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Beyond Beer's Law: Why the Index of Refraction Depends (Almost) Linearly on Concentration
Beer's empiric law states that absorbance is linearly proportional to the concentration. Based on electromagnetic theory, an approximately linear dependence can only be confirmed for comparably weak oscillators. For stronger oscillators the proportionality constant, the molar attenuation coefficient, is modulated by the inverse index of refraction, which is itself a function of concentration. For comparably weak oscillators, the index of refraction function depends, like absorbance, linearly on concentration. For stronger oscillators, this linearity is lost, except at wavenumbers considerably lower than the oscillator position. In these transparency regions, linearity between the change of the index of refraction and concentration is preserved to a high degree. This can be shown with help of the KramersâKronig relations which connect the integrated absorbance to the index of refraction change at lower wavenumbers than the corresponding band. This finding builds the foundation not only for refractive index sensing, but also for new interferometric approaches in IR spectroscopy, which allow measuring the complex index of refraction function. © 2020 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA
Ultra-sensitive silicon nitride waveguide-enhanced Raman spectroscopy for aqueous solutions of organic compounds
We demonstrate a waveguide-enhanced Raman sensor functionalized with mesoporous silica coating for organic compounds in aqueous solutions. The detection limit of cyclohexanone in water is improved by at least 100 times compared to bare waveguides. (C) 2020 The Author(s
Shuffled ATG8 interacting motifs form an ancestral bridge between UFMylation and autophagy
UFMylation involves the covalent modification of substrate proteins with UFM1 (Ubiquitinâfold modifier 1) and is important for maintaining ER homeostasis. Stalled translation triggers the UFMylation of ERâbound ribosomes and activates C53âmediated autophagy to clear toxic polypeptides. C53 contains noncanonical shuffled ATG8âinteracting motifs (sAIMs) that are essential for ATG8 interaction and autophagy initiation. However, the mechanistic basis of sAIMâmediated ATG8 interaction remains unknown. Here, we show that C53 and sAIMs are conserved across eukaryotes but secondarily lost in fungi and various algal lineages. Biochemical assays showed that the unicellular alga Chlamydomonas reinhardtii has a functional UFMylation pathway, refuting the assumption that UFMylation is linked to multicellularity. Comparative structural analyses revealed that both UFM1 and ATG8 bind sAIMs in C53, but in a distinct way. Conversion of sAIMs into canonical AIMs impaired binding of C53 to UFM1, while strengthening ATG8 binding. Increased ATG8 binding led to the autoactivation of the C53 pathway and sensitization of Arabidopsis thaliana to ER stress. Altogether, our findings reveal an ancestral role of sAIMs in UFMylationâdependent fineâtuning of C53âmediated autophagy activation
NGTS-21b: An Inflated Super-Jupiter Orbiting a Metal-poor K dwarf
We report the discovery of NGTS-21b, a massive hot Jupiter orbiting a
low-mass star as part of the Next Generation Transit Survey (NGTS). The planet
has a mass and radius of M, and
R, and an orbital period of 1.543 days. The host is a K3V (, K) metal-poor (, dex) dwarf
star with a mass and radius of , M,and , R. Its age and rotation period of , Gyr
and , d respectively, are in accordance with the observed
moderately low stellar activity level. When comparing NGTS-21b with currently
known transiting hot Jupiters with similar equilibrium temperatures, it is
found to have one of the largest measured radii despite its large mass.
Inflation-free planetary structure models suggest the planet's atmosphere is
inflated by , while inflationary models predict a radius consistent
with observations, thus pointing to stellar irradiation as the probable origin
of NGTS-21b's radius inflation. Additionally, NGTS-21b's bulk density (, g/cm) is also amongst the largest within the population of
metal-poor giant hosts ([Fe/H] < 0.0), helping to reveal a falling upper
boundary in metallicity-planet density parameter space that is in concordance
with core accretion formation models. The discovery of rare planetary systems
such as NGTS-21 greatly contributes towards better constraints being placed on
the formation and evolution mechanisms of massive planets orbiting low-mass
stars.Comment: 12 pages, 13 figures, accepted for publication in MNRA
TOI-199 b: A well-characterized 100-day transiting warm giant planet with TTVs seen from Antarctica
We present the spectroscopic confirmation and precise mass measurement of the
warm giant planet TOI-199 b. This planet was first identified in TESS
photometry and confirmed using ground-based photometry from ASTEP in Antarctica
including a full 6.5h long transit, PEST, Hazelwood, and LCO; space
photometry from NEOSSat; and radial velocities (RVs) from FEROS, HARPS,
CORALIE, and CHIRON. Orbiting a late G-type star, TOI-199\,b has a
period, a mass of
, and a radius of .
