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At least 721 records · Page 40

The Hubble PanCET Program: A Metal-rich Atmosphere for the Inflated Hot Jupiter HAT-P-41b

We present a comprehensive analysis of the 0.3–5 μm transit spectrum for the inflated hot Jupiter HAT-P-41b. The planet was observed in transit with Hubble STIS and WFC3 as part of the Hubble Panchromatic Comparative Exoplanet Treasury (PanCET) program, and we combine those data with warm Spitzer transit observations. We extract transit depths from each of the data sets, presenting the STIS transit spectrum (0.29–0.93 μm) for the first time. We retrieve the transit spectrum both with a free-chemistry retrieval suite (AURA) and a complementary chemical equilibrium retrieval suite (PLATON) to constrain the atmospheric properties at the day–night terminator. Both methods provide an excellent fit to the observed spectrum. Both AURA and PLATON retrieve a metal-rich atmosphere for almost all model assumptions (most likely O/H ratio of log{sub 10}Z/Z{sub ⊙}=1.46{sub −0.68}{sup +0.53} and log{sub 10}Z/Z{sub ⊙}=2.33{sub −0.25}{sup +0.23}, respectively); this is driven by a 4.9σ detection of H{sub 2}O as well as evidence of gas absorption in the optical (>2.7σ detection) due to Na, AlO, and/or VO/TiO, though no individual species is strongly detected. Both retrievals determine the transit spectrum to be consistent with a clear atmosphere, with no evidence of haze or high-altitude clouds. Interior modeling constraints on the maximum atmospheric metallicity (log{sub 10}Z/Z{sub ⊙}<1.7) favor the AURA results. The inferred elemental oxygen abundance suggests that HAT-P-41b has one of the most metal-rich atmospheres of any hot Jupiters known to date. Overall, the inferred high metallicity and high inflation make HAT-P-41b an interesting test case for planet formation theories.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

ACCESS: An Optical Transmission Spectrum of the High-gravity Hot Jupiter HAT-P-23b

We present a new ground-based visible transmission spectrum of the high-gravity, hot Jupiter HAT-P-23b, obtained as part of the ACCESS project. We derive the spectrum from five transits observed between 2016 and 2018, with combined wavelength coverage between 5200 Å and 9269 Å in 200 Å bins, and with a median precision of 247 ppm per bin. HAT-P-23b’s relatively high surface gravity (g ≈ 30 m s{sup −2}), combined with updated stellar and planetary parameters from Gaia DR2, gives a five-scale-height signal of 384 ppm for a hydrogen-dominated atmosphere. Bayesian models favor a clear atmosphere for the planet with the tentative presence of TiO, after simultaneously modeling stellar contamination, using spots parameter constraints from photometry. If confirmed, HAT-P-23b would be the first example of a high-gravity gas giant with a clear atmosphere observed in transmission at optical/near-IR wavelengths; therefore, we recommend expanding observations to the UV and IR to confirm our results and further characterize this planet. This result demonstrates how combining transmission spectroscopy of exoplanet atmospheres with long-term photometric monitoring of the host stars can help disentangle the exoplanet and stellar activity signals.

47 OTHER INSTRUMENTATION↗

Strontium-84 Enrichments in Presolar Grains Provide First Evidence of p -process Nucleosynthesis in Core-collapse Supernovae

This study reports detection of rare p-process isotopes within presolar grains. Presolar grains are relic dust grains from dying stars. These microscopic dust particles are found in primitive solar system materials. Their distinct isotopic compositions record the nucleosynthetic processes in their parent stars and the Galactic chemical environment in which these stars formed. We studied presolar graphite grains of high-density type from the Murchison meteorite and found five grains with subgrains that show enrichments in 84 Sr compared to the solar abundance. 84 Sr is the neutron-deficient isotope of strontium that can be produced in the deep oxygen-rich interior of high-mass stars that end their lives as core-collapse supernovae. The observed 84 Sr excesses cannot be produced in low-mass asymptotic giant branch stars, the source of most high-density presolar graphites found in meteorites. High-density graphites with embedded 84 Sr excesses are, instead, compatible with a core-collapse supernovae origin. The graphite subgrains condensed from carbon-rich materials in the outer layers of core-collapse supernovae, where 84 Sr was destroyed by neutron captures during hydrostatic evolution of the stars and their final explosion. Based on current theoretical stellar models, a few percent of contribution from the inner regions of core-collapse supernovae, which are enriched in p-process nuclides, to the outer carbon-rich regions is the most likely explanation for the observed enrichment of 84 Sr in the subgrains of the high-density graphites. In this study, we present the first observational evidence that core-collapse supernovae produce and eject isotopes made by the p-process.

