Abstract
We have collected 10,025 foreground–background quasar pairs with projected distances
d
p
< 500 kpc from the large quasar catalog of the Sloan Digital Sky Survey DR16Q. We investigate the ...properties of the Mg
ii
absorption lines with
W
r
> 0.15 Å around foreground quasars, including both the line of sight (LOS; of foreground quasars) and transverse (TRA; perpendicular to the LOS) absorptions. Both the equivalent width (the correlation coefficient
ρ
= −0.915 and the probability
P
< 10
−4
of no correlation) and incident rate (
ρ
= −0.964 and
P
< 10
−6
) of TRA Mg
ii
absorption lines are obviously anticorrelated with projected distance. The incident rate of TRA Mg
ii
absorption lines is obviously (>4
σ
) greater than that of LOS Mg
ii
absorption lines at projected distances
d
p
< 200 kpc, while the TRA and LOS Mg
ii
both have similar (<3
σ
) incident rates at scales
d
p
> 200 kpc. The anisotropic radiation from quasars would be the most possible interpretation for the anisotropic absorption around quasars. This could also indicate that the quasar radiation is not obviously impacting the gas halos of quasars at scales
d
p
> 200 kpc.
Herein, the electrodeposited-film electrode CFeCoNiP was fabricated to serve as a bifunctional electrocatalyst for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Kinetic ...Tafel slope analysis suggests that the HER follows the Volmer-Tafel mechanism (29 mV dec
−1
), indicating that the recombination of the two adsorbed hydrogen atoms is the rate-determining step. The FeCoNi-based thick film (thickness: 168.3 μm) shows a metallic state favorable for electron transfer; on the other hand, in the case of the FeCoNi-based thin film (thickness: 389.2 nm), the in
operando
XAS investigation reveals that Fe
3+
-assisted water dissociation promotes the formation of Co
2+
-μ-H-Ni
3+
(catalyst-H
ad
) species, which subsequently undergoes reductive elimination to furnish H
2
gas
via
the HER process. During the OER, the CoNi-oxide matrix acts as a chemical and electroconductive host to build/stabilize the key intermediate Fe
4+
&z.dbd;O/Fe
3+
-O&z.rad; motifs; this subsequently triggers the catalytic O-O bond formation (30 mV dec
−1
) through the radical-radical coupling of the adjacent Fe
4+
&z.dbd;O/Fe
3+
-O&z.rad; motifs or/and OH
−
attack on the Fe
4+
-induced electrophilic oxygen center, leading to the release of O
2
. The mechanistic experiments provide advanced insights into the catalytic kinetics/intermediates and demonstrate that the electronically cooperative interplay among Fe/Co/Ni leads to enhanced alkaline water electrolysis. The CFeCoNiP catalyst exhibits an excellent HER activity (specific activity
j
s
= 0.227 mA cm
−2
) with a low charge transfer resistance (3.9 Ω) and an overpotential of 37 mV, achieving the current density of 10 mA cm
2
; moreover, it shows good OER activity (
j
s
= 1.798 mA cm
−2
) with low charge transfer resistance (2.1 Ω) and an overpotential of 250 mV, approaching a current density of 10 mA cm
−2
in a 1 M NaOH aqueous solution. The CFeCoNiP/NF (electrodeposited on Ni foam) electrode-pair device achieved the current densities of 100 and 500 mA cm
−2
at the voltages of 1.65 and 1.86 V, respectively, under alkaline conditions.
In operando XAS investigation on FeCoNi-based thin film unravels that Fe
3+
-assisted water dissociation promotes the formation of Co
2+
-μ-H-Ni
3+
species, and the conductive character of Co
2+
Ni
3+
-oxide matrix facilitates the coupling of adjacent Fe
4+
&z.dbd;O/Fe
3+
-O&z.rad; motifs.
