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1.
Seda Keskin 《Molecular simulation》2013,39(1):14-24
Grand canonical Monte Carlo and equilibrium molecular dynamics simulations were used to assess the performance of an rht-type metal–organic framework (MOF), Cu-TDPAT, in adsorption-based and membrane-based separation of CH4/H2, CO2/CH4 and CO2/H2 mixtures. Adsorption isotherms and self-diffusivities of pure gases and binary gas mixtures in Cu-TDPAT were computed using detailed molecular simulations. Several properties of Cu-TDPAT such as adsorption selectivity, working capacity, diffusion selectivity, gas permeability and permeation selectivity were computed and compared with well-known zeolites and MOFs. Results showed that Cu-TDPAT is a very promising adsorbent and membrane material especially for separation of CO2 and it can outperform traditional zeolites and MOFs such as DDR, MFI, CuBTC, IRMOF-1 in adsorption-based CO2/CH4 and CO2/H2 separations. 相似文献
2.
U. Casellato D. Fregona S. Sitran S. Tamburini P. A. Vigato 《Inorganica chimica acta》1985,110(3):181-190
A new heptadentate compartmental ligand has been synthesized by condensation of 3-formylsalicylic acid and 1,5-diamino-3-thiapentane in methanol (H4La). This Schiff base contains an inner N2SO2 and an outer O2O2 site and gives, by reaction with copper(II), nickel(II) and uranyl(VI) diacetate, mononuclear, homo- and heterobinuclear complexes. In the mononuclear copper and nickel complexes, the metal ion is in the inner N2SO2 site, while it is in the outer O2O2 for uranyl; a solvent molecule fills the fifth equatorial coordination position in this last complex. The physico-chemical properties of the compounds are discusscd on the basis of infrared, electronic and magnetic data and by comparison with the analogous complexes with the ligand obtained by reaction of 3- formylsalicylic acid and diethylenetriamine (H4Lb). The mononuclear copper and the heterodinuclear copper-uranyl complexes show anomalously low magnetic moments. 相似文献
3.
U. Casellato D. Fregona S. Sitran S. Tamburini P.A. Vigato 《Inorganica chimica acta》1985,110(3):161-167
A new heptadentate compartmental ligand has been synthesized by condensation of 3-formylsalicylic acid and 1,5-diamino-3-thiapentane in methanol (H4La). This Schiff base contains an inner N2SO2 and an outer O2O2 site and gives, by reaction with copper(II), nickel(II) and uranyl(VI) diacetate, mononuclear, homo- and heterobinuclear complexes. In the mononuclear copper and nickel complexes, the metal ion is in the inner N2SO2 site, while it is in the outer O2O2 for uranyl; a solvent molecule fills the fifth equatorial coordination position in this last complex. The physico-chemical properties of the compounds are discusscd on the basis of infrared, electronic and magnetic data and by comparison with the analogous complexes with the ligand obtained by reaction of 3- formylsalicylic acid and diethylenetriamine (H4Lb). The mononuclear copper and the heterodinuclear copper-uranyl complexes show anomalously low magnetic moments. 相似文献
4.
Many coastal plain wetlands receive nutrient pollution from agricultural fields and are particularly vulnerable to saltwater incursion. Although wetlands are a major source of the greenhouse gases methane (CH4) and nitrous oxide (N2O), the consequences of salinization for greenhouse gas emissions from wetlands with high agricultural pollution loads is rarely considered. Here, we asked how saltwater exposure alters greenhouse gas emissions from a restored freshwater wetland that receives nutrient loading from upstream farms. During March to November 2012, we measured greenhouse gases along a ~2 km inundated portion of the wetland. Sampling locations spanned a wide chemical gradient from sites receiving seasonal fertilizer nitrogen and sulfate (SO4 2?) loads to sites receiving seasonal increases in marine salts. Concentrations and fluxes of CH4 were low (<100 µg L?1 and <10 mg m?2 h?1) for all sites and sampling dates when SO4 2? was high (>10 mg L?1), regardless of whether the SO4 2? source was agriculture or saltwater. Elevated CH4 (as high as 1,500 µg L?1 and 45 mg m?2 h?1) was only observed on dates when air temperatures were >27 °C and SO4 2? was <10 mg L?1. Despite elevated ammonium (NH4 +) for saltwater exposed sites, concentrations of N2O remained low (<5 µg L?1 and <10 µg m?2 h?1), except when fertilizer derived nitrate (NO3 ?) concentrations were high and N2O increased as high as 156 µg L?1. Our results suggest that although both saltwater and agriculture derived SO4 2? may suppress CH4, increases in N2O associated with fertilizer derived NO3 ? may offset that reduction in wetlands exposed to both agricultural runoff and saltwater incursion. 相似文献
5.
