Publications

Despite the promise of precisely targeted or otherwise functionalized polymeric particulate drug delivery vehicles, typical biocompatible particles are generally not amenable to facile and selective surface modification. Herein, we report the development of a simple, mild, and chemoselective strategy for the conjugation of biologically active molecules to the surface of dextran-based microparticles. Alkoxyamine-bearing reagents were used to form stable oxime conjugates with latent aldehyde functionality present in reducing carbohydrate chain ends. We demonstrate the functionalization of dextran-based microparticles with a fluorophore as well as a cell-penetrating peptide sequence, which facilitated the delivery of cargo to nonphagocytic cells leading to a 60-fold increase in the expression of a reporter gene when plasmid DNA-loaded particles were used.

A giant bandgap reduction in layered GaTe is demonstrated. Chemisorption of oxygen to the Te-terminated surfaces produces significant restructuring of the conduction band resulting in a bandgap below 0.8 eV, compared to 1.65 eV for pristine GaTe. Localized partial recovery of the pristine gap is achieved by thermal annealing, demonstrating that reversible band engineering in layered semiconductors is accessible through their surfaces.

Abstract not Available.

Fish, reptiles, and mammals can possess flexible dermal armor for protection. Here we seek to find the means by which Nature derives its protection by examining the scales from several fish ( Atractosteus spatula , Arapaima gigas , Polypterus senegalus, Morone saxatilis, Cyprinius carpio) , and osteoderms from armadillos, alligators, and leatherback turtles. Dermal armor has clearly been developed by convergent evolution in these different species. In general, it has a hierarchical structure with collagen fibers joining more rigid units (scales or osteoderms), thereby increasing flexibility without significantly sacrificing strength, in contrast to rigid monolithic mineral composites. These dermal structures are also multifunctional, with hydrodynamic drag (in fish), coloration for camouflage or intraspecies recognition, temperature and fluid regulation being other important functions. The understanding of such flexible dermal armor is important as it may provide a basis for new synthetic, yet bioinspired, armor materials.

Abstract The Wide Field InfraRed Survey Telescope ( WFIRST ) was the highest-ranked large space-based mission of the 2010 New Worlds , New Horizons decadal survey. It is now a NASA mission in formulation with a planned launch in the mid 2020s. A primary mission objective is to precisely constrain the nature of dark energy through multiple probes, including Type Ia supernovae (SN Ia). Here, we present the first realistic simulations of the WFIRST SN survey based on current hardware specifications and using open-source tools. We simulate SN light curves and spectra as viewed by the WFIRST wide-field channel (WFC) imager and integral field channel (IFC) spectrometer, respectively. We examine 11 survey strategies with different time allocations between the WFC and IFC, two of which are based upon the strategy described by the WFIRST Science Definition Team, which measures SN distances exclusively from IFC data. We propagate statistical and, crucially, systematic uncertainties to predict the Dark Energy Task Force figure of merit (FoM) for each strategy. Of the strategies investigated, we find the most successful to be WFC focused. However, further work in constraining systematics is required to fully optimize the use of the IFC. Even without improvements to other cosmological probes, the WFIRST SN survey has the potential to increase the FoM by more than an order of magnitude from the current values. Although the survey strategies presented here have not been fully optimized, these initial investigations are an important step in the development of the final hardware design and implementation of the WFIRST mission.

We demonstrate the selective, pulsed-laser deposition of hexagonal GaS and monoclinic Ga2S3 films on sapphire substrates from a single Ga2S3 target in high-vacuum conditions. Growth at substrate temperatures below 550 °C causes GaS film formation, which indicates non-stoichiometric transfer from the target to the film. Surprisingly, stoichiometric transfer occurs at substrate temperatures above 650 °C with monoclinic Ga2S3 as the preferred, higher S-content phase. Through a series of growth and annealing experiments, we show that GaS nucleation under S-deficient conditions leads to the preferred growth of this layered, hexagonal phase below 550 °C. Furthermore, GaS films annealed above 650 °C under high vacuum are transformed to Ga2S3, reflecting the greater stability of the monoclinic phase. By first growing Ga2S3 at a higher temperature and subsequently growing GaS at a lower temperature, we can fabricate GaS/Ga2S3 heterostructures in a single growth process.

