AIM: To compare n-butyl-2-cyanoacrylate, iso-amyl-2-cyanoacrylate and a mixture of 72% chromated glycerin with hypertonic glucose solution in management of gastric varices. METHODS: Ninety patients with gastric varice...AIM: To compare n-butyl-2-cyanoacrylate, iso-amyl-2-cyanoacrylate and a mixture of 72% chromated glycerin with hypertonic glucose solution in management of gastric varices. METHODS: Ninety patients with gastric varices presented to Endoscopy Unit of Ain Shams University Hospital were included. They were randomly allocated into three groups; each group included 30 patients treated with intravariceal sclerosant injections in biweekly sessions till complete obturation of gastric varices; Group I(n-butyl-2-cyanoacrylate; Histoacryl), Group II(iso-amyl-2-cyanoacrylate; Amcrylate) and Group III(mixture of 72% chromated glycerin; Scleremo with glucose solution 25%). All the procedures were performed electively without active bleeding. Recruited patients were followed up for 3 mo. RESULTS: 26% of Scleremo group had bleeding during puncture vs 3.3% in each of the other two groups with significant difference,(P < 0.05). None of Scleremo group had needle obstruction vs 13.3% in each of the other two groups with no significant difference,(P > 0.05). Rebleeding occurred in 13.3% of Histoacryl and Amcrylate groups vs 0% in Scleremo group with no significant difference. The in hospital mortality was 6.6% in both Histoacryl and Amcrylate groups, while it was 0% in Scleremo group with no significant difference. In the first and second sessions, the amount of Scleremo needed for obturation was significantly high, while the amount of Histoacryl was significantly low. Scleremo was the less costly of the two treatments. CONCLUSION: All used sclerosant substances showed efficacy and success in management of gastric varices with no significant differences except in total amount, cost and bleeding during puncture.展开更多
A no pollution organic acid based conversion coating solution MIS. No.1 has been examined as to its suitability as possible replacement for chromate containing formulations on magnesium alloys. Investigations have con...A no pollution organic acid based conversion coating solution MIS. No.1 has been examined as to its suitability as possible replacement for chromate containing formulations on magnesium alloys. Investigations have concentrated on the formation of passive film from simple MIS. No.1 solution using immersion. The morphology of passivated surfaces was examined using scanning electron microscopy (SEM). The corrosion resistance of the passivated surfaces and the painted surface was assessed using electrochemical techniques as well as humidity and salt fog tests. It was concluded that the surface treatment magnesium alloy by MIS.No.1 solution is more effective than that by chromate coating treatment, and the MIS.No.1 coating is also suitable for painting’s pretreatment.展开更多
Arthrobacter sp. SUK 1205 isolated from metalliferous chromite mine environment of Orissa, India showed wide degree of tolerance to heavy metals including Cr(VI), variety of antibiotics and was also capable of reducin...Arthrobacter sp. SUK 1205 isolated from metalliferous chromite mine environment of Orissa, India showed wide degree of tolerance to heavy metals including Cr(VI), variety of antibiotics and was also capable of reducing Cr(VI) during growth. Freshly grown whole cells of this bacterium were evaluated for chromate reduction under batch culture using Vogel Bonner (V. B.) broth as the base. Cells of SUK 1205 were capable of completely reducing 100 μM Cr(VI) in V. B. broth within 48 h of incubation. Reduction of chromate increased with increase in cell density which attained maximum at 1010 cells/ml, however, reverse was the phenomenon when the concentration of Cr(VI) increased gradually. Glycerol, glycine and glucose promoted chromate reduction efficiency of the cells when used as electron donors. Optimum pH and temperature were found to be 7.0 and 35°C respectively. The process of reduction was inhibited by Ni(II), Mn(II), Zn(II) and Co(II), but Cu(II) and Fe(III) was promotive in nature. On the other hand, 2, 4-dinitrophenol was found to be neither promotive nor inhibitory for the reduction process, but carbonyl cyanide-m-chloro phenyl hydrazone, sodium azide, sodium fluoride and N,N,-dicyclohexyl carboiimide were inhibitory. Cells of SUK 1205 when permeabilized with toluene, triton X-100 and tween 80 showed an enhancement of the process and thereby indicated that reduction of Cr(VI) was mainly associated with soluble component of the cells. Arthrobacter sp. SUK 1205, therefore, showed great promise for use in Cr(VI) detoxification under a wide range of environmental conditions.展开更多
The corrosion resistance of a low concentration chromate passive film for zinc based alloy coated steel wires was assessed by salt spray and electrochemical corrosion tests. XPS and AES analyses showed that the compos...The corrosion resistance of a low concentration chromate passive film for zinc based alloy coated steel wires was assessed by salt spray and electrochemical corrosion tests. XPS and AES analyses showed that the composition of such chromate passive film was S 5 5, Na 3 4, C 11 8, Ti 7 9, O 41 6, Cr 13 7, Zn 16 0.展开更多
Over 2 million tons of chromate residues as hazardous wastes have been accumulated from chromate production processes during the past more than 30 years in China. Some serious pollution problems have been caused due t...Over 2 million tons of chromate residues as hazardous wastes have been accumulated from chromate production processes during the past more than 30 years in China. Some serious pollution problems have been caused due to no appropriate technology and management. Approaches are reviewed to pollution control of chromate residues by utilizing them as secondary resources in this paper. In addition to legislation for pollution control, chromate residues can be used as raw materials to produce a great diversity of useful industrial products. Strategies are also recommanded for the resourcefulization of chromate residues.展开更多
