scholarly journals Photoevaporation versus core-powered mass-loss: model comparison with the 3D radius gap

2021 ◽  
Author(s):  
James G Rogers ◽  
Akash Gupta ◽  
James E Owen ◽  
Hilke E Schlichting
Keyword(s):  
Mass Loss ◽  
Model Comparison ◽  
Hypothesis Test ◽  
Space Mission ◽  
Data Sets ◽  
X Ray ◽  
Wide Range ◽  
Cent Level ◽  
Loss Models ◽  
Atmospheric Mass

Abstract The EUV/X-ray photoevaporation and core-powered mass-loss models are both capable of reproducing the bimodality in the sizes of small, close-in exoplanets observed by the Kepler space mission, often referred to as the ‘radius gap’. However, it is unclear which of these two mechanisms dominates the atmospheric mass-loss which is likely sculpting the radius gap. In this work, we propose a new method of differentiating between the two models, which relies on analysing the radius gap in 3D parameter space. Using models for both mechanisms, and by performing synthetic transit surveys we predict the size and characteristics of a survey capable of discriminating between the two models. We find that a survey of ≳ 5000 planets, with a wide range in stellar mass and measurement uncertainties at a $\lesssim 5{{\ \rm per\ cent}}$ level is sufficient. Our methodology is robust against moderate false positive contamination of $\lesssim 10{{\ \rm per\ cent}}$. We perform our analysis on two surveys (which do not satisfy our requirements): the California Kepler Survey and the Gaia-Kepler Survey and find, unsurprisingly, that both data-sets are consistent with either model. We propose a hypothesis test to be performed on future surveys which can robustly ascertain which of the two mechanisms formed the radius gap, provided one dominates over the other.

The subatomic resolution study of laccase inhibition by chloride and fluoride anions using single-crystal serial crystallography: insights into the enzymatic reaction mechanism

2019 ◽  
Vol 75 (9) ◽  
pp. 804-816 ◽  
Author(s):  
Konstantin M. Polyakov ◽  
Sergei Gavryushov ◽  
Tatiana V. Fedorova ◽  
Olga A. Glazunova ◽  
Alexander N. Popov
Keyword(s):  
Molecular Oxygen ◽  
Enzymatic Reaction ◽  
Copper Ion ◽  
Data Sets ◽  
X Ray Diffraction ◽  
Fluoride Ions ◽  
X Ray ◽  
Mechanism Of Inhibition ◽  
Wide Range ◽  
Oxygen Ligand

Laccases are enzymes that catalyze the oxidation of a wide range of organic and inorganic substrates accompanied by the reduction of molecular oxygen to water. Here, a subatomic resolution X-ray crystallographic study of the mechanism of inhibition of the laccase from the basidiomycete fungus Steccherinum murashkinskyi by chloride and fluoride ions is presented. Three series of X-ray diffraction data sets were collected with increasing doses of absorbed X-ray radiation from a native S. murashkinskyi laccase crystal and from crystals of complexes of the laccase with chloride and fluoride ions. The data for the native laccase crystal confirmed the previously deduced enzymatic mechanism of molecular oxygen reduction. The structures of the complexes allowed the localization of chloride and fluoride ions in the channel near the T2 copper ion. These ions replace the oxygen ligand of the T2 copper ion in this channel and can play the role of this ligand in the enzymatic reaction. As follows from analysis of the structures from the increasing dose series, the inhibition of laccases by chloride and fluoride anions can be explained by the fact that the binding of these negatively charged ions at the position of the oxygen ligand of the T2 copper ion impedes the reduction of the T2 copper ion.