Astronomy and AstroPhysics↗

Developing capacitated p-median location-allocation model in the spopt library to allow UCL student teacher placements using public transport

Location-allocation is a key tool within the GIS and network analysis toolbox. In this paper we discuss the real world application of a location-allocation case study (approx 800 students, 500 schools) from UCL using public transport. The use of public transportation is key for this case study, as many location-allocation approaches only make use of drive-time or walking-time distances, but the location of UCL in Greater London, UK makes the inclusion of public transport vital for this case study. The location-allocation is implemented as a capacitated p-median location-allocation model, using the spopt library, part of the Python Spatial Analysis Library (PySAL). The capacitated variation of the p-median location-allocation problem is a new addition to the spopt library, which this work will present. The results from the initial version of the capacitated p-median location-allocation problem has shown a marked improvement on public transport travel time, with public transport travel time reduced by 891 minutes overall for an initial sample of 93 students (9.58 minutes per student). Results will be presented below and plans for further improvement shared.

Bearman, Nick↗

P-coumaroyl-CoA:monolignol transferases

The invention is directed to p-coumaroyl-CoA:monolignol transferase enzymes, nucleic acids encoding p-coumaroyl-CoA:monolignol transferase enzymes, and inhibitory nucleic acids adapted to inhibit the expression and/or translation of p-coumaroyl-CoA:monolignol transferase RNA; expression cassettes, plant cells, and plants that have or encode such nucleic acids and enzymes; and methods of making and using such nucleic acids, enzymes, expression cassettes, cells, and plants.

Ralph, John↗

Generation and enhancement of surface acoustic waves on a highly doped p-type III-V semiconductor substrate

A device employing the generation and enhancement of surface acoustic waves on a highly doped p-type III-V semiconductor substrate (e.g., GaAs, GaSb, InAs, or InGaAs). The device includes two SiO 2 /ZnO islands, each including a SiO 2 buffer layer deposited on the doped p-type III-V semiconductor substrate and a ZnO layer deposited on the SiO 2 buffer layer. An input interdigital transducers (IDT) and an output IDT are each patterned on one of the SiO 2 /ZnO islands. The IDTs generates surface acoustic waves along an exposed surface of the highly doped p-type III-V semiconductor substrate. The surface acoustic waves improve the photoelectric and photovoltaic properties of the device. The device is manufactured using a disclosed technique for propagating strong surface acoustic waves on weak piezoelectric materials. Also disclosed is a photodetector developed using that technique.

Dong, Boqun↗

P-coumaroyl-CoA:monolignol transferase

The invention relates to nucleic acids encoding a p-coumaroyl-CoA:monolignol transferase and to inhibitory nucleic acids adapted to inhibit the expression and/or translation of a p-coumaroyl-CoA:monolignol transferase RNA. Inhibition of p-coumaroyl-CoA:monolignol transferase in plants improves the incorporation of monolignol ferulates into the lignin of plants, giving rise to plant biomass that is more easily processed into useful products such as paper and biofuels.

Wilkerson, Curtis↗

P-coumaroyl-CoA:monolignol transferases

The invention is directed to p-coumaroyl-CoA:monolignol transferase enzymes, nucleic acids encoding p-coumaroyl-CoA:monolignol transferase enzymes, and inhibitory nucleic acids adapted to inhibit the expression and/or translation of p-coumaroyl-CoA:monolignol transferase RNA; expression cassettes, plant cells, and plants that have or encode such nucleic acids and enzymes; and methods of making and using such nucleic acids, enzymes, expression cassettes, cells, and plants.

Ralph, John↗

A position and pulse shape discriminant p -terphenyl detector module

We present the development of a neutron detector array module made with para-terphenyl, a bright, fast, n/γ discriminating crystalline organic scintillator. The module is comprised of 2 cm × 2 cm × 2 cm p-terphenyl crystals that have been optically coupled together to create a pseudo-bar module. While only relying on two photo detectors, the module is capable of distinguishing interactions between up to eight crystals. Furthermore, the module retains the p-terphenyl’s pulse shape discrimination (PSD) capability. Together this makes the pseudo-bar module a promising position-sensitive neutron detector. Here we present characteristics of the pseudo-bar module - its timing resolution as well as its pulse shape and position discrimination capabilities, and briefly discuss future plans for utilizing an array of pseudo-bar modules in a useful neutron detector system.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

