Nanotechnology represents a new and enabling platform that promises to provide a range of innovative technologies for biological applications. ZnO nanoparticles of controlled size were synthesized, and their cytotoxicity toward different human immune cells evaluated. A differential cytotoxic response between human immune cell subsets was observed, with lymphocytes being the most resistant and monocytes being the most susceptible to ZnO nanoparticle-induced toxicity. Significant differences were also observed between previously activated memory lymphocytes and naive lymphocytes, indicating a relationship between cell-cycle potential and nanoparticle susceptibility. Mechanisms of toxicity involve the generation of reactive oxygen species, with monocytes displaying the highest levels, and the degree of cytotoxicity dependent on the extent of nanoparticle interactions with cellular membranes. An inverse relationship between nanoparticle size and cytotoxicity, as well as nanoparticle size and reactive oxygen species production was observed. In addition, ZnO nanoparticles induce the production of the proinflammatory cytokines, IFN-γ, TNF-α, and IL-12, at concentrations below those causing appreciable cell death. Collectively, these results underscore the need for careful evaluation of ZnO nanoparticle effects across a spectrum of relevant cell types when considering their use for potential new nanotechnology-based biological applications.

We demonstrate that quantum fluctuations suppress Bose-Einstein condensation of quasi-twodimensional bosons in a rapidly-rotating trap. Our conclusions rest in part on the derivation of an exact expression for the boson action in terms of vortex position coordinates, and in part on a solution of the weakly-interacting-boson Bogoliubov equations, which simplify in the rapid-rotation limit. We obtain analytic expressions for the collective-excitation dispersion, which is quadratic rather than linear. Our estimates for the boson filling factor at which the vortex lattice melts are consistent with recent exact-diagonalization calculations. PACS: 03.75.Fi, 05.30.Jp, 73.43.Cd, 73.43.Nq Recent experiments [1,2] in rapidly-rotating Bosecondensed alkali gases [3] have established the occurrence of large vortex arrays. These observations have raised a number of fundamental questions about boson vortex matter that are suggested by loose analogies with the properties of type-II superconductors in a magnetic field, and by the lore of the boson quantum Hall effect [4]. The simplicity of dilute alkali gases, and the arsenal of techniques that have been developed to manipulate them experimentally, make these systems ideal for the study of condensed-matter systems containing vortices. The proportionality between rotation frequency and rotating-frame effective magnetic field suggests [5] that there will be a maximum rotation frequency, Ω c2 , beyond which vortex-lattice states cannot occur, even at zero temperature. This expectation is consistent [6] with our understanding from quantum-Hall studies that quasi-two-dimensional (2D) charged-boson systems in strong magnetic fields form strongly-correlated fluid ground states that do not break translational symmetry. In theoretical studies of rapidly-rotating boson systems, exact-diagonalization studies tend to suggest that the bosons form fluid states, while Thomas-Fermi and mean-field studies predict vortex-lattice states. Very recently, it has been suggested [7,8], on the basis of exactdiagonalization studies using periodic boundary conditions, that the vortex-lattice state of quasi-2D bosons melts due to quantum fluctuations when the boson filling factor ν, the ratio of boson density to vortex density, is smaller than ∼ 6.In this Letter, we present a theoretical study of quantum fluctuations in rotating Bose-Einstein condensates that is based partly on a long-wavelength effective Lagrangian derived from the microscopic action, and partly on microscopic Bogoliubov-approximation calculations in the rapid-rotation limit. We find that the collective excitation energy of quasi-2D rotating bosons has a wavevector (q) dependence that is quadratic at small q, in contrast to the linear behavior ordinarily characteristic of interacting boson systems. The quadratic energy dispersion has fundamental consequences for the nature of the interacting-boson ground state: for any ν, the integral for the fraction of particles outside the condensate diverges logarithmically at small q. Thus, Bose-E...

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Nanoscale materials can have cytotoxic effects. Here we present the first combined empirical and theoretical investigation of the influence of electrostatic attraction on nanoparticle cytotoxicity. Modeling electrostatic interactions between cells and 13 nm spheres of zinc oxide nanoparticles provided insight into empirically determined variations of the minimum inhibitory concentrations between four differently charged isogenic strains of Pseudomonas aeruginosa PAO1. We conclude that controlling the electrostatic attraction between nanoparticles and their cellular targets may permit the modulation of nanoparticle cytotoxicity.

Double-layer quantum Hall systems possess interlayer phase coherence at sufficiently small layer separations, even without interlayer tunneling. When interlayer tunneling is present, application of a sufficiently strong in-plane magnetic field $B_\parallel > B_c$ drives a commensurate-incommensurate (CI) transition to an incommensurate soliton-lattice (SL) state. We calculate the Hartree-Fock ground-state energy of the SL state for all values of $B_\parallel$ within a gradient approximation, and use it to obtain the anisotropic SL stiffness, the Kosterlitz-Thouless melting temperature for the SL, and the SL magnetization. The in-plane differential magnetic susceptibility diverges as $(B_\parallel - B_c)^{-1}$ when the CI transition is approached from the SL state.Comment: 12 pages, 7 figures, to be published in Physical Review