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1.
Liu  Qiong  Liu  Mingwei  Zhan  Shiping  Wu  Lingxi  Xie  Suxia  Chen  Zhaohui  Zhang  Yichen 《Plasmonics (Norwell, Mass.)》2019,14(4):1005-1011

In this paper, a graphene strip is introduced into a metal-insulator-metal (MIM)-integrated square cavity hybrid structure; the transmission spectra are theoretically investigated by the finite different time domain (FDTD) methods. An asymmetric Fano resonance dip that has high figure of merit (FOM) value appears in the transmission band. According to the multimode interference coupled mode theory (MICMT) analytical method, the Fano resonance originates from the coherent coupling between TM10 cavity magnetic mode and graphene plasmonic resonance electric mode. The center wavelength, full width at half maximum (FWHM), and FOM value of the Fano resonance can be tuned dynamically by altering the Fermi level of the graphene. Through breaking the symmetry of the hybrid structure or introducing double graphene strips with different Fermi level into hybrid structure, double Fano resonance are realized. This study can provide some theoretical basis and design reference for designing ultrahigh sensitivity plasmonic sensor.

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2.
Zheng  Gaige  Zhang  Haojing  Bu  Lingbing  Gao  Haiyang  Xu  Linhua  Liu  Yuzhu 《Plasmonics (Norwell, Mass.)》2018,13(1):215-220

A planar silicon carbide/dielectric multilayer structure is investigated in Otto geometry, where surface phonon polaritons and planar waveguide mode can be coupled to realize Fano resonances under transverse magnetic polarization. The resonance coupling is analytically demonstrated using the coupled harmonic oscillator model and numerically presented through rigorous coupled-wave analysis calculations, which shows that the coupling strength between different resonances and the resonant wavelength matching condition plays an important role in the bandwidth and position of the Fano resonance (FR); the magnetic field distribution was also shown to explain the origin of FRs qualitatively.

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3.

In the paper, resonances of different waveguide structures with various vertical indirect coupled cavities were investigated by FDTD (finite difference-time domain). In the silicon cavity, Fano resonance could be observed at about 1430 nm. The coupling distance for the gold cavity/air cavity had less effect on the transmittance of the main waveguide but had a great influence on the transmission for water cavity in the visible region, which showed that water cavity could adjust resonance of waveguide structures. In addition, with the increment of refractive index n, the resonance peak at about 850 nm moved to the long wavelength (redshift). Dispersion rate about 2 × 10–3/nm indicated that the transparent dielectric selectively absorbed the surface plasmon polariton wave and the sensitivity of the waveguide structure designed in this paper has high stability for the refractive index of the main waveguide cavity. Obvious Fano resonance could be observed with the increase of refractive index for silicon cavity. Among the four dielectrics, silicon and water are suitable for studying Fano resonance and filter dielectrics.

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4.

Miniaturized bubble columns (MBCs) have different hydrodynamics in comparison with the larger ones, but there is a lack of scientific data on MBCs. Hence, in this study, the effect of gas hold-up, flow regimes, bubble size distribution on volumetric oxygen mass transfer coefficient at different pore size spargers and gas flow rates in MBCs in the presence and absence of microorganisms were investigated. It was found that flow regime transition occurred around low gas flow rates of 1.18 and 0.85 cm/s for small (16–40 µm) and large (40–100 µm) pore size spargers, respectively. Gas hold-up and KLa in MBC with small size sparger were higher than those with larger one, with an increasing effect in the presence of microorganisms. A comparison revealed that the wall effect on the flow regime and gas hold-up in MBCs was greater than bench-scale bubble columns. The KLa values significantly increased up to tenfold using small pore size sparger. In the MBC and stirred tank bioreactors, the maximum obtained cell concentrations were OD600 of 41.5 and 43.0, respectively. Furthermore, it was shown that in MBCs, higher KLa and lower turbulency could be achieved at the end of bubbly flow regime.