Nitrogen p-type doping in polycrystalline zinc selenide telluride films

Nitrogen-doped zinc selenide telluride (N:ZnSe x Te 1−x ) is of interest because it is one of the widest-gap II–VI semiconductors that can still be doped p-type with reasonably high hole concentrations. We sputter deposit N:ZnSe x Te 1−x films, varying Se/(Se + Te), or x, from 0 to 0.7, N 2 flow rate from 0.25 to 0.75 sccm, and substrate temperature from 250 to 370 °C. Increasing x from 0 to 0.39 at the optimal temperature of 370 °C and N 2 flow rate of 0.5 sccm leads to 1.3 atomic % nitrogen incorporation and wurtzite phase stabilization. Such doping and alloying increases hole concentration from 3 × 10 18 cm −3 to 3 × 10 19 cm −3 , although mobility drops from 0.4 to 0.02 cm 2 V −1 s −1 . Our sputtered N:ZnSe 0.38 Te 0.62 has an absorption onset 0.1 eV greater than the ZnTe value of 1.87 eV. Increasing x from 0 to 0.51 enhances transmittance by moving absorption onset from 1.87 to 2.11 eV with diminished band gap bowing likely due to disorder, and increases the work function from 5.12 to 5.42 eV. This combination of tunable properties makes sputtered N:ZnSe x Te 1−x desirable for transparent p-type contacts in polycrystalline Cd(Se,Te) optoelectronic devices.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Cross-section measurement of the 82 Kr ($p,γ$) 83 Rb reaction in inverse kinematics

The total cross section of the 82 Kr(p,γ) 83 Rb reaction was measured for the first time at effective center-of-mass energies between 2.4 and 3.0 MeV, within the relevant Gamow window for the astrophysical γ process. The experiment took place at the National Superconducting Cyclotron Laboratory at Michigan State University using the ReA facility. A 82 Kr beam was directed onto a hydrogen gas cell located at the center of the Summing NaI(Tl) (SuN) detector. Here, the obtained spectra were analyzed using the γ-summing technique and the extracted cross section was compared to standard statistical model calculations using the non-smoker and talys codes. The comparison indicates that standard statistical model calculations tend to overproduce the cross section of the 82 Kr(p,γ) 83 Rb reaction relative to the experimentally measured values. Furthermore, the experimental data were used to provide additional constraints on the nuclear level density and the γ-ray strength function used in the statistical model calculations.

59 ≤ A ≤ 89↗

First Direct Measurement of Mg (α,p) 25 Al and Implications for X-Ray Burst Model-Observation Comparisons

Type-I x-ray bursts can reveal the properties of an accreting neutron star system when compared with astrophysics model calculations. However, model results are sensitive to a handful of uncertain nuclear reaction rates, such as 22 Mg(α , p). We report the first direct measurement of 22 Mg(α , p), performed with the Active Target Time Projection Chamber. The corresponding astrophysical reaction rate is orders of magnitude larger than determined from a previous indirect measurement in a broad temperature range. Overall, our new measurement suggests a less-compact neutron star in the source GS1826-24.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

Beam Energy Dependence of Triton Production and Yield Ratio $N_t \times N_p / N^2_d$ in Au+Au Collisions at RHIC

We report the triton (t) production in midrapidity (|y| < 0.5) Au + Au collisions at $\sqrt{s_{NN}} = 7.7-200$ GeV measured by the STAR experiment from the first phase of the beam energy scan at the Relativistic Heavy Ion Collider. The nuclear compound yield ratio ($N_t \times N_p / N^2_d$), which is predicted to be sensitive to the fluctuation of local neutron density, is observed to decrease monotonically with increasing charged-particle multiplicity ($dN_{ch}/dη$) and follows a scaling behavior. The $dN_{ch}/dη$ dependence of the yield ratio is compared to calculations from coalescence and thermal models. Enhancements in the yield ratios relative to the coalescence baseline are observed in the 0%-10% most central collisions at 19.6 and 27 GeV, with a significance of 2.3σ and 3.4σ, respectively, giving a combined significance of 4.1σ. The enhancements are not observed in peripheral collisions or model calculations without critical fluctuation, and decreases with a smaller $p_T$ acceptance. The physics implications of these results on the QCD phase structure and the production mechanism of light nuclei in heavy-ion collisions are discussed.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