Sodium chromate solubility is determined in the range of NaOH concentrations from 450 to 810 g/L andsolution temperatUres from 30 to 110℃. The optimized conditions to separate sodium chromate from NaOH inleached solu...Sodium chromate solubility is determined in the range of NaOH concentrations from 450 to 810 g/L andsolution temperatUres from 30 to 110℃. The optimized conditions to separate sodium chromate from NaOH inleached solution are resolved. It is first found the method to efficiently separate sbdium chromate from NaOH andsodium altuninate in crude sodium chromate. Bench-scale studies on the separating are performed. Finally, goodseparation results are achieved.展开更多
Ni-based anodes of SOFCs are susceptible to coking, which greatly limits practical application of direct methane-based fuels. An indirect internal reformer is an effective way to convert methane-based fuels into synga...Ni-based anodes of SOFCs are susceptible to coking, which greatly limits practical application of direct methane-based fuels. An indirect internal reformer is an effective way to convert methane-based fuels into syngas before they reach anode. In this work, catalytic activity of a redox-stable perovskite La0.7Sr0.3Cr0.8Fe0.2O3-δ(LSCrFO) for methane conversion was evaluated. The catalyst was fabricated as an anodic protective layer to improve coking resistance of a Ni cermet anode. Using wet CH4 as a fuel, the LSCrFO-modified cell showed excellent power output and good coking resistance with peak power density of 1.59 W cm-2 at 800℃. The cell demonstrated good durability lasting for at least 100 h. While the bare cell without the protective layer showed poor durability with the cell voltage fast dropped from 0.75 V to 0.4 V within 30 min. Under wet coal bed methane (CBM) operation, obvious performance degradation within 35 h (1.7 mV h^-1) was observed due to the influence of heavy carbon compounds in CBM. The pre-and post-mortem microstructures and carbon analysis of the anode surface and catalyst surface were further conducted.展开更多
A putative chromate ion binding site was identified proximal to a rigidly bound FMN from electron densities in the crystal structure of the quinone reductase from Gluconacetobacter hansenii (Gh-ChrR) (3s2y.pdb). To cl...A putative chromate ion binding site was identified proximal to a rigidly bound FMN from electron densities in the crystal structure of the quinone reductase from Gluconacetobacter hansenii (Gh-ChrR) (3s2y.pdb). To clarify the location of the chromate binding site, and to understand the role of FMN in the NADPH-dependent reduction of chromate, we have expressed and purified four mutant enzymes involving the site-specific substitution of individual side chains within the FMN binding pocket that form non-covalent bonds with the ribityl phosphate (i.e., S15A and R17A in loop 1 between β1 sheet and α1 helix) or the isoalloxanzine ring (E83A or Y84A in loop 4 between the β3 sheet and α4 helix). Mutations that selectively disrupt hydrogen bonds between either the N3 nitrogen on the isoalloxanzine ring (i.e., E83) or the ribitylphos- phoate (i.e., S15) respectively result in 50% or 70% reductions in catalytic rates of chromate reduction. In comparison, mutations that disrupt π-π ring stacking interactions with the isoal-loxanzine ring (i.e., Y84) or a salt bridge with the ribityl phosphate result in 87% and 97% inhibittion. In all cases there are minimal alterations in chromate binding affinities. Collectively, these results support the hypothesis that chromate binds proximal to FMN, and implicate a structural role for FMN positioning for optimal chromate reduction rates. As side chains proximal to the β3/α4 FMN binding loop 4 contribute to both NADH and metal ion binding, we propose a model in which structural changes around the FMN binding pocket couples to both chromate and NADH binding sites.展开更多
A smart hybrid conversion coating has been developed. Modifications of coating solutions with poly-hydroxyl organic materials to reduce the usual mud cracking pattern characteristics of chromate conversion coatings (C...A smart hybrid conversion coating has been developed. Modifications of coating solutions with poly-hydroxyl organic materials to reduce the usual mud cracking pattern characteristics of chromate conversion coatings (CCCs) and improve its ability to release inhibitors to corroding sites have been achieved. The smart functionalised chromate conversion coating (SFCCC), developed on aluminium substrate has undergone laboratory checks and commercial runs under factory conditions confirmed its potency in improving corrosion resistance and paint adhesion to metal surfaces. In-service performance of the coating in the past three years is excellent.展开更多
In order to discover genes capable of catalyzing the reductive immobilization of toxic chromate and uranyl ions, we have created a T7 bacteriophage library containing cDNA from environmental microbes (i.e., Geobacter ...In order to discover genes capable of catalyzing the reductive immobilization of toxic chromate and uranyl ions, we have created a T7 bacteriophage library containing cDNA from environmental microbes (i.e., Geobacter sulfurreducens and Shewanella oneidensis MR-1) that are known to mediate the reduction of chromate and uranyl ions. After three rounds of screening, ten bacteriophage mutants were found to mediate the NADH-dependent reduction of chromate and uranyl ions whose cDNA encodes polypeptide chains ranging 14 to 73 amino acids in length. All identified sequences contain disordered structural motifs similar to the β-amyloid peptide (Aβ) known to promote aggregation and formation of high-affinity metal binding sites. Confirmation of this structural similarity involved phage display of the 42 amino-acid Aβ-peptides that have been found to catalyze the NADH-dependent reduction of both chromate and uranyl ions. Transmission electron microscopy (TEM) and X-ray absorption near edge structure (XANES) measurements confirm that reduced uranium is present on the surface of bacteriophage expressing the Aβ-peptide. The surface-displayed Aβ-like peptide on bacteriophage has the potential to couple naturally occurring electron transfer shuttles present in soils to promote economically viable remediation of contaminated sites containing toxic chromate and uranyl ions.展开更多