Matthew D Jones 《Inorganica chimica acta》2004,357(11):3351-3359
The Schiff base 2,2′-bis((4S)-4-benzyl-2-oxazoline) (I) and its coordination complexes with rhodium(I) and palladium(II) (and with 1,5-cyclo-octadiene and allyl ligands) have been characterised by single-crystal X-ray diffraction, mass spectrometry, 13C and 1H NMR spectroscopy: [Rh(C20H20N2O2)(C8H12)][Rh2(C20H20N2O2)2](CF3SO3)3 · (CH3CH2O) (II) and [Pd(C20H20N2O2)(C3H5)]CF3SO3 (III). We discuss the reasons for the formation of two complex cations for Rh(I), [Rh(C20H20N2O2)(C8H12)]+ (IIa) and [Rh2(C20H20N2O2)2]2+ (IIb), and only one for Pd(II). 相似文献
6.
Four new platinum(II) complexes: PtII L1·H2O (C1, H2 L1 = C20H16N2O2), PtII L2Cl2 (C2, L2 = C22H16N2O2), PtII L3Cl2·H2O (C3, L3 = C20H16N2), PtII L4Cl2·0.4H2O (C4, L4 = C18H14N4) have been synthesized and characterized by using various physico-chemical techniques. The binding interaction of the four platinum(II) complexes C1–C4 with calf thymus (CT)-DNA has been investigated by UV–Vis and fluorescence emission spectrometry. The apparent binding constant (K app) values follow the order: C3 > C1 > C2 > C4. In addition, fluorescence spectrometry of bovine serum albumin (BSA) with the four platinum(II) complexes C1–C4 showed that the quenching mechanism might be a static quenching procedure. For C1–C4, the number of binding sites was about one for BSA and the binding constants follow the order: C3 (7.08 × 105M?1) > C1 (2.82 × 105M?1) > C2 (0.85 × 105M?1) > C4 (0.15 × 105M?1). With the single condition change such as absence of an external agent, the DNA cleavage abilities of C3 exhibit remarkable changes. In addition, the cytotoxicity of C3 in vitro on tumor cells lines (MCF-7, HepG2 and HT29) were examined by MTT and showed better antitumor effects on the tested cells. 相似文献
7.
In this study, the effect of H2O2-induced oxidative stress on gellan gum production and cell growth were investigated. Gellan gum production was improved and cell growth was inhibited by H2O2. A multiple H2O2 stresses with different concentrations were developed to optimize gellan gum production. A maximal gellan gum yield (22.52 g/L), which was 35.58 % higher than the control, was observed with 2, 2, 3, 4 mmol/L H2O2 added at 6, 12, 18, 24 h, respectively. Moreover, UDP-glucose pyrophosphorylase activity and glucosyltransferase activity were increased with H2O2 stresses. This new strategy of multiple H2O2-induced oxidative stresses would be further applied to gellan gum production in future study. 相似文献
8.
Wenmin Chen Peng Zhan Erik De Clercq Christophe Pannecouque Jan Balzarini Xin Jiang Xinyong Liu 《Bioorganic & medicinal chemistry》2013,21(22):7091-7100
A series of N2,N4-disubstituted-1,1,3-trioxo-2H,4H-pyrrolo[1,2-b][1,2,4,6]thiatriazine derivatives (PTTDs) was designed and synthesized by a facile route. The biological assay results showed that five most potent compounds displayed inhibitory activity against HIV-1 at low micromolar concentrations (EC50 = 5.1–8.9 μM). Structure–activity relationship analysis indicated that N2-(3-halogenated-benzyl) analogues were more potent than N2-(unsubstituted-benzyl) analogues. The N4-substitutions contributed to the antiviral activity in the following order: 2-/3-cyano substituted benzyl > 2-/3-halogenated benzyl > non-substituted benzyl > 4-halogenated benzyl. Docking studies of the representative compound revealed the binding conformation of these compounds and provided critical insights for the further development of PTTD analogues. 相似文献
9.
