Iron(III) Porphyrin Covalently Supported onto Magnetic Amino-Functionalized Nanospheres as Catalyst for Hydrocarbon and Herbicide Oxidations

This work describes the covalent immobilization of an ironporphyrin, 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin iron(III) chloride (FeTFPP), onto maghemite/silica magnetic nanospheres covered with aminofunctionalized silica. The resulting material (gamma-Fe2O3/SiO2-NHFeP) was characterized by diffuse reflectance infrared spectroscopy (DRIFTS) and UV-Vis absorption spectroscopy. The catalytic activity of this magnetic ironporphyrin was investigated in the oxidation of hydrocarbons (styrene, (Z)-cyclooctene and R-(+)-limonene) and an herbicide (simazine) by hydrogen peroxide or 3-chloroperoxybenzoic acid. Hydrocarbon and simazine oxidation reaction products were analyzed by gas chromatography (GC) and high performance liquid chromatography (HPLC), respectively. This catalytic system proved to be efficient and selective for hydrocarbon oxidation, leading to high product yields from styrene (89%), cyclooctene (71%) and R-(+) -limonene (86%). Simazine oxidation was attained with 100% selectivity for a dechlorinated product (OEAT), while several oxidation products were obtained for the same catalyst in homogeneous media. The catalyst can be easily recovered through application of an external magnetic field and washed after reaction. Catalyst reuse experiments for R-(+)-limonene oxidation have shown that the catalytic activity is kept at 90% after 10 consecutive reactions.

Optical third harmonic generation in the magnetic semiconductor EuSe

Third harmonic generation (THG) has been studied in europium selenide EuSe in the vicinity of the band gap at 2.1-2.6 eV and at higher energies up to 3.7 eV. EuSe is amagnetic semiconductor crystalizing in centrosymmetric structure of rock-salt type with the point group m3m. For this symmetry the crystallographic and magnetic-field-induced THG nonlinearities are allowed in the electric-dipole approximation. Using temperature, magnetic field, and rotational anisotropy measurements, the crystallographic and magnetic-field-induced contributions to THG were unambiguously separated. Strong resonant magnetic-field-induced THG signals were measured at energies in the range of 2.1-2.6 eV and 3.1-3.6 eV for which we assign to transitions from 4 f(7) to 4 f(6)5d(1) bands, namely involving 5d(t(2g)) and 5d(e(g)) states.

Biocompatible Magnetic Microspheres for Use in PDT and Hyperthermia

Loaded microspheres with a silicon (IV) phthalocyanine derivative (NzPC) acting as a photosensitizer were prepared from polyhydroxybutyrate-co-valerate (PHBHV) and poly(ecaprolactone) (PCL) polymers using the emulsification solvent evaporation method (EE). The aim of our study was to prepare two systems of these biodegradable PHBHV/PCL microspheres. The first one containing only photosensitizer previously incorporated in the PHBHV and poly(ecaprolactone) (PCL) microspheres and the second one with the post magnetization of the DDS with magnetic nanoparticles. Magnetic fluid is successfully used for controlled incorporation of nanosized magnetic particles within the micron-sized template. This is the first time that we could get a successful pos incorporation of nanosized magnetic particles in a previously-prepared polymeric template. This procedure opens a great number of possibilities of post-functionalization of polymeric micro or nanoparticles with different bioactive materials. The NzPC release profile of the systems is ideal for PDT, the zeta potential and the size particle are stable upon aging in time. In vitro studies were evaluated using gingival fibroblastic cell line. The dark citotoxicity, the phototoxicity and the AC magnetic field assays of the as-prepared nanomagnetic composite were evaluated and the cellular viability analyzed by the classical test of MU.

Schrodinger and Dirac operators with the Aharonov-Bohm and magnetic-solenoid fields

We construct all self-adjoint Schrodinger and Dirac operators (Hamiltonians) with both the pure Aharonov-Bohm (AB) field and the so-called magnetic-solenoid field (a collinear superposition of the AB field and a constant magnetic field). We perform a spectral analysis for these operators, which includes finding spectra and spectral decompositions, or inversion formulae. In constructing the Hamiltonians and performing their spectral analysis, we follow, respectively, the von Neumann theory of self-adjoint extensions of symmetric operators and the Krein method of guiding functionals.