A new rapid method for the analysis of chromate ion in water by using high performance capillary electrophoresis is described. The detection limit is 1 .0 μg/ml by using 100 m mol/1 Tris-HCI buffer containing 2 m mol...A new rapid method for the analysis of chromate ion in water by using high performance capillary electrophoresis is described. The detection limit is 1 .0 μg/ml by using 100 m mol/1 Tris-HCI buffer containing 2 m mol/l 1,6-hexanediamine which was used as an electroosmosis modifier to improve the separation and detection sensitivity.展开更多
A solution containing Cr(VI), Cr(NO3)3 and its complex with an organic acid as well as several commercial solutions containing Cr(III) complexes with an organic acid and additionally CO2+, F-, SO42- ions were used for...A solution containing Cr(VI), Cr(NO3)3 and its complex with an organic acid as well as several commercial solutions containing Cr(III) complexes with an organic acid and additionally CO2+, F-, SO42- ions were used for the studies. Results of the studies obtained in the following commercial solutions: Likonda 2AT, Cr(NO3)3 + malonic acid;Likonda 3Cr5 and Likonda 3CrMC are discussed. Steel coated with chromated Zn coatings was contaminated by some microscopic fungi. The variety of fungi on chromated plates diminished, however the propagules of fungi did not disappear completely. The Likonda 3Cr5 solution diminishes fungi contamination on chromated steel most effectively. In water used to rinse the surface of chromated plates the number of fungi propagules was detected to be higher as compared to that on the plate surface. The least quantity of fungi propagules was detected in water used to rinse plates coated in the Likonda 3Cr5 solution. The main part of fungi detected on chromated plates treated in the Likonda 3Cr5 solution were the fungi of Cladosporium species (C.herbarum, C.cladosporioides). The latter species also dominated on chromated plates coated with zinc and treated with the other solution. It should be mentioned, that on these plates chromated in this solution, Actinomycetes of the Streptomyces group were abundant. After comparison of surfaces of the plates treated in four solutions it has been determined that the surface of the plates treated in the Likonda 3Cr5 passivation solution and exposed to modelling conditions changed least of all. It has been noticed that on the subject studied white porous rust accumulates, the intensity of this process on the surface studied determines both the probability of corrosion and the resistance of the used safety means to the external factors.展开更多
A new paradigm to remove toxic chromate anions from aqueous solution by crystallization of chromatewater clusters with imine-linked guanidinium cationic ligands is introduced.The guanidium-based cationic ligand was ea...A new paradigm to remove toxic chromate anions from aqueous solution by crystallization of chromatewater clusters with imine-linked guanidinium cationic ligands is introduced.The guanidium-based cationic ligand was easily prepared through the imine condensation of an alde hyde and aminoguanidine hydrochloride.The cationic imine-linked guanidinium liga nd(BBIG-CI)showed a high re moval capacity(292.5 mg/g)in the solutions.Rapid decontamination of chromate anions from the wastewater by this cationic ligand was resulted from an instantaneous crystallization.The produced guanidium chromate salts have an extremely low solubility(Ksp,BBIG=8.19×10^9).Such superior removal performance of these mate rials was attributed to the cha rge-assisted hydrogen bonding between the cationic ligand and chromate-water hydrate anions,which was revealed by the single-crystal X-ray diffraction analysis and density functional theory(DFT)calculations.In addition,the succes s ful recove ry of the guanidium-based ligand makes it more attractive for real-world applications.展开更多
The purpose of this study is to estimate the removal efficiency of As and Cr(VI)by one kind of industrial waste–iron chips,as well as to estimate the effects of typical inorganic anions(sulfate,phosphate,and nitrate)...The purpose of this study is to estimate the removal efficiency of As and Cr(VI)by one kind of industrial waste–iron chips,as well as to estimate the effects of typical inorganic anions(sulfate,phosphate,and nitrate),and typical organic anions(citrate,oxalate,and humate)on As or Cr(VI)removal.The results showed that 98%of As(V)and 92%of As(III)could be removed from aqueous phase by the iron chips within 60 min.Compared with As species,Cr(VI)was removed much more rapidly and efficiently with 97%of Cr(VI)being removed within 25 min.The removal efficiency for arsenic was in the order:As(III)(sulfate),As(III)(nitrate)or As(III),As(III)(humate),As(III)(oxalate),As(III)(citrate),As(III)(phosphate),and for chromate was in the order:Cr(VI)(sulfate),Cr(VI)(phosphate)or Cr(VI)(nitrate)or Cr(VI)(oxalate),Cr(VI),Cr(VI)(citrate),Cr(VI)(humate).In all the treatments,pH level increased with time except for As(III),the removal of which was either without anions or in the presence of humate or nitrate.展开更多