The aim of the present investigation was to verify the effect of H2O2-induced oxidative stress on SO4= uptake through Band 3 protein, responsible for Cl-/HCO3- as well as for cell membrane deformability, due to its cross link with cytoskeletal proteins. The role of cytoplasmic proteins binding to Band 3 protein has been also considered by assaying H2O2 effects on hemoglobin-free resealed ghosts of erythrocytes. Oxidative conditions were induced by 30 min exposure of human erythrocytes to different H2O2 concentrations (10 to 300 μM), with or without GSH (glutathione, 2 mM) or curcumin (10 μM), compounds with proved antioxidant properties. Since SO4= influx through Band 3 protein is slower and better controllable than Cl- or HCO3- exchange, the rate constant for SO4= uptake was measured to prove anion transport efficiency, while MDA (malondialdehyde) levels and –SH groups were estimated to quantify the effect of oxidative stress. H2O2 induced a significant decrease in rate constant for SO4= uptake at both 100 and 300 μM H2O2. This reduction, observed in erythrocytes but not in resealed ghosts and associated to increase in neither MDA levels nor in –SH groups, was impaired by both curcumin and GSH, whereas only curcumin effectively restored H2O2-induced changes in erythrocytes shape. Our results show that: i) 30 min exposure to 300 μM H2O2 reduced SO4= uptake in human erythrocytes; ii) oxidative damage was revealed by the reduction in rate constant for SO4= uptake, but not by MDA or –SH groups levels; iii) the damage was produced via cytoplasmic components which cross link with Band 3 protein; iv) the natural antioxidant curcumin may be useful in protecting erythrocytes from oxidative injury; v) SO4= uptake through Band 3 protein may be reasonably suggested as a tool to monitor erythrocytes function under oxidative conditions possibly deriving from alcohol consumption, use of drugs, radiographic contrast media administration, hyperglicemia or neurodegenerative diseases. 相似文献
10.
Background
Pretreatment is a critical step in the conversion of lignocellulose to fermentable sugars. Although many pretreatment processes are currently under investigation, none of them are entirely satisfactory in regard to effectiveness, cost, or environmental impact. The use of hydrogen peroxide at pH 11.5 (alkaline hydrogen peroxide (AHP)) was shown by Gould and coworkers to be an effective pretreatment of grass stovers and other plant materials in the context of animal nutrition and ethanol production. Our earlier experiments indicated that AHP performed well when compared against two other alkaline pretreatments. Here, we explored several key parameters to test the potential of AHP for further improvement relevant to lignocellulosic ethanol production.Results
The effects of biomass loading, hydrogen peroxide loading, residence time, and pH control were tested in combination with subsequent digestion with a commercial enzyme preparation, optimized mixtures of four commercial enzymes, or optimized synthetic mixtures of pure enzymes. AHP pretreatment was performed at room temperature (23°C) and atmospheric pressure, and after AHP pretreatment the biomass was neutralized with HCl but not washed before enzyme digestion. Standard enzyme digestion conditions were 0.2% glucan loading, 15 mg protein/g glucan, and 48 h digestion at 50°C. Higher pretreatment biomass loadings (10% to 20%) gave higher monomeric glucose (Glc) and xylose (Xyl) yields than the 2% loading used in earlier studies. An H2O2 loading of 0.25 g/g biomass was almost as effective as 0.5 g/g, but 0.125 g/g was significantly less effective. Optimized mixtures of four commercial enzymes substantially increased post-AHP-pretreatment enzymatic hydrolysis yields at all H2O2 concentrations compared to any single commercial enzyme. At a pretreatment biomass loading of 10% and an H2O2 loading of 0.5 g/g biomass, an optimized commercial mixture at total protein loadings of 8 or 15 mg/g glucan gave monomeric Glc yields of 83% or 95%, respectively. Yields of Glc and Xyl after pretreatment at a low hydrogen peroxide loading (0.125 g H2O2/g biomass) could be improved by extending the pretreatment residence time to 48 h and readjusting the pH to 11.5 every 6 h during the pretreatment. A Glc yield of 77% was obtained using a pretreatment of 15% biomass loading, 0.125 g H2O2/g biomass, and 48 h with pH adjustment, followed by digestion with an optimized commercial enzyme mixture at an enzyme loading of 15 mg protein/g glucan.Conclusions
Alkaline peroxide is an effective pretreatment for corn stover. Particular advantages are the use of reagents with low environmental impact and avoidance of special reaction chambers. Reasonable yields of monomeric Glc can be obtained at an H2O2 concentration one-quarter of that used in previous AHP research. Additional improvements in the AHP process, such as peroxide stabilization, peroxide recycling, and improved pH control, could lead to further improvements in AHP pretreatment. 相似文献11.