It is the first warm exo-Saturn with a precisely determined mass and radius.
The TESS and ASTEP transits show strong transit timing variations, pointing to
the existence of a second planet in the system. The joint analysis of the RVs
and TTVs provides a unique solution for the non-transiting companion TOI-199 c,
which has a period of and an estimated
mass of . This period places it within
the conservative Habitable Zone.Comment: 33 pages, 23 figures. Accepted for publication in A
A long-period transiting substellar companion in the super-Jupiters to brown dwarfs mass regime and a prototypical warm-Jupiter detected by TESS
We report on the confirmation and follow-up characterization of two
long-period transiting substellar companions on low-eccentricity orbits around
TIC 4672985 and TOI-2529, whose transit events were detected by the TESS space
mission. Ground-based photometric and spectroscopic follow-up from different
facilities, confirmed the substellar nature of TIC 4672985 b, a massive gas
giant, in the transition between the super Jupiters and brown dwarfs mass
regime. From the joint analysis we derived the following orbital parameters: P
= 69.0480 d, Mp = 12.74 Mjup, Rp = 1.026 Rjup and e = 0.018. In addition, the
RV time series revealed a significant trend at the 350 m/s/yr level, which is
indicative of the presence of a massive outer companion in the system. TIC
4672985 b is a unique example of a transiting substellar companion with a mass
above the deuterium-burning limit, located beyond 0.1 AU and in a nearly
circular orbit. These planetary properties are difficult to reproduce from
canonical planet formation and evolution models. For TOI-2529 b, we obtained
the following orbital parameters: P = 64.5949 d, Mp = 2.340 Mjup, Rp = 1.030
Rjup and e = 0.021, making this object a new example of a growing population of
transiting warm giant planets.Comment: Accepted in A&
A long-period transiting substellar companion in the super-Jupiters to brown dwarfs mass regime and a prototypical warm-Jupiter detected by TESS
We report on the confirmation and follow-up characterization of two long-period transiting substellar companions on low-eccentricity orbits around TIC 4672985 and TOI-2529, whose transit events were detected by the TESS space mission. Ground-based photometric and spectroscopic follow up from different facilities, confirmed the substellar nature of TIC 4672985 b, a massive gas giant, in the transition between the super-Jupiters and brown-dwarfs mass regime. From the joint analysis we derived the following orbital parameters: P = 69.0480+0.0004â0.0005 d, Mp = 12.74+1.01â1.01 MJ, Rp =1.026+0.065â0.067 RJ and e = 0.018+0.004â0.004 . In addition, the RV time series revealed a significant trend at the ⌠350 m sâ1 yrâ1level, which is indicative of the presence of a massive outer companion in the system. TIC 4672985 b is a unique example of a transiting substellar companion with a mass above the deuterium-burning limit, located beyond 0.1 AU and in a nearly circular orbit. These planetary properties are difficult to reproduce from canonical planet formation and evolution models. For TOI-2529 b, we obtained the following orbital parameters: P = 64.5949+0.0003â0.0003 d, Mp =2.340+0.197â0.195 MJ, Rp = 1.030+0.050â0.050 RJ and e = 0.021+0.024â0.015 , making this object a new example of a growing population of transiting warm giant planets
Three long period transiting giant planets from TESS
We report the discovery and orbital characterization of three new transiting
warm giant planets. These systems were initially identified as presenting
single transit events in the light curves generated from the full frame images
of the Transiting Exoplanet Survey Satellite (TESS). Follow-up radial velocity
measurements and additional light curves were used to determine the orbital
periods and confirm the planetary nature of the candidates. The planets orbit
slightly metal-rich late F- and early G-type stars. We find that TOI 4406b has
a mass of = 0.30 0.04 , a radius of = 1.00 0.02
, and a low eccentricity orbit (e=0.15 0.05) with a period of P=
30.08364 0.00005 d . TOI 2338b has a mass of = 5.98 0.20
, a radius of = 1.00 0.01 , and a highly eccentric orbit (e=
0.676 0.002 ) with a period of P= 22.65398 0.00002 d . Finally, TOI
2589b has a mass of = 3.50 0.10 , a radius of = 1.08
0.03 , and an eccentric orbit (e = 0.522 0.006 ) with a
period of P= 61.6277 0.0002 d . TOI 4406b and TOI 2338b are enriched in
metals compared to their host stars, while the structure of TOI 2589b is
consistent with having similar metal enrichment to its host star.Comment: 24 pages, 16 figures, accepted in A
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