation under zero dc field, while single molecular magnet behavior is obtained for 3 under an applied dc field of 2000 Oe. PMID:26781997

  3. Determination of malachite green in aquatic products based on magnetic molecularly imprinted polymers.

    PubMed

    Lin, Zheng-zhong; Zhang, Hong-yuan; Peng, Ai-hong; Lin, Yi-dong; Li, Lu; Huang, Zhi-yong

    2016-06-01

    Magnetic molecularly imprinted polymers (MMIPs) were synthesized through precipitation polymerization using malachite green (MG) as template, methacrylic acid as monomer, ethylene dimethacrylate as crosslinker, and Fe3O4 magnetite as magnetic component. MMIPs were characterized by scanning electron microscopy, Fourier transform infrared spectrometry, and vibrating sample magnetometry. Under the optimum condition, the MMIPs obtained exhibited quick binding kinetics and high affinity to MG in the solution. Scatchard plot analysis revealed that the MMIPs contained only one type of binding site with dissociation constant of 24.0 μg mL(-1). The selectivity experiment confirmed that the MMIPs exhibited higher selective binding capacity for MG than its structurally related compound (e.g., crystal violet). As a sorbent for the extraction of MG in sample preparation, MMIPs together with the absorbed analytes could easily be separated from the sample matrix with an external magnet. After elution with methanol/acetic acid (9:1, v/v), MG in the eluent was determined by high-performance liquid chromatography coupled with UV detector with recoveries of 94.0-115%. Results indicated that the as-prepared MMIPs are promising materials for MG analysis in aquatic products. PMID:26830557

  4. Preparation and characterization of a magnetic and optical dual-modality molecular probe

    NASA Astrophysics Data System (ADS)

    Bumb, A.; Regino, C. A. S.; Perkins, M. R.; Bernardo, M.; Ogawa, M.; Fugger, L.; Choyke, P. L.; Dobson, P. J.; Brechbiel, M. W.

    2010-04-01

    Multi-modality imaging probes combine the advantages of individual imaging techniques to yield highly detailed anatomic and molecular information in living organisms. Herein, we report the synthesis and characterization of a dual-modality nanoprobe that couples the magnetic properties of ultrasmall superparamagnetic iron oxide nanoparticles (USPIOs) with the near infrared fluorescence of Cy5.5. The fluorophore is encapsulated in a biocompatible shell of silica surrounding the iron oxide core for a final diameter of ~ 17 nm. This silica-coated iron oxide nanoparticle (SCION) has been analyzed by transmission electron microscopy, dynamic light scattering, and superconducting quantum interference device (SQUID). The particle demonstrates a strong negative surface charge and maintains colloidal stability in the physiological pH range. Magnetic hysteresis analysis confirms superparamagnetic properties that could be manipulated for thermotherapy. The viability of primary human monocytes, T cells, and B cells incubated with the particle has been examined in vitro. In vivo analysis of agent leakage into subcutaneous A431 tumors in mice was also conducted. This particle has been designed for diagnostic application with magnetic resonance and fluorescence imaging, and has future potential to serve as a heat-sensitive targeted drug delivery platform.

  5. Molecular magnetic resonance probe targeting VEGF165: preparation and in vitro and in vivo evaluation.

    PubMed

    You, Xiao-Guang; Tu, Rong; Peng, Ming-Li; Bai, Yu-Jie; Tan, Mingqian; Li, Han-Jian; Guan, Jing; Wen, Li-Jun

    2014-01-01

    A new method for imaging the tumor human vascular endothelial growth factor 165 (VEGF 165) is presented. A magnetic resonance imaging (MRI) probe was prepared by crosslinking ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles to the aptamer for tumor vascular endothelial growth factor 165 (VEGF165-aptamer). The molecular probe was evaluated for its in vitro and in vivo activities toward VEGF165. Enzyme-linked immunosorbent assay showed that the VEGF165-aptamer-USPIO nanoparticles conjugate specifically binds to VEGF165 in vitro. A cell proliferation test showed that VEGF165-aptamer-USPIO seems to block the proliferation of human umbilical vein endothelial cells induced by free VEGF165, suggesting that VEGF165 is an effective target of this molecular probe. In xenograft mice carrying liver cancer that expresses VEGF165, T2-weighted imaging of the tumor displayed marked negative enhancement 3 h after the intravenous administration of VEGF165-aptamer-USPIO. The enhancement disappeared 6 h after administration of the probe. These results suggest the targeted imaging effect of VEGF165-aptamer-USPIO probe in vivo for VEGF165-expressing tumors. This is the first report of a targeted MRI molecular probe based on USPIO and VEGF165-aptamer. PMID:24729581

  6. A symmetry model for genetic coding via a wallpaper group composed of the traditional four bases and an imaginary base E: Towards category theory-like systematization of molecular/genetic biology

    PubMed Central

    2014-01-01

    Background Previously, we suggested prototypal models that describe some clinical states based on group postulates. Here, we demonstrate a group/category theory-like model for molecular/genetic biology as an alternative application of our previous model. Specifically, we focus on deoxyribonucleic acid (DNA) base sequences. Results We construct a wallpaper pattern based on a five-letter cruciform motif with letters C, A, T, G, and E. Whereas the first four letters represent the standard DNA bases, the fifth is introduced for ease in formulating group operations that reproduce insertions and deletions of DNA base sequences. A basic group Z5 = {r, u, d, l, n} of operations is defined for the wallpaper pattern, with which a sequence of points can be generated corresponding to changes of a base in a DNA sequence by following the orbit of a point of the pattern under operations in group Z5. Other manipulations of DNA sequence can be treated using a vector-like notation ‘Dj’ corresponding to a DNA sequence but based on the five-letter base set; also, ‘Dj’s are expressed graphically. Insertions and deletions of a series of letters ‘E’ are admitted to assist in describing DNA recombination. Likewise, a vector-like notation Rj can be constructed for sequences of ribonucleic acid (RNA). The wallpaper group B = {Z5×∞, ●} (an ∞-fold Cartesian product of Z5) acts on Dj (or Rj) yielding changes to Dj (or Rj) denoted by ‘Dj◦B(j→k) = Dk’ (or ‘Rj◦B(j→k) = Rk’). Based on the operations of this group, two types of groups—a modulo 5 linear group and a rotational group over the Gaussian plane, acting on the five bases—are linked as parts of the wallpaper group for broader applications. As a result, changes, insertions/deletions and DNA (RNA) recombination (partial/total conversion) are described. As an exploratory study, a notation for the canonical “central dogma” via a category theory-like way is presented for future

  7. Strong impact of lattice vibrations on electronic and magnetic properties of paramagnetic Fe revealed by disordered local moments molecular dynamics

    NASA Astrophysics Data System (ADS)

    Alling, B.; Körmann, F.; Grabowski, B.; Glensk, A.; Abrikosov, I. A.; Neugebauer, J.

    2016-06-01

    We study the impact of lattice vibrations on magnetic and electronic properties of paramagnetic bcc and fcc iron at finite temperature, employing the disordered local moments molecular dynamics (DLM-MD) method. Vibrations strongly affect the distribution of local magnetic moments at finite temperature, which in turn correlates with the local atomic volumes. Without the explicit consideration of atomic vibrations, the mean local magnetic moment and mean field derived magnetic entropy of paramagnetic bcc Fe are larger compared to paramagnetic fcc Fe, which would indicate that the magnetic contribution stabilizes the bcc phase at high temperatures. In the present study we show that this assumption is not valid when the coupling between vibrations and magnetism is taken into account. At the γ -δ transition temperature (1662 K), the lattice distortions cause very similar magnetic moments of both bcc and fcc structures and hence magnetic entropy contributions. This finding can be traced back to the electronic densities of states, which also become increasingly similar between bcc and fcc Fe with increasing temperature. Given the sensitive interplay of the different physical excitation mechanisms, our results illustrate the need for an explicit consideration of vibrational disorder and its impact on electronic and magnetic properties to understand paramagnetic Fe. Furthermore, they suggest that at the γ -δ transition temperature electronic and magnetic contributions to the Gibbs free energy are extremely similar in bcc and fcc Fe.

  8. Information flow and protein dynamics: the interplay between nuclear magnetic resonance spectroscopy and molecular dynamics simulations.

    PubMed

    Pastor, Nina; Amero, Carlos

    2015-01-01

    Proteins participate in information pathways in cells, both as links in the chain of signals, and as the ultimate effectors. Upon ligand binding, proteins undergo conformation and motion changes, which can be sensed by the following link in the chain of information. Nuclear magnetic resonance (NMR) spectroscopy and molecular dynamics (MD) simulations represent powerful tools for examining the time-dependent function of biological molecules. The recent advances in NMR and the availability of faster computers have opened the door to more detailed analyses of structure, dynamics, and interactions. Here we briefly describe the recent applications that allow NMR spectroscopy and MD simulations to offer unique insight into the basic motions that underlie information transfer within and between cells. PMID:25999971

  9. Molecular Design Guidelines for Large Magnetic Circular Dichroism Intensities in Lanthanide Complexes.

    PubMed

    Kitagawa, Yuichi; Wada, Satoshi; Yanagisawa, Kei; Nakanishi, Takayuki; Fushimi, Koji; Hasegawa, Yasuchika

    2016-03-16

    Magneto optical devices based on the Faraday effects of lanthanide ion have attracted much attention. Recently, large Faraday effects were found in nano-sized multinuclear lanthanide complexes. In this study, the Faraday rotation intensities were estimated for lanthanide nitrates [Ln(III) (NO3 )3 ⋅n H2 O: Ln=Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm) and Eu(III) complexes with β-diketone ligands, using magnetic circular dichroism. Eu ions exhibit the largest Faraday rotation intensity for (7) F0 →(5) D1 transitions, and high-symmetry fields around the Eu ions induce larger Faraday effects. The molecular design for the enhancement of Faraday effects in lanthanide complexes is discussed. PMID:26789658

  10. Information flow and protein dynamics: the interplay between nuclear magnetic resonance spectroscopy and molecular dynamics simulations

    PubMed Central

    Pastor, Nina; Amero, Carlos

    2015-01-01

    Proteins participate in information pathways in cells, both as links in the chain of signals, and as the ultimate effectors. Upon ligand binding, proteins undergo conformation and motion changes, which can be sensed by the following link in the chain of information. Nuclear magnetic resonance (NMR) spectroscopy and molecular dynamics (MD) simulations represent powerful tools for examining the time-dependent function of biological molecules. The recent advances in NMR and the availability of faster computers have opened the door to more detailed analyses of structure, dynamics, and interactions. Here we briefly describe the recent applications that allow NMR spectroscopy and MD simulations to offer unique insight into the basic motions that underlie information transfer within and between cells. PMID:25999971

  11. Molecular orbital calculations of possible pinning centers for magnetic flux in copper oxide superconductors

    NASA Astrophysics Data System (ADS)

    Fukushima, Kimichika

    1993-07-01

    Cluster calculations using the molecular orbital method were performed to search for impurities which would act as pinning centers for magnetic flux in copper oxide superconductors. Electronic structures were first investigated for interstitial helium atoms and for He atoms (including He clusters) substituted for oxygen and copper atoms. Calculations were then done for F atoms substituted for O atoms, and C, Mg, Al, Zn, Ga, and Cd atoms substituted for Cu. With these impurities, the energies of orbitals mainly attributable to the impurities differ from the Fermi energy. The Mulliken populations show that most charge carriers do not exist on the impurity sites (though some charge carriers enter the C sites), so it can be expected that the impurities considered here will act as pinning centers.

  12. The composing process in technical communication

    NASA Technical Reports Server (NTRS)

    Masse, R. E.

    1981-01-01

    The theory and application of the composing process in technical communications is addressed. The composing process of engineers, some implications for composing research for the teaching and research of technical communication, and an interpretation of the processes as creative experience are also discussed. Two areas of technical communications summarized concern: the rhetorical features of technical communications, and the theoretical background for a process-based view, a problem-solving approach to technical writing.

  13. Magnetic molecularly imprinted polymers synthesized by surface-initiated reversible addition-fragmentation chain transfer polymerization for the enrichment and determination of synthetic estrogens in aqueous solution.

    PubMed

    Chen, Fangfang; Zhang, Jingjing; Wang, Minjun; Kong, Jie

    2015-08-01

    Magnetic molecularly imprinted polymers have attracted significant interest because of their multifunctionality of selective recognition of target molecules and rapid magnetic response. In this contribution, magnetic molecularly imprinted polymers were synthesized via surface-initiated reversible addition addition-fragmentation chain transfer polymerization using diethylstilbestrol as the template for the enrichment of synthetic estrogens. The uniform imprinted surface layer and the magnetic property of the magnetic molecularly imprinted polymers favored a fast binding kinetics and rapid analysis of target molecules. The static and selective binding experiments demonstrated a desirable adsorption capacity and good selectivity of the magnetic molecularly imprinted polymers in comparison to magnetic non-molecularly imprinted polymers. Accordingly, a corresponding analytical method was developed in which magnetic molecularly imprinted polymers were employed as magnetic solid-phase extraction materials for the concentration and determination of four synthetic estrogens (diethylstilbestrol, hexestrol, dienestrol, and bisphenol A) in fish pond water. The recoveries of these synthetic estrogens in spiked fish pond water samples ranged from 61.2 to 99.1% with a relative standard deviation of lower than 6.3%. This study provides a versatile approach to prepare well-defined magnetic molecularly imprinted polymers sorbents for the analysis of synthetic estrogens in water solution. PMID:25989155

  14. The thickness-dependent dynamic magnetic property of Co2FeAl films grown by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Qiao, Shuang; Nie, Shuaihua; Zhao, Jianhua; Zhang, Xinhui

    2014-10-01

    Co2FeAl films with different thickness were prepared at different temperature by molecular beam epitaxy. Their dynamic magnetic property was studied by the time-resolved magneto-optical Kerr effect measurements. It is observed that the intrinsic damping factor of Co2FeAl for [100] orientation is not related to the film's thickness and magnetic anisotropy as well as temperature at high-field regime, but increases with structural disorder of Co2FeAl. The dominant contribution from the inhomogeneous magnetic anisotropy is revealed to be responsible for the observed extremely nonlinear and drastic field-dependent damping factors at low-field regime.

  15. Design of magnetic molecularly imprinted polymer nanoparticles for controlled release of doxorubicin under an alternative magnetic field in athermal conditions.

    PubMed

    Griffete, N; Fresnais, J; Espinosa, A; Wilhelm, C; Bée, A; Ménager, C

    2015-12-01

    An innovative magnetic delivery nanomaterial for triggered cancer therapy showing active control over drug release by using an alternative magnetic field is proposed. In vitro and In vivo release of doxorubicin (DOX) were investigated and showed a massive DOX release under an alternative magnetic field without temperature elevation of the medium. PMID:26515533

  16. Mid-Infrared Spectropolarimetry of Molecular Cloud Sources: Magnetic Fields and Dust Properties

    NASA Astrophysics Data System (ADS)

    Wright, Christopher Mathew

    1994-12-01

    One of the earliest phases of the star formation process is the bipolar outflow. It is not presently understood how the outflow is generated, but a number of theories propose that a dynamically important magnetic field, embedded in the disk and acting in concert with rotation, is able to tap the gravitational potential well of the star plus disk system to drive material off the disk surface. Spectropolarimetric observations between 8 and 13 micrometers provide information on the chemical and physical nature of dust grains, as well as on the direction of the transverse (to the line-of-sight) component of an aligning magnetic field. In this thesis, such observations toward a selection of mainly high mass young stellar objects (YSO's) are presented. The field directions inferred from the polarization position angle are compared with the axes of disks and bipolar outflows associated with the sources. A strong correlation is found such that the field tends to lie in the plane of the disk, thereby providing support for the magnetic pressure mechanism for bipolar outflows. The observed field directions are also compared with the interstellar field configuration determined from optical polarization of field stars and obtained from the literature. Two distributions are observed, one in which the difference between the position angles of the two fields is less than 30 deg, and the other for which the difference is greater than 30 deg. The existence of the second group implies that the evolution of the YSO has a significant perturbing effect on its ambient magnetic field. Together with the disk field finding, the results are discussed in terms of the initial collapse phase of the molecular cloud in which the YSO is embedded, specifically whether the cloud was supercritical or subcritical. For instance, for two high mass objects, AFGL 2591 and AFGL 989, and one low mass object, SVS13, the source and interstellar fields, and interstellar field and disk major axes, are inclined

  17. Fast and selective extraction of sulfonamides from honey based on magnetic molecularly imprinted polymer.

    PubMed

    Chen, Ligang; Zhang, Xiaopan; Sun, Lei; Xu, Yang; Zeng, Qinglei; Wang, Hui; Xu, Haoyan; Yu, Aimin; Zhang, Hanqi; Ding, Lan

    2009-11-11

    A fast and selective method was developed for the determination of sulfonamides (SAs) in honey based on magnetic molecularly imprinted polymer. The extraction was carried out by blending and stirring the sample, extraction solvent and polymers. When the extraction was complete, the polymers, along with the captured analytes, were easily separated from the sample matrix by an adscititious magnet. The analytes eluted from the polymers were determined by liquid chromatography-tandem mass spectrometry. Under the optimal conditions, the detection limits of SAs are in the range of 1.5-4.3 ng g(-1). The relative standard deviations of intra- and interday ranging from 3.7% to 7.9% and from 4.3% to 9.9% are obtained, respectively. The proposed method was successfully applied to determine SAs including sulfadiazine, sulfamerazine, sulfamethoxydiazine, sulfamonomethoxine, sulfadimethoxine, sulfamethoxazole and sulfaquinoxaline in different honey samples. The recoveries of SAs in these samples from 67.1% to 93.6% were obtained. PMID:19817457

  18. Determination of malachite green in fish based on magnetic molecularly imprinted polymer extraction followed by electrochemiluminescence.

    PubMed

    Huang, Baomei; Zhou, Xibin; Chen, Jing; Wu, Guofan; Lu, Xiaoquan

    2015-09-01

    A novel procedure for selective extraction of malachite green (MG) from fish samples was set up by using magnetic molecularly imprinted polymers (MMIP) as the solid phase extraction material followed by electrochemiluminescence (ECL) determination. MMIP was prepared by using Fe3O4 magnetite as magnetic component, MG as template molecule, methacrylic acid (MAA) as functional monomer and ethylene glycol dimethacrylate (EGDMA) as crosslinking agent. MMIP was characterized by SEM, TEM, FT-IR, VSM and XRD. Leucomalachite green (LMG) was oxidized in situ to MG by 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ). And then MMIP was successfully used to selectively enrich MG from fish samples. Adsorbed MG was desorbed and determined by ECL. Under the optimal conditions, calibration curve was good linear in the range of 0.29-290 μg/kg and the limit of detection (LOD) was 7.3 ng/kg (S/N=3). The recoveries of MMIP extraction were 77.1-101.2%. In addition, MMIP could be regenerated. To the best of our knowledge, MMIP coupling with ECL quenching of Ru(bpy)3(2+)/TPA for the determination of MG has not yet been developed. PMID:26003716

  19. Magnetosomes, biogenic magnetic nanomaterials for brain molecular imaging with 17.2 T MRI scanner.

    PubMed

    Mériaux, Sébastien; Boucher, Marianne; Marty, Benjamin; Lalatonne, Yoann; Prévéral, Sandra; Motte, Laurence; Lefèvre, Christopher T; Geffroy, Françoise; Lethimonnier, Franck; Péan, Michel; Garcia, Daniel; Adryanczyk-Perrier, Géraldine; Pignol, David; Ginet, Nicolas

    2015-05-01

    The fast development of sensitive molecular diagnostic tools is currently paving the way for a personalized medicine. A new class of ultrasensitive magnetic resonance imaging (MRI) T₂-contrast agents based on magnetosomes, magnetite nanocrystals biomineralized by magnetotactic bacteria, is proposed here. The contrast agents can be injected into the blood circulation and detected in the picomolar range. Purified magnetosomes are water-dispersible and stable within physiological conditions and exhibit at 17.2 T a transverse relaxivity r₂ four times higher than commercial ferumoxide. The subsequent gain in sensitivity by T₂(*) -weighted imaging at 17.2 T of the mouse brain vasculature is evidenced in vivo after tail vein injection of magnetosomes representing a low dose of iron (20 μmoliron kg(-1)), whereas no such phenomenon with the same dose of ferumoxide is observed. Preclinical studies of human pathologies in animal models will benefit from the combination of high magnetic field MRI with sensitive, low dose, easy-to-produce biocompatible contrast agents derived from bacterial magnetosomes. PMID:25676134

  20. Magnetic materials at finite temperatures: thermodynamics and combined spin and molecular dynamics derived from first principles calculations

    SciTech Connect

    Eisenbach, Markus; Perera, Meewanage Dilina N.; Landau, David P; Nicholson, Don M.; Yin, Junqi; Brown, Greg

    2015-01-01

    We present a unified approach to describe the combined behavior of the atomic and magnetic degrees of freedom in magnetic materials. Using Monte Carlo simulations directly combined with first principles the Curie temperature can be obtained ab initio in good agreement with experimental values. The large scale constrained first principles calculations have been used to construct effective potentials for both the atomic and magnetic degrees of freedom that allow the unified study of influence of phonon-magnon coupling on the thermodynamics and dynamics of magnetic systems. The MC calculations predict the specific heat of iron in near perfect agreement with experimental results from 300K to above Tc and allow the identification of the importance of the magnon-phonon interaction at the phase-transition. Further Molecular Dynamics and Spin Dynamics calculations elucidate the dynamics of this coupling and open the potential for quantitative and predictive descriptions of dynamic structure factors in magnetic materials using first principles-derived simulations.

  1. Membrane-Permeable Mn(III) Complexes for Molecular Magnetic Resonance Imaging of Intracellular Targets.

    PubMed

    Barandov, Ali; Bartelle, Benjamin B; Gonzalez, Beatriz A; White, William L; Lippard, Stephen J; Jasanoff, Alan

    2016-05-01

    Intracellular compartments make up roughly two-thirds of the body, but delivery of molecular imaging probes to these spaces can be challenging. This situation is particularly true for probes designed for detection by magnetic resonance imaging (MRI), a high-resolution but relatively insensitive modality. Most MRI contrast agents are polar and membrane impermeant, making it difficult to deliver them in sufficient quantities for measurement of intracellular analytes. Here we address this problem by introducing a new class of planar tetradentate Mn(III) chelates assembled from a 1,2-phenylenediamido (PDA) backbone. Mn(III)-PDA complexes display T1 relaxivity comparable to that of Gd(III)-based contrast agents and undergo spontaneous cytosolic localization via defined mechanisms. Probe variants incorporating enzyme-cleavable acetomethoxy ester groups are processed by intracellular esterases and accumulate in cells. Probes modified with ethyl esters preferentially label genetically modified cells that express a substrate-selective esterase. In each case, the contrast agents gives rise to robust T1-weighted MRI enhancements, providing precedents for the detection of intracellular targets by Mn(III)-PDA complexes. These compounds therefore constitute a platform from which to develop reagents for molecular MRI of diverse processes inside cells. PMID:27088782

  2. Magnetic molecularly imprinted polymer for the selective extraction of quercetagetin from Calendula officinalis extract.

    PubMed

    Ma, Run-Tian; Shi, Yan-Ping

    2015-03-01

    A new magnetic molecularly imprinted polymers (MMIPs) for quercetagetin was prepared by surface molecular imprinting method using super paramagnetic core-shell nanoparticle as the supporter. Acrylamide as the functional monomer, ethyleneglycol dimethacrylate as the crosslinker and acetonitrile as the porogen were applied in the preparation process. Fourier transform infrared spectrometer (FT-IR), X-ray diffraction (XRD) and Vibrating sample magnetometer (VSM) were applied to characterize the MMIPs, and High performance liquid chromatography (HPLC) was utilized to analyze the target analytes. The selectivity of quercetagetin MMIPs was evaluated according to their recognition to template and its analogues. Excellent binding for quercetagetin was observed in MMIPs adsorption experiment, and the adsorption isotherm models analysis showed that the homogeneous binding sites were distributed on the surface of the MMIPs. The MMIPs were employed as adsorbents in solid phase extraction for the determination of quercetagetin in Calendula officinalis extracts. Furthermore, this method is fast, simple and could fulfill the determination and extraction of quercetagetin from herbal extract. PMID:25618718

  3. Core-shell magnetic molecularly imprinted polymers as sorbent for sulfonylurea herbicide residues.

    PubMed

    Miao, Shan Shan; Wu, Mei Sheng; Zuo, Hai Gen; Jiang, Chen; Jin, She Feng; Lu, Yi Chen; Yang, Hong

    2015-04-15

    Sulfonylurea herbicides are widely used at lower dosage for controlling broad-leaf weeds and some grasses in cereals and economic crops. It is important to develop a highly efficient and selective pretreatment method for analyzing sulfonylurea herbicide residues in environments and samples from agricultural products based on magnetic molecularly imprinted polymers (MIPs). The MIPs were prepared by a surface molecular imprinting technique especially using the vinyl-modified Fe3O4@SiO2 nanoparticle as the supporting matrix, bensulfuron-methyl (BSM) as the template molecule, methacrylic acid (MAA) as a functional monomer, trimethylolpropane trimethacrylate (TRIM) as a cross-linker, and azodiisobutyronitrile (AIBN) as an initiator. The MIPs show high affinity, recognition specificity, fast mass transfer rate, and efficient adsorption performance toward BSM with the adsorption capacity reaching up to 37.32 mg g(-1). Furthermore, the MIPs also showed cross-selectivity for herbicides triasulfuron (TS), prosulfuron (PS), and pyrazosulfuron-ethyl (PSE). The MIP solid phase extraction (SPE) column was easier to operate, regenerate, and retrieve compared to those of C18 SPE column. The developed method showed highly selective separation and enrichment of sulfonylurea herbicide residues, which enable its application in the pretreatment of multisulfonylurea herbicide residues. PMID:25797565

  4. High-resolution low-field molecular magnetic resonance imaging of hyperpolarized liquids.

    PubMed

    Coffey, Aaron M; Kovtunov, Kirill V; Barskiy, Danila A; Koptyug, Igor V; Shchepin, Roman V; Waddell, Kevin W; He, Ping; Groome, Kirsten A; Best, Quinn A; Shi, Fan; Goodson, Boyd M; Chekmenev, Eduard Y

    2014-09-16

    We demonstrate the feasibility of microscale molecular imaging using hyperpolarized proton and carbon-13 MRI contrast media and low-field (47.5 mT) preclinical scale (38 mm i.d.) 2D magnetic resonance imaging (MRI). Hyperpolarized proton images with 94 × 94 μm(2) spatial resolution and hyperpolarized carbon-13 images with 250 × 250 μm(2) in-plane spatial resolution were recorded in 4-8 s (largely limited by the electronics response), surpassing the in-plane spatial resolution (i.e., pixel size) achievable with micro-positron emission tomography (PET). These hyperpolarized proton and (13)C images were recorded using large imaging matrices of up to 256 × 256 pixels and relatively large fields of view of up to 6.4 × 6.4 cm(2). (13)C images were recorded using hyperpolarized 1-(13)C-succinate-d2 (30 mM in water, %P(13C) = 25.8 ± 5.1% (when produced) and %P(13C) = 14.2 ± 0.7% (when imaged), T1 = 74 ± 3 s), and proton images were recorded using (1)H hyperpolarized pyridine (100 mM in methanol-d4, %P(H) = 0.1 ± 0.02% (when imaged), T1 = 11 ± 0.1 s). Both contrast agents were hyperpolarized using parahydrogen (>90% para-fraction) in an automated 5.75 mT parahydrogen induced polarization (PHIP) hyperpolarizer. A magnetized path was demonstrated for successful transportation of a (13)C hyperpolarized contrast agent (1-(13)C-succinate-d2, sensitive to fast depolarization when at the Earth's magnetic field) from the PHIP polarizer to the 47.5 mT low-field MRI. While future polarizing and low-field MRI hardware and imaging sequence developments can further improve the low-field detection sensitivity, the current results demonstrate that microscale molecular imaging in vivo is already feasible at low (<50 mT) fields and potentially at low (~1 mM) metabolite concentrations. PMID:25162371

  5. High-Resolution Low-Field Molecular Magnetic Resonance Imaging of Hyperpolarized Liquids

    PubMed Central

    2015-01-01

    We demonstrate the feasibility of microscale molecular imaging using hyperpolarized proton and carbon-13 MRI contrast media and low-field (47.5 mT) preclinical scale (38 mm i.d.) 2D magnetic resonance imaging (MRI). Hyperpolarized proton images with 94 × 94 μm2 spatial resolution and hyperpolarized carbon-13 images with 250 × 250 μm2 in-plane spatial resolution were recorded in 4–8 s (largely limited by the electronics response), surpassing the in-plane spatial resolution (i.e., pixel size) achievable with micro-positron emission tomography (PET). These hyperpolarized proton and 13C images were recorded using large imaging matrices of up to 256 × 256 pixels and relatively large fields of view of up to 6.4 × 6.4 cm2. 13C images were recorded using hyperpolarized 1-13C-succinate-d2 (30 mM in water, %P13C = 25.8 ± 5.1% (when produced) and %P13C = 14.2 ± 0.7% (when imaged), T1 = 74 ± 3 s), and proton images were recorded using 1H hyperpolarized pyridine (100 mM in methanol-d4, %PH = 0.1 ± 0.02% (when imaged), T1 = 11 ± 0.1 s). Both contrast agents were hyperpolarized using parahydrogen (>90% para-fraction) in an automated 5.75 mT parahydrogen induced polarization (PHIP) hyperpolarizer. A magnetized path was demonstrated for successful transportation of a 13C hyperpolarized contrast agent (1-13C-succinate-d2, sensitive to fast depolarization when at the Earth’s magnetic field) from the PHIP polarizer to the 47.5 mT low-field MRI. While future polarizing and low-field MRI hardware and imaging sequence developments can further improve the low-field detection sensitivity, the current results demonstrate that microscale molecular imaging in vivo is already feasible at low (<50 mT) fields and potentially at low (∼1 mM) metabolite concentrations. PMID:25162371

  6. The Composing Processes of Unskilled College Writers.

    ERIC Educational Resources Information Center

    Perl, Sondra

    The findings from a study of five students undertaken to determine how unskilled college writers compose, whether their writing processes can be analyzed in a systematic manner, and what an increased understanding of those processes suggests about the nature of composing and about the manner in which writing is taught are presented in this paper.…

  7. A Virtual Composer in Every Classroom

    ERIC Educational Resources Information Center

    Hoffman, Adria R.; Carter, Bruce A.

    2013-01-01

    Previous generations applauded grant-funded programs that brought living composers into the lives of K-12 music students. The current economic climate, however, limits opportunities similar to those enjoyed in the past. We designed a virtual composer-in-residence experience that uses technology to overcome the barriers of funding limitations and…

  8. America's Women Composers: Up from the Footnotes.

    ERIC Educational Resources Information Center

    Pool, Jeannie G.

    1979-01-01

    This article presents an overview on women composers in the United States from the eighteenth century to the present. It also lists women's musical organizations, selected references on women in music, and available recordings of works by American women composers. (SJL)

  9. Supramolecular control over molecular magnetic materials: γ-cyclodextrin-templated grid of cobalt(II) single-ion magnets.

    PubMed

    Nedelko, Natalia; Kornowicz, Arkadiusz; Justyniak, Iwona; Aleshkevych, Pavlo; Prochowicz, Daniel; Krupiński, Piotr; Dorosh, Orest; Ślawska-Waniewska, Anna; Lewiński, Janusz

    2014-12-15

    Single-ion magnets (SIMs) are potential building blocks of novel quantum computing devices. Unique magnetic properties of SIMs require effective separation of magnetic ions and can be tuned by even slight changes in their coordination sphere geometry. We show that an additional level of tailorability in the design of SIMs can be achieved by organizing magnetic ions into supramolecular architectures, resulting in gaining control over magnetic ion packing. Here, γ-cyclodextrin was used to template magnetic Co(II) and nonmagnetic auxiliary Li(+) ions to form a heterometallic {Co, Li, Li}4 ring. In the sandwich-type complex [(γ-CD)2Co4Li8(H2O)12] spatially separated Co(II) ions are prevented from superexchange magnetic coupling. Ac/dc magnetic and EPR studies demonstrated that individual Co(II) ions with positive zero-field splitting exhibit field-induced slow magnetic relaxation consistent with the SIMs' behavior, which is exceptional in complexes with easy-plane magnetic anisotropy. PMID:25494948

  10. Design of magnetic molecularly imprinted polymer nanoparticles for controlled release of doxorubicin under an alternative magnetic field in athermal conditions

    NASA Astrophysics Data System (ADS)

    Griffete, N.; Fresnais, J.; Espinosa, A.; Wilhelm, C.; Bée, A.; Ménager, C.

    2015-11-01

    An innovative magnetic delivery nanomaterial for triggered cancer therapy showing active control over drug release by using an alternative magnetic field is proposed. In vitro and In vivo release of doxorubicin (DOX) were investigated and showed a massive DOX release under an alternative magnetic field without temperature elevation of the medium.An innovative magnetic delivery nanomaterial for triggered cancer therapy showing active control over drug release by using an alternative magnetic field is proposed. In vitro and In vivo release of doxorubicin (DOX) were investigated and showed a massive DOX release under an alternative magnetic field without temperature elevation of the medium. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr06133d

  11. Estrogen Receptor-Targeted Contrast Agents for Molecular Magnetic Resonance Imaging of Breast Cancer Hormonal Status.

    PubMed

    Pais, Adi; Degani, Hadassa

    2016-01-01

    The estrogen receptor (ER) α is overexpressed in most breast cancers, and its level serves as a major prognostic factor. It is important to develop quantitative molecular imaging methods that specifically detect ER in vivo and assess its function throughout the entire primary breast cancer and in metastatic breast cancer lesions. This study presents the biochemical and molecular features, as well as the magnetic resonance imaging (MRI) effects of two novel ER-targeted contrast agents (CAs), based on pyridine-tetra-acetate-Gd(III) chelate conjugated to 17β-estradiol (EPTA-Gd) or to tamoxifen (TPTA-Gd). The experiments were conducted in solution, in human breast cancer cells, and in severe combined immunodeficient mice implanted with transfected ER-positive and ER-negative MDA-MB-231 human breast cancer xenografts. Binding studies with ER in solution and in human breast cancer cells indicated affinities in the micromolar range of both CAs. Biochemical and molecular studies in breast cancer cell cultures showed that both CAs exhibit estrogen-like agonistic activity, enhancing cell proliferation, as well as upregulating cMyc oncogene and downregulating ER expression levels. The MRI longitudinal relaxivity was significantly augmented by EPTA-Gd in ER-positive cells as compared to ER-negative cells. Dynamic contrast-enhanced studies with EPTA-Gd in vivo indicated specific augmentation of the MRI water signal in the ER-positive versus ER-negative xenografts, confirming EPTA-Gd-specific interaction with ER. In contrast, TPTA-Gd did not show increased enhancement in ER-positive tumors and did not appear to interact in vivo with the tumors' ER. However, TPTA-Gd was found to interact strongly with muscle tissue, enhancing muscle signal intensity in a mechanism independent of the presence of ER. The specificity of EPTA-Gd interaction with ER in vivo was further verified by acute and chronic competition with tamoxifen. The chronic tamoxifen treatment also revealed that this

  12. Estrogen Receptor-Targeted Contrast Agents for Molecular Magnetic Resonance Imaging of Breast Cancer Hormonal Status

    PubMed Central

    Pais, Adi; Degani, Hadassa

    2016-01-01

    The estrogen receptor (ER) α is overexpressed in most breast cancers, and its level serves as a major prognostic factor. It is important to develop quantitative molecular imaging methods that specifically detect ER in vivo and assess its function throughout the entire primary breast cancer and in metastatic breast cancer lesions. This study presents the biochemical and molecular features, as well as the magnetic resonance imaging (MRI) effects of two novel ER-targeted contrast agents (CAs), based on pyridine-tetra-acetate-Gd(III) chelate conjugated to 17β-estradiol (EPTA-Gd) or to tamoxifen (TPTA-Gd). The experiments were conducted in solution, in human breast cancer cells, and in severe combined immunodeficient mice implanted with transfected ER-positive and ER-negative MDA-MB-231 human breast cancer xenografts. Binding studies with ER in solution and in human breast cancer cells indicated affinities in the micromolar range of both CAs. Biochemical and molecular studies in breast cancer cell cultures showed that both CAs exhibit estrogen-like agonistic activity, enhancing cell proliferation, as well as upregulating cMyc oncogene and downregulating ER expression levels. The MRI longitudinal relaxivity was significantly augmented by EPTA-Gd in ER-positive cells as compared to ER-negative cells. Dynamic contrast-enhanced studies with EPTA-Gd in vivo indicated specific augmentation of the MRI water signal in the ER-positive versus ER-negative xenografts, confirming EPTA-Gd-specific interaction with ER. In contrast, TPTA-Gd did not show increased enhancement in ER-positive tumors and did not appear to interact in vivo with the tumors’ ER. However, TPTA-Gd was found to interact strongly with muscle tissue, enhancing muscle signal intensity in a mechanism independent of the presence of ER. The specificity of EPTA-Gd interaction with ER in vivo was further verified by acute and chronic competition with tamoxifen. The chronic tamoxifen treatment also revealed that this

  13. Novel molecularly imprinted magnetic nanoparticles for the selective extraction of protoberberine alkaloids in herbs and rat plasma.

    PubMed

    Meng, Jiawei; Zhang, Wenpeng; Bao, Tao; Chen, Zilin

    2015-06-01

    In this work, a novel magnetic nanomaterial functionalized with a molecularly imprinted polymer was prepared for the extraction of protoberberine alkaloids. Molecularly imprinted polymers were made on the surface of Fe3 O4 nanoparticles by using berberine as template, acetonitrile/water as porogen, acrylamide as functional monomer and ethylene glycol dimethacrylate as cross-linker. The optimized molar ratio of template/functional monomer was 1:7. The polymeric magnetic nanoparticles were characterized by transmission electron microscopy and Fourier transform infrared spectroscopy. The stability and adsorption capacity of the molecularly imprinted polymers were investigated. The molecularly imprinted polymers were used as a selective sorbent for the magnetic molecularly imprinted solid-phase extraction and determination of jatrorrhizine, palmatine, and berberine. Extraction parameters were studied including loading pH, sample volume, stirring speed, and extraction time. Finally, a magnetic molecularly imprinted solid-phase extraction coupled to high-performance liquid chromatography method was developed. Under the optimized conditions, the method showed good linear range of 0.1-150 ng/mL for berberine and 0.1-100 ng/mL for jatrorrhizine and palmatine. The limit of detection was 0.01 ng/mL for berberine and 0.02 ng/mL for jatrorrhizine and palmatine. The proposed method has been applied to determine protoberberine alkaloids in Cortex phellodendri and rat plasma samples. The recoveries ranged from 87.33-102.43%, with relative standard deviation less than 4.54% in Cortex phellodendri and from 102.22-111.15% with relative standard deviation less than 4.59% in plasma. PMID:25832420

  14. Low virial parameters in molecular clouds: Implications for high-mass star formation and magnetic fields

    SciTech Connect

    Kauffmann, Jens; Pillai, Thushara; Goldsmith, Paul F. E-mail: tpillai@astro.caltech.edu

    2013-12-20

    Whether or not molecular clouds and embedded cloud fragments are stable against collapse is of utmost importance for the study of the star formation process. Only 'supercritical' cloud fragments are able to collapse and form stars. The virial parameter α = M {sub vir}/M, which compares the virial mass to the actual mass, provides one way to gauge stability against collapse. Supercritical cloud fragments are characterized by α ≲ 2, as indicated by a comprehensive stability analysis considering perturbations in pressure and density gradients. Past research has suggested that virial parameters α ≳ 2 prevail in clouds. This would suggest that collapse toward star formation is a gradual and relatively slow process and that magnetic fields are not needed to explain the observed cloud structure. Here, we review a range of very recent observational studies that derive virial parameters <<2 and compile a catalog of 1325 virial parameter estimates. Low values of α are in particular observed for regions of high-mass star formation (HMSF). These observations may argue for a more rapid and violent evolution during collapse. This would enable 'competitive accretion' in HMSF, constrain some models of 'monolithic collapse', and might explain the absence of high-mass starless cores. Alternatively, the data could point at the presence of significant magnetic fields ∼1 mG at high gas densities. We examine to what extent the derived observational properties might be biased by observational or theoretical uncertainties. For a wide range of reasonable parameters, our conclusions appear to be robust with respect to such biases.

  15. Films Composed Of Diamond And Diamondlike Carbon

    NASA Technical Reports Server (NTRS)

    Shing, Yuh-Han

    1995-01-01

    Proposed films composed of diamond and diamondlike carbon useful as wear-resistant and self-lubricating protective and tribological coats at extreme temperatures and in corrosive and oxidizing environments. Films have wide variety of industrial applications.

