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Application of a Functionalized K₁₋ₓNiₓNbO₃ Structure: Enhancing the Photocatalytic Activity of a CdS/K₁₋ₓNiₓNbO₃ Composite
No full textHerein we report a K₁₋ₓNiₓNbO₃ composite undergoing a phase transition from orthorhombic to rhombohedral, resulting in a Ni particle and a short Nb–O^(δ-) on the surface caused by a structural distortion. The Ni particles are dispersed on the overall surface of the structure, and the short bonded Nb–O^(δ-) sticks out to the structure interstices on the surface. The properties of the structure and surface of K₁₋ₓNiₓNbO₃ are defined by spectroscopic analysis of scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), Raman, nuclear magnetic resonance (¹H NMR), and X-ray photoelectron spectroscopy (XPS). This unique surface property enables the formation of two hybrid composites that deposit CdS on either site of the Ni/Ni–H particle or short Nb–O^(δ-), resulting in a different interface between CdS and K₁₋ₓNiₓNbO₃. The one that deposits CdS on the Ni/Ni–H particles is denoted as SCdS/K₁₋ₓNiₓNbO₃, and the other that deposits CdS on the short Nb–O^(δ-) is denoted as CdS/K_(0.9)Ni_(0.1)NbO₃. SCdS/K₁₋ₓNiₓNbO₃ exhibits a delayed kinetics for CdS photoinduced electrons compared to that of CdS/K₁₋ₓNiₓNbO₃ as decayed fluorescence at ca. 311 ps, while indicating ca. 238 ps for CdS/K₁₋ₓNiₓNbO₃. As a result, SCdS/K₁₋ₓNiₓNbO₃ exhibits a superior photocatalytic activity for H₂ production of ca. 3.1 mmol g⁻¹ h⁻¹ compared to CdS/K₁₋ₓNiₓNbO₃ with ca. 2.7 mmol g⁻¹ h⁻¹
Level Set Discrete Element Method for modeling sea ice floes
No full textUnderstanding and projecting seasonal variations in sea ice is necessary to improve global climate predictions. However, accurately capturing changes in sea ice and its interactions with ocean and atmosphere variability remains a challenge for models, notably due to its complex behavior at the floe scale. In this work, we introduce a method to capture the floe-like behavior of sea ice, named the ‘Level Set Discrete Element Method for Sea Ice’ (LS-ICE). This model can resolve individual sea ice floes with realistic shapes, and represent their physical interactions by leveraging level-set functions for detecting contact between floes. LS-ICE can also be coupled to heat and momentum forcings from the atmosphere and the ocean, and simulate associated melt and breakage processes. The discrete representation of sea ice floes reveals melt dynamics, associated with their shapes and thickness distributions, which are currently not well represented by continuum models. We illustrate the model capabilities for two different years involving the spring to summer transition in Baffin Bay, where the sea ice concentration declines from approximately 80% to 0% between the months of June and July. Satellite imagery, along with oceanographic reanalysis data based on field measurements, are used to initialize the model and validate its subsequent evolution during these months. For an appropriate set of parameters, the model can reproduce the evolution of sea ice concentration, floe size distribution, oceanic temperature and mean sea ice thickness, despite only a small number of tunable parameters. This study identifies the potential for LS-ICE to simulate the interaction between floe shape, melt and breakage, to enhance seasonal scale forecasts for sea ice floes
First steps into the cloud: Using Amazon data storage and computing with Python notebooks
No full textWith the oncoming age of big data, biologists are encountering more use cases for cloud-based computing to streamline data processing and storage. Unfortunately, cloud platforms are difficult to learn, and there are few resources for biologists to demystify them. We have developed a guide for experimental biologists to set up cloud processing on Amazon Web Services to cheaply outsource data processing and storage. Here we provide a guide for setting up a computing environment in the cloud and showcase examples of using Python and Julia programming languages. We present example calcium imaging data in the zebrafish brain and corresponding analysis using suite2p software. Tools for budget and user management are further discussed in the attached protocol. Using this guide, researchers with limited coding experience can get started with cloud-based computing or move existing coding infrastructure into the cloud environment
Small-sized, ultra-low phase noise photonic microwave oscillators at X-Ka bands
No full textSmall-sized, ultra-low phase noise photonic microwave oscillators at 10, 20, 30, and 40 GHz are demonstrated using electro-optical frequency division. At 40 GHz, a record-low, to our knowledge, phase noise of −153 dBc/Hz is achieved (10 kHz offset)
The Orbital Architecture of Qatar-6: A Fully Aligned Three-body System?
