Perfect imaging: they don't do it with mirrors

Imaging with a spherical mirror in empty space is compared with the case when the mirror is filled with the medium of Maxwell's fish eye. Exact time-dependent solutions of Maxwell's equations show that perfect imaging is not achievable with an electrical ideal mirror on its own, but with Maxwell's fish eye in the regime when it implements a curved geometry for full electromagnetic waves

Collimating lenses from non-Euclidean transformation optics

Based on the non-Euclidean transformation optics, we design a thin metamaterial lens that can achieve wide-beam radiation by embedding a simple source (a point source in three-dimensional case or a line current source in two-dimensional case). The scheme is performed on a layer-by-layer geometry to convert curved surfaces in virtual space to flat sheets, which pile up and form the entire lens in physical space. Compared to previous designs, the lens has no extreme material parameters. Simulation results confirm its functionality.Comment: 12 pages, 6 figure

Optimal phase measurements with pure Gaussian states

We analyze the Heisenberg limit on phase estimation for Gaussian states. In the analysis, no reference to a phase operator is made. We prove that the squeezed vacuum state is the most sensitive for a given average photon number. We provide two adaptive local measurement schemes that attain the Heisenberg limit asymptotically. One of them is described by a positive operator-valued measure and its efficiency is exhaustively explored. We also study Gaussian measurement schemes based on phase quadrature measurements. We show that homodyne tomography of the appropriate quadrature attains the Heisenberg limit for large samples. This proves that this limit can be attained with local projective Von Neuman measurements.Comment: 9 pages. Revised version: two new sections added, revised conclusions. Corrected prose. Corrected reference

Perfect imaging with geodesic waveguides

Transformation optics is used to prove that a spherical waveguide filled with an isotropic material with radial refractive index n=1/r has radial polarized modes (i.e. the electric field has only radial component) with the same perfect focusing properties as the Maxwell Fish-Eye lens. The approximate version of that device using a thin waveguide with a homogenous core paves the way to experimentally prove perfect imaging in the Maxwell Fish Eye lens

A versatile non-radioactive assay for DNA methyltransferase activity and DNA binding

We present a simple, non-radioactive assay for DNA methyltransferase activity and DNA binding. As most proteins are studied as GFP fusions in living cells, we used a GFP binding nanobody coupled to agarose beads (GFP nanotrap) for rapid one-step purification. Immobilized GFP fusion proteins were subsequently incubated with different fluorescently labeled DNA substrates. The absolute amounts and molar ratios of GFP fusion proteins and bound DNA substrates were determined by fluorescence spectroscopy. In addition to specific DNA binding of GFP fusion proteins, the enzymatic activity of DNA methyltransferases can also be determined by using suicide DNA substrates. These substrates contain the mechanism-based inhibitor 5-aza-dC and lead to irreversible covalent complex formation. We obtained covalent complexes with mammalian DNA methyltransferase 1 (Dnmt1), which were resistant to competition with non-labeled canonical DNA substrates, allowing differentiation between methyltransferase activity and DNA binding. By comparison, the Dnmt1(C1229W) catalytic site mutant showed DNA-binding activity, but no irreversible covalent complex formation. With this assay, we could also confirm the preference of Dnmt1 for hemimethylated CpG sequences. The rapid optical read-out in a multi-well format and the possibility to test several different substrates in direct competition allow rapid characterization of sequence-specific binding and enzymatic activity

Metacognitive self-reflectivity moderates the relationship between distress tolerance and empathy in schizophrenia

Deficits in empathy seen in schizophrenia are thought to play a major role in the social dysfunction seen in the disorder. However, little work has investigated potential determinants of empathic deficits. This study aimed to fill that gap by examining the effects of two variables on empathy – distress tolerance and metacognitive self-reflectivity. Fifty-four people with schizophrenia-spectrum disorders receiving services at an urban VA or community mental health center were assessed for empathy, metacognition, and distress tolerance. Bivariate correlations and moderation methods were used to ascertain associations amongst these variables and examine interactions. Results revealed that, against hypotheses, empathy was not related at the bivariate level to either distress tolerance or metacognitive self-reflectivity. However, consistent with hypotheses, moderation analyses revealed that participants with higher self-reflectivity showed no relationship between distress tolerance and empathy, while those with lower self-reflectivity showed a relationship such that reduced ability to tolerate distress predicted reduced empathy. Taken together, results of this study suggest that lack of distress tolerance can negatively affect empathy in people with schizophrenia with lesser capacity for metacognitive self-reflection; thus, fostering self-reflectivity may help overcome that negative impact. Future work is needed investigating the impact of metacognitively-tailored interventions on empathy in this population

Quantum levitation by left-handed metamaterials

Left-handed metamaterials make perfect lenses that image classical electromagnetic fields with significantly higher resolution than the diffraction limit. Here we consider the quantum physics of such devices. We show that the Casimir force of two conducting plates may turn from attraction to repulsion if a perfect lens is sandwiched between them. For optical left-handed metamaterials this repulsive force of the quantum vacuum may levitate ultra-thin mirrors

Scheme to measure squeezing and phase properties of a harmonic oscillator

We propose a simple scheme to measure squeezing and phase properties of a harmonic oscillator. We treat in particular the case of a the field, but the scheme may be easily realized in ion traps. It is based on integral transforms of measured atomic properties as atoms exit a cavity. We show that by measuring atomic polarizations it is possible, after a given integration, to measure several properties of the field.Comment: Presented at XI Central European Workshop on Quantum Optics, Trieste, Italy, 18-20 July, 200

Quantum homodyne tomography with a priori constraints

I present a novel algorithm for reconstructing the Wigner function from homodyne statistics. The proposed method, based on maximum-likelihood estimation, is capable of compensating for detection losses in a numerically stable way.Comment: 4 pages, REVTeX, 2 figure