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5.
In this contribution, the size dependent band gap variation of (Zn4/6Cu2/6O)L/(Zn5/6Cu1/6O)L (L is the periodic size) superlattices are investigated with the change of L. The results show that the variation tendency of band gap appears a minimum in S4 (L?=?4) which is nearly a conductor. The band gap of S3 (L?=?3) and S5 (L?=?5) also decrease obviously compared to the other three configurations. Especially, the band gap of S3 has decreased to 2.16?eV which is in the region of narrow bandgap semiconductor. Thus, the band gap can be modulated by alloying through constructing an appropriate variation period. Our ZnCuO superlattices can absorb light in both visible and UV region. These properties make the superlattices a potential application in photocatalysis and the visible light emitter.  相似文献   

6.
Jia  Zi-Xun  Shuai  Yong  Chen  Xiang  Tan  He-Ping 《Plasmonics (Norwell, Mass.)》2016,11(5):1331-1336

In this paper, a theoretical demonstration is given of nanoscale range finding by exciting Fano resonance in coupled gratings. Metallic ridges induce oscillation mode, whose interference with surface plasmon polartions generate narrow Fano resonance. The concept of hybridization is employed to understand the coupling effect of surface plasmon polartions and the oscillation due to metallic ridges. Fano behavior in this structure is captured by using the temporal coupled-mode theory. The gained fundamental understanding opens up new ways to control nanoscale spacing distances and tailor Fano resonance, thus facilitating rational design of nanosensors to improve the performance of nanomotion control systems.

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7.
First estimates of sex allocation patterns and body size‐at‐sexual maturity and at protogynous sex change are presented for the five major (including one endemic) species of parrotfishes of Hawaii. Median body size at initial maturation as a female (LM50) and at protogynous sex change from adult female to adult male (LΔ50) varied greatly among the five species. Estimates of LM50 were about 14, 17, 24, 34 and 35 cm fork length (LF) in palenose Scarus psittacus, Pacific bullethead Chlorurus spilurus, stareye Calotomus carolinus, spectacled Chlorurus perspicillatus and redlip parrotfish Scarus rubroviolaceus. Values of LΔ50 were c. 23, 27, 37, 46 and 47 cm LF in the respective species. Length at female maturation was proportional to maximum body size (Lmax) of the respective species, ranging from 50 to 72% and averaging 62% of Lmax across species. LΔ50 was also proportional to Lmax, ranging from 82 to 97% and averaging 92%. Males of both pairs of Scarus and Chlorurus spp. reported here are diandric. Only one of the five major species (C. carolinus) is functionally monandric, with either all or nearly all males secondarily derived from adult females. The broadly differing absolute body sizes at sexual maturation and at sex change among the five species have important implications for improving regulatory size limits for parrotfishes in the State of Hawaii, where parrotfish species have historically been managed based on a single minimum size limit of 30·5 cm LF. This study provides a model demonstration of why catch data for parrotfishes, and other size‐structured reef‐fish populations, should be recorded either by species or by functional size‐groups of species that allow setting more meaningful minimum size limits.  相似文献   

8.
Arctic vegetation is characterized by high spatial variability in plant functional type (PFT) composition and gross primary productivity (P). Despite this variability, the two main drivers of P in sub‐Arctic tundra are leaf area index (LT) and total foliar nitrogen (NT). LT and NT have been shown to be tightly coupled across PFTs in sub‐Arctic tundra vegetation, which simplifies up‐scaling by allowing quantification of the main drivers of P from remotely sensed LT. Our objective was to test the LTNT relationship across multiple Arctic latitudes and to assess LT as a predictor of P for the pan‐Arctic. Including PFT‐specific parameters in models of LTNT coupling provided only incremental improvements in model fit, but significant improvements were gained from including site‐specific parameters. The degree of curvature in the LTNT relationship, controlled by a fitted canopy nitrogen extinction co‐efficient, was negatively related to average levels of diffuse radiation at a site. This is consistent with theoretical predictions of more uniform vertical canopy N distributions under diffuse light conditions. Higher latitude sites had higher average leaf N content by mass (NM), and we show for the first time that LTNT coupling is achieved across latitudes via canopy‐scale trade‐offs between NM and leaf mass per unit leaf area (LM). Site‐specific parameters provided small but significant improvements in models of P based on LT and moss cover. Our results suggest that differences in LTNT coupling between sites could be used to improve pan‐Arctic models of P and we provide unique evidence that prevailing radiation conditions can significantly affect N allocation over regional scales.  相似文献   