We report a molecular simulation study for gas permeation in two membranes constructed from polymers of intrinsic microporosity (PIM-1 and PIM-7). With rigid ladder polymer chains, the membranes posses approximately 47.7 and 46.6% fractional free volumes (FFVs) in PIM-1 and PIM-7, respectively. The voids in the membranes have a diameter up to 9 Å and are largely interconnected. The sorption and diffusion of four gases (H2, O2, CH4 and CO2) were calculated by Monte Carlo and molecular dynamics simulations. The solubility coefficients increase in the order of H2 < O2 < CH4 < CO2, while the diffusion coefficients increase in the following order: CH4 < CO2 < O2 < H2. The simulation results agree well with experimental data, particularly for the solubility coefficients. The solubility and diffusion coefficients correlate well separately with the critical temperatures and effective diameters of gases. These molecular-based correlations can be used in the prediction for other gases. As attributed to the microporous structure, PIM-1 and PIM-7 outperform most glassy polymeric membranes in sorption and diffusion. PIM-1 has larger solubility and diffusion coefficients than PIM-7 because the cyano groups in PIM-1 lead to a stronger affinity and a larger FFV. The simulated solubility, diffusivity and permeation selectivities of CO2/H2, CO2/O2 and CO2/CH4 are consistent with experimental data. The quantitative microscopic understanding of gas permeation in the PIM membranes is useful for the new development of high-performance membranes. 相似文献
12.
Gero Benckiser 《Annals of microbiology》2007,57(4):509-514
Soil-N (NO3 ?) initiates as far as a threshold concentration is surpassed manifold physiological reactions on N2-fixation. Organic N and ammonium oxidised to NO3 ? means oxygen depletion. Plants suffering under O2 or infection stress start to excrete ethylene (C2H4). C2H4 widens the root intercellulars that O2-respiration will continue. Now microbes may more easily enter the plant interior by transforming the reached methionine into C2H4. Surplus nitrate and C2H4 inhibit nodulation of leguminous plants. Excess NO3 ? in the nodulesphere could be diminished by N2-fixing bacteria which in addition can denitrify or ammonify nitrate. Consequently, it was asked whether C2H4 interferes with the potential of N2-fixing bacteria to reduce nitrate. The groundnut-nodule isolate TNAU 14, from which it was known that it denitrifies and ammonifies nitrate, served as inoculum of a KNO3-mannitol-medium that was incubated under N2-, 1% (v/v) N2?C2H4-, and 1% (v/v) N2?C2H2-atmosphere in the laboratory. C2H2 was included into the experiments because it is frequently used to quantify N2-fixing potentials (acetylene reduction array, ARA). Gene-16S rDNA-sequencing and physiological tests revealed a high affiliation of strain TNAU 14 toRhizobium radiobacter andRhizobium tumefaciens. Strain TNAU 14 released N2O into the bottle headspace in all treatments, surprisingly significantly less in presence of C2H2. Nitrate-ammonification was even completely blocked by C2H2. C2H4, in contrast rather stimulated growth, denitrification, and nitrate-ammonification of strain TNAU 14 which consumed the released NH4 + during continuing incubation. 相似文献
13.
Keizo Uzu Yujiro Harada Shigetoshi Wakaki Yasuhiro Yamada 《Bioscience, biotechnology, and biochemistry》2013,77(6):388-402
Mitomycin A (C16H19O6N3) and mitomycin C (C15H18O5N4) are pigments which have the quinoid structure. When treated with aqueous ammonia, mitomycin A is converted to mitomycin C. Acid hydrolysis of mitomycin C gave three degradation products, namely, C14H15O5N4, C14H15O6N3 and C13H14O5N2. Acetylation with acetic anhydride and pyridine and methylation with methyl iodide gave monoacetyl and monomethyl derivatives of mitomycin C respectively, though diacetate of demethyl derivatives were obtained when boiled with acetic anhydride. 相似文献
14.
