1,796 research outputs found
Phase diagram for a Bose-Einstein condensate moving in an optical lattice
The stability of superfluid currents in a system of ultracold bosons was
studied using a moving optical lattice. Superfluid currents in a very weak
lattice become unstable when their momentum exceeds 0.5 recoil momentum.
Superfluidity vanishes already for zero momentum as the lattice deep reaches
the Mott insulator(MI) phase transition. We study the phase diagram for the
disappearance of superfluidity as a function of momentum and lattice depth
between these two limits. Our phase boundary extrapolates to the critical
lattice depth for the superfluid-to-MI transition with 2% precision. When a
one-dimensional gas was loaded into a moving optical lattice a sudden
broadening of the transition between stable and unstable phases was observed.Comment: 4 figure
Phase diagram of CeVSb3 under pressure and its dependence on pressure conditions
We present temperature dependent resistivity and ac-calorimetry measurements
of CeVSb3 under pressure up to 8 GPa in a Bridgman anvil cell modified to use a
liquid medium and in a diamond anvil cell using argon as a pressure medium,
respectively. We observe an initial increase of the ferromagnetic transition
temperature Tc with pressures up to 4.5 GPa, followed by decrease of Tc on
further increase of pressure and finally its disappearance, in agreement with
the Doniach model. We infer a ferromagnetic quantum critical point around 7 GPa
under hydrostatic pressure conditions from the extrapolation to 0 K of Tc and
the maximum of the A coefficient from low temperature fits of the resistivity
\rho (T)=\rho_{0}+AT^{n}. No superconductivity under pressure was observed down
to 0.35 K for this compound. In addition, differences in the Tc(P) behavior
when a slight uniaxial component is present are noticed and discussed and
correlated to choice of pressure medium
Two-Dimensional Nature of Four-Layer Superconductors by Inequivalent Hole Distribution
The magnetization of the four-layer superconductor
CuBa_{2}Ca_{3}Cu_4O_{12-\delta} with T_c\simeq117 K is presented. The
high-field magnetization around T_c(H) follows the exact two-dimensional
scaling function given by Te\v{s}anovi\'{c} and Andreev. This feature is
contrary to the inference that the interlayer coupling becomes strong if the
number of CuO_2 planes in a unit cell increases. Also, the fluctuation-induced
susceptibility in the low-field region was analyzed by using the modified
Lawrence-Doniach model. The effective number of independently fluctuating CuO_2
layers per unit cell, g_{\rm eff}, turned out to be \simeq 2 rather than 4,
which indicated that two among the four CuO_2 layers were in states far from
their optimal doping levels. This result could explain why
CuBa_{2}Ca_{3}Cu_4O_{12-\delta} shows two-dimensional behavior.Comment: 5 pages and 4 figure
Nanorobot: Modelling And Simulation.
This research addresses the state of the art in nanorobot design and simulation focusing on the leukemia disease as well as ongoing applications on addressing the challenges posed by cancer treatment, especially chemotherapy
Catalytic Properties of Gel-Immobilized Gold Nanoparticles in Decomposition Of Hydrogen Peroxide
This paper reports the study of hydrogen peroxide decomposition catalyzed by polymer-protected gold nanoparticles (AuNPs) immobilized within polyacrylamide hydrogel. The stabilization of AuNPs was achieved using hydrophilic polymers. Embedding of AuNPs stabilized with various polymers into polyacrylamide hydrogels was carried out using three ways: “in situ” polymerization, sorption and boronhydride methods. Size, shape and morphology of AuNPs were characterized by various physicochemical methods
Impact of irreversibility and uncertainty on the timing of infrastructure projects
This paper argues that because of the irreversibility and uncertainty associated with Build - Operate - Transfer (BOT) infrastructure projects, their financial evaluation should also routinely include the determination of the value of the option to defer the construction start-up. This ensures that project viability is comprehensively assessed before any revenue or loan guarantees are considered by project sponsors to support the project. This paper shows that the framework can be used even in the context of the intuitive binomial lattice model. This requires estimating volatility directly from the evolution of the net operating income while accounting for the correlation between the revenue and costs functions. This approach ensures that the uncertainties usually associated with toll revenues, in particular, are thoroughly investigated and their impact on project viability is thoroughly assessed. This paper illustrates the usefulness of the framework with data from an actual (BOT) toll road project. The results show that by postponing the project for a couple of years the project turns out to be viable, whereas it was not without the deferral. The evaluation approach proposed therefore provides a better framework for determining when and the extent of government financial support, if any, that may be needed to support a BOT project on the basis of project economics. The analysis may also be applicable to private sector investment projects, which are characterized by irreversibility and a high rate of uncertainty
Current-phase relation of the SNS junction in a superconducting loop
We study the current-phase relation of the
superconductor/normal/superconductor (SNS) junction imbedded in a
superconducting loop. Considering the current conservation and free energy
minimum conditions, we obtain the persistent currents of the
normal/superconductor (NS) loop. At finite temperature we can explain the
experimentally observed highly non-sinusoidal currents which have maxima near
the zero external flux.Comment: 7 pages, 3 figures, version to appear in Europhys. Let
Raman Spectroscopy of Mott insulator states in optical lattices
We propose and analyse a Raman spectroscopy technique for probing the
properties of quantum degenerate bosons in the ground band of an optical
lattice. Our formalism describes excitations to higher vibrational bands and is
valid for deep lattices where a tight-binding approach can be applied to the
describe the initial state of the system. In sufficiently deep lattices,
localized states in higher vibrational bands play an important role in the
system response, and shifts in resonant frequency of excitation are sensitive
to the number of particles per site. We present numerical results of this
formalism applied to the case of a uniform lattice deep in the Mott insulator
regime.Comment: 10 pages, 3 figure
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