9.
The leaf-specific hydraulic conductivity (K L) of plant stems can control leaf water supply. This property is influenced by variation in leaf/sapwood area ratio (A L/A S) and the specific hydraulic conductivity of xylem tissue (K S). In environments with high atmospheric vapor pressure deficit (VPD), K L may increase to support higher transpiration rates. We predicted that saplings of Acerrubrum and A.pensylvanicum grown in forest canopy gaps, under high light and VPD, would have higher K L and lower A L/A S than similar sized saplings in the understory. Leaf-specific hydraulic conductivity and K S increased with sapling size for both species. In A. rubrum, K S did not differ between the two environments but lower A L/A S (P=0.05, ANCOVA) led to higher K L for gap-grown saplings (P < 0.05, ANCOVA). In A. pensylvanicum, neither K S, A L/A S, nor KL differed between environments. In a second experiment, we examined the impact of sapling size on the water relations and carbon assimilation of A.pensylvanicum. Maximum stomatal conductance for A.pensylvanicum increased with K L (r 2=0.75, P < 0.05). A hypothetical large A. pensylvanicum sapling (2 m tall) had 2.4 times higher K L and 22 times greater daily carbon assimilation than a small (1 m tall) sapling. Size-related hydraulic limitations in A.pensylvanicum caused a 68% reduction in daily carbon assimilation in small saplings. Mid-day water potential increased with A.pensylvanicum sapling size (r 2=0.69, P < 0.05). Calculations indicated that small A.pensylvanicum saplings (low K L) could not transpire at the rate of large saplings (high K L) without reaching theoretical thresholds for xylem embolism induction. The coordination between K L and stomatal conductance in saplings may prevent xylem water potential from reaching levels that cause embolism but also limits transpiration. The K S of the xylem did not vary across environments, suggesting that altering biomass allocation is the primary mechanism of increasing K L. However, the ability to alter aboveground biomass allocation in response to canopy gaps is species-specific. As a result of the increase in K L and K S with sapling size for both species, hydraulic limitation of water flux may impose a greater restriction on daily carbon assimilation for small saplings in the gap environment. Received: 18 February 1997 / Accepted: 23 June 1997  相似文献   

10.
The diet and trophic level (TL) of the yellownose skate Zearaja chilensis in the south‐western Atlantic Ocean (35°–54° S), and how these varied in relation to body size, sex, maturity stage, depth and region were determined by analysis of stomach contents. From 776 specimens analysed, 671 (86·5%) ranging from 180 to 1190 mm total length (LT) had prey in their stomachs. The diet was dominated by fishes, mainly the notothenioid Patagonotothen ramsayi and the Argentine hake Merluccius hubbsi. The consumption of fishes and crabs increased with increasing predator size, and these preys were more important in the north than in the south. Isopods and other crustaceans were consumed more in the south and their consumption decreased as the size of Z. chilensis increased. The TL of Z. chilensis increased with LT from 4·29 to 4·59 (mean 4·53), confirming their ecological role as a top predator. The small and large size classes exhibited a low diet overlap and the highest spatial segregation, whereas medium and large specimens had higher co‐occurrence and dietary overlap indices. A clear distinction in tooth shape was noted between sexes in adult specimens, with males having longer cusps. This sexual heterodonty may be related to reproductive behaviour, increasing the grasping ability of males during courtship, because there were no differences in diet between the sexes.  相似文献   

11.
A simple T-shaped plasmonic nanostructure composed of two perpendicular coupled nanorods is proposed to produce strong Fano resonances. By the near-field coupling between the “bright” dipole and “dark” quadrupole plasmons of the nanorods, a deep Fano dip is formed in the extinction spectrum, which can be well fitted by the Fano interference model. The effects of the geometry parameters including nanorod length, coupling gap size, and coupling location to the Fano resonances are analyzed in detail, and a very high refractive index sensitivity is achieved by the Fano resonance. Also by adjusting the incident polarization direction, double Fano resonances can be formed by the interferences of the dipole, quadrupole, and hexapole plasmons. The proposed nanorod dimer structure is agile, and a trimer which supports double Fano resonances can be easily formed by introducing a third perpendicular coupled nanorod. The proposed T-shaped nanorod dimer structure may have applications in the fields of biological sensing and plasmon-induced transparency.  相似文献   

