Fundamental biological processes require concurrent sharing of DNA by numerous motor proteins and complexes. Thus, collision, congestion, and roadblocks are inescapable on these busy “molecular highways.†The consequences of these traffic problems are diverse, resulting in complex cellular mechanisms to resolve threats to genome stability and ensure cellular viability. Here, we review the different types of events and the diverse consequences that an RNA polymerase may encounter during transcription.

Unusual behavior in quantum materials commonly arises from their effective low-dimensional physics, reflecting the underlying anisotropy in the spin and charge degrees of freedom. Here we introduce the magnetotropic coefficient k = ∂2F/∂θ2, the second derivative of the free energy F with respect to the magnetic field orientation θ in the crystal. We show that the magnetotropic coefficient can be quantitatively determined from a shift in the resonant frequency of a commercially available atomic force microscopy cantilever under magnetic field.

Since the discovery of the large spin Hall effect in certain heavy metals, there has been continuous interest in utilizing this spin-orbit torque (SOT) effect in constructing a non-volatile memory that can be switched by an electric current. The key to future application of this type of memory is achieving both a short write time and a low write current, which will lower the energy cost compared to existing and other emerging memory technologies.

We report very efficient spin-current generation by the spin Hall effect in the alloy Au0.25Pt0.75, which, as determined by two different direct spin-orbit torque measurements, exhibits a giant internal spin Hall ratio of ≥0.58 (antidamping spin-orbit torque efficiency of approximately 0.35 in bilayers with Co), a relatively low resistivity of approximately 83 μΩ cm, an exceptionally large spin Hall conductivity of ≥7.0×105Ω-1m-1, and a spin diffusion length of 1.7 nm.

Natural organisms use a combination of contracting muscles and inextensible fibers to transform into controllable shapes, camouflage into their surrounding environment, and catch prey. Replicating these capabilities with engineered materials is challenging because of the difficulty inmanufacturing and controlling soft material actuators with embedded fibers.

Niobium-3 Tin (Nb3Sn) is a very promising alternative material for SRF accelerator cavities. The material can achieve higher quality factors, higher temperature operation and potentially higher accelerating gradients (Eacc ˜ 96 MV/m) compared to conventional niobium. This material is formed by vaporizing Sn in a high temperature vacuum furnace and letting the Sn absorb into a Nb substrate to form a 2-3 µm Nb3Sn layer. Current Nb3Sn cavities produced at Cornell achieve Q ˜ 2 · 1010 at 4.2 K and Eacc = 17 MV/m.

In recent years, the success of serial femtosecond crystallography and the paucity of beamtime at X-ray free-electron lasers have motivated the development of serial microcrystallography experiments at storage-ring synchrotron sources. However, especially at storage-ring sources, if a crystal is too small it will have suffered significant radiation damage before diffracting a sufficient number of X-rays into Bragg peaks for peak-indexing software to determine the crystal orientation. As a consequence, the data frames of small crystals often cannot be indexed and are discarded.

We introduce superdensity operators as a tool for analyzing quantum information in spacetime. Superdensity operators encode spacetime correlation functions in an operator framework, and support a natural generalization of Hilbert space techniques and Dirac’s transformation theory as traditionally applied to standard density operators. Superdensity operators can be measured experimentally, but accessing their full content requires novel procedures. We demonstrate these statements on several examples.

A primary goal of collective population behavior studies is to determine the rules governing crowd distributions in order to predict future behaviors in new environments. Current top-down modeling approaches describe, instead of predict, specific emergent behaviors, whereas bottom-up approaches must postulate, instead of directly determine, rules for individual behaviors. Here, we employ classical density functional theory (DFT) to quantify, directly from observations of local crowd density, the rules that predict mass behaviors under new circumstances.

The effect of introducing internal cavities on protein native structure and global stability has been well documented, but the consequences of these packing defects on folding free-energy landscapes have received less attention. We investigated the effects of cavity creation on the folding landscape of the leucine-rich repeat protein pp32 by high-pressure (HP) and urea-dependent NMR and high-pressure small-angle X-ray scattering (HPSAXS).