  16. The Frontier of Molecular Spintronics Based on Multiple-Decker Phthalocyaninato Tb(III) Single-Molecule Magnets.

    PubMed

    Katoh, Keiichi; Komeda, Tadahiro; Yamashita, Masahiro

    2016-04-01

    Ever since the first example of a double-decker complex (SnPc2) was discovered in 1936, MPc2 complexes with π systems and chemical and physical stabilities have been used as components in molecular electronic devices. More recently, in 2003, TbPc2 complexes were shown to be single-molecule magnets (SMMs), and researchers have utilized their quantum tunneling of the magnetization (QTM) and magnetic relaxation behavior in spintronic devices. Herein, recent developments in Ln(III)-Pc-based multiple-decker SMMs on surfaces for molecular spintronic devices are presented. In this account, we discuss how dinuclear Tb(III)-Pc multiple-decker complexes can be used to elucidate the relationship between magnetic dipole interactions and SMM properties, because these complexes contain two TbPc2 units in one molecule and their intramolecular Tb(III)-Tb(III) distances can be controlled by changing the number of stacks. Next, we focus on the switching of the Kondo signal of Tb(III)-Pc-based multiple-decker SMMs that are adsorbed onto surfaces, their characterization using STM and STS, and the relationship between the molecular structure, the electronic structure, and the Kondo resonance of Tb(III)-Pc multiple-decker complexes. PMID:26991524

  17. Trapping cold molecules and atoms: Simultaneous magnetic deceleration and trapping of cold molecular Oxygen with Lithium atoms

    NASA Astrophysics Data System (ADS)

    Akerman, Nitzan; Karpov, Michael; Segev, Yair; Bibelink, Natan; Narevicius, Julia; Narevicius, Edvardas

    2016-05-01

    Cooling molecules to the ultra-cold regime remains a major challenge in the growing field of cold molecules. The molecular internal degrees of freedom complicate the effort of direct application of laser cooling. An alternative and general path towards ultra-cold molecules relies on sympathetic cooling via collisions with laser-cooled atoms. Here, we demonstrate the first step towards application of sympathetic cooling by co-trapping of molecular Oxygen with Lithium atoms in a magnetic trap at a temperature of 300 mK. Our experiment begins with a pulsed supersonic beam which is a general source for cold high-flux atomic and molecular beams. Although the supersonic expansion efficiently cools the beam to temperatures below 1K, it also accelerates the beam to high mean velocities. We decelerate a beam of O2 in a moving magnetic trap decelerator from 375 m/s to a stop. We entrained the molecular beam with Li atoms by laser ablation prior to deceleration. The deceleration ends with loading the molecules and atoms into a static quadrupole trap, which is generated by two permanent magnets. We estimate 109 trapped molecules with background limited lifetime of 0.6 Sec. Our achievement enables application of laser cooling on the Li atoms in order to sympathetically cool the O2.

  18. Probing the role of the magnetic field in the formation of structure in molecular clouds with Planck

    NASA Astrophysics Data System (ADS)

    Diego Soler, Juan

    2015-08-01

    The Planck observations of intensity and polarization of thermal emission from Galactic dust over the whole sky, and down to scales that probe the interiors of nearby molecular clouds, constitute an unprecedented data set for the study of the morphology of the magnetic field.Within ten nearby (d < 450 pc) Gould Belt molecular clouds we evaluate statistically the relative orientation between the magnetic field projected on the plane of sky, inferred from the polarized thermal emission of Galactic dust observed by Planck at 353 GHz, and the gas column density structures, quantified by the gradient of the column density, NH. The relative orientation is evaluated pixel by pixel and analyzed in bins of column density using the novel statistical tool called "Histogram of Relative Orientations".Within most clouds we find that the relative orientation changes progressively with increasing NH, from preferentially parallel or having no preferred orientation to preferentially perpendicular.In simulations of magnetohydrodynamic turbulence in molecular clouds this trend in relative orientation is a signature of Alfvénic or sub-Alfvénic turbulence, implying that the magnetic field is significant for the gas dynamics at the scales probed by Planck.We compare the deduced plane-of-the-sky magnetic field strength with estimates we obtain from the Davis-Chandrasekhar-Fermi method and with the line-of-sight magnetic field strengths derived from Zeeman splitting observations towards some of the studied regions.Finally, we discuss the implications of the Planck observations for the general picture of molecular cloud formation and evolution.This work is presented on behalf of the Planck Collaboration.

  19. Magnetic Resonance Spectroscopy and Imaging Guidance in Molecular Medicine: Targeting and Monitoring of Choline and Glucose Metabolism in Cancer

    PubMed Central

    Glunde, Kristine; Jiang, Lu; Moestue, Siver A.; Gribbestad, Ingrid S.

    2011-01-01

    Magnetic resonance spectroscopy (MRS) and spectroscopic imaging (MRSI) are valuable tools to detect metabolic changes in tumors. The currently emerging era of molecular medicine, which is shaped by molecularly targeted anticancer therapies combined with molecular imaging of the effects of such therapies, requires powerful imaging technologies that are able to detect molecular information. MRS and MRSI (MRS/I) are such technologies that are able to detect metabolites arising from glucose and choline metabolism in noninvasive in vivo settings and at higher resolution in tissue samples. The roles that MRS/I plays in diagnosing different types of cancer as well as in early monitoring of tumor response to traditional chemotherapies are reviewed. Emerging roles of MRS/I in the development and detection of novel targeted anticancer therapies that target oncogenic signaling pathways or targets in choline or glucose metabolism are discussed. PMID:21793073

  20. Magnetically-induced ferroelectricity in the (ND4)2[FeCl5(D2O)] molecular compound

    PubMed Central

    Alberto Rodríguez-Velamazán, José; Fabelo, Óscar; Millán, Ángel; Campo, Javier; Johnson, Roger D.; Chapon, Laurent

    2015-01-01

    The number of magnetoelectric multiferroic materials reported to date is scarce, as magnetic structures that break inversion symmetry and induce an improper ferroelectric polarization typically arise through subtle competition between different magnetic interactions. The (NH4)2[FeCl5(H2O)] compound is a rare case where such improper ferroelectricity has been observed in a molecular material. We have used single crystal and powder neutron diffraction to obtain detailed solutions for the crystal and magnetic structures of (NH4)2[FeCl5(H2O)], from which we determined the mechanism of multiferroicity. From the crystal structure analysis, we observed an order-disorder phase transition related to the ordering of the ammonium counterion. We have determined the magnetic structure below TN, at 2 K and zero magnetic field, which corresponds to a cycloidal spin arrangement with magnetic moments contained in the ac-plane, propagating parallel to the c-axis. The observed ferroelectricity can be explained, from the obtained magnetic structure, via the inverse Dzyaloshinskii-Moriya mechanism. PMID:26417890

  1. Phase transition between quantum and classical regimes for the escape rate of dimeric molecular nanomagnets in a staggered magnetic field

    NASA Astrophysics Data System (ADS)

    Owerre, S. A.; Paranjape, M. B.

    2014-04-01

    We study the phase transition of the escape rate of exchange-coupled dimer of single-molecule magnets which are coupled either ferromagnetically or antiferromagnetically in a staggered magnetic field and an easy z-axis anisotropy. The Hamiltonian for this system has been used to study dimeric molecular nanomagnet [Mn4]2 which is comprised of two single molecule magnets coupled antiferromagnetically. We generalize the method of mapping a single-molecule magnetic spin problem onto a quantum-mechanical particle to dimeric molecular nanomagnets. The problem is mapped to a single particle quantum-mechanical Hamiltonian in terms of the relative coordinate and a coordinate dependent reduced mass. It is shown that the presence of the external staggered magnetic field creates a phase boundary separating the first- from the second-order transition. With the set of parameters used by R. Tiron et al. (2003) [25] and S. Hill et al. (2003) [20] to fit experimental data for [Mn4]2 dimer we find that the critical temperature at the phase boundary is T0(c)=0.29K. Therefore, thermally activated transitions should occur for temperatures greater than T0(c).

  2. Magnetotransport in MgO-based magnetic tunnel junctions grown by molecular beam epitaxy (invited)

    SciTech Connect

    Andrieu, S. Bonell, F.; Hauet, T.; Montaigne, F.; Lefevre, P.; Bertran, F.

    2014-05-07

    The strong impact of molecular beam epitaxy growth and Synchrotron Radiation characterization tools in the understanding of fundamental issues in nanomagnetism and spintronics is illustrated through the example of fully epitaxial MgO-based Magnetic Tunnel Junctions (MTJs). If ab initio calculations predict very high tunnel magnetoresistance (TMR) in such devices, some discrepancy between theory and experiments still exists. The influence of imperfections in real systems has thus to be considered like surface contaminations, structural defects, unexpected electronic states, etc. The influence of possible oxygen contamination at the Fe/MgO(001) interface is thus studied, and is shown to be not so detrimental to TMR as predicted by ab initio calculations. On the contrary, the decrease of dislocations density in the MgO barrier of MTJs using Fe{sub 1−x}V{sub x} electrodes is shown to significantly increase TMR. Finally, unexpected transport properties in Fe{sub 1−X}Co{sub x}/MgO/Fe{sub 1−X}Co{sub x} (001) are presented. With the help of spin and symmetry resolved photoemission and ab initio calculation, the TMR decrease for Co content higher than 25% is shown to come from the existence of an interface state and the shift of the empty Δ1 minority spin state towards the Fermi level.

  3. Magnetic resonance-coupled fluorescence tomography scanner for molecular imaging of tissue.

    PubMed

    Davis, Scott C; Pogue, Brian W; Springett, Roger; Leussler, Christoph; Mazurkewitz, Peter; Tuttle, Stephen B; Gibbs-Strauss, Summer L; Jiang, Shudong S; Dehghani, Hamid; Paulsen, Keith D

    2008-06-01

    A multichannel spectrally resolved optical tomography system to image molecular targets in small animals from within a clinical MRI is described. Long source/detector fibers operate in contact mode and couple light from the tissue surface in the magnet bore to 16 spectrometers, each containing two optical gratings optimized for the near infrared wavelength range. High sensitivity, cooled charge coupled devices connected to each spectrograph provide detection of the spectrally resolved signal, with exposure times that are automated for acquisition at each fiber. The design allows spectral fitting of the remission light, thereby separating the fluorescence signal from the nonspecific background, which improves the accuracy and sensitivity when imaging low fluorophore concentrations. Images of fluorescence yield are recovered using a nonlinear reconstruction approach based on the diffusion approximation of photon propagation in tissue. The tissue morphology derived from the MR images serves as an imaging template to guide the optical reconstruction algorithm. Sensitivity studies show that recovered values of indocyanine green fluorescence yield are linear to concentrations of 1 nM in a 70 mm diameter homogeneous phantom, and detection is feasible to near 10 pM. Phantom data also demonstrate imaging capabilities of imperfect fluorophore uptake in tissue volumes of clinically relevant sizes. A unique rodent MR coil provides optical fiber access for simultaneous optical and MR data acquisition of small animals. A pilot murine study using an orthotopic glioma tumor model demonstrates optical-MRI imaging of an epidermal growth factor receptor targeted fluorescent probe in vivo. PMID:18601421

  4. Unmasking Silent Endothelial Activation in the Cardiovascular System Using Molecular Magnetic Resonance Imaging

    PubMed Central

    Belliere, Julie; Martinez de Lizarrondo, Sara; Choudhury, Robin P.; Quenault, Aurélien; Le Béhot, Audrey; Delage, Christine; Chauveau, Dominique; Schanstra, Joost P.; Bascands, Jean-Loup; Vivien, Denis; Gauberti, Maxime

    2015-01-01

    Endothelial activation is a hallmark of cardiovascular diseases, acting either as a cause or a consequence of organ injury. To date, we lack suitable methods to measure endothelial activation in vivo. In the present study, we developed a magnetic resonance imaging (MRI) method allowing non-invasive endothelial activation mapping in the vasculature of the main organs affected during cardiovascular diseases. In clinically relevant contexts in mice (including systemic inflammation, acute and chronic kidney diseases, diabetes mellitus and normal aging), we provided evidence that this method allows detecting endothelial activation before any clinical manifestation of organ failure in the brain, kidney and heart with an exceptional sensitivity. In particular, we demonstrated that diabetes mellitus induces chronic endothelial cells activation in the kidney and heart. Moreover, aged mice presented activated endothelial cells in the kidneys and the cerebrovasculature. Interestingly, depending on the underlying condition, the temporospatial patterns of endothelial activation in the vascular beds of the cardiovascular system were different. These results demonstrate the feasibility of detecting silent endothelial activation occurring in conditions associated with high cardiovascular risk using molecular MRI. PMID:26379785

  5. Preparation of a magnetic molecularly imprinted polymer for selective recognition of rhodamine B

    NASA Astrophysics Data System (ADS)

    Liu, Xiuying; Yu, Dan; Yu, Yingchao; Ji, Shujuan

    2014-11-01

    A novel magnetic molecularly imprinted polymer (MMIP) was developed as an adsorbent to selectively remove rhodamine B from real samples. The polymer was characterized by scanning electron microscopy, Fourier-transform infrared spectroscopy, and thermo-gravimetric analysis. Static adsorption, kinetic adsorption, and selective recognition experiments were also performed to investigate the specific adsorption equilibrium, kinetics, and selective recognition ability of the MMIP. The MMIPs had outstanding thermal stability, large adsorption capacity, and high competitive selectivity. When they were used as dispersed solid-phase extraction adsorbents in real samples, rhodamine B recovery was 79.97-81.88% and 75.56-79.74% in intra-day and inter-day reproducibility experiments with relative standard deviations lower than 2.62% and 4.28%, respectively. Extraction was optimized for yield and efficiency. Precision, accuracy, and linear working range were determined under optimal experimental conditions. The limits of detection and quantification were 1.05 and 3.49 μg L-1, respectively. These results suggest MMIPs may be used for determination of rhodamine B in real samples.

  6. Comparing implementations of magnetic-resonance-guided fluorescence molecular tomography for diagnostic classification of brain tumors

    NASA Astrophysics Data System (ADS)

    Davis, Scott C.; Samkoe, Kimberley S.; O'Hara, Julia A.; Gibbs-Strauss, Summer L.; Paulsen, Keith D.; Pogue, Brian W.

    2010-09-01

    Fluorescence molecular tomography (FMT) systems coupled to conventional imaging modalities such as magnetic resonance imaging (MRI) and computed tomography provide unique opportunities to combine data sets and improve image quality and content. Yet, the ideal approach to combine these complementary data is still not obvious. This preclinical study compares several methods for incorporating MRI spatial prior information into FMT imaging algorithms in the context of in vivo tissue diagnosis. Populations of mice inoculated with brain tumors that expressed either high or low levels of epidermal growth factor receptor (EGFR) were imaged using an EGF-bound near-infrared dye and a spectrometer-based MRI-FMT scanner. All data were spectrally unmixed to extract the dye fluorescence from the tissue autofluorescence. Methods to combine the two data sets were compared using student's t-tests and receiver operating characteristic analysis. Bulk fluorescence measurements that made up the optical imaging data set were also considered in the comparison. While most techniques were able to distinguish EGFR(+) tumors from EGFR(-) tumors and control animals, with area-under-the-curve values=1, only a handful were able to distinguish EGFR(-) tumors from controls. Bulk fluorescence spectroscopy techniques performed as well as most imaging techniques, suggesting that complex imaging algorithms may be unnecessary to diagnose EGFR status in these tissue volumes.

  7. Magnetotransport in MgO-based magnetic tunnel junctions grown by molecular beam epitaxy (invited)

    NASA Astrophysics Data System (ADS)

    Andrieu, S.; Bonell, F.; Hauet, T.; Montaigne, F.; Calmels, L.; Snoeck, E.; Lefevre, P.; Bertran, F.

    2014-05-01

    The strong impact of molecular beam epitaxy growth and Synchrotron Radiation characterization tools in the understanding of fundamental issues in nanomagnetism and spintronics is illustrated through the example of fully epitaxial MgO-based Magnetic Tunnel Junctions (MTJs). If ab initio calculations predict very high tunnel magnetoresistance (TMR) in such devices, some discrepancy between theory and experiments still exists. The influence of imperfections in real systems has thus to be considered like surface contaminations, structural defects, unexpected electronic states, etc. The influence of possible oxygen contamination at the Fe/MgO(001) interface is thus studied, and is shown to be not so detrimental to TMR as predicted by ab initio calculations. On the contrary, the decrease of dislocations density in the MgO barrier of MTJs using Fe1-xVx electrodes is shown to significantly increase TMR. Finally, unexpected transport properties in Fe1-XCox/MgO/Fe1-XCox (001) are presented. With the help of spin and symmetry resolved photoemission and ab initio calculation, the TMR decrease for Co content higher than 25% is shown to come from the existence of an interface state and the shift of the empty Δ1 minority spin state towards the Fermi level.

  8. Magnetic Resonance Imaging to Detect Early Molecular and Cellular Changes in Alzheimer's Disease.

    PubMed

    Knight, Michael J; McCann, Bryony; Kauppinen, Risto A; Coulthard, Elizabeth J

    2016-01-01

    Recent pharmaceutical trials have demonstrated that slowing or reversing pathology in Alzheimer's disease is likely to be possible only in the earliest stages of disease, perhaps even before significant symptoms develop. Pathology in Alzheimer's disease accumulates for well over a decade before symptoms are detected giving a large potential window of opportunity for intervention. It is therefore important that imaging techniques detect subtle changes in brain tissue before significant macroscopic brain atrophy. Current diagnostic techniques often do not permit early diagnosis or are too expensive for routine clinical use. Magnetic Resonance Imaging (MRI) is the most versatile, affordable, and powerful imaging modality currently available, being able to deliver detailed analyses of anatomy, tissue volumes, and tissue state. In this mini-review, we consider how MRI might detect patients at risk of future dementia in the early stages of pathological change when symptoms are mild. We consider the contributions made by the various modalities of MRI (structural, diffusion, perfusion, relaxometry) in identifying not just atrophy (a late-stage AD symptom) but more subtle changes reflective of early dementia pathology. The sensitivity of MRI not just to gross anatomy but to the underlying "health" at the cellular (and even molecular) scales, makes it very well suited to this task. PMID:27378911

  9. Magnetic resonance-coupled fluorescence tomography scanner for molecular imaging of tissue

    NASA Astrophysics Data System (ADS)

    Davis, Scott C.; Pogue, Brian W.; Springett, Roger; Leussler, Christoph; Mazurkewitz, Peter; Tuttle, Stephen B.; Gibbs-Strauss, Summer L.; Jiang, Shudong S.; Dehghani, Hamid; Paulsen, Keith D.

    2008-06-01

    A multichannel spectrally resolved optical tomography system to image molecular targets in small animals from within a clinical MRI is described. Long source/detector fibers operate in contact mode and couple light from the tissue surface in the magnet bore to 16 spectrometers, each containing two optical gratings optimized for the near infrared wavelength range. High sensitivity, cooled charge coupled devices connected to each spectrograph provide detection of the spectrally resolved signal, with exposure times that are automated for acquisition at each fiber. The design allows spectral fitting of the remission light, thereby separating the fluorescence signal from the nonspecific background, which improves the accuracy and sensitivity when imaging low fluorophore concentrations. Images of fluorescence yield are recovered using a nonlinear reconstruction approach based on the diffusion approximation of photon propagation in tissue. The tissue morphology derived from the MR images serves as an imaging template to guide the optical reconstruction algorithm. Sensitivity studies show that recovered values of indocyanine green fluorescence yield are linear to concentrations of 1nM in a 70mm diameter homogeneous phantom, and detection is feasible to near 10pM. Phantom data also demonstrate imaging capabilities of imperfect fluorophore uptake in tissue volumes of clinically relevant sizes. A unique rodent MR coil provides optical fiber access for simultaneous optical and MR data acquisition of small animals. A pilot murine study using an orthotopic glioma tumor model demonstrates optical-MRI imaging of an epidermal growth factor receptor targeted fluorescent probe in vivo.

  10. Molecular beam epitaxy growth and magnetic properties of Cr-Co-Ga Heusler alloy films

    SciTech Connect

    Feng, Wuwei Wang, Weihua; Zhao, Chenglong; Van Quang, Nguyen; Cho, Sunglae; Dung, Dang Duc

    2015-11-15

    We have re-investigated growth and magnetic properties of Cr{sub 2}CoGa films using molecular beam epitaxy technique. Phase separation and precipitate formation were observed experimentally again in agreement with observation of multiple phases separation in sputtered Cr{sub 2}CoGa films by M. Meinert et al. However, significant phase separation could be suppressed by proper control of growth conditions. We showed that Cr{sub 2}CoGa Heusler phase, rather than Co{sub 2}CrGa phase, constitutes the majority of the sample grown on GaAs(001) at 450 {sup o}C. The measured small spin moment of Cr{sub 2}CoGa is in agreement with predicted HM-FCF nature; however, its Curie temperature is not as high as expected from the theoretical prediction probably due to the off-stoichiometry of Cr{sub 2}CoGa and the existence of the disorders and phase separation.

  11. Sorption of carbamazepine from water by magnetic molecularly imprinted polymers based on chitosan-Fe₃O₄.

    PubMed

    Zhang, Ya-Lei; Zhang, Juan; Dai, Chao-Meng; Zhou, Xue-Fei; Liu, Shu-Guang

    2013-09-12

    A novel magnetic-molecularly imprinted polymer (MMIP) based on chitosan-Fe₃O₄ has been synthesized for fast separation of carbamazepine (CBZ) from water. During polymerization, the modified chitosan-Fe₃O₄ was used not only as supporter but also as functional monomer. The properties of obtained MMIP were characterized by scanning electron and transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectra, thermo-gravimetric analysis and so on. The sorption equilibrium data was well described by Freundlich isotherm model and the increase in the temperature generated an increase in the sorption amount, indicating endothermic nature of adsorption process. Sorption kinetics followed the pseudo-second-order model. The feasibility of selective sorption of CBZ from real water by the MMIP was analyzed by using spiked real water samples. The result showed that the sorption capacity of MMIP has no obvious decrease in different water samples whereas there was obvious decline in the sorption amount of the MNIP. PMID:23911519

  12. Growth and magnetic property of antiperovskite manganese nitride films doped with Cu by molecular beam epitaxy

    SciTech Connect

    Yu, Fengmei; Ren, Lizhu; Meng, Meng; Wang, Yunjia; Yang, Mei; Wu, Shuxiang; Li, Shuwei

    2014-04-07

    Manganese nitrides thin films on MgO (100) substrates with and without Cu-doping have been fabricated by plasma assisted molecular beam epitaxy. Antiperovskite compounds Mn{sub 3.6}Cu{sub 0.4}N have been grown in the case of Cu-doping, and the pure Mn{sub 3}N{sub 2} single crystal has been obtained without Cu-doping. The Mn{sub 3.6}Cu{sub 0.4}N exhibits ferrimagnetism, and the magnetization of Mn{sub 3.6}Cu{sub 0.4}N increases upon the temperature decreasing from 300 K to 5 K, similar to Mn{sub 4}N. The exchange bias (EB) effects emerge in the Mn{sub 3.6}Cu{sub 0.4}N films. The EB behavior is originated from the interfaces between ferrimagnetic Mn{sub 3.6}Cu{sub 0.4}N and antiferromagnetic metal Mn, which is verified to be formed by the data of x-ray photoelectron spectroscopy. The present results not only provide a strategy for producing functional antiperovskite manganese nitrides, but also shed promising light on fabricating the exchange bias part of spintronic devices.

  13. Cotunneling signatures of spin-electric coupling in frustrated triangular molecular magnets

    NASA Astrophysics Data System (ADS)

    Nossa, J. F.; Canali, C. M.

    2014-06-01

    The ground state of frustrated (antiferromagnetic) triangular molecular magnets is characterized by two total-spin S =1/2 doublets with opposite chirality. According to a group theory analysis [M. Trif et al., Phys. Rev. Lett. 101, 217201 (2008), 10.1103/PhysRevLett.101.217201], an external electric field can efficiently couple these two chiral spin states, even when the spin-orbit interaction (SOI) is absent. The strength of this coupling, d, is determined by an off-diagonal matrix element of the dipole operator, which can be calculated by ab initio methods [M. F. Islam et al., Phys. Rev. B 82, 155446 (2010), 10.1103/PhysRevB.82.155446]. In this work, we propose that Coulomb-blockade transport experiments in the cotunneling regime can provide a direct way to determine the spin-electric coupling strength. Indeed, an electric field generates a d-dependent splitting of the ground-state manifold, which can be detected in the inelastic cotunneling conductance. Our theoretical analysis is supported by master-equation calculations of quantum transport in the cotunneling regime. We employ a Hubbard-model approach to elucidate the relationship between the Hubbard parameters t and U, and the spin-electric coupling constant d. This allows us to predict the regime in which the coupling constant d can be extracted from experiment.

  14. Magnetic Resonance Imaging to Detect Early Molecular and Cellular Changes in Alzheimer's Disease

    PubMed Central

    Knight, Michael J.; McCann, Bryony; Kauppinen, Risto A.; Coulthard, Elizabeth J.

    2016-01-01

    Recent pharmaceutical trials have demonstrated that slowing or reversing pathology in Alzheimer's disease is likely to be possible only in the earliest stages of disease, perhaps even before significant symptoms develop. Pathology in Alzheimer's disease accumulates for well over a decade before symptoms are detected giving a large potential window of opportunity for intervention. It is therefore important that imaging techniques detect subtle changes in brain tissue before significant macroscopic brain atrophy. Current diagnostic techniques often do not permit early diagnosis or are too expensive for routine clinical use. Magnetic Resonance Imaging (MRI) is the most versatile, affordable, and powerful imaging modality currently available, being able to deliver detailed analyses of anatomy, tissue volumes, and tissue state. In this mini-review, we consider how MRI might detect patients at risk of future dementia in the early stages of pathological change when symptoms are mild. We consider the contributions made by the various modalities of MRI (structural, diffusion, perfusion, relaxometry) in identifying not just atrophy (a late-stage AD symptom) but more subtle changes reflective of early dementia pathology. The sensitivity of MRI not just to gross anatomy but to the underlying “health” at the cellular (and even molecular) scales, makes it very well suited to this task. PMID:27378911

  15. Unmasking Silent Endothelial Activation in the Cardiovascular System Using Molecular Magnetic Resonance Imaging.

    PubMed

    Belliere, Julie; Martinez de Lizarrondo, Sara; Choudhury, Robin P; Quenault, Aurélien; Le Béhot, Audrey; Delage, Christine; Chauveau, Dominique; Schanstra, Joost P; Bascands, Jean-Loup; Vivien, Denis; Gauberti, Maxime

    2015-01-01

    Endothelial activation is a hallmark of cardiovascular diseases, acting either as a cause or a consequence of organ injury. To date, we lack suitable methods to measure endothelial activation in vivo. In the present study, we developed a magnetic resonance imaging (MRI) method allowing non-invasive endothelial activation mapping in the vasculature of the main organs affected during cardiovascular diseases. In clinically relevant contexts in mice (including systemic inflammation, acute and chronic kidney diseases, diabetes mellitus and normal aging), we provided evidence that this method allows detecting endothelial activation before any clinical manifestation of organ failure in the brain, kidney and heart with an exceptional sensitivity. In particular, we demonstrated that diabetes mellitus induces chronic endothelial cells activation in the kidney and heart. Moreover, aged mice presented activated endothelial cells in the kidneys and the cerebrovasculature. Interestingly, depending on the underlying condition, the temporospatial patterns of endothelial activation in the vascular beds of the cardiovascular system were different. These results demonstrate the feasibility of detecting silent endothelial activation occurring in conditions associated with high cardiovascular risk using molecular MRI. PMID:26379785

  16. (GaMn)As: GaAs-based III?V diluted magnetic semiconductors grown by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Hayashi, T.; Tanaka, M.; Nishinaga, T.; Shimada, H.; Tsuchiya, H.; Otuka, Y.

    1997-05-01

    We have grown novel III-V diluted magnetic semiconductors, (Ga 1 - xMn x)As, on GaAs substrates by low-temperature molecular beam epitaxy using strong nonequilibrium growth conditions. When the Mn concentration x is relatively low (≲0.08), homogeneous alloy semiconductors, GaMnAs, are grown with zincblende structure and slightly larger lattice constants than that of GaAs, whereas inhomogeneous structures with zincblende GaMnAs (or GaAs) plus hexagonal MnAs are formed when x is relatively high. Magnetization measurements indicate that the homogeneous GaMnAs films have ferromagnetic ordering at low temperature.

  17. Long lifetimes of high molecular Rydberg states in crossed magnetic and electric fields: An experimental and classical computational study

    NASA Astrophysics Data System (ADS)

    Mühlpfordt, Annette; Even, U.; Rabani, Eran; Levine, R. D.

    1995-05-01

    Crossed magnetic and electric fields are observed to extend the lifetime of high molecular Rydberg states of DABCO (1,4-Diazabicyclo[2.2.2]octane) well into the microsecond range. The experimental and computational (using classical mechanics and for a diatomic polar core) results agree both on the magnitude of the effect and on its decrease with increasing electrical field. Theoretical considerations suggest that this time-stretching effect is only present for high Rydberg states and/or for not too weak fields. The computed lifetime increases as the magnetic-field strength is decreased but it requires a finite magnetic field for the onset of the effect. The experimental technique of detection of the surviving Rydberg states via their ionization in a delayed field pulse (known as ZEKE spectroscopy) is most easily implemented for high (say, n>100) but not too high (n<400) Rydberg states. In this regime, the magnetic field required for the additional time stretching is larger than that due to the earth but can be significantly weaker than that required to induce extensive chaotic behavior. The results of the numerically exact classical simulations are interpreted using equations of motion, cast in the form of a mapping, which retain terms up to second order in the fields. (The first-order terms are qualitatively and quantitatively not, by themselves, sufficient.) As is to be expected on physical grounds, the origin of the effect is the slow, periodic modulation of the magnitude of the magnetic quantum number ml of the electron due to terms second order in the magnetic field. Since the angular momentum l of the electron is bounded from below by ml, and since it requires a low l for the electron to couple effectively to the molecular core, the presence of the magnetic field provides for an elongation of the time scale which is over and above that made possible due to the periodic motion of l due to the dc electric field.

  18. Preparation of molecularly imprinted polymers based on magnetic nanoparticles for the selective extraction of protocatechuic acid from plant extracts.

    PubMed

    Xie, Xiaoyu; Wei, Fen; Chen, Liang; Wang, Sicen

    2015-03-01

    In this study, highly selective core-shell molecularly imprinted polymers on the surface of magnetic nanoparticles were prepared using protocatechuic acid as the template molecule. The resulting magnetic molecularly imprinted polymers were characterized by transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and vibrating sample magnetometry. The binding performances of the prepared materials were evaluated by static and selective adsorption. The binding isotherms were obtained for protocatechuic acid and fitted by the Langmuir isotherm model and Freundlich isotherm model. Furthermore, the resulting materials were used as the solid-phase extraction materials coupled to high-performance liquid chromatography for the selective extraction and detection of protocatechuic acid from the extracts of Homalomena occulta and Cynomorium songaricum with the recoveries in the range 86.3-102.2%. PMID:25641806

  19. Magnetic molecularly imprinted polymer for the selective extraction of sildenafil, vardenafil and their analogs from herbal medicines.

    PubMed

    Chen, Fang-Fang; Xie, Xiao-Yu; Shi, Yan-Ping

    2013-10-15

    The successfully developed magnetic molecularly imprinted polymers (MMIPs) toward six synthetic phosphodiesterase type-5 (PDE-5) inhibitors were described. Sildenafil was used as template for the preparation of MMIPs using superparamagnetic core-shell nanoparticle as supporter. The obtained MMIPs were characterized using transmission electron microscope, Fourier transform infrared, X-ray diffraction, and vibrating sample magnetometer. High performance liquid chromatography (HPLC) with diode array detector (DAD) was used for the analysis of target analytes. The application of MMIPs as selective sorbent in the cleanup of herbal medicine samples prior to HPLC offered simple sample preparation. The adsorption capacity and selectivity of prepared MMIPs and magnetic non-molecularly imprinted polymers were investigated. The binding isotherms were obtained for sildenafil and fitted by Freundlich isotherm model. Structurally similar compound of sildenafil and a reference compound protocatechuic acid were used for investing the selective recognition of MMIPs. PMID:24054622

  20. Optical sensing of phenylalanine in urine via extraction with magnetic molecularly imprinted poly(ethylene-co-vinyl alcohol) nanoparticles

    NASA Astrophysics Data System (ADS)

    Hsu, Chung-Yi; Lee, Mei-Hwa; Thomas, James L.; Shih, Ching-Ping; Hung, Tzu-Lin; Whang, Thou-Jen; Lin, Hung-Yin

    2015-07-01

    Incorporation of superparamagnetic nanoparticles into molecularly imprinted polymers (MIPs) is useful for both bioseparations and for concentration and sensing of biomedically relevant target molecules in physiological fluids, through the application of a magnetic field. In this study, we combined the separation and concentration of a target (phenylalanine) in urine, using magnetic molecularly imprinted polymeric composite nanoparticles, with optical sensing, to improve assay sensitivity. This target is important as a catecholamine precursor, and as an important amino acid constituent of proteins. Poly(ethylene-co-vinyl alcohol)s were imprinted with target molecules, and showed a high imprinting effectiveness (target binding compared with binding to non-imprinted polymer particles.) Fluorescence spectrophotometry was used to measure binding of the target, and also binding of possible interfering compounds. These measurements suggest that functional groups on phenylalanine dominate the selectivity of the synthesized MIPs. Finally, the composite nanoparticles were used to separate and sense the target molecule in urine by Raman scattering microscopy.

  1. On the alignment of Classical T Tauri stars with the magnetic field in the Taurus-Auriga molecular cloud

    NASA Astrophysics Data System (ADS)

    Ménard, F.; Duchêne, G.

    2004-10-01

    In this paper we readdress the issue of the alignment of Classical T Tauri stars (CTTS) with the magnetic field in the Taurus-Auriga molecular cloud. Previous studies have claimed that the jet axis of active young stellar objects (YSO), projected in the plane of the sky, is aligned preferentially along the projected direction of the local magnetic field. We re-examine this issue in view of the numerous high angular resolution images of circumstellar disks and micro-jets now available. The images show that T Tauri stars as a group are oriented randomly with respect to the local magnetic field, contrary to previous claims. This indicates that the magnetic field may play a lesser role in the final stages of collapse of an individual prestellar core than previously envisioned. The current database also suggests that a subsample of CTTS with resolved disks but without observations of bright and extended outflows have a tendency to align perpendicularly to the magnetic field. We discuss the possibility that this may trace a less favorable topology, e.g., quadrupolar, for the magnetic field in the inner disk, resulting in a weaker collimated outflow.

  2. Planck intermediate results. XXXV. Probing the role of the magnetic field in the formation of structure in molecular clouds

    NASA Astrophysics Data System (ADS)

    Planck Collaboration; Ade, P. A. R.; Aghanim, N.; Alves, M. I. R.; Arnaud, M.; Arzoumanian, D.; Ashdown, M.; Aumont, J.; Baccigalupi, C.; Banday, A. J.; Barreiro, R. B.; Bartolo, N.; Battaner, E.; Benabed, K.; Benoît, A.; Benoit-Lévy, A.; Bernard, J.-P.; Bersanelli, M.; Bielewicz, P.; Bock, J. J.; Bonavera, L.; Bond, J. R.; Borrill, J.; Bouchet, F. R.; Boulanger, F.; Bracco, A.; Burigana, C.; Calabrese, E.; Cardoso, J.-F.; Catalano, A.; Chiang, H. C.; Christensen, P. R.; Colombo, L. P. L.; Combet, C.; Couchot, F.; Crill, B. P.; Curto, A.; Cuttaia, F.; Danese, L.; Davies, R. D.; Davis, R. J.; de Bernardis, P.; de Rosa, A.; de Zotti, G.; Delabrouille, J.; Dickinson, C.; Diego, J. M.; Dole, H.; Donzelli, S.; Doré, O.; Douspis, M.; Ducout, A.; Dupac, X.; Efstathiou, G.; Elsner, F.; Enßlin, T. A.; Eriksen, H. K.; Falceta-Gonçalves, D.; Falgarone, E.; Ferrière, K.; Finelli, F.; Forni, O.; Frailis, M.; Fraisse, A. A.; Franceschi, E.; Frejsel, A.; Galeotta, S.; Galli, S.; Ganga, K.; Ghosh, T.; Giard, M.; Gjerløw, E.; González-Nuevo, J.; Górski, K. M.; Gregorio, A.; Gruppuso, A.; Gudmundsson, J. E.; Guillet, V.; Harrison, D. L.; Helou, G.; Hennebelle, P.; Henrot-Versillé, S.; Hernández-Monteagudo, C.; Herranz, D.; Hildebrandt, S. R.; Hivon, E.; Holmes, W. A.; Hornstrup, A.; Huffenberger, K. M.; Hurier, G.; Jaffe, A. H.; Jaffe, T. R.; Jones, W. C.; Juvela, M.; Keihänen, E.; Keskitalo, R.; Kisner, T. S.; Knoche, J.; Kunz, M.; Kurki-Suonio, H.; Lagache, G.; Lamarre, J.-M.; Lasenby, A.; Lattanzi, M.; Lawrence, C. R.; Leonardi, R.; Levrier, F.; Liguori, M.; Lilje, P. B.; Linden-Vørnle, M.; López-Caniego, M.; Lubin, P. M.; Macías-Pérez, J. F.; Maino, D.; Mandolesi, N.; Mangilli, A.; Maris, M.; Martin, P. G.; Martínez-González, E.; Masi, S.; Matarrese, S.; Melchiorri, A.; Mendes, L.; Mennella, A.; Migliaccio, M.; Miville-Deschênes, M.-A.; Moneti, A.; Montier, L.; Morgante, G.; Mortlock, D.; Munshi, D.; Murphy, J. A.; Naselsky, P.; Nati, F.; Netterfield, C. B.; Noviello, F.; Novikov, D.; Novikov, I.; Oppermann, N.; Oxborrow, C. A.; Pagano, L.; Pajot, F.; Paladini, R.; Paoletti, D.; Pasian, F.; Perotto, L.; Pettorino, V.; Piacentini, F.; Piat, M.; Pierpaoli, E.; Pietrobon, D.; Plaszczynski, S.; Pointecouteau, E.; Polenta, G.; Ponthieu, N.; Pratt, G. W.; Prunet, S.; Puget, J.-L.; Rachen, J. P.; Reinecke, M.; Remazeilles, M.; Renault, C.; Renzi, A.; Ristorcelli, I.; Rocha, G.; Rossetti, M.; Roudier, G.; Rubiño-Martín, J. A.; Rusholme, B.; Sandri, M.; Santos, D.; Savelainen, M.; Savini, G.; Scott, D.; Soler, J. D.; Stolyarov, V.; Sudiwala, R.; Sutton, D.; Suur-Uski, A.-S.; Sygnet, J.-F.; Tauber, J. A.; Terenzi, L.; Toffolatti, L.; Tomasi, M.; Tristram, M.; Tucci, M.; Umana, G.; Valenziano, L.; Valiviita, J.; Van Tent, B.; Vielva, P.; Villa, F.; Wade, L. A.; Wandelt, B. D.; Wehus, I. K.; Ysard, N.; Yvon, D.; Zonca, A.

    2016-02-01

    Within ten nearby (d < 450 pc) Gould belt molecular clouds we evaluate statistically the relative orientation between the magnetic field projected on the plane of sky, inferred from the polarized thermal emission of Galactic dust observed by Planck at 353 GHz, and the gas column density structures, quantified by the gradient of the column density, NH. The selected regions, covering several degrees in size, are analysed at an effective angular resolution of 10' FWHM, thus sampling physical scales from 0.4 to 40 pc in the nearest cloud. The column densities in the selected regions range from NH≈ 1021 to1023 cm-2, and hence they correspond to the bulk of the molecular clouds. The relative orientation is evaluated pixel by pixel and analysed in bins of column density using the novel statistical tool called "histogram of relative orientations". Throughout this study, we assume that the polarized emission observed by Planck at 353 GHz is representative of the projected morphology of the magnetic field in each region, i.e., we assume a constant dust grain alignment efficiency, independent of the local environment. Within most clouds we find that the relative orientation changes progressively with increasing NH, from mostly parallel or having no preferred orientation to mostly perpendicular. In simulations of magnetohydrodynamic turbulence in molecular clouds this trend in relative orientation is a signature of Alfvénic or sub-Alfvénic turbulence, implying that the magnetic field is significant for the gas dynamics at the scales probed by Planck. We compare the deduced magnetic field strength with estimates we obtain from other methods and discuss the implications of the Planck observations for the general picture of molecular cloud formation and evolution.

  3. Cotton-mouton effects, magnetic hyperpolarizabilities, and magnetic anisotropies of the methyl halides. Comparison with molecular Zeeman and high-field NMR spectroscopic results

    SciTech Connect

    Coonan, M.H.; Ritchie, G.L.D. )

    1991-02-07

    Measurements of the vapor-phase Cotton-Mouton effects of methyl fluoride, methyl bromide, and methyl iodide are reported. Analysis of the results, in conjunction with those of an earlier study of methane and methyl chloride, shows that in the series CH{sub 3}X (X = H, F, Cl, Br, I) the magnetic hyperpolarizabiity anisotropy, which is related to the quadratic response of the molecular polarizability to a magnetic field, is positive in sign and roughly proportional in magnitude to the mean polarizability. The magnetic anisotropies (10{sup 29}{Delta}{sub {chi}}/J T{sup {minus}2}) found for methyl chloride,methyl bromide, and methyl iodide (CH{sub 3}Cl, {minus}15.0 {plus minus} 1.3; CH{sub 3}Br, -15.1 {plus minus} 0.8; CH{sub 3}I, {minus}18.0 {plus minus} 1.5) are compared with values obtained by the molecular Zeeman and high-field {sup 2}H NMR spectroscopic methods.

  4. Music and emotion—a composer's perspective

    PubMed Central

    Douek, Joel

    2013-01-01

    This article takes an experiential and anecdotal look at the daily lives and work of film composers as creators of music. It endeavors to work backwards from what practitioners of the art and craft of music do instinctively or unconsciously, and try to shine a light on it as a conscious process. It examines the role of the film composer in his task to convey an often complex set of emotions, and communicate with an immediacy and universality that often sit outside of common language. Through the experiences of the author, as well as interviews with composer colleagues, this explores both concrete and abstract ways in which music can bring meaning and magic to words and images, and as an underscore to our daily lives. PMID:24348344

  5. Rectenna composed of a circular microstrip antenna

    SciTech Connect

    Itoh, K.; Ohgane, T.; Ogawa, Y.

    1986-01-01

    One of the big problems in the SPS system is reradiation of the harmonic waves generated by the rectifying diode. The authors proposed the use of a circular microstrip antenna (CMSA), since the CMSA has no higher resonance-harmonic of integer multiple of the dominant resonance frequency. However, characteristics of a large rectenna array of CMSA's have not been clarified. This paper is concerned with the absorption efficiency of the rectenna composed of the CMSA. The efficiency is estimated explicitly using an infinite array model. The results show that the absorption efficiency of the infinite rectenna array composed of the CMSA is 100%. Also, this paper considers the effect of the losses of the composed of the CMSA is 100%. Also, this paper considers the effect of the losses of the CMSA. 4 references, 4 figures.