12.
Age and growth rates of bull shark Carcharhinus leucas[n = 255; 555–2230 mm fork length (LF)] from the northern Gulf of Mexico were estimated from ring counts on vertebral sections collected from fishery‐dependent and ‐independent surveys. Two growth models were fitted to observed data: the von Bertalanffy growth model (VBGM) with t0 as the third parameter and a modified version of the VBGM using a fixed size‐at‐birth intercept as the third parameter. To address the variability in size‐at‐birth, a Monte Carlo simulation was incorporated into the size‐at‐birth intercept. The sex‐specific growth models were not significantly different, allowing a sexes combined model to be generated. The traditional VBGM predicted a theoretical maximum size (L) of 3007·1 mm LF, a growth coefficient (K) of 0·042 year?1 and a theoretical age at zero length (t0) of –6·844 years. The modified VBGM with a fixed size‐at‐birth intercept of 565 mm LF predicted an L of 2289·2 mm LF and a K value of 0·089 year?1. When comparing model estimates to previously published information, the traditional VBGM predicted a significantly lower theoretical maximum size and a higher growth coefficient than those produced using data collected during the 1980s. Overall, results obtained using the VBGM with a fixed size‐at‐birth produced more biologically realistic parameters than that of the VBGM with t0. The Monte‐Carlo simulation incorporating variability in size‐at‐birth produced similar results to the VBGM using a fixed size‐at‐birth. This study provides the first attempt to incorporate variability at size‐at‐birth and provide measurements of variability around the individual parameter estimates for an elasmobranch.  相似文献   

13.
The reproductive biology of the white grunt Haemulon plumierii was studied from 360 individuals obtained from artisanal fisheries landings in the Abrolhos Bank, Brazil, between August 2010 and March 2012. The overall sex‐ratio did not differ significantly from 1:1, although males predominated in larger size classes. β‐Binomial modelling of historical sex‐ratio data indicated that the catch rate of females has increased in recent years. Females reached maturity at a smaller total length (LT; 214 mm) than males (235 mm LT) and the LT at which 50% of all individuals are mature (L50) was 220 mm, corresponding to 41·5% of the maximum recorded LT. Variation in the gonado‐somatic index and in the relative frequency of reproductive stages indicates that reproduction occurs year round, with increased activity during the austral spring and summer. Fecundity was not size dependent. The reproductive parameters provided here can support management measures focussed on seasonal closures during spawning peaks (September to November and February to March) and minimum sizes (>L50) for the capture of this important artisanal fisheries resource in Abrolhos, the region with the largest and most biodiverse coralline reefs in the South Atlantic Ocean.  相似文献   

14.
Abstract

Two new nickel (II) triphenylphosphine complexes derived from tridentate aroylhydrazone ligands [H2L1 = 2-hydroxy-3-methoxybenzylidene)benzohydrazone and H2L2 = N′-(2-hydroxy-3-methoxybenzylidene)-2-hydroxybenzoylhydrazone] and triphenylphosphine were prepared and their molecular structures were determined by single crystal X-ray diffraction analysis. Both nickel(II) complexes showed slightly distorted square planar geometry with one tridentate aroylhydrazone ligand coordinated through ONO donor atoms and one triphenylphosphine ligand coordinated to the nickel center through the phosphorus atom. DNA interaction studies indicated that both complexes possessed higher affinity to herring sperm DNA (HS-DNA) than the corresponding free aroylhydrazone ligand. Molecular docking investigations showed that both complexes could bind to DNA through intercalation of the phenyl rings between adjacent base pairs in the double helix. Meanwhile, bovine serum albumin (BSA) binding studies revealed the complexes could effectively interact with BSA and change the secondary structure of BSA. Further pharmacological evaluations of the synthesized complexes by in vitro antioxidant assays demonstrated high antioxidant activity against NO· and O2˙? radicals. The anticancer activity of each complex was assessed through in vitro cytotoxicity assays (CCK-8 kit) toward A549 and MCF-7 cancer cell and normal L-02 cell lines. Significantly, the Ni(II) complex derived from H2L1 ligand was found to be more effective cytotoxic toward MCF-7cancerous cell with the IC50 value equaled 9.7?μM, which showed potent cytotoxic activity over standard drug cisplatin.