Evaluation of phosphorus in forest soils: Comparison of phosphorus uptake,extraction method and soil properties 总被引:1,自引:0,他引:1
Summary Phosphorus in soils from plantation of red pine (Pinus resinosa Ait.) was determined using six extractants: 0.002N H2SO4 (pH 3.0); 0.025N HCl+ +0.03N NH4F; 0.5N NaHCO3 (pH 8.5);N NH4OAc (pH 4.8); anion exchange resin (Dower –2, Cl-form); H2O. Correlations of extractable P with Al- and Al-+Fe-P indicated that these fractions are the dominant forms of inorganic P in most of the soils.Uptake of P by corn and Monterey pine seedlings grown in greenhouse culture was correlated with soil P extracted by the different methods. The most successful of the extractants for predicting P uptake was resin extractable P; the simple correlation coefficients were 0.811 and 0.609 for pine and corn respectively. P uptake by pine correlated significantly with 0.002N H2SO4 P (r=0.679),N NH4OAc P (r=0.443), H2O P (r=0.549) and Al-+Fe-P (r=0.532) while P uptake by corn correlated with 0.002N H2SO4 P (r=0.579), H2O P (r=0.477) and organic P (r=0.460). Per cent P in pine seedling tops correlated significantly with 0.002N H2SO4, resin andN NH4 OAc extractable P. Multiple regressions which included silt+clay and organic P improved correlations of some soil tests with P uptake in corn and pine seedlings respectively.Research supported by the School of Natural Resources, College of Agricultural and Life Sciences, Univ. of Wisconsin, Madison, the Wisconsin Department of Natural Resources and FAO Fellowship to the senior author. 相似文献
15.
A horizontal biotrickling filter (HBTF) was used to inoculate autotrophic sulfide-oxidizing and ammonia-oxidizing microbial
consortiums over H2S-exhausted carbon for co-treating H2S and NH3 waste gas in a long-term operation. In this study, several aspects (i.e., pH change, shock loading and starvation) of the
dynamic behavior of the HBTF were investigated. The metabolic products of N and S bearing species in recycling liquid and
biological activities of the biofilm were analyzed to explain the observed phenomena and further explore the fundamentals
behind. In the pH range of 4–8.5, although the removal efficiencies of H2S and NH3 remained 96–98% and 100%, respectively, the metabolic products demonstrated different removal mechanisms and pathways. NH4-N and NO2/NO3-N were dominated at pH ≤6 and ≥7, respectively, indicating the differentiated contributions from physical/chemical adsorption
and bio-oxidation. Moreover, the HBTF demonstrated a good dynamic stability to withstand shock loadings by recovering immediately
to the original. During shock loading, only 15.4% and 17.9% of captured H2S and NH3 was biodegraded, respectively. After 2, 11, and 48 days of starvation, the HBTF system reached a full performance within
reasonable re-startup times (2–80 h), possibly due to the consumption of reduced S and N species in biomass or activated carbon
thus converted into SO4-S and NO3-N during starvation period. The results helped to understand the fundamental knowledge by revealing the effects of pH and
transient loadings linked with individual removal mechanism for H2S and NH3 co-treatment in different conditions. 相似文献
16.
To accomplish the micro Kjeldahl digestion of cereal grains and other biological materials in approximately 10 minutes, two techniques were developed: (1) digestion in the presence of hydrogen peroxide, K2SO4HgOH2SO4 mixture, with lauric acid as anti-foaming agent, and (2) precarbonization of sample in K2SO4HgOH2SO4 mixture to produce foam-forming materials which are immediately destroyed by H2O2. Oxidation of the sample is enhanced by H2O2 and high digestion temperature resulting from increased salt-acid ratio. 相似文献
17.
