Effect of distance on photoluminescence quenching and proximity-induced spin-orbit coupling in graphene-WSe2 heterostructures

Spin-orbit coupling (SOC) in graphene can be greatly enhanced by proximity coupling it to transition metal dichalcogenides (TMDs) such as WSe2. We find that the strength of the acquired SOC in graphene depends on the stacking order of the heterostructures when using hexagonal boron nitride (h-BN) as the capping layer, i.e., SiO2/graphene/WSe2/h-BN exhibiting stronger SOC than SiO2/WSe2/graphene/h-BN. We utilize photoluminescence (PL) as an indicator to characterize the interaction between graphene and monolayer WSe2 grown by chemical vapor deposition. We observe much stronger PL quenching in the SiO2/graphene/WSe2/h-BN stack than in the SiO2/WSe2/graphene/h-BN stack, and correspondingly a much larger weak antilocalization (WAL) effect or stronger induced SOC in the former than in the latter. We attribute these two effects to the interlayer distance between graphene and WSe2, which depends on whether graphene is in immediate contact with h-BN. Our observations and hypothesis are further supported by first-principles calculations which reveal a clear difference in the interlayer distance between graphene and WSe2 in these two stacks

Stable Ta2O5 Overlayers on Hematite for Enhanced Photoelectrochemical Water Splitting Efficiencies

Hematite (α‐Fe2O3) is one of the most promising photoanodes for water oxidation, however the efficiencies of current hematite materials remain low. Surface trap states are often reported as one of the factors which limit the activity of hematite photoelectrodes, often leading to undesirable surface pinning and trap‐mediated recombination. The deposition of ultra‐thin Al2O3 overlayers is known to enhance hematite activity through passivation of surface states, however Al2O3 is rapidly degraded at normal hematite operating pH values (pH≈13). This study reports atomic layer deposition (ALD) of Ta2O5 thin films as stable, passivating overlayers on a range of hematite photoelectrodes and demonstrates that enhanced activity correlates with observed changes in trap‐state dynamics

N-terminal acetylation promotes synaptonemal complex assembly in C. elegans

N-terminal acetylation of the first two amino acids on proteins is a prevalent cotranslational modification. Despite its abundance, the biological processes associated with this modification are not well understood. Here, we mapped the pattern of protein N-terminal acetylation in Caenorhabditis elegans, uncovering a conserved set of rules for this protein modification and identifying substrates for the N-terminal acetyltransferase B (NatB) complex. We observed an enrichment for global protein N-terminal acetylation and also specifically for NatB substrates in the nucleus, supporting the importance of this modification for regulating biological functions within this cellular compartment. Peptide profiling analysis provides evidence of cross-talk between N-terminal acetylation and internal modifications in a NAT substrate-specific manner. In vivo studies indicate that N-terminal acetylation is critical for meiosis, as it regulates the assembly of the synaptonemal complex (SC), a proteinaceous structure ubiquitously present during meiosis from yeast to humans. Specifically, N-terminal acetylation of NatB substrate SYP-1, an SC structural component, is critical for SC assembly. These findings provide novel insights into the biological functions of N-terminal acetylation and its essential role during meiosis

PMAS integral field spectroscopy of luminous infrared galaxies. I.- The atlas

In this paper we present PMAS optical (3800-7200A) IFS of the northern hemisphere portion of a volume-limited sample of 11 LIRGs. The PMAS observations typically cover the central ~5kpc and are complemented with HST/NICMOS images. For most LIRGs in our sample, the peaks of the continuum and gas (e.g., Halpha, [NII]) emissions coincide, unlike what is observed in local, strongly interacting ULIRGs. The only exceptions are galaxies with circumnuclear rings of star formation where the most luminous Halpha emitting regions are found in the rings rather than in the nuclei, and the displacements are well understood in terms of differences in the stellar populations. A large fraction of the nuclei of these LIRGs are classified as LINER and intermediate LINER/HII, or composite objects. The excitation conditions of the integrated emission depend on the relative contributions of HII regions and the diffuse emission to the line emission over the PMAS FoV. Galaxies dominated by high surface-brightness HII regions show integrated HII-like excitation. A few galaxies show slightly larger integrated [NII]/Halpha and [SII]/Halpha line ratios than the nuclear ones, probably because of more contribution from the diffuse emission. The Halpha velocity fields over the central few kpc are generally consistent, at least to first order, with rotational motions. The velocity fields of most LIRGs are similar to those of disk galaxies, in contrast to the highly perturbed fields of most local, strongly interacting ULIRGs. The peak of the Halpha velocity dispersion coincides with the position of the nucleus and is likely to be tracing mass. All these results are similar to the properties of z~1 LIRGs, and they highlight the importance of detailed studies of flux-limited samples of local LIRGs. (Abridged)Comment: Accepted for publication in Astronomy and Astrophysic

Fermion contribution to the static quantities of arbitrarily charged vector bosons

We present an analysis of the one-loop contribution from left- and right-handed fermions to the static electromagnetic properties of an arbitrarily charged no self-conjugate vector boson $V$. Particular emphasis is given to the case of a no self-conjugate neutral boson $V^0$. Regardless the electric charge of the $V$ boson, a fermionic loop can induce the two CP-even form factors but only one CP-odd. As a result the corresponding electric dipole moment is directly proportional to the magnetic quadrupole moment. The CP-odd form factor might be severely suppressed since it requires the presence of both left- and right-handed fermions. The behavior of the form factors is analyzed for several scenarios of the fermion masses in the context of the decoupling theorem.Comment: 12 pages, 3 figures, submitted to Journal of Physics

Decentralized [Hscr] ∞ controller design for large-scale civil structures

Complexities inherent to large-scale modern civil structures pose many challenges in the design of feedback structural control systems for dynamic response mitigation. With the emergence of low-cost sensors and control devices creating technologies from which large-scale structural control systems can deploy, a future control system may contain hundreds, or even thousands, of such devices. Key issues in such large-scale structural control systems include reduced system reliability, increasing communication requirements, and longer latencies in the feedback loop. To effectively address these issues, decentralized control strategies provide promising solutions that allow control systems to operate at high nodal counts. This paper examines the feasibility of designing a decentralized controller that minimizes the [Hscr] ∞ norm of the closed-loop system. [Hscr] ∞ control is a natural choice for decentralization because imposition of decentralized architectures is easy to achieve when posing the controller design using linear matrix inequalities. Decentralized control solutions are investigated for both continuous-time and discrete-time [Hscr] ∞ formulations. Numerical simulation results using a 3-story and a 20-story structure illustrate the feasibility of the different decentralized control strategies. The results also demonstrate that when realistic semi-active control devices are used in combination with the decentralized [Hscr] ∞ control solution, better performance can be gained over the passive control cases. It is shown that decentralized control strategies may provide equivalent or better control performance, given that their centralized counterparts could suffer from longer sampling periods due to communication and computation constraints. Copyright © 2008 John Wiley & Sons, Ltd.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/61866/1/862_ftp.pd

It's Not How Fat You Are, It's What You Do with It That Counts

Mechanisms underlying obesity-related metabolic disorders are poorly understood. Samuel Virtue and Antonio Vidal-Puig explore the evidence for an emerging hypothesis that attributes metabolic complications not to obesity per se, but to an individual's capacity for adipose tissue expandability