Iron-based high-temperature superconductivity develops when the 'parent' antiferromagnetic/orthorhombic phase is suppressed, typically by introduction of dopant atoms. But their impact on atomic-scale electronic structure, although in theory rather complex, is unknown experimentally. What is known is that a strong transport anisotropy with its resistivity maximum along the crystal b axis, develops with increasing concentration of dopant atoms; this 'nematicity'vanishes when the parent phase disappears near the maximum superconducting T c.

In nanomaterials, optical anisotropies reveal a fundamental relationship between structural and optical properties. Directional optical properties can be exploited to enhance the performance of optoelectronic devices, optomechanical actuators and metamaterials. In layered materials, optical anisotropies may result from in-plane and out-of-plane dipoles associated with intra- and interlayer excitations, respectively. Here, we resolve the orientation of luminescent excitons and isolate photoluminescence signatures arising from distinct intra- and interlayer optical transitions.

In most large universities, much of the undergraduate teaching responsibility falls on graduate student teaching assistants (TAs), who are by then experienced students, but relatively inexperienced instructors. Institutions have a responsibility to offer quality instruction to undergraduate students and thus are responsible for preparing the TAs to teach.

Neuroscience is at a crossroads. Great effort is being invested into deciphering specific neural interactions and circuits. At the same time, there exist few general theories or principles that explain brain function. We attribute this disparity, in part, to limitations in current methodologies. Traditional neurophysiological approaches record the activities of one neuron or a few neurons at a time. Neurochemical approaches focus on single neurotransmitters.

A fast, high-spatial-resolution detector for high-energy microscopy work is presented. The detector uses a 2160 × 2560 CMOS chip for fast framing (up to 100 Hz in full-frame mode), coupled by a fiber optic taper to a scintillating Terbium-doped fiber optic plate for excellent stopping power even at high energies. The field of view is 7mm × 8.6mm with a resolution of 9 microns. The sensitivity is 1 e-/X-ray at 35 keV, with a read noise of 2.5 e-/pixel.

An X-ray pixel array detector (PAD) capable of framing up to 1 kHz is described. This hybrid detector is constructed from a 3-side buttable, 128×128 pixel module based upon the mixed-mode pixel array detector (MMPAD) chip developed jointly by Cornell and Area Detector Systems Corporation (Poway, CA). The chip uses a charge integrating front end for a high instantaneous count rate yet with single photon sensitivity. In-pixel circuitry utilizing a digital overflow counter extends the per frame dynamic range to >4×107 X-rays/pixel.

Motivated by recent observations, we study the stability of a Bose-Einstein condensate within a spin-dependent honeycomb lattice towards forming a "twisted superfluid" state. Our exhaustive numerical search fails to find this phase, pointing to possible non-mean-field physics. © 2013 American Physical Society.

We have developed calibration and data processing techniques optimized specifically for photon-integrating pixel array detectors (PADs). Primary effects to be calibrated are pixel gain variation and pixel area variation. Gain variations originate in pixel electronics and may be corrected for via a multiplicative factor. In contrast, area variations result from doping inhomogeneities in the sensor diode, which induce lateral fields that disturb the path of charge carriers as they traverse the diode, resulting in variation in the area mapped to each pixel, depending on the X-ray energy.

New sources and detectors are allowing scientists to look at matter with finer spatial and temporal resolutions. These experiments can produce data that are a series of severely Poisson limited snap-shots of randomly oriented samples. An extreme case of this is destructive imaging of single particles with an X-ray free-electron laser-many frames are needed for a reconstruction, but there is no a priori information associated with the frames about particle orientation.

Researchers propose building technologies to enable comprehensive mapping of neural circuit activity to understand brain function and disease.