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Euclid: Forecast constraints on consistency tests of the ΛCDM model
No full textContext. The standard cosmological model is based on the fundamental assumptions of a spatially homogeneous and isotropic universe on large scales. An observational detection of a violation of these assumptions at any redshift would immediately indicate the presence of new physics.
Aims. We quantify the ability of the Euclid mission, together with contemporary surveys, to improve the current sensitivity of null tests of the canonical cosmological constant Λ and the cold dark matter (ΛCDM) model in the redshift range 0 z < 1.8.
Methods. We considered both currently available data and simulated Euclid and external data products based on a ΛCDM fiducial model, an evolving dark energy model assuming the Chevallier-Polarski-Linder parameterization or an inhomogeneous Lemaître-Tolman-Bondi model with a cosmological constant Λ, and carried out two separate but complementary analyses: a machine learning reconstruction of the null tests based on genetic algorithms, and a theory-agnostic parametric approach based on Taylor expansion and binning of the data, in order to avoid assumptions about any particular model.
Results. We find that in combination with external probes, Euclid can improve current constraints on null tests of the ΛCDM by approximately a factor of three when using the machine learning approach and by a further factor of two in the case of the parametric approach. However, we also find that in certain cases, the parametric approach may be biased against or missing some features of models far from ΛCDM.
Conclusions. Our analysis highlights the importance of synergies between Euclid and other surveys. These synergies are crucial for providing tighter constraints over an extended redshift range for a plethora of different consistency tests of some of the main assumptions of the current cosmological paradigm
Photochemical evolution of the 2013 California Rim Fire: synergistic impacts of reactive hydrocarbons and enhanced oxidants
No full textLarge wildfires influence regional atmospheric composition, but chemical complexity challenges model predictions of downwind impacts. Here, we elucidate key connections within gas-phase photochemistry and assess novel chemical processes via a case study of the 2013 California Rim Fire plume. Airborne in situ observations, acquired during the NASA Studies of Emissions, Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys (SEAC⁴RS) mission, illustrate the evolution of volatile organic compounds (VOCs), oxidants, and reactive nitrogen over 12 h of atmospheric aging. Measurements show rapid formation of ozone and peroxyacyl nitrates (PNs), sustained peroxide production, and prolonged enhancements in oxygenated VOCs and nitrogen oxides (NOₓ).
Observations and Lagrangian trajectories constrain a 0-D puff model that approximates plume photochemical history and provides a framework for evaluating process interactions. Simulations examine the effects of (1) previously unmeasured reactive VOCs identified in recent laboratory studies and (2) emissions and secondary production of nitrous acid (HONO). Inclusion of estimated unmeasured VOCs leads to a 250 % increase in OH reactivity and a 70 % increase in radical production via oxygenated VOC photolysis. HONO amplifies radical cycling and serves as a downwind NOₓ source, although impacts depend on how HONO is introduced. The addition of initial HONO (representing primary emissions) or particulate nitrate photolysis amplifies ozone production, while heterogeneous conversion of NO₂ suppresses ozone formation. Analysis of radical initiation rates suggests that oxygenated VOC photolysis is a major radical source, exceeding HONO photolysis when averaged over the first 2 h of aging. Ozone production chemistry transitions from VOC sensitive to NOₓ sensitive within the first hour of plume aging, with both peroxide and organic nitrate formation contributing significantly to radical termination. To simulate smoke plume chemistry accurately, models should simultaneously account for the full reactive VOC pool and all relevant oxidant sources
A high-resolution view of the filament of gas between Abell 399 and Abell 401 from the Atacama Cosmology Telescope and MUSTANG-2
