7,186 research outputs found
Synthesis of Al and Ag nanoparticles through ultra-sonic dissociation of thermal evaporation deposited thin films for promising clinical applications as polymer nanocomposite
Nanoparticles (NPs) having well-defined shape, size and clean surface serve as ideal model system to investigate surface/interfacial reactions. Ag and Al NPs are receiving great interest due to their wide applications in bio-medical field, aerospace and space technology as combustible additives in propellants and hydrogen generation. Hence, in this study, we have synthesized Ag and Al NPs using an innovative approach of ultra-sonic dissociation of thin films. Phase and particle size distributions of the Ag and Al NPs have been determined by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Thin film dissociation/dissolution mechanism, hence conversion into NPs has been characterized by SEM- scanning electron microscope. EDXA & ICPMS have been performed for chemical analysis of NPs. Optical properties have been characterized by UV-Vis and PL spectroscopy. These NPs have also been investigated for their anti-bacterial activity against Escherichia coli bacteria. To the best of our knowledge, this is the first time when NPs has been synthesized by ultra-sonic dissociation of thin films. As an application, these NPs were used further for synthesis of nanocomposite polymer membranes, which show excellent activity against bio film formation
Intrinsic Structural Disorder and the Magnetic Ground State in Bulk EuTiO3
The magnetic properties of single-crystal EuTiO3 are suggestive of nanoscale
disorder below its cubic-tetragonal phase transition. We demonstrate that
electric field cooling acts to restore monocrystallinity, thus confirming that
emergent structural disorder is an intrinsic low-temperature property of this
material. Using torque magnetometry, we deduce that tetragonal EuTiO3 enters an
easy-axis antiferromagnetic phase at 5.6 K, with a first-order transition to an
easy-plane ground state below 3 K. Our data is reproduced by a 3D anisotropic
Heisenberg spin model.Comment: 5 pages, 4 figure
Microcircuit modeling and simulation beyond Ohm's law
Circuit theory textbooks rely heavily on the applicability of Ohms law, which collapses as electronic components reach micro-and nanoscale dimensions. Circuit analysis is examined in the regime where the applied voltage V is greater than the critical voltage $Vc, which triggers the nonlinear behavior. The critical voltage is infinity in the Ohmic regime, but is as low as a fraction of a volt when linear currentvoltage characteristics become sublinear and the resistance surges due to current saturation effects. For two resistors of the same Ohmic values but of differing lengths, the shorter resistor is more susceptible to this effect. In addition, the power consumed in this regime is a linear function of voltage as compared to quadratic behavior in the Ohmic regime. Several possible applications are suggested
Mirnov coil data analysis for tokamak ADITYA
The spatial and temporal structures of magnetic signal in the tokamak ADITYA is analysed using recently developed singular value decomposition (SVD) technique. The analysis technique is first tested with simulated data and then applied to the ADITYA Mirnov coil data to determine the structure of current peturbation as the discharge progresses. It is observed that during the current rise phase, current perturbation undergoes transition from m=5 poloidal structure to m=4 and then to m=3. At the time of current termination, m=2 perturbation is observed. It is observed that the mode frequency remains nearly constant (≈10 kHz) when poloidal mode structure changes from m=4 to m=2. This may be either an indication of mode coupling or a consequences of changes in the plasma electron temperature and density scale length
Automated Rendezvous and Docking Using Tethered Formation Flight
This paper analyzes capture strategies for tether-based autonomous rendezvous and docking. Once both spacecrafts are connected by tethers, docking is achieved through the use of reaction wheels and tether motors without the use of propellant. Autonomous rendezvous and docking is crucial for many upcoming missions including on-orbit servicing and potential Mars missions. The tether-based capture strategies investigated are a spin-up tether deployment and a free-flying child spacecraft attaching the tether. These strategies are compared to a traditional two-agent propulsive docking strategy. The capture strategies are simulated from initial orbit through to completed dock, with the total fuel consumption and dock time compared, along with initial pointing/location requirements. In addition to having lower fuel cost, the tether-based strategies are also more reliable due to redundancy, since tethers can be reeled back in and multiple tethers can be stored for use in case of primary tether failure
Evidence for Uniform Coexistence of Ferromagnetism and Unconventional Superconductivity in UGe_2: A ^73Ge-NQR Study under Pressure
We report on the itinerant ferromagnetic superconductor UGe_2 through
^73Ge-NQR measurements under pressure (P). The P dependence of the NQR spectrum
signals a first-order transition from the low-temperature (T) and low-P
ferromagnetic phase (FM2) to high-T and high-P one (FM1) around a critical
pressure of P_x ~ 1.2 GPa. The superconductivity exhibiting a maximum value of
T_sc=0.7 K at P_x ~ 1.2 GPa, was found to take place in connection with the
P-induced first-order transition. The nuclear spin-lattice relaxation rate
1/T_1 has probed the ferromagnetic transition, exhibiting a peak at the Curie
temperature as well as a decrease without the coherence peak below T_sc. These
results reveal the uniformly coexistent phase of ferromagnetism and
unconventional superconductivity with a line-node gap. We remark on an intimate
interplay between the onset of superconductivity and the underlying electronic
state for the ferromagnetic phases.Comment: 8 pages, 9 figures. to appear in J. Phys. Soc. JPN, 74 No.2 (2005
Generalized Mittag-Leffler Distributions and Processes for Applications in Astrophysics and Time Series Modeling
Geometric generalized Mittag-Leffler distributions having the Laplace
transform is
introduced and its properties are discussed. Autoregressive processes with
Mittag-Leffler and geometric generalized Mittag-Leffler marginal distributions
are developed. Haubold and Mathai (2000) derived a closed form representation
of the fractional kinetic equation and thermonuclear function in terms of
Mittag-Leffler function. Saxena et al (2002, 2004a,b) extended the result and
derived the solutions of a number of fractional kinetic equations in terms of
generalized Mittag-Leffler functions. These results are useful in explaining
various fundamental laws of physics. Here we develop first-order autoregressive
time series models and the properties are explored. The results have
applications in various areas like astrophysics, space sciences, meteorology,
financial modeling and reliability modeling.Comment: 12 pages, LaTe
Superconducting Properties of MgCNi3 Films
We report the magnetotransport properties of thin polycrystalline films of
the recently discovered non-oxide perovskite superconductor MgCNi3. CNi3
precursor films were deposited onto sapphire substrates and subsequently
exposed to Mg vapor at 700 C. We report transition temperatures (Tc) and
critical field values (Hc2) of MgCNi3 films ranging in thickness from 7.5 nm to
100 nm. Films thicker than ~40 nm have a Tc ~ 8 K, and an upper critical field
Hc2 ~ 14 T, which are both comparable to that of polycrystalline powders. Hall
measurements in the normal state give a carrier density, n =-4.2 x 10^22 cm^-3,
that is approximately 4 times that reported for bulk samples.Comment: submitted to PR
Angular Position of Nodes in the Superconducting Gap of Quasi-2D Heavy-Fermion Superconductor CeCoIn_5
The thermal conductivity of the heavy-fermion superconductor CeCoIn_5 has
been studied in a magnetic field rotating within the 2D planes. A clear
fourfold symmetry of the thermal conductivity which is characteristic of a
superconducting gap with nodes along the (+-pi,+-pi)-directions is resolved.
The thermal conductivity measurement also reveals a first order transition at
H_c2, indicating a Pauli limited superconducting state. These results indicate
that the symmetry most likely belongs to d_{x^2-y^2}, implying that the
anisotropic antiferromagnetic fluctuation is relevant to the superconductivity.Comment: 5 Pages, 4 figure
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