A novel copper-based metal-organic framework (Cu-MOF) with a large specific surface area and high porosity was synthesized. The Cu-MOF was a good peroxidase-mimicking enzyme and showed a high ...affinity with hydrogen peroxide in a wide pH range. The catalytic mechanism of Cu-MOF has been studied further based on comparing the characteristic of the Cu-MOF with some isomorphic MOFs. The catalytic activity center of Cu-MOF was determined to be the cupric ion rather than the ligand, which effectively promoted the generation of free radicals and electron transfer in the reaction progress. The high affinity of Cu-MOF to hydrogen peroxide proved it as an ideal catalyst for the chemiluminescence (CL) reaction involving hydrogen peroxide. Therefore, the CL method with high sensitivity could be established for detecting various substrates. A double-enzyme CL glucose biosensing platform was constructed for the determination of serum glucose employing the peroxidase-mimicking properties of Cu-MOF as well as glucose oxidase (GOx).
Graphical abstract
ABSTRACT
Gravitational microlensing is unique in detecting binary black (BH) holes with wide (a few au) separations. Models predict that about 1 per cent of microlensing binaries should be due to ...binary BHs, and yet zero has been robustly identified. Using simulated events with binary BH lenses, we show that the microlensing parallax effect in a typical binary BH event cannot be reliably detected. Given the crucial role of the parallax parameter in determining the mass of dark microlenses, this may explain the non-detection of binary BHs. Additionally, we show that in only a small fraction ($\lesssim 7\ \rm{per\ cent}$) of the simulated events the full orbital motion of the binary lens cannot be modelled with the linear orbital motion approximation. This approximation has been frequently used in modellings of binary microlensing events.
A novel copper (Ⅱ) metal-organic framework (Cu(L)(H2O)2nCu-MOF) has been successfully synthesized by facile one step hydrothermal method. Modified the glassy carbon electrode (GCE) with this kind of ...Cu-MOF, a strong cathode electrochemiluminescence (ECL) signal was produced under the potential scan from 0.2 to −1.6 V in the potassium persulfate solution, which was about 8 times higher than that on the bare GCE electrode. The possible enhancement mechanism was studied in detail. The results showed that Cu (Ⅱ) in Cu-MOF catalyzed the reduction of potassium persulfate promoting the conversion of S2O82− into SO4•− and enhancing ECL signal intensively. Based on the inhibition effect of ferrous ion on this ECL signal, a sensitive ECL method for the determination of ferrous ion was developed within the linear range from 1.0 × 10−10 M to 3.0 × 10−8 M and the detection limit of 4 × 10−11 M. The ECL method showed high sensitivity, good stability, and excellent reproducibility and had been applied for analysis of ferrous ion in environmental water samples successfully.
•A novel Cu-MOF has been successfully synthesized by hydrothermal method.•An enhanced ECL signal has been observed with Cu-MOF modified GCE in the K2S2O8 solution.•A sensitive ECL detection of ferrous ion was achieved with Cu-MOF-K2S2O8 system.
ABSTRACT
Only a few wide-orbit planets around old stars have been detected, which limits our statistical understanding of this planet population. Following the systematic search for planetary ...anomalies in microlensing events found by the Korea Microlensing Telescope Network, we present the discovery and analysis of three events that were initially thought to contain wide-orbit planets. The anomalous feature in the light curve of OGLE-2018-BLG-0383 is caused by a planet with mass ratio q = 2.1 × 10−4 and a projected separation s = 2.45. This makes it the lowest mass-ratio microlensing planet at such wide orbits. The other two events, KMT-2018-BLG-0998 and OGLE-2018-BLG-0271, are shown to be stellar binaries (q > 0.1) with rather close (s < 1) separations. We briefly discuss the properties of known wide-orbit microlensing planets and show that the survey observations are crucial in discovering and further statistically constraining such a planet population.
Abstract
We inaugurate a program of “mass production” of microlensing planets discovered in 2021 KMTNet data, with the aim of laying the basis for future statistical studies. While we ultimately plan ...to quickly publish all 2021 planets meeting some minimal criteria, the current sample of four was chosen simply on the basis of having low initial estimates of the planet–host mass ratio,
q
. It is therefore notable that two members of this sample suffer from a degeneracy in the normalized source radius
ρ
that arises from different morphologies of closely spaced caustics. All four planets (KMT-2021-BLG-1391, KMT-2021-BLG-1253, KMT-2021-BLG-1372, KMT-2021-BLG-0748) have well-characterized mass ratios,
q
, and therefore are suitable for mass-ratio frequency studies. Both of the
ρ
degeneracies can be resolved by future adaptive optics (AO) observations on 30 m class telescopes. We provide general guidance for such AO observations for all events in anticipation of the prospect that they will revolutionize the field of microlensing planets.