No full textThe evolutionary history of an extrasolar system is, in part, fossilized through its planets’ orbital orientations relative to the host star’s spin axis. However, spin–orbit constraints for warm Jupiters—particularly in binary star systems, which are amenable to a wide range of dynamical processes—are relatively scarce. We report a measurement of the Rossiter–McLaughlin effect, observed with the Keck/HIRES spectrograph, across the transit of Qatar-6 A b—a warm Jupiter orbiting one star within a binary system. From this measurement, we obtain a sky-projected spin–orbit angle λ = 0.°1 ± 2.°6. Combining this new constraint with the stellar rotational velocity of Qatar-6 A that we measure from TESS photometry, we derive a true obliquity ψ = 21.82_(-18.36)^(+8.86)°—consistent with near-exact alignment. We also leverage astrometric data from Gaia DR3 to show that the Qatar-6 binary star system is edge-on (i_B = 90.17_(-1.06)^(+1.07)°), such that the stellar binary and the transiting exoplanet orbit exhibit line-of-sight orbit–orbit alignment. Ultimately, we demonstrate that all current constraints for the three-body Qatar-6 system are consistent with both spin–orbit and orbit–orbit alignment. High-precision measurements of the projected stellar spin rate of the host star and the sky-plane geometry of the transit relative to the binary plane are required to conclusively verify the full 3D configuration of the system
A next-generation liquid xenon observatory for dark matter and neutrino physics
No full textThe nature of dark matter and properties of neutrinos are among the most pressing issues in contemporary particle physics. The dual-phase xenon time-projection chamber is the leading technology to cover the available parameter space for weakly interacting massive particles, while featuring extensive sensitivity to many alternative dark matter candidates. These detectors can also study neutrinos through neutrinoless double-beta decay and through a variety of astrophysical sources. A next-generation xenon-based detector will therefore be a true multi-purpose observatory to significantly advance particle physics, nuclear physics, astrophysics, solar physics, and cosmology. This review article presents the science cases for such a detector
Three-dimensional full-field velocity measurements in shock compression experiments using stereo digital image correlation
No full textShock compression plate impact experiments conventionally rely on point-wise velocimetry measurements based on laser-based interferometric techniques. This study presents an experimental methodology to measure the free surface full-field particle velocity in shock compression experiments using high-speed imaging and three-dimensional (3D) digital image correlation (DIC). The experimental setup has a temporal resolution of 100 ns with a spatial resolution varying from 90 to 200 μm/pixel. Experiments were conducted under three different plate impact configurations to measure spatially resolved free surface velocity and validate the experimental technique. First, a normal impact experiment was conducted on polycarbonate to measure the macroscopic full-field normal free surface velocity. Second, an isentropic compression experiment on Y-cut quartz–tungsten carbide assembly is performed to measure the particle velocity for experiments involving ramp compression waves. To explore the capability of the technique in multiaxial loading conditions, a pressure shear plate impact experiment was conducted to measure both the normal and transverse free surface velocities under combined normal and shear loading. The velocities measured in the experiments using digital image correlation are validated against previous data obtained from laser interferometry. Numerical simulations were also performed using established material models to compare and validate the experimental velocity profiles for these different impact configurations. The novel ability of the employed experimental setup to measure full-field free surface velocities with high spatial resolutions in shock compression experiments is demonstrated for the first time in this work
Evaluation of finite difference based asynchronous partial differential equations solver for reacting flows