Abbreviations A549 human lung carcinoma cell

BSA bovine serum albumin

CCK-8 Cell Counting Kit-8

DFT density functional theory

DNA deoxyribonucleic acid

DPPH˙ 2,2-diphenyl-1-picrylhydrazyl

H2L1 2-hydroxy-3-methoxybenzylidene)benzohydrazone N′-(2-hydroxy-3-methoxybenzylidene)-2-hydroxybenzoylhydrazone

H2L2 N′-(2-hydroxy-3-methoxybenzylidene)-2-hydroxybenzoylhydrazone

HOMO highest occupied molecular orbital

IC50 the 50% activity

L-02 human normal liver cell

LOMO lowest unoccupied molecular orbital (LUMO)

MCF-7 human breast carcinoma cell

NO˙ nitric oxide

O2˙? superoxide anion

SOD superoxide dismutase

Communicated by Ramaswamy H. Sarma  相似文献   

15.
In the southern Gulf of Mexico, the bonnethead shark, Sphyrna tiburo, is one of the most frequently captured species in landings of small-scale fisheries. Based on the analysis of two fishery-dependent sampling periods (1993–1994 and 2007–2014), this study aimed to determine reproductive parameters and identify temporal differences between the two time periods. In the first sampling period, 776 males and 352 females with a size range of 28.0–120.0 cm total stretched length (LT) were analysed, and in the second sampling period, 387 males and 432 females with a size range of 28.0–122.0 cm LT were analysed. The size at 50% maturity in the second sampling period was significantly different between sexes, 82.6 cm LT for females and 73.8 cm LT for males (no estimation was possible for the first sampling period). The size at 50% maternity was not different between sampling periods, 97.3 cm LT for the first sampling period and 99.0 cm LT for the second sampling period. Litter size varied from 3 to 19 embryos and the average was not statistically different in both periods, 10.1 (S.D. = 3.8) for the first sampling period and 11.3 (S.D. = 3.5) for the second sampling period. The female reproductive cycle is asynchronous, and it seems to be annual, with a gestation period of 5–6 months, and a consecutive ovarian cycle and gestation period. Temporal (between sampling periods) and latitudinal (southern Gulf versus northern regions) variations occur in the synchronicity of the reproductive cycle, temporal variation in the relationship between maternal length and litter size, and latitudinal variation in average size of mature sharks.  相似文献   

16.
To gain a better understanding of the trophic ecology of Pacific blue marlin Makaira nigricans off eastern Taiwan, nitrogen and carbon stable isotopes (δ15N and δ13C) and Bayesian mixing models were used to explore trophic dynamics and potential ontogenetic feeding shifts across M. nigricans of different size classes. Makaira nigricans samples from east of Taiwan (n = 213) and Palau (n = 37), as well as their prey (n = 70), were collected during 2012 and 2013. Results indicated increases in δ15N with size, with values of larger size classes (> 200 cm eye-to-fork length; LEF) significantly higher than those < 200 cm LEF. Values of δ13C were negatively correlated with size. Makaira nigricans > 200 cm LEF had the highest estimated trophic position (4.44) and also exhibited ontogenetic changes in trophic position. Large M. nigricans fed more on dolphinfish Coryphaena hippurus and hairtail Trichiurus lepturus, while smaller M. nigricans consumed smaller forage fish (e.g., moonfish Mene maculata) and cephalopods. These changes may relate to greater swimming speeds and vertical habitat use in larger M. nigricans, allowing capture and consumption of larger prey items at higher trophic positions. The high trophic level of M. nigricans east of Taiwan confirms its important role as an apex predator in marine food webs and how ecological role changes with size.  相似文献   