No full textWe report a significant detection of the hot intergalactic medium in the filamentary bridge connecting the galaxy clusters Abell 399 and Abell 401. This result is enabled by a low-noise, high-resolution map of the thermal Sunyaev–Zeldovich signal from the Atacama Cosmology Telescope (ACT) and Planck satellite. The ACT data provide the 1.65 arcmin resolution that allows us to clearly separate the profiles of the clusters, whose centres are separated by 37 arcmin, from the gas associated with the filament. A model that fits for only the two clusters is ruled out compared to one that includes a bridge component at >5σ. Using a gas temperature determined from Suzaku X-ray data, we infer a total mass of (3.3±0.7)×10¹⁴M⊙ associated with the filament, comprising about 8 per cent of the entire Abell 399–Abell 401 system. We fit two phenomenological models to the filamentary structure; the favoured model has a width transverse to the axis joining the clusters of ∼1.9Mpc. When combined with the Suzaku data, we find a gas density of (0.88±0.24)×10⁻⁴cm⁻³, considerably lower than previously reported. We show that this can be fully explained by a geometry in which the axis joining Abell 399 and Abell 401 has a large component along the line of sight, such that the distance between the clusters is significantly greater than the 3.2Mpc projected separation on the plane of the sky. Finally, we present initial results from higher resolution (12.7 arcsec effective) imaging of the bridge with the MUSTANG-2 receiver on the Green Bank Telescope
Synthesis of Noraugustamine and Development of an Oxidative Heck/Aza-Wacker Cascade Cyclization
No full textRadical and transition metal-catalyzed cascade cyclization strategies were investigated with respect to the synthesis of the tetracyclic core of the augustamine-type Amaryllidaceae alkaloids. These studies resulted in the synthesis of noraugustamine and the development of an oxidative Heck/aza-Wacker cascade forming two rings, a C–N bond, and an all-carbon quaternary center in a single step
Sterically Invariant Carborane-Based Ligands for the Morphological and Electronic Control of Metal–Organic Chalcogenolate Assemblies
No full textHerein, we report the use of sterically invariant carborane-based chalcogenols, containing exopolyhedral B–Se or B–S bonds, as ligands for the formation of photoluminescent copper(I)-based metal–organic chalcogenolate assemblies (MOCHAs). We show that precise tuning of the carborane dipole by changing the carborane isomer from meta to ortho allows for control over the MOCHA morphology and regulation of the resulting photophysical properties. Furthermore, microcrystal electron diffraction (MicroED) has been demonstrated as a powerful tool for metal chalcogenide structure elucidation. Through the use of MicroED, one of the isolated materials is determined to consist of zero-dimensional Cu₄(Se–C₂B₁₀H₁₁)₄ clusters with an unprecedented Cu₄Se₄ geometry
Skydiving into the interface of chemistry and biology
No full textLet me extend my deepest thanks to the American Chemical Society. It is a very special honor to be included among the Priestley Medalists, many of whom are my teachers and scientific heroes. I am grateful to my students and mentors who helped me along the way.
Tonight I will take you on my journey from Boston to Pasadena. I will discuss the importance of luck, my early education, graduate school at the University of Wisconsin–Madison and Yale University, becoming a California Institute of Technology assistant professor at age 28, the impact of teaching on my research direction, embracing risk and crossing the divide between chemistry and biology, venturing outside the academic ivory tower, and national service.
My parents emigrated from Ireland. They came over in the early 1920s, before the Great Depression. Life must have been hard. Our family of six lived in Dorchester, a working-class suburb of Boston. One important value at our home was to focus on education. In the 1950s, science was admired in America. Jonas Salk had developed a safe and effective vaccine for polio, saving thousands of children from being disabled or confined to an iron lung.
In 1957, when I was 12 years old, the Soviet Union launched Sputnik, a satellite the size of a basketball that weighed about 184 lb (84 kg). The US government calculated that the Russian rockets were bigger than ours! There could be a science and engineering gap between the US and the Soviet Union. I believe this crisis was one of the best things that ever happened to America. It certainly impacted my generation. Young people were encouraged to pursue careers in science and engineering, and fellowships to do so were plentiful.
My high school experience was formative. Boston College High School was a college-preparatory school. We took 4 years of Latin and 2 years of Greek, along with German, math, chemistry, and physics—the whole deal. I carried out my first science project as a freshman and I loved it. With 4 h of homework every evening, I learned how to study and how to learn. I was prepared to succeed in college, and I feel I have been coasting downhill ever since.