Hydrocalumite, a calcium aluminate hydrate phase, consists of positively-charged structure units, and is therefore an ideal candidate for accommodating anionic contaminants. In this study, a series of batch experiment...Hydrocalumite, a calcium aluminate hydrate phase, consists of positively-charged structure units, and is therefore an ideal candidate for accommodating anionic contaminants. In this study, a series of batch experiments was carried out to examine the uptake of chromate and selenate by hydrocalumite. To determine the uptake capacity and long-term stability, hydrocalumite solid solutions between chromate/selenate and hydroxyl were synthesized over a reaction time of more than one year. At a ratio of water to initial solids added (CaAl2O4+CaO) of 75: 1, the maximum uptake capacities were over 77 and 114 g/kg for Cr and Se, respectively.These values are very close to the theoretical uptake capacities of chromate and selenate hydrocalumite end-members (81 and 118 g/kg, respectively). The oxyanion removal efficiency from solution was above 95%. Due to the high uptake capacity and anion removal efficiency of hydrocalumites, their application in wastewater treatment is promising. Hydrocalumites are also important hydration products of cementitious materials and the long-term stability of these phases is of significance for application in solidification/stabilization technology.展开更多
An edge coloring of hypergraph H is a function such that holds for any pair of intersecting edges . The minimum number of colors in edge colorings of H is called the chromatic index of H and is ...An edge coloring of hypergraph H is a function such that holds for any pair of intersecting edges . The minimum number of colors in edge colorings of H is called the chromatic index of H and is denoted by . Erdös, Faber and Lovász proposed a famous conjecture that holds for any loopless linear hypergraph H with n vertices. In this paper, we show that is true for gap-restricted hypergraphs. Our result extends a result of Alesandroni in 2021.展开更多
Metalenses,which may effectively manipulate the wavefront of incident light,have been proposed and extensively utilized in the development of various planar optical devices for specialized purposes.However,similar to ...Metalenses,which may effectively manipulate the wavefront of incident light,have been proposed and extensively utilized in the development of various planar optical devices for specialized purposes.However,similar to traditional lenses,the metalens suffers from chromatic aberration problems due to the significant phase dispersion in each unit structure and the limited operational bandwidth.To mitigate the impact of chromatic aberration,we integrate a phase compensation approach with a novel utilization of a phase shift function to define the adjusted phase criterion satisfied by each α-Si resonance unit.This approach may lead to development of an innovative optical tweezer known as an achromatic optical vortex metalens(AOVM),offering reliable focusing capabilities across the 1300 nm and 1600 nm incident light range.Numerical simulations are conducted to investigate the optical properties of 200 nm diameter SiO_(2) particles at the focal plane of the AOVM.The trapping ability of the AOVM is successfully validated,exhibiting favorable characteristics including constant optical force,stable kinematic state of trapped particles,and consistent capture positions,surpassing those of the optical vortex metalens.展开更多
Metasurface-based polarimetry techniques have attracted lots of interests and been extensively studied in the past years,but are still hampered by narrow operating bandwidth and large crosstalk.Recently,Xian-Gang Luo&...Metasurface-based polarimetry techniques have attracted lots of interests and been extensively studied in the past years,but are still hampered by narrow operating bandwidth and large crosstalk.Recently,Xian-Gang Luo's group proposed a new method of polarization-dependent phase optimization for the design of crosstalk-free,broadband achromatic,and full Stokes imaging polarimeter,which offers a promising platform for a wide range of applications including bio-photonics and integrated optics.展开更多
Adaptive mate choice has been accepted as the leading theory to explain the colorful plumage of birds.This theory hypothesizes that conspicuous colors act as signals to advertise the qualities of the owners.However,a ...Adaptive mate choice has been accepted as the leading theory to explain the colorful plumage of birds.This theory hypothesizes that conspicuous colors act as signals to advertise the qualities of the owners.However,a dilemma arises in that conspicuous colors may not only attract mates,but also alert predators.The"private channels of communication"hypothesis proposes that some intraspecific signals may not be visible to heterospecific animals because of different visual systems.To better understand the evolution of plumage colors and sexual selection in birds,here we studied the chromatic difference and achromatic differences of melanin-and carotenoid-based plumage coloration in five minivet species(Pericrocotus spp.)under conspecific and predator visual systems.We found that either the chromatic or achromatic difference among male or female minivets’plumage was consistently higher under conspecific vision than under predator vision for all five studied species of minivets.This result indicated that individual differences in plumage colors of minivets were visible to the conspecific receivers and hidden from potential predators as a result of evolution under predation risk and conspecific communication.However,males were under a higher risk of predation because they were more conspicuous than females to the vision of a nocturnal predator.展开更多