17.
Hydraulic conductance was measured on leaf and stem segments excised from sugarcane plants at different stages of development. Maximum transpiration rates and leaf water potential (ΨL) associated with maximum transpiration were also measured in intact plants as a function of plant size. Leaf specific hydraulic conductivity (Lsc) and transpiration on a unit leaf area basis (E) were maximal in plants with approximately 0.2 m2 leaf area and decreased with increasing plant size. These changes in Fand Lsc were nearly parallel, which prevented φL in larger plants from decreasing to levels associated with substantial loss in xylem conductivity caused by embolism formation. Coordination of changes in E and leaf hydraulic properties was not mediated by declining leaf water status, since φL increased with plant size. Hydraulic constrictions were present at nodes and in the node-leaf sheath-leaf blade pathway. This pattern of constrictions is in accord with the idea of plant segmentation into regions differing in water transport efficiency and would tend to confine embolisms to the relatively expendable leaves at terminal positions in the pathway, thereby preserving water transport through the stem.  相似文献   

18.
Water movement between a root and the soil depends on the hydraulic conductances of the soil, the root, and the intervening root-soil air gap (Lgap) created as roots shrink during soil drying. To measure Lgap, segments of young cylindrical roots of Agave deserti about 3 mm in diameter were placed concentrically or eccentrically within tubes of moistened filter paper at a known water potential. As the width of the air gap between the filter paper and a concentrically located root was made smaller, measured Lgap increased less than did predicted Lgap based on isothermal conditions. For gaps of the size expected in the soil during water loss from roots (e.g., 10% of the root radius), the underprediction was about 70% and was primarily caused by a lowering of the root surface temperature accompanying water evaporation. As a root segment was eccentrically moved toward the filter paper, the measured Lgap increased. For the most eccentric case of touching the filter paper, the measured Lgap was 2.4-fold greater than for the concentric case, compared with an infinite Lgap predicted if the water potential were constant around the root surface. When a root touched soil with a water potential of -1.0MPa, Lgap estimated using a graphical method increased about 2.3-fold and the overall conductance of the root-soil system increased by 31% compared with the concentric case. For markedly eccentric locations of roots in air gaps, Lgap, which can be the principal conductance initially limiting water loss from roots to a drying soil, can be about 60% of the value predicted for the concentric isothermal case.  相似文献   

19.
The slowing of growth as fish age has long been believed to be related to energy expenditure for maturation, and this rationalization has been used to explain why, across nearly all fish species, the relationship between size at first maturity (Lm) and maximum (Lmax) or asymptotic length (L) is relatively constant. In contrast, the Gill-Oxygen Limitation Theory (GOLT) postulates that (a) fish growth slows because as they grow, their two-dimensional ability to extract oxygen from the water diminishes relative to their three-dimensional weight gain, and (b) they can only invest energy for maturation if oxygen supply at their size at first maturity (Qm) exceeds that needed for maintenance metabolism (Q). It has been reported previously across dozens of marine fish species that the relationship between Qm and Q is linear and, further, it can be mathematically converted to Lm vs. L by raising both terms to the power of D (the gill surface factor), resulting in a slope of 1.36. If the GOLT is universal, a similar slope should exist for LmD vs. LD relationships for freshwater species across multiple individual populations that reside in disparate habitats, although to our knowledge this has never been evaluated. For analysis, we used existing data from previous studies conducted on 51 stream-dwelling populations of redband trout Oncorhynchus mykiss gairdneri, Yellowstone cutthroat trout O. clarkii bouvieri and mountain whitefish Prosopium williamsoni. The resulting LmD vs. LD slopes combining all data points (1.35) or for all species considered separately (range = 1.29–1.40) were indeed equivalent to the slope originally produced for the marine species from which the GOLT-derived relationship was first reported. We briefly discuss select papers both supporting and resisting various aspects of the GOLT, note that it could potentially explain shrinking sizes of marine fish, and call for more concerted research efforts combining laboratory and field expertise in fish growth research.  相似文献   

20.
Anadromous trout Salmo trutta exhibits sexual size dimorphism (SSD); females were larger than males in populations where male mean total length (LT) at maturity was below 49 cm and females were smaller than males when mean male LT was above 49 cm, the slope of the regression of female on male LT was 0·59. In streams with mean annual discharge below 41 m3 s?1, flow added significantly to a model with SSD as the dependent variable and male mean LT at maturity as the first predictor variable. There was a slight increase in SSD with increasing latitude, which may result from an increase in male size with increasing latitude.  相似文献   

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