Photoevaporation of Water Dominated Exoplanet Atmospheres

2020 ◽  
Author(s):  
Laura Harbach ◽  
James Owen ◽  
Subhanjoy Mohanty
Keyword(s):  
Mass Loss ◽  
Planetary Atmospheres ◽  
Loss Mechanism ◽  
Hydrodynamic Simulations ◽  
X Ray ◽  
Atmospheric Observations ◽  
Low Mass ◽  
The Subject ◽  
Complex Chemistry ◽  
Atmospheric Mass

<p>The atmospheres of close-in, low-mass exoplanets are extremely vulnerable to the effects of stellar UV to X-ray radiation. Photoevaporation can significantly ablate planetary atmospheres or even strip them entirely, potentially rendering a planet inhabitable. Existing hydrodynamical studies of this important atmospheric mass loss mechanism have mainly considered hydrogen/helium dominated atmospheres. Currently, the effect of more complex chemistry on photoevaporative mass loss has only been the subject of a limited number of studies (e.g. Bolmont et al. 2017). In the era of more advanced exoplanet atmospheric observations, it is more important than ever to determine what, if any atmosphere, these planets may have been able to retain. Here, I present preliminary results of hydrodynamic simulations, showing how the atmosphere of a low-mass planet undergoing photoevaporation is affected by the inclusion of water.</p>

scholarly journals Poisson errors and adaptive rebinning in X-ray powder diffraction data

2018 ◽  
Vol 33 (4) ◽  
pp. 266-269 ◽  
Author(s):  
Marcus H. Mendenhall
Keyword(s):  
Powder Diffraction ◽  
Diffraction Data ◽  
Data Sets ◽  
Powder Diffraction Data ◽  
Data Set ◽  
X Ray ◽  
Short Summary ◽  
Correct Assignment ◽  
Wide Range ◽  
Diffraction Patterns

This work provides a short summary of techniques for formally-correct handling of statistical uncertainties in Poisson-statistics dominated data, with emphasis on X-ray powder diffraction patterns. Correct assignment of uncertainties for low counts is documented. Further, we describe a technique for adaptively rebinning such data sets to provide more uniform statistics across a pattern with a wide range of count rates, from a few (or no) counts in a background bin to on-peak regions with many counts. This permits better plotting of data and analysis of a smaller number of points in a fitting package, without significant degradation of the information content of the data set. Examples of the effect of this on a diffraction data set are given.

Quantitative Electron Microprobe Analysis Of Semiconductor Materials: An Evaluation Of Accuracy

1999 ◽  
Vol 5 (S2) ◽  
pp. 74-75
Author(s):  
P.K. Carpenter
Keyword(s):  
Ternary Systems ◽  
Data Sets ◽  
Silicate Mineral ◽  
Data Set ◽  
X Ray ◽  
Quantitative Microanalysis ◽  
Wide Range ◽  
Analytical Accuracy ◽  
Unknown Composition ◽  
Counting Statistics

Both precision and accuracy are central to quantitative microanalysis. While precision may be evaluated from x-ray counting statistics and replicate measurement, the determination of analytical accuracy requires well characterized standards of which there are few that span a wide range of compositions in binary and ternary systems. The accuracy of silicate mineral analysis has been previously studied via measurement of α factors at multiple accelerating potential and the subsequent evaluation of correction algorithms and mass absorption coefficient (mac) data sets. This approach has been extended in this study to the In2O3-Ga2O3 and HgTe-CdTe systems.Single crystals of ln2O3, Ga2O3, and an InGa-oxide of unknown composition were used to evaluate accuracy in the In2O3-Ga2O3 binary, using the GaKα, GaLα, and InLα x-ray lines, with WDS measurements performed at 15, 20, and 25KV relative to the ln2O3 and Ga2O3 standards (see Table I). The Ga Kα line exhibits minimal absorption, has no fluorescence correction in this system and is not critically dependent on the correction algorithm or mac data set used.

Structural study of the X-ray-induced enzymatic reduction of molecular oxygen to water bySteccherinum murashkinskyilaccase: insights into the reaction mechanism

2017 ◽  
Vol 73 (5) ◽  
pp. 388-401 ◽  
Author(s):  
K. M. Polyakov ◽  
S. Gavryushov ◽  
S. Ivanova ◽  
T. V. Fedorova ◽  
O. A. Glazunova ◽  
...  
Keyword(s):  
Molecular Oxygen ◽  
Catalytic Reduction ◽  
Copper Ions ◽  
Absorbed Dose ◽  
Large Family ◽  
Data Sets ◽  
X Ray ◽  
Substrate Complex ◽  
Enzymatic Reduction ◽  
Wide Range