No full textNext-generation exascale machines with extreme levels of parallelism will provide massive computing resources for large scale numerical simulations of complex physical systems at unprecedented parameter ranges. However, novel numerical methods, scalable algorithms and re-design of current state-of-the art numerical solvers are required for scaling to these machines with minimal overheads. One such approach for partial differential equations based solvers involves computation of spatial derivatives with possibly delayed or asynchronous data using high-order asynchrony-tolerant (AT) schemes to facilitate mitigation of communication and synchronization bottlenecks without affecting the numerical accuracy. In the present study, an effective methodology of implementing temporal discretization using a multi-stage Runge-Kutta method with AT schemes is presented. Together these schemes are used to perform asynchronous simulations of canonical reacting flow problems, demonstrated in one-dimension including auto-ignition of a premixture, premixed flame propagation and non-premixed autoignition. Simulation results show that the AT schemes incur very small numerical errors in all key quantities of interest including stiff intermediate species despite delayed data at processing element (PE) boundaries. For simulations of supersonic flows, the degraded numerical accuracy of well-known shock-resolving WENO (weighted essentially non-oscillatory) schemes when used with relaxed synchronization is also discussed. To overcome this loss of accuracy, high-order AT-WENO schemes are derived and tested on linear and non-linear equations. Finally the novel AT-WENO schemes are demonstrated in the propagation of a detonation wave with delays at PE boundaries
GOALS-JWST: Revealing the Buried Star Clusters in the Luminous Infrared Galaxy VV 114
No full textWe present the results of a James Webb Space Telescope NIRCam investigation into the young massive star cluster (YMC) population in the luminous infrared galaxy VV 114. We identify 374 compact YMC candidates with signal-to-noise ratios ≥ 3, 5, and 5 at F150W, F200W, and F356W, respectively. A direct comparison with our HST cluster catalog reveals that ∼20% of these sources are undetected at optical wavelengths. Based on yggdrasil stellar population models, we identify 17 YMC candidates in our JWST imaging alone with F150W – F200W and F200W – F356W colors suggesting they are all very young, dusty (A_V = 5–15), and massive (10^(5.8) < M_⊙ < 6.1). The discovery of these “hidden” sources, many of which are found in the “overlap” region between the two nuclei, quadruples the number of t < Myr clusters and nearly doubles the number of t < 6 Myr clusters detected in VV 114. Now extending the cluster
age distribution (dN/dτ ∝ τ^γ ) to the youngest ages, we find a slope of γ = −1.30 ± 0.39 for 10⁶ < τ(yr) < 10⁷, which is consistent with the previously determined value from 10⁷ < τ(yr) < 10^(8.5), and confirms that VV 114 has a steep age distribution slope for all massive star clusters across the entire range of cluster ages observed. Finally, the consistency between our JWST- and HST-derived age distribution slopes indicates that the balance between cluster formation and destruction has not been significantly altered in VV 114 over the last 0.5 Gyr
Gut microbial metabolism of 5-ASA diminishes its clinical efficacy in inflammatory bowel disease
No full textFor decades, variability in clinical efficacy of the widely used inflammatory bowel disease (IBD) drug 5-aminosalicylic acid (5-ASA) has been attributed, in part, to its acetylation and inactivation by gut microbes. Identification of the responsible microbes and enzyme(s), however, has proved elusive. To uncover the source of this metabolism, we developed a multi-omics workflow combining gut microbiome metagenomics, metatranscriptomics and metabolomics from the longitudinal IBDMDB cohort of 132 controls and patients with IBD. This associated 12 previously uncharacterized microbial acetyltransferases with 5-ASA inactivation, belonging to two protein superfamilies: thiolases and acyl-CoA N-acyltransferases. In vitro characterization of representatives from both families confirmed the ability of these enzymes to acetylate 5-ASA. A cross-sectional analysis within the discovery cohort and subsequent prospective validation within the independent SPARC IBD cohort (n = 208) found three of these microbial thiolases and one acyl-CoA N-acyltransferase to be epidemiologically associated with an increased risk of treatment failure among 5-ASA users. Together, these data address a longstanding challenge in IBD management, outline a method for the discovery of previously uncharacterized gut microbial activities and advance the possibility of microbiome-based personalized medicine