  6. Molecular dynamics simulation of the nematic liquid crystal phase in the presence of an intense magnetic field.

    PubMed

    Satoh, Katsuhiko

    2006-04-14

    The influence of an intense external field on the dynamics of the nematic liquid crystal phase is investigated using a molecular dynamics simulation for the Gay-Berne nematogen under isobaric-isothermal conditions. The molecular dynamics as a function of the second-rank orientational order parameter P<2> for a system consisting of a nematic liquid crystal in the presence of an intense magnetic field is compared with that of a similar system without the field. The translational motion of molecules is determined as a function of the translational diffusion coefficient tensor and the anisotropy and compared with the values predicted theoretically. The rotational dynamics of molecules is analyzed using the first- and the second-rank orientational time correlation functions. The translational diffusion coefficient parallel with respect to the director is constrained by the intense field, although the perpendicular one is decreased as the P<2> is increased, just as it is in the system without the field. However, no essential effect of the strong magnetic field is observed in the rotational molecular dynamics. Further, the rotational diffusion coefficient parallel with respect to the director obtained from the first-rank orientational time correlation function in the simulation is qualitatively in agreement with that in the real nematic liquid crystalline molecules. The P<2> dependence of the rotational diffusion coefficient for the system with the intense magnetic field shows a tendency similar to that for the system without the field. PMID:16626239

  7. Molecular dynamics simulation of the nematic liquid crystal phase in the presence of an intense magnetic field

    NASA Astrophysics Data System (ADS)

    Satoh, Katsuhiko

    2006-04-01

    The influence of an intense external field on the dynamics of the nematic liquid crystal phase is investigated using a molecular dynamics simulation for the Gay-Berne nematogen under isobaric-isothermal conditions. The molecular dynamics as a function of the second-rank orientational order parameter ⟨P2⟩ for a system consisting of a nematic liquid crystal in the presence of an intense magnetic field is compared with that of a similar system without the field. The translational motion of molecules is determined as a function of the translational diffusion coefficient tensor and the anisotropy and compared with the values predicted theoretically. The rotational dynamics of molecules is analyzed using the first- and the second-rank orientational time correlation functions. The translational diffusion coefficient parallel with respect to the director is constrained by the intense field, although the perpendicular one is decreased as the ⟨P2⟩ is increased, just as it is in the system without the field. However, no essential effect of the strong magnetic field is observed in the rotational molecular dynamics. Further, the rotational diffusion coefficient parallel with respect to the director obtained from the first-rank orientational time correlation function in the simulation is qualitatively in agreement with that in the real nematic liquid crystalline molecules. The ⟨P2⟩ dependence of the rotational diffusion coefficient for the system with the intense magnetic field shows a tendency similar to that for the system without the field.

  8. A core-shell surface magnetic molecularly imprinted polymers with fluorescence for λ-cyhalothrin selective recognition.

    PubMed

    Gao, Lin; Wang, Jixiang; Li, Xiuying; Yan, Yongsheng; Li, Chunxiang; Pan, Jianming

    2014-11-01

    In this study, we report here a general protocol for making core-shell magnetic Fe3O4/SiO2-MPS/MIPs (MPS = 3-(methacryloxyl) propyl trimethoxysilane, MIPs = molecularly imprinted polymers, Fe3O4/SiO2-MPS as core, MIPs as shell) via a surface molecular imprinting technique for optical detection of trace λ-cyhalothrin. The fluorescent molecularly imprinted polymer shell was first prepared by copolymerization of acrylamide with a small quantity of allyl fluorescein in the presence of λ-cyhalothrin to form recognition sites without doping. The magnetic Fe3O4/SiO2-MPS/MIPs exhibited paramagnetism, high fluorescence intensity, and highly selective recognition. Using fluorescence quenching as a detecting tool, Fe3O4/SiO2-MPS/MIPs were successfully applied to selectively and sensitively detect λ-cyhalothrin, and a linear relationship could be obtained covering a wide concentration range of 0-50 nM with a correlation coefficient of 0.9962 described by the Stern-Volmer equation. The experimental results of practical detection revealed that magnetic Fe3O4/SiO2-MPS/MIPs as an attractive recognition element was satisfactory for determination of trace λ-cyhalothrin in honey samples. This study, therefore, demonstrated the potential of MIPs for detection of λ-cyhalothrin in food. PMID:25200071

  9. Large Orbital Magnetic Moment Measured in the [TpFe(III)(CN)3](-) Precursor of Photomagnetic Molecular Prussian Blue Analogues.

    PubMed

    Jafri, Sadaf Fatima; Koumousi, Evangelia S; Sainctavit, Philippe; Juhin, Amélie; Schuler, Vivien; Bun U, Oana; Mitcov, Dmitri; Dechambenoit, Pierre; Mathonière, Corine; Clérac, Rodolphe; Otero, Edwige; Ohresser, Philippe; Cartier Dit Moulin, Christophe; Arrio, Marie-Anne

    2016-07-18

    Photomagnetism in three-dimensional Co/Fe Prussian blue analogues is a complex phenomenon, whose detailed mechanism is not yet fully understood. Recently, researchers have been able to prepare molecular fragments of these networks using a building block synthetic approach from mononuclear precursors. The main objective in this strategy is to isolate the smallest units that show an intramolecular electron transfer to have a better understanding of the electronic processes. A prior requirement to the development of this kind of system is to understand to what extent electronic and magnetic properties are inherited from the corresponding precursors. In this work, we investigate the electronic and magnetic properties of the FeTp precursor (N(C4H9)4)[TpFe(III)(CN)3], (Tp being tris-pyrazolyl borate) of a recently reported binuclear cyanido-bridged Fe/Co complex. X-ray absorption spectroscopy and X-ray magnetic circular dichroism measurements at the Fe L2,3 edges (2p → 3d) supported by ligand field multiplet calculations have allowed to determine the spin and orbit magnetic moments. Inaccuracy of the spin sum rule in the case of low-spin Fe(III) ion was demonstrated. An exceptionally large value of the orbital magnetic moment is found (0.9 μB at T = 2 K and B = 6.5 T) that is likely to play an important role in the magnetic and photomagnetic properties of molecular Fe/Co Prussian blue analogues. PMID:27385292

  10. Structural and Magnetic Phase Transitions in Manganese Arsenide Thin-Films Grown by Molecular Beam Epitaxy

    NASA Astrophysics Data System (ADS)

    Jaeckel, Felix Till

    Phase transitions play an important role in many fields of physics and engineering, and their study in bulk materials has a long tradition. Many of the experimental techniques involve measurements of thermodynamically extensive parameters. With the increasing technological importance of thin-film technology there is a pressing need to find new ways to study phase transitions at smaller length-scales, where the traditional methods are insufficient. In this regard, the phase transitions observed in thin-films of MnAs present interesting challenges. As a ferromagnetic material that can be grown epitaxially on a variety of technologically important substrates, MnAs is an interesting material for spintronics applications. In the bulk, the first order transition from the low temperature ferromagnetic alpha-phase to the beta-phase occurs at 313 K. The magnetic state of the beta-phase has remained controversial. A second order transition to the paramagnetic gamma-phase takes place at 398 K. In thin-films, the anisotropic strain imposed by the substrate leads to the interesting phenomenon of coexistence of alpha- and beta-phases in a regular array of stripes over an extended temperature range. In this dissertation these phase transitions are studied in films grown by molecular beam epitaxy on GaAs (001). The films are confirmed to be of high structural quality and almost purely in the A0 orientation. A diverse set of experimental techniques, germane to thin-film technology, is used to probe the properties of the film: Temperature-dependent X-ray diffraction and atomic-force microscopy (AFM), as well as magnetotransport give insights into the structural properties, while the anomalous Hall effect is used as a probe of magnetization during the phase transition. In addition, reflectance difference spectroscopy (RDS) is used as a sensitive probe of electronic structure. Inductively coupled plasma etching with BCl3 is demonstrated to be effective for patterning MnAs. We show

  11. Molecular interactions between green tea catechins and cheese fat studied by solid-state nuclear magnetic resonance spectroscopy.

    PubMed

    Rashidinejad, Ali; Birch, Edward J; Hindmarsh, Jason; Everett, David W

    2017-01-15

    Molecular integrations between green tea catechins and milk fat globules in a cheese matrix were investigated using solid-state magic angle spinning nuclear magnetic resonance spectroscopy. Full-fat cheeses were manufactured containing free catechin or free green tea extract (GTE), and liposomal encapsulated catechin or liposomal encapsulated GTE. Molecular mobility of the carbon species in the cheeses was measured by a wide-line separation technique. The (1)H evolution frequency profile of the (13)C peak at 16ppm obtained for the control cheese and cheeses containing encapsulated polyphenols (catechin or GTE) were similar, however, the spectrum was narrower for cheeses containing free polyphenols. Differences in spectral width indicates changes in the molecular mobility of --CH3- or -C-C-PO4- species through hydrophobic and/or cation-π associations between green tea catechins and cheese fat components. However, the similar spectral profile suggests that encapsulation protects cheese fat from interaction with catechins. PMID:27542471

  12. The Brain Functional State of Music Creation: an fMRI Study of Composers.

    PubMed

    Lu, Jing; Yang, Hua; Zhang, Xingxing; He, Hui; Luo, Cheng; Yao, Dezhong

    2015-01-01

    In this study, we used functional magnetic resonance imaging (fMRI) to explore the functional networks in professional composers during the creation of music. We compared the composing state and resting state imagery of 17 composers and found that the functional connectivity of primary networks in the bilateral occipital lobe and bilateral postcentral cortex decreased during the composing period. However, significantly stronger functional connectivity appeared between the anterior cingulate cortex (ACC), the right angular gyrus and the bilateral superior frontal gyrus during composition. These findings indicate that a specific brain state of musical creation is formed when professional composers are composing, in which the integration of the primary visual and motor areas is not necessary. Instead, the neurons of these areas are recruited to enhance the functional connectivity between the ACC and the default mode network (DMN) to plan the integration of musical notes with emotion. PMID:26203921

  13. The Brain Functional State of Music Creation: an fMRI Study of Composers

    PubMed Central

    Lu, Jing; Yang, Hua; Zhang, Xingxing; He, Hui; Luo, Cheng; Yao, Dezhong

    2015-01-01

    In this study, we used functional magnetic resonance imaging (fMRI) to explore the functional networks in professional composers during the creation of music. We compared the composing state and resting state imagery of 17 composers and found that the functional connectivity of primary networks in the bilateral occipital lobe and bilateral postcentral cortex decreased during the composing period. However, significantly stronger functional connectivity appeared between the anterior cingulate cortex (ACC), the right angular gyrus and the bilateral superior frontal gyrus during composition. These findings indicate that a specific brain state of musical creation is formed when professional composers are composing, in which the integration of the primary visual and motor areas is not necessary. Instead, the neurons of these areas are recruited to enhance the functional connectivity between the ACC and the default mode network (DMN) to plan the integration of musical notes with emotion. PMID:26203921

  14. Structural and magnetic properties of Prussian blue analogue molecular magnet Fe1.5[Cr(CN)6].mH2O

    NASA Astrophysics Data System (ADS)

    Bhatt, Pramod; Meena, S. S.; Mukadam, M. D.; Yusuf, S. M.

    2016-05-01

    Molecular magnets, based on Prussian blue analogues, Fe1.5[Cr(CN)6].mH2O have been synthesized in the bulk as well as nanoparticle forms using a co-precipitation method, and their structural and magnetic properties have been investigated using x-ray diffraction (XRD) Mössbauer spectroscopy and dc magnetization. The XRD study confirms the single phase crystalline and nanoparticle nature of the compounds with a face centered cubic (fcc) structure of space group Fm3m. The values of lattice constant are found to be ~10.18(5) Å and ~9.98(9)Å, for the bulk and nanoparticle samples, respectively. The dc magnetization shows a Curie temperature (TC) of ~17 K and ~5 K for the bulk and nanopartcile samples, respectively. The Mossouber spectroscopy reveal that the compound shows spin flipping from the high spin (HS) Fe (CrIII-C≡N-FeII) to low spin (LS) FeII ions (CrIII-N≡C-FeII). Moreover, the TC and the HS state of the Fe ions decreases (converts to its LS states) with time as well as in the nanoparticle form compared to bulk.

  15. Solar cells composed of semiconductive materials

    SciTech Connect

    Hezel, R.

    1981-03-03

    A solar cell is composed of a semiconductive material having an active zone in which charge carriers are produced by photons which strike and penetrate into the solar cell. The cell is comprised of a semiconductive body having an electrically insulating laminate with metal contacts therein positioned on the semiconductor body in the active zone thereof. The insulating laminate is composed of a double layer of insulating material, with the layer in direct contact with the semiconductive surface being composed of SiO2 which is either natural or is produced at temperatures below 800/sup 0/ C. And the layer superimposed above the SiO2 layer being composed of a different insulating material, such as plasma-produced Si3N4. In certain embodiments of the invention, a whole-area pn-junction is provided parallel to the semiconductive surface. The solar cells of the invention exhibit a higher degree of efficiency due to a higher fixed interface charged density, and low surface recombination velocity, an increased UV sensitivity, improved surface protection and passivation and improved anti-reflection characteristics relative to prior art solar cell devices.

  16. Take a Change with Aleatory Composing.

    ERIC Educational Resources Information Center

    Stambaugh, Laura

    2003-01-01

    Discusses how teachers can incorporate musical composition into their classrooms by teaching students about aleatory, or chance, music. Provides a definition of aleatory music and provides various composing techniques, focusing on aleatory music. Includes lesson plans using aleatory music, such as the "Mozart Model" for grades 4-12. (CMK)

  17. The Composer in the Liberal Arts College

    ERIC Educational Resources Information Center

    Schwartz, Elliott

    2011-01-01

    This essay explores the role of music composition within the curriculum of a typical small liberal arts college and the faculty composer's role(s) in facilitating the study of composition. The relationship between composition and campus performance is discussed, particularly in light of the increased emphasis on performance in formerly all-male…

  18. Composing for Digital Publication: Rhetoric, Design, Code

    ERIC Educational Resources Information Center

    Eyman, Douglas; Ball, Cheryl E.

    2014-01-01

    The authors discuss the state of digital publication with the claim that, at this historical moment, nearly all composition is digital composition. But, as a field, composition studies has not yet made that shift completely explicit in the discussions of composing processes and writing pedagogies. A deeper engagement with this very rapid shift in…

  19. The Composer's Blueprint: A Teacher's Guide.

    ERIC Educational Resources Information Center

    Trzcinski, Louis C.; Nelhybel, Vaclav

    This teacher's guide is designed to accompany two 15-minute color television programs dealing with the creative process involved in conceiving a composition. The programs are appropriate for junior high school string students and instrumental students in string methods courses at teacher training institutions. In the program, the composer explains…

  20. Prospects for composability of models and simulations

    NASA Astrophysics Data System (ADS)

    Davis, Paul K.; Anderson, Robert B.

    2004-08-01

    This paper is the summary of a recent RAND study done at the request of the U.S. Defense Modeling and Simulation Office (DMSO). Commissioned in recognition that the last decade's efforts by DoD to achieve model "composability" have had only limited success (e.g., HLA-mediated exercises), and that fundamental problems remain, the study surveyed the underlying problems that make composability difficult. It then went on to recommend a series of improvement measures for DMSO and other DoD offices to consider. One strong recommendation was that DoD back away from an earlier tendency toward overselling composability, moving instead to a more particularized approach in which composability is sought within domains where it makes most sense substantively. Another recommendation was that DoD needs to recognize the shortcomings of standard software-engineering paradigms when dealing with "models" rather than pure software. Beyond this, the study had concrete recommendations dealing with science and technology, the base of human capital, management, and infrastructure. Many recommendations involved the need to align more closely with cutting edge technology and emerging standards in the private sector.

  1. Mathematical Approaches to the Composing Process.

    ERIC Educational Resources Information Center

    Hall, Dennis R.

    Rhetoric and mathematics have much in common that can help explain the composing process. Common elements of rhetoric and mathematics important to the teaching of writing are (1) relationships between syntax and semantics, (2) practices of representation, and (3) focus on problem solving. Recent emphasis on "repair processes" in mathematics is…

  2. COLLAPSE AND FRAGMENTATION OF MAGNETIC MOLECULAR CLOUD CORES WITH THE ENZO AMR MHD CODE. I. UNIFORM DENSITY SPHERES

    SciTech Connect

    Boss, Alan P.; Keiser, Sandra A.

    2013-02-20

    Magnetic fields are important contributors to the dynamics of collapsing molecular cloud cores, and can have a major effect on whether collapse results in a single protostar or fragmentation into a binary or multiple protostar system. New models are presented of the collapse of magnetic cloud cores using the adaptive mesh refinement code Enzo2.0. The code was used to calculate the ideal magnetohydrodynamics (MHD) of initially spherical, uniform density, and rotation clouds with density perturbations, i.e., the Boss and Bodenheimer standard isothermal test case for three-dimensional (3D) hydrodynamics codes. After first verifying that Enzo reproduces the binary fragmentation expected for the non-magnetic test case, a large set of models was computed with varied initial magnetic field strengths and directions with respect to the cloud core axis of rotation (parallel or perpendicular), density perturbation amplitudes, and equations of state. Three significantly different outcomes resulted: (1) contraction without sustained collapse, forming a denser cloud core; (2) collapse to form a single protostar with significant spiral arms; and (3) collapse and fragmentation into binary or multiple protostar systems, with multiple spiral arms. Comparisons are also made with previous MHD calculations of similar clouds with a barotropic equations of state. These results for the collapse of initially uniform density spheres illustrate the central importance of both magnetic field direction and field strength for determining the outcome of dynamic protostellar collapse.

  3. Magnetic sensing film based on Fe₃O₄@Au-GSH molecularly imprinted polymers for the electrochemical detection of estradiol.

    PubMed

    Han, Qing; Shen, Xin; Zhu, Wanying; Zhu, Chunhong; Zhou, Xuemin; Jiang, Huijun

    2016-05-15

    A novel magnetic molecularly imprinted sensing film (MMISF) was fabricated for the determination of estradiol (E2) based on magnetic glassy carbon electrode (MGCE) and magnetic molecularly imprinted polymers (MMIPs). The MMIPs were synthesized by in situ polymerization of glutathione (GSH)-functionalized gold (Au)-coated Fe3O4 (Fe3O4@Au-GSH) nanocomposites and aniline. The MMISF was constructed with MMIPs via a kind of "soft modification" where MMIPs were assembled and immobilized on the surface of MGCE or removed from it by freely installing a magnet into MGCE or not. The E2-MMIPs were obtained by MMIPs recognizing E2 from sample, and the electrochemical detection was carried out after forming the "soft modification" sensing film by putting MGCE into the E2-MMIPs suspension liquid. Afterwards, the "soft modification" MMISF was peeled off from the electrode by removing the magnet from MGCE. The interface of the electrode could be quickly refreshed through simple treatment for the next detection. The structures and morphologies of Fe3O4@Au-GSH, MMIPs and MMISF were investigated by Fourier transform infrared spectrometer, ultraviolet and visible spectrophotometer, scanning electron microscope and atomic force microscope. In addition, the MMISF was successfully used for detecting E2 in milk powder with good sensitivity, selectivity, reproducibility and efficiency. The linear range of the MMISF for E2 was 0.025-10.0μmolL(-1) with the limit of detection of 2.76nmolL(-1) (S/N= 3). PMID:26706939

  4. Spin-communication channels between Ln(III) bis-phthalocyanines molecular nanomagnets and a magnetic substrate

    NASA Astrophysics Data System (ADS)

    Candini, A.; Klar, D.; Marocchi, S.; Corradini, V.; Biagi, R.; de Renzi, V.; Del Pennino, U.; Troiani, F.; Bellini, V.; Klyatskaya, S.; Ruben, M.; Kummer, K.; Brookes, N. B.; Huang, H.; Soncini, A.; Wende, H.; Affronte, M.

    2016-02-01

    Learning the art of exploiting the interplay between different units at the atomic scale is a fundamental step in the realization of functional nano-architectures and interfaces. In this context, understanding and controlling the magnetic coupling between molecular centers and their environment is still a challenging task. Here we present a combined experimental-theoretical work on the prototypical case of the bis(phthalocyaninato)-lanthanide(III) (LnPc2) molecular nanomagnets magnetically coupled to a Ni substrate. By means of X-ray magnetic circular dichroism we show how the coupling strength can be tuned by changing the Ln ion. The microscopic parameters of the system are determined by ab-initio calculations and then used in a spin Hamiltonian approach to interpret the experimental data. By this combined approach we identify the features of the spin communication channel: the spin path is first realized by the mediation of the external (5d) electrons of the Ln ion, keeping the characteristic features of the inner 4 f orbitals unaffected, then through the organic ligand, acting as a bridge to the external world.

  5. Experimental cell for molecular beam deposition and magnetic resonance studies of matrix isolated radicals at temperatures below 1 K

    SciTech Connect

    Sheludiakov, S. Ahokas, J.; Vainio, O.; Järvinen, J.; Zvezdov, D.; Vasiliev, S.; Khmelenko, V. V.; Mao, S.; Lee, D. M.

    2014-05-15

    We present the design and performance of an experimental cell constructed for matrix isolation studies of H and D atoms in solid H{sub 2}/D{sub 2} films, which are created by molecular beam deposition at temperatures below 1 K. The sample cell allows sensitive weighing of the films by a quartz microbalance (QM) and their studies by magnetic resonance techniques in a strong magnetic field of 4.6 T. We are able to regulate the deposition rate in the range from 0.01 to 10 molecular layers/s, and measure the thickness with ≈0.2 monolayer resolution. The upper QM electrode serves as a mirror for a 128 GHz Fabry-Perot resonator connected to an electron spin resonance (ESR) spectrometer. H and D atoms were created by RF discharge in situ in the sample cell, and characterized by ESR and electron-nuclear double resonance. From the magnetic resonance measurements we conclude that the films are smooth and provide homogeneous trapping conditions for embedded atoms. The current sample cell design also makes it possible to calibrate the ESR signal and estimate the average and local concentrations of H and D radicals in the film.

  6. Spin-communication channels between Ln(III) bis-phthalocyanines molecular nanomagnets and a magnetic substrate

    PubMed Central

    Candini, A.; Klar, D.; Marocchi, S.; Corradini, V.; Biagi, R.; De Renzi, V.; del Pennino, U.; Troiani, F.; Bellini, V.; Klyatskaya, S.; Ruben, M.; Kummer, K.; Brookes, N. B.; Huang, H.; Soncini, A.; Wende, H.; Affronte, M.

    2016-01-01

    Learning the art of exploiting the interplay between different units at the atomic scale is a fundamental step in the realization of functional nano-architectures and interfaces. In this context, understanding and controlling the magnetic coupling between molecular centers and their environment is still a challenging task. Here we present a combined experimental-theoretical work on the prototypical case of the bis(phthalocyaninato)-lanthanide(III) (LnPc2) molecular nanomagnets magnetically coupled to a Ni substrate. By means of X-ray magnetic circular dichroism we show how the coupling strength can be tuned by changing the Ln ion. The microscopic parameters of the system are determined by ab-initio calculations and then used in a spin Hamiltonian approach to interpret the experimental data. By this combined approach we identify the features of the spin communication channel: the spin path is first realized by the mediation of the external (5d) electrons of the Ln ion, keeping the characteristic features of the inner 4 f orbitals unaffected, then through the organic ligand, acting as a bridge to the external world. PMID:26907811

  7. Spin-communication channels between Ln(III) bis-phthalocyanines molecular nanomagnets and a magnetic substrate.

    PubMed

    Candini, A; Klar, D; Marocchi, S; Corradini, V; Biagi, R; De Renzi, V; Del Pennino, U; Troiani, F; Bellini, V; Klyatskaya, S; Ruben, M; Kummer, K; Brookes, N B; Huang, H; Soncini, A; Wende, H; Affronte, M

    2016-01-01

    Learning the art of exploiting the interplay between different units at the atomic scale is a fundamental step in the realization of functional nano-architectures and interfaces. In this context, understanding and controlling the magnetic coupling between molecular centers and their environment is still a challenging task. Here we present a combined experimental-theoretical work on the prototypical case of the bis(phthalocyaninato)-lanthanide(III) (LnPc2) molecular nanomagnets magnetically coupled to a Ni substrate. By means of X-ray magnetic circular dichroism we show how the coupling strength can be tuned by changing the Ln ion. The microscopic parameters of the system are determined by ab-initio calculations and then used in a spin Hamiltonian approach to interpret the experimental data. By this combined approach we identify the features of the spin communication channel: the spin path is first realized by the mediation of the external (5d) electrons of the Ln ion, keeping the characteristic features of the inner 4 f orbitals unaffected, then through the organic ligand, acting as a bridge to the external world. PMID:26907811

  8. Probing molecular geometry of solids by nuclear magnetic resonance spin exchange at the n=0 rotational-resonance condition

    NASA Astrophysics Data System (ADS)

    Tekely, Piotr; Gardiennet, Carole; Potrzebowski, Marek J.; Sebald, Angelika; Reichert, Detlef; Luz, Zeev

    2002-05-01

    Exploration of the molecular geometry in rotating powder solids on the basis of magnetization exchange between spins with identical isotropic chemical shifts but differing chemical shielding tensor orientations is demonstrated experimentally. For this we take advantage of the potential of the ODESSA (one-dimensional exchange spectroscopy by sidebands alternation) experiment for the accurate measurement of spin exchange rate constants. We also report the observation of oscillatory behavior of the rotor-driven magnetization exchange at this so-called n=0 rotational-resonance condition which, in contrast to n=1,2,3,… rotational-resonance conditions, takes place at nearly arbitrary magic-angle spinning frequencies. The sensitivity of the longitudinal exchange decays to the relevant physical parameters of the spin system under conditions of rotor-driven and proton-driven magnetization exchange is discussed theoretically and demonstrated experimentally. Several 13C and 31P spin-exchange measurements have been performed on a series of model compounds covering a broad range of internuclear distances between carboxyl carbon atoms, and on a series of phosphorylated amino acids with different internuclear distances between phosphorus sites. The capacity of the ODESSA experiment for an unambiguous recognition of distinct internuclear distances is demonstrated. Potential applications of such measurements involve the exploration of intermolecular distances and the determination of the mutual orientation of neighboring molecular fragments in polycrystalline and noncrystalline solids.

  9. Is the Higgs boson composed of neutrinos?

    SciTech Connect

    Krog, Jens; Hill, Christopher T.

    2015-11-09

    We show that conventional Higgs compositeness conditions can be achieved by the running of large Higgs-Yukawa couplings involving right-handed neutrinos that become active at ~1013–1014 GeV. Together with a somewhat enhanced quartic coupling arising by a Higgs portal interaction to a dark matter sector, we can obtain a Higgs boson composed of neutrinos. Furthermore, this is a “next-to-minimal” dynamical electroweak symmetry breaking scheme.

  10. Is the Higgs boson composed of neutrinos?

    DOE PAGESBeta

    Krog, Jens; Hill, Christopher T.

    2015-11-09

    We show that conventional Higgs compositeness conditions can be achieved by the running of large Higgs-Yukawa couplings involving right-handed neutrinos that become active at ~1013–1014 GeV. Together with a somewhat enhanced quartic coupling arising by a Higgs portal interaction to a dark matter sector, we can obtain a Higgs boson composed of neutrinos. Furthermore, this is a “next-to-minimal” dynamical electroweak symmetry breaking scheme.

  11. Radiogenomic analysis of breast cancer: dynamic contrast enhanced - magnetic resonance imaging based features are associated with molecular subtypes

    NASA Astrophysics Data System (ADS)

    Wang, Shijian; Fan, Ming; Zhang, Juan; Zheng, Bin; Wang, Xiaojia; Li, Lihua

    2016-03-01

    Breast cancer is one of the most common malignant tumor with upgrading incidence in females. The key to decrease the mortality is early diagnosis and reasonable treatment. Molecular classification could provide better insights into patient-directed therapy and prognosis prediction of breast cancer. It is known that different molecular subtypes have different characteristics in magnetic resonance imaging (MRI) examination. Therefore, we assumed that imaging features can reflect molecular information in breast cancer. In this study, we investigated associations between dynamic contrasts enhanced MRI (DCE-MRI) features and molecular subtypes in breast cancer. Sixty patients with breast cancer were enrolled and the MR images were pre-processed for noise reduction, registration and segmentation. Sixty-five dimensional imaging features including statistical characteristics, morphology, texture and dynamic enhancement in breast lesion and background regions were semiautomatically extracted. The associations between imaging features and molecular subtypes were assessed by using statistical analyses, including univariate logistic regression and multivariate logistic regression. The results of multivariate regression showed that imaging features are significantly associated with molecular subtypes of Luminal A (p=0.00473), HER2-enriched (p=0.00277) and Basal like (p=0.0117), respectively. The results indicated that three molecular subtypes are correlated with DCE-MRI features in breast cancer. Specifically, patients with a higher level of compactness or lower level of skewness in breast lesion are more likely to be Luminal A subtype. Besides, the higher value of the dynamic enhancement at T1 time in normal side reflect higher possibility of HER2-enriched subtype in breast cancer.

  12. Au(III)-promoted magnetic molecularly imprinted polymer nanospheres for electrochemical determination of streptomycin residues in food.

    PubMed

    Liu, Bingqian; Tang, Dianping; Zhang, Bing; Que, Xiaohua; Yang, Huanghao; Chen, Guonan

    2013-03-15

    Redox-active magnetic molecularly imprinted polymer (mMIP) nanospheres were first synthesized and functionalized with streptomycin templates for highly efficient electrochemical determination of streptomycin residues (STR) in food by coupling with bioelectrocatalytic reaction of enzymes for signal amplification. The mMIP nanospheres were synthesized by using Au(III)-promoted molecularly imprinted polymerization with STR templates on magnetic beads. Based on extraction of template molecules from the mMIP surface, the imprints toward STR templates were formed. The assay was implemented with a competitive-type assay format. Upon addition of streptomycin, the analyte competed with glucose oxidase-labeled streptomycin (GOX-STR) for molecular imprints on the mMIP nanospheres. With the increasing streptomycin in the sample, the conjugation amount of GOX-STR on the mMIP nanospheres decreased, leading to the change in the bioelectrocatalytic current relative to glucose system. Under optimal conditions, the catalytic current was proportional to STR level in the sample, and exhibited a dynamic range of 0.05-20 ng mL(-1) with a detection limit of 10 pg mL(-1) STR (at 3s(B)). Intra- and inter-assay coefficients of variation were below 12%. The assayed results for STR spiked samples including milk and honey with the mMIP-based sensor were received a good accordance with the results obtained from the referenced high-performance liquid chromatography (HPLC) method. PMID:23058661

  13. The Influence of Conceptions of Molecular Structure and Patterns of Problem-Solving on the Process of Learning To Interpret Nuclear Magnetic Resonance Spectra.

    ERIC Educational Resources Information Center

    Gonzalez, Barbara L.

    The purpose of this study was to characterize the prior conceptions of molecular structure that organic chemistry students expressed as they learned to interpret nuclear magnetic resonance spectra, and to describe the problem-solving strategies that students employ as they determine molecular structure. The two questions that frame this study…

  14. Aptamer-modified magnetic nanoprobe for molecular MR imaging of VEGFR2 on angiogenic vasculature

    NASA Astrophysics Data System (ADS)

    Kim, Bongjune; Yang, Jaemoon; Hwang, Myeonghwan; Choi, Jihye; Kim, Hyun-Ouk; Jang, Eunji; Lee, Jung Hwan; Ryu, Sung-Ho; Suh, Jin-Suck; Huh, Yong-Min; Haam, Seungjoo

    2013-09-01

    Nucleic acid-based aptamers have been developed for the specific delivery of diagnostic nanoprobes. Here, we introduce a new class of smart imaging nanoprobe, which is based on hybridization of a magnetic nanocrystal with a specific aptamer for specific detection of the angiogenic vasculature of glioblastoma via magnetic resonance (MR) imaging. The magnetic nanocrystal imaging core was synthesized using the thermal decomposition method and enveloped by carboxyl polysorbate 80 for water solubilization and conjugation of the targeting moiety. Subsequently, the surface of the carboxylated magnetic nanocrystal was modified with amine-functionalized aptamers that specifically bind to the vascular growth factor receptor 2 (VEGFR2) that is overexpressed on angiogenic vessels. To assess the targeted imaging potential of the aptamer-conjugated magnetic nanocrystal for VEGFR2 markers, the magnetic properties and MR imaging sensitivity were investigated using the orthotopic glioblastoma mouse model. In in vivo tests, the aptamer-conjugated magnetic nanocrystal effectively targeted VEGFR2 and demonstrated excellent MR imaging sensitivity with no cytotoxicity.

  15. A Simple Demonstration of Atomic and Molecular Orbitals Using Circular Magnets

    ERIC Educational Resources Information Center

    Chakraborty, Maharudra; Mukhopadhyay, Subrata; Das, Ranendu Sekhar

    2014-01-01

    A quite simple and inexpensive technique is described here to represent the approximate shapes of atomic orbitals and the molecular orbitals formed by them following the principles of the linear combination of atomic orbitals (LCAO) method. Molecular orbitals of a few simple molecules can also be pictorially represented. Instructors can employ the…

  16. Structural and magnetic characterization of Sm-doped GaN grown by plasma-assisted molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Dehara, Kentaro; Miyazaki, Yuta; Hasegawa, Shigehiko

    2016-05-01

    We have investigated structural, optical and magnetic properties of Sm-doped GaN thin films grown by plasma-assisted molecular beam epitaxy. Reflection high-energy electron diffraction and X-ray diffraction reveal that Ga1- x Sm x N films with a SmN mole fraction of ˜8% or below are grown on GaN templates without segregation of any secondary phases. With increasing SmN mole fraction, the c-axis lattice parameter of the GaSmN films linearly increases. GaSmN films with low Sm concentrations exhibit inner-4f transitions of Sm3+ in photoluminescence spectra. The present findings show that Sm atoms are substituted for some Ga atoms as trivalent ions (Sm3+). The Ga1- x Sm x N films display hysteresis loops in magnetization versus external magnetic field (M-H) curves even at 300 K. We will discuss the origin of these features together with the corresponding temperature dependences of magnetization.

  17. Liquid state DNP at high magnetic fields: Instrumentation, experimental results and atomistic modelling by molecular dynamics simulations.

    PubMed

    Prisner, Thomas; Denysenkov, Vasyl; Sezer, Deniz

    2016-03-01

    Dynamic nuclear polarization (DNP) at high magnetic fields has recently become one of the major research areas in magnetic resonance spectroscopy and imaging. Whereas much work has been devoted to experiments where the polarization transfer from the electron spin to the nuclear spin is performed in the solid state, only a few examples exist of experiments where the polarization transfer is performed in the liquid state. Here we describe such experiments at a magnetic field of 9.2 T, corresponding to a nuclear Larmor frequency of 400 MHz for proton spins and an excitation frequency of 263 GHz for the electron spins. The technical requirements to perform such experiments are discussed in the context of the double resonance structures that we have implemented. The experimental steps that allowed access to the enhancement factors for proton spins of several organic solvents with nitroxide radicals as polarizing agents are described. A computational scheme for calculating the coupling factors from molecular dynamics (MD) simulations is outlined and used to highlight the limitations of the classical models based on translational and rotational motion that are typically employed to quantify the observed coupling factors. The ability of MD simulations to predict enhancements for a variety of radicals and solvent molecules at any magnetic field strength should prove useful in optimizing experimental conditions for DNP in the liquid state. PMID:26920832

  18. Liquid state DNP at high magnetic fields: Instrumentation, experimental results and atomistic modelling by molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Prisner, Thomas; Denysenkov, Vasyl; Sezer, Deniz

    2016-03-01

    Dynamic nuclear polarization (DNP) at high magnetic fields has recently become one of the major research areas in magnetic resonance spectroscopy and imaging. Whereas much work has been devoted to experiments where the polarization transfer from the electron spin to the nuclear spin is performed in the solid state, only a few examples exist of experiments where the polarization transfer is performed in the liquid state. Here we describe such experiments at a magnetic field of 9.2 T, corresponding to a nuclear Larmor frequency of 400 MHz for proton spins and an excitation frequency of 263 GHz for the electron spins. The technical requirements to perform such experiments are discussed in the context of the double resonance structures that we have implemented. The experimental steps that allowed access to the enhancement factors for proton spins of several organic solvents with nitroxide radicals as polarizing agents are described. A computational scheme for calculating the coupling factors from molecular dynamics (MD) simulations is outlined and used to highlight the limitations of the classical models based on translational and rotational motion that are typically employed to quantify the observed coupling factors. The ability of MD simulations to predict enhancements for a variety of radicals and solvent molecules at any magnetic field strength should prove useful in optimizing experimental conditions for DNP in the liquid state.

  19. Improvement of extraction capability of magnetic molecularly imprinted polymer beads in aqueous media via dual-phase solvent system.

    PubMed

    Hu, Yuling; Liu, Ruijin; Zhang, Yi; Li, Gongke

    2009-08-15

    In this study, a novel and simple dual-phase solvent system for the improvement of extraction capability of magnetic molecularly imprinted polymer (MIP) beads in aqueous sample was proposed. The method integrated MIP extraction and micro-liquid-liquid extraction (micro-LLE) into only one step. A magnetic MIP beads using atrazine as template was synthesized, and was applied to aqueous media by adding micro-volume of n-hexane to form a co-extraction system. The magnetic MIP beads preferred to suspend in the organic phase, which shielded them from the disturbance of water molecule. The target analytes in the water sample was extracted into the organic phase by micro-LLE and then further bound to the solid-phase of magnetic MIP beads. The beads specificity was significantly improved with the imprinting efficiency of template increasing from 0.5 to 4.4, as compared with that in pure aqueous media. The extraction capacity, equilibration process and cross-selectivity of the MIP dual-phase solvent extraction system were investigated. The proposed method coupled with high-performance liquid chromatography was applied to the analysis of atrazine, simazine, propazine, simetryn, prometryne, ametryn and terbutryn in complicated sample such as tomato, strawberry juice and milk. The method is selective, sensitive and low organic solvent-consuming, and has potential to broaden the range of MIP application in biological and environmental sample. PMID:19576415

  20. Water-compatible temperature and magnetic dual-responsive molecularly imprinted polymers for recognition and extraction of bisphenol A.

    PubMed

    Wu, Xiaqing; Wang, Xiaoyan; Lu, Wenhui; Wang, Xinran; Li, Jinhua; You, Huiyan; Xiong, Hua; Chen, Lingxin

    2016-02-26

    Versatile molecularly imprinted polymers (MIPs) have been widely applied to various sample matrices, however, molecular recognition in aqueous media is still difficult. Stimuli-responsive MIPs have received increasing attentions due to their unique feature that the molecular recognition is regulated by specific external stimuli. Herein, water-compatible temperature and magnetic dual-responsive MIPs (WC-TMMIPs) with hydrophilic brushes were prepared via reversible addition-fragmentation chain transfer precipitation polymerization for reversible and selective recognition and extraction of bisphenol A (BPA). Transmission electron microscopy (TEM), Fourier transform infrared spectrometer (FT-IR) and vibrating sample magnetometry (VSM) as characterization methods were used to examine the successful synthesis of polymers, and the resultant WC-TMMIPs showed excellent thermosensitivity and simple rapid magnetic separation. Controlled adsorption and release of BPA by temperature regulation were investigated systematically, and the maximum adsorption and removal efficiency toward BPA in aqueous solutions were attained at 35 °C and 45 °C, respectively, as well as a good recoverability was exhibited with the precision less than 5% through five adsorption-desorption cycles. Phenolic structural analogs were tested and good recognition specificity for BPA was displayed. Accordingly, the WC-TMMIPs were employed as adsorbents for magnetic solid-phase extraction (MSPE) and packed SPE of BPA from seawater samples. Using the two modes followed by HPLC-UV determination, excellent linearity was attained in the range of 0.1-14.5 μM and 1.3-125 nM, with low detection limits of 0.02 μM and 0.18 nM, respectively. Satisfactory recoveries for spiked seawater samples were achieved ranging from 86.3-103.5% and 96.2-104.3% with RSD within 2.12-4.33%. The intelligent WC-TMMIPs combining water-compatibility, molecular recognition, magnetic separation, and temperature regulation proved

  1. Highly-oriented molecular arrangements and enhanced magnetic interactions in thin films of CoTTDPz using PTCDA templates.

    PubMed

    Eguchi, Keitaro; Nanjo, Chihiro; Awaga, Kunio; Tseng, Hsiang-Han; Robaschik, Peter; Heutz, Sandrine

    2016-07-14

    In the present work, the templating effect of thin layers of perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) on the growth of cobalt tetrakis(thiadiazole)porphyrazine (CoTTDPz) thin films was examined. X-ray diffraction and optical absorption spectra indicate that while CoTTDPz forms amorphous thin films on the bare substrates, it forms crystalline thin films on the PTCDA templates, in which the molecular planes of CoTTDPz are considered to be parallel to the substrates. Magnetic measurements reveal a significantly enhanced antiferromagnetic interaction of CoTTDPz in the templated thin films, with values reaching over 13 K. The ability to generate crystalline films and to control their orientation using molecular templates is an important strategy in the fields of organic electronics and spintronics in order to tailor the physical properties of organic thin films to suit their intended application. PMID:27183955

  2. Molecular and Integrative Physiological Effects of Isoflurane Anesthesia: The Paradigm of Cardiovascular Studies in Rodents using Magnetic Resonance Imaging

    PubMed Central

    Constantinides, Christakis; Murphy, Kathy

    2016-01-01

    To-this-date, the exact molecular, cellular, and integrative physiological mechanisms of anesthesia remain largely unknown. Published evidence indicates that anesthetic effects are multifocal and occur in a time-dependent and coordinated manner, mediated via central, local, and peripheral pathways. Their effects can be modulated by a range of variables, and their elicited end-effect on the integrative physiological response is highly variable. This review summarizes the major cellular and molecular sites of anesthetic action with a focus on the paradigm of isoflurane (ISO) – the most commonly used anesthetic nowadays – and its use in prolonged in vivo rodent studies using imaging modalities, such as magnetic resonance imaging (MRI). It also presents established evidence for normal ranges of global and regional physiological cardiac function under ISO, proposes optimal, practical methodologies relevant to the use of anesthetic protocols for MRI and outlines the beneficial effects of nitrous oxide supplementation. PMID:27525256

  3. Molecular orientational dynamics in solid C70: Investigation by one- and two-dimensional magic angle spinning nuclear magnetic resonance

    NASA Astrophysics Data System (ADS)

    Tycko, R.; Dabbagh, G.; Vaughan, G. B. M.; Heiney, P. A.; Strongin, R. M.; Cichy, M. A.; Smith, A. B., III

    1993-11-01

    We present the results of 13C nuclear magnetic resonance (NMR) measurements that probe molecular orientational dynamics in solid C70 in the temperature range 223-343 K. Orientational dynamics affect the NMR line shapes and spin-lattice relaxation rates by modulating the 13C chemical shift anisotropy (CSA). Motionally averaged CSA line shapes, determined from both one-dimensional and two-dimensional magic angle spinning NMR spectra, and relaxation rates are determined for each of the five inequivalent carbon sites in the C70 molecule. Comparisons of the results for the five sites provide evidence for rapid uniaxial molecular reorientation in the monoclinic (T≤280 K) and rhombohedral (280≤T≤330 K) phases and rapid isotropic reorientation in the face-centered cubic (T≥330 K) phase. The orientational correlation time is roughly 2 ns at 250 K and of the order of 5 ps at 340 K.

