We present precision 4.5 Spitzer transit photometry of eight planet candidates discovered by the K2 mission: K2-52 b, K2-53 b, EPIC 205084841.01, K2-289 b, K2-174 b, K2-87 b, K2-90 b, and K2-124 b. ...The sample includes four sub-Neptunes and two sub-Saturns, with radii between 2.6 and 18 and equilibrium temperatures between 440 and 2000 K. In this paper we identify several targets of potential interest for future characterization studies, demonstrate the utility of transit follow-up observations for planet validation and ephemeris refinement, and present new imaging and spectroscopy data. Our simultaneous analysis of the K2 and Spitzer light curves yields improved estimates of the planet radii and multiwavelength information that helps validate their planetary nature, including the previously unvalidated candidate EPIC 205686202.01 (K2-289 b). Our Spitzer observations yield an order-of-magnitude increase in ephemeris precision, thus paving the way for efficient future study of these interesting systems by reducing the typical transit timing uncertainty in mid-2021 from several hours to a dozen or so minutes. K2-53 b, K2-289 b, K2-174 b, K2-87 b, and K2-90 b are promising radial velocity (RV) targets given the performance of spectrographs available today or in development, and the M3V star K2-124 hosts a temperate sub-Neptune that is potentially a good target for both RV and atmospheric characterization studies.
The CO oxidation on different platinum model catalysts, in particular differently sized Pt particles on vertically aligned TiO2 nanotubes (d=80, l=200 nm) was investigated by near‐ambient‐pressure ...X‐ray photoelectron spectroscopy and simultaneous online gas analysis. The results are compared to the behavior on a TiO2(1 1 0) rutile crystal with a similar Pt coverage and a Pt(1 1 1) single crystal. Temperature‐programmed reaction experiments at total pressures of 10−3 to 1.0 mbar, and a CO/O2 ratio of 1:4 were performed to evaluate the reactivity of the samples. The onset temperature of the reaction on the Pt/TiO2 nanotube samples was found to be lower than on Pt(1 1 1) and Pt/TiO2(1 1 0) and to decrease with decreasing particle size. For all particle samples, a steep increase in reaction rate at a defined temperature was observed, and at high temperatures the reaction became mass transfer‐limited in all cases. Isothermal measurements showed that no CO is adsorbed on the particles when CO oxidation has a high activity and metallic platinum is the active catalyst. Ageing of the TiO2‐supported samples is observed resulting in changes of the reaction onset and CO conversion.
Tubular Underground: The CO oxidation on differently sized Pt particles sputtered on vertically aligned TiO2 nanotubes is investigated. For all particle samples, a steep increase in reaction rate at a defined temperature is observed. At high temperatures the reaction becomes mass‐transfer limited.
The James Webb Space Telescope (JWST) will likely revolutionize transiting exoplanet atmospheric science, due to a combination of its capability for continuous, long duration observations and its ...larger collecting area, spectral coverage, and spectral resolution compared to existing space-based facilities. However, it is unclear precisely how well JWST will perform and which of its myriad instruments and observing modes will be best suited for transiting exoplanet studies. In this article, we describe a prefatory JWST Early Release Science (ERS) Cycle 1 program that focuses on testing specific observing modes to quickly give the community the data and experience it needs to plan more efficient and successful transiting exoplanet characterization programs in later cycles. We propose a multi-pronged approach wherein one aspect of the program focuses on observing transits of a single target with all of the recommended observing modes to identify and understand potential systematics, compare transmission spectra at overlapping and neighboring wavelength regions, confirm throughputs, and determine overall performances. In our search for transiting exoplanets that are well suited to achieving these goals, we identify 12 objects (dubbed "community targets") that meet our defined criteria. Currently, the most favorable target is WASP-62b because of its large predicted signal size, relatively bright host star, and location in JWST's continuous viewing zone. Since most of the community targets do not have well-characterized atmospheres, we recommend initiating preparatory observing programs to determine the presence of obscuring clouds/hazes within their atmospheres. Measurable spectroscopic features are needed to establish the optimal resolution and wavelength regions for exoplanet characterization. Other initiatives from our proposed ERS program include testing the instrument brightness limits and performing phase-curve observations. The latter are a unique challenge compared to transit observations because of their significantly longer durations. Using only a single mode, we propose to observe a full-orbit phase curve of one of the previously characterized, short-orbital-period planets to evaluate the facility-level aspects of long, uninterrupted time-series observations.
Histiocytic sarcoma (HS) is associated with a poor prognosis owing to the presence of metastasis at the time of diagnosis in most dogs. Improved outcome has been reported in several dogs with ...localized HS following local therapy, however, distant metastasis occurs in 70–91% of dogs suggesting that adjuvant systemic therapy is necessary. The purpose of this retrospective study was to describe clinical characteristics and outcome in dogs with localized HS treated with aggressive local therapy plus adjuvant CCNU chemotherapy. Data from 16 dogs were evaluated. The median disease‐free interval was 243 days. Two dogs had local recurrence and eight dogs developed metastatic disease with a median time to relapse of 201 days in these 10 dogs. The median survival time for all 16 dogs was 568 days. These results support the recommendation for aggressive local therapy combined with adjuvant CCNU chemotherapy in dogs with localized HS.