The laccase fromSteccherinum murashkinskyiis a member of the large family of multicopper oxidases that catalyze the oxidation of a wide range of organic and inorganic substrates, accompanied by the reduction of dioxygen to water. The reducing properties of X-ray radiation and the high quality of the laccase crystals allow the study of the catalytic reduction of dioxygen to water directly in a crystal. A series of diffraction data sets with increasing absorbed radiation dose were collected from a single crystal ofSteccherinum murashkinskyilaccase at 1.35 Å resolution. Changes in the active-site structure associated with the reduction of molecular oxygen to water on increasing the absorbed dose of ionizing radiation were detected. The structures in the series are mixtures of different states of the enzyme–substrate complex. Nevertheless, it was possible to interpret these structures as complexes of various oxygen ligands with copper ions in different oxidation states. The results allowed the mechanism of oxygen reduction catalyzed by laccases to be refined.

scholarly journals The Kepler-11 system: evolution of the stellar high-energy emission and initial planetary atmospheric mass fractions

2019 ◽  
Vol 632 ◽  
pp. A65 ◽  
Author(s):  
D. Kubyshkina ◽  
L. Fossati ◽  
A. J. Mustill ◽  
P. E. Cubillos ◽  
M. B. Davies ◽  
...  
Keyword(s):  
Mass Loss ◽  
Extreme Ultraviolet ◽  
High Energy ◽  
X Ray ◽  
System Parameters ◽  
The Past ◽  
Energy Emission ◽  
Mass Fractions ◽  
High Energy Emission ◽  
Atmospheric Mass

The atmospheres of close-in planets are strongly influenced by mass loss driven by the high-energy (X-ray and extreme ultraviolet, EUV) irradiation of the host star, particularly during the early stages of evolution. We recently developed a framework to exploit this connection and enable us to recover the past evolution of the stellar high-energy emission from the present-day properties of its planets, if the latter retain some remnants of their primordial hydrogen-dominated atmospheres. Furthermore, the framework can also provide constraints on planetary initial atmospheric mass fractions. The constraints on the output parameters improve when more planets can be simultaneously analysed. This makes the Kepler-11 system, which hosts six planets with bulk densities between 0.66 and 2.45 g cm−3, an ideal target. Our results indicate that the star has likely evolved as a slow rotator (slower than 85% of the stars with similar masses), corresponding to a high-energy emission at 150 Myr of between 1 and 10 times that of the current Sun. We also constrain the initial atmospheric mass fractions for the planets, obtaining a lower limit of 4.1% for planet c, a range of 3.7–5.3% for planet d, a range of 11.1–14% for planet e, a range of 1–15.6% for planet f, and a range of 4.7–8.7% for planet g assuming a disc dispersal time of 1 Myr. For planet b, the range remains poorly constrained. Our framework also suggests slightly higher masses for planets b, c, and f than have been suggested based on transit timing variation measurements. We coupled our results with published planet atmosphere accretion models to obtain a temperature (at 0.25 AU, the location of planet f) and dispersal time of the protoplanetary disc of 550 K and 1 Myr, although these results may be affected by inconsistencies in the adopted system parameters. This work shows that our framework is capable of constraining important properties of planet formation models.

Electron Beam-Induced Mass Loss in Freeze-Dried Tissue and Protein Samples

1985 ◽  
Vol 43 ◽  
pp. 470-471
Author(s):  
M.E. Cantino ◽  
M.K. Goddard ◽  
L.E. Wilkinson ◽  
D.E. Johnson
Keyword(s):  
Electron Beam ◽  
Salivary Gland ◽  
Mass Loss ◽  
Counting Rate ◽  
Dose Dependence ◽  
X Ray ◽  
Large Samples ◽  
Freeze Dried ◽  
Muscle Homogenate ◽  
Large Muscle

Quantification in biological x-ray microanalysis depends on accurate evaluation of mass loss. Although several studies have addressed the problem of electron beam induced mass loss from organic samples (eg., 1,2). uncertainty persists as to the dose dependence, the extent of loss, the elemental constituents affected, and the variation in loss for different materials and tissues. in the work described here, we used x-ray counting rate changes to measure mass loss in albumin (used as a quantification standard), salivary gland, and muscle.In order to measure mass loss at low doses (10-4 coul/cm2 ) large samples were needed. While freeze-dried salivary gland sections of the required dimensions were available, muscle sections of this size were difficult to obtain. To simulate large muscle sections, frog or rat muscle homogenate was injected between formvar films which were then stretched over slot grids and freeze-dried. Albumin samples were prepared by a similar procedure. using a solution of bovine serum albumin in water. Samples were irradiated in the STEM mode of a JEOL 100C.