  4. Streptavidin-modified monodispersed magnetic poly(2-hydroxyethyl methacrylate) microspheres as solid support in DNA-based molecular protocols.

    PubMed

    Salih, Tagrid; Ahlford, Annika; Nilsson, Mats; Plichta, Zdeněk; Horák, Daniel

    2016-04-01

    Molecular diagnostics may provide tailored and cost efficient treatment for infectious disease and cancer. Rolling circle amplification (RCA) of padlock probes guarantees high specificity to identify nucleic acid targets down to single nucleotide resolution in a multiplex fashion. This makes the assay suitable for molecular analysis of various diseases, and interesting to integrate into automated devices for point-of-care analysis. A critical prerequisite for many molecular assays is (i) target-specific isolation from complex clinical samples and (ii) removal of reagents, inhibitors and contaminants between reaction steps. Efficient solid supports are therefore essential to enable multi-step, multi-analyte protocols. Superparamagnetic micro- and nanoparticles, with large surface area and rapid liquid-phase kinetics, are attractive for multi-step protocols. Recently, streptavidin-modified magnetic monodispersed poly(2-hydroxyethyl methacrylate) (STV-mag.PHEMA) microspheres were developed by multiple swelling polymerization. They are easily separated by a magnet and exhibit low non-specific protein sorption. In this study, the performance and the binding efficiency of STV-mag.PHEMA was addressed by circle-to-circle amplification (C2CA). A lower number of RCA products were detected as compared to the gold standard Dynabeads. Nevertheless, this study was the first to successfully adapt STV-mag.PHEMA microspheres as solid support in a DNA-based protocol, which is an important finding. The STV-mag.PHEMA microspheres were larger with about 16 times less surface area as compared to the Dynabeads, which might partly explain the lower rolling circle product (RCP) count obtained. Further research is currently ongoing comparing particles of similar sizes and optimizing reaction conditions to establish their full utility in the field. Ultimately, low cost and versatile particles are a great resource to facilitate future clinical molecular diagnostics. PMID:26838862

  5. Molecular based magnets comprising vanadium tetracyanoethylene complexes for shielding electromagnetic fields

    DOEpatents

    Epstein, A.J.; Morin, B.G.

    1998-10-13

    The invention presents a vanadium tetracyanoethylene solvent complex for electromagnetic field shielding, and a method for blocking low frequency and magnetic fields using these vanadium tetracyanoethylene compositions. The compositions of the invention can be produced at ambient temperature and are light weight, low density and flexible. The materials of the present invention are useful as magnetic shields to block low frequency fields and static fields, and for use in cores in transformers and motors. 21 figs.

  6. Molecular based magnets comprising vanadium tetracyanoethylene complexes for shielding electromagnetic fields

    DOEpatents

    Epstein, Arthur J.; Morin, Brian G.

    1998-01-01

    The invention presents a vanadium tetracyanoethylene solvent complex for electromagnetic field shielding, and a method for blocking low frequency and magnetic fields using these vanadium tetracyanoethylene compositions. The compositions of the invention can be produced at ambient temperature and are light weight, low density and flexible. The materials of the present invention are useful as magnetic shields to block low frequency fields and static fields, and for use in cores in transformers and motors.

  7. Magnetic Capture of a Molecular Biomarker from Synovial Fluid in a Rat Model of Knee Osteoarthritis.

    PubMed

    Yarmola, Elena G; Shah, Yash; Arnold, David P; Dobson, Jon; Allen, Kyle D

    2016-04-01

    Biomarker development for osteoarthritis (OA) often begins in rodent models, but can be limited by an inability to aspirate synovial fluid from a rodent stifle (similar to the human knee). To address this limitation, we have developed a magnetic nanoparticle-based technology to collect biomarkers from a rodent stifle, termed magnetic capture. Using a common OA biomarker--the c-terminus telopeptide of type II collagen (CTXII)--magnetic capture was optimized in vitro using bovine synovial fluid and then tested in a rat model of knee OA. Anti-CTXII antibodies were conjugated to the surface of superparamagnetic iron oxide-containing polymeric particles. Using these anti-CTXII particles, magnetic capture was able to estimate the level of CTXII in 25 μL aliquots of bovine synovial fluid; and under controlled conditions, this estimate was unaffected by synovial fluid viscosity. Following in vitro testing, anti-CTXII particles were tested in a rat monoiodoacetate model of knee OA. CTXII could be magnetically captured from a rodent stifle without the need to aspirate fluid and showed tenfold changes in CTXII levels from OA-affected joints relative to contralateral control joints. Combined, these data demonstrate the ability and sensitivity of magnetic capture for post-mortem analysis of OA biomarkers in the rat. PMID:26136062

  8. Alexia without agraphia in a composer.

    PubMed

    Judd, T; Gardner, H; Geschwind, N

    1983-06-01

    A 77-year-old composer had a left occipital lobe haemorrhagic infarct giving a severe reading disturbance with well-preserved writing and without appreciable aphasia. He continued to read music and to compose. His text- and music-reading performance under different conditions suggests that this unusual dissociation was primarily due to four factors. (1) He was unusually talented musically and inferred a great deal about the music he was reading. (2) The symbols of staff music notation are more visually distinctive than the symbols of phonetic language writing systems. (3) In staff music notation, pitch is represented ordinally, and other symbols are also distinguishable by their relative positions and sizes. (4) Music notation can be usefully read by interpreting it acoustically, kinaesthetically or in terms of formal musical concepts; in contrast to written language, it need not be interpreted referentially or in terms of auditory-verbal images. His disorder fits the classic visual-verbal disconnection account of alexia without agraphia and the contemporary view that music involves a family of related but distinct skills probably involving many brain areas in both hemispheres, although different cortical areas make characteristic contributions to different musical behaviours. PMID:6850277

  9. Collapse and fragmentation of magnetic molecular cloud cores with the Enzo AMR MHD code. II. Prolate and oblate cores

    SciTech Connect

    Boss, Alan P.; Keiser, Sandra A.

    2014-10-10

    We present the results of a large suite of three-dimensional models of the collapse of magnetic molecular cloud cores using the adaptive mesh refinement code Enzo2.2 in the ideal magnetohydrodynamics approximation. The cloud cores are initially either prolate or oblate, centrally condensed clouds with masses of 1.73 or 2.73 M {sub ☉}, respectively. The radial density profiles are Gaussian, with central densities 20 times higher than boundary densities. A barotropic equation of state is used to represent the transition from low density isothermal phases, to high density optically thick phases. The initial magnetic field strength ranges from 6.3 to 100 μG, corresponding to clouds that are strongly to marginally supercritical, respectively, in terms of the mass to magnetic flux ratio. The magnetic field is initially uniform and aligned with the clouds' rotation axes, with initial ratios of rotational to gravitational energy ranging from 10{sup –4} to 0.1. Two significantly different outcomes for collapse result: (1) formation of single protostars with spiral arms, and (2) fragmentation into multiple protostar systems. The transition between these two outcomes depends primarily on the initial magnetic field strength, with fragmentation occurring for mass to flux ratios greater than about 14 times the critical ratio for prolate clouds. Oblate clouds typically fragment into several times more clumps than prolate clouds. Multiple, rather than binary, system formation is the general rule in either case, suggesting that binary stars are primarily the result of the orbital dissolution of multiple protostar systems.

  10. Preparation of thermal-responsive magnetic molecularly imprinted polymers for selective removal of antibiotics from aqueous solution.

    PubMed

    Xu, Longcheng; Pan, Jianming; Dai, Jiangdong; Li, Xiuxiu; Hang, Hui; Cao, Zhijing; Yan, Yongsheng

    2012-09-30

    A novel thermal-responsive magnetic molecularly imprinted polymers (TMMIPs), maghemite/silica/poly (N-isopropylacrylamide-co-acrylamide-co-ethylene glycol dimethacrylate) (γ-Fe(2)O(3)/SiO(2)/P (NIPAm-co-AAm-co-EGDMA)), were developed as a potential effective adsorbent for selectively remove sulfamethazine (SMZ) exist in aquatic environments, which has been recognized as a warranting considerable issue. Free radical polymerization of NIPAm, AAm and EGDMA was performed in dimethyl sulfoxide/water (DMSO/H(2)O) (v/v=9/1) with 2,2'-azobisisobutyronitrile (AIBN) as initiator to coat γ-Fe(2)O(3)/SiO(2)/3-(methacryloxyl) propyl trimethoxysilane (MPS) microspheres through the capture of oligomers with the aid of vinyl groups on their surfaces. The unique aspect of TMMIPs was that they combined molecular recognition, magnetic separation and thermo-responsiveness. The got material was characterized by SEM, TEM, FT-IR and VSM. Batch mode adsorption studies were carried out to investigate the specific adsorption equilibrium, kinetics, and selective recognition ability of TMMIPs. Reversible recognition and release of template molecule were realized by changing environmental temperatures. Several other antibiotics were selected as model analytes to evaluate the selective recognition performance of TMMIPs. The TMMIPs have good temperature response, selectivity and reusability, making them possible in applying for antibiotics separation and controlled release. PMID:22795838

  11. [Mental disease in two classical music composers].

    PubMed

    Rempelakos, L; Poulakou-Rebelakou, E; Ploumpidis, D

    2012-01-01

    A study οn two neglected classical music composers suffering a not syphilitic mental disease, is attempted here, syphilis of the central nervous system being frequent in that time. A brief overview on the psychiatric ailments of many great composers reveals suicide attempts and more or less severe depression following external events. The issue of a possible relationship between mental disease and (musical) creativity can be discussed, as mood swings and a certain tendency to melancholia are frequent features of a talented brain (a fact that can also be detected in their works). The first case presented here is Hans Rott from Austria, the beloved student of Anton Bruckner, who was considered to be at least equal to his famous classmate Gustav Mahler. The great expectations of his teacher and his friends suddenly came to an end, when he suffered a crisis of schizophrenia and was hospitalized in an insane asylum in Lower Austria. The tragic psychiatric adventure of the young musician lasted almost four years. He was diagnosed as a case of "hallucinatory insanity" and "persecution mania" by the medical staff, before dying of tuberculosis, aged only 26, and having completed only one symphony and several smaller works. His name came again on surface only a century after his death, when in 1989 his Symphony in E Major was discovered and premiered with great success, permitting to its creator a posthumous recognition, among Bruckner and Mahler. The second case of mental illness is that of the Armenian Komitas Vardapet. He was an orphan who grew up in theological schools and became a monk and later a priest, though he spent some years in Berlin in order to develop his musical skills. He is considered to be an authority of Armenian ecclesiastic music, introducing polyphony in the Armenian Church's music and collecting numerous traditional songs from all parts of Armenia. In 1915, during the Armenian genocide he was deported, tortured but finally saved, due to interventions

  12. Magnetic Luminescent Porous Silicon Microparticles for Localized Delivery of Molecular Drug Payloads

    PubMed Central

    Gu, Luo; Park, Ji-Ho; Duong, Kim H.; Ruoslahti, Erkki; Sailor, Michael J.

    2011-01-01

    Magnetic manipulation, fluorescent tracking, and localized delivery of a drug payload to cancer cells in vitro is demonstrated, using nanostructured porous silicon microparticles as a carrier. The multifunctional microparticles are prepared by electrochemical porosification of a silicon wafer in a hydrofluoric acid-containing electrolyte, followed by removal and fracture of the porous layer into particles using ultrasound. The intrinsically luminescent particles are loaded with superparamagnetic iron oxide nanoparticles and the anti-cancer drug doxorubicin. The drug-containing particles are delivered to human cervical cancer (HeLa) cells in vitro, under the guidance of a magnetic field. The high concentration of particles in the proximity of the magnetic field results in a high concentration of drug being released in that region of the Petri dish, and localized cell death is confirmed by cellular viability assay (Calcein AM). PMID:20814923

  13. Two-dimensional nuclear magnetic resonance studies of molecular structure in liquids and liquid crystals

    SciTech Connect

    Rucker, S.P.

    1991-07-01

    Magnetic couplings between protons, such as through-space dipole couplings, and scalar J-couplings depend sensitively on the structure of the molecule. Two dimensional nuclear magnetic resonance experiments provide a powerful tool for measuring these couplings, correlating them to specific pairs of protons within the molecule, and calculating the structure. This work discusses the development of NMR methods for examining two such classes of problems -- determination of the secondary structure of flexible molecules in anisotropic solutions, and primary structure of large biomolecules in aqueous solutions. 201 refs., 84 figs., 19 tabs.

  14. Magnetic tweezers measurement of the bond lifetime-force behavior of the IgG-protein A specific molecular interaction.

    PubMed

    Shang, Hao; Lee, Gil U

    2007-05-23

    The bond lifetime-force behavior of the immunoglobulin G (IgG)-protein A interaction has been studied with magnetic tweezers to characterize the physical properties of the bond under nonequilibrium conditions. Super-paramagnetic microparticles were developed that have a high and uniform magnetization to simultaneously apply a piconewton-scale tensile force to many thousands of IgG-protein A bonds. A strong and a weak slip bond were detected with an effective bond length that is characteristic of short-range, stiff intermolecular interactions. These bonds are attributed to the interaction of protein A with the constant region (Fc) and heavy chain variable domain (VH) of IgG, respectively. The IgG-VH interaction appears to be one of the weakest specific molecular interactions that has been identified with a single molecule force measurement technique. This study demonstrates that magnetic tweezers can be used to rapidly characterize very weak biomolecular interactions as well as strong biomolecular interactions with a high degree of accuracy. PMID:17465553

  15. Low-temperature anomalies in the magnetic and thermal properties of molecular cryocrystals doped with oxygen impurity

    NASA Astrophysics Data System (ADS)

    Freiman, Yu. A.; Tretyak, S. M.; JeŻowski, A.

    2000-09-01

    The magnetic properties of oxygen pair clusters are investigated theoretically for different cluster geometries which can be realized by doping molecular cryomatrices with oxygen. Anomalous temperature and pressure behavior of the magnetic susceptibility, heat capacity, and entropy is predicted. It is proposed to use these anomalies for studying the parameters characterizing the oxygen clusters and the parameters of the host matrix: the effective spin-figure interaction constant D for the molecule in the matrix, the exchange parameter J, and the number of pair clusters Np, which can deviate markedly from the purely random value Np=6Nc2 (N is Avogadro's number, and c is the molar concentration of the impurity). The data on the magnetic susceptibility may be used to analyze the character of the positional and orientational short-range order in the solid solution. The value of D contains information about the orientational order parameter; the distance and angular dependence of the exchange interaction parameter are still subject to discussion in the literature. The temperature dependence of Np contains information about diffusion and clusterization processes in the system.

  16. Preparation of magnetic molecularly imprinted polymer for the separation of tetracycline antibiotics from egg and tissue samples.

    PubMed

    Chen, Ligang; Liu, Jun; Zeng, Qinglei; Wang, Hui; Yu, Aimin; Zhang, Hanqi; Ding, Lan

    2009-05-01

    Magnetic molecularly imprinted polymers were prepared using hydrophobic Fe(3)O(4) magnetite as the magnetically susceptible component, oxytetracycline as template molecule, methacrylic acid as functional monomer, and styrene and divinylbenzene as polymeric matrix components. The polymers were applied to the separation of tetracycline antibiotics from egg and tissue samples. The extraction and clean-up procedures were carried out in a single step by blending and stirring the sample, extraction solvent and polymers. The analytes can be transferred from the sample matrix to the polymers directly or through the extraction solvent as medium. When the extraction was complete, the polymers adsorbing the analytes were easily separated from the sample matrix by an adscititious magnet. The analytes eluted from the polymers were determined by liquid chromatography-tandem mass spectrometry. The recoveries ranging from 72.8% to 96.5% were obtained with relative standard deviations in the range of 2.9-12.3%. The limit of detection was less than 0.2 ng g(-1). The feasibility of this method was validated by analysis of incurred egg and tissue samples, and the results were compared with those obtained by the classical method in which solvent extraction, centrifugation, and subsequent clean-up and concentration by solid-phase extraction were applied. The proposed method reduced the complicacy of classical method and improved the reliability of method. PMID:19268956

  17. Amyloid fibrils composed of hexameric peptides attenuate neuroinflammation.

    PubMed

    Kurnellas, Michael P; Adams, Chris M; Sobel, Raymond A; Steinman, Lawrence; Rothbard, Jonathan B

    2013-04-01

    The amyloid-forming proteins tau, αB crystallin, and amyloid P protein are all found in lesions of multiple sclerosis (MS). Our previous work established that amyloidogenic peptides from the small heat shock protein αB crystallin (HspB5) and from amyloid β fibrils, characteristic of Alzheimer's disease, were therapeutic in experimental autoimmune encephalomyelitis (EAE), reflecting aspects of the pathology of MS. To understand the molecular basis for the therapeutic effect, we showed a set of amyloidogenic peptides composed of six amino acids, including those from tau, amyloid β A4, major prion protein (PrP), HspB5, amylin, serum amyloid P, and insulin B chain, to be anti-inflammatory and capable of reducing serological levels of interleukin-6 and attenuating paralysis in EAE. The chaperone function of the fibrils correlates with the therapeutic outcome. Fibrils composed of tau 623-628 precipitated 49 plasma proteins, including apolipoprotein B-100, clusterin, transthyretin, and complement C3, supporting the hypothesis that the fibrils are active biological agents. Amyloid fibrils thus may provide benefit in MS and other neuroinflammatory disorders. PMID:23552370

  18. Amyloid Fibrils Composed of Hexameric Peptides Attenuate Neuroinflammation

    PubMed Central

    Kurnellas, Michael P.; Adams, Chris M.; Sobel, Raymond A.; Steinman, Lawrence; Rothbard, Jonathan B.

    2013-01-01

    Amyloid forming proteins Tau, alpha B crystallin, and amyloid P protein are all found in lesions of multiple sclerosis (MS). Our previous work established that amyloidogenic peptides from the small heat shock protein, alpha B crystallin(HspB5), and from amyloid β fibrils, characteristic of Alzheimer’s disease, were therapeutic in experimental autoimmune encephalomyelitis (EAE), reflecting aspects of the pathology of MS. To understand the molecular basis for the therapeutic effect, a set of amyloidogenic peptides composed of six amino acids, including those from tau, amyloid β A4, major prion protein (PrP), HspB5, amylin, serum amyloid P (SAP), and insulin B chain were shown to be anti-inflammatory, capable of reducing serological levels of IL-6, and attenuating paralysis in EAE. The chaperone function of the fibrils correlates with the therapeutic outcome. Fibrils composed of Tau 623–628 precipitated 49 plasma proteins, including apolipoprotein B-100, clusterin, transthyretin, and complement C3, supporting the hypothesis that the fibrils are active biological agents. Amyloid fibrils thus may provide benefit in MS and other neuroinflammatory disorders. PMID:23552370

  19. Molecular magnets based on metal complexes with spin-labeled imidazoles

    NASA Astrophysics Data System (ADS)

    Fursova, E.; Romanenko, G.; Ikorskii, V.; Ovcharenko, V.

    2004-04-01

    New heterospin systems based on Cu(II) and Mn(II) complexes with spin-labeled imidazol-4-yl derivatives were synthesized. Magneto-structural correlations inherent in their nature were investigated. Key words. Nitroxides metal complexes structure magnetic properties.

  20. Pair-eigenstates and mutual alignment of coupled molecular rotors in a magnetic field.

    PubMed

    Sharma, Ketan; Friedrich, Bretislav

    2016-05-11

    We examine the rotational states of a pair of polar (2)Σ molecules subject to a uniform magnetic field. The electric dipole-dipole interaction between the molecules creates entangled pair-eigenstates of two types. In one type, the Zeeman interaction between the inherently paramagnetic molecules and the magnetic field destroys the entanglement of the pair-eigenstates, whereas in the other type it does not. The pair-eigenstates exhibit numerous intersections, which become avoided for pair-eigenstates comprised of individual states that meet the selection rules ΔJi = 0, ± 1, ΔNi = 2n (n = 0, ±1, ±2,…), and ΔMi = 0, ± 1 imposed by the electric dipole-dipole operator. Here Ji, Ni and Mi are the total, rotational and projection angular momentum quantum numbers of molecules i = 1, 2 in the absence of the electric dipole-dipole interaction. We evaluate the mutual alignment of the pair-eigenstates and find it to be independent of the magnetic field, except for states that undergo avoided crossings, in which case the alignment of the interacting states is interchanged at the magnetic field corresponding to the crossing point. We present an analytic model which provides ready estimates of the pairwise alignment cosine that characterises the mutual alignment of the pair of coupled rotors. PMID:27126576

  1. Dispersion of Magnetic Fields in Molecular Clouds. IV. Analysis of Interferometry Data

    NASA Astrophysics Data System (ADS)

    Houde, Martin; Hull, Charles L. H.; Plambeck, Richard L.; Vaillancourt, John E.; Hildebrand, Roger H.

    2016-03-01

    We expand on the dispersion analysis of polarimetry maps toward applications to interferometry data. We show how the filtering of low spatial frequencies can be accounted for within the idealized Gaussian turbulence model, initially introduced for single-dish data analysis, to recover reliable estimates for correlation lengths of magnetized turbulence, as well as magnetic field strengths (plane-of-the-sky component) using the Davis-Chandrasekhar-Fermi method. We apply our updated technique to TADPOL/CARMA data obtained on W3(OH), W3 Main, and DR21(OH). For W3(OH), our analysis yields a turbulence correlation length δ ≃ 19 mpc, a ratio of turbulent-to-total magnetic energy < {B}{{t}}2> /< {B}2> ≃ 0.58, and a magnetic field strength {B}0˜ 1.1 {mG}; for W3 Main δ ≃ 22 mpc, < {B}{{t}}2> /< {B}2> ≃ 0.74, and {B}0˜ 0.7 {mG}; while for DR21(OH) δ ≃ 12 mpc, < {B}{{t}}2> /< {B}2> ≃ 0.70, and {B}0˜ 1.2 {mG}.

  2. Molecular materials with conducting and magnetic properties based on ET and [ M(tdas){2}]x- dithiolenes

    NASA Astrophysics Data System (ADS)

    Mercuri, M. L.; Curreli, S.; Deplano, P.; Pilia, L.; Serpe, A.; Trogu, E. F.; Schlueter, J. A.; Gómez-García, C. J.

    2004-04-01

    Two hybrid molecular materials showing a combination of magnetic and conducting properties, the charge-transfer (ET){2}[ Fe(tdas){2}] (1) and (ET)Ni(tdas){2} (2), (ET=bis(ethylenedithio) tetrathiafulvalene; M=Fe, Ni; tdas=1,2,5-thiadiazole-3,4-dithiolate) salts, are characterized by vibrational (IR and Raman) and UV-VIS-NIR spectroscopies. These studies have proved to be effective and diagnostic tools in identifying the oxidation state (partial or integer) and the packing pattern (dimers or segregated stacks) of the ET donor only, since no ν (C=C) group vibration sensitive to the charge of M(tdas){2} complexes has been observed. This is ascribed to the extensive electron-delocalization inside the tdas ring in agreement with semiempirical extended Huckel calculations, indicating also that the AO's of the terminal S-atom give a high contribution to the HOMO and favour the occurrence of three-dimensional intermolecular interactions along the molecular longitudinal axis. These findings are consistent with structural results. Key words. Dithiolenes Molecular Materials Raman Spectroscopy Reflectance Spectroscopy.

  3. [Effects and molecular mechanisms of the biological action of weak and extremely weak magnetic fields].

    PubMed

    Novikov, V V; Ponomarev, V O; Novikov, G V; Kuvichkin, V V; Iablokova, E V; Fesenko, E E

    2010-01-01

    A number of effects of weak combined (static and alternating) magnetic fields with an alternating component of tens and hundreds nT at a collinear static field of 42 microT, which is equivalent to the geomagnetic field, have been found: the activation of fission and regeneration of planarians Dugesia tigrina, the inhibition of the growth of the Ehrlich ascites carcinoma in mice, the stimulation of the production of the tumor necrosis factor by macrophages, a decrease in the protection of chromatin against the action of DNase 1, and the enhancement of protein hydrolysis in systems in vivo and in vitro. The frequency and amplitude ranges for the alternating component of weak combined magnetic fields have been determined at which it affects various biological systems. Thus, the optimal amplitude at a frequency of 4.4 Hz is 100 nT (effective value); at a frequency of 16.5 Hz, the range of effective amplitudes is broader, 150-300 nT; and at a frequency of 1 (0.5) Hz, it is 300 nT. The sum of close frequencies (e.g., 16 and 17 Hz) produces a similar biological effect as the product of the modulating (0.5 Hz) and carrying frequencies (16.5 Hz), which is explained by the ratio A = A0sin omega1t + A0sin omega2t = A0sin(omega1 + omega2)t/2cos(omega1 - omega2)t/2. The efficiency of magnetic signals with pulsations (the sum of close frequencies) is more pronounced than that of sinusoidal frequencies. These data may indicate the presence of several receptors of weak magnetic fields in biological systems and, as a consequence, a higher efficiency of the effect at the simultaneous adjustment to these frequencies by the field. Even with consideration of these facts, the mechanism of the biological action of weak combined magnetic fields remains still poorly understood. PMID:20968074

  4. Synthesis and Characterization of Magnetic Molecularly Imprinted Polymer for the Enrichment of Ofloxacin Enantiomers in Fish Samples.

    PubMed

    Wang, Yan-Fei; Jin, Huo-Xi; Wang, Yang-Guang; Yang, Li-Ye; OuYang, Xiao-Kun; Wu, Wei-Jian

    2016-01-01

    A new method for the isolation and enrichment of ofloxacin enantiomers from fish samples was developed using magnetic molecularly imprinted polymers (MMIPs). These polymers can be easily collected and rapidly separated using an external magnetic field, and also exhibit a high specific recognition for ofloxacin enantiomers. The preparation of amino-functionalized MMIPs was carried out via suspension polymerization and a ring-opening reaction using rac-ofloxacin as a template, ethylenediamine as an active group, glycidyl methacrylate and methyl methacrylate as functional monomers, divinylbenzene as a cross-linker, and Fe₃O₄ nanoparticles as magnetic cores. The characteristics of the MMIPs were assessed using transmission electron microscopy (TEM), X-ray powder diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), and vibrating sample magnetometer (VSM) measurements. Furthermore, the adsorption properties were determined using Langmuir and Freundlich isotherm models. The conditions for use of these MMIPs as magnetic solid-phase extraction (MSPE) sorbents, including pH, adsorption time, desorption time, and eluent, were investigated in detail. An extraction method using MMIPs coupled with high performance liquid chromatography (HPLC) was developed for the determination of ofloxacin enantiomers in fish samples. The limits of quantitation (LOQ) for the developed method were 0.059 and 0.067 μg∙mL(-1) for levofloxacin and dextrofloxacin, respectively. The recovery of ofloxacin enantiomers ranged from 79.2% ± 5.6% to 84.4% ± 4.6% and ofloxacin enantiomers had good linear relationships within the concentration range of 0.25-5.0 μg∙mL(-1) (R² > 0.999). The obtained results demonstrate that MSPE-HPLC is a promising approach for preconcentration, purification, and simultaneous separation of ofloxacin enantiomers in biomatrix samples. PMID:27428943

  5. Molecular extraction in single live cells by sneaking in and out magnetic nanomaterials

    PubMed Central

    Yang, Zhen; Deng, Liangzi; Lan, Yucheng; Zhang, Xiaoliu; Gao, Zhonghong; Chu, Ching-Wu; Cai, Dong; Ren, Zhifeng

    2014-01-01

    Extraction of intracellular molecules is crucial to the study of cellular signal pathways. Disruption of the cellular membrane remains the established method to release intracellular contents, which inevitably terminates the time course of biological processes. Also, conventional laboratory extractions mostly use bulky materials that ignore the heterogeneity of each cell. In this work, we developed magnetized carbon nanotubes that can be sneaked into and out of cell bodies under a magnetic force. Using a testing model with overexpression of GFP, the nanotubes successfully transported the intracellular GFP out at the single-cell level. The confined nanoscale invasiveness did not change cell viability or proliferation. This study presents the proof of concept of a previously unidentified real-time and single-cell approach to investigate cellular biology, signal messengers, and therapeutic effects with nanomaterials. PMID:25030447

  6. A theoretical study of magnetoelectronic and switching properties of molecular magnetic tunnel junctions

    NASA Astrophysics Data System (ADS)

    Soti, V.; Ravan, B. Abedi

    2016-01-01

    Electronic transport and switching properties of molecule-based magnetic tunnel junctions are investigated using the first-principles density functional theory and non-equilibrium Green function methods. As a result of being sandwiched between the ferromagnetic electrodes, a spin-polarization is induced in the nonmagnetic organic atoms. Magnitudes of the spin-polarizations in the trans-polyacetylene, cis-polyacetylene, terphenyl and pentacene chains are calculated and it is suggested that among these the pentacene molecules, because of showing a relatively higher magnetization can theoretically be more appropriate for utilization in spintronic devices. Furthermore, electrical switching capabilities of the junctions are studied and the results reveal that the pentacene junction due to having a larger ON/OFF ratio shows a better switching behavior. Finally, magnetoresistive properties are studied and it is shown that applying torsion can be an effective method to enhance and also adjust magnitudes of the magnetoresistances of the junctions.

  7. Effects of D-strain, g-strain, and dipolar interactions on EPR linewidths of the molecular magnets Fe8 and Mn12

    NASA Astrophysics Data System (ADS)

    Park, Kyungwha; Novotny, M. A.; Dalal, N. S.; Hill, S.; Rikvold, P. A.

    2002-01-01

    Electron paramagnetic resonance measurements on single crystals of the molecular magnets Fe8 and Mn12 reveal complex nonlinearities in the linewidths as functions of energy eigenstate, frequency, and temperature. Using a density-matrix equation with distributions of the uniaxial anisotropy parameter D, the Landé g factor, and dipolar interactions, we obtain linewidths in good agreement with experiments. Our study shows that the distribution in D is common to the examined molecular magnets Fe8 and Mn12 regardless of the qualities of the samples. This could provide the basis for a proposed tunneling mechanism due to lattice defects. The distribution in g is also quite significant for Mn12.

  8. Development of a High Resolution Analyzing Magnet System for Heavy Molecular Ions

    NASA Astrophysics Data System (ADS)

    Ghazaly, Mohamed O. A. El; Dehnel, Morgan; Defrance, Pierre

    At the King Abdulaziz City for Science and Technology (KACST, Saudi Arabia), a versatile ion-beam injector was constructed to provide the electrostatic storage ring with the required high-quality ion beams. In order to remove the ambiguity over the ion mass due to the exclusive application of electric fields in the set-up, the injector is being equipped with a high resolution mass analyzing magnet. A high resolution Analyzing Magnet System has been designed to provide a singly-charged ion beam of kinetic energy up to 50 keV, mass up to 1500 Amu, and with the mass resolution fixed to Δm/m =1:1500. The system includes specific entrance and exit slits, designed to sustain the required mass resolution. Furthermore, specific focusing and shaping optics have been added upstream and downstream the system, in order to monitor and adapt the shape of the ion beam at the entrance and exit of the system, respectively. The present paper gives an overview on the design of this mass analyzing magnet system together with the upstream/downstream adapting optics.

  9. A model for the magnetic field in the molecular disk at the Galactic center

    SciTech Connect

    Wardle, M.; Konigl, A. )

    1990-10-01

    A model for the magnetic field configuration in the Galactic center disk is presented. The field has an open geometry and represents the poloidal field detected at larger distances from the Galactic center, stretched and twisted by the effects of advection and shear in a magnetized accretion disk. It is concluded that the 100 micron polarization measurements of Hildebrand et al. (1990) imply that the radial and azimuthal components of the magnetic field in the disk are comparable and have opposite signs, consistent with the generation of B(phi) from B(r) by differential rotation. The polarization measurements indicate that the z-component of the field is smaller than both /B(phi)/ and /B(r)/; thus, they do not by themselves require that the field lines thread the disk. The field strengths of order 1 mG inferred from the Zeeman measurements and the fact that /B(phi)/ and /B(r)/ exceed B(z) imply that the field could remove the excess angular momentum of the accreted matter in the form of a centrifugally driven outflow. 31 refs.

  10. Molecular MRI in the Earth's Magnetic Field Using Continuous Hyperpolarization of a Biomolecule in Water.

    PubMed

    Rovedo, Philipp; Knecht, Stephan; Bäumlisberger, Tim; Cremer, Anna Lena; Duckett, Simon B; Mewis, Ryan E; Green, Gary G R; Burns, Michael; Rayner, Peter J; Leibfritz, Dieter; Korvink, Jan G; Hennig, Jürgen; Pütz, Gerhard; von Elverfeldt, Dominik; Hövener, Jan-Bernd

    2016-06-30

    In this work, we illustrate a method to continuously hyperpolarize a biomolecule, nicotinamide, in water using parahydrogen and signal amplification by reversible exchange (SABRE). Building on the preparation procedure described recently by Truong et al. [ J. Phys. Chem. B , 2014 , 118 , 13882 - 13889 ], aqueous solutions of nicotinamide and an Ir-IMes catalyst were prepared for low-field NMR and MRI. The (1)H-polarization was continuously renewed and monitored by NMR experiments at 5.9 mT for more than 1000 s. The polarization achieved corresponds to that induced by a 46 T magnet (P = 1.6 × 10(-4)) or an enhancement of 10(4). The polarization persisted, although reduced, if cell culture medium (DPBS with Ca(2+) and Mg(2+)) or human cells (HL-60) were added, but was no longer observable after the addition of human blood. Using a portable MRI unit, fast (1)H-MRI was enabled by cycling the magnetic field between 5 mT and the Earth's field for hyperpolarization and imaging, respectively. A model describing the underlying spin physics was developed that revealed a polarization pattern depending on both contact time and magnetic field. Furthermore, the model predicts an opposite phase of the dihydrogen and substrate signal after one exchange, which is likely to result in the cancelation of some signal at low field. PMID:27228166

  11. Molecular charge contact biosensing based on the interaction of biologically modified magnetic beads with an ion-sensitive field effect transistor.

    PubMed

    Miyazawa, Yuuya; Sakata, Toshiya

    2014-05-01

    In this article, we report a novel method of biomolecular recognition based on the molecular charge contact (MCC). As one of the MCC biosensing method, the interaction between DNA-coated magnetic beads and a silicon-based semiconductor, an ion-sensitive field effect transistor (ISFET) could be detected for DNA molecular recognition events using the principle of the field effect, which enables detecting ionic or molecular charges. After DNA-coated magnetic beads had been introduced and brought in contact with the gate surface by a magnet, the threshold voltage of the ISFET was shifted in the positive direction by immobilization, hybridization and extension reaction of DNA molecules on magnetic beads. This positive shift was based on the increase in negative charges of the phosphate groups in them. Then, the ISFET device could be reused a couple of dozen times continuously and cost-effectively because the oligonucleotide probes were tethered to the magnetic beads, but this was not done directly on the gate surface of the ISFET. Moreover, the MCC biosensing method enabled discrimination of a single nucleotide polymorphism. By creating an interaction of magnetic beads with the semiconductor, we can expect enhancement of the reaction efficiency in a solution and reuse of the device by separating the reaction field from the sensing substrate. PMID:24595376

  12. Magnetic transitions of single-component molecular metal [Au(tmdt)2] and its alloy systems.

    PubMed

    Zhou, Biao; Shimamura, Mina; Fujiwara, Emiko; Kobayashi, Akiko; Higashi, Takeshi; Nishibori, Eiji; Sakata, Makoto; Cui, Hengbo; Takahashi, Kazuyuki; Kobayashi, Hayao

    2006-03-29

    A single-component molecular conductor [Au(tmdt)2] (tmdt = trimethylenetetrathiafulvalenedithiolate) undergoes an antiferromagnetic phase transition at unprecedentedly high temperature (TN = 110 K). Black microcrystals of alloys, [Ni1-xAux(tmdt)2] (0.0 < x < 1.0) were prepared. The Au-rich system exhibited an antiferromagnetic transition. Metallic single crystal was obtained for x = 0.25. PMID:16551070

  13. Application of Molecular Imprinted Magnetic Fe3O4@SiO2 Nanoparticles for Selective Immobilization of Cellulase.

    PubMed

    Tao, Qing-Lan; Li, Yue; Shi, Ying; Liu, Rui-Jiang; Zhang, Ye-Wang; Guo, Jianyong

    2016-06-01

    Magnetic Fe3O4@SiO2 nanoparticles were prepared with molecular imprinting method using cellulase as the template. And the surface of the nanoparticles was chemically modified with arginine. The prepared nanoparticles were used as support for specific immobilization of cellulase. SDS-PAGE results indicated that the adsorption of cellulase onto the modified imprinted nanoparticles was selective. The immobilization yield and efficiency were obtained more than 70% after the optimization. Characterization of the immobilized cellulase revealed that the immobilization didn't change the optimal pH and temperature. The half-life of the immobilized cellulase was 2-fold higher than that of the free enzyme at 50 degrees C. After 7 cycles reusing, the immobilized enzyme still retained 77% of the original activity. These results suggest that the prepared imprinted nanoparticles have the potential industrial applications for the purification or immobilization of enzymes. PMID:27427671

  14. Competitive fluorescence assay for specific recognition of atrazine by magnetic molecularly imprinted polymer based on Fe3O4-chitosan.

    PubMed

    Liu, Guangyang; Li, Tengfei; Yang, Xin; She, Yongxin; Wang, Miao; Wang, Jing; Zhang, Min; Wang, Shanshan; Jin, Fen; Jin, Maojun; Shao, Hua; Jiang, Zejun; Yu, Hailong

    2016-02-10

    A novel fluorescence sensing strategy for determination of atrazine in tap water involving direct competition between atrazine and 5-(4,6-dichlorotriazinyl) aminofluorescein (5-DTAF), and which exploits magnetic molecularly imprinted polymer (MMIP), has been developed. The MMIP, based on Fe3O4-chitosan nanoparticles, was synthesized to recognize specific binding sites of atrazine. The recognition capability and selectivity of the MMIP for atrazine and other triazine herbicides was investigated. Under optimal conditions, the competitive reaction between 5-DTAF and atrazine was performed to permit quantitation. Fluorescence intensity changes at 515 nm was linearly related to the logarithm of the atrazine concentration for the range 2.32-185.4 μM. The detection limit for atrazine was 0.86μM (S/N=3) and recoveries were 77.6-115% in spiked tap water samples. PMID:26686107

  15. Joint Composable Object Model and LVC Methodology

    NASA Technical Reports Server (NTRS)

    Rheinsmith, Richard; Wallace, Jeffrey; Bizub, Warren; Ceranowicz, Andy; Cutts, Dannie; Powell, Edward T.; Gustavson, Paul; Lutz, Robert; McCloud, Terrell

    2010-01-01

    Within the Department of Defense, multiple architectures are created to serve and fulfill one or several specific service or mission related LVC training goals. Multiple Object Models exist across and within those architectures and it is there that those disparate object models are a major source of interoperability problems when developing and constructing the training scenarios. The two most commonly used architectures are; HLA and TENA, with DIS and CTIA following close behind in terms of the number of users. Although these multiple architectures can share and exchange data the underlying meta-models for runtime data exchange are quite different, requiring gateways/translators to bridge between the different object model representations; while the Department of Defense's use of gateways are generally effective in performing these functions, as the LVC environment increases so too does the cost and complexity of these gateways. Coupled with the wide range of different object models across the various user communities we increase the propensity for run time errors, increased programmer stop gap measures during coordinated exercises, or failure of the system as a whole due to unknown or unforeseen incompatibilities. The Joint Composable Object Model (JCOM) project was established under an M&S Steering Committee (MSSC)-sponsored effort with oversight and control placed under the Joint Forces Command J7 Advanced Concepts Program Directorate. The purpose of this paper is to address the initial and the current progress that has been made in the following areas; the Conceptual Model Development Format, the Common Object Model, the Architecture Neutral Data Exchange Model (ANDEM), and the association methodology to allow the re-use of multiple architecture object models and the development of the prototype persistent reusable library.

  16. Co-Ln mixed-metal phosphonate grids and cages as molecular magnetic refrigerants.

    PubMed

    Zheng, Yan-Zhen; Evangelisti, Marco; Tuna, Floriana; Winpenny, Richard E P

    2012-01-18

    The synthesis, structures, and magnetic properties of six families of cobalt-lanthanide mixed-metal phosphonate complexes are reported in this Article. These six families can be divided into two structural types: grids, where the metal centers lie in a single plane, and cages. The grids include [4 × 3] {Co(8)Ln(4)}, [3 × 3] {Co(4)Ln(6)}, and [2 × 2] {Co(4)Ln(2)} families and a [4 × 4] {Co(8)Ln(8)} family where the central 2 × 2 square is rotated with respect to the external square. The cages include {Co(6)Ln(8)} and {Co(8)Ln(2)} families. Magnetic studies have been performed for these compounds, and for each family, the maximum magnetocaloric effect (MCE) has been observed for the Ln = Gd derivative, with a smaller MCE for the compounds containing magnetically anisotropic 4f-ions. The resulting entropy changes of the gadolinium derivatives are (for 3 K and 7 T) 11.8 J kg(-1) K(-1) for {Co(8)Gd(2)}; 20.0 J kg(-1) K(-1) for {Co(4)Gd(2)}; 21.1 J kg(-1) K(-1) for {Co(8)Gd(4)}; 21.4 J kg(-1) K(-1) for {Co(8)Gd(8)}; 23.6 J kg(-1) K(-1) for {Co(4)Gd(6)}; and 28.6 J kg(-1) K(-1) for {Co(6)Gd(8)}, from which we can see these values are proportional to the percentage of the gadolinium in the core. PMID:22171923

  17. The protective effect of a constant magnetic field. [reduction of molecular cell pathology

    NASA Technical Reports Server (NTRS)

    Sosunov, A. V.; Tripuzov, A. N.