Complex mixed state of the Pauli-limited superconductor CeCoIn5

Magnetization measurements were performed on CeCoIn5 at temperatures down to 20 mK and magnetic fields up to 17 T applied along different crystallographic orientations. For field configurations nearly parallel to the ab plane (theta less than or similar to 40 degrees and T <= 50 mK), we have found an intriguing vortex dynamics regime revealed by a hysteretic and metastable anomalous peak effect (APE), which gives evidence of surface barrier effects enhanced by antiferromagnetic fluctuations in the mixed state of CeCoIn5. Furthermore, we have observed crossover features in the torque and magnetization traces at fields below H-c2, which are consistent with vortices lattice phase transitions and with the anomalies speculated to be the Fulde-Ferrel-Larkin-Ovchinnikov (FFLO) superconducting state in CeCoIn5. All of the above features were found to be dramatically perturbed in Ce0.98Gd0.02CoIn5.

Flux-Line-Lattice Melting and Upper Critical Field of Bi1.65Pb0.35Sr2Ca2Cu3O10+delta Ceramic Samples

We have conducted magnetoresistance measurements rho(T,H) in applied magnetic fields up to 18 T in Bi1.65Pb0.35Sr2Ca2Cu3O10+delta ceramic samples which were subjected to different uniaxial compacting pressures. The anisotropic upper critical fields H (c2)(T) were extracted from the rho(T,H) data, yielding and the out-of-plane superconducting coherence length xi (c) (0)similar to 3 . We have also estimated and xi (ab) (0) similar to 90 . In addition to this, a flux-line-lattice (FLL) melting temperature T (m) has been identified as a second peak in the derivative of the magnetoresistance d rho/dT data close to the superconducting transition temperature. An H (m) vs. T phase diagram was constructed and the FLL boundary lines were found to obey a temperature dependence H (m) ae(T (c) /T-1) (alpha) , where alpha similar to 2 for the sample subjected to the higher compacting pressure. A reasonable value of the Lindemann parameter c (L) similar to 0.29 has been found for all samples studied.

Co-nanoencapsulation of magnetic nanoparticles and selol for breast tumor treatment: in vitro evaluation of cytotoxicity and magnetohyperthermia efficacy

Antitumor activities have been described in selol, a hydrophobic mixture of molecules containing selenium in their structure, and also in maghemite magnetic nanoparticles (MNPs). Both selol and MNPs were co-encapsulated within poly(lactic-co-glycolic acid) (PLGA) nanocapsules for therapeutic purposes. The PLGA-nanocapsules loaded with MNPs and selol were labeled MSE-NC and characterized by transmission and scanning electron microscopy, electrophoretic mobility, photon correlation spectroscopy, presenting a monodisperse profile, and positive charge. The antitumor effect of MSE-NC was evaluated using normal (MCF-10A) and neoplastic (4T1 and MCF-7) breast cell lines. Nanocapsules containing only MNPs or selol were used as control. MTT assay showed that the cytotoxicity induced by MSE-NC was dose and time dependent. Normal cells were less affected than tumor cells. Cell death occurred mainly by apoptosis. Further exposure of MSE-NC treated neoplastic breast cells to an alternating magnetic field increased the antitumor effect of MSE-NC. It was concluded that selol-loaded magnetic PLGA-nanocapsules (MSE-NC) represent an effective magnetic material platform to promote magnetohyperthermia and thus a potential system for antitumor therapy.

Magnetic hyperthermia investigation of cobalt ferrite nanoparticles: Comparison between experiment, linear response theory, and dynamic hysteresis simulations

Considerable effort has been made in recent years to optimize materials properties for magnetic hyperthermia applications. However, due to the complexity of the problem, several aspects pertaining to the combined influence of the different parameters involved still remain unclear. In this paper, we discuss in detail the role of the magnetic anisotropy on the specific absorption rate of cobalt-ferrite nanoparticles with diameters ranging from 3 to 14 nm. The structural characterization was carried out using x-ray diffraction and Rietveld analysis and all relevant magnetic parameters were extracted from vibrating sample magnetometry. Hyperthermia investigations were performed at 500 kHz with a sinusoidal magnetic field amplitude of up to 68 Oe. The specific absorption rate was investigated as a function of the coercive field, saturation magnetization, particle size, and magnetic anisotropy. The experimental results were also compared with theoretical predictions from the linear response theory and dynamic hysteresis simulations, where exceptional agreement was found in both cases. Our results show that the specific absorption rate has a narrow and pronounced maxima for intermediate anisotropy values. This not only highlights the importance of this parameter but also shows that in order to obtain optimum efficiency in hyperthermia applications, it is necessary to carefully tailor the materials properties during the synthesis process. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4729271]