I then attended Boston College as a chemistry major and have great memories doing undergraduate research in the summer before my senior year. I discovered the fun of not knowing the result of an experiment. It was like going to the racetrack! Thank you to the National Science Foundation for those undergraduate summer research fellowships
Innovation by evolution: bringing new chemistry to life
No full textNot satisfied with biology's vast catalyst repertoire, I want to create new enzyme catalysts and expand the chemistry of life. We use the most powerful biological design process, evolution, to optimize existing enzymes and invent new ones, thereby circumventing our profound ignorance of how sequence encodes function. Chemistry encoded in DNA and optimized by evolution enables efficient, sustainable routes to important fuels and chemicals. Evolution not only optimizes, it can also innovate and create entirely new enzyme catalysts. I will illustrate how whole families of new-to-nature enzymes increase the scope of molecules and materials that can be built using synthetic biology
Constraints on dark photon dark matter using data from LIGO’s and Virgo’s third observing run
No full textWe present a search for dark photon dark matter that could couple to gravitational-wave interferometers using data from Advanced LIGO and Virgo’s third observing run. To perform this analysis, we use two methods, one based on cross-correlation of the strain channels in the two nearly aligned LIGO detectors, and one that looks for excess power in the strain channels of the LIGO and Virgo detectors. The excess power method optimizes the Fourier transform coherence time as a function of frequency, to account for the expected signal width due to Doppler modulations. We do not find any evidence of dark photon dark matter with a mass between m_A ∼ 10⁻¹⁴–10⁻¹¹ eV/c², which corresponds to frequencies between 10–2000 Hz, and therefore provide upper limits on the square of the minimum coupling of dark photons to baryons, i.e., U(1)_B dark matter. For the cross-correlation method, the best median constraint on the squared coupling is ∼1.31 × 10⁻⁴⁷ at m_A ∼ 4.2 × 10⁻¹³ eV/c²; for the other analysis, the best constraint is ∼2.4 × 10⁻⁴⁷ at m_A ∼ 5.7 × 10⁻¹³ eV/c². These limits improve upon those obtained in direct dark matter detection experiments by a factor of ∼100 for m_A ∼ [2–4] × 10⁻¹³ eV/c², and are, in absolute terms, the most stringent constraint so far in a large mass range m_A ∼ 2 × 10⁻¹³–8 × 10⁻¹² eV/c²
Part-per-trillion trace selective gas detection using frequency locked whispering gallery mode microtoroids
No full textRapid detection of toxic and hazardous gases at trace concentrations plays a vital role in industrial, battlefield, and laboratory scenarios. Of interest are both sensitive as well as highly selective sensors. Whispering gallery mode (WGM) microresonator-based biochemical sensors are among the most sensitive sensors in existence due to their long photon confinement times. One main concern with these devices, however, is their selectivity towards specific classes of target analytes. Here, we employ frequency locked whispering gallery mode microtoroid optical resonators covalently modified with various polymer coatings to selectively detect the chemical warfare agent surrogate diisopropyl methylphosphonate (DIMP) as well as the toxic industrial chemicals formaldehyde and ammonia at parts-per-trillion concentrations. This is 1-2 orders of magnitude better than previously reported, depending on the target, except for pristine graphene and pristine carbon nanotube sensors, which demonstrate similar detection levels but in vacuum and without selectivity. Selective polymer coatings include polyethylene glycol (PEG) for DIMP sensing, accessed by the modification of commercially available materials, and 3-(triethoxysilyl)propyl-terminated polyvinyl acetate (PVAc) for ammonia sensing. Notably, we developed an efficient one-pot procedure to access 3-(triethoxysilyl)propyl-terminated PVAc that utilizes cobalt-mediated living radical polymerization and a nitroxyl polymer-terminating agent. Alkaline hydrolysis of PVAc coatings to form polyvinyl alcohol (PVA) coatings directly bound to the microtoroid proved to be reliable and reproducible, leading to WGM sensors capable of the rapid and selective detection of formaldehyde vapors. The selectivity of these three polymer coatings as sensing media was predicted, in part, based on their functional group content and known reactivity patterns with the target analytes. Furthermore, we demonstrate that microtoroids coated with a mixture of polymers can serve as an all-in-one sensor that can detect multiple agents. We anticipate that our results will facilitate rapid early detection of chemical agents, as well as their surrogates and precursors
QUBIC VIII: Optical design and performance
No full textThe Q and U Bolometric Interferometer for Cosmology (QUBIC) is a ground-based experiment that aims to detect B-mode polarization anisotropies [1] in the CMB at angular scales around the ℓ ≃100 recombination peak. Systematic errors make ground-based observations of B modes at millimetre wavelengths very challenging and QUBIC mitigates these problems in a somewhat complementary way to other existing or planned experiments using the novel technique of bolometric interferometry. This technique takes advantage of the sensitivity of an imager and the systematic error control of an interferometer. A cold reflective optical combiner superimposes the re-emitted beams from 400 aperture feedhorns on two focal planes. A shielding system composed of a fixed groundshield, and a forebaffle that moves with the instrument, limits the impact of local contaminants. The modelling, design, manufacturing and preliminary measurements of the optical components are described in this paper