Abstract
We present the analysis of seven microlensing planetary events with planet/host mass ratios
q
< 10
−4
: KMT-2017-BLG-1194, KMT-2017-BLG-0428, KMT-2019-BLG-1806, KMT-2017-BLG-1003, ...KMT-2019-BLG-1367, OGLE-2017-BLG-1806, and KMT-2016-BLG-1105. They were identified by applying the Korea Microlensing Telescope Network (KMTNet) AnomalyFinder algorithm to 2016–2019 KMTNet events. A Bayesian analysis indicates that all the lens systems consist of a cold super-Earth orbiting an M or K dwarf. Together with 17 previously published and three that will be published elsewhere, AnomalyFinder has found a total of 27 planets that have solutions with
q
< 10
−4
from 2016–2019 KMTNet events, which lays the foundation for the first statistical analysis of the planetary mass-ratio function based on KMTNet data. By reviewing the 27 planets, we find that the missing planetary caustics problem in the KMTNet planetary sample has been solved by AnomalyFinder. We also find a desert of high-magnification planetary signals (
A
≳ 65), and a follow-up project for KMTNet high-magnification events could detect at least two more
q
< 10
−4
planets per year and form an independent statistical sample.
We report the lens mass and distance measurements of the nearby microlensing event TCP J05074264+2447555 (Kojima-1). We measure the microlens parallax vector using Spitzer and ground-based light ...curves with constraints on the direction of lens-source relative proper motion derived from Very Large Telescope Interferometer (VLTI) GRAVITY observations. Combining this determination with the angular Einstein radius measured by VLTI-GRAVITY observations, we find that the lens is a star with mass at a distance DL = 429 21 pc. We find that the blended light basically all comes from the lens. The lens-source proper motion is , so with currently available adaptive-optics instruments, the lens and source can be resolved in 2021. This is the first microlensing event whose lens mass is unambiguously measured by interferometry + satellite-parallax observations, which opens a new window for mass measurements of isolated objects such as stellar-mass black holes.
Abstract We report the analysis of four unambiguous planets and one possible planet from the subprime fields (Γ ≤ 1 hr −1 ) of the 2017 Korea Microlensing Telescope Network (KMTNet) microlensing ...survey, to complete the KMTNet AnomalyFinder planetary sample for the 2017 subprime fields. They are KMT-2017-BLG-0849, KMT-2017-BLG-1057, OGLE-2017-BLG-0364, and KMT-2017-BLG-2331 (unambiguous), as well as KMT-2017-BLG-0958 (possible). For the four unambiguous planets, the mean planet–host mass ratios, q , are (1.0, 1.2, 4.6, 13) × 10 −4 , the median planetary masses are (6.4, 24, 76, 171) M ⊕ , and the median host masses are (0.19, 0.57, 0.49, 0.40) M ⊙ , respectively, found from a Bayesian analysis. We have completed the Anomaly Finder planetary sample from the first 4 yr of KMTNet data (2016–2019), with 112 unambiguous planets in total, which nearly tripled the microlensing planetary sample. The “sub-Saturn desert” ( log q = − 3.6 , − 3.0 ) found in the 2018 and 2019 KMTNet samples is confirmed by the 2016 and 2017 KMTNet samples.
Abstract
We measure the Einstein radius of the single-lens microlensing event KMT-2022-BLG-2397 to be
θ
E
= 24.8 ± 3.6
μ
as, placing it at the upper shore of the Einstein Desert, 9 ≲
θ
E
/
μ
as ≲ 25, ...between free-floating planets (FFPs) and bulge brown dwarfs (BDs). In contrast to the six BD (25 ≲
θ
E
≲ 50) events presented by Gould et al. (2022), which all had giant-star source stars, KMT-2022-BLG-2397 has a dwarf-star source, with angular radius
θ
ast
∼ 0.9
μ
as. This prompts us to study the relative utility of dwarf and giant sources for characterizing FFPs and BDs from finite-source point-lens (FSPL) microlensing events. We find “dwarfs” (including main-sequence stars and subgiants) are likely to yield twice as many
θ
E
measurements for BDs and a comparable (but more difficult to quantify) improvement for FFPs. We show that neither current nor planned experiments will yield complete mass measurements of isolated bulge BDs, nor will any other planned experiment yield as many
θ
E
measurements for these objects as the Korea Microlensing Telescope (KMT). Thus, the currently anticipated 10 yr KMT survey will remain the best way to study bulge BDs for several decades to come.
Abstract
We continue our program of publishing all planets (and possible planets) found by eye in 2021 Korea Microlensing Telescope Network (KMTNet) online data. We present four planets ...(KMT-2021-BLG-0712Lb, KMT-2021-BLG-0909Lb, KMT-2021-BLG-2478Lb, and KMT-2021-BLG-1105Lb), with planet-to-host mass ratios in the range
−
3.3
≲
log
q
≲
−
2.2
. This brings the total of secure, by-eye, 2021 KMTNet planets to 16, including 8 in this series. The by-eye sample is an important check of the completeness of semiautomated detections, which are the basis for statistical analyses. One of the planets, KMT-2021-BLG-1105Lb, is blended with a relatively bright (
I
,
V
) ∼ (18.9, 21.6) star that may be the host. This could be verified immediately by high-resolution imaging. If so, the host is an early G dwarf, and the planet could be characterized by radial velocity observations on 30 m class telescopes.
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