Bose glass and Mott glass of quasiparticles in a doped quantum magnet

The low-temperature states of bosonic fluids exhibit fundamental quantum effects at the macroscopic scale: the best-known examples are Bose-Einstein condensation and superfluidity, which have been tested experimentally in a variety of different systems. When bosons interact, disorder can destroy condensation, leading to a 'Bose glass'. This phase has been very elusive in experiments owing to the absence of any broken symmetry and to the simultaneous absence of a finite energy gap in the spectrum. Here we report the observation of a Bose glass of field-induced magnetic quasiparticles in a doped quantum magnet (bromine-doped dichloro-tetrakis-thiourea-nickel, DTN). The physics of DTN in a magnetic field is equivalent to that of a lattice gas of bosons in the grand canonical ensemble; bromine doping introduces disorder into the hopping and interaction strength of the bosons, leading to their localization into a Bose glass down to zero field, where it becomes an incompressible Mott glass. The transition from the Bose glass (corresponding to a gapless spin liquid) to the Bose-Einstein condensate (corresponding to a magnetically ordered phase) is marked by a universal exponent that governs the scaling of the critical temperature with the applied field, in excellent agreement with theoretical predictions. Our study represents a quantitative experimental account of the universal features of disordered bosons in the grand canonical ensemble.

STRUCTURE OF THE ELECTROMAGNETIC FIELD ALLOWING EXACT SOLUTION OF THE SCHRODINGER EQUATION IN SUPERPOSITION WITH AN AHARONOV-BOHM FIELD

A charged particle is considered in a complex external electromagnetic field. The field is a superposition of an Aharonov-Bohm field and some additional field. Here we describe all additional fields known up to the present time that allow exact solution of the Schrodinger equation in a complex field.

THE ROLE OF TURBULENT MAGNETIC RECONNECTION IN THE FORMATION OF ROTATIONALLY SUPPORTED PROTOSTELLAR DISKS

The formation of protostellar disks out of molecular cloud cores is still not fully understood. Under ideal MHD conditions, the removal of angular momentum from the disk progenitor by the typically embedded magnetic field may prevent the formation of a rotationally supported disk during the main protostellar accretion phase of low-mass stars. This has been known as the magnetic braking problem and the most investigated mechanism to alleviate this problem and help remove the excess of magnetic flux during the star formation process, the so-called ambipolar diffusion (AD), has been shown to be not sufficient to weaken the magnetic braking at least at this stage of the disk formation. In this work, motivated by recent progress in the understanding of magnetic reconnection in turbulent environments, we appeal to the diffusion of magnetic field mediated by magnetic reconnection as an alternative mechanism for removing magnetic flux. We investigate numerically this mechanism during the later phases of the protostellar disk formation and show its high efficiency. By means of fully three-dimensional MHD simulations, we show that the diffusivity arising from turbulent magnetic reconnection is able to transport magnetic flux to the outskirts of the disk progenitor at timescales compatible with the collapse, allowing the formation of a rotationally supported disk around the protostar of dimensions similar to 100 AU, with a nearly Keplerian profile in the early accretion phase. Since MHD turbulence is expected to be present in protostellar disks, this is a natural mechanism for removing magnetic flux excess and allowing the formation of these disks. This mechanism dismisses the necessity of postulating a hypothetical increase of the ohmic resistivity as discussed in the literature. Together with our earlier work which showed that magnetic flux removal from molecular cloud cores is very efficient, this work calls for reconsidering the relative role of AD in the processes of star and planet formation.