The visible-light imaging system used in military equipment is often subjected to severe weather conditions, such as fog, haze, and smoke, under complex lighting conditions at night that significantly degrade the acqu...The visible-light imaging system used in military equipment is often subjected to severe weather conditions, such as fog, haze, and smoke, under complex lighting conditions at night that significantly degrade the acquired images. Currently available image defogging methods are mostly suitable for environments with natural light in the daytime, but the clarity of images captured under complex lighting conditions and spatial changes in the presence of fog at night is not satisfactory. This study proposes an algorithm to remove night fog from single images based on an analysis of the statistical characteristics of images in scenes involving night fog. Color channel transfer is designed to compensate for the high attenuation channel of foggy images acquired at night. The distribution of transmittance is estimated by the deep convolutional network DehazeNet, and the spatial variation of atmospheric light is estimated in a point-by-point manner according to the maximum reflection prior to recover the clear image. The results of experiments show that the proposed method can compensate for the high attenuation channel of foggy images at night, remove the effect of glow from a multi-color and non-uniform ambient source of light, and improve the adaptability and visual effect of the removal of night fog from images compared with the conventional method.展开更多
文摘AIM: To compare n-butyl-2-cyanoacrylate, iso-amyl-2-cyanoacrylate and a mixture of 72% chromated glycerin with hypertonic glucose solution in management of gastric varices. METHODS: Ninety patients with gastric varices presented to Endoscopy Unit of Ain Shams University Hospital were included. They were randomly allocated into three groups; each group included 30 patients treated with intravariceal sclerosant injections in biweekly sessions till complete obturation of gastric varices; Group I(n-butyl-2-cyanoacrylate; Histoacryl), Group II(iso-amyl-2-cyanoacrylate; Amcrylate) and Group III(mixture of 72% chromated glycerin; Scleremo with glucose solution 25%). All the procedures were performed electively without active bleeding. Recruited patients were followed up for 3 mo. RESULTS: 26% of Scleremo group had bleeding during puncture vs 3.3% in each of the other two groups with significant difference,(P < 0.05). None of Scleremo group had needle obstruction vs 13.3% in each of the other two groups with no significant difference,(P > 0.05). Rebleeding occurred in 13.3% of Histoacryl and Amcrylate groups vs 0% in Scleremo group with no significant difference. The in hospital mortality was 6.6% in both Histoacryl and Amcrylate groups, while it was 0% in Scleremo group with no significant difference. In the first and second sessions, the amount of Scleremo needed for obturation was significantly high, while the amount of Histoacryl was significantly low. Scleremo was the less costly of the two treatments. CONCLUSION: All used sclerosant substances showed efficacy and success in management of gastric varices with no significant differences except in total amount, cost and bleeding during puncture.
文摘A no pollution organic acid based conversion coating solution MIS. No.1 has been examined as to its suitability as possible replacement for chromate containing formulations on magnesium alloys. Investigations have concentrated on the formation of passive film from simple MIS. No.1 solution using immersion. The morphology of passivated surfaces was examined using scanning electron microscopy (SEM). The corrosion resistance of the passivated surfaces and the painted surface was assessed using electrochemical techniques as well as humidity and salt fog tests. It was concluded that the surface treatment magnesium alloy by MIS.No.1 solution is more effective than that by chromate coating treatment, and the MIS.No.1 coating is also suitable for painting’s pretreatment.
文摘Arthrobacter sp. SUK 1205 isolated from metalliferous chromite mine environment of Orissa, India showed wide degree of tolerance to heavy metals including Cr(VI), variety of antibiotics and was also capable of reducing Cr(VI) during growth. Freshly grown whole cells of this bacterium were evaluated for chromate reduction under batch culture using Vogel Bonner (V. B.) broth as the base. Cells of SUK 1205 were capable of completely reducing 100 μM Cr(VI) in V. B. broth within 48 h of incubation. Reduction of chromate increased with increase in cell density which attained maximum at 1010 cells/ml, however, reverse was the phenomenon when the concentration of Cr(VI) increased gradually. Glycerol, glycine and glucose promoted chromate reduction efficiency of the cells when used as electron donors. Optimum pH and temperature were found to be 7.0 and 35°C respectively. The process of reduction was inhibited by Ni(II), Mn(II), Zn(II) and Co(II), but Cu(II) and Fe(III) was promotive in nature. On the other hand, 2, 4-dinitrophenol was found to be neither promotive nor inhibitory for the reduction process, but carbonyl cyanide-m-chloro phenyl hydrazone, sodium azide, sodium fluoride and N,N,-dicyclohexyl carboiimide were inhibitory. Cells of SUK 1205 when permeabilized with toluene, triton X-100 and tween 80 showed an enhancement of the process and thereby indicated that reduction of Cr(VI) was mainly associated with soluble component of the cells. Arthrobacter sp. SUK 1205, therefore, showed great promise for use in Cr(VI) detoxification under a wide range of environmental conditions.
文摘The corrosion resistance of a low concentration chromate passive film for zinc based alloy coated steel wires was assessed by salt spray and electrochemical corrosion tests. XPS and AES analyses showed that the composition of such chromate passive film was S 5 5, Na 3 4, C 11 8, Ti 7 9, O 41 6, Cr 13 7, Zn 16 0.