    1974-01-01

    The protective effect of a constant magnetic field sharply reduced spontaneous lysis of E. coli cells when subjected to ultraviolet radiation. A protective effect of a CMF was found in a study of tissue cultures of normally growing cells (kidney epithelium) and cancer cells (cells from a cancer of the larynx). The protective effect of a CMF is also seen in a combined exposure of tissue cultures to X-rays and CMF energy (strength of the CMF was 2000 oersteds with a gradient of 500 oersteds/cm). The data obtained are of interest to experimental oncology (development of new methods of treating malignant tumors).

  18. Magnetic properties of Fe0.4Mn0.6/Co2FeAl bilayers grown on GaAs by molecular-beam epitaxy

    NASA Astrophysics Data System (ADS)

    Meng, K. K.; Nie, S. H.; Yu, X. Z.; Wang, S. L.; Yan, W. S.; Zhao, J. H.

    2011-11-01

    Polycrystalline Fe0.4Mn0.6 layers with the different thickness are deposited on 4-nm-thick single-crystalline Co2FeAl layers, which are grown on GaAs (001) substrates at room temperature by molecular-beam epitaxy. Both the exchange bias and the in-plane magnetic anisotropies of the bilayers are strongly dependent on the thickness of the Fe0.4Mn0.6 layer. The former is described using a granular level model. A modified Stoner-Wohlfarth model is used to explain the in-plane magnetic anisotropies observed at 5 K, while one possible reason for the magnetic anisotropies measured at 300 K is the complex interfacial magnetic properties proved by x-ray magnetic circular dichroism measurements.

  19. Low temperature magnetic properties and spin dynamics in single crystals of Cr{sub 8}Zn antiferromagnetic molecular rings

    SciTech Connect

    Adelnia, Fatemeh; Chiesa, Alessandro; Bordignon, Sara; Carretta, Stefano; Ghirri, Alberto; Candini, Andrea; Cervetti, Christian; Evangelisti, Marco; Affronte, Marco; Sheikin, Ilya; Winpenny, Richard; Timco, Grigore; Borsa, Ferdinando; and others

    2015-12-28

    A detailed experimental investigation of the effects giving rise to the magnetic energy level structure in the vicinity of the level crossing (LC) at low temperature is reported for the open antiferromagnetic molecular ring Cr{sub 8}Zn. The study is conducted by means of thermodynamic techniques (torque magnetometry, magnetization and specific heat measurements) and microscopic techniques (nuclear magnetic resonance line width, nuclear spin lattice, and spin-spin relaxation measurements). The experimental results are shown to be in excellent agreement with theoretical calculations based on a minimal spin model Hamiltonian, which includes a Dzyaloshinskii-Moriya interaction. The first ground state level crossing at μ{sub 0}H{sub c1} = 2.15 T is found to be an almost true LC while the second LC at μ{sub 0}H{sub c2} = 6.95 T has an anti-crossing gap of Δ{sub 12} = 0.19 K. In addition, both NMR and specific heat measurements show the presence of a level anti-crossing between excited states at μ{sub 0}H = 4.5 T as predicted by the theory. In all cases, the fit of the experimental data is improved by introducing a distribution of the isotropic exchange couplings (J), i.e., using a J strain model. The peaks at the first and second LCs in the nuclear spin-lattice relaxation rate are dominated by inelastic scattering and a value of Γ ∼ 10{sup 10} rad/s is inferred for the life time broadening of the excited state of the open ring, due to spin phonon interaction. A loss of NMR signal (wipe-out effect) is observed for the first time at LC and is explained by the enhancement of the spin-spin relaxation rate due to the inelastic scattering.

  20. Facile synthesis of magnetic molecularly imprinted polymer: Perphenazine template and its application in urine and plasma analysis.

    PubMed

    Safdarian, Mehdi; Ramezani, Zahra; Ghadiri, Ata A

    2016-07-15

    Synthesis of magnetic iron oxide nanoparticles and its surface modification with methacrylic acid (MAA) was performed simultaneously by adding Fe(2+)/Fe(3+) to an alkaline MAA solution under nitrogen atmosphere. MAA coated magnetite (Fe3O4@MAA) has abundant reactive double bonds on the surface that can initiate polymerization. Magnetic molecularly imprinted polymers (MMIPs) were synthesized through distillation-precipitation polymerization of MAA as monomer, perphenazine (PPZ) as template, and ethylene glycol di-methacrylate (EGDMA) as cross linker on Fe3O4@MAA, with concise control of experimental conditions in about 90min. The produced super paramagnetic MMIPs can be separated from the solution in the presence of external magnetic field in less than 1min. Characterizations of the synthesized particles were performed by electron microscopes, thermo-gravimetric analysis (TGA), vibrating sample magnetometer (VSM), Fourier transform infrared (FT-IR) spectroscopy, and BET. The data showed that Fe3O4@MAA was well encapsulated in the polymer shell. The MMIPs showed high porosity. Moreover, MMIPs were used for rapid pre-concentration and separation of PPZ in human plasma and urine without any dilution and pretreatments using high performance liquid chromatography equipped with a photo diode array detector (HPLC-PDA). The calibration curve in urine and plasma has shown the same slope as the external calibration curve. Linear range of 20-5000ngmL(-1), and a detection limit of 5.3ngmL(-1) was obtained. The results showed 97.92% recovery along with the relative standard deviation of 6.07% (n=6) for 1μgmL(-1) PPZ. Pre-concentration factor was 13. The MMIPs adsorbed PPZ in 1min and then desorbed it by MeOH:HOAc in 2min. PMID:27302687

  1. Low temperature magnetic properties and spin dynamics in single crystals of Cr8Zn antiferromagnetic molecular rings

    NASA Astrophysics Data System (ADS)

    Adelnia, Fatemeh; Chiesa, Alessandro; Bordignon, Sara; Carretta, Stefano; Ghirri, Alberto; Candini, Andrea; Cervetti, Christian; Evangelisti, Marco; Affronte, Marco; Sheikin, Ilya; Winpenny, Richard; Timco, Grigore; Borsa, Ferdinando; Lascialfari, Alessandro

    2015-12-01

    A detailed experimental investigation of the effects giving rise to the magnetic energy level structure in the vicinity of the level crossing (LC) at low temperature is reported for the open antiferromagnetic molecular ring Cr8Zn. The study is conducted by means of thermodynamic techniques (torque magnetometry, magnetization and specific heat measurements) and microscopic techniques (nuclear magnetic resonance line width, nuclear spin lattice, and spin-spin relaxation measurements). The experimental results are shown to be in excellent agreement with theoretical calculations based on a minimal spin model Hamiltonian, which includes a Dzyaloshinskii-Moriya interaction. The first ground state level crossing at μ0Hc1 = 2.15 T is found to be an almost true LC while the second LC at μ0Hc2 = 6.95 T has an anti-crossing gap of Δ12 = 0.19 K. In addition, both NMR and specific heat measurements show the presence of a level anti-crossing between excited states at μ0H = 4.5 T as predicted by the theory. In all cases, the fit of the experimental data is improved by introducing a distribution of the isotropic exchange couplings (J), i.e., using a J strain model. The peaks at the first and second LCs in the nuclear spin-lattice relaxation rate are dominated by inelastic scattering and a value of Γ ˜ 1010 rad/s is inferred for the life time broadening of the excited state of the open ring, due to spin phonon interaction. A loss of NMR signal (wipe-out effect) is observed for the first time at LC and is explained by the enhancement of the spin-spin relaxation rate due to the inelastic scattering.

  2. Novel readout method for molecular diagnostic assays based on optical measurements of magnetic nanobead dynamics.

    PubMed

    Donolato, Marco; Antunes, Paula; Bejhed, Rebecca S; Zardán Gómez de la Torre, Teresa; Østerberg, Frederik W; Strömberg, Mattias; Nilsson, Mats; Strømme, Maria; Svedlindh, Peter; Hansen, Mikkel F; Vavassori, Paolo

    2015-02-01

    We demonstrate detection of DNA coils formed from a Vibrio cholerae DNA target at picomolar concentrations using a novel optomagnetic approach exploiting the dynamic behavior and optical anisotropy of magnetic nanobead (MNB) assemblies. We establish that the complex second harmonic optical transmission spectra of MNB suspensions measured upon application of a weak uniaxial AC magnetic field correlate well with the rotation dynamics of the individual MNBs. Adding a target analyte to the solution leads to the formation of permanent MNB clusters, namely, to the suppression of the dynamic MNB behavior. We prove that the optical transmission spectra are highly sensitive to the formation of permanent MNB clusters and, thereby to the target analyte concentration. As a specific clinically relevant diagnostic case, we detect DNA coils formed via padlock probe recognition and isothermal rolling circle amplification and benchmark against a commercial equipment. The results demonstrate the fast optomagnetic readout of rolling circle products from bacterial DNA utilizing the dynamic properties of MNBs in a miniaturized and low-cost platform requiring only a transparent window in the chip. PMID:25539065

  3. Lost and found: The missing diabolical points in the Fe8 molecular magnet

    NASA Astrophysics Data System (ADS)

    Li, Feifei; Garg, Anupam

    2011-03-01

    The tunneling spectrum of the single-molecule-magnet Fe 8 is known to have diabolical points (DP's). For magnetic fields along the hard axis, there are four such points for tunneling between the ground pair of levels, whereas the simplest model including only second-order anisotropy would predict ten DP's. The difference is due to a very weak fourth-order anisotropy, which in a semiclassical picture generates instantons with endpoint discontinuities, one of which dominates for large enough fields, and having no interfering partner, causes six of the underlying DP's to go away. However, as shown by Bruno, the six missing DP's do not truly disappear, but merely move off the hard axis into the hard-medium plane. In this talk, we report on a numerical search for these ``missing" DP's. This search is nontrivial because the energy surface is like a smooth golf course, on which the DP's are extremely localized and deep holes. We therefore locate the DP's by following the lines of the Berry curvature which have monopole singulairities at the DP's. This exercise is performed for tunneling between excited pairs of levels also. An experimental observation of the rediscovered DP's would be an important test of the underlying spin Hamiltonian for Fe 8 . (Submitted to the arxiv: Nov. 18, 2010.) Work supported by the NSF via grant no. PHY-0854896.

  4. Referencing strategy for the direct comparison of nuclear magnetic resonance and molecular dynamics motional parameters in RNA.

    PubMed

    Musselman, Catherine; Zhang, Qi; Al-Hashimi, Hashim; Andricioaei, Ioan

    2010-01-21

    Nuclear magnetic resonance (NMR) spectroscopy and molecular dynamics (MD) simulations are both techniques that can be used to characterize the structural dynamics of biomolecules and their underlying time scales. Comparison of relaxation parameters obtained through each methodology allows for cross validation of techniques and for complementarity in the analysis of dynamics. Here we present a combined NMR/MD study of the dynamics of HIV-1 transactivation response (TAR) RNA. We compute relaxation constants (R(1), R(2), and NOE) and model-free parameters (S(2) and tau) from a 65 ns molecular dynamics (MD) trajectory and compare them with the respective parameters measured in a domain-elongation NMR experiment. Using the elongated domain as the frame of reference for all computed parameters allows for a direct comparison between experiment and simulation. We see good agreement for many parameters and gain further insight into the nature of the local and global dynamics of TAR, which are found to be quite complex, spanning multiple time scales. For the few cases where agreement is poor, comparison of the dynamical parameters provides insight into the limits of each technique. We suggest a frequency-matching procedure that yields an upper bound for the time scale of dynamics to which the NMR relaxation experiment is sensitive. PMID:20039757

  5. Fluoride-bridged {Gd(III)3M(III)2} (M = Cr, Fe, Ga) molecular magnetic refrigerants.

    PubMed

    Pedersen, Kasper S; Lorusso, Giulia; Morales, Juan José; Weyhermüller, Thomas; Piligkos, Stergios; Singh, Saurabh Kumar; Larsen, Dennis; Schau-Magnussen, Magnus; Rajaraman, Gopalan; Evangelisti, Marco; Bendix, Jesper

    2014-02-24

    The reaction of fac-[M(III)F3(Me3tacn)]⋅x H2O with Gd(NO3)3⋅5H2O affords a series of fluoride-bridged, trigonal bipyramidal {Gd(III)3M(III)2} (M = Cr (1), Fe (2), Ga (3)) complexes without signs of concomitant GdF3 formation, thereby demonstrating the applicability even of labile fluoride-complexes as precursors for 3d-4f systems. Molecular geometry enforces weak exchange interactions, which is rationalized computationally. This, in conjunction with a lightweight ligand sphere, gives rise to large magnetic entropy changes of 38.3 J kg(-1)  K(-1) (1) and 33.1 J kg(-1)  K(-1) (2) for the field change 7 T→0 T. Interestingly, the entropy change, and the magnetocaloric effect, are smaller in 2 than in 1 despite the larger spin ground state of the former secured by intramolecular Fe-Gd ferromagnetic interactions. This observation underlines the necessity of controlling not only the ground state but also close-lying excited states for successful design of molecular refrigerants. PMID:24574031

  6. Preparation of a magnetic molecularly imprinted polymer by atom-transfer radical polymerization for the extraction of parabens from fruit juices.

    PubMed

    You, Xiaoxiao; Piao, Chungying; Chen, Ligang

    2016-07-01

    A silica-based surface magnetic molecularly imprinted polymer for the selective recognition of parabens was prepared using a facile and general method that combined atom-transfer radical polymerization with surface imprinting technique. The prepared magnetic molecularly imprinted polymer was characterized by transmission electron microscopy, Fourier transform infrared spectrometry and physical property measurement. The isothermal adsorption experiment and kinetics adsorption experiment investigated the adsorption property of magnetic molecularly imprinted polymer to template molecule. The four parabens including methylparaben, ethylparaben, propylparaben, and butylparaben were used to assess the rebinding selectivity. An extraction method, which used magnetic molecularly imprinted polymer as adsorbents coupled with high-performance liquid chromatography for the determination of the four parabens in fruit juice samples was developed. Under the optimal conditions, the limits of detections of the four parabens were 0.028, 0.026, 0.021, and 0.026 mg/L, respectively. The precision expressed as relative standard deviation ranging from 2.6 to 8.9% was obtained. In all three fortified levels, recoveries of parabens were in the range of 72.5-89.4%. The proposed method has been applied to different fruit juice samples including orange juice, grape juice, apple juice and peach juice, and satisfactory results were obtained. PMID:27214157

  7. The preparation of magnetic molecularly imprinted nanoparticles for the recognition of bovine hemoglobin.

    PubMed

    Zhang, Min; Wang, Yuzhi; Jia, Xiaoping; He, Meizhi; Xu, Minli; Yang, Shan; Zhang, Cenjin

    2014-03-01

    The protein imprinted technique combining surface imprinting and nano-sized supports materials is an attractive strategy for protein recognition and rapid separation. In this work, we imprinted bovine hemoglobin (BHb) on magnetic nanoparticles. With itaconic acid (IA) and acrylamide (AAm) as the monomers, the experiment was carried out in aqueous media via surface-imprinting technique. The effects of initial concentration and adsorption time over the adsorption capacity of both imprinted and non-imprinted nanoparticles were analyzed. The maximum adsorption capability of imprinted nanoparticles was found to be 77.6 mg g(-1), which was 3.1-4.3 times higher than that of the non-imprinted nanoparticles prepared at the same conditions. This resulted in the successful formation of imprinting cavities. Moreover, in selective adsorption experiment and competitive batch rebinding test, imprinted nanoparticles exhibited a high specific recognition of the template protein over the non-imprinted protein. PMID:24468385

  8. Dual-template magnetic molecularly imprinted particles with multi-hollow structure for the detection of dicofol and chlorpyrifos-methyl.

    PubMed

    Yang, Tao; Feng, Shun; Lu, Yi; Yin, Chao; Wang, Jide

    2016-06-01

    In this work, a novel dual-template magnetic molecularly imprinted polymer particle for dicofol and chlorpyrifos-methyl was prepared through oil-in-water emulsifier-free emulsion technology. The resulting magnetic particles were characterized with electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction. It was found that as-prepared particles were well-shaped spheres with multi-hollow structures and of a size around 125 μm. Meanwhile it showed a good magnetic sensitivity. The results testified that multi-hollow magnetic molecularly imprinted polymers possessed excellent recognition capacity and fast kinetic binding behavior to the objective molecules. The maximum binding amounts toward dicofol and chlorpyrifos-methyl were 31.46 and 25.23 mg/g, respectively. The feasibility of the use of the particles as a solid-phase extraction sorbent was evaluated. Satisfactory recoveries ranging from 90.62 to 111.47 and 91.07 to 94.03% were obtained for dicofol and chlorpyrifos-methyl, respectively, spiked at three concentration levels from real samples. The Langmuir isotherm equation provided an excellent fit to the equilibrium sorption data of either dicofol or chlorpyrifos-methyl. It provided a novel way to advise dual-template magnetic molecularly imprinted polymer particles to adsorb pesticides with high selectivity. PMID:27119595

  9. MAGNETS

    DOEpatents

    Hofacker, H.B.

    1958-09-23

    This patent relates to nmgnets used in a calutron and more particularly to means fur clamping an assembly of magnet coils and coil spacers into tightly assembled relation in a fluid-tight vessel. The magnet comprises windings made up of an assembly of alternate pan-cake type coils and spacers disposed in a fluid-tight vessel. At one end of the tank a plurality of clamping strips are held firmly against the assembly by adjustable bolts extending through the adjacent wall. The foregoing arrangement permits taking up any looseness which may develop in the assembly of coils and spacers.

  10. Plastic protein microarray to investigate the molecular pathways of magnetic nanoparticle-induced nanotoxicity

    NASA Astrophysics Data System (ADS)

    Liu, Yingshuai; Li, Xuelian; Bao, Shujuan; Lu, Zhisong; Li, Qing; Li, Chang Ming

    2013-05-01

    Superparamagnetic iron oxide nanoparticles (SPIONs) (about 15 nm) were synthesized via a hydrothermal method and characterized by field emission scanning electron microscopy, transmission electron microscopy, dynamic light scattering, x-ray diffraction, and vibrating sample magnetometer. The molecular pathways of SPIONs-induced nanotoxicity was further investigated by protein microarrays on a plastic substrate from evaluation of cell viability, reactive oxygen species (ROS) generation and cell apoptosis. The experimental results reveal that 50 μg ml-1 or higher levels of SPIONs cause significant loss of cell viability, considerable generation of ROS and cell apoptosis. It is proposed that high level SPIONs could induce cell apoptosis via a mitochondria-mediated intrinsic pathway by activation of caspase 9 and caspase 3, an increase of the Bax/Bcl-2 ratio, and down-regulation of HSP70 and HSP90 survivor factors.

  11. Sequoias, Mavericks, Open Doors...Composing Joan Tower

    ERIC Educational Resources Information Center

    Allsup, Randall Everett

    2011-01-01

    This essay interview with Joan Tower is a meditation on the importance of composing, understood as a process larger than the making of new sound combinations or musical scores, suggesting that the compositional act is self-educative and self-forming. Tower's musical life, one of teaching and learning, one of composing and self-composing, is an…

  12. Molecular spintronics in mixed-valence magnetic dimers: the double-exchange blockade mechanism.

    PubMed

    Soncini, Alessandro; Mallah, Talal; Chibotaru, Liviu F

    2010-06-16

    We theoretically investigate the charge and spin transport through a binuclear Fe(III)Fe(III) iron complex connected to two metallic electrodes. During the transport process, the Fe(III)Fe(III) dimer undergoes a one-electron reduction (Coulomb blockade transport regime), leading to the reduced mixed-valence Fe(II) Fe(III) species. For such a system, the additional electron may be fully delocalized leading to the stabilization of the highest spin ground state S = 9/2 by the double exchange mechanism, while the original Fe(III)Fe(III) has usually an S = 0 spin ground state due to the antiferromagnetic exchange coupling between the two Fe(III) ions. Intuitively, the spin delocalization within the mixed-valence complex may be thought to favor charge and spin transport through the molecule between the two metallic electrodes. Contrary to such an intuitive concept, we find that the increased delocalization leads in fact to a blocking of the transport, if the exchange coupling interaction within the Fe(III)Fe(III) dimer is antiferromagnetic. This is due to the violation of the spin angular momentum conservation, where a change of half a unit of spin (DeltaS = 1/2) is allowed between two different redox states of the molecule. The result is explained in terms of a double-exchange blockade mechanism, triggered by the interplay between spin delocalization and antiferromagnetic coupling between the magnetic cores. Consequently, ferromagnetically coupled dimers are shown not to be affected by the double-exchange blockade mechanism. The situation is evocative of the onset and removal of giant magnetoresistance in the conductance of diamagnetic layers, as a function of the relative alignment of the magnetization of two weakly antiferromagnetically coupled ferromagnetic contacts. Numerical simulations accounting for the effect of vibronic coupling show that the spin current increases as a function of spin delocalization in Class I and Class II mixed-valence dimers. The signature

  13. Rovibrational molecular populations, atoms, and negative ions in H2 and D2 magnetic multicusp discharges

    NASA Astrophysics Data System (ADS)

    Pealat, M.; Taran, J.-P. E.; Bacal, M.; Hillion, F.

    1985-06-01

    Coherent anti-Stokes Raman scattering is applied to the study of rovibrational populations in magnetic multicusp H2 and D2 discharges. This subject is of interest to negative hydrogen-ion formation by volume plasma processes. The populations of high-lying rotational states (J greater than 5) in the vibrational levels v = 0, 1, and 2 are found to be significantly higher than expected from the Boltzmann law. In H2 the net populations of the first four vibrational levels follow approximately the Boltzmann law, with the vibrational temperature of 2390 K (in a 90 V-10 A discharge at 55 micro bar). In similar discharge conditions, the population of the state v = 3 in D2 is higher than expected from the Boltzmann law. In the presence of the discharge a deficiency in H2 and D2 molecule density was observed and was attributed to the possible presence of H and D atoms. This was verified by an independent measurement of the atomic fraction and temperature. The density of negative ions, measured by the photodetachment technique, is also reported.

  14. Utility of magnetic cell separation as a molecular sperm preparation technique.

    PubMed

    Said, Tamer M; Agarwal, Ashok; Zborowski, Maciej; Grunewald, Sonja; Glander, Hans-Juergen; Paasch, Uwe

    2008-01-01

    Assisted reproductive techniques (ARTs) have become the treatment of choice in many cases of infertility; however, the current success rates of these procedures remain suboptimal. Programmed cell death (apoptosis) most likely contributes to failed ART and to the decrease in sperm quality after cryopreservation. There is a likelihood that some sperm selected for ART will display features of apoptosis despite their normal appearance, which may be partially responsible for the low fertilization and implantation rates seen with ART. One of the features of apoptosis is the externalization of phosphatidylserine (PS) residues, which are normally present on the inner leaflet of the sperm plasma membrane. Colloidal superparamagnetic microbeads ( approximately 50 nm in diameter) conjugated with annexin V bind to PS and are used to separate dead and apoptotic spermatozoa by magnetic-activated cell sorting (MACS). Cells with externalized PS will bind to these microbeads, whereas nonapoptotic cells with intact membranes do not bind and could be used during ARTs. We have conducted a series of experiments to investigate whether the MACS technology could be used to improve ART outcomes. Our results clearly indicate that integrating MACS as a part of sperm preparation techniques will improve semen quality and cryosurvival rates by eliminating apoptotic sperm. Nonapoptotic spermatozoa prepared by MACS display higher quality in terms of routine sperm parameters and apoptosis markers. The higher sperm quality is represented by an increased oocyte penetration potential and cryosurvival rates. Thus, the selection of nonapoptotic spermatozoa by MACS should be considered to enhance ART success rates. PMID:18077822

  15. Synthesis route and three different core-shell impacts on magnetic characterization of gadolinium oxide-based nanoparticles as new contrast agents for molecular magnetic resonance imaging

    PubMed Central

    2012-01-01

    Despite its good resolution, magnetic resonance imaging intrinsically has low sensitivity. Recently, contrast agent nanoparticles have been used as sensitivity and contrast enhancer. The aim of this study was to investigate a new controlled synthesis method for gadolinium oxide-based nanoparticle preparation. For this purpose, diethyleneglycol coating of gadolinium oxide (Gd2O3-DEG) was performed using new supervised polyol route, and small particulate gadolinium oxide (SPGO) PEGylation was obtained with methoxy-polyethylene-glycol-silane (550 and 2,000 Da) coatings as SPGO-mPEG-silane550 and 2,000, respectively. Physicochemical characterization and magnetic properties of these three contrast agents in comparison with conventional Gd-DTPA were verified by dynamic light scattering transmission electron microscopy, Fourier transform infrared spectroscopy, inductively coupled plasma, X-ray diffraction, vibrating sample magnetometer, and the signal intensity and relaxivity measurements were performed using 1.5-T MRI scanner. As a result, the nanoparticle sizes of Gd2O3-DEG, SPGO-mPEG-silane550, and SPGO-mPEG-silane2000 could be reached to 5.9, 51.3, 194.2 nm, respectively. The image signal intensity and longitudinal (r1) and transverse relaxivity (r2) measurements in different concentrations (0.3 to approximately 2.5 mM), revealed the r2/r1 ratios of 1.13, 0.89, 33.34, and 33.72 for Gd-DTPA, Gd2O3-DEG, SPGO-mPEG-silane550, and SPGO-mPEG-silane2000, respectively. The achievement of new synthesis route of Gd2O3-DEG resulted in lower r2/r1 ratio for Gd2O3-DEG than Gd-DTPA and other previous synthesized methods by this and other groups. The smaller r2/r1 ratios of two PEGylated-SPGO contrast agents in our study in comparison with r2/r1 ratio of previous PEGylation (r2/r1 = 81.9 for mPEG-silane 6,000 MW) showed that these new three introduced contrast agents could potentially be proper contrast enhancers for cellular and molecular MR imaging. PMID:23033866

  16. Synthesis route and three different core-shell impacts on magnetic characterization of gadolinium oxide-based nanoparticles as new contrast agents for molecular magnetic resonance imaging

    NASA Astrophysics Data System (ADS)

    Azizian, Gholamreza; Riyahi-Alam, Nader; Haghgoo, Soheila; Moghimi, Hamid Reza; Zohdiaghdam, Reza; Rafiei, Behrooz; Gorji, Ensieh

    2012-10-01

    Despite its good resolution, magnetic resonance imaging intrinsically has low sensitivity. Recently, contrast agent nanoparticles have been used as sensitivity and contrast enhancer. The aim of this study was to investigate a new controlled synthesis method for gadolinium oxide-based nanoparticle preparation. For this purpose, diethyleneglycol coating of gadolinium oxide (Gd2O3-DEG) was performed using new supervised polyol route, and small particulate gadolinium oxide (SPGO) PEGylation was obtained with methoxy-polyethylene-glycol-silane (550 and 2,000 Da) coatings as SPGO-mPEG-silane550 and 2,000, respectively. Physicochemical characterization and magnetic properties of these three contrast agents in comparison with conventional Gd-DTPA were verified by dynamic light scattering transmission electron microscopy, Fourier transform infrared spectroscopy, inductively coupled plasma, X-ray diffraction, vibrating sample magnetometer, and the signal intensity and relaxivity measurements were performed using 1.5-T MRI scanner. As a result, the nanoparticle sizes of Gd2O3-DEG, SPGO-mPEG-silane550, and SPGO-mPEG-silane2000 could be reached to 5.9, 51.3, 194.2 nm, respectively. The image signal intensity and longitudinal ( r 1) and transverse relaxivity ( r 2) measurements in different concentrations (0.3 to approximately 2.5 mM), revealed the r 2/ r 1 ratios of 1.13, 0.89, 33.34, and 33.72 for Gd-DTPA, Gd2O3-DEG, SPGO-mPEG-silane550, and SPGO-mPEG-silane2000, respectively. The achievement of new synthesis route of Gd2O3-DEG resulted in lower r 2/ r 1 ratio for Gd2O3-DEG than Gd-DTPA and other previous synthesized methods by this and other groups. The smaller r 2/ r 1 ratios of two PEGylated-SPGO contrast agents in our study in comparison with r 2/ r 1 ratio of previous PEGylation ( r 2/ r 1 = 81.9 for mPEG-silane 6,000 MW) showed that these new three introduced contrast agents could potentially be proper contrast enhancers for cellular and molecular MR imaging.

  17. Utility of Magnetic Cell Separation as a Molecular Sperm Preparation Technique

    PubMed Central

    Said, Tamer M.; Agarwal, Ashok; Zborowski, Maciej; Grunewald, Sonja; Glander, Hans-Juergen; Paasch, Uwe

    2009-01-01

    Assisted reproductive techniques (ART) have become the treatment of choice in many cases of infertility; however the current success rates of these procedures remain suboptimal. Programmed cell death (apoptosis) most likely contributes to failed ART and to the decrease in sperm quality after cryopreservation. There is likelihood that some sperm selected for ART will display features of apoptosis despite their normal appearance, which may be partially responsible for the low fertilization and implantation rates seen with ART. One of the features of apoptosis is the externalization of phosphatidylserine (PS) residues, which are normally present on the inner leaflet of the sperm plasma membrane. Colloidal super-paramagnetic microbeads (~50 nm in diameter) conjugated with annexin-V bind to PS are used to separate dead and apoptotic spermatozoa by magnetic cell sorting (MACS). Cells with externalized PS will bind to these microbeads, while non-apoptotic cells with intact membranes do not bind and could be used during ART. We have conducted a series of experiments to investigate if the MACS technology could be used to improve ART outcomes. Our results clearly indicate that integrating MACS as a part of sperm preparation techniques will improve semen quality and cryosurvival rates by eliminating apoptotic sperm. Non-apoptotic spermatozoa prepared by MACS display higher quality in terms of routine sperm parameters and apoptosis markers. The higher sperm quality is represented by an increased oocyte penetration potential and cryosurvival rates. Thus, the selection of non-apoptotic spermatozoa by MACS should be considered to enhance ART success rates. PMID:18077822

  18. Magnetic resonance spectroscopy — Revisiting the biochemical and molecular milieu of brain tumors

    PubMed Central

    Verma, Ashish; Kumar, Ishan; Verma, Nimisha; Aggarwal, Priyanka; Ojha, Ritu

    2016-01-01

    Background Magnetic resonance spectroscopy (MRS) is an established tool for in-vivo evaluation of the biochemical basis of human diseases. On one hand, such lucid depiction of ‘live biochemistry’ helps one to decipher the true nature of the pathology while on the other hand one can track the response to therapy at sub-cellular level. Brain tumors have been an area of continuous interrogation and instigation for mankind. Evaluation of these lesions by MRS plays a crucial role in the two aspects of disease management described above. Scope of review Presented is an overview of the window provided by MRS into the biochemical aspects of brain tumors. We systematically visit each metabolite deciphered by MRS and discuss the role of deconvoluting the biochemical aspects of pathologies (here in context of brain tumors) in the disease management cycle. We further try to unify a radiologist's perspective of disease with that of a biochemist to prove the point that preclinical work is the mother of the treatment we provide at bedside as clinicians. Furthermore, an integrated approach by various scientific experts help resolve a query encountered in everyday practice. Major conclusions MR spectroscopy is an integral tool for evaluation and systematic follow-up of brain tumors. A deeper understanding of this technology by a biochemist would help in a swift and more logical development of the technique while a close collaboration with radiologist would enable definitive application of the same. General significance The review aims at inciting closer ties between the two specialists enabling a deeper understanding of this valuable technology. PMID:27158592

  19. Synthesis of magnetic molecularly imprinted polymers for the selective separation and determination of metronidazole in cosmetic samples.

    PubMed

    Liu, Min; Li, Xiao-Yan; Li, Jun-Jie; Su, Xiao-Meng; Wu, Zong-Yuan; Li, Peng-Fei; Lei, Fu-Hou; Tan, Xue-Cai; Shi, Zhan-Wang

    2015-05-01

    In this study, novel magnetic molecularly imprinted polymers (MMIPs) were developed as a sorbent for solid-phase extraction (SPE) and used for the selective separation of metronidazole (MNZ) in cosmetics; MNZ was detected by high-performance liquid chromatography (HPLC). First, magnetic Fe3O4 nanoparticles (NPs) were prepared by the co-precipitation of Fe(2+)and Fe(3+) ions in an ammonia solution; then oleic acid (OA) was modified onto the surface of Fe3O4NPs. Finally, the MMIP was prepared by aqueous suspension polymerization, involving the copolymerization of Fe3O4NPs@OA with MNZ as the template molecule, methacrylic acid (MAA) as the functional monomer, ethylene glycol maleic rosinate acrylate (EGMRA) as the cross-linking agent, and 2,2-azobisisobutyronitrile (AIBN) as the initiator. The MMIP materials showed high selective adsorption capacity and fast binding kinetics for MNZ; the maximum adsorption amount of the MMIP to MNZ was 46.7 mg/g. The assay showed a linear range from 0.1 to 20.0 μg/mL for MNZ with the correlation coefficient 0.999. The relative standard deviations (RSD) of intra- and inter-day ranging from 0.71 to 2.45% and from 1.06 to 5.20% were obtained. The MMIP can be applied to the enrichment and determination of MNZ in cosmetic products with the recoveries of spiked toner, powder, and cream cosmetic samples ranging from 90.6 to 104.2, 84.1 to 91.4, and 90.3 to 100.4%, respectively, and the RSD was <3.54%. PMID:25749799

  20. Nano-crystallization and magnetic mechanisms of Fe85Si2B8P4Cu1 amorphous alloy by ab initio molecular dynamics simulation

    NASA Astrophysics Data System (ADS)

    Wang, Yaocen; Takeuchi, Akira; Makino, Akihiro; Liang, Yunye; Kawazoe, Yoshiyuki

    2014-05-01

    Iron-based amorphous and nano-crystalline alloys have attracted a growing interest due to their potential in the application of magnetic coil production. However, fundamental understanding of the nano-crystallization mechanisms and magnetic features in the amorphous structure are still lack of knowledge. In the present work, we performed ab initio molecular dynamics simulation to clarify the ionic and electronic structure in atomic scale, and to derive the origin of the good magnetic property of Fe85Si2B8P4Cu1 amorphous alloy. The simulation gave a direct evidence of the Cu-P bonding preference in the amorphous alloy, which may promote nucleation in nano-crystallization process. On the other hand, the electron transfer and the band/orbital features in the amorphous alloy suggests that alloying elements with large electronegativity and the potential to expand Fe disordered matrix are preferred for enhancing the magnetization.

  1. Aqueous biphasic systems composed of ionic liquids and polypropylene glycol: insights into their liquid-liquid demixing mechanisms.

    PubMed

    Neves, Catarina M S S; Shahriari, Shahla; Lemus, Jesus; Pereira, Jorge F B; Freire, Mara G; Coutinho, João A P

    2016-07-27

    Novel ternary phase diagrams of aqueous biphasic systems (ABSs) composed of polypropylene glycol with an average molecular weight of 400 g mol(-1) (PPG-400) and a vast number of ionic liquids (ILs) were determined. The large array of selected ILs allowed us to evaluate their tuneable structural features, namely the effect of the anion nature, cation core and cation alkyl side chain length on the phase behaviour. Additional evidence on the molecular-level mechanisms which rule the phase splitting was obtained by (1)H NMR (Nuclear Magnetic Resonance) spectroscopy and by COSMO-RS (Conductor-like Screening Model for Real Solvents). Some systems, for which the IL-PPG-400 pairs are completely miscible, revealed to be of type "0". All data collected suggest that the formation of PPG-IL-based ABSs is controlled by the interactions established between the IL and PPG, contrarily to previous reports where a "salting-out" phenomenon exerted by the IL over the polymer in aqueous media was proposed as the dominant effect in ABS formation. The influence of temperature on the liquid-liquid demixing was also evaluated. In general, an increase in temperature favours the formation of an ABS in agreement with the lower critical solution temperature (LCST) phase behaviour usually observed in polymer-IL binary mixtures. Partition results of a dye (chloroanilic acid, in its neutral form) further confirm the possibility of tailoring the phases' polarities of IL-PPG-based ABSs. PMID:27405841

  2. Determination of absolute configuration in chiral solvents with nuclear magnetic resonance. A combined molecular dynamics/quantum chemical study.

    PubMed

    Kessler, Jiří; Dračínský, Martin; Bouř, Petr

    2015-05-28

    Nuclear magnetic resonance (NMR) spectroscopy is omnipresent in chemical analysis. However, chirality of a molecule can only be detected indirectly by NMR, e.g., by monitoring its interaction with another chiral object. In the present study, we investigate the spectroscopic behavior of chiral molecules placed into a chiral solvent. In this case, the solvent-solute interaction is much weaker, but the application range of such NMR analysis is wider than for a specific chemical shift agent. Two alcohols and an amine were used as model systems, and differences in NMR chemical shifts dependent on the solute-solvent chirality combination were experimentally detected. Combined quantum mechanic/molecular mechanic (QM/MM) computations were applied to reveal the underlying solute-solvent interactions. NMR shielding was calculated using the density functional theory (DFT). While the experimental observations could not be reproduced quantitatively, the modeling provided a qualitative agreement and detailed insight into the essence of solvent-solute chiral interactions. The potentials of mean force (PMF) obtained using molecular dynamics (MD) and the weighted histogram analysis method (WHAM) indicate that the chiral interaction brings about differences in conformer ratios, which are to a large extent responsible for the NMR shifts. The MD results also predicted slight changes in the solvent structure, including the radial distribution function (RDF), to depend on the solvent/solute chirality combination. Apart from the conformer distribution, an effective average solvent electrostatic field was tested as another major factor contributing to the chiral NMR effect. The possibility to simulate spectral effects of chiral solvents from the first-principles opens up the way to NMR spectroscopic determination of the absolute configuration for a larger scale of compounds, including those not forming specific complexes. PMID:25411905

  3. In Vivo Targeted Molecular Magnetic Resonance Imaging of Free Radicals in Diabetic Cardiomyopathy within Mice

    PubMed Central

    Towner, Rheal A.; Smith, Nataliya; Saunders, Debra; Carrizales, Jorge; Lupu, Florea; Silasi-Mansat, Robert; Ehrenshaft, Marilyn; Mason, Ronald P.

    2016-01-01

    Free radicals contribute to the pathogenesis of diabetic cardiomyopathy. We present a method to observe in vivo free radical events within murine diabetic cardiomyopathy. This study reports on in vivo imaging of protein/lipid radicals using molecular MRI (mMRI) and immuno-spin trapping (IST) in diabetic cardiac muscle. To detect free radicals in diabetic cardiomyopathy, streptozotocin (STZ)-exposed mice were given 5,5-dimethyl-pyrroline-N-oxide (DMPO) and administered an anti-DMPO probe (biotin-anti-DMPO antibody-albumin-Gd-DTPA). For controls, non-diabetic mice were given DMPO (non-disease control), and administered an anti-DMPO probe; or diabetic mice were given DMPO but administered a non-specific IgG contrast agent instead of the anti-DMPO probe. DMPO administration started at 7 weeks following STZ treatment for 5 days, and the anti-DMPO probe was administered at 8 weeks for MRI detection. MRI was used to detect a significant increase (p<0.001) in MR image signal intensity (SI) from anti-DMPO nitrone adducts in diabetic murine left-ventricular (LV) cardiac tissue, compared to controls. Regional increases in MR SI in the LV were found in apical and upper left areas (p<0.01 for both), compared to controls. The biotin moiety of the anti-DMPO probe was targeted with fluorescently-labeled streptavidin to locate the anti-DMPO probe in excised cardiac tissues, which indicating elevated fluorescence only in cardiac muscle from mice administered the anti-DMPO probe. Oxidized lipids and proteins were also found to be significantly elevated (p<0.05 for both) in diabetic cardiac muscle compared to controls. It can be concluded that diabetic mice have more heterogeneously distributed radicals in cardiac tissue than non-diabetic mice. PMID:25968951

  4. Structural, electrical, and magnetic properties of a series of molecular conductors based on BDT-TTP and lanthanoid nitrate complex anions (BDT-TTP = 2,5-Bis(1,3-dithiol-2-ylidene)-1,3,4,6-tetrathiapentalene).

