A discovery of gravitational waves from binary black holes raises a possibility that measurements of them can provide strict tests of CPT invariance in gravitational waves. When CPT violation exists, ...if any, gravitational waves with different circular polarizations could gain a slight difference in propagating speeds. Hence, the birefringence of gravitational waves is induced and there should be a rotation of plus and cross modes. For CPT-violating dispersion relation
ω
2
=
k
2
±
2
ζ
k
3
, where a sign
±
denotes different circular polarizations, we find no substantial deviations from CPT invariance in gravitational waves by analyzing a compilation of ten signals of binary black holes in the LIGO-Virgo catalog GWTC-1. We obtain a strict constraint on the CPT-violating parameter, i.e.,
ζ
=
0
.
14
-
0.31
+
0.22
×
10
-
15
m
, which is around two orders of magnitude better than the existing one. Therefore, this study stands for the up-to-date strictest tests of CPT invariance in gravitational waves.
Two gravitational wave events, i.e. GW200105 and GW200115, were observed by the Advanced LIGO and Virgo detectors recently. In this work, we show that they can be explained by a scenario of ...primordial black hole binaries that are formed in the early Universe. The merger rate predicted by such a scenario could be consistent with the one estimated from LIGO and Virgo, even if primordial black holes constitute a fraction of cold dark matter. The required abundance of primordial black holes is compatible with the existing upper limits from microlensing, caustic crossing and cosmic microwave background observations.
Abstract
Gravitational waves would attain birefringence during their propagation from distant sources to the Earth, when the charge, parity, and time reversal (CPT) symmetry is broken. If it was ...sizeable enough, such birefringence could be measured by the Advanced LIGO, Virgo, and KAGRA detector network. In this work, we place constraints on the birefringence of gravitational waves with the third observing run of this network, i.e., two catalogs GWTC-2 and GWTC-3. For the dispersion relation
ω
2
=
k
2
± 2
ζ
k
3
, our analysis shows the up-to-date strictest limit on the CPT-violating parameter, i.e.,
ζ
=
4.07
−
5.79
+
5.91
×
10
−
17
m
, at 68% confidence level. This limit is stricter by ∼5 times when compared to the existing one (∼2× 10
−16
m) and stands for the first ∼10 GeV-scale test of the CPT symmetry in gravitational waves. The results of the Bayes factor strongly disfavor the birefringence scenario of gravitational waves.
We conduct numerical investigations on turbulent Rayleigh–Bénard (RB) convection modulated by oscillating filaments, where an array of active filaments is adhered to the bottom surface. Our study ...focuses on the dependence of global heat transfer, quantified by the Nusselt number (Nu), on the rigidity (B) of the active filaments under various oscillation frequencies (ω). We reveal two critical filament rigidities, Bc1 and Bc2, delineating distinct heat transfer regimes: (I) Soft regime (B<Bc1), where negligibly small filament rigidity allows for obvious bending, and Nu decreases with increasing rigidity B in this regime. (II) Elastic bending regime (Bc1<B<Bc2), where elastic bending of filament takes place, inducing swaying motion near the filament root and subsequently perturbing the boundary layers to favor thermal plumes emission. In this regime, Nu noticeably increases with rising rigidity. (III) Stiff regime (B>Bc2), characterized by minimal deformation induced by filament–fluid interaction and the saturation of heat transfer enhancement. Furthermore, we analyze the competition between bending and inertial forces experienced by the filaments through comparing their relative magnitude, from which we theoretically determine both critical rigidities Bc. Our study offers valuable insights into the intricate dynamics of active filaments in turbulent convection, advancing our understanding of heat transfer modulation in active environments with dynamically driving agents.
•Mechanism of heat transfer modulation by active filament has been elucidated.•Three heat transfer regimes are identified depending on filament rigidity.•Critical filament rigidity is determined by the competition between bending and inertial forces.
