ReaxFF Reactive Force Field for the Y-Doped BaZrO_3 Proton Conductor with Applications to Diffusion Rates for Multigranular Systems

Proton-conducting perovskites such as Y-doped BaZrO3 (BYZ) are promising candidates as electrolytes for a proton ceramic fuel cell (PCFC) that might permit much lower temperatures (from 400 to 600 °C). However, these materials lead to relatively poor total conductivity (∼10^−4 S/cm) because of extremely high grain boundary resistance. In order to provide the basis for improving these materials, we developed the ReaxFF reactive force field to enable molecular dynamics (MD) simulations of proton diffusion in the bulk phase and across grain boundaries of BYZ. This allows us to elucidate the atomistic structural details underlying the origin of this poor grain boundary conductivity and how it is related to the orientation of the grains. The parameters in ReaxFF were based entirely on the results of quantum mechanics (QM) calculations for systems related to BYZ. We apply here the ReaxFF to describe the proton diffusion in crystalline BYZ and across grain boundaries in BYZ. The results are in excellent agreement with experiment, validating the use of ReaxFF for studying the transport properties of these membranes. Having atomistic structures for the grain boundaries from simulations that explain the overall effect of the grain boundaries on diffusion opens the door to in silico optimization of these materials. That is, we can now use theory and simulation to examine the effect of alloying on both the interfacial structures and on the overall diffusion. As an example, these calculations suggest that the reduced diffusion of protons across the grain boundary results from the increased average distances between oxygen atoms in the interface, which necessarily leads to larger barriers for proton hopping. Assuming that this is the critical issue in grain boundary diffusion, the performance of BYZ for multigranular systems might be improved using additives that would tend to precipitate to the grain boundary and which would tend to pull the oxygens atoms together. Possibilities might be to use a small amount of larger trivalent ions, such as La or Lu or of tetravalent ions such as Hf or Th. Since ReaxFF can also be used to describe the chemical processes on the anode and cathode and the migration of ions across the electrode-membrane interface, ReaxFF opens the door to the possibility of atomistic first principles predictions on models of a complete fuel cell

Characterization of four subtypes in morphologically normal tissue excised proximal and distal to breast cancer

Widespread mammographic screening programs and improved self-monitoring allow for breast cancer to be detected earlier than ever before. Breast-conserving surgery is a successful treatment for select women. However, up to 40% of women develop local recurrence after surgery despite apparently tumor-free margins. This suggests that morphologically normal breast may harbor early alterations that contribute to increased risk of cancer recurrence. We conducted a comprehensive transcriptomic and proteomic analysis to characterize 57 fresh-frozen tissues from breast cancers and matched histologically normal tissues resected proximal to (<2 cm) and distant from (5–10 cm) the primary tumor, using tissues from cosmetic reduction mammoplasties as baseline. Four distinct transcriptomic subtypes are identified within matched normal tissues: metabolic; immune; matrisome/epithelial–mesenchymal transition, and non-coding enriched. Key components of the subtypes are supported by proteomic and tissue composition analyses. We find that the metabolic subtype is associated with poor prognosis (p < 0.001, HR6.1). Examination of genes representing the metabolic signature identifies several genes able to prognosticate outcome from histologically normal tissues. A subset of these have been reported for their predictive ability in cancer but, to the best of our knowledge, these have not been reported altered in matched normal tissues. This study takes an important first step toward characterizing matched normal tissues resected at pre-defined margins from the primary tumor. Unlocking the predictive potential of unexcised tissue could prove key to driving the realization of personalized medicine for breast cancer patients, allowing for more biologically-driven analyses of tissue margins than morphology alone

Pervasively Distributed Copyright Enforcement

In an effort to control flows of unauthorized information, the major copyright industries are pursuing a range of strategies designed to distribute copyright enforcement functions across a wide range of actors and to embed these functions within communications networks, protocols, and devices. Some of these strategies have received considerable academic and public scrutiny, but much less attention has been paid to the ways in which all of them overlap and intersect with one another. This article offers a framework for theorizing this process. The distributed extension of intellectual property enforcement into private spaces and throughout communications networks can be understood as a new, hybrid species of disciplinary regime that locates the justification for its pervasive reach in a permanent state of crisis. This hybrid regime derives its force neither primarily from centralized authority nor primarily from decentralized, internalized norms, but instead from a set of coordinated processes for authorizing flows of information. Although the success of this project is not yet assured, its odds of success are by no means remote as skeptics have suggested. Power to implement crisis management in the decentralized marketplace for digital content arises from a confluence of private and public interests and is amplified by the dynamics of technical standards processes. The emergent regime of pervasively distributed copyright enforcement has profound implications for the production of the networked information society

Macroscale and Nanoscale Photoelectrochemical Behavior of p-Type Si(111) Covered by a Single Layer of Graphene or Hexagonal Boron Nitride

Two-dimensional (2D) materials may enable a general approach to the introduction of a dipole at a semiconductor surface as well as control over other properties of the double layer at a semiconductor/liquid interface. Vastly different properties can be found in the 2D materials currently studied due in part to the range of the distribution of density-of-states. In this work, the open-circuit voltage (V_(oc)) of p-Si–H, p-Si/Gr (graphene), and p-Si/h-BN (hexagonal boron nitride) in contact with a series of one-electron outer-sphere redox couples was investigated by macroscale measurements as well as by scanning electrochemical cell microscopy (SECCM). The band gaps of Gr and h-BN (0–5.97 eV) encompass the wide range of band gaps for 2D materials, so these interfaces (p-Si/Gr and p-Si/h-BN) serve as useful references to understand the behavior of 2D materials more generally. The value of V_(oc) shifted with respect to the effective potential of the contacting solution, with slopes (ΔV_(oc)/ΔE_(Eff)) of −0.27 and −0.38 for p-Si/Gr and p-Si/h-BN, respectively, indicating that band bending at the p-Si/h-BN and p-Si/Gr interfaces responds at least partially to changes in the electrochemical potential of the contacting liquid electrolyte. Additionally, SECCM is shown to be an effective method to interrogate the nanoscale photoelectrochemical behavior of an interface, showing little spatial variance over scales exceeding the grain size of the CVD-grown 2D materials in this work. The measurements demonstrated that the polycrystalline nature of the 2D materials had little effect on the results and confirmed that the macroscale measurements reflected the junction behavior at the nanoscale

A Historical and Political Review of the Response to the 2015-2016 Zika Outbreak in Puerto Rico

The Zika virus was first identified in 1948 but was relatively unknown until 2015, when Brazil began to report a significant increase in the numbers of babies with congenital defects. It is a virus that is primarily transmitted by mosquitos and primarily effects the nervous system. With its tropical climate and constant mosquito presence, Puerto Rico was the location of a massive outbreak during 2015-2016. However, the response to the outbreak faced several hurdles despite Brazil already reporting an increase in microcephaly. The purpose of this review is to examine the political and historical factors that hampered the initial response to the 2015 Zika outbreak in Puerto Rico and how they affected the perceived risk of the Zika virus. It is crucial that intensive health education campaigns and vaccine development continue in order to ensure that a second outbreak does not occur and result in a greater number of babies diagnosed with Congenital Zika Syndrome