Demonstration of >6.0-kV Breakdown Voltage in Large Area Vertical GaN p-n Diodes With Step-Etched Junction Termination Extensions

Vertical gallium nitride (GaN) p-n diodes have garnered significant interest for use in power electronics where high-voltage blocking and high-power efficiency are of concern. In this article, we detail the growth and fabrication methods used to develop a large area (1 mm 2 ) vertical GaN p-n diode capable of a 6.0-kV breakdown. We also demonstrate a large area diode with a forward pulsed current of 3.5 A, an 8.3-mΩ$\cdot$cm 2 differential specific ON-resistance, and a 5.3-kV reverse breakdown. In addition, we report on a smaller area diode (0.063 mm 2 ) that is capable of 6.4-kV breakdown with a differential specific ON-resistance of 10.2 mΩ$\cdot$cm 2 , when accounting for current spreading through the drift region at a 45° angle. Finally, the demonstration of avalanche breakdown is shown for a 0.063-mm 2 diode with a room temperature breakdown of 5.6 kV. In this work, these results were achieved via epitaxial growth of a 50-μm drift region with a very low carrier concentration of <1×10 15 cm –3 and a carefully designed four-zone junction termination extension.

42 ENGINEERING↗

Materials Data on P(HO)3 by Materials Project

H3PO3 crystallizes in the orthorhombic Pna2_1 space group. The structure is one-dimensional and consists of four H3PO3 ribbons oriented in the (1, 0, 0) and (0, 1, 0) directions. In two of the H3PO3 ribbons, P5+ is bonded in a trigonal non-coplanar geometry to three O2- atoms. There are a spread of P–O bond distances ranging from 1.62–1.67 Å. There are three inequivalent H+0.33+ sites. In the first H+0.33+ site, H+0.33+ is bonded in a distorted single-bond geometry to two O2- atoms. There is one shorter (1.00 Å) and one longer (1.69 Å) H–O bond length. In the second H+0.33+ site, H+0.33+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 1.00 Å. In the third H+0.33+ site, H+0.33+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.98 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 120 degrees geometry to one P5+ and one H+0.33+ atom. In the second O2- site, O2- is bonded in a 2-coordinate geometry to one P5+ and two H+0.33+ atoms. In the third O2- site, O2- is bonded in a water-like geometry to one P5+ and one H+0.33+ atom. In two of the H3PO3 ribbons, P5+ is bonded in a trigonal non-coplanar geometry to three O2- atoms. There are a spread of P–O bond distances ranging from 1.62–1.67 Å. There are three inequivalent H+0.33+ sites. In the first H+0.33+ site, H+0.33+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.99 Å. In the second H+0.33+ site, H+0.33+ is bonded in a distorted linear geometry to two O2- atoms. There is one shorter (1.01 Å) and one longer (1.64 Å) H–O bond length. In the third H+0.33+ site, H+0.33+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.99 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted water-like geometry to one P5+ and one H+0.33+ atom. In the second O2- site, O2- is bonded in a bent 120 degrees geometry to one P5+ and one H+0.33+ atom. In the third O2- site, O2- is bonded in a distorted trigonal planar geometry to one P5+ and two H+0.33+ atoms.

