An overview is presented of an approach for treating cancer that uses nanoparticles to deliver heat to diseased areas after absorbing energy from a laser of the appropriate wavelength. The implications are discussed of the relationship of parameters necessary to raise the temperature to therapeutically beneficial levels. Tight focusing is required for a continuous-wave laser to sufficiently heat individual nanoparticles because of heat loss to the surrounding fluid during the period of exposure.

We study the scaling behavior of the entanglement entropy of two-dimensional conformal quantum critical systems, i.e., systems with scale-invariant wave functions. They include two-dimensional generalized quantum dimer models on bipartite lattices and quantum loop models, as well as the quantum Lifshitz model and related gauge theories. We show that under quite general conditions, the entanglement entropy of a large and simply connected subsystem of an infinite system with a smooth boundary has a universal finite contribution, as well as scale-invariant terms for special geometries.

We propose and analyze interedge tunneling in a quantum spin Hall corner junction as a means to probe the helical nature of the edge states. We show that electron-electron interactions in the one-dimensional helical edge states result in Luttinger parameters for spin and charge that are intertwined, and thus rather different from those for a quantum wire with spin rotation invariance. Consequently, we find that the four-terminal conductance in a corner junction has a distinctive form that could be used as evidence for the helical nature of the edge states.

We present a theoretical study of vortices within a harmonically trapped Bose-Einstein condensate in a rotating optical lattice. We find that proximity to the Mott insulating state dramatically affects the vortex structures. To illustrate, we give examples in which the vortices (i) all sit at a fixed distance from the center of the trap, forming a ring, or (ii) coalesce at the center of the trap, forming a giant vortex. We also model time-of-flight expansion. © 2009 The American Physical Society.

The nature of the nucleosomal barrier that regulates access to the underlying DNA during many cellular processes is not fully understood. Here we present a detailed map of histone-DNA interactions along the DNA sequence to near base pair accuracy by mechanically unzipping single molecules of DNA, each containing a single nucleosome. This interaction map revealed a distinct ∼5-bp periodicity that was enveloped by three broad regions of strong interactions, with the strongest occurring at the dyad and the other two about ∼40-bp from the dyad.

A stone tablet from New York University considered to be a copy of an inscription from Teanum Sidinicum is examined with X-ray fluorescence (XRF) and XRF imaging. Fluorescence spectra show many of the same elements seen in ancient Roman inscriptions, but the fluorescence intensity from calcium is much weaker and that from many other elements is much stronger. The weak calcium fluorescence cannot be due to X-ray absorption by other elements present, and so the tablet is unlikely to be of marble. This conclusion is supported by X-ray diffraction and electron microprobe measurements.

We propose that the upper Hubbard band (electronlike) and the Zhang-Rice singlet band (holelike) are two essential components in describing low-energy excitations of electron-doped cuprate superconductors. We find that the gap between these two bands is significantly smaller than the charge-transfer gap measured by optics and is further reduced upon doping. This indicates that the charge fluctuation is strong and the system is in the intermediate correlation regime. A two-band model is derived.

Magneto-optical methods allow us to observe the dynamics of domain wall motion, but this is intrinsically a very noisy process. We discuss a new method allowing us to reduce the measurement noise, taking advantage of the acquisition of a whole temporal sequence of images. The resulting avalanche distributions give interesting hints as to the magnetization dynamics, but are strongly dependent on the size of the observation windows chosen. We investigate the effects of window size by studying finite-size scaling, and use this to extract the fractal dimension critical exponent 1/σν.

Transcription factor binding sites are being discovered at a rapid pace. It is now necessary to turn attention towards understanding how these sites work in combination to influence gene expression. Quantitative models that accurately predict gene expression from promoter sequence will be a crucial part of solving this problem. Here we present such a model, based on the analysis of synthetic promoter libraries in yeast (Saccharomyces cerevisiae).

As a single DNA molecule is positively supercoiled under constant tension, its extension initially increases due to a negative twist-stretch coupling. The subsequent attainment of an extension maximum has previously been assumed to be indicative of the onset of a phase transition from B- to scP-DNA. Here we show that an extension maximum in fact does not coincide with the onset of a phase transition. This transition is evidenced by a direct observation of a torque plateau using an angular optical trap.