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Observation of light-by-light scattering in ultraperipheral Pb+Pb collisions with the ATLAS detector
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SKYSURF: Constraints on Zodiacal Light and Extragalactic Background Light through Panchromatic HST All-sky Surface-brightness Measurements: II. First Limits on Diffuse Light at 1.25, 1.4, and 1.6 μm
We present the first results from the HST Archival Legacy project "SKYSURF." As described in Windhorst et al., SKYSURF utilizes the large HST archive to study the diffuse UV, optical, and near-IR backgrounds and foregrounds in detail. Here, we utilize SKYSURF's first sky-surface-brightness measurements to constrain the level of near-IR diffuse Extragalactic Background Light (EBL) in three near-IR filters (F125W, F140W, and F160W). This is done by comparing our preliminary sky measurements of >30,000 images to zodiacal light models, carefully selecting the darkest images to avoid contamination from stray light. Our sky-surface-brightness measurements have been verified to an accuracy of better than 1%, which when combined with systematic errors associated with HST, results in sky-brightness uncertainties of ∼ 2%–4% ≃ 0.005 MJy sr−1 in each image. When compared to the Kelsall et al. zodiacal model, an isotropic diffuse background of ∼30 nW m−2 sr−1 remains, whereas using the Wright zodiacal model results in no discernible diffuse background. Based primarily on uncertainties in the foreground model subtraction, we present limits on the amount of diffuse EBL of 29, 40, and 29 nW m−2 sr−1, for F125W, F140W, and F160W, respectively. While this light is generally isotropic, our modeling at this point does not distinguish between a cosmological origin or a solar system origin (such as a dim, diffuse, spherical cloud of cometary dust).
Mass spectrometry footprinting reveals the structural rearrangements of cyanobacterial orange carotenoid protein upon light activation
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Design Tool for Estimating Chemical Hydrogen Storage System Characteristics for Light-Duty Fuel Cell Vehicles
The U.S. Department of Energy (DOE) has developed a vehicle framework model to simulate fuel cell-based light-duty vehicle operation for various hydrogen storage systems. This transient model simulates the performance of the storage system, fuel cell, and vehicle for comparison to DOE’s Technical Targets using four drive cycles/profiles. Chemical hydrogen storage models have been developed for the Framework model for both exothermic and endothermic materials. Despite the utility of such models, they require that material researchers input system design specifications that cannot be easily estimated. To address this challenge, a design tool has been developed that allows researchers to directly enter kinetic and thermodynamic chemical hydrogen storage material properties into a simple sizing module that then estimates the systems parameters required to run the storage system model. Additionally, this design tool can be used as a standalone executable file to estimate the storage system mass and volume outside of the framework model and compare it to the DOE Technical Targets. These models will be explained and exercised with existing hydrogen storage materials.
Techno-economic analysis and life-cycle analysis of two light-duty bio-blendstocks: isobutanol and aromatic rich hydrocarbons
Isobutanol and aromatic-rich hydrocarbons (ARHC) are two biomass-derived high octane blendstocks that could be blended with petroleum gasoline for use in optimized spark-ignition engines in light-duty vehicles, potentially increasing engine efficiency. To evaluate technology readiness, economic viability, and environmental impacts of these technologies, we use detailed techno-economic analysis (TEA) and life-cycle analysis (LCA). We assumed isobutanol is produced via biochemical conversion of an herbaceous feedstock blend while ARHC is produced via thermochemical conversion of a woody feedstock blend.The minimum estimated fuel selling price (MFSP) of isobutanol ranged from $5.57/gasoline gallon equivalent (GGE) based on today’s technology to $4.22/GGE with technology advancements. The MFSP of ARHC could decline from $5.20/GGE based on today’s technology to $4.20/GGE as technology improves. Both isobutanol and ARHC offer about 73% GHG emission reduction relative to petroleum gasoline per LCA of these two bio-blendstocks. On the other hand, water consumption in the production of both bio-blendstocks exceeds that of conventional gasoline although process engineering offers routes to cutting water consumption. Over their life cycles, both isobutanol and ARHC emit more NOx and PM2.5 than petroleum gasoline.Improving the energy efficiency and lowering air emissions from agricultural equipment will reduce the life-cycle air pollutant emissions of these bio-blendstocks.
Long-lived light mediator to dark matter and primordial small scale spectrum
We calculate the early universe evolution of perturbations in the dark matter energy density in the context of simple dark sector models containing a GeV scale light mediator. We consider the case that the mediator is long-lived, with lifetime up to a second, and before decaying it temporarily dominates the energy density of the universe. We show that for primordial perturbations that enter the horizon around this period, the interplay between linear growth during matter domination and collisional damping can generically lead to a sharp peak in the spectrum of dark matter density perturbation. As a result, the population of the smallest DM halos gets enhanced. Possible implications of this scenario are discussed.
Enhanced Light-Harvesting Capacity by Micellar Assembly of Free Accessory Chromophores and LH1-like Antennas
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National Synchrotron Light Source II storage ring vacuum systems
The National Synchrotron Light Source II, completed in 2014, is a 3-GeV synchrotron radiation (SR) facility at Brookhaven National Laboratory and has been in steady operation since. With a design electron current of 500 mA and subnanometer radians horizontal emittance, this 792-m circumference storage ring is providing the highest flux and brightness x-ray beam for SR users. The majority of the storage ring vacuum chambers are made of extruded aluminium. Chamber sections are interconnected using low-impedance radiofrequency shielded bellows. SR from the bending magnets is intercepted by water-cooled compact photon absorbers resided in the storage ring chambers. This paper presents the design of the storage ring vacuum system, the fabrication of vacuum chambers and other hardware, the installation, the commissioning, and the continuing beam conditioning of the vacuum systems.