    PubMed

    Cui, Hengbo; Otsuka, Takeo; Kobayashi, Akiko; Takeda, Naoya; Ishikawa, Masayasu; Misaki, Yohji; Kobayashi, Hayao

    2003-09-22

    The platelike crystals of a series of novel molecular conductors, which are based on the pi-donor molecules BDT-TTP (2,5-bis(1,3-dithiol-2-ylidene)-1,3,4,6-tetrathiapentalene) with a tetrathiapentalene skeleton and lanthanide nitrate complex anions [Ln(NO3)x](3-x)(Ln = La, Ce, (Pr), Tb, Dy, Ho, Er, Tm, Yb, Lu) with localized 4f magnetic moments, were synthesized. Except for the Ce complex, the salts were composed of (BDT-TTP)(5)[Ln(NO(3))(5)] and were isostructural. Even though the Ce crystal had a different composition, (BDT-TTP)(6)[Ce(NO(3))(6)](C(2)H(5)OH)(x)() (x approximately 3), the crystals all had the space group P(-)1. Although the X-ray examination of the Pr salts was insufficient, the existence of two modifications was suggested in these systems by preliminary X-ray examination. Previously, we reported the crystal structures and unique magnetic properties of (BDT-TTP)(5)[Ln(NO(3))(5)] (Ln = Sm, Eu, Nd, Gd). Thus, by combining the results of this work with previous one, we for the first time succeeded in obtaining a complete set of organic conductors composed of the identical pi-donors (BDT-TTP in this case) and all the lanthanide nitrate complex anions (except the complex with Pm(3+)). The crystals were all metallic down to 2 K. Electronic band structure calculations resulted in two-dimensional Fermi surfaces, which was consistent with their stable metallic states. Except for the Lu complex, which lacked paramagnetic moments, the magnetic susceptibilities were measured on the six heavy lanthanide ion complex salts by a SQUID magnetometer (Ln = Tb, Dy, Ho, Er, Tm, Yb). The large paramagnetic susceptibilities, which were caused by the paramagnetic moments of the rare-earth ions, were obtained. The Curie-Weiss law fairly accurately reproduced the temperature dependence of the magnetic susceptibilities of (BDT-TTP)(5)[Ho(NO(3))(5)] in the experimental temperature range (2-300 K) and a comparatively large Weiss temperature (|THETAV;|) was obtained (THETAV

  5. Kinetic effects on double hysteresis in spin crossover molecular magnets analyzed with first order reversal curve diagram technique

    SciTech Connect

    Stan, Raluca-Maria; Gaina, Roxana; Enachescu, Cristian E-mail: radu.tanasa@uaic.ro; Stancu, Alexandru; Tanasa, Radu E-mail: radu.tanasa@uaic.ro; Bronisz, Robert

    2015-05-07

    In this paper, we analyze two types of hysteresis in spin crossover molecular magnets compounds in the framework of the First Order Reversal Curve (FORC) method. The switching between the two stable states in these compounds is accompanied by hysteresis phenomena if the intermolecular interactions are higher than a threshold. We have measured the static thermal hysteresis (TH) and the kinetic light induced thermal hysteresis (LITH) major loops and FORCs for the polycrystalline Fe(II) spin crossover compound [Fe{sub 1−x}Zn{sub x}(bbtr){sub 3}](ClO{sub 4}){sub 2} (bbtr = 1,4-di(1,2,3-triazol-1-yl)butane), either in a pure state (x = 0) or doped with Zn ions (x = 0.33) considering different sweeping rates. Here, we use this method not only to infer the domains distribution but also to disentangle between kinetic and static components of the LITH and to estimate the changes in the intermolecular interactions introduced by dopants. We also determined the qualitative relationship between FORC distributions measured for TH and LITH.

  6. Solution-state structure and affinities of cyclodextrin: Fentanyl complexes by nuclear magnetic resonance spectroscopy and molecular dynamics simulation

    DOE PAGESBeta

    Mayer, Brian P.; Kennedy, Daniel J.; Lau, Edmond Y.; Valdez, Carlos A.

    2016-02-04

    Cyclodextrins (CDs) are investigated for their ability to form inclusion complexes with the analgesic fentanyl and three similar molecules: acetylfentanyl, thiofentanyl, and acetylthiofentanyl. Stoichiometry, binding strength, and complex structure are revealed through nuclear magnetic resonance (NMR) techniques and discussed in terms of molecular dynamics (MD) simulations. It was found that β-cyclodextrin is generally capable of forming the strongest complexes with the fentanyl panel. Two-dimensional NMR data and computational chemical calculations are used to derive solution-state structures of the complexes. Binding of the fentanyls to the CDs occurs at the amide phenyl ring, leaving the majority of the molecule solvated bymore » water, an observation common to all four fentanyls. This finding suggests a universal binding behavior, as the vast majority of previously synthesized fentanyl analogues contain this structural moiety. Furthermore, this baseline study serves as the most complete work on CD:fentanyl complexes to date and provides the insights into strategies for producing future generations of designer cyclodextrins capable of stronger and more selective complexation of fentanyl and its analogues.« less

  7. High molecular weight chitosan derivative polymeric micelles encapsulating superparamagnetic iron oxide for tumor-targeted magnetic resonance imaging

    PubMed Central

    Xiao, Yunbin; Lin, Zuan Tao; Chen, Yanmei; Wang, He; Deng, Ya Li; Le, D Elizabeth; Bin, Jianguo; Li, Meiyu; Liao, Yulin; Liu, Yili; Jiang, Gangbiao; Bin, Jianping

    2015-01-01

    Magnetic resonance imaging (MRI) contrast agents based on chitosan derivatives have great potential for diagnosing diseases. However, stable tumor-targeted MRI contrast agents using micelles prepared from high molecular weight chitosan derivatives are seldom reported. In this study, we developed a novel tumor-targeted MRI vehicle via superparamagnetic iron oxide nanoparticles (SPIONs) encapsulated in self-aggregating polymeric folate-conjugated N-palmitoyl chitosan (FAPLCS) micelles. The tumor-targeting ability of FAPLCS/SPIONs was demonstrated in vitro and in vivo. The results of dynamic light scattering experiments showed that the micelles had a relatively narrow size distribution (136.60±3.90 nm) and excellent stability. FAPLCS/SPIONs showed low cytotoxicity and excellent biocompatibility in cellular toxicity tests. Both in vitro and in vivo studies demonstrated that FAPLCS/SPIONs bound specifically to folate receptor-positive HeLa cells, and that FAPLCS/SPIONs accumulated predominantly in established HeLa-derived tumors in mice. The signal intensities of T2-weighted images in established HeLa-derived tumors were reduced dramatically after intravenous micelle administration. Our study indicates that FAPLCS/SPION micelles can potentially serve as safe and effective MRI contrast agents for detecting tumors that overexpress folate receptors. PMID:25709439

  8. Dynamic aspects of antibody:oligosaccharide complexes characterized by molecular dynamics simulations and saturation transfer difference nuclear magnetic resonance.

    PubMed

    Theillet, François-Xavier; Frank, Martin; Vulliez-Le Normand, Brigitte; Simenel, Catherine; Hoos, Sylviane; Chaffotte, Alain; Bélot, Frédéric; Guerreiro, Catherine; Nato, Farida; Phalipon, Armelle; Mulard, Laurence A; Delepierre, Muriel

    2011-12-01

    Carbohydrates are likely to maintain significant conformational flexibility in antibody (Ab):carbohydrate complexes. As demonstrated herein for the protective monoclonal Ab (mAb) F22-4 recognizing the Shigella flexneri 2a O-antigen (O-Ag) and numerous synthetic oligosaccharide fragments thereof, the combination of molecular dynamics simulations and nuclear magnetic resonance saturation transfer difference experiments, supported by physicochemical analysis, allows us to determine the binding epitope and its various contributions to affinity without using any modified oligosaccharides. Moreover, the methods used provide insights into ligand flexibility in the complex, thus enabling a better understanding of the Ab affinities observed for a representative set of synthetic O-Ag fragments. Additionally, these complementary pieces of information give evidence to the ability of the studied mAb to recognize internal as well as terminal epitopes of its cognate polysaccharide antigen. Hence, we show that an appropriate combination of computational and experimental methods provides a basis to explore carbohydrate functional mimicry and receptor binding. The strategy may facilitate the design of either ligands or carbohydrate recognition domains, according to needed improvements of the natural carbohydrate:receptor properties. PMID:21610193

  9. Molecular magnetic resonance imaging of acute vascular cell adhesion molecule-1 expression in a mouse model of cerebral ischemia.

    PubMed

    Hoyte, Lisa C; Brooks, Keith J; Nagel, Simon; Akhtar, Asim; Chen, Ruoli; Mardiguian, Sylvie; McAteer, Martina A; Anthony, Daniel C; Choudhury, Robin P; Buchan, Alastair M; Sibson, Nicola R

    2010-06-01

    The pathogenesis of stroke is multifactorial, and inflammation is thought to have a critical function in lesion progression at early time points. Detection of inflammatory processes associated with cerebral ischemia would be greatly beneficial in both designing individual therapeutic strategies and monitoring outcome. We have recently developed a new approach to imaging components of the inflammatory response, namely endovascular adhesion molecule expression on the brain endothelium. In this study, we show specific imaging of vascular cell adhesion molecule (VCAM)-1 expression in a mouse model of middle cerebral artery occlusion (MCAO), and a reduction in this inflammatory response, associated with improved behavioral outcome, as a result of preconditioning. The spatial extent of VCAM-1 expression is considerably greater than the detectable lesion using diffusion-weighted imaging (25% versus 3% total brain volume), which is generally taken to reflect the core of the lesion at early time points. Thus, VCAM-1 imaging seems to reveal both core and penumbral regions, and our data implicate VCAM-1 upregulation and associated inflammatory processes in the progression of penumbral tissue to infarction. Our findings indicate that such molecular magnetic resonance imaging (MRI) approaches could be important clinical tools for patient evaluation, acute monitoring of therapy, and design of specific treatment strategies. PMID:20087364

  10. Bonding, Backbonding, and Spin-Polarized Molecular Orbitals:Basis for Magnetism and Semiconducting Transport in V[TCNE]x~;;2

    SciTech Connect

    Kortright, Jeffrey B; Kortright, Jeffrey B; Lincoln, Derek M; Edelstein, Ruth Shima; Epstein, Arthur J

    2008-05-20

    X-ray absorption spectroscopy (XAS) and magnetic circular dichroism (MCD) at the V L2,3 and C and N K edges reveal bonding/backbonding interactions in films of the 400 K magnetic semiconductor V[TCNE]x~;;2. In V spectra, dxy-like orbitals are modeled assuming V2+ in an octahedral ligand field, while dz2 and dx2-y2 orbitals involved in strong covalent bonding cannot be modeled by atomic calculations. C and N MCD, and differences in XAS from neutral TCNE molecules, reveal spin-polarized molecular orbitals in V[TCNE]x~;;2 associated with backbonding interactions that yield its novel properties.

  11. A second-order planar gradiometer composed of concentric superconductive loops

    NASA Astrophysics Data System (ADS)

    Kuriki, S.; Isobe, Y.; Mizutani, Y.

    1987-01-01

    A planar gradiometer composed of three concentric superconductive loops is analyzed. The gradiometer performs the second derivative with a rotational symmetry in a form of ∂2Bz/∂r2, where r2=x2+y2. In response to the biomagnetic field generated by a current dipole, an isoflux line distribution which resembles well the magnetic field distribution is obtained. The location and the strength of the current-dipole source can readily be estimated from the isoflux pattern. Reduction of the magnetic field noise from distant sources with respect to the signal of a near source is calculated to be comparable with that of conventional axial gradiometers.

  12. Molecular diffusion in disordered interfacial media as probed by pulsed field gradients and nuclear magnetic relaxation dispersion

    NASA Astrophysics Data System (ADS)

    Levitz, P.; Korb, J.-P.; Bryant, R. G.

    1999-10-01

    We address the question of probing the fluid dynamics in disordered interfacial media by Pulsed field gradient (PFG) and Magnetic relaxation dispersion (MRD) techniques. We show that the PFG method is useful to separate the effects of morphology from the connectivity in disordered macroporous media. We propose simulations of molecular dynamics and spectral density functions, J(ω), in a reconstructed mesoporous medium for different limiting conditions at the pore surface. An algebraic form is found for J(ω) in presence of a surface diffusion and a local exploration of the pore network. A logarithmic form of J(ω) is found in presence of a pure surface diffusion. We present magnetic relaxation dispersion experiments (MRD) for water and acetone in calibrated mesoporous media to support the main results of our simulations and theories. Nous présentons les avantages respectifs des méthodes de gradients de champs pulsés (PFG) et de relaxation magnétique nucléaire en champs cyclés (MRD) pour sonder la dynamique moléculaire dans les milieux interfaciaux désordonnés. La méthode PFG est utile pour séparer la morphologie et la connectivité dans des milieux macroporeux. Des simulations de diffusion moléculaire et de densité spectrale J(ω) en milieux mésoporeux sont présentées dans différentes conditions limites aux interfaces des pores. Nous trouvons une forme de dispersion algébrique de J(ω) pour une diffusion de surface assistée d'une exploration locale du réseau de pores et une forme logarithmique dans le cas d'une simple diffusion de surface. Les résultats expérimentaux de la méthode MRD pour de l'eau et de l'acétone dans des milieux mésoporeux calibrés supportent les résultats principaux de nos simulations et théories.

  13. Magnetically Hard Fe3Se4 Embedded in Bi2Se3 Topological Insulator Thin Films Grown by Molecular Beam Epitaxy.

    PubMed

    Vasconcelos, Hugo Menezes do Nascimento; Eddrief, Mahmoud; Zheng, Yunlin; Demaille, Dominique; Hidki, Sarah; Fonda, Emiliano; Novikova, Anastasiia; Fujii, Jun; Torelli, Piero; Salles, Benjamin Rache; Vobornik, Ivana; Panaccione, Giancarlo; de Oliveira, Adilson Jesus Aparecido; Marangolo, Massimiliano; Vidal, Franck

    2016-01-26

    We investigated the structural, magnetic, and electronic properties of Bi2Se3 epilayers containing Fe grown on GaAs(111) by molecular beam epitaxy. It is shown that, in the window of growth parameters leading to Bi2Se3 epilayers with optimized quality, Fe atom clustering leads to the formation of FexSey inclusions. These objects have platelet shape and are embedded within Bi2Se3. Monoclinic Fe3Se4 is identified as the main secondary phase through detailed structural measurements. Due to the presence of the hard ferrimagnetic Fe3Se4 inclusions, the system exhibits a very large coercive field at low temperature and room temperature magnetic ordering. Despite this composite structure and the proximity of a magnetic phase, the surface electronic structure of Bi2Se3 is preserved, as shown by the persistence of a gapless Dirac cone at Γ. PMID:26653134

  14. The thickness-dependent dynamic magnetic property of Co{sub 2}FeAl films grown by molecular beam epitaxy

    SciTech Connect

    Qiao, Shuang; Nie, Shuaihua; Zhao, Jianhua; Zhang, Xinhui

    2014-10-27

    Co{sub 2}FeAl films with different thickness were prepared at different temperature by molecular beam epitaxy. Their dynamic magnetic property was studied by the time-resolved magneto-optical Kerr effect measurements. It is observed that the intrinsic damping factor of Co{sub 2}FeAl for [100] orientation is not related to the film's thickness and magnetic anisotropy as well as temperature at high-field regime, but increases with structural disorder of Co{sub 2}FeAl. The dominant contribution from the inhomogeneous magnetic anisotropy is revealed to be responsible for the observed extremely nonlinear and drastic field-dependent damping factors at low-field regime.

  15. Magnetismo Molecular (Molecular Magentism)

    SciTech Connect

    Reis, Mario S; Moreira Dos Santos, Antonio F

    2010-07-01

    The new synthesis processes in chemistry open a new world of research, new and surprising materials never before found in nature can now be synthesized and, as a wonderful result, observed a series of physical phenomena never before imagined. Among these are many new materials the molecular magnets, the subject of this book and magnetic properties that are often reflections of the quantum behavior of these materials. Aside from the wonderful experience of exploring something new, the theoretical models that describe the behavior these magnetic materials are, in most cases, soluble analytically, which allows us to know in detail the physical mechanisms governing these materials. Still, the academic interest in parallel this subject, these materials have a number of properties that are promising to be used in technological devices, such as in computers quantum magnetic recording, magnetocaloric effect, spintronics and many other devices. This volume will journey through the world of molecular magnets, from the structural description of these materials to state of the art research.

  16. Coding the Composing Process: A Guide for Teachers and Researchers.

    ERIC Educational Resources Information Center

    Perl, Sondra

    Designed for teachers and researchers interested in the study of the composing process, this guide introduces a method of analysis that can be applied to data from a range of different cases. Specifically, the guide offers a simple, direct coding scheme for describing the movements occurring during composing that involves four procedures: teaching…

  17. Composing in Public: The Ambient Audiences of a Writing Lab

    ERIC Educational Resources Information Center

    Hall, Matthew

    2015-01-01

    Although scholars have investigated the ways youths individually enact composing practices and the impact of audience on these practices, this study examines the impact of an audience physically present while composing in a shared, public space--an ambient audience. Blurring the line between traditional notions of audience and collaborator through…

  18. The Links between Handwriting and Composing for Y6 Children

    ERIC Educational Resources Information Center

    Medwell, Jane; Strand, Steve; Wray, David

    2009-01-01

    Although handwriting is often considered a matter of presentation, a substantial body of international research suggests that the role of handwriting in children's composing has been neglected. Automaticity in handwriting is now seen as of key importance in composing but this proposition is relatively untested in the UK and the assumption has been…

  19. Teaching Composing in Secondary School: A Case Study Analysis

    ERIC Educational Resources Information Center

    Bolden, Benjamin

    2009-01-01

    This article reports a case study of an experienced teacher of composing working with secondary school students in a large urban centre in Ontario, Canada. Results suggest authentic assignments connect student composing to the "real world", and so have meaning and life beyond the music classroom. Teachers can facilitate the development of…

  20. 16 CFR 301.20 - Fur products composed of pieces.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 16 Commercial Practices 1 2014-01-01 2014-01-01 false Fur products composed of pieces. 301.20 Section 301.20 Commercial Practices FEDERAL TRADE COMMISSION REGULATIONS UNDER SPECIFIC ACTS OF CONGRESS RULES AND REGULATIONS UNDER FUR PRODUCTS LABELING ACT Regulations § 301.20 Fur products composed...

  1. 16 CFR 301.20 - Fur products composed of pieces.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 16 Commercial Practices 1 2010-01-01 2010-01-01 false Fur products composed of pieces. 301.20 Section 301.20 Commercial Practices FEDERAL TRADE COMMISSION REGULATIONS UNDER SPECIFIC ACTS OF CONGRESS RULES AND REGULATIONS UNDER FUR PRODUCTS LABELING ACT Regulations § 301.20 Fur products composed of pieces. (a) Where fur products, or fur mats...

  2. 16 CFR 301.20 - Fur products composed of pieces.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 16 Commercial Practices 1 2011-01-01 2011-01-01 false Fur products composed of pieces. 301.20 Section 301.20 Commercial Practices FEDERAL TRADE COMMISSION REGULATIONS UNDER SPECIFIC ACTS OF CONGRESS RULES AND REGULATIONS UNDER FUR PRODUCTS LABELING ACT Regulations § 301.20 Fur products composed of pieces. (a) Where fur products, or fur mats...

  3. 16 CFR 301.20 - Fur products composed of pieces.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 16 Commercial Practices 1 2013-01-01 2013-01-01 false Fur products composed of pieces. 301.20 Section 301.20 Commercial Practices FEDERAL TRADE COMMISSION REGULATIONS UNDER SPECIFIC ACTS OF CONGRESS RULES AND REGULATIONS UNDER FUR PRODUCTS LABELING ACT Regulations § 301.20 Fur products composed...

  4. 16 CFR 301.20 - Fur products composed of pieces.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 16 Commercial Practices 1 2012-01-01 2012-01-01 false Fur products composed of pieces. 301.20 Section 301.20 Commercial Practices FEDERAL TRADE COMMISSION REGULATIONS UNDER SPECIFIC ACTS OF CONGRESS RULES AND REGULATIONS UNDER FUR PRODUCTS LABELING ACT Regulations § 301.20 Fur products composed...

  5. Syllabus for a Women Studies Course on Women Composers.

    ERIC Educational Resources Information Center

    Hayes, Deborah

    An upper division college-level course dealing with women composers for both music majors and nonmusic majors is outlined. The course provides an historical and analytical survey of western music through works composed by women, with emphasis on the 19th and 20th centuries. Students listen to music, participate in class discussions, and listen to…

  6. Hypermedia Composing: Questions Arising from Writing in Three Dimensions.

    ERIC Educational Resources Information Center

    Garthwait, Abigail

    2001-01-01

    Observes four sixth graders composing nonfiction projects for an integrated unit on Canadian studies, using hypermedia. Ponders issues raised when students compose in hypermedia including evaluating nontraditional projects, developing a sense of audience, conventions of the medium, use of visuals to convey information, engaged students, and…

  7. How Composers Approach Teaching Composition: Strategies for Music Teachers

    ERIC Educational Resources Information Center

    Randles, Clint; Sullivan, Mark

    2013-01-01

    Composition pedagogy is explored from the perspective of a composer and a music teacher educator in this article. The primary goal is to help practicing music teachers develop strategies that will encourage students to create original music. The authors provide reflection about the process of helping students compose on the basis of personal…

  8. Collaborative Composing in High School String Chamber Music Ensembles

    ERIC Educational Resources Information Center

    Hopkins, Michael T.

    2015-01-01

    The purpose of this study was to examine collaborative composing in high school string chamber music ensembles. Research questions included the following: (a) How do high school string instrumentalists in chamber music ensembles use verbal and musical forms of communication to collaboratively compose a piece of music? (b) How do selected variables…

  9. In Vivo Detection of Activated Platelets Allows Characterizing Rupture of Atherosclerotic Plaques with Molecular Magnetic Resonance Imaging in Mice

    PubMed Central

    Wiens, Kristina; Neudorfer, Irene; Zirlik, Andreas; Meissner, Mirko; Tilly, Peg; Charles, Anne-Laure; Bode, Christoph; Peter, Karlheinz; Fabre, Jean-Etienne

    2012-01-01

    Background Early and non-invasive detection of platelets on micro atherothrombosis provides a means to identify unstable plaque and thereby allowing prophylactic treatment towards prevention of stroke or myocardial infarction. Molecular magnetic resonance imaging (mMRI) of activated platelets as early markers of plaque rupture using targeted contrast agents is a promising strategy. In this study, we aim to specifically image activated platelets in murine atherothrombosis by in vivo mMRI, using a dedicated animal model of plaque rupture. Methods An antibody targeting ligand-induced binding sites (LIBS) on the glycoprotein IIb/IIIa-receptor of activated platelets was conjugated to microparticles of iron oxide (MPIO) to form the LIBS-MPIO contrast agent causing a signal-extinction in T2*-weighted MRI. ApoE−/− mice (60 weeks-old) were fed a high fat diet for 5 weeks. Using a small needle, the surface of their carotid plaques was scratched under blood flow to induce atherothrombosis. In vivo 9.4 Tesla MRI was performed before and repetitively after intravenous injection of either LIBS-MPIO versus non-targeted-MPIO. Results LIBS-MPIO injected animals showed a significant signal extinction (p<0.05) in MRI, corresponding to the site of plaque rupture and atherothrombosis in histology. The signal attenuation was effective for atherothrombosis occupying ≥2% of the vascular lumen. Histology further confirmed significant binding of LIBS-MPIO compared to control-MPIO on the thrombus developing on the surface of ruptured plaques (p<0.01). Conclusion in vivo mMRI detected activated platelets on mechanically ruptured atherosclerotic plaques in ApoE−/− mice with a high sensititvity. This imaging technology represents a unique opportunity for noninvasive detection of atherothrombosis and the identification of unstable atherosclerotic plaques with the ultimate promise to prevent strokes and myocardial infarctions. PMID:23028736

  10. The composing process of technical writers: A preliminary study

    NASA Technical Reports Server (NTRS)

    Mair, D.; Roundy, N.

    1981-01-01

    The assumption that technical writers compose as do other writers is tested. The literature on the composing process, not limited to the pure or applied sciences, was reviewed, yielding three areas of general agreement. The composing process (1) consists of several stages, (2) is reflexive, and (3) may be mastered by means of strategies. Data on the ways technical writers compose were collected, and findings were related to the three areas of agreement. Questionnaires and interviews surveying 70 writers were used. The disciplines represented by these writers included civil, chemical, agricultural, geological, mechanical, electrical, and petroleum engineering, chemistry, hydrology, geology, and biology. Those providing consulting services, or performing research. No technical editors or professional writers were surveyed, only technicians, engineers, and researchers whose jobs involved composing reports. Three pedagogical implications are included.

  11. Magnetic

    NASA Astrophysics Data System (ADS)

    Aboud, Essam; El-Masry, Nabil; Qaddah, Atef; Alqahtani, Faisal; Moufti, Mohammed R. H.

    2015-06-01

    The Rahat volcanic field represents one of the widely distributed Cenozoic volcanic fields across the western regions of the Arabian Peninsula. Its human significance stems from the fact that its northern fringes, where the historical eruption of 1256 A.D. took place, are very close to the holy city of Al-Madinah Al-Monawarah. In the present work, we analyzed aeromagnetic data from the northern part of Rahat volcanic field as well as carried out a ground gravity survey. A joint interpretation and inversion of gravity and magnetic data were used to estimate the thickness of the lava flows, delineate the subsurface structures of the study area, and estimate the depth to basement using various geophysical methods, such as Tilt Derivative, Euler Deconvolution and 2D modeling inversion. Results indicated that the thickness of the lava flows in the study area ranges between 100 m (above Sea Level) at the eastern and western boundaries of Rahat Volcanic field and getting deeper at the middle as 300-500 m. It also showed that, major structural trend is in the NW direction (Red Sea trend) with some minor trends in EW direction.

  12. Tunneling in Molecular Magnets

    NASA Astrophysics Data System (ADS)

    Vijayaraghavan, Avinash

    This thesis is about the tunneling dynamics of the Fe8 molecule in the presence of an environment. Although a lot of progress has been made experimentally to determine among many things the extremely small tunnel splitting energies of this macromolecule, the question of how the environment affects the molecule has still not been properly understood. It is the purpose of this thesis to put forward a coherent model for the decoherence processes that affect the Fe8 molecule. The decoherence allows us to treat the Fe8 molecules as classical objects and we can write down rate equations that determine the relaxation dynamics of the entire Fe8 solid. The theoretical predictions are in very good agreement with Monte-Carlo simulations of spherical samples. We believe that the model developed can be generalized to different geometries and also improvised to tackle the different experimental protocols that have been undertaken on these macroscopic molecules.

  13. Magnetic and transport properties of epitaxial thin film MgFe2O4 grown on MgO (100) by molecular beam epitaxy

    PubMed Central

    Wu, Han-Chun; Mauit, Ozhet; Coileáin, Cormac Ó; Syrlybekov, Askar; Khalid, Abbas; Mouti, Anas; Abid, Mourad; Zhang, Hong-Zhou; Abid, Mohamed; Shvets, Igor V.

    2014-01-01

    Magnesium ferrite is a very important magnetic material due to its interesting magnetic and electrical properties and its chemical and thermal stability. Here we report on the magnetic and transport properties of epitaxial MgFe2O4 thin films grown on MgO (001) by molecular beam epitaxy. The structural properties and chemical composition of the MgFe2O4 films were characterized by X-Ray diffraction and X-Ray photoelectron spectroscopy, respectively. The nonsaturation of the magnetization in high magnetic fields observed for M (H) measurements and the linear negative magnetoresistance (MR) curves indicate the presence of anti-phase boundaries (APBs) in MgFe2O4. The presence of APBs was confirmed by transmission electron microscopy. Moreover, post annealing decreases the resistance and enhances the MR of the film, suggesting migration of the APBs. Our results may be valuable for the application of MgFe2O4 in spintronics. PMID:25388355

  14. Microwave response to a magnetic phase transition in a molecular magnet based on [Mn12O12( MeCO2)16(H2O)4] clusters and tetramethyltetrathiafulvalene molecules

    NASA Astrophysics Data System (ADS)

    Morgunov, R. B.; Berdinskiĭ, V. L.; Dmitriev, A. I.; Tanimoto, Y.

    2007-05-01

    The electron paramagnetic resonance spectra of a molecular magnet synthesized from [Mn12O12( MeCO2)16(H2O)4] high-spin clusters and tetramethyltetrathiafulvalene donor organic molecules are investigated. It is revealed that, in the temperature range 5-7 K, there appears an additional signal against the background of the ferromagnetic resonance spectrum. The additional signal consists of a large number of lines and has a resonance nature, because it is observed in the well-reproduced narrow ranges of the constant magnetic field of the spectrometer (300-650 and 850-1300 Oe) at a frequency of 9.4152 GHz. The appearance of the additional signal at a temperature of 5 K is attended by a multiple increase in the magnetic susceptibility of the sample. There is a correlation between the spectral characteristics of the additional signal (such as the average amplitude, the spectral power, etc.) and the parameters of the ferromagnetic resonance spectrum (the resonance field, the linewidth, and the integrated intensity). The assumption is made that the additional signal is associated with the magnetic-field-induced transitions between spin states of Mn12 high-spin clusters for different orientations of crystallites with respect to the external magnetic field.

  15. Molecular Order in Buried Layers of TbPc2 Single-Molecule Magnets Detected by Torque Magnetometry.

    PubMed

    Perfetti, Mauro; Serri, Michele; Poggini, Lorenzo; Mannini, Matteo; Rovai, Donella; Sainctavit, Philippe; Heutz, Sandrine; Sessoli, Roberta

    2016-08-01

    Cantilever torque magnetometry is used to elucidate the orientation of magnetic molecules in thin films. The technique allows depth-resolved investigations by intercalating a layer of anisotropic magnetic molecules in a film of its isotropic analogues. The proof-of-concept is here demonstrated with the single-molecule magnet TbPc2 evidencing also an exceptional long-range templating effect on substrates coated by the organic molecule perylene-3,4,9,10-tetracarboxylic dianhydride. PMID:27232580

  16. Magnetic properties and hyperfine interactions in Cr8, Cr7Cd, and Cr7Ni molecular rings from 19F-NMR

    SciTech Connect

    Bordonali, L; Garlatti, E; Casadei, C M; Furukawa, Y; Lascialfari, A; Carretta, S; Troiani, F; Timco, G; Winpenny, R E; Borsa, F

    2014-04-14

    A detailed experimental investigation of the 19F nuclear magnetic resonance is made on single crystals of the homometallic Cr₈ antiferromagnetic molecular ring and heterometallic Cr₇Cd and Cr₇ Ni rings in the low temperature ground state. Since the F- ion is located midway between neighboring magnetic metal ions in the ring, the 19F-NMR spectra yield information about the local electronic spin density and ¹⁹F hyperfine interactions. In Cr8, where the ground state is a singlet with total spin S T = 0, the ¹⁹F-NMR spectra at 1.7 K and low external magnetic field display a single narrow line, while when the magnetic field is increased towards the first level crossing field, satellite lines appear in the ¹⁹F-NMR spectrum, indicating a progressive increase in the Boltzmann population of the first excited state S T = 1. In the heterometallic rings, Cr₇Cd and Cr₇ Ni, whose ground state is magnetic with S T = 3/2 and S T = 1/2, respectively, the ¹⁹F-NMR spectrum has a complicated structure which depends on the strength and orientation of the magnetic field, due to both isotropic and anisotropic transferred hyperfine interactions and classical dipolar interactions. From the 19F-NMR spectra in single crystals we estimated the transferred hyperfine constants for both the F⁻-Ni2⁺ and the F⁻-Cd2⁺ bonds. The values of the hyperfine constants compare well to the ones known for F⁻-Ni2⁺ in KNiF₃ and NiF₂ and for F⁻-Cr³⁺ in K₂NaCrF₆. The results are discussed in terms of hybridization of the 2s, 2p orbitals of the F⁻ ion and the d orbitals of the magnetic ion. Finally, we discuss the implications of our results for the electron-spin decoherence.

  17. Magnetic field effects in singlet-polaron quenching in molecularly doped fluorescence organic light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Xu, Kai; Ma, Dongge

    2014-08-01

    The magnetic field effects of electroluminescence (MEL) in 4-[dicyanomethylene]-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran(DCJTB) doped tri-(8-hydroxyquinoline)-aluminum (Alq3) based organic light-emitting diodes were investigated. A linear decrease in MEL with the increase of magnetic field was observed at high magnetic field (>20 mT) in this doping devices, which has been attributed to the singlet-polaron quenching effect. It was found that the singlet-polaron quenching is magnetic field dependent. Our results showed that singlet-polaron quenching commonly exists in fluorescence OLEDs and induces the linear decrease in MEL.

  18. Molecular magnetic resonance imaging of angiogenesis in vivo using polyvalent cyclic RGD-iron oxide microparticle conjugates.

    PubMed

    Melemenidis, Stavros; Jefferson, Andrew; Ruparelia, Neil; Akhtar, Asim M; Xie, Jin; Allen, Danny; Hamilton, Alastair; Larkin, James R; Perez-Balderas, Francisco; Smart, Sean C; Muschel, Ruth J; Chen, Xiaoyuan; Sibson, Nicola R; Choudhury, Robin P

    2015-01-01

    Angiogenesis is an essential component of tumour growth and, consequently, an important target both therapeutically and diagnostically. The cell adhesion molecule α(v)β(3) integrin is a specific marker of angiogenic vessels and the most prevalent vascular integrin that binds the amino acid sequence arginine-glycine-aspartic acid (RGD). Previous studies using RGD-targeted nanoparticles (20-50 nm diameter) of iron oxide (NPIO) for magnetic resonance imaging (MRI) of tumour angiogenesis, have identified a number of limitations, including non-specific extravasation, long blood half-life (reducing specific contrast) and low targeting valency. The aim of this study, therefore, was to determine whether conjugation of a cyclic RGD variant [c(RGDyK)], with enhanced affinity for α(v)β(3), to microparticles of iron oxide (MPIO) would provide a more sensitive contrast agent for imaging of angiogenic tumour vessels. Cyclic RGD [c(RGDyK)] and RAD [c(RADyK)] based peptides were coupled to 2.8 μm MPIO, and binding efficacy tested both in vitro and in vivo. Significantly greater specific binding of c(RGDyK)-MPIO to S-nitroso-n-acetylpenicillamine (SNAP)-stimulated human umbilical vein endothelial cells in vitro than PBS-treated cells was demonstrated under both static (14-fold increase; P < 0.001) and flow (44-fold increase; P < 0.001) conditions. Subsequently, mice bearing subcutaneous colorectal (MC38) or melanoma (B16F10) derived tumours underwent in vivo MRI pre- and post-intravenous administration of c(RGDyK)-MPIO or c(RADyK)-MPIO. A significantly greater volume of MPIO-induced hypointensities were found in c(RGDyK)-MPIO injected compared to c(RADyK)-MPIO injected mice, in both tumour models (P < 0.05). Similarly, administration of c(RGDyK)-MPIO induced a greater reduction in mean tumour T(2)* relaxation times than the control agent in both tumour models (melanoma P < 0.001; colorectal P < 0.0001). Correspondingly, MPIO density per tumour volume assessed

  19. Molecular Magnetic Resonance Imaging of Angiogenesis In Vivo using Polyvalent Cyclic RGD-Iron Oxide Microparticle Conjugates

    PubMed Central

    Melemenidis, Stavros; Jefferson, Andrew; Ruparelia, Neil; Akhtar, Asim M; Xie, Jin; Allen, Danny; Hamilton, Alastair; Larkin, James R; Perez-Balderas, Francisco; Smart, Sean C; Muschel, Ruth J; Chen, Xiaoyuan; Sibson, Nicola R; Choudhury, Robin P

    2015-01-01

    Angiogenesis is an essential component of tumour growth and, consequently, an important target both therapeutically and diagnostically. The cell adhesion molecule αvβ3 integrin is a specific marker of angiogenic vessels and the most prevalent vascular integrin that binds the amino acid sequence arginine-glycine-aspartic acid (RGD). Previous studies using RGD-targeted nanoparticles (20-50 nm diameter) of iron oxide (NPIO) for magnetic resonance imaging (MRI) of tumour angiogenesis, have identified a number of limitations, including non-specific extravasation, long blood half-life (reducing specific contrast) and low targeting valency. The aim of this study, therefore, was to determine whether conjugation of a cyclic RGD variant [c(RGDyK)], with enhanced affinity for αvβ3, to microparticles of iron oxide (MPIO) would provide a more sensitive contrast agent for imaging of angiogenic tumour vessels. Cyclic RGD [c(RGDyK)] and RAD [c(RADyK)] based peptides were coupled to 2.8 μm MPIO, and binding efficacy tested both in vitro and in vivo. Significantly greater specific binding of c(RGDyK)-MPIO to S-nitroso-n-acetylpenicillamine (SNAP)-stimulated human umbilical vein endothelial cells in vitro than PBS-treated cells was demonstrated under both static (14-fold increase; P < 0.001) and flow (44-fold increase; P < 0.001) conditions. Subsequently, mice bearing subcutaneous colorectal (MC38) or melanoma (B16F10) derived tumours underwent in vivo MRI pre- and post-intravenous administration of c(RGDyK)-MPIO or c(RADyK)-MPIO. A significantly greater volume of MPIO-induced hypointensities were found in c(RGDyK)-MPIO injected compared to c(RADyK)-MPIO injected mice, in both tumour models (P < 0.05). Similarly, administration of c(RGDyK)-MPIO induced a greater reduction in mean tumour T2* relaxation times than the control agent in both tumour models (melanoma P < 0.001; colorectal P < 0.0001). Correspondingly, MPIO density per tumour volume assessed immunohistochemically was

  20. Facility for low-temperature spin-polarized-scanning tunneling microscopy studies of magnetic/spintronic materials prepared in situ by nitride molecular beam epitaxy

    SciTech Connect

    Lin, Wenzhi; Foley, Andrew; Alam, Khan; Wang, Kangkang; Liu, Yinghao; Chen, Tianjiao; Pak, Jeongihm; Smith, Arthur R.

    2014-04-15

    Based on the interest in, as well as exciting outlook for, nitride semiconductor based structures with regard to electronic, optoelectronic, and spintronic applications, it is compelling to investigate these systems using the powerful technique of spin-polarized scanning tunneling microscopy (STM), a technique capable of achieving magnetic resolution down to the atomic scale. However, the delicate surfaces of these materials are easily corrupted by in-air transfers, making it unfeasible to study them in stand-alone ultra-high vacuum STM facilities. Therefore, we have carried out the development of a hybrid system including a nitrogen plasma assisted molecular beam epitaxy/pulsed laser epitaxy facility for sample growth combined with a low-temperature, spin-polarized scanning tunneling microscope system. The custom-designed molecular beam epitaxy growth system supports up to eight sources, including up to seven effusion cells plus a radio frequency nitrogen plasma source, for epitaxially growing a variety of materials, such as nitride semiconductors, magnetic materials, and their hetero-structures, and also incorporating in situ reflection high energy electron diffraction. The growth system also enables integration of pulsed laser epitaxy. The STM unit has a modular design, consisting of an upper body and a lower body. The upper body contains the coarse approach mechanism and the scanner unit, while the lower body accepts molecular beam epitaxy grown samples using compression springs and sample skis. The design of the system employs two stages of vibration isolation as well as a layer of acoustic noise isolation in order to reduce noise during STM measurements. This isolation allows the system to effectively acquire STM data in a typical lab space, which during its construction had no special and highly costly elements included, (such as isolated slabs) which would lower the environmental noise. The design further enables tip exchange and tip coating without

  1. Facility for low-temperature spin-polarized-scanning tunneling microscopy studies of magnetic/spintronic materials prepared in situ by nitride molecular beam epitaxy.

    PubMed

    Lin, Wenzhi; Foley, Andrew; Alam, Khan; Wang, Kangkang; Liu, Yinghao; Chen, Tianjiao; Pak, Jeongihm; Smith, Arthur R

    2014-04-01

    Based on the interest in, as well as exciting outlook for, nitride semiconductor based structures with regard to electronic, optoelectronic, and spintronic applications, it is compelling to investigate these systems using the powerful technique of spin-polarized scanning tunneling microscopy (STM), a technique capable of achieving magnetic resolution down to the atomic scale. However, the delicate surfaces of these materials are easily corrupted by in-air transfers, making it unfeasible to study them in stand-alone ultra-high vacuum STM facilities. Therefore, we have carried out the development of a hybrid system including a nitrogen plasma assisted molecular beam epitaxy/pulsed laser epitaxy facility for sample growth combined with a low-temperature, spin-polarized scanning tunneling microscope system. The custom-designed molecular beam epitaxy growth system supports up to eight sources, including up to seven effusion cells plus a radio frequency nitrogen plasma source, for epitaxially growing a variety of materials, such as nitride semiconductors, magnetic materials, and their hetero-structures, and also incorporating in situ reflection high energy electron diffraction. The growth system also enables integration of pulsed laser epitaxy. The STM unit has a modular design, consisting of an upper body and a lower body. The upper body contains the coarse approach mechanism and the scanner unit, while the lower body accepts molecular beam epitaxy grown samples using compression springs and sample skis. The design of the system employs two stages of vibration isolation as well as a layer of acoustic noise isolation in order to reduce noise during STM measurements. This isolation allows the system to effectively acquire STM data in a typical lab space, which during its construction had no special and highly costly elements included, (such as isolated slabs) which would lower the environmental noise. The design further enables tip exchange and tip coating without

  2. Stroke, music, and creative output: Alfred Schnittke and other composers.

    PubMed

    Zagvazdin, Yuri

    2015-01-01

    Alfred Schnittke (1934-1998), a celebrated Russian composer of the twentieth century, suffered from several strokes which affected his left cerebral hemisphere. The disease, however, did not diminish his musical talent. Moreover, he stated that his illness in a way facilitated his work. The composer showed amazingly high productivity after his first and second injuries of the central nervous system. The main topic of this chapter is the effect of strokes on Schnittke's output, creativity, and style of music. A brief biography of the composer with the chronology of his brain hemorrhages is included. In addition, the influence of cerebrovascular lesions on creative potential of other prominent composers such as Benjamin Britten, Jean Langlais, Vissarion Shebalin, Igor Stravinsky, and Ira Randall Thompson is discussed. PMID:25684289

  3. Low temperature, high magnetic field investigations of the nature of magnetism in the molecular semiconductor β- cobalt phthalocyanine (C32H16CoN8)

    NASA Astrophysics Data System (ADS)

    Wang (王正君), Zhengjun; Lee, M.; Choi, E. S.; Poston, J.; Seehra, M. S.

    2016-06-01

    Results from detailed investigations of the magnetic properties of a powder sample of β-CoPc for the temperatures T=0.4 K to 300 K and in magnetic fields H up to 90 kOe are reported. X-ray diffraction confirmed the β-phase and scanning electron microscopy showed plate-like morphology of the sample. For T>3 K, the data of magnetic susceptibility χ vs. T fit the Curie-Weiss (CW) law yielding θ=-2.5 K, μ=2.16 μB per Co2+ and g=2.49 for spin S=1/2 of the low spin-state of Co2+. However for T<3 K, the χ vs. T data deviates from the CW law yielding a peak in χ at Tmax=1.9 K. It is shown that the χ vs. T data from 0.4 K to 300 K fits well with the predictions of the Bonner-Fisher (BF) model for S=1/2 Heisenberg linear chain antiferromagnet with the Co2+-Co2+ exchange J/kB = -1.5 K (Ĥ=-2J Σ Si•Si+1). The data of magnetization M vs. H at T=1 K agrees with the predictions of the BF model with J/kB=-1.5 K, yielding saturation magnetization MS=12.16 emu/g above 60 kOe corresponding to complete alignment of the spins.