Background & Aims Solid tumors often become hypoxic, leading to activation of hypoxia-response genes. We investigated the effects of overexpression of the hypoxia response genes eIF5A2 in esophageal ...squamous cell carcinoma (ESCC). Methods We used quantitative real-time polymerase chain reaction and immunohistochemistry analyses to compare expression of eIF5A2 between paired ESCC samples and nontumor esophageal tissues, and fluorescence in situ hybridization to detect gene copy-number alterations. Luciferase reporter and chromatin immunoprecipitation assays were used to study interactions between eIF5A2 and hypoxia-inducible factor-1α ( HIF1α ). We determined the effects of eIF5A2 overexpression and knockdown in ESCC cell lines and growth of ESCC xenograft tumors in nude mice. Results Levels of eIF5A2 messenger RNA and protein were increased in >40% of ESCC samples compared with matched nontumor tissues, along with levels of HIF1α and vascular endothelial growth factor. Increased levels of EIF5A2 were significantly associated with ESCC metastasis to lymph nodes ( P < .001) and tissue invasion ( P = .037), and shorter survival times of patients ( P < .001). Amplification of eIF5A2 was detected in 35.14% of ESCC samples that overexpressed eIF5A2. Hypoxia increased expression of eIF5A2 4- to 8-fold in ESCC cell lines; we observed bidirectional regulation between eIF5A2 and HIF1α . Transient transfection of ESCC cell lines with eIF5A2 increased their migratory and invasive abilities and markers of the epithelial to mesenchymal transition, and eIF5A2 knockdown or HIFα inhibition reduced these. In mice, xenograft tumors grown from ESCC cells that expressed eIF5A2 formed tumors more rapidly than cells that expressed only vector (controls); they also expressed higher levels of HIF1α and vascular endothelial growth factor, and formed more microvessels than controls. Knockdown of eIF5A2 in ESCC cells with interfering RNAs reduced their growth as xenograft tumors in mice, particularly when mice were given docetaxel or cisplatin. Conclusions eIF5A2 is overexpressed by gene amplification or hypoxia in ESCCs, and associated with up-regulation of HIF1α, metastasis, and shorter survival times of patients. Increased expression of eIF5A2 increases metastasis and angiogenesis in ESCC via the HIF1α -mediated signaling pathway.
Four heteroleptic copper(I) complexes containing phenanthroline and monoanionic nido‐carborane‐diphosphine ligands have been prepared and structurally characterized by various spectroscopic ...techniques and X‐ray diffraction. These complexes exhibit intense absorptions in the visible range and excited‐state lifetimes on the microsecond scale. Their application in visible‐light‐induced cross‐dehydrogenative coupling reactions was investigated. Preliminary studies showed that one of the four copper(I) complexes is an efficient catalyst for photoinduced oxidative CH functionalization using oxygen as oxidant. Furthermore, α‐functionalized tertiary amines were obtained in good‐to‐excellent yields by light irradiation (λ>420 nm) of a mixture of our CuI complex, tertiary amines, and a variety of nucleophiles (nitroalkane, acetone, or indoles) under aerobic conditions. Electron paramagnetic resonance measurements provided evidence for the formation of superoxide radical anions (O2−⋅) rather than singlet oxygen (1O2) during these photocatalytic reactions.
Oxidative cross‐coupling: The long‐lived excited states of heteroleptic copper(I) complexes containing phenanthroline and monoanionic nido‐carborane‐diphosphine ligands catalyze oxidative CC coupling reactions with oxygen as the oxidant under visible‐light irradiation (see figure).
The recombination of electron–hole pairs severely detracts from the efficiency of photocatalysts. This issue could be addressed in metal–organic frameworks (MOFs) through optimization of the ...charge-transfer kinetics via rational design of structures at atomic level. Herein, a pyrazolyl porphyrinic Ni-MOF (PCN-601), integrating light harvesters, active catalytic sites, and high surface areas, has been demonstrated as a superior and durable photocatalyst for visible-light-driven overall CO2 reduction with H2O vapor at room temperature. Kinetic studies reveal that the robust coordination spheres of pyrazolyl groups and Ni-oxo clusters endow PCN-601 with proper energy band alignment and ultrafast ligand-to-node electron transfer. Consequently, the CO2-to-CH4 production rate of PCN-601 far exceeds those of the analogous MOFs based on carboxylate porphyrin and the classic Pt/CdS photocatalyst by more than 3- and 20-fold, respectively. The reaction avoids the use of hole scavengers and proceeds in a gaseous phase which can take full advantage of the high gas uptake of MOFs. This work demonstrates that the rational design of coordination spheres in MOF structures not only reconciles the contradiction between reactivity and stability but also greatly promotes the interfacial charge transfer to achieve optimized kinetics, providing guidance for the design of highly efficient MOF photocatalysts.