Abstract
The CO oxidation on different platinum model catalysts, in particular differently sized Pt particles on vertically aligned TiO
2
nanotubes (
d
=80,
l
=200 nm) was investigated by ...near‐ambient‐pressure X‐ray photoelectron spectroscopy and simultaneous online gas analysis. The results are compared to the behavior on a TiO
2
(1 1 0) rutile crystal with a similar Pt coverage and a Pt(1 1 1) single crystal. Temperature‐programmed reaction experiments at total pressures of 10
−3
to 1.0 mbar, and a CO/O
2
ratio of 1:4 were performed to evaluate the reactivity of the samples. The onset temperature of the reaction on the Pt/TiO
2
nanotube samples was found to be lower than on Pt(1 1 1) and Pt/TiO
2
(1 1 0) and to decrease with decreasing particle size. For all particle samples, a steep increase in reaction rate at a defined temperature was observed, and at high temperatures the reaction became mass transfer‐limited in all cases. Isothermal measurements showed that no CO is adsorbed on the particles when CO oxidation has a high activity and metallic platinum is the active catalyst. Ageing of the TiO
2
‐supported samples is observed resulting in changes of the reaction onset and CO conversion.
Phthalocyanine–Perylenediimide Cart Wheels Fernández-Ariza, Javier; Krick Calderón, Rafael M; Rodríguez-Morgade, M. Salomé ...
Journal of the American Chemical Society,
10/2016, Letnik:
138, Številka:
39
Journal Article
Recenzirano
Odprti dostop
The electronic features of Zn(II) and Ru(II) phthalocyanines (Pcs) have been modulated by direct peripheral attachment of up to eight ferrocenes. The presence of peripheral ferrocenes noticeably ...impacts the electronic properties of the corresponding ZnPc and RuPc complexes 7, 12 and 9, 15, respectivelya notion that is supported by optical spectroscopy with bathochromic shifts of up to 8–10 nm per ferrocene unit. Cyclic voltammetry and optical spectroscopy reveal long-distance (10–11 bonds) electronic interaction between ferrocene units. The ZnPc and RuPc complexes have been integrated into a series of orthogonal, supramolecular bis(phthalocyanine)–perylenediimide electron donor–acceptor conjugates, 2a,b and 3a,b. In these cart-wheel-shaped arrays, coordination of ditopic perylenediimide 16, containing two pyridyl substituents at its imido positions, enabled selective interactions with the metal centers of phthalocyanines 7, 12, 9, and 15. The presence of ferrocenes in, for example, Zn complexes 2a and 3a triggers a fast energy transfer from the excited-state PDI to ZnPc. In the RuPc-PDI conjugates, substitution with ferrocenes produces a slight acceleration of the charge separation upon photoexcitation of the PDI chromophore. However, charge recombination is accelerated by 2 orders of magnitude in ferrocene-containing conjugates when compared to that in the analogous tert-butyl-substituted array 1b.
Four new subphthalocyanine-based capsules have been synthesized and characterized. These supramolecular systems have been successfully employed for the encapsulation of fullerenes and probed by a ...wide range of characterization methods, including NMR, UV–vis and fluorescence spectroscopy, electrospray ionization mass spectrometry, and electrochemistry. Furthermore, the binding constants of the host guest complexes were estimated. Finally, the photophysical properties revealed that the subphthalocyanines undergo a transduction of singlet excited-state energy to the fullerene inside the cavity upon photoexcitation.
The present study systematically investigated the mechanical properties of wire-based (wire and arc additive manufacturing, known as WAAM) deposition of steel metals, both stainless steel 304 and ...mild steel ER70S. Graded material properties of stainless steel 304 were observed for wear and hardness in the direction of deposition and in Z height, due to variations in local thermal histories of the metal. Wear rates decreased significantly (p=5.6×10−12 by one-way ANOVA) along the length of the deposited material, from K=2.62x10−5mm3/Nm (+/− 2.32x10−6mm3/Nm), to K=0.63mm3x10−5mm3/Nm (+/−3.08x10-6mm3/Nm), whereas microhardness values increased significantly (p∼0 by one-way ANOVA) along the same path from μ=202.3 HV and σ=5.82 HV to 210.9 HV and σ=5.91 HV. The yield and ultimate strength, however, were not found to be statistically significantly different (p=0.55) along the direction of deposition for SS304. During wear testing, a grain refinement was observed directly beneath the wear scar in these materials in a focused ion beam channel observed under scanning electron microscopy. Additionally, no significant difference in yield strength was observed in printed mild steel (ER70S) between vertical and horizontal specimens. The observed graded mechanical properties in stainless steel 304 allow the opportunity for varying the processing conditions to design parts with locally optimized or functionally graded mechanical properties.
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