Iron(III) porphyrin covalently supported onto magnetic amino-functionalized nanospheres as catalyst for hydrocarbon and herbicide oxidations

This work describes the covalent immobilization of an ironporphyrin, 5,10,15,20- tetrakis(pentafluorophenyl)porphyrin iron(III) chloride (FeTFPP), onto maghemite/silica magnetic nanospheres covered with aminofunctionalized silica. The resulting material (γ-Fe2O3/SiO2-NHFeP) was characterized by diffuse reflectance infrared spectroscopy (DRIFTS) and UV-Vis absorption spectroscopy. The catalytic activity of this magnetic ironporphyrin was investigated in the oxidation of hydrocarbons (styrene, (Z)-cyclooctene and R-(+)-limonene) and an herbicide (simazine) by hydrogen peroxide or 3-chloroperoxybenzoic acid. Hydrocarbon and simazine oxidation reaction products were analyzed by gas chromatography (GC) and high performance liquid chromatography (HPLC), respectively. This catalytic system proved to be efficient and selective for hydrocarbon oxidation, leading to high product yields from styrene (89%), cyclooctene (71%) and R-(+)-limonene (86%). Simazine oxidation was attained with 100% selectivity for a dechlorinated product (OEAT), while several oxidation products were obtained for the same catalyst in homogeneous media. The catalyst can be easily recovered through application of an external magnetic field and washed after reaction. Catalyst reuse experiments for R-(+)-limonene oxidation have shown that the catalytic activity is kept at 90% after 10 consecutive reactions.

Magnetic color-flavor-locked stars

Using the solutions of the gap equations of the magnetic-color-flavor-locked (MCFL) phase of paired quark matter in a magnetic field, and taking into consideration the separation between the longitudinal and transverse pressures due to the field-induced breaking of the spatial rotational symmetry, the equation of state (EoS) of the MCFL phase is self-consistently determined. Implications for stellar models of magnetized (self-bound) strange stars and hybrid (MCFL core) stars are discussed.

Magnetic topology and current channels in plasmas with toroidal current density inversions

The equilibrium magnetic field inside axisymmetric plasmas with inversions on the toroidal current density is studied. Structurally stable non-nested magnetic surfaces are considered. For any inversion in the internal current density the magnetic families define several positive current channels about a central negative one. A general expression relating the positive and negative currents is derived in terms of a topological anisotropy parameter. Next, an analytical local solution for the poloidal magnetic flux is derived and shown compatible with current hollow magnetic pitch measurements shown in the literature. Finally, the analytical solution exhibits non-nested magnetic families with positive anisotropy, indicating that the current inside the positive channels have at least twice the magnitude of the central one.

A spectroscopic and photometric study of MSP companions in Galactic Globular Clusters

This Thesis is devoted to the study of the optical companions of Millisecond Pulsars in Galactic Globular Clusters (GCs) as a part of a large project started at the Department of Astronomy of the Bologna University, in collaboration with other institutions (Astronomical Observatory of Cagliari and Bologna, University of Virginia), specifically dedicated to the study of the environmental effects on passive stellar evolution in galactic GCs. Globular Clusters are very efficient “Kilns” for generating exotic object, such as Millisecond Pulsars (MSP), low mass X-ray binaries(LMXB) or Blue Straggler Stars (BSS). In particular MSPs are formed in binary systems containing a Neutron Star which is spun up through mass accretion from the evolving companion (e.g. Bhattacharia & van den Heuvel 1991). The final stage of this recycling process is either the core of a peeled star (generally an Helium white dwarf) or a very light almos exhausted star, orbiting a very fast rotating Neutron Star (a MSP). Despite the large difference in total mass between the disk of the Galaxy and the Galactic GC system (up a factor 103), the percentage of fast rotating pulsar in binary systems found in the latter is very higher. MSPs in GCs show spin periods in the range 1.3 ÷ 30ms, slowdown rates ˙P 1019 s/s and a lower magnetic field, respect to ”normal” radio pulsars, B 108 gauss . The high probability of disruption of a binary systems after a supernova explosion, explain why we expect only a low percentage of recycled millisecond pulsars respect to the whole pulsar population. In fact only the 10% of the known 1800 radio pulsars are radio MSPs. Is not surprising, that MSP are overabundant in GCs respect to Galactic field, since in the Galactic Disk, MSPs can only form through the evolution of primordial binaries, and only if the binary survives to the supernova explosion which lead to the neutron star formation. On the other hand, the extremely high stellar density in the core of GCs, relative to most of the rest of the Galaxy, favors the formation of several different binary systems, suitable for the recycling of NSs (Davies at al. 1998). In this thesis we will present the properties two millisecond pulsars companions discovered in two globular clusters, the Helium white dwarf orbiting the MSP PSR 1911-5958A in NGC 6752 and the second case of a tidally deformed star orbiting an eclipsing millisecond pulsar, PSR J1701-3006B in NGC6266