Abstract It is commonly accepted that outflows from the central regions of quasars play a substantial role in regulating the global properties of the host galaxy. These outflows are typically ...detected through blueshifted absorption lines. However, the question remains whether outflows observed with different absorption line types indeed reflect the same environmental or evolutionary stage of the host galaxy. In this study, we use the Sloan Digital Sky Survey quasar catalog and employ the flux ratio of O II and Ne V emission lines as indicators to compare star formation rates (SFRs) within host galaxies of quasars exhibiting various outflow absorption line types: low-ionization broad absorption line (LoBAL), low-ionization Mini-BAL (LoMini-BAL), low-ionization narrow absorption line (LoNAL), high-ionization broad absorption line (HiBAL), high-ionization Mini-BAL (HiMini-BAL), and high-ionization narrow absorption line (HiNAL). Our findings indicate that the SFR of LoMini-BAL quasars is comparable to that of LoNAL quasars, somewhat less than that of LoBAL quasars, but markedly greater than that of HiBAL quasars. Furthermore, the SFR of HiMini-BAL quasars mirrors that of HiNAL or Non-abs (no associated absorption lines) quasars, but is significantly higher than that of HiBAL quasars. If we consider that differing absorption line types are indicative of the quasar evolution stage, our results propose an inclusive evolution sequence: LoBALs evolve into LoMini-BALs/LoNALs, then progress to HiBALs, and ultimately morph into HiMini-BALs/HiNALs/Non-abs. Concomitantly, the SFR within the host galaxies of quasars appears to decline noticeably nearing the LoNAL phase’s end and rejuvenates before the HiMini-BAL phase.
Recent rapid development in homogeneous gold catalysis affords an alternative and particularly thriving strategy for the generation of gold carbenes through gold-catalyzed ...oxidation/amination/cycloaddition of alkynes, while it avoids the employment of hazardous and potentially explosive diazo compounds as starting materials for carbene generation. In addition to facile and secure operation, gold carbenes generated in this strategy display good chemoselectivity distinct from other metal carbenes produced from the related diazo approach. N-heterocyclic carbene (NHC) gold is a special metal complex that can be used as ancillary ligands, which provides enhanced stability and can also act as an efficient chiral directing group. In this review, we will present an overview of these recent advances in alkyne oxidation/amination/cycloaddition by highlighting their specificity and applicability, aiming to facilitate progress in this very exciting area of research.
One of the key challenges in artificial photosynthesis is to design a photocatalyst that can bind and activate the CO2 molecule with the smallest possible activation energy and produce selective ...hydrocarbon products. In this contribution, a combined experimental and computational study on Ni‐nanocluster loaded black TiO2 (Ni/TiO2Vo) with built‐in dual active sites for selective photocatalytic CO2 conversion is reported. The findings reveal that the synergistic effects of deliberately induced Ni nanoclusters and oxygen vacancies provide (1) energetically stable CO2 binding sites with the lowest activation energy (0.08 eV), (2) highly reactive sites, (3) a fast electron transfer pathway, and (4) enhanced light harvesting by lowering the bandgap. The Ni/TiO2Vo photocatalyst has demonstrated highly selective and enhanced photocatalytic activity of more than 18 times higher solar fuel production than the commercial TiO2 (P‐25). An insight into the mechanisms of interfacial charge transfer and product formation is explored.
Black titania incorporated with dual reactive sites (Ni‐nanocluster and oxygen vacancy) converts carbon dioxide selectively into acetaldehyde with sunlight and water. The enhancement in photocatalytic activity and product selectivity is attributed to the synergistic effect of the two active sites which alter the optical, electrical, and chemical properties of the black TiO2.
Soybean (Glycine max (L.) Merr.) is a typical short-day and warm season plant, and the interval between emergence and flowering has long been known to be regulated by environmental factors, primarily ...photoperiod and temperature. While the effects of photoperiod and temperature on soybean flowering have been extensively studied, a dissection of the component photo-thermal effects has not been documented for Chinese germplasm. Our objective of the current study was to evaluate the independent- and interactive-photo-thermal responses of 71 cultivars from 6 ecotypes spanning the soybean production regions in China. These cultivars were subjected in pot experiments to different temperature regimes by planting in spring (low temperature (LT)) and summer (high temperature (HT)), and integrating with short day (SD, 12 h), natural day (ND, variable day-length), and long day (LD, 16 h) treatments over two years. The duration of the vegetative phase from emergence to first bloom (R1) was recorded, and the photo-thermal response was calculated. The outcome of this characterization led to the following conclusions: (1) There were significant differences in photo-thermal response among the different ecotypes. High-latitude ecotypes were less sensitive to the independent- and interactive-photo-thermal effects than low-latitude ecotypes; and (2) there was an interaction between photoperiod and temperature, with the effect of photoperiod on thermal sensitivity being greater under the LD than the SD condition, and with the effect of temperature on photoperiodic sensitivity being greater under the LT than the HT condition. The strengths and limitations of this study are discussed in terms of implications for current knowledge and future research directions. The study provides better understanding of photo-thermal effects on flowering in soybean genotypes from different ecotypes throughout China and of the implications for their adaptation more broadly.
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