The paper describes an analog current mode realization of Discrete-Time Cellular Neural Networks (DTCNNs) with high cell density, which have local analog and local logic memory. Hence, some important parts of the CNN Universal Machine concept are implemented. The computation speed can be adjusted simply to the application by changing the clock rate. The circuit components are described in detail and SPICE level 2 simulation results are given for the ORBIT 2.0 /spl mu/m process. A layout has been designed for a chip with 12 by 12 cells on a square grid realizing a one-neighborhood with 9 feedback and 9 control coefficients. The cell size is 619 /spl mu/m by 425 /spl mu/m and the simulated speed is between 1 MHz and 10 MHz depending on the minimum value of the state current. For the latter this leads to a simulated performance of 25.9 10/sup 9/ XPS for a single chip operation with an effective area of 0.379 cm/sup 2/ and a worst case power consumption of 0.86 W. Another important feature of the chip is its capability for a spatial cascaded connection.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Throughout the history of Li-ion batteries, cathode materials with high energy density have been sought from well-ordered oxide compounds in which lithium and other cations occupy distinct sites within an oxygen FCC framework.[1,2] In contrast, cation-disordered materials have received only a limited attention as cathodes because lithium diffusion tends to be limited by their structure, resulting in poor cycling performance.[3] However, recent studies have shown that cation-disordered materials can in fact deliver higher energy densities than the ordered materials once enough excess lithium ( x &gt; 0.1 in Li1+ x TM1- x O2, TM: transition metal) is introduced to their structure, opening a new search space for high energy density Li-ion cathodes.[4,5] The understanding of disordered cathodes was first made with percolation theory which links the composition of a compound to the population of Li diffusion channels with low barriers.[4,5] In rocksalt-type oxides, Li diffusion takes place between two octahedral sites through a face-sharing tetrahedral site. Li+ ion in this tetrahedral site in the activate state in diffusion, whose electrostatic energy largely determines the diffusion barrier. Hence, (i) the oxidation states of species in the face-sharing octahedral sites and (ii) the tetrahedron height, along which the activated Li+ ion relaxes away the strong electrostatic repulsion from face-sharing octahedral species, largely determine the activity of a Li diffusion channel. [4] In the disordered rocksalt structure with small tetrahedron heights, it was found that only the diffusion channel through which an activated Li+ ion shares faces with no transition metal ions (0-TM channels) has low Li diffusion barriers. However, for the 0-TM channel to dominate macroscopic Li diffusion, the channel must be percolating in a crystal structure, such that every Li hopping occurs through the channel. Percolation theory predicts that Li excess introduces such 0-TM percolation, and hence Li-excess disordered cathodes should allow for facile Li diffusion.(Fig. 1a)[4] Consistent to the theory, recently developed cation-disordered Li-excess cathodes (e.g. Li1.211Mo0.467Cr0.3O2, Li1.3Mn0.4Nb0.3O2) deliver high capacity and energy density with facile Li diffusion.[4,6] However, percolation theory alone cannot completely guide the design of high capacity disordered cathodes because it does not take redox process into account. While percolation theory predicts higher Li-excess contents should lead to better disordered cathodes, higher Li excess necessarily leads to lower transition metal contents hence their redox capacity.[7] Therefore, unless transition metals can exchange multiple electrons or oxygen redox can reversibly occur, the electron-storage capacity should decrease with Li excess, which is unwanted. In this presentation, we explain how lithium excess can affect both Li diffusion and redox process in disordered cathodes using percolation theory and ligand field theory, respectively.(Fig. 1b, 1c)[4,8] Based on this understanding, we will show that Li diffusion and redox process in the materials are highly correlated hence need to be considered simultaneously. We further demonstrate how such complete understanding can be used to explain the performance of recently developed high capacity disordered cathodes (e.g. Li-Ni-Ti-Mo oxides) and to design improved disordered cathode materials.[7,8] References [1] K. Kang, Y. S. Meng, J. Bréger, C. P. Grey, G. Ceder, Science 311, 977–980 (2006). [2] M. M. Thackeray, P. J. Johnson, L. A. De Picciotto, P. G. Bruce, J. B. Goodenough, Mater. Res. Bull.19, 179–187 (1984). [3] M. N. Obrovac, O. Mao, J. R. Dahn, Solid State Ion.112, 9–19 (1998). [4] J. Lee, A. Urban, X. Li, D. Su, G. Hautier, G. Ceder, Science 343, 519–522 (2014). [5] A. Urban, J. Lee, G. Ceder, Adv. Energy Mater.4, 1400478 (2014). [6] N. Yabuuchi et al., PNAS 112, 7650–7655 (2015). [7] J. Lee, D.-H. Seo, M. Balasubramania, N. Twu, X. Li, G. Ceder, Energy Environ. Sci.8, 3255 (2015). [8] D.-H. Seo‡, J. Lee‡, A. Urban, R. Malik, SY. Kang, G. Ceder, Nature Chem., in press (2016) (‡ equal contribution) Figure 1