Elemental mass loss in silicate minerals during x-ray analysis

1990 ◽  
Vol 48 (4) ◽  
pp. 804-805
Author(s):  
P.E. Champness ◽  
R.W. Devenish
Keyword(s):  
Mass Loss ◽  
Current Density ◽  
Damage Mechanism ◽  
Beam Current ◽  
Single Chain ◽  
Plagioclase Feldspar ◽  
X Ray ◽  
Alkali Ions ◽  
Structural Order ◽  
Sheet Silicate

It has long been recognised that silicates can suffer extensive beam damage in electron-beam instruments. The predominant damage mechanism is radiolysis. For instance, damage in quartz, SiO2, results in loss of structural order without mass loss whereas feldspars (framework silicates containing Ca, Na, K) suffer loss of structural order with accompanying mass loss. In the latter case, the alkali ions, particularly Na, are found to migrate away from the area of the beam. The aim of the present study was to investigate the loss of various elements from the common silicate structures during electron irradiation at 100 kV over a range of current densities of 104 - 109 A m−2. (The current density is defined in terms of 50% of total current in the FWHM probe). The silicates so far ivestigated are:- olivine [(Mg, Fe)SiO4], a structure that has isolated Si-O tetrahedra, garnet [(Mg, Ca, Fe)3Al2Si3AO12 another silicate with isolated tetrahedra, pyroxene [-Ca(Mg, Fe)Si2O6 a single-chain silicate; mica [margarite, -Ca2Al4Si4Al4O2O(OH)4], a sheet silicate, and plagioclase feldspar [-NaCaAl3Si5O16]. Ion- thinned samples of each mineral were examined in a VG Microscopes UHV HB501 field- emission STEM. The beam current used was typically - 0.5 nA and the current density was varied by defocussing the electron probe. Energy-dispersive X-ray spectra were collected every 10 seconds for a total of 200 seconds using a Link Systems windowless detector. The thickness of the samples in the area of analysis was normally 50-150 nm.

Background particle detector for the solar x-ray photometer ChemiX of space mission “Interhelioprobe”: an adjustment of breadboard model modules

2015 ◽  
Vol 21 (2(93)) ◽  
pp. 3-14 ◽  
Author(s):  
O.V. Dudnik ◽  
◽  
E.V. Kurbatov ◽  
V.O. Tarasov ◽  
L.A. Andryushenko ◽  
...  
Keyword(s):  
Space Mission ◽  
Particle Detector ◽  
X Ray ◽  
Background Particle

Counterfeit Parts Recognition and Detection for Failure Analysts

2010 ◽  
Author(s):  
Katherine V. Whittington
Keyword(s):  
Thermal Cycle ◽  
Visual Inspection ◽  
Acoustic Microscopy ◽  
Scanning Acoustic Microscopy ◽  
3D Measurement ◽  
X Ray ◽  
Wide Range ◽  
Electronic Parts ◽  
Testing Awareness

Abstract The electronics supply chain is being increasingly infiltrated by non-authentic, counterfeit electronic parts, whose use poses a great risk to the integrity and quality of critical hardware. There is a wide range of counterfeit parts such as leads and body molds. The failure analyst has many tools that can be used to investigate counterfeit parts. The key is to follow an investigative path that makes sense for each scenario. External visual inspection is called for whenever the source of supply is questionable. Other methods include use of solvents, 3D measurement, X-ray fluorescence, C-mode scanning acoustic microscopy, thermal cycle testing, burn-in technique, and electrical testing. Awareness, vigilance, and effective investigations are the best defense against the threat of counterfeit parts.

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