36 MATERIALS SCIENCE↗

Materials Data on P(W3O10)2 by Materials Project

P(W3O10)2 crystallizes in the orthorhombic P2_12_12_1 space group. The structure is three-dimensional. there are six inequivalent W+5.83+ sites. In the first W+5.83+ site, W+5.83+ is bonded to six O2- atoms to form corner-sharing WO6 octahedra. The corner-sharing octahedra tilt angles range from 2–19°. There are a spread of W–O bond distances ranging from 1.87–2.00 Å. In the second W+5.83+ site, W+5.83+ is bonded to six O2- atoms to form WO6 octahedra that share corners with five WO6 octahedra and a cornercorner with one PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 5–18°. There are a spread of W–O bond distances ranging from 1.85–2.05 Å. In the third W+5.83+ site, W+5.83+ is bonded to six O2- atoms to form corner-sharing WO6 octahedra. The corner-sharing octahedra tilt angles range from 1–17°. There are a spread of W–O bond distances ranging from 1.92–1.96 Å. In the fourth W+5.83+ site, W+5.83+ is bonded to six O2- atoms to form WO6 octahedra that share corners with three WO6 octahedra and corners with three equivalent PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 2–18°. There are a spread of W–O bond distances ranging from 1.85–2.06 Å. In the fifth W+5.83+ site, W+5.83+ is bonded to six O2- atoms to form corner-sharing WO6 octahedra. The corner-sharing octahedra tilt angles range from 1–19°. There are a spread of W–O bond distances ranging from 1.91–1.98 Å. In the sixth W+5.83+ site, W+5.83+ is bonded to six O2- atoms to form corner-sharing WO6 octahedra. The corner-sharing octahedra tilt angles range from 1–19°. There are a spread of W–O bond distances ranging from 1.89–2.02 Å. P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with four WO6 octahedra. The corner-sharing octahedra tilt angles range from 10–26°. All P–O bond lengths are 1.54 Å. There are twenty inequivalent O2- sites. In the first O2- site, O2- is bonded in a linear geometry to two W+5.83+ atoms. In the second O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one W+5.83+ and one P5+ atom. In the third O2- site, O2- is bonded in a distorted bent 150 degrees geometry to two W+5.83+ atoms. In the fourth O2- site, O2- is bonded in a bent 150 degrees geometry to two W+5.83+ atoms. In the fifth O2- site, O2- is bonded in a distorted linear geometry to one W+5.83+ and one P5+ atom. In the sixth O2- site, O2- is bonded in a bent 150 degrees geometry to one W+5.83+ and one P5+ atom. In the seventh O2- site, O2- is bonded in a linear geometry to two W+5.83+ atoms. In the eighth O2- site, O2- is bonded in a distorted linear geometry to one W+5.83+ and one P5+ atom. In the ninth O2- site, O2- is bonded in a linear geometry to two W+5.83+ atoms. In the tenth O2- site, O2- is bonded in a linear geometry to two W+5.83+ atoms. In the eleventh O2- site, O2- is bonded in a linear geometry to two equivalent W+5.83+ atoms. In the twelfth O2- site, O2- is bonded in a linear geometry to two W+5.83+ atoms. In the thirteenth O2- site, O2- is bonded in a linear geometry to two W+5.83+ atoms. In the fourteenth O2- site, O2- is bonded in a linear geometry to two W+5.83+ atoms. In the fifteenth O2- site, O2- is bonded in a bent 150 degrees geometry to two W+5.83+ atoms. In the sixteenth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to two W+5.83+ atoms. In the seventeenth O2- site, O2- is bonded in a linear geometry to two W+5.83+ atoms. In the eighteenth O2- site, O2- is bonded in a linear geometry to two W+5.83+ atoms. In the nineteenth O2- site, O2- is bonded in a linear geometry to two W+5.83+ atoms. In the twentieth O2- site, O2- is bonded in a linear geometry to two W+5.83+ atoms.

36 MATERIALS SCIENCE↗

A Molten Salt Electrochemical Process for the Preparation of Cost-Effective p-Block (Coating) Materials

Solar energy applications rely heavily on p-block elements and transition metals. Silicon is, by far, the most commonly used material in photovoltaic cells and accounts for about 85% of modules sold presently. Of late, thin film photovoltaic cells have gained momentum because of their higher efficiencies. Most of these thin film devices are made out of just five elements, namely, cadmium, tellurium, selenium, indium, gallium and copper. The present manuscript describes an elegant and inexpensive molten salt-based electrolytic process for fabricating a tellurium-coated metallic substrate. A three-electrode set up was employed to coat iridium with tellurium from a molten bath containing lithium chloride, lithium oxide and tellurium tetrachloride (LiCl-Li 2 O-TeCl 4 ) at 650 °C for a duration ranging from 30 to 120 min under a galvanostatic mode. The tellurium coating was observed to be thick, uniform, smooth and homogeneous. Additionally, the deposited tellurium did not chemically react with the iridium substrate to form intermetallic compounds, which is a good feature from the standpoint of the device’s performance characteristics. The present process, being generic in nature, shows the potential for the manufacture of both the coated substates and high-purity elements not just for tellurium but also for other p-block elements.

36 MATERIALS SCIENCE↗

Search for baryon and lepton number violating decays D → p ℓ

We search for the baryon and lepton number violating charm decays, D → p ℓ , where D is either a D 0 or a D ¯ 0 and ℓ is a muon or an electron, using a data sample of 921 fb − 1 collected by the Belle detector at the KEKB asymmetric energy e + e − collider. In the absence of significant signals, we set upper limits on the branching fractions in the range ( 5 – 8 ) × 10 − 7 at a 90% confidence level, depending on the decay mode. Published by the American Physical Society 2024

Astronomy & Astrophysics↗