Understanding the relationship between liquid manipulation and micro‐/nanostructured interfaces has gained much attention due to the wide potential applications in many fields, such as chemical and ...biomedical assays, environmental protection, industry, and even daily life. Much work has been done to construct various materials with interfacial liquid manipulation abilities, leading to a range of interesting applications. Herein, different fabrication methods from the top‐down approach to the bottom‐up approach and subsequent surface modifications of micro‐/nanostructured interfaces are first introduced. Then, interactions between the surface and liquid, including liquid wetting, liquid transportation, and a number of corresponding models, together with the definition of hydrophilic/hydrophobic, oleophilic/olephobic, the definition and mechanism of superwetting, including superhydrophobicity, superhydrophilicity, and superoleophobicity, are presented. The micro‐/nanostructured interface, with major applications in self‐cleaning, antifogging, anti‐icing, anticorrosion, drag‐reduction, oil–water separation, water collection, droplet (micro)array, and surface‐directed liquid transport, is summarized, and the mechanisms underlying each application are discussed. Finally, the remaining challenges and future perspectives in this area are included.
Understanding the relationship between liquid manipulation and micro‐/nanostructured interfaces is important in many applications. Here, the relationship between liquid manipulation and micro‐/nanostructured interfaces, including liquid wetting and liquid transportation, is revealed. Their wide applications in self‐cleaning, antifogging, anti‐icing, anticorrosion, drag‐reduction, oil–water separation, water collection, droplet (micro)arrays, and surface‐directed liquid transport are presented.
A new type of physically linked double‐network hydrogel is synthesized by a simple, time‐saving, facile, easily controlled, one‐pot method. The resulting agar/polyacrylamide double‐network hydrogels ...exhibit good mechanical properties, excellent recoverability, and a unique free‐shapeable property, which makes them very promising hydrogels for load‐bearing soft tissues.
A method for the regiodivergent and stereoselective hydrosilylation of the basic industrial feedstock isoprene with unactivated silanes has been developed using earth‐abundant iron catalysts. The ...manipulation of regioselectivity relies on fine modification of the coordination geometry of the iron center. While a bidentate pyridine imine ligand promoted the formation of allylic silanes through 4,1‐addition, selectivity for the 3,4‐adduct homoallylic silanes was observed with a tridentate nitrogen ligand. Experimental studies and analysis were carried out to elucidate the reaction mechanism and the factors enabling manipulation of the regioselectivity. This study contributes to the art of regioselectivity control in alkene hydrofunctionalization.
A ligand‐regulated regiodivergent and stereoselective hydrosilylation of terpenes has been developed using earth‐abundant iron catalysts. Various silanes and terpenes were transformed with excellent selectivity into the corresponding allylic silanes and homoallylic silanes through 4,1‐ and 3,4‐addition, respectively.
Oxidative stress and inflammatory responses are closely implicated in the progression of renal interstitial fibrosis, thereby leading to chronic kidney disease. Cryptotanshinone (CTS) is a natural ...compound involved in antioxidant and anti‐inflammatory activities. We evaluated the effects of CTS on inflammation and oxidative stress in obstructed kidneys. Mice received gastric gavage of CTS from 7 days before unilateral ureteral obstruction operation to 1 week after surgery. Administration of CTS at 50 and 100 mg/kg/day significantly decreased collagen production, as shown by Masson staining. Immunohistochemistry staining and RT‐PCR confirmed that CTS reduced extracellular matrix proteins, such as fibronectin and collagen‐1, in the obstructed kidneys in a dose‐dependent manner. Furthermore, immunohistochemistry staining indicated that CTS inhibited infiltration of the macrophage (CD68‐positive) and lymphocyte (CD3‐positive) cells, which were associated with the suppression of the nuclear factor‐κB signalling activation. CTS increased superoxide dismutase, catalase and glutathione while decreased malondialdehyde production. More importantly, CTS activated Nrf‐2 and HO‐1 in the obstructed kidneys for 7 days. CTS could protect renal interstitial fibrosis by ameliorating inflammation and oxidative stress, which might be through the regulation of NF‐κB and Nrf‐2/HO‐1 signalling pathways.
The basic industrial feedstock isoprene was employed as a building block to install prenyl and reverse‐prenyl groups onto indoles. The regioselectivity can be manipulated by the choice of metal ...hydride. Reverse‐prenylated indoles were attained with high selectivity when using Rh−H. By switching to a Pd−H catalyst, selectivity toward prenylated indoles was achieved. This regiodivergent method also features high atom economy without stoichiometric byproduct formation.
Backwards and forwards: A metal hydride mediated regiodivergent coupling of indoles with the industrial feedstock isoprene was developed for which the regioselectivity for prenylation versus reverse prenylation is determined by the choice of metal hydride. This method enables the installation of prenyl and reverse‐prenyl motifs onto indoles with high atom economy.
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