We present photometry, spectroscopy, and host-galaxy integral-field spectroscopy of the Type II supernova (SN) 2016esw in CGCG~229-009 from the first day after the explosion up to 120 days. Its light-curve shape is similar to that of a typical SN II; however, SN 2016esw is near the high-luminosity end of the SN II distribution, with a peak of $M^{\rm max}_{V}=-18.36$ mag. The $V$-band light curve exhibits a long recombination phase for a SN II (similar to the long-lived plateau of SN 2004et). Considering the well-known relation between the luminosity and the plateau decline rate, SN 2016esw should have a $V$-band slope of $\sim 2.10$ mag (100 days)$^{-1}$; however, SN 2016esw has a substantially flatter plateau with a slope of $1.01\pm 0.26$ mag (100 days)$^{-1}$, perhaps indicating that interacting Type II supernovae are not useful for cosmology. At 19.5 days post-explosion, the spectrum presents a boxy H$\alpha$ emission line with flat absorption profiles, suggesting interaction between the ejecta and circumstellar matter. Finally, based on the spectral properties, SN 2016esw shows similarities with the luminous and interacting SN 2007pk at early epochs, particularly in terms of observable line features and their evolution.

Improvement in endurance exercise performance in adult humans following sprint interval training (SIT) has been attributed to mitochondrial (mito) biogenesis. However, this conclusion has been inferred from mito biogenic signaling, and not synthesis of new mito protein. Muscle protein synthesis (MPS) and mito biogenic responses to SIT have not been measured, nor have sex‐specific responses. We hypothesized that males and females would have similar rates of MPS, mito biogenesis, and overall individual protein synthetic rates after 9 sessions of SIT. 21 healthy adults (11 male, 10 female, 23±1 years, body mass index: 22.8±0.6 kg/m 2 ; mean±SE) were orally administered deuterium oxide (D 2 O) for measurements of protein synthetic rates for 4 weeks while completing SIT. Maximal oxygen uptake increased (males from 43.4±2.1 to 44.0±2.3; females from 39.5±0.9 to 42.5±1.3 ml/kg/min; P =0.002) following SIT. MPS was greater in males compared with females in the mixed (150%; P &lt;0.001), cytosolic (135%; P =0.038), and mito (135%; P =0.056) fractions. Kinetic proteomics identified 60 proteins that responded differently to SIT between the sexes ( P &lt;0.05); all were greater in males. For the first time, we document greater MPS and mito biogenesis in response to SIT in males compared with females, and present the first data describing the synthetic response of individual proteins in humans during exercise training. Grant Funding Source : Supported by the Office of Naval Research (N00014‐10‐1‐0247)