  4. Magnetic molecularly imprinted polymer nanoparticles based electrochemical sensor for the measurement of Gram-negative bacterial quorum signaling molecules (N-acyl-homoserine-lactones).

    PubMed

    Jiang, Hui; Jiang, Donglei; Shao, Jingdong; Sun, Xiulan

    2016-01-15

    We have developed a novel and economical electrochemical sensor to measure Gram-negative bacterial quorum signaling molecules (AHLs) using magnetic nanoparticles and molecularly imprinted polymer (MIP) technology. Magnetic molecularly imprinted polymers (MMIPs) capable of selectively absorbing AHLs were successfully synthesized by surface polymerization. The particles were deposited onto a magnetic carbon paste electrode (MGCE) surface, and characterized by electrochemical measurements. Differential Pulse Voltammetry (DPV) was utilized to record the oxidative current signal that is characteristic of AHL. The detection limit of this assay was determined to be 8×10(-10)molL(-1) with a linear detection range of 2.5×10(-9)molL(-1) to 1.0×10(-7)molL(-1). This Fe3O4@SiO2-MIP-based electrochemical sensor is a valuable new tool that allows quantitative measurement of Gram-negative bacterial quorum signaling molecules. It has potential applications in the fields of clinical diagnosis or food analysis with real-time detection capability, high specificity, excellent reproducibility, and good stability. PMID:26344904

  5. IV-VI diluted magnetic semiconductor Ge{sub 1-x}Mn{sub x}Te epilayer grown by molecular beam epitaxy

    SciTech Connect

    Fukuma, Y.; Goto, K.; Senba, S.; Miyawaki, S.; Asada, H.; Koyanagi, T.; Sato, H.

    2008-03-01

    Growth of the IV-VI diluted magnetic semiconductor Ge{sub 1-x}Mn{sub x}Te by molecular beam epitaxy is reported. The epitaxial growth of Ge{sub 1-x}Mn{sub x}Te (x=0.13) on BaF{sub 2} (111) with a GeTe buffer layer is confirmed by x-ray diffraction and reflection high-energy electron diffraction. The ferromagnetic order is clearly established by the magnetization and magnetotransport measurements. The Curie temperature of 100 K is obtained for the hole concentration of 7.86x10{sup 20} cm{sup -3}. The existence of the strong p-d exchange which gives rise to the ferromagnetic order is revealed by the hard x-ray photoemission measurements.

  6. Cold collisions of polyatomic molecular radicals with S-state atoms in a magnetic field: an ab initio study of He + CH2(X) collisions.

    PubMed

    Tscherbul, T V; Grinev, T A; Yu, H-G; Dalgarno, A; Kłos, Jacek; Ma, Lifang; Alexander, Millard H

    2012-09-14

    We develop a rigorous quantum mechanical theory for collisions of polyatomic molecular radicals with S-state atoms in the presence of an external magnetic field. The theory is based on a fully uncoupled space-fixed basis set representation of the multichannel scattering wave function. Explicit expressions are presented for the matrix elements of the scattering Hamiltonian for spin-1/2 and spin-1 polyatomic molecular radicals interacting with structureless targets. The theory is applied to calculate the cross sections and thermal rate constants for spin relaxation in low-temperature collisions of the prototypical organic molecule methylene [CH(2)(X(3)B(1))] with He atoms. To this end, two accurate three-dimensional potential energy surfaces (PESs) of the He-CH(2)(X(3)B(1)) complex are developed using the state-of-the-art coupled-cluster method including single and double excitations along with a perturbative correction for triple excitations and large basis sets. Both PESs exhibit shallow minima and are weakly anisotropic. Our calculations show that spin relaxation in collisions of CH(2), CHD, and CD(2) molecules with He atoms occurs at a much slower rate than elastic scattering over a large range of temperatures (1 μK-1 K) and magnetic fields (0.01-1 T), suggesting excellent prospects for cryogenic helium buffer-gas cooling of ground-state ortho-CH(2)(X(3)B(1)) molecules in a magnetic trap. Furthermore, we find that ortho-CH(2) undergoes collision-induced spin relaxation much more slowly than para-CH(2), which indicates that magnetic trapping can be used to separate nuclear spin isomers of open-shell polyatomic molecules. PMID:22979854

  7. Cold collisions of polyatomic molecular radicals with S-state atoms in a magnetic field: An ab initio study of He + CH2(X~) collisions

    NASA Astrophysics Data System (ADS)

    Tscherbul, T. V.; Grinev, T. A.; Yu, H.-G.; Dalgarno, A.; Kłos, Jacek; Ma, Lifang; Alexander, Millard H.

    2012-09-01

    We develop a rigorous quantum mechanical theory for collisions of polyatomic molecular radicals with S-state atoms in the presence of an external magnetic field. The theory is based on a fully uncoupled space-fixed basis set representation of the multichannel scattering wave function. Explicit expressions are presented for the matrix elements of the scattering Hamiltonian for spin-1/2 and spin-1 polyatomic molecular radicals interacting with structureless targets. The theory is applied to calculate the cross sections and thermal rate constants for spin relaxation in low-temperature collisions of the prototypical organic molecule methylene [CH_2(tilde{X}^3B_1)] with He atoms. To this end, two accurate three-dimensional potential energy surfaces (PESs) of the He-CH_2(tilde{X}^3B_1) complex are developed using the state-of-the-art coupled-cluster method including single and double excitations along with a perturbative correction for triple excitations and large basis sets. Both PESs exhibit shallow minima and are weakly anisotropic. Our calculations show that spin relaxation in collisions of CH2, CHD, and CD2 molecules with He atoms occurs at a much slower rate than elastic scattering over a large range of temperatures (1 μK-1 K) and magnetic fields (0.01-1 T), suggesting excellent prospects for cryogenic helium buffer-gas cooling of ground-state ortho-CH_2(tilde{X}^3B_1) molecules in a magnetic trap. Furthermore, we find that ortho-CH2 undergoes collision-induced spin relaxation much more slowly than para-CH2, which indicates that magnetic trapping can be used to separate nuclear spin isomers of open-shell polyatomic molecules.

  8. Transitions between quantum states of the spin-soliton structure in molecular magnets [Mn{( R/ S)- pn}]2[Mn{( R/ S)- pn}2(H2O)][Cr(CN)6]2

    NASA Astrophysics Data System (ADS)

    Morgunov, R. B.; Kirman, M. V.; Talantsev, A. D.

    2015-08-01

    A series of jumps of the magnetic moment (up to five jumps) with an amplitude of 1-10% of the saturation magnetization has been observed upon demagnetizing the molecular magnet [Mn{( R/ S)- pn}]2[Mn{( R/ S)- pn}2(H2O)][Cr(CN)6]2 in a narrow region of magnetic fields close to the coercive force. A decrease in the temperature leads to an increase in the critical magnetic field, which corresponds to the onset of the series of demagnetization jumps. The obtained experimental data agree with theoretical predictions on jump-like transitions between the magnetization curves upon attaining critical magnetic fields caused by the energy quantization of spin solitons.

  9. Particle alignment and clustering in sheared granular materials composed of platy particles.

    PubMed

    Boton, Mauricio; Estrada, Nicolas; Azéma, Emilien; Radjaï, Farhang

    2014-11-01

    By means of molecular dynamics simulations, we investigate the texture and local ordering in sheared packings composed of cohesionless platy particles. The morphology of large packings of platy particles in quasistatic equilibrium is complex due to the combined effects of local nematic ordering of the particles and anisotropic orientations of contacts between particles. We find that particle alignment is strongly enhanced by the degree of platyness and leads to the formation of face-connected clusters of exponentially decaying size. Interestingly, due to dynamics in continuous shearing, this ordering phenomenon emerges even in systems composed of particles of very low platyness differing only slightly from spherical shape. The number of clusters is an increasing function of platyness. However, at high platyness the proportion of face-face interactions is too low to allow for their percolation throughout the system. PMID:25412821

  10. Molecular Spintronics using Molecular Nanomagnets

    NASA Astrophysics Data System (ADS)

    Wernsdorfer, Wolfgang

    2009-03-01

    A revolution in electronics is in view, with the contemporary evolution of two novel disciplines, spintronics and molecular electronics. A fundamental link between these two fields can be established using molecular magnetic materials and, in particular, single-molecule magnets [1], which combine the classic macroscale properties of a magnet with the quantum properties of a nanoscale entity. The resulting field, molecular spintronics aims at manipulating spins and charges in electronic devices containing one or more molecules. In this context, we want to fabricate, characterize and study molecular devices (molecular spin-transistor, molecular spin-valve and spin filter, molecular double-dot devices, carbon nanotube nano-SQUIDs, etc.) in order to read and manipulate the spin states of the molecule and to perform basic quantum operations. The talk will discuss this--still largely unexplored--field and present our the first important results [2,3].[4pt] [1] L. Bogani & W. Wernsdorfer, Nature Mat. 7, 179 (2008).[0pt] [2] J.-P. Cleuziou, W. Wernsdorfer, V. Bouchiat, T. Ondarcuhu, M. Monthioux, Nature Nanotech. 1, 53-59 (2006).[0pt] [3] N. Roch, S. Florens, V. Bouchiat, W. Wernsdorfer, F. Balestro, Nature 453, 633 (2008).

  11. A membrane page composer - Further developments. [for holographic memory system

    NASA Technical Reports Server (NTRS)

    Cosentino, L. S.; Stewart, W. C.

    1974-01-01

    Membrane page composers were made and were evaluated in a simulated holographic optical memory system. Calculated and experimentally determined electromechanical and optical characteristics of the circular membrane light valves used on the arrays are shown to be in close agreement. Several operating prototypes of 8 x 8 and 16 x 16 elements were produced. Measurements were made of switching time, optical contrast, and dynamic storage time of many cells on the devices. Digital patterns were stored in the arrays. The performance required of the page composer as a component of an optical memory system is considered. The fabrication techniques used can be easily extended to larger arrays.

  12. Polarized Neutron Diffraction as a Tool for Mapping Molecular Magnetic Anisotropy: Local Susceptibility Tensors in Co(II) Complexes.

    PubMed

    Ridier, Karl; Gillon, Béatrice; Gukasov, Arsen; Chaboussant, Grégory; Cousson, Alain; Luneau, Dominique; Borta, Ana; Jacquot, Jean-François; Checa, Ruben; Chiba, Yukako; Sakiyama, Hiroshi; Mikuriya, Masahiro

    2016-01-11

    Polarized neutron diffraction (PND) experiments were carried out at low temperature to characterize with high precision the local magnetic anisotropy in two paramagnetic high-spin cobalt(II) complexes, namely [Co(II) (dmf)6 ](BPh4 )2 (1) and [Co(II) 2 (sym-hmp)2 ](BPh4 )2 (2), in which dmf=N,N-dimethylformamide; sym-hmp=2,6-bis[(2-hydroxyethyl)methylaminomethyl]-4-methylphenolate, and BPh4 (-) =tetraphenylborate. This allowed a unique and direct determination of the local magnetic susceptibility tensor on each individual Co(II) site. In compound 1, this approach reveals the correlation between the single-ion easy magnetization direction and a trigonal elongation axis of the Co(II) coordination octahedron. In exchange-coupled dimer 2, the determination of the individual Co(II) magnetic susceptibility tensors provides a clear outlook of how the local magnetic properties on both Co(II) sites deviate from the single-ion behavior because of antiferromagnetic exchange coupling. PMID:26728231

  13. One-step synthesis of mussel-inspired molecularly imprinted magnetic polymer as stationary phase for chip-based open tubular capillary electrochromatography enantioseparation.

    PubMed

    Wang, Xiao-Ni; Liang, Ru-Ping; Meng, Xiang-Ying; Qiu, Jian-Ding

    2014-10-01

    A facile approach for preparation of molecularly imprinted polymers was developed and successfully used as chiral stationary phase for rapid enantioseparation by open tubular capillary electrochromatography (OT-CEC). In this work, molecularly imprinted polymers were one-step prepared employing Fe3O4 nanoparticles (NPs) as the supporting substrate and dopamine as the functional monomer. By simply mixing Fe3O4 NPs with template molecules in a weak alkaline solution of dopamine, a thin adherent polydopamine (PDA) film imprinted with template molecules was formed by the self-polymerization of dopamine on the surface of Fe3O4 NPs. After extracting the embedded template molecules, the produced imprinted Fe3O4@PDA NPs are of three dimensional shape of template molecules favoring high binding capacity and magnetism property for easy manipulation. The imprinted Fe3O4@PDA NPs prepared with l-tryptophan, l-tyrosine, Gly-l-Phe or s-ofloxacin as template molecules were packed in the PDMS microchannel via magnetic field as novel stationary phase for the successful enantioseparation of corresponding target analysts. In addition, the imprinted Fe3O4@PDA NPs-based OT-CEC system exhibited excellent reproducibility, stability and repeatability, which provides a powerful protocol for separation enantiomers within a short analytical time and opens up a promising avenue for high-throughput screening of chiral compounds. PMID:25182855

  14. Spatial Habitat Features Derived from Multiparametric Magnetic Resonance Imaging Data Are Associated with Molecular Subtype and 12-Month Survival Status in Glioblastoma Multiforme

    PubMed Central

    Lee, Joonsang; Narang, Shivali; Martinez, Juan; Rao, Ganesh; Rao, Arvind

    2015-01-01

    One of the most common and aggressive malignant brain tumors is Glioblastoma multiforme. Despite the multimodality treatment such as radiation therapy and chemotherapy (temozolomide: TMZ), the median survival rate of glioblastoma patient is less than 15 months. In this study, we investigated the association between measures of spatial diversity derived from spatial point pattern analysis of multiparametric magnetic resonance imaging (MRI) data with molecular status as well as 12-month survival in glioblastoma. We obtained 27 measures of spatial proximity (diversity) via spatial point pattern analysis of multiparametric T1 post-contrast and T2 fluid-attenuated inversion recovery MRI data. These measures were used to predict 12-month survival status (≤12 or >12 months) in 74 glioblastoma patients. Kaplan-Meier with receiver operating characteristic analyses was used to assess the relationship between derived spatial features and 12-month survival status as well as molecular subtype status in patients with glioblastoma. Kaplan-Meier survival analysis revealed that 14 spatial features were capable of stratifying overall survival in a statistically significant manner. For prediction of 12-month survival status based on these diversity indices, sensitivity and specificity were 0.86 and 0.64, respectively. The area under the receiver operating characteristic curve and the accuracy were 0.76 and 0.75, respectively. For prediction of molecular subtype status, proneural subtype shows highest accuracy of 0.93 among all molecular subtypes based on receiver operating characteristic analysis. We find that measures of spatial diversity from point pattern analysis of intensity habitats from T1 post-contrast and T2 fluid-attenuated inversion recovery images are associated with both tumor subtype status and 12-month survival status and may therefore be useful indicators of patient prognosis, in addition to providing potential guidance for molecularly-targeted therapies in

  15. Molecular design of one dimensional magnetic FeNi3 nanochains and their application in oil removal

    NASA Astrophysics Data System (ADS)

    Bhattacharya, Kakoli; Gogoi, Monika; Deb, Pritam

    2016-05-01

    One dimensional magnetic nanochains (MNCs) of FeNi3 alloy is developed by reducing iron and nickel salts in ethylene glycol in a hydrothermal environment without the use of any external magnetic field or template. The as prepared nanochains, comprised of nanospheres of diameter 350 nm, exhibit an extraordinary length of around 2 µm. The he self assembly of the FeNi3 nanospheres is attributed to strong dipolar interaction. Hydrophilic to hydrophobic surface transformation achieved by using trimethoxysilane and stearic acid, also introduces oleophilicity to the MNCs. After surface modification, the hydrophobic and oleophilic MNCs shows quick and selective absorption of oils from water surface under the influence of magnetic field.

  16. The Composing Processes of Unskilled Writers at the College Level.

    ERIC Educational Resources Information Center

    Perl, Sondra

    This paper uses five case studies of unskilled writers at the college level to provide insights into the composing process. Each student's writing process was tape-recorded and observed by the instructor in four sessions. The tapes and written observations were charted and analyzed for exhibited behavior patterns in comparison to the written…

  17. To Compose: Teaching Writing in the High School.

    ERIC Educational Resources Information Center

    Newkirk, Thomas, Ed.

    The twelve essays in this collection, selected by leading teacher educators, explore the composition process and composition instruction. The first essay, "Toward Righting Writing" by Arthur Diagon, serves as a prologue while the second section, "getting started," consists of "A Way of Writing" by William Stafford, "Understanding Composing" by…

  18. The Composing Process: A Critical Review of Some Recent Studies.

    ERIC Educational Resources Information Center

    Crismore, Avon

    Six of the 10 existing research studies that attempt to characterize the composing process by examining certain components and behaviors are critically reviewed in this paper. For each study, the aims and data gathering and sampling procedures are described, and the findings, interpretations, design, and rationale of the research are critically…

  19. Teaching Effective Communication Skills with ACE: Analyzing, Composing, & Evaluating

    ERIC Educational Resources Information Center

    Snyder, Lisa Gueldenzoph; Shwom, Barbara

    2011-01-01

    Most business communication classes teach students to use a writing process to compose effective documents. Students practice the process by applying it to various types of writing with various purposes-reports, presentations, bad news letters, persuasive memos, etc. However, unless students practice that process in other contexts outside of the…

  20. Circularly polarized printed arrays composed of strip dipoles and slots

    NASA Astrophysics Data System (ADS)

    Ito, Koichi

    1987-04-01

    This paper presents circularly polarized printed arrays composed of strip dipoles and slots (CP-PASS). A design method for CP-PASS is described on the basis of its equivalent circuit model. A linear array with a Chebyshev pattern and a middle-gain planar array are designed and measured at S band.

  1. Beyond the Enthymeme: Sorites, Critical Thinking, and the Composing Process.

    ERIC Educational Resources Information Center

    Hill, Carolyn

    A teacher presents a writing exercise designed to facilitate audience-directed, critical thinking during the process of composing, that starts students thinking in terms of sorites and enthymemes. Students first read a CIA manual, "Psychological Operations in Guerrilla Warfare," that instructs the Contra guerrillas in illegal acts and then free…

  2. Performing Stenographic Activities. Compose Correspondence. Student's Manual and Instructor's Manual.

    ERIC Educational Resources Information Center

    Harrison, Pam

    Supporting performance objective 71 of the V-TECS (Vocational-Technical Education Consortium of States) Secretarial Catalog, both a set of student materials and an instructor's manual on composing correspondence are included in this packet. (The packet is the fourth in a set of four on performing stenographic activities--CE 016 973-976.) The…

  3. Composing with New Technology: Teacher Reflections on Learning Digital Video

    ERIC Educational Resources Information Center

    Bruce, David L.; Chiu, Ming Ming

    2015-01-01

    This study explores teachers' reflections on their learning to compose with new technologies in the context of teacher education and/or teacher professional development. English language arts (ELA) teachers (n = 240) in 15 courses learned to use digital video (DV), completed at least one DV group project, and responded to open-ended survey…

  4. "Convince Me!" Valuing Multimodal Literacies and Composing Public Service Announcements

    ERIC Educational Resources Information Center

    Selfe, Richard J.; Selfe, Cynthia L.

    2008-01-01

    For some teachers, the increasing attention to digital and multimodal composing in English and Language Arts classrooms has brought into sharp relief the profession's investment in print as the primary means of expression. Although new forms of communication that combine words, still and moving images, and animation have begun to dominate digital…

  5. How One Class with One Computer Composed Music

    ERIC Educational Resources Information Center

    Siegel, Jack

    2004-01-01

    Music composition is a rewarding activity for students. Through composition, teachers not only address National Standard 4 (composing and arranging music within specified guidelines), but also cover other areas of the music curriculum such as singing, notation, improvisation, form, style, tempo, dynamics, music vocabulary, and assessment. During…

  6. When Did Classic Composers Make Their Best Work?

    ERIC Educational Resources Information Center

    Franses, Philip Hans

    2016-01-01

    This Research Note shows that classic composers created their best works when they were at a similar age when creators in other domains did their best work, namely when they were at an age that represented around 60% of their life span. This finding is very similar to earlier results for painters and authors.

  7. The Poetics of Computers: Composing Relationships with Technology.

    ERIC Educational Resources Information Center

    Longo, Bernadette; Reiss, Donna; Selfe, Cynthia L.; Young, Art

    2003-01-01

    Describes a course with three primary goals: to help students reflect on the complex relationship between humans and technology; to reflect on students' responsibility for shaping this relationship in contemporary contexts; and to provide opportunities within which to practice composing this relationship in personal terms. Concludes that in such…

  8. Quiet Grove in a Savage Garden: A Composer's Bicameral Reality

    ERIC Educational Resources Information Center

    Bohlen, Donald

    2004-01-01

    This author, a composer, states that music has been the primal generator of his existence and the definition of living creatively; and that understanding the bicameral reality of creativity through a study of the nature of consciousness involves a symbiotic host of disciplines. In the study of the occurrence of "creativity," consciousness as well…

  9. Composing Songs for Teaching Science to College Students

    ERIC Educational Resources Information Center

    Yee Pinn Tsin, Isabel

    2015-01-01

    Recent studies have shown that songs may enhance learning as they function as mnemonic devices to increase memorability. In this research, songs based on the more difficult subtopics in Chemistry were composed, encompassing many formulas, equations and facts to be remembered. This technique of song composition can be used in any subject, any point…

  10. Conversations with American Composers: Ev Grimes Interviews William Schuman.

    ERIC Educational Resources Information Center

    Grimes, Ev

    1986-01-01

    Born in 1910, composer William Schuman has been deeply involved with music education, first as a college professor and later a president of the Julliard School of Music. In this interview, Schuman talks about what music means to him, his teaching career, and music in general education. (RM)

  11. Conversations with American Composers: Ev Grimes Interviews Otto Luening.

    ERIC Educational Resources Information Center

    Grimes, Ev

    1986-01-01

    Otto Luening, one of the pioneers in the development of tape composition, talks about a variety of topics, including the education of musicians, the relationship between composer and teacher, his class for non-music majors, the musical training a teacher should have, and changes needed in music education. (RM)

  12. Readers as Writers Composing from Sources. Technical Report No. 18.

    ERIC Educational Resources Information Center

    Spivey, Nancy Nelson; King, James R.

    A study of discourse synthesis (readers/writers composing new texts by selecting, organizing, and connecting content from source texts) examined the performance of accomplished and less accomplished readers in the 6th, 8th, and 10th grades on a report-writing task. Over a 3-day period 60 English/language arts students wrote informational reports…

  13. Facile and controllable one-step fabrication of molecularly imprinted polymer membrane by magnetic field directed self-assembly for electrochemical sensing of glutathione.

    PubMed

    Zhu, Wanying; Jiang, Guoyi; Xu, Lei; Li, Bingzhi; Cai, Qizhi; Jiang, Huijun; Zhou, Xuemin

    2015-07-30

    Based on magnetic field directed self-assembly (MDSA) of the ternary Fe3O4@PANI/rGO nanocomposites, a facile and controllable molecularly imprinted electrochemical sensor (MIES) was fabricated through a one-step approach for detection of glutathione (GSH). The ternary Fe3O4@PANI/rGO nanocomposites were obtained by chemical oxidative polymerization and intercalation of Fe3O4@PANI into the graphene oxide layers via π-π stacking interaction, followed by reduction of graphene oxide in the presence of hydrazine hydrate. In molecular imprinting process, the pre-polymers, including GSH as template molecule, Fe3O4@PANI/rGO nanocomposites as functional monomers and pyrrole as both cross-linker and co-monomer, was assembled through N-H hydrogen bonds and the electrostatic interaction, and then was rapidly oriented onto the surface of MGCE under the magnetic field induction. Subsequently, the electrochemical GSH sensor was formed by electropolymerization. In this work, the ternary Fe3O4@PANI/rGO nanocomposites could not only provide available functionalized sites in the matrix to form hydrogen bond and electrostatic interaction with GSH, but also afford a promoting network for electron transfer. Moreover, the biomimetic sensing membrane could be controlled more conveniently and effectively by adjusting the magnetic field strength. The as-prepared controllable sensor showed good stability and reproducibility for the determination of GSH with the detection limit reaching 3 nmol L(-1) (S/N = 3). In addition, the highly sensitive and selective biomimetic sensor has been successfully used for the clinical determination of GSH in biological samples. PMID:26320634

  14. Effect of molecular diffusion on the spin dynamics of a micellized radical pair in low magnetic fields studied by Monte Carlo simulation.

    PubMed

    Miura, Tomoaki; Murai, Hisao

    2015-06-01

    Magnetic field effect is a powerful tool to study dynamics and kinetics of radical pairs (RPs), which are one of the most important intermediates for organic photon-energy conversion reactions. However, quantitative discussion regarding the relationship between the modulation of interelectron interactions and spin dynamics at low magnetic fields (<10 mT) is still an open question. We have studied the spin dynamics of a long-lived RP in a micelle by newly developed Monte Carlo simulation, in which fluctuations of the exchange and magnetic dipolar interactions by in-cage diffusion are directly introduced to the time-domain spin dynamics calculation. State-dependent relaxation/dephasing times of a few to a few tens of nanoseconds are obtained by simulations without hyperfine interactions (HFIs) as a function of the mutual diffusion constant (∼10(-6) cm(2)/s). Simulations with the HFIs exhibit incoherent singlet-triplet (S-T) mixings resulting from interplay between the HFIs and the fluctuating spin-spin interactions. The experimentally observed incoherent S-T mixing of ∼20 ns at 3 mT for a singlet-born RP in a sodium dodecyl sulfate micelle is reproduced by the simulation with reasonable diffusion coefficients. The computational method developed here contributes to quantitative detection of molecular motion that governs the recombination efficiency of RPs. PMID:25942039

  15. Determination of roxithromycin from human plasma samples based on magnetic surface molecularly imprinted polymers followed by liquid chromatography-tandem mass spectromer.

    PubMed

    Ding, Jie; Zhang, Fengshuang; Zhang, Xiaopan; Wang, Long; Wang, Changjia; Zhao, Qi; Xu, Yang; Ding, Lan; Ren, Nanqi

    2016-05-15

    In this paper, a simple and reproducible method for the determination of roxithromycin in human plasma samples is proposed. The surface magnetic molecularly imprinted polymers (MMIPs) were utilized as sorbent. Roxithromycin was used as imprinted compound. The experimental results showed that the MMIPs had high affinity and selectivity toward roxithromycin. The extraction process was carried out in a single step by mixing the extraction solvent, MMIPs and human plasma samples by vortex. When the extraction process was completed, the MMIPs adsorbed the analyte were separated from the sample matrix by an external magnet due to the magnetism. The analyte eluted from the MMIPs was analysed by liquid chromatography-tandem mass spectrometry. Some main factors affecting the extraction of roxithromycin such as the amount of MMIPs, extraction solvent, extraction time, washing and elution conditions were optimized in this study. The calibration curve obtained by analyzing matrix-matched standards showed excellent linear relationship (r(2)=0.9997) in the concentration range of 10-1000ngmL(-1). The limit of detection and quantification obtained were 3.8 and 9.8ngmL(-1), respectively. The relative standard deviations of intra- and inter-day obtained were in the range of 3.9 %-5.5 % and 2.9 %-4.6 % with the recoveries ranging from 86.5 % to 91.5 %. PMID:26300321

  16. Smart Magnetic Nanosensors Synthesized through Layer-by-Layer Deposition of Molecular Beacons for Noninvasive and Longitudinal Monitoring of Cellular mRNA.

    PubMed

    Wang, Min; Hou, Xiaochun; Wiraja, Christian; Sun, Libo; Xu, Zhichuan J; Xu, Chenjie

    2016-03-01

    Noninvasive and longitudinal monitoring of gene expression in living cells is essential for understanding and monitoring cellular activities. Herein, a smart magnetic nanosensor is constructed for the real-time, noninvasive, and longitudinal monitoring of cellular mRNA expression through the layer-by-layer deposition of molecular beacons (MBs) and polyethylenimine on the iron oxide nanoparticles. The loading of MBs, responsible for the signal intensity and the tracking time, was easily tuned with the number of layers incorporated. The idea was first demonstrated with the magnetic nanosensors for glyceraldehyde-3-phosphate dehydrogenase (GAPDH) mRNA, which was efficiently internalized into the cells under the influence of magnetic field. This nanosensor allowed the continuous monitoring of the cellular GAPDH mRNA expression for 1 month. Then this platform was further utilized to incorporate two kinds of MBs for alkaline phosphatase (ALP) and GAPDH mRNAs, respectively. The multifunctional nanosensors permitted the simultaneous monitoring of the reference gene (GAPDH mRNA) and the early osteogenic differentiation marker (ALP mRNA) expression. When the fluorescence signal ratio between ALP mRNA MBs and GAPDH mRNA MBs was taken, the dynamic osteogenic differentiation process of MSCs was accurately monitored. PMID:26878880

  17. Study of Molecular Conformation and Activity-Related Properties of Lipase Immobilized onto Core-Shell Structured Polyacrylic Acid-Coated Magnetic Silica Nanocomposite Particles.

    PubMed

    Esmaeilnejad-Ahranjani, Parvaneh; Kazemeini, Mohammad; Singh, Gurvinder; Arpanaei, Ayyoob

    2016-04-01

    A facile approach for the preparation of core-shell structured poly(acrylic acid) (PAA)-coated Fe3O4 cluster@SiO2 nanocomposite particles as the support materials for the lipase immobilization is reported. Low- or high-molecular-weight (1800 and 100 000, respectively) PAA molecules were covalently attached onto the surface of amine-functionalized magnetic silica nanoacomposite particles. The successful preparation of particles were verified by scanning transmission electron microscopy (STEM), X-ray diffraction (XRD), vibrating sample magnetometer (VSM), thermogravimetric analysis (TGA), zeta potential measurement, and Fourier-transform infrared (FTIR) techniques. Once lipase is covalently immobilized onto the particles with an average diameter of 210 ± 50 nm, resulting from high binding sites concentrations on the low- and high-molecular-weight PAA-coated particles, high lipase immobilization efficiencies (86.2% and 89.9%, respectively), and loading capacities (786 and 816 mg g(-1), respectively) are obtained. Results from circular dichroism (CD) analysis and catalytic activity tests reveal an increase in the β-sheet content of lipase molecules upon immobilization, along with an enhancement in their activities and stabilities. The lipases immobilized onto the low- and high-molecular-weight PAA-coated particles show maximum activities at 55 and 50 °C, respectively, which are ∼28% and ∼15% higher than that of the free lipase at its own optimum temperature (40 °C), respectively. The immobilized lipases exhibit excellent performance at broader temperature and pH ranges and high thermal and storage stabilities, as well as superior reusability. These prepared magnetic nanocomposite particles can be offered as suitable support materials for efficient immobilization of enzymes and improvement of the immobilized enzymes properties. PMID:26986897

  18. Molecular weight dependence of segmental alignment in a sheared polymer melt: A deuterium nuclear magnetic resonance investigation

    NASA Astrophysics Data System (ADS)

    Cormier, Ryan J.; Callaghan, Paul T.

    2002-06-01

    2H NMR quadrupole interaction spectroscopy has been used to measure the molecular weight dependence of poly(dimethylsiloxane) chain deformation under shear in a cylindrical Couette cell while NMR velocimetry has been used to directly measure shear rates. The signals were acquired from a perdeuterated benzene probe molecule, which provides a motionally averaged sampling of the entire segmental ensemble. We have measured the dependence on shear rate of the SXX (velocity), SYY (velocity gradient), and SZZ (vorticity) elements of the segmented alignment tensor, fitting the data using the standard Doi-Edwards theory and modified to allow for convected constraint release. Our results suggest that the tube disengagement times scale as molecular weight to the power 3.5±0.1, consistent with the usual 3.4 power law. Our velocimetry measurements indicate a reproducible and consistent slip occurring at high molecular weights (>1 M Dalton), a phenomenon which is independently observed in a lower than expected chain deformation.

  19. Computer-aided design and synthesis of magnetic molecularly imprinted polymers with high selectivity for the removal of phenol from water.

    PubMed

    Yang, Wenming; Liu, Lukuan; Ni, Xiaoni; Zhou, Wei; Huang, Weihong; Liu, Hong; Xu, Wanzhen

    2016-02-01

    A molecular simulation method was introduced to compute the phenol-monomer pre-assembled system of a molecularly imprinted polymer. The interaction type and intensity between phenol and monomer were evaluated by combining binding energy and charge transfer with complex conformation. The simulation results indicate that interaction energies are simultaneously affected by the type of monomer and the ratio between phenol and monomers. At the same time, we considered that by increasing the amount of functional monomer is not always better for preparing molecularly imprinter polymers. In this study, three kinds of novel magnetic phenol-imprinted polymers with favorable specific adsorption effects were prepared by the surface imprinting technique combined with atom transfer radical polymerization. Various measures were selected to characterize the structure and morphology to obtain the optimal polymer. The characterization results show that the optimal polymer has suitable features for further adsorption process. A series of static adsorption experiments were conducted to analyze its adsorption performance, which follows the Elovich model from the kinetic analysis and the Sips equation from the isothermal analysis. To further verify the reliability and accuracy of the simulation results, the effects of different monomers on the adsorption selectivity were also determined. They display higher selectivity towards phenol than 4-nitrophenol.The results from the simulation of the pre-assembled complexes are in reasonable agreement with those from the experiment. PMID:26648327

  20. Composing Texts, Composing Lives.

    ERIC Educational Resources Information Center

    Perl, Sondra

    1994-01-01

    Using composition, reader response, critical, and feminist theories, a teacher demonstrates how adult students respond critically to literary texts and how teachers must critically analyze the texts of their teaching practice. Both students and teachers can use writing to bring their experiences to interpretation. (SK)

  1. Environmental influence on the single-molecule magnet behavior of [Mn(III)6Cr(III)]3+: molecular symmetry versus solid-state effects.

    PubMed

    Hoeke, Veronika; Heidemeier, Maik; Krickemeyer, Erich; Stammler, Anja; Bögge, Hartmut; Schnack, Jürgen; Postnikov, Andrei; Glaser, Thorsten

    2012-10-15

    The structural, spectroscopic, and magnetic properties of a series of [Mn(III)(6)Cr(III)](3+) (= [{(talen(t-Bu(2)))Mn(III)(3)}(2){Cr(III)(CN)(6)}](3+)) compounds have been investigated by single-crystal X-ray diffraction (XRD), Fourier transform infrared (FT-IR) and electronic absorption spectroscopy, elemental analysis, electro spray ionization-mass spectrometry (ESI-MS) and matrix-assisted laser desorption ionization-mass spectrometry (MALDI-MS), cyclic voltammetry, AC and DC magnetic measurements, as well as theoretical analysis. The crystal structures obtained with [Cr(III)(CN)(6)](3-) as a counterion exhibit (quasi-)one-dimensional (1D) chains formed by hydrogen-bonded (1) or covalently linked (2) trications and trianions. The rod-shaped anion lactate enforces a rod packing of the [Mn(III)(6)Cr(III)](3+) complexes in the highly symmetric space group R3[overline] (3) with a collinear arrangement of the molecular S(6) axes. Incorporation of the spherical anion BPh(4)(-) leads to less-symmetric crystal structures (4-6) with noncollinear orientations of the [Mn(III)(6)Cr(III)](3+) complexes, as evidenced by the angle between the approximate molecular C(3) axes taking no specific values in the range of 2°-69°. AC magnetic measurements on freshly isolated crystals (1a and 3a-6a), air-dried crystals (3b-6b), and vacuum-dried powder samples (3c-6c) indicate single-molecule magnet (SMM) behavior for all samples with U(eff) values up to 28 K. The DC magnetic data are analyzed by a full-matrix diagonalization of the appropriate spin-Hamiltonian including isotropic exchange, zero-field splitting, and Zeeman interaction, taking into account the relative orientation of the D-tensors. Simulations for 3a-6a and 3c-6c indicate a weak antiferromagnetic exchange between the Mn(III) ions in the trinuclear subunits (J(Mn-Mn) = -0.70 to -0.85 cm(-1), Ĥ(ex) = -2∑(i

  2. Modeling and Composing Scenario-Based Requirements with Aspects

    NASA Technical Reports Server (NTRS)

    Araujo, Joao; Whittle, Jon; Ki, Dae-Kyoo

    2004-01-01

    There has been significant recent interest, within the Aspect-Oriented Software Development (AOSD) community, in representing crosscutting concerns at various stages of the software lifecycle. However, most of these efforts have concentrated on the design and implementation phases. We focus in this paper on representing aspects during use case modeling. In particular, we focus on scenario-based requirements and show how to compose aspectual and non-aspectual scenarios so that they can be simulated as a whole. Non-aspectual scenarios are modeled as UML sequence diagram. Aspectual scenarios are modeled as Interaction Pattern Specifications (IPS). In order to simulate them, the scenarios are transformed into a set of executable state machines using an existing state machine synthesis algorithm. Previous work composed aspectual and non-aspectual scenarios at the sequence diagram level. In this paper, the composition is done at the state machine level.

  3. A Design for Composing and Extending Vehicle Models

    NASA Technical Reports Server (NTRS)

    Madden, Michael M.; Neuhaus, Jason R.

    2003-01-01

    The Systems Development Branch (SDB) at NASA Langley Research Center (LaRC) creates simulation software products for research. Each product consists of an aircraft model with experiment extensions. SDB treats its aircraft models as reusable components, upon which experiments can be built. SDB has evolved aircraft model design with the following goals: 1. Avoid polluting the aircraft model with experiment code. 2. Discourage the copy and tailor method of reuse. The current evolution of that architecture accomplishes these goals by reducing experiment creation to extend and compose. The architecture mechanizes the operational concerns of the model's subsystems and encapsulates them in an interface inherited by all subsystems. Generic operational code exercises the subsystems through the shared interface. An experiment is thus defined by the collection of subsystems that it creates ("compose"). Teams can modify the aircraft subsystems for the experiment using inheritance and polymorphism to create variants ("extend").

  4. Magnetic and Gilbert damping properties of L21-Co2FeAl film grown by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Qiao, Shuang; Nie, Shuaihua; Zhao, Jianhua; Huo, Yan; Wu, Yizheng; Zhang, Xinhui

    2013-10-01

    Co2FeAl film with L21 structure was prepared. Its magnetic and Gilbert damping properties were studied by ferromagnetic resonance (FMR) and time-resolved magneto-optical Kerr effect (TR-MOKE), respectively. It is observed that the apparent damping parameter decreases drastically with increasing magnetic field at low field regime and eventually becomes a constant value of 0.004 at high field regime by TR-MOKE measurements. A Gilbert damping parameter of 0.008 in the hard axis by FMR measurement has also been obtained, which is comparable with that extracted from TR-MOKE measurements at low external field, indicating the extrinsic damping processes involved in the low field regime.

  5. Assembly of single molecular magnets from dinuclear to 2D Dy-compounds with significant change of relaxation energy barriers.

    PubMed

    Chen, Zhi; Fang, Ming; Kang, Xiao-Min; Hou, Yin-Ling; Zhao, Bin

    2016-01-01

    A dinuclear Dy(III) compound (1) was structurally and magnetically characterized, displaying a single-molecule magnet (SMM) behavior with a relaxation energy barrier of 21(1) K. Interestingly, by only adding a suitable substituent on the ligand in , as an SMM building unit, can be further assembled into a two-dimensional (2D) framework (2), which possesses a typical SMM behavior and a high relaxation energy barrier of 68(2) K. The result implied that the assembly of an SMM can effectively tune the energy barrier. To our knowledge, a cluster-based SMM assembled into a new 2D framework with SMM behavior is seldom reported. PMID:26634233

  6. Soft elasticity in solids composed of ellipse-shaped particles

    NASA Astrophysics Data System (ADS)

    Mkhonta, Simiso K.; Vernon, Daniel; Elder, K. R.; Grant, Martin

    2013-03-01

    We present a method for studying the influence of internal rotational degrees of freedom on the elastic properties of crystals composed of ellipsoidal particles. We derive the conditions under which a stretched-triangular lattice of ellipsoidal particles can exhibit a vanishing shear modulus. Analytical predictions are confirmed with numerical calculations. Numerical results also show that internal rotational modes can delay the proliferation of dislocations in the plastic regime.

  7. 1. General view, outbuildings. The seed house composed of the ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    1. General view, outbuildings. The seed house composed of the greenhouse, a storeroom (shed), a classroom (over a former ice pit), and a kitchen (over a cellar)-stands on the right. The barn roof is visible at center and the gift shop (former stable) stands on the left (Note the carved stone posts framing the gateway). - John Bartram House & Garden, Greenhouse, 54th Street & LIndbergh Boulevard, Philadelphia, Philadelphia County, PA

  8. Measuring image quality in overlapping areas of panoramic composed images

    NASA Astrophysics Data System (ADS)

    Mitjà, Carles; Bover, Toni; Escofet, Jaume

    2012-06-01

    Several professional photographic applications uses the merging of consecutive overlapping images in order to obtain bigger files by means of stitching techniques or extended field of view (FOV) for panoramic images. All of those applications share the fact that the final composed image is obtained by overlapping the neighboring areas of consecutive individual images taken as a mosaic or a series of tiles over the scene, from the same point of view. Any individual image taken with a given lens can carry residual aberrations and several of them will affect more probably the borders of the image frame. Furthermore, the amount of distortion aberration present in the images of a given lens will be reversed in position for the two overlapping areas of a pair of consecutive takings. Finally, the different images used in composing the final one have corresponding overlapping areas taken with different perspective. From all the previously stated can be derived that the software employed must remap all the pixel information in order to resize and match image features in those overlapping areas, providing a final composed image with the desired perspective projection. The work presented analyse two panoramic format images taken with a pair of lenses and composed by means of a state of the art stitching software. Then, a series of images are taken to cover an FOV three times the original lens FOV, the images are merged by means of a software of common use in professional panoramic photography and the final image quality is evaluated through a series of targets positioned in strategic locations over the whole taking field of view. That allows measuring the resulting Resolution and Modulation Transfer Function (MTF). The results are shown compared with the previous measures on the original individual images.