文摘Over 2 million tons of chromate residues as hazardous wastes have been accumulated from chromate production processes during the past more than 30 years in China. Some serious pollution problems have been caused due to no appropriate technology and management. Approaches are reviewed to pollution control of chromate residues by utilizing them as secondary resources in this paper. In addition to legislation for pollution control, chromate residues can be used as raw materials to produce a great diversity of useful industrial products. Strategies are also recommanded for the resourcefulization of chromate residues.
文摘Sodium chromate solubility is determined in the range of NaOH concentrations from 450 to 810 g/L andsolution temperatUres from 30 to 110℃. The optimized conditions to separate sodium chromate from NaOH inleached solution are resolved. It is first found the method to efficiently separate sbdium chromate from NaOH andsodium altuninate in crude sodium chromate. Bench-scale studies on the separating are performed. Finally, goodseparation results are achieved.
基金supported by the Coal Seam Gas Joint Foundation of Shanxi(2015012016)Shanxi Province Science Foundation(2016011025)+2 种基金Shanxi Scholarship Council of China(2016-010)Shanxi “1331 Project” Key Innovative Research Team(“1331KIRT”)the Open Funding from State Key Laboratory of Materialoriented Chemical Engineering(No.KL16-03)
文摘Ni-based anodes of SOFCs are susceptible to coking, which greatly limits practical application of direct methane-based fuels. An indirect internal reformer is an effective way to convert methane-based fuels into syngas before they reach anode. In this work, catalytic activity of a redox-stable perovskite La0.7Sr0.3Cr0.8Fe0.2O3-δ(LSCrFO) for methane conversion was evaluated. The catalyst was fabricated as an anodic protective layer to improve coking resistance of a Ni cermet anode. Using wet CH4 as a fuel, the LSCrFO-modified cell showed excellent power output and good coking resistance with peak power density of 1.59 W cm-2 at 800℃. The cell demonstrated good durability lasting for at least 100 h. While the bare cell without the protective layer showed poor durability with the cell voltage fast dropped from 0.75 V to 0.4 V within 30 min. Under wet coal bed methane (CBM) operation, obvious performance degradation within 35 h (1.7 mV h^-1) was observed due to the influence of heavy carbon compounds in CBM. The pre-and post-mortem microstructures and carbon analysis of the anode surface and catalyst surface were further conducted.
文摘A putative chromate ion binding site was identified proximal to a rigidly bound FMN from electron densities in the crystal structure of the quinone reductase from Gluconacetobacter hansenii (Gh-ChrR) (3s2y.pdb). To clarify the location of the chromate binding site, and to understand the role of FMN in the NADPH-dependent reduction of chromate, we have expressed and purified four mutant enzymes involving the site-specific substitution of individual side chains within the FMN binding pocket that form non-covalent bonds with the ribityl phosphate (i.e., S15A and R17A in loop 1 between β1 sheet and α1 helix) or the isoalloxanzine ring (E83A or Y84A in loop 4 between the β3 sheet and α4 helix). Mutations that selectively disrupt hydrogen bonds between either the N3 nitrogen on the isoalloxanzine ring (i.e., E83) or the ribitylphos- phoate (i.e., S15) respectively result in 50% or 70% reductions in catalytic rates of chromate reduction. In comparison, mutations that disrupt π-π ring stacking interactions with the isoal-loxanzine ring (i.e., Y84) or a salt bridge with the ribityl phosphate result in 87% and 97% inhibittion. In all cases there are minimal alterations in chromate binding affinities. Collectively, these results support the hypothesis that chromate binds proximal to FMN, and implicate a structural role for FMN positioning for optimal chromate reduction rates. As side chains proximal to the β3/α4 FMN binding loop 4 contribute to both NADH and metal ion binding, we propose a model in which structural changes around the FMN binding pocket couples to both chromate and NADH binding sites.
文摘A smart hybrid conversion coating has been developed. Modifications of coating solutions with poly-hydroxyl organic materials to reduce the usual mud cracking pattern characteristics of chromate conversion coatings (CCCs) and improve its ability to release inhibitors to corroding sites have been achieved. The smart functionalised chromate conversion coating (SFCCC), developed on aluminium substrate has undergone laboratory checks and commercial runs under factory conditions confirmed its potency in improving corrosion resistance and paint adhesion to metal surfaces. In-service performance of the coating in the past three years is excellent.
文摘In order to discover genes capable of catalyzing the reductive immobilization of toxic chromate and uranyl ions, we have created a T7 bacteriophage library containing cDNA from environmental microbes (i.e., Geobacter sulfurreducens and Shewanella oneidensis MR-1) that are known to mediate the reduction of chromate and uranyl ions. After three rounds of screening, ten bacteriophage mutants were found to mediate the NADH-dependent reduction of chromate and uranyl ions whose cDNA encodes polypeptide chains ranging 14 to 73 amino acids in length. All identified sequences contain disordered structural motifs similar to the β-amyloid peptide (Aβ) known to promote aggregation and formation of high-affinity metal binding sites. Confirmation of this structural similarity involved phage display of the 42 amino-acid Aβ-peptides that have been found to catalyze the NADH-dependent reduction of both chromate and uranyl ions. Transmission electron microscopy (TEM) and X-ray absorption near edge structure (XANES) measurements confirm that reduced uranium is present on the surface of bacteriophage expressing the Aβ-peptide. The surface-displayed Aβ-like peptide on bacteriophage has the potential to couple naturally occurring electron transfer shuttles present in soils to promote economically viable remediation of contaminated sites containing toxic chromate and uranyl ions.