A novel organic-inorganic hybrid pentaborate [Ni(C4H10N2)(C2H8N2)2][B5O6(OH)4]2 has been synthesized by hydrothermal reaction and characterized by FT-IR, Raman spectroscopy, elemental analyses and DTA-TGA. Its crystal structure was determined from single crystal X-ray diffraction. The structure consists of isolated polyborate anion [B5O6(OH)4]− and nickel complex cation of [Ni(C4H10N2)(C2H8N2)2]2+, in which the two kinds of ligands come from the decomposition of triethylenetriamine material. The [B5O6(OH)4]− units are connected to one another through hydrogen bonds, forming a three-dimensional framework with large channel along the a and c axes, in which the templating [Ni(C4H10N2)(C2H8N2)2]2+ cations are located. The assignments of the record FT-IR absorption frequencies and Raman shifts were given. 相似文献
18.
A. Saeed Bhatti 《Plant and Soil》1974,41(3):681-683
Summary Effects of H2SO4, H2O2, C2H5OH and of acetone on germination of cotton seeds and on the growth of seedling root were studied under laboratory conditions. H2SO4 or H2O2 hastened germination but decreased the ultimate number of seeds germinated. Higher temperature (27°C) hastened germination and increased the number of seeds germinated. Root length remained unaffected by treatments at room temperature while H2SO4 or H2SO4/H2O2 substantially decreased it at 27°C. 相似文献
19.
Nethika S. Suraweera Austin A. Albert Michael E. Peretich Joshua Abbott James R. Humble Craig E. Barnes 《Molecular simulation》2014,40(7-9):618-633
The adsorptive and diffusive behaviour of methane and carbon dioxide in amorphous nanoporous adsorbents composed of spherosilicate building blocks, in which isolated metal sites have been distributed, is examined. The adsorbent contains cubic silicate building blocks (spherosilicate units: Si8O20), which are cross linked by SiCl2O2 bridges and decorated with either –OTiCl3 or –OSiMe3 groups of the other cube corners. The model structures were generated to correspond to experimentally synthesised materials, matching physical properties including density, surface area and accessible volume. It is shown that both methane and carbon dioxide adsorb via physisorption only in the modelled materials. Adsorption isotherms and energies at 300 K for pressures up to 100 bar were generated via molecular simulation. The maximum gravimetric capacity of CH4 is 16.9 wt%, occurring at 300 K and 97 bar. The maximum gravimetric capacity of CO2 is 50.3 wt%, occurring at 300 K and 51.6 bar. The best performing adsorbent was a low-density (high accessible volume) material with no –OTiCl3 groups. The presence of –OTiCl3 did not enhance physisorption even on a volumetric basis, and the high molecular weight of –OTiCl3 groups is a significant penalty on a gravimetric basis. Based on the pair correlation functions, the most favourable adsorption sites for both adsorbates are located in front of the faces of spherosilicate cubes. The self-diffusivity and activation energy for diffusion are also reported. 相似文献
20.
Li Tan Zhaoyong Sun Wenxue Zhang Yueqin Tang Shigeru Morimura Kenji Kida 《Bioprocess and biosystems engineering》2014,37(10):2031-2038
Distilled grain waste eluted from Chinese spirit making is rich in carbohydrates, and could potentially serve as feedstock for the production of bio-fuel ethanol. Our study evaluated two types of saccharification methods that convert distilled grain waste to monosaccharides: enzymatic saccharification and concentrated H2SO4 saccharification. Results showed that enzymatic saccharification performed unsatisfactorily because of inefficient removal of lignin during pretreatment. Concentrated H2SO4 saccharification led to a total sugar recovery efficiency of 79.0 %, and to considerably higher sugar concentrations than enzymatic saccharification. The process of ethanol production from distilled grain waste based on concentrated H2SO4 saccharification was then studied. The process mainly consisted of concentrated H2SO4 saccharification, solid–liquid separation, decoloration, sugar–acid separation, oligosaccharide hydrolysis, and continuous ethanol fermentation. An improved simulated moving bed system was employed to separate sugars from acid after concentrated H2SO4 saccharification, by which 95.8 % of glucose and 85.8 % of xylose went into the sugar-rich fraction, while 83.3 % of H2SO4 went into the acid-rich fraction. A flocculating yeast strain, Saccharomyces cerevisiae KF-7, was used for continuous ethanol fermentation, which produced an ethanol yield of 91.9–98.9 %, based on glucose concentration. 相似文献