  9. Molecular orbital (SCF-X-α-SW) theory of Fe2+-Mn3+, Fe3+-Mn2+, and Fe3+-Mn3+ charge transfer and magnetic exchange in oxides and silicates

    USGS Publications Warehouse

    Sherman, David M.

    1990-01-01

    Metal-metal charge-transfer and magnetic exchange interactions have important effects on the optical spectra, crystal chemistry, and physics of minerals. Previous molecular orbital calculations have provided insight on the nature of Fe2+-Fe3+ and Fe2+-Ti4+ charge-transfer transitions in oxides and silicates. In this work, spin-unrestricted molecular orbital calculations on (FeMnO10) clusters are used to study the nature of magnetic exchange and electron delocalization (charge transfer) associated with Fe3+-Mn2+, Fe3+-Mn3+, and Fe2+-Mn3+ interactions in oxides and silicates. 

  10. Coordination Complexes of a Neutral 1,2,4-Benzotriazinyl Radical Ligand: Synthesis, Molecular and Electronic Structures, and Magnetic Properties.

    PubMed

    Morgan, Ian S; Mansikkamäki, Akseli; Zissimou, Georgia A; Koutentis, Panayiotis A; Rouzières, Mathieu; Clérac, Rodolphe; Tuononen, Heikki M

    2015-10-26

    A series of d-block metal complexes of the recently reported coordinating neutral radical ligand 1-phenyl-3-(pyrid-2-yl)-1,4-dihydro-1,2,4-benzotriazin-4-yl (1) was synthesized. The investigated systems contain the benzotriazinyl radical 1 coordinated to a divalent metal cation, Mn(II) , Fe(II) , Co(II) , or Ni(II) , with 1,1,1,5,5,5-hexafluoroacetylacetonato (hfac) as the auxiliary ligand of choice. The synthesized complexes were fully characterized by single-crystal X-ray diffraction, magnetic susceptibility measurements, and electronic structure calculations. The complexes [Mn(1)(hfac)2 ] and [Fe(1)(hfac)2 ] displayed antiferromagnetic coupling between the unpaired electrons of the ligand and the metal cation, whereas the interaction was found to be ferromagnetic in the analogous Ni(II) complex [Ni(1)(hfac)2 ]. The magnetic properties of the complex [Co(1)(hfac)2 ] were difficult to interpret owing to significant spin-orbit coupling inherent to octahedral high-spin Co(II) metal ion. As a whole, the reported data clearly demonstrated the favorable coordinating properties of the radical 1, which, together with its stability and structural tunability, make it an excellent new building block for establishing more complex metal-radical architectures with interesting magnetic properties. PMID:26493885

  11. A design study of a photorefractive page composer

    NASA Technical Reports Server (NTRS)

    1975-01-01

    A laboratory demonstration and preliminary system analysis of a page composer designed to have the dual advantages of low optical loss and small size, were reported. The current page composer is optically addressed and functions by virtue of optically induced refractive index changes in the active material. Laboratory demonstrations of the device were successfully performed using 10 x 10 bit and 128 x 128 bit data arrays. It was established that the only significant obstacle to the construction of a brass-board model working at megabit data rates is the lack of sensitivity of the photorefractive materials which were considered during the course of this study. Possible materials for future consideration are the photoplastics. While they have more than the required sensitivity, their stability and suitability for double exposure holography was not investigated. If a sufficiently sensitive material is found, then the photorefractive page composer could be built to perform in a highly efficient fashion which would result in a overall reduction of the size of the memory system and an easing of the requirements upon the sensitivity of the holographic recording material.

  12. Relevant interactions of antimicrobial iron chelators and membrane models revealed by nuclear magnetic resonance and molecular dynamics simulations.

    PubMed

    Coimbra, João T S; Moniz, Tânia; Brás, Natércia F; Ivanova, Galya; Fernandes, Pedro A; Ramos, Maria J; Rangel, Maria

    2014-12-18

    The dynamics and interaction of 3-hydroxy-4-pyridinone fluorescent iron chelators, exhibiting antimicrobial properties, with biological membranes were evaluated through NMR and molecular dynamics simulations. Both NMR and MD simulation results support a strong interaction of the chelators with the lipid bilayers that seems to be strengthened for the rhodamine containing compounds, in particular for compounds that include ethyl groups and a thiourea link. For the latter type of compounds the interaction reaches the hydrophobic core of the lipid bilayer. The molecular docking and MD simulations performed for the potential interaction of the chelators with DC-SIGN receptors provide valuable information regarding the cellular uptake of these compounds since the results show that the fluorophore fragment of the molecular framework is essential for an efficient binding. Putting together our previous and present results, we put forward the hypothesis that all the studied fluorescent chelators have access to the cell, their uptake occurs through different pathways and their permeation properties correlate with a better access to the cell and its compartments and, consequently, with the chelators antimicrobial properties. PMID:25482538

  13. Molecular imprinting and immobilization of cellulase onto magnetic Fe3O4@SiO2 nanoparticles.

    PubMed

    Li, Yue; Wang, Xiang-Yu; Zhang, Rui-Zhuo; Zhang, Xiao-Yun; Liu, Wei; Xu, Xi-Ming; Zhang, Ye-Wang

    2014-04-01

    Supermagnetic Fe3O4@SiO2 nanoparticles were molecular-imprinted prepared with cellulase as the template. The molecular imprinted nanoparticles were used as support to immobilization of cellulase. The transmission electron microscopy confirmed the core-shell structure and revealed that the size of the nanoparticles was around 10 nm. It was observed that cellulase was immobilized on the nanoparticles successfully from the Fourier transform infrared spectra. The adsorption of cellulase on the nanoparticles was specific and rapid. A high immobilization efficiency of 95% was achieved after the optimization. At 70 degrees C, the half-life of the immobilized cellulase was 3.3-fold of the free enzyme. Compared with the free enzyme, the immobilized cellulase has the same optimal pH, higher optimal temperature, better thermal stability and higher catalytic efficiency. The results strongly suggest that the immobilized cellulase on molecular imprinted Fe3O4@SiO2 has the potential applications in the production of bioethanol, paper and pulp industry, and pharmaceutical industry. PMID:24734713

  14. Electronic and magnetic properties of early transition-metal substituted iron-cyclopentadienyl sandwich molecular wires: Parity-dependent half-metallicity

    NASA Astrophysics Data System (ADS)

    Li, Yuanchang; Zhou, Gang; Wu, Jian; Duan, Wenhui

    2011-07-01

    Electronic and magnetic properties of early transition metals (V, Ti, Sc)-FekCpk + 1 sandwich molecular wires (SMWs) are investigated by means of ab initio calculations. It is found that all SMWs favor a ferromagnetic ground state. Significantly, V-FekCpk + 1 SMWs are either half-metallic or semiconducting, dependent upon the parity (even or odd) of the number (k) of Fe atoms in the unit cell of SMWs. This parity oscillation of conductive properties results from the combined effects of the band-folding and gap-opening at the Brillouin-zone boundary of one-dimensional materials. In contrast, Sc-FekCpk + 1 and Ti-FekCpk + 1 SMWs are always semiconducting. Our work may open up the way toward half metal/semiconductor heterostructures with perfect atomic interface.

  15. Magnetic properties of Mn{sub x}Ti{sub 1-x}N thin films grown by plasma-assisted molecular beam epitaxy

    SciTech Connect

    Wu, S. X.; Xia, Y. Q.; Yu, X. L.; Liu, Y. J.; Li, S. W.

    2007-09-15

    High-quality Mn{sub x}Ti{sub 1-x}N thin films were grown on MgO(001) substrates using plasma-assisted molecular beam epitaxy. Magnetic measurements evidence the presence of ferromagnetism with Curie temperature exceeding 380 K. X-ray photoelectron spectroscopy indicates that the Mn ions are in a divalent state and uniformly substitute on Ti cation sites, consistent with the ferromagnetism that correlates with Mn substitution on Ti sites. The origin of the ferromagnetism might be attributed to itinerant-carrier mediated Rudermann-Kittel-Kasuya-Yosida (RKKY)-type long-range coupling which allows for arbitrary itinerant-carrier spin polarization and dynamic correlations.

  16. Investigation of ZnO thin films deposited on ferromagnetic metallic buffer layer by molecular beam epitaxy toward realization of ZnO-based magnetic tunneling junctions

    SciTech Connect

    Belmoubarik, M.; Nozaki, T.; Sahashi, M.; Endo, H.

    2013-05-07

    Deposition of ZnO thin films on a ferromagnetic metallic buffer layer (Co{sub 3}Pt) by molecular beam epitaxy technique was investigated for realization of ZnO-based magnetic tunneling junctions with good quality hexagonal ZnO films as tunnel barriers. For substrate temperature of 600 Degree-Sign C, ZnO films exhibited low oxygen defects and high electrical resistivity of 130 {Omega} cm. This value exceeded that of hexagonal ZnO films grown by sputtering technique, which are used as tunnel barriers in ZnO-MTJs. Also, the effect of oxygen flow during deposition on epitaxial growth conditions and Co{sub 3}Pt surface oxidation was discussed.

  17. Development of magnetic molecularly imprinted polymers for selective extraction: determination of citrinin in rice samples by liquid chromatography with UV diode array detection.

    PubMed

    Urraca, Javier L; Huertas-Pérez, José F; Cazorla, Guillermo Aragoneses; Gracia-Mora, Jesus; García-Campaña, Ana M; Moreno-Bondi, María Cruz

    2016-04-01

    In this work, we report the synthesis of novel magnetic molecularly imprinted polymers (m-MIPs) and their application to the selective extraction of the mycotoxin citrinin (CIT) from food samples. The polymers were prepared by surface imprinting of Fe3O4 nanoparticles, using 2-naphtholic acid (2-NA) as template molecule, N-3,5-bis(trifluoromethyl)phenyl-N'-4-vinylphenyl urea and methacrylamide as functional monomers and ethyleneglycol dimethacrylate as cross-linker. The resulting material was characterized by transmission electron microscopy (TEM), and X-ray diffraction (XRD) and Fourier transform infrared spectroscopies (FT-IR). The polymers were used to develop a solid-phase extraction method (m-MISPE) for the selective recovery of CIT from rice extracts prior to its determination by HPLC with UV diode array detection. The method involves ultrasound-assisted extraction of the mycotoxin from rice samples with (7:3, v/v) methanol/water, followed by sample cleanup and preconcentration with m-MIP. The extraction (washing and elution) conditions were optimized and their optimal values found to provide CIT recoveries of 94-98 % with relative standard deviations (RSD) less than 3.4 % (n = 3) for preconcentrated sample extracts (5 mL) fortified with the analyte at concentrations over the range 25-100 μg kg(-1). Based on the results, the application of the m-MIPs facilitates the accurate and efficient determination of CIT in rice extracts. Graphical Abstract Novel magnetic molecularly imprinted polymers (m-MIPs) for citrinin (CIT) have been obtained and applied to the selective extraction of the mycotoxin from rice samples. PMID:26873195

  18. A cost-effective sandwich electrochemiluminescence immunosensor for ultrasensitive detection of HIV-1 antibody using magnetic molecularly imprinted polymers as capture probes.

    PubMed

    Zhou, Jing; Gan, Ning; Li, Tianhua; Hu, Futao; Li, Xing; Wang, Lihong; Zheng, Lei

    2014-04-15

    In this report, a rapid and cost-effective sandwich electrochemiluminescence (ECL) immunosensor was constructed for the ultrasensitive detection of human immunodeficiency virus type 1 antibody (anti-HIV-1) using magnetic molecularly imprinted polymers (MMIPs) as capture probes by combining surface and epitope imprinting techniques and antigen conjugated with horseradish peroxidase (HRP-HIV-1) as labels. First, 3-aminobenzeneboronic acid (APBA) was used as the functional monomer and cross-linking reagent, which was polymerized on the surface of silicate-coated magnetic iron oxide nanoparticles (Fe3O4@SiO2 NPs) in the presence of human immunoglobulin G (HIgG), as the template exhibiting the same Fc region but different Fab region to anti-HIV-1 after the addition of the initiator, ammonium persulfate. This process resulted in grafting a hydrophilic molecularly imprinted polymer (MIP) film on the Fe3O4@SiO2 NPs. Thus, MMIPs, which could be reused after eluting the template, were used to recognize and enrich ultra-trace levels of anti-HIV-1. Subsequently, a novel sandwich ECL immunosensor was formed through the immunoreaction between MMIPs conjugated with varied concentrations of anti-HIV-1 and HRP-HIV-1. By the catalysis of HRP immobilized onto HRP-HIV-1 on the ECL system of Luminol-H2O2, a linear response range of the anti-HIV-1 dilution ratio (standard positive serum) was achieved from 1:20,000 to 1:50, with a detection limit of 1:60,000 (S/N=3). The developed method provides a low-cost, simple, and sensitive way for the early diagnosis of HIV infected patients. PMID:24280050

  19. Magnetic Hysteresis in Mn_12 -- a Status Report

    NASA Astrophysics Data System (ADS)

    Sarachik, Myriam P.

    2000-03-01

    The molecular magnet Mn_12 acetate consists of a large (Avogadro's) number of identical nanoscopic-sized spin-10 magnetic clusters, each composed of 12 exchange-coupled Mn atoms, regularly arranged on a tetragonal lattice. In the absence of a magnetic field, strong uniaxial anisotropy favors doubly-degenerate spin alignment along the c-axis of the crystal, m_s= ± 10, and two-fold-degenerate excited states corresponding to spin-projections m_s=± 9, ± 8,....0 in a double-well potential. When cooled below its blocking temperature of 3 K, Mn_12 exhibits hysteretic behavior with steep ``steps'' at reproducible, regularly-spaced magnetic fields, indicating enhanced magnetic relaxation at these special field values. This behavior has been attributed to mesoscopic quantum tunneling of the magnetization of the spin-10 magnetic clusters at magnetic fields corresponding to level crossings on opposite sides of the anisotropy barrier. Subsequent EPR and neutron scattering measurements, as well as precise measurements of the magnetic response, have provided detailed information regarding the form of the spin Hamiltonian and the symmetry-breaking terms that drive the tunneling process. Very recent measurements have provided evidence for an abrupt transition to ground-state tunneling (pure quantum tunneling requiring no thermal activation to excited states within the metastable potential well). These experiments will be briefly reviewed and explained, and open questions will be discussed.

  20. Influence of a strong magnetic field on the hydrogen molecular ion using B-spline-type basis-sets

    NASA Astrophysics Data System (ADS)

    Zhang, Yue-Xia; Xiao-Long, Zhang

    2015-12-01

    As an improvement on our previous work [J. Phys. B: At. Mol. Opt. Phys. 45 085101 (2012)], an accurate method combining the spheroidal coordinates and B-spline basis is applied to study the ground state 1σg and low excited states 1σu, 1πg,u,1δg,u,2σg of the in magnetic fields ranging from 109 Gs (1 Gs = 10-4 T) to 4.414 × 1013 Gs. Comparing the one-center method used in our previous work, the present method has a higher precision with a shorter computing time. Equilibrium distances of the states of the in strong magnetic fields were found to be accurate to 3˜5 significant digits (s.d.) and the total energies 6˜11 s.d., even for some antibonding state, such as 1πg, which is difficult for the one-center method to give reliable results while the field strength is B ≥ 1013 Gs. For the large disagreement in previous works, such as the equilibrium distances of the 1πg state at B = 109 Gs, the present data may be used as a reference. Further, the potential energy curves (PECs) and the electronic probability density distributions (EPDDs) of the bound states 1σg, 1πu, 1δg and antibonding states 1σu, 1πg, 1δu for B = 1, 10, 100, 1000 a.u. (atomic unit) are compared, so that the different influences of the magnetic fields on the chemical bonds of the bound states and antibonding states are discussed in detail. Project supported by the National Natural Science Foundation of China (Grant No. 11204389) and the Natural Science Foundation Project of Chongqing (Grant Nos. CSTC2012jjA50015 and CSTC2012jjA00012).

  1. Trinuclear Mo3S7 clusters coordinated to dithiolate or diselenolate ligands and their use in the preparation of magnetic single component molecular conductors.

    PubMed

    Llusar, Rosa; Triguero, Sonia; Polo, Victor; Vicent, Cristian; Gómez-García, Carlos J; Jeannin, Olivier; Fourmigué, Marc

    2008-10-20

    A general route for the preparation of a series of dianionic Mo3S7 cluster complexes bearing dithiolate or diselenolate ligands, namely, [Mo3S7L3](2-) (where L = tfd (bis(trifluoromethyl)-1,2-dithiolate) (4(2-)), bdt (1,2-benzenedithiolate) (5(2-)), dmid (1,3-dithia-2-one-4,5-dithiolate) (6(2-)), and dsit (1,3-dithia-2-thione-4,5-diselenolate) (7(2-))) is reported by direct reaction of [Mo3S7Br6](2-) and (n-Bu)2Sn(dithiolate). The redox properties, molecular structure, and electronic structure (BP86/VTZP) of the 4(2-) to 7(2-) clusters have also been investigated. The HOMO orbital in all complexes is delocalized over the ligand and the Mo3S7 cluster core. Ligand contributions to the HOMO range from 61.67% for 4(2-) to 82.07% for 7(2-), which would allow fine-tuning of the electronic and magnetic properties. These dianionic clusters present small energy gaps between the HOMO and HOMO-1 orbitals (0.277-0.104 eV). Complexes 6(2-) and 7(2-) are oxidized to the neutral state to afford microcrystalline or amorphous fine powders that exhibit semiconducting behavior and present antiferromagnetic exchange interactions. These compounds are new examples of the still rare single-component conductors based on cluster magnetic units. PMID:18808110

  2. Growth and magnetic property of {zeta}-phase Mn{sub 2}N{sub 1{+-}x} thin films by plasma-assisted molecular beam epitaxy

    SciTech Connect

    Liu Yajing; Xu Lingmin; Hu Ping; Li Shuwei; Li Xinyu

    2010-05-15

    {zeta}-phase manganese nitride films were directly grown on sapphire substrates using plasma-assisted molecular beam epitaxy. Mn{sub 2}N{sub 1.06}, Mn{sub 2}N{sub 0.98}, and Mn{sub 2}N{sub 0.86} films were synthesized by controlling the temperature of the effusion cell filled with highly pure manganese powder. The composition, structure, and morphology of the films were identified by x-ray photoelectron spectroscopy, x-ray diffraction and atomic force microscopy, and the magnetic properties of the films were characterized by a superconducting quantum interference device magnetometer at 5 and 300 K. The magnetic measurements reveal that Mn{sub 2}N{sub 1{+-}x} exhibits weak ferromagnetism at 5 K, which is mainly ascribed to the weak interaction among the Mn cations induced by the nitrogen vacancies. Furthermore, the Mn{sub 2}N{sub 0.86} single-crystalline films are found to have room-temperature ferromagnetism, which is attributed to the strain of the Mn{sub 2}N{sub 0.86} films raised from lattice mismatch between the Mn{sub 2}N{sub 0.86} films and the substrates.

  3. Efficient determination of protocatechuic acid in fruit juices by selective and rapid magnetic molecular imprinted solid phase extraction coupled with HPLC.

    PubMed

    Xie, Lianwu; Guo, Junfang; Zhang, Yuping; Shi, Shuyun

    2014-08-13

    Magnetic molecular imprinted polymers (MMIPs) have been prepared as solid phase material to selectively extract protocatechuic acid (PCA) from fruit juices with high capacity and fast binding kinetics. The resulting MMIPs were characterized by TEM, FT-IR, TGA, and VSM. The adsorption process between PCA and MMIPs followed Langumuir adsorption isotherm with maximum adsorption capacity at 7.5 mg/g and pseudo-second-order reaction kinetics with fast binding kinetics (equilibrium time at 40 min). In addition, the prepared MMIPs showed rapid magnetic separation (10 s) and reusability (retained 94.9% after six cycles). Subsequently, MMIPs were successfully applied for selective enrichment and determination of PCA from fruit juices (0.45 μg/mL in grape juice but not detected in apple juice, pineapple juice, orange juice, and peach juice) with satisfactory recoveries (92-107%). The results indicated that synthesized MMIPs can be used for efficient and selective extraction of PCA from complex matrices. PMID:25075753

  4. Rapid degradation of Congo red by molecularly imprinted polypyrrole-coated magnetic TiO2 nanoparticles in dark at ambient conditions.

    PubMed

    Wei, Shoutai; Hu, Xiaolei; Liu, Hualong; Wang, Qiang; He, Chiyang

    2015-08-30

    A novel molecularly imprinted polymer (MIP)-coated magnetic TiO2 nanocomposite was prepared, using methyl orange (MO) as the dummy template and pyrrole as functional monomer, for degradation of Congo red (CR). The nanocomposite was characterized by Fourier transform infrared spectroscopy, thermo-gravimetric analysis, X-ray diffraction, transmission electron microscopy, and vibrating sample magnetometer. The imprinting efficiency of the imprinted nanoparticles was investigated by static binding test, and their degradation ability toward CR was also studied. Moreover, the effects of pH, temperature, dissolved oxygen and oscillation rate on degradation rate of CR were investigated. Results showed that the imprinted nanocomposite had higher adsorption ability for MO compared with the non-imprinted one. Moreover, it could degrade CR rapidly in dark at room temperature and atmospheric pressure and could be recycled easily by a magnet with a good reusability. A degradation mechanism was proposed according to LC-MS analysis of degradation products of CR. The new imprinted nanoparticles showed high catalytic activity at ambient conditions without light illumination and additional chemicals, and therefore, it can be potentially applied to the rapid, "green" and low-cost degradation of CR in industrial printing and dyeing wastewater. PMID:25867589

  5. Structure, electronic and magnetic properties of hexagonal boron nitride sheets doped by 5d transition metal atoms: First-principles calculations and molecular orbital analysis

    NASA Astrophysics Data System (ADS)

    Zhang, Zhaofu; Geng, Zhaohui; Cai, Danyun; Pan, Tongxi; Chen, Yixin; Dong, Liyuan; Zhou, Tiege

    2015-01-01

    A first-principles calculation based on density functional theory is carried out to reveal the geometry, electronic structures and magnetic properties of hexagonal boron nitride sheets (h-BNSs) doped by 5d transitional mental atoms (Lu, Hf, Ta, W, Re, Os, Ir, Pt, Au and Hg) at boron-site (B5d) and nitrogen-site (N5d). Results of pure h-BNS, h-BNS with B vacancy (VB) and N vacancy (VN) are also given for comparison. It is shown that all the h-BNSs doped with 5d atoms possess a C3v local symmetry except for NLu and NHg which have a clear deviation. For the same 5d dopant, the binding energy of B5d is larger than that of N5d, which indicates the substitution of a 5d atom for B is preferred. The total densities of states are presented, where impurity energy levels exist. Besides, the total magnetic moments (TMMs) change regularly with the increment of the 5d atomic number. Theoretical analyses by molecular orbital under C3v symmetry explain the impurity energy levels and TMMs.

  6. Synthesis of magnetic molecularly imprinted polymers by reversible addition fragmentation chain transfer strategy and its application in the Sudan dyes residue analysis.

    PubMed

    Xie, Xiaoyu; Chen, Liang; Pan, Xiaoyan; Wang, Sicen

    2015-07-31

    Magnetic molecularly imprinted polymers (MMIPs) have become a hotspot owing to the dual functions of target recognition and magnetic separation. In this study, the MMIPs were obtained by the surface-initiated reversible addition fragmentation chain transfer (RAFT) polymerization using Sudan I as the template. The resultant MMIPs were characterized by transmission electron microscope, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, vibrating sample magnetometer, and X-ray diffraction. Benefiting from the controlled/living property of the RAFT strategy, the uniform MIP layer was successfully grafted on the surface of RAFT agent-modified Fe3O4@SiO2 nanoparticles, favoring the fast mass transfer and rapid binding kinetics. The developed MMIPs were used as the solid-phase extraction sorbents to selectively extract four Sudan dyes (Sudan I, II, III, and IV) from chili powder samples. The recoveries of the spiked samples in chili powder samples ranged from 74.1 to 93.3% with RSD lower than 6.4% and the relative standard uncertainty lower than 0.029. This work provided a good platform for the extraction and removal of Sudan dyes in complicated matrixes and demonstrated a bright future for the application of the well-constructed MMIPs in the field of solid-phase extraction. PMID:26077971

  7. Temperature and magnetism bi-responsive molecularly imprinted polymers: Preparation, adsorption mechanism and properties as drug delivery system for sustained release of 5-fluorouracil.

    PubMed

    Li, Longfei; Chen, Lin; Zhang, Huan; Yang, Yongzhen; Liu, Xuguang; Chen, Yongkang

    2016-04-01

    Temperature and magnetism bi-responsive molecularly imprinted polymers (TMMIPs) based on Fe3O4-encapsulating carbon nanospheres were prepared by free radical polymerization, and applied to selective adsorption and controlled release of 5-fluorouracil (5-FU) from an aqueous solution. Characterization results show that the as-synthesized TMMIPs have an average diameter of about 150 nm with a typical core-shell structure, and the thickness of the coating layer is approximately 50 nm. TMMIPs also displayed obvious magnetic properties and thermo-sensitivity. The adsorption results show that the prepared TMMIPs exhibit good adsorption capacity (up to 96.53 mg/g at 25 °C) and recognition towards 5-FU. The studies on 5-FU loading and release in vitro suggest that the release rate increases with increasing temperature. Meanwhile, adsorption mechanisms were explored by using a computational analysis to simulate the imprinted site towards 5-FU. The interaction energy between the imprinted site and 5-FU is -112.24 kJ/mol, originating from a hydrogen bond, Van der Waals forces and a hydrophobic interaction between functional groups located on 5-FU and a NIPAM monomer. The electrostatic potential charges and population analysis results suggest that the imprinted site of 5-FU can be introduced on the surface of TMMIPs, confirming their selective adsorption behavior for 5-FU. PMID:26838836

  8. Gd (III) complex conjugate of low-molecular-weight chitosan as a contrast agent for magnetic resonance/fluorescence dual-modal imaging.

    PubMed

    Huang, Yan; Boamah, Peter Osei; Gong, Jianbo; Zhang, Qi; Hua, Mingqing; Ye, Yuzhen

    2016-06-01

    The fusion of molecular and anatomical modalities facilitates more reliable and accurate detection in clinic. In this work, we prepared gadolinium (III) complex Gd-DTPA-FITC-CS11 with magnetic resonance (MR) and fluorescence dual-modal imaging modalities. Gd-DTPA-FITC-CS11 consisted of fluorescein isothiocyanate and low-molecular-weight chitosan (CS11) units conjugated with gadolinium diethylenetriamine pentaacetic acid (Gd-DTPA). Gd-DTPA-FITC-CS11 exhibited a higher longitudinal relaxivity (14.09mM(-1)s(-1)) than the clinical Gd-DTPA (3.85mM(-1)s(-1)). T1-weighted MR contrast enhancement was also demonstrated the comparability to Gd-DTPA at lower dosage. The binding with bovine serum albumin (BSA) was investigated. The fluorescence of BSA in the presence of Gd-DTPA-FITC-CS11 was weakened due to static quenching mechanism. The conformation of BSA was slightly changed but α-helix was dominant. The binding was entropy-driven and spontaneous and the main contribution was hydrophobic interaction. Our results suggested the potential of Gd-DTPA-FITC-CS11 as an MR/fluorescence dual-modal imaging contrast agent in improving the diagnostic sensitivity and accuracy. PMID:27083371

  9. Molecular weight distributions of irradiated siloxane-based elastomers: A complementary study by statistical modeling and multiple quantum nuclear magnetic resonance

    SciTech Connect

    Dinh, L. N.; Mayer, B. P.; Maiti, A.; Chinn, S. C.; Maxwell, R. S.

    2011-05-01

    The statistical methodology of population balance (PB) has been applied in order to predict the effects of cross-linking and chain-scissioning induced by ionizing radiation on the distribution of molecular weight between cross-links (MWBC) of a siloxane-based elastomer. Effective molecular weight distributions were extracted from the quantification of residual dipolar couplings via multiple quantum nuclear magnetic resonance (MQ-NMR) measurements and are taken to reflect actual MWBC distributions. The PB methodology is then applied to the unirradiated MWBC distribution and considers both chain-scissioning and the possibility of the formation of three types of cross-links: random recombination of scissioned-chain ends (end-linking), random covalent bonds of free radicals on scissioned-chain ends (Y-cross-linking), and the formation of random cross-links from free radicals on side groups (H-cross-linking). The qualitative agreement between the statistical modeling approach and the NMR data confirms that it is possible to predict trends for the evolution of the distribution of MWBC of polymers under irradiation. The approach described herein can also discern heterogeneities in radiation effects in different structural motifs in the polymer network.

  10. Supramolecular Assembly of Molecular Rare-Earth-3,5-Dichlorobenzoic Acid-2,2':6',2″-Terpyridine Materials: Structural Systematics, Luminescence Properties, and Magnetic Behavior.

    PubMed

    Carter, Korey P; Thomas, Kara E; Pope, Simon J A; Holmberg, Rebecca J; Butcher, Ray J; Murugesu, Muralee; Cahill, Christopher L

    2016-07-18

    The syntheses and crystal structures of 16 new rare-earth (RE = La(3+)-Y(3+))-3,5-dichlorobenzoic acid-terpyridine molecular materials characterized via single-crystal and powder X-ray diffraction are reported. These 16 complexes consist of four unique structure types ranging from molecular dimers (La(3+) and Ce(3+)) to tetramers (Pr(3+)-Y(3+)) as one moves across the RE(3+) series. This structural evolution is accompanied by subsequent changes in modes of supramolecular assembly (halogen bonding, halogen-π, halogen-halogen, and π-π interactions). Solid-state visible and near-infrared lifetime measurements were performed on complexes 6 (Sm(3+)), 7 (Eu(3+)), 9 (Tb(3+)), 10 (Dy(3+)), 11 (Ho(3+)), 12 (Er(3+)), and 14 (Yb(3+)), and characteristic emission was observed for all complexes except 11. Lifetime data for 11, 12, and 14 suggest sensitization by the terpy antenna does occur in near-infrared systems, although not as efficiently as in the visible region. Additionally, direct current magnetic susceptibility measurements were taken for complexes 10 (Dy(3+)) and 12 (Er(3+)) and showed dominant ferromagnetic behavior. PMID:27347607

  11. A sensitive and selective chemiluminescence sensor for the determination of dopamine based on silanized magnetic graphene oxide-molecularly imprinted polymer

    NASA Astrophysics Data System (ADS)

    Duan, Huimin; Li, Leilei; Wang, Xiaojiao; Wang, Yanhui; Li, Jianbo; Luo, Chuannan

    2015-03-01

    Based on silanized magnetic graphene oxide-molecularly imprinted polymer (Si-MG-MIP), a sensitive and selective chemiluminescence sensor for dopamine measurement was developed. Si-MG-MIP, in which silanes was introduced to improve the mass transfer, graphene oxide was employed to improve absorption capacity, Fe3O4 nanoparticles were applied for separation easily and molecularly imprinted polymer was used to improve selectivity, demonstrated the advantages of the sensor. All the composites were confirmed by SEM, TEM, XRD and FTIR. Under the optimal conditions of chemiluminescence, dopamine could be assayed in the range of 8.0-200.0 ng/mL with a correlation coefficient of linear regression of 0.9970. The detection limit was 1.5 ng/mL (3δ) and the precision for 11 replicate detections of 80.0 ng/mL dopamine was 3.4% (RSD). When the sensor was applied in determining dopamine in actual samples, recovery ranged from 94% to 110%, which revealed that the results were satisfactory.

  12. Modulation of a Molecular π-Electron System in a Purely Organic Conductor that Shows Hydrogen-Bond-Dynamics-Based Switching of Conductivity and Magnetism.

    PubMed

    Ueda, Akira; Hatakeyama, Akari; Enomoto, Masaya; Kumai, Reiji; Murakami, Youichi; Mori, Hatsumi

    2015-10-12

    New important aspects of the hydrogen-bond (H-bond)-dynamics-based switching of electrical conductivity and magnetism in an H-bonded, purely organic conductor crystal have been discovered by modulating its tetrathiafulvalene (TTF)-based molecular π-electron system by means of partial sulfur/selenium substitution. The prepared selenium analogue also showed a similar type of phase transition, induced by H-bonded deuterium transfer followed by electron transfer between the H-bonded TTF skeletons, and the resulting switching of the physical properties; however, subtle but critical differences due to sulfur/selenium substitution were detected in the electronic structure, phase transition nature, and switching function. A molecular-level discussion based on the crystal structures shows that this chemical modification of the TTF skeleton influences not only its own π-electronic structure and π-π interactions within the conducting layer, but also the H-bond dynamics between the TTF π skeletons in the neighboring layers, which enables modulation of the interplay between the H-bond and π electrons to cause such differences. PMID:26311352

  13. A sensitive and selective chemiluminescence sensor for the determination of dopamine based on silanized magnetic graphene oxide-molecularly imprinted polymer.

    PubMed

    Duan, Huimin; Li, Leilei; Wang, Xiaojiao; Wang, Yanhui; Li, Jianbo; Luo, Chuannan

    2015-03-15

    Based on silanized magnetic graphene oxide-molecularly imprinted polymer (Si-MG-MIP), a sensitive and selective chemiluminescence sensor for dopamine measurement was developed. Si-MG-MIP, in which silanes was introduced to improve the mass transfer, graphene oxide was employed to improve absorption capacity, Fe3O4 nanoparticles were applied for separation easily and molecularly imprinted polymer was used to improve selectivity, demonstrated the advantages of the sensor. All the composites were confirmed by SEM, TEM, XRD and FTIR. Under the optimal conditions of chemiluminescence, dopamine could be assayed in the range of 8.0-200.0 ng/mL with a correlation coefficient of linear regression of 0.9970. The detection limit was 1.5 ng/mL (3δ) and the precision for 11 replicate detections of 80.0 ng/mL dopamine was 3.4% (RSD). When the sensor was applied in determining dopamine in actual samples, recovery ranged from 94% to 110%, which revealed that the results were satisfactory. PMID:25574658

  14. Theory, fabrication and applications of metamaterials composed of cylinders

    NASA Astrophysics Data System (ADS)

    Strickland, Diana

    In this work we design a new type of hyperlens composed of nanowires, and numerically demonstrate its ability to resolve closely spaced and otherwise indistinguishable features of an imaged object in the far field. Conversely, we demonstrate the ability of a concentrator to focus incident radiation into an area much smaller than a wave length. To overcome limitations in fabricating materials such as the nanowire composites used in the applications above as well as other materials composed of cylindrical structures, we propose the newly patented method, #US2015/0017466A1, that features initial masked patterning and partial self-assembly, resulting in a relatively simple, inexpensive process with a flexible flow and many constituent material options, capable of forming composites with diverse functionalities. Although modeling the effective properties of cylinder-based media has been the focus of considerable research in the field of Metamaterials, surprisingly enough, no complete and fully dynamic model of such cylinders' response to incident radiation existed. Based on Mie scattering theory, we derive the complete dynamic polarizability tensor for circular, azimuthally symmetric cylinders excited by an arbitrary field distribution, and provide compact expressions for all of its elements. Interestingly, magnetoelectric effects are shown to arise at oblique incidence, even in the case of centrosymmetric achiral thin cylinders, associated with a weak form of spatial dispersion. We expect the polarizabilities to find applications in antenna design, in metamaterial design, and to improve the physical understanding of the wave interaction and spatial dispersion in artificial materials composed of elongated inclusions such as wire media.

  15. Near-edge x-ray absorption studies of Na-doped tetracyanoethylene films: A model system for the V(TCNE)x room-temperature molecular magnet

    NASA Astrophysics Data System (ADS)

    Carlegrim, E.; Gao, B.; Kanciurzewska, A.; de Jong, M. P.; Wu, Z.; Luo, Y.; Fahlman, M.

    2008-02-01

    V(TCNE)x , with TCNE=tetracyanoethylene and xtilde 2 , is an organic-based molecular magnet with potential to be used in spintronic devices. With the aim of shedding light on the unoccupied frontier electronic structure of V(TCNE)x we have studied pristine TCNE and sodium-intercalated TCNE by near edge x-ray absorption fine structure (NEXAFS) spectroscopy as well as with theoretical calculations. Sodium-intercalated TCNE was used as a model system of the more complex V(TCNE)x and both experimental and theoretical results of the model compound have been used to interpret the NEXAFS spectra of V(TCNE)x . By comparing the experimental and theoretical C K -edge of pristine TCNE, the contributions from the various carbon species (cyano and vinyl) could be disentangled. Upon fully sodium intercalation, TCNE is n doped with one electron per molecule and the features in the C and N K -edge spectra of pristine TCNE undergo strong modification caused by partially filling the TCNE lowest unoccupied molecular orbital (LUMO). When comparing the C and N K -edge NEXAFS spectra of fully sodium-doped TCNE with V(TCNE)x , the spectra are similar except for broadening of the features which originates from structural disorder of the V(TCNE)x films. The combined results from the model system and V(TCNE)x suggest that the lowest unoccupied molecular orbital with density on the nitrogen atoms in V(TCNE)x has no significant hybridization with vanadium and is similar to the so-called singly occupied molecular orbital of the TCNE anion. This suggests that the LUMO of V(TCNE)x is TCNE- or vanadiumlike, in contrast to the frontier occupied electronic structure where the highest occupied molecular orbital is a hybridization between V(3d) and cyano carbons. The completely different nature of the unoccupied and occupied frontier electronic structure of the material will most likely affect both charge injection and transport properties of a spintronic device featuring V(TCNE)x .

  16. System Composer: Technology for rapid system integration and remote collaboration

    SciTech Connect

    Davies, B.R.; Palmquist, R.D.

    1996-03-01

    Sandia National Laboratories has developed an approach to the design, evaluation, deployment and operation of intelligent systems which is called System Composer. This toolkit provides an infrastructure and architecture for robot and automation system users to readily integrate system components and share mechatronic, sensor, and information resources over networks. The technology described in this paper provides a framework for real-time collaboration between researchers, manufacturing entities, design entities, and others without regard to relative location. An overview of the toolkit including its elements and architecture is provided along with examples of its use.

  17. Liquid Crystalline Networks Composed of Pentagonal, Square, and Triangular Cylinders

    NASA Astrophysics Data System (ADS)

    Chen, Bin; Zeng, Xiangbing; Baumeister, Ute; Ungar, Goran; Tschierske, Carsten

    2005-01-01

    T-shaped molecules are designed in such a way that they self-organize into nanoscale liquid crystalline honeycombs based on polygons with any chosen number of sides. One of the phases reported here is a periodic organization of identical pentagonal cylinders; the other one is a structure composed of square-shaped and triangular cylinders in the ratio 2:1. These two different packing motifs represent duals of the same topological class. The generalization of the concept applied here allows the prediction of a whole range of unusual complex liquid crystalline phases.

  18. Dipole-exchange spin waves in nanotubes composed of uniaxial ferromagnets with "easy-plane" and "easy-axis" anisotropies

    NASA Astrophysics Data System (ADS)

    Gorobets, Yu. I.; Kulish, V. V.

    2015-07-01

    Dipole-exchange spin waves in nanotubes composed of uniaxial ferromagnets are studied. An equation for the magnetic potential of linear spin waves in uniaxial "easy plane" ferromagnets is obtained in the magnetostatic approximation taking into account magnetic dipole-dipole interactions, exchange interactions, and anisotropy effects. A solution is found for this equation and a dispersion relation for these types of spin waves is obtained. The dependence of the spin wave frequency on the total wave number is found for the case of a thin nanotube. An expression is derived for the transverse wave number spectrum.

  19. Hybrid plasmonic magnetic nanoparticles as molecular specific agents for MRI/optical imaging and photothermal therapy of cancer cells

    NASA Astrophysics Data System (ADS)

    Larson, Timothy A.; Bankson, James; Aaron, Jesse; Sokolov, Konstantin

    2007-08-01

    Nanoparticles which consist of a plasmonic layer and an iron oxide moiety could provide a promising platform for development of multimodal imaging and therapy approaches in future medicine. However, the feasibility of this platform has yet to be fully explored. In this study we demonstrated the use of gold-coated iron oxide hybrid nanoparticles for combined molecular specific MRI/optical imaging and photothermal therapy of cancer cells. The gold layer exhibits a surface plasmon resonance that provides optical contrast due to light scattering in the visible region and also presents a convenient surface for conjugating targeting moieties, while the iron oxide cores give strong T2 (spin-spin relaxation time) contrast. The strong optical absorption of the plasmonic gold layer also makes these nanoparticles a promising agent for photothermal therapy. We synthesized hybrid nanoparticles which specifically target epidermal growth factor receptor (EGFR), a common biomarker for many epithelial cancers. We demonstrated molecular specific MRI and optical imaging in MDA-MB-468 breast cancer cells. Furthermore, we showed that receptor-mediated aggregation of anti-EGFR hybrid nanoparticles allows selective destruction of highly proliferative cancer cells using a nanosecond pulsed laser at 700 nm wavelength, a significant shift from the peak absorbance of isolated hybrid nanoparticles at 532 nm.

  20. Preparation and characterization of the pH and thermosensitive magnetic molecular imprinted nanoparticle polymer for the cancer drug delivery.

    PubMed

    Kaamyabi, Sharif; Habibi, Davood; Amini, Mostafa M

    2016-05-01

    A novel pH and thermosensitive magnetic nanoparticle polymer composite [poly(NIPAAM@Fe3O4 MNPs/TMSPMC/DOX)] was synthesized by radical polymerization of N-isopropylacrylamide (NIPAAM) and the methacrylate functionalized Fe3O4 nanoparticles/DOX complex using AIBN and EGDMA, and used as a drug carrier for the DOX drug delivery. Formation of poly(NIPAAM@Fe3O4 MNPs/TMSPMC/DOX) was confirmed by FTIR, XRD, UV-Vis, VSM, TGA-DTA and SEM. The results showed the high DOX loading controls release. Moreover, it showed the lower critical solution temperature of 40°C which can be beneficial in cancer drug delivery, since the temperature of cancer cells is higher than normal ones, and DOX can be released selectively in cancer cells. PMID:27020717