文摘A new rapid method for the analysis of chromate ion in water by using high performance capillary electrophoresis is described. The detection limit is 1 .0 μg/ml by using 100 m mol/1 Tris-HCI buffer containing 2 m mol/l 1,6-hexanediamine which was used as an electroosmosis modifier to improve the separation and detection sensitivity.
文摘A solution containing Cr(VI), Cr(NO3)3 and its complex with an organic acid as well as several commercial solutions containing Cr(III) complexes with an organic acid and additionally CO2+, F-, SO42- ions were used for the studies. Results of the studies obtained in the following commercial solutions: Likonda 2AT, Cr(NO3)3 + malonic acid;Likonda 3Cr5 and Likonda 3CrMC are discussed. Steel coated with chromated Zn coatings was contaminated by some microscopic fungi. The variety of fungi on chromated plates diminished, however the propagules of fungi did not disappear completely. The Likonda 3Cr5 solution diminishes fungi contamination on chromated steel most effectively. In water used to rinse the surface of chromated plates the number of fungi propagules was detected to be higher as compared to that on the plate surface. The least quantity of fungi propagules was detected in water used to rinse plates coated in the Likonda 3Cr5 solution. The main part of fungi detected on chromated plates treated in the Likonda 3Cr5 solution were the fungi of Cladosporium species (C.herbarum, C.cladosporioides). The latter species also dominated on chromated plates coated with zinc and treated with the other solution. It should be mentioned, that on these plates chromated in this solution, Actinomycetes of the Streptomyces group were abundant. After comparison of surfaces of the plates treated in four solutions it has been determined that the surface of the plates treated in the Likonda 3Cr5 passivation solution and exposed to modelling conditions changed least of all. It has been noticed that on the subject studied white porous rust accumulates, the intensity of this process on the surface studied determines both the probability of corrosion and the resistance of the used safety means to the external factors.
基金the National Natural Science Foundation of China(Nos.21790374,21825601,U1732112,21876124)the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)the Fundamental Research Funds for the Central Universities(No.2019QNA4047)。
文摘A new paradigm to remove toxic chromate anions from aqueous solution by crystallization of chromatewater clusters with imine-linked guanidinium cationic ligands is introduced.The guanidium-based cationic ligand was easily prepared through the imine condensation of an alde hyde and aminoguanidine hydrochloride.The cationic imine-linked guanidinium liga nd(BBIG-CI)showed a high re moval capacity(292.5 mg/g)in the solutions.Rapid decontamination of chromate anions from the wastewater by this cationic ligand was resulted from an instantaneous crystallization.The produced guanidium chromate salts have an extremely low solubility(Ksp,BBIG=8.19×10^9).Such superior removal performance of these mate rials was attributed to the cha rge-assisted hydrogen bonding between the cationic ligand and chromate-water hydrate anions,which was revealed by the single-crystal X-ray diffraction analysis and density functional theory(DFT)calculations.In addition,the succes s ful recove ry of the guanidium-based ligand makes it more attractive for real-world applications.
基金This paper was supported by Asian Institute at Nankai University,Tianjin,China.
文摘The purpose of this study is to estimate the removal efficiency of As and Cr(VI)by one kind of industrial waste–iron chips,as well as to estimate the effects of typical inorganic anions(sulfate,phosphate,and nitrate),and typical organic anions(citrate,oxalate,and humate)on As or Cr(VI)removal.The results showed that 98%of As(V)and 92%of As(III)could be removed from aqueous phase by the iron chips within 60 min.Compared with As species,Cr(VI)was removed much more rapidly and efficiently with 97%of Cr(VI)being removed within 25 min.The removal efficiency for arsenic was in the order:As(III)(sulfate),As(III)(nitrate)or As(III),As(III)(humate),As(III)(oxalate),As(III)(citrate),As(III)(phosphate),and for chromate was in the order:Cr(VI)(sulfate),Cr(VI)(phosphate)or Cr(VI)(nitrate)or Cr(VI)(oxalate),Cr(VI),Cr(VI)(citrate),Cr(VI)(humate).In all the treatments,pH level increased with time except for As(III),the removal of which was either without anions or in the presence of humate or nitrate.