Black silicon solar thin-film microcells integrating top nanocone structures for broadband and omnidirectional light-trapping
Recently developed classes of monocrystalline silicon solar microcells (μ-cell) can be assembled into modules with characteristics (i.e., mechanically flexible forms, compact concentrator designs, and high-voltage outputs) that would be impossible to achieve using conventional, wafer-based approaches. In this paper, we describe a highly dense, uniform and non-periodic nanocone forest structure of black silicon (bSi) created on optically-thin (30 μm) μ-cells for broadband and omnidirectional light-trapping with a lithography-free and high-throughput plasma texturizing process. With optimized plasma etching conditions and a silicon nitride passivation layer, black silicon μ-cells, when embedded in a polymer waveguiding layer, display dramatic increases of as much as 65.7% in short circuit current, as compared to a bare silicon device. Here, the conversion efficiency increases from 8.1% to 11.5% with a small drop in open circuit voltage and fill factor.
Increased light-use efficiency in northern terrestrial ecosystems indicated by CO 2 and greening observations: INCREASE IN NH LIGHT USE EFFICIENCY
Observations show an increasing amplitude in the seasonal cycle of CO2 (ASC) north of 45°N of 56 ± 9.8% over the last 50 years and an increase in vegetation greenness of 7.5–15% in high northern latitudes since the 1980s. However, the causes of these changes remain uncertain. Historical simulations from terrestrial biosphere models in the Multiscale Synthesis and Terrestrial Model Intercomparison Project are compared to the ASC and greenness observations, using the TM3 atmospheric transport model to translate surface fluxes into CO2 concentrations. We find that the modeled change in ASC is too small but the mean greening trend is generally captured. Modeled increases in greenness are primarily driven by warming, whereas ASC changes are primarily driven by increasing CO2. We suggest that increases in ecosystem-scale light use efficiency (LUE) have contributed to the observed ASC increase but are underestimated by current models. We highlight potential mechanisms that could increase modeled LUE.
Construction of multi-shelled Bi2WO6 hollow microspheres with enhanced visible light photo-catalytic performance
Highlights: • Bi{sub 2}WO{sub 6} with multi-shelled hollow microstructure was successfully fabricated and the use of ethylene glycol is a key factor. • Bi{sub 2}O{sub 3}/Bi{sub 2}WO{sub 6} composite with multi-shelled hollow structure were also fabricated when concentration of solution was reduced. • Enhanced visible light photocatalytic performance was observed, which are believed due to the unique hollow microstructure. - Abstract: As a promising structure in enhancing the photo-catalytic performance of the materials, hollow-shell structure still faces the great challenge of constructing an effective architecture for catalytic application. Herein, multi-shelled hollow microspheres of the visible-light photo-catalyst Bi{sub 2}WO{sub 6} with shells up to the triple (BWO-MSH), have been synthesized by using a facile and effective carbonaceous template route. Intriguingly, the photo-catalytic reaction rate constant of BWO-MSH sample is nearly 16 times higher than the Bi{sub 2}WO{sub 6} prepared through solid-state reaction (BWO-SSR). The single-, double-shelled Bi{sub 2}WO{sub 6} microspheres (Broken) could only be synthesized with lower quality (synthesized with many broken species), and their photo-catalytic performance was nearly the same poor as the BWO-SSR sample. Furthermore, multi-shelled hollow microsphere of Bi{sub 2}O{sub 3}/Bi{sub 2}WO{sub 6} (BO/BWO-MSH) composite was also synthesized. The present work not only extends the scope of high-performance complex mixed metal oxides with multi-shelled microstructures, but also brings a good reference to engineer other impressive photo-catalyst.
Fermi energy tuning with light to control doping profiles during epitaxy
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Aberrant Assembly Complexes of the Reaction Center Light Harvesting 1 PufX (RC-LH1-Pufx) Core Complex of Rhodobacter sphaeroides Imaged by Atomic Force Microscopy
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Collaborative development of diffraction-limited beamline optical systems at US DOE light sources
An ongoing collaboration among four US Department of Energy National Laboratories has demonstrated key technology prototypes and software modeling tools required for new high-coherent flux beamline optical systems. New free electron laser (FEL) and diffraction-limited storage ring (DLSR) light sources demand wavefront preservation from source to sample to achieve and maintain optimal performance. Fine wavefront control was achieved using a novel, roomtemperature cooled mirror system called REAL (resistive element adjustable length) that combines cooling with applied, spatially variable auxiliary heating. Single-grating shearing interferometry (also called Talbot interferometry) and Hartmann wavefront sensors were developed and used for optical characterization and alignment on several beamlines, across a range of photon energies. Demonstrations of non-invasive hard x-ray wavefront sensing were performed using a thin diamond single-crystal as a beamsplitter.
RfpA, RfpB, and RfpC are the Master Control Elements of Far-Red Light Photoacclimation (FaRLiP)
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Slow light enhanced singlet exciton fission solar cells with a 126% yield of electrons per photon
Singlet exciton fission generates two triplet excitons per absorbed photon. It promises to increase the power extracted from sunlight without increasing the number of photovoltaic junctions in a solar cell. We demonstrate solar cells with an external quantum efficiency of 126% by enhancing absorption in thin films of the singlet exciton fission material pentacene. The device structure exploits the long photon dwell time at the band edge of a distributed Bragg reflector to achieve enhancement over a broad range of angles. Measuring the reflected light from the solar cell establishes a lower bound of 137% for the internal quantum efficiency.