We survey the use of spectroscopic imaging scanning tunneling microscopy (SI-STM) to probe the electronic structure of underdoped cuprates. Two distinct classes of electronic states are observed in both the d-wave superconducting (dSC) and the pseudogap (PG) phases. The first class consists of the dispersive Bogoliubov quasiparticle excitations of a homogeneous d-wave superconductor, existing below a lower energy scale E = Δ0.

High-pressure methods for solving protein structures by X-ray crystallography and NMR are maturing. These techniques are beginning to impact our understanding of thermodynamic and structural features that define not only the protein's native conformation, but also the higher free energy conformations. The ability of high-pressure methods to visualize these mostly unexplored conformations provides new insight into protein function and dynamics.

We use atomic force microscopy to image grain boundaries and ripples in graphene membranes obtained by chemical vapor deposition. Nanoindentation measurements reveal that out-of-plane ripples effectively soften graphene's in-plane stiffness. Furthermore, grain boundaries significantly decrease the breaking strength of these membranes. Molecular dynamics simulations reveal that grain boundaries are especially weakening when subnanometer voids are present in the lattice. Finally, we demonstrate that two graphene membranes brought together form membranes with higher resistance to breaking.

The helicase and primase activities of the hexameric ringshaped T7 gp4 protein reside in two separate domains connected by a linker region. This linker region is part of the subunit interface between monomers, and point mutations in this region have deleterious effects on the helicase functions. One such linker region mutant, A257T, is analogous to the A359T mutant of the homologous human mitochondrial DNA helicase Twinkle, which is linked to diseases such as progressive external opthalmoplegia.

Over 20 years since the discovery of high temperature superconductivity in cuprates (Bednorz and Müller, 1986 [1]), the first convincing observation of quantum oscillations in underdoped YBa2Cu3O6.5 (Doiron-Leyraud et al., 2007 [2]) has deeply changed the theoretical landscape relevant to these materials. The Fermi surface is a basic concept of solid state physics, which underpins most physical properties (electrical, thermal, optical, etc.) of a metal. Even in the presence of interactions, this fundamental concept remains robust.

The high intensity of free-electron X-ray light sources may enable structure determinations of viruses or even individual proteins without the encumbrance of first forming crystals. This note compares two schemes of non-crystalline diffraction data collection that have been proposed: serial single-shot data from individual particles, and averaged cross-correlation data from particle ensembles. The information content of these schemes is easily compared and we show that the single-shot approach, although experimentally more challenging, is always superior in this respect.

We calculate the single-particle spectral density of a normal (nonsuperfluid) two-component gas of fermions in the BCS-BEC crossover within a T-matrix approximation. We review how noncondensed pairs lead to a spectral density reminiscent of the ordered state, and explore how a gaplike feature in the spectrum evolves as one changes the polarization of the gas. As the gas is polarized, we find that this pseudogap becomes more diffuse and moves away from the Fermi level, reflecting the fact that fewer pairs are present but that they still play an important role in the excitations.

Much controversy exists regarding the structural organization of the yeast centromeric nucleosome and the role of the nonhistone protein, Scm3, in its assembly and architecture. Here we show that the substitution of H3 with its centromeric variant Cse4 results in octameric nucleosomes that organize DNA in a left-handed superhelix. We demonstrate by single-molecule approaches, micrococcal nuclease digestion and small-angle X-ray scattering that Cse4-nucleosomes exhibit an open conformation with weakly bound terminal DNA segments.

Using a high-sensitivity torsional oscillator (TO) technique, we mapped the rotational and relaxational dynamics of solid helium-4 (4He) throughout the parameter range of the proposed supersolidity. We found evidence that the same microscopic excitations controlling the torsional oscillator motions are generated independently by thermal and mechanical stimulation. Moreover, a measure for the relaxation times of these excitations diverges smoothly without any indication for a critical temperature or critical velocity of a supersolid transition.