文摘Hydrocalumite, a calcium aluminate hydrate phase, consists of positively-charged structure units, and is therefore an ideal candidate for accommodating anionic contaminants. In this study, a series of batch experiments was carried out to examine the uptake of chromate and selenate by hydrocalumite. To determine the uptake capacity and long-term stability, hydrocalumite solid solutions between chromate/selenate and hydroxyl were synthesized over a reaction time of more than one year. At a ratio of water to initial solids added (CaAl2O4+CaO) of 75: 1, the maximum uptake capacities were over 77 and 114 g/kg for Cr and Se, respectively.These values are very close to the theoretical uptake capacities of chromate and selenate hydrocalumite end-members (81 and 118 g/kg, respectively). The oxyanion removal efficiency from solution was above 95%. Due to the high uptake capacity and anion removal efficiency of hydrocalumites, their application in wastewater treatment is promising. Hydrocalumites are also important hydration products of cementitious materials and the long-term stability of these phases is of significance for application in solidification/stabilization technology.
文摘An edge coloring of hypergraph H is a function such that holds for any pair of intersecting edges . The minimum number of colors in edge colorings of H is called the chromatic index of H and is denoted by . Erdös, Faber and Lovász proposed a famous conjecture that holds for any loopless linear hypergraph H with n vertices. In this paper, we show that is true for gap-restricted hypergraphs. Our result extends a result of Alesandroni in 2021.
基金supported by the National Natural Science Foundation of China(Grant Nos.62275269,60907003,61805278,61875168,and 22134005)the Chongqing Talents Program for Outstanding Scientists(Grant No.cstc2021ycjh-bgzxm0178)。
文摘Metalenses,which may effectively manipulate the wavefront of incident light,have been proposed and extensively utilized in the development of various planar optical devices for specialized purposes.However,similar to traditional lenses,the metalens suffers from chromatic aberration problems due to the significant phase dispersion in each unit structure and the limited operational bandwidth.To mitigate the impact of chromatic aberration,we integrate a phase compensation approach with a novel utilization of a phase shift function to define the adjusted phase criterion satisfied by each α-Si resonance unit.This approach may lead to development of an innovative optical tweezer known as an achromatic optical vortex metalens(AOVM),offering reliable focusing capabilities across the 1300 nm and 1600 nm incident light range.Numerical simulations are conducted to investigate the optical properties of 200 nm diameter SiO_(2) particles at the focal plane of the AOVM.The trapping ability of the AOVM is successfully validated,exhibiting favorable characteristics including constant optical force,stable kinematic state of trapped particles,and consistent capture positions,surpassing those of the optical vortex metalens.
文摘Metasurface-based polarimetry techniques have attracted lots of interests and been extensively studied in the past years,but are still hampered by narrow operating bandwidth and large crosstalk.Recently,Xian-Gang Luo's group proposed a new method of polarization-dependent phase optimization for the design of crosstalk-free,broadband achromatic,and full Stokes imaging polarimeter,which offers a promising platform for a wide range of applications including bio-photonics and integrated optics.
基金supported by the National Natural Science Foundation of China(32260127)the Education Department of Hainan Province(HnjgY2022-12)+1 种基金the Hainan Provincial Natural Science Foundation of China(320CXTD437)the Hainan Provincial Innovative Research Program for Graduates(Qhys2022-241)。
文摘Adaptive mate choice has been accepted as the leading theory to explain the colorful plumage of birds.This theory hypothesizes that conspicuous colors act as signals to advertise the qualities of the owners.However,a dilemma arises in that conspicuous colors may not only attract mates,but also alert predators.The"private channels of communication"hypothesis proposes that some intraspecific signals may not be visible to heterospecific animals because of different visual systems.To better understand the evolution of plumage colors and sexual selection in birds,here we studied the chromatic difference and achromatic differences of melanin-and carotenoid-based plumage coloration in five minivet species(Pericrocotus spp.)under conspecific and predator visual systems.We found that either the chromatic or achromatic difference among male or female minivets’plumage was consistently higher under conspecific vision than under predator vision for all five studied species of minivets.This result indicated that individual differences in plumage colors of minivets were visible to the conspecific receivers and hidden from potential predators as a result of evolution under predation risk and conspecific communication.However,males were under a higher risk of predation because they were more conspicuous than females to the vision of a nocturnal predator.
基金supported by a grant from the Qian Xuesen Laboratory of Space Technology, China Academy of Space Technology (Grant No. GZZKFJJ2020004)the National Natural Science Foundation of China (Grant Nos. 61875013 and 61827814)the Natural Science Foundation of Beijing Municipality (Grant No. Z190018)。
文摘The visible-light imaging system used in military equipment is often subjected to severe weather conditions, such as fog, haze, and smoke, under complex lighting conditions at night that significantly degrade the acquired images. Currently available image defogging methods are mostly suitable for environments with natural light in the daytime, but the clarity of images captured under complex lighting conditions and spatial changes in the presence of fog at night is not satisfactory. This study proposes an algorithm to remove night fog from single images based on an analysis of the statistical characteristics of images in scenes involving night fog. Color channel transfer is designed to compensate for the high attenuation channel of foggy images acquired at night. The distribution of transmittance is estimated by the deep convolutional network DehazeNet, and the spatial variation of atmospheric light is estimated in a point-by-point manner according to the maximum reflection prior to recover the clear image. The results of experiments show that the proposed method can compensate for the high attenuation channel of foggy images at night, remove the effect of glow from a multi-color and non-uniform ambient source of light, and improve the adaptability and visual effect of the removal of night fog from images compared with the conventional method.
