共查询到20条相似文献,搜索用时 15 毫秒
1.
Through a moderate ammonolysis method, nanobelts of α‐MoO 3 can be modified to H xMo(O, N) 3. When reaction temperatures are kept between 200–300 °C, gaseous NH 3 diffuses in‐between the oxide layers and reacts with terminal oxygen sites of MoO 3. As a consequence, hydrogen is introduced into the layers and bonded to terminal oxygen, and together with the effect of nitradation, the unit cell volume significantly shrinks mostly along the b axis. The modified compound H xMo(O, N) 3 exhibits not only better electronic conductivity, but also faster lithium ion mobility than regular MoO 3. In addition, this ammonolyzed MoO 3 exhibits enhanced electrochemical performance beyond MoO 3. In the potential window 1.5–3.5 V, the specific capacity of H xMo(O, N) 3 can reach more than 250 A h kg ?1 and was cycled 300 times without fading. It can be considered as a novel candidate cathode material with high specific charge for rechargeable Li‐ion batteries. 相似文献
3.
Mass spectral analysis of T-2 toxin formed during the growth of Fusarium sporotrichioides (ATCC 24043) in the presence of H 218O showed incorporation of up to three 18O atoms per toxin molecule. The carbonyl oxygens of the acetates at C-4 and C-15 and of the isovalerate at C-8 were derived from H 2O. Toxin formed in the presence of 18O molecular oxygen incorporated up to six 18O atoms per toxin molecule. The overall incorporation was 78 and 92% of toxin molecules labeled for H 218O and 18O 2 labeled samples, respectively. The oxygens of position 1, the 12,13-epoxide, and the hydroxyl groups at C-3, C-4, C-8, and C-15 were all derived from molecular oxygen. 相似文献
4.
The acid molecules H 2SO 3, H 2SO 4, and H 3PO 4 are usually drawn using "Lewis structures" which exhibit the octet extension by 3d-orbitals on sulfur and phosphorus, respectively. Thus, S=O and P=O double bonds are assumed to be formed. The natural d-orbital occupancies on S and P, however, were calculated to be as low as 0.1 e, and therefore, an octet extension can hardly be expected. After the natural bond orbitals (NBO) search procedure was forced to attempt to form different Lewis structures of bonds and lone pairs, we defined the optimal Lewis structure, if a dominant structure exists at all, by the maximum electronic charge in Lewis orbitals. Indeed, sulfur obeys the octet rule in the optimal zwitterionic Lewis structures and does not form S=O double bonds. No dominant resonance structure could be found for H 3PO 4 where polarized PO ?-bond and zwitterionic PO bond structures exhibit similar weights. 相似文献
5.
Please replace the paragraph Culture of material in Materialand method on page 574 (Fujii, Shimmen and Tazawa), Vol. 19,No. 4 with the following corrected paragraph. Materials and methods Culture of material Spirogyra sp. used for the experiments was collected in theriver Kamogawa in Kyoto. Cylindrical cells composing the filamentwere 55 µm in diameter and 100200 µm in length.Each cell usually had one spiral ribbon-like chloroplast. Thealga was cultured in slightly modified Reichardt's medium ( 27),1000 ml of which contained: 200 mg KNO 3, 20 mg K 2HPO 4, 10mgH 3BO 3, 6.6 mg FeSO 4?7H 2O, 25 mg Na 2EDTA (ethylenediamine tetraaceticacid disodium salt), 200 mg NaHCO 3, 50 mg CaSO 4?2H 2O, 10mg MgSO 4?7H 2O,0.5 mg ZnSO 4?7H 2O, 5mg MnCl 2?4H 2O, 24 µg Na 2MoO 4, 2 µgCoCl 2?6H 2O, 500 mg Tris. The pH was adjusted to 7.4 with HCl.The alga was cultured in a Petri dish at 20?1?C under a 16 hr8hr light-dark regime. The light intensity was about 2000 lux.Under such conditions, the cells divided once a day fairly synchronously. Experimental solutions Artificial pond water (APW) containing 0.1 mM each of KCl, NaCland CaCl 2 相似文献
6.
At the 2017 meeting of the Australian Society for Biophysics, we presented the combined results from two recent studies showing how hydronium ions (H 3O +) modulate the structure and ion permeability of phospholipid bilayers. In the first study, the impact of H 3O + on lipid packing had been identified using tethered bilayer lipid membranes in conjunction with electrical impedance spectroscopy and neutron reflectometry. The increased presence of H 3O + (i.e. lower pH) led to a significant reduction in membrane conductivity and increased membrane thickness. A first-order explanation for the effect was assigned to alterations in the steric packing of the membrane lipids. Changes in packing were described by a critical packing parameter (CPP) related to the interfacial area and volume and shape of the membrane lipids. We proposed that increasing the concentraton of H 3O + resulted in stronger hydrogen bonding between the phosphate oxygens at the water–lipid interface leading to a reduced area per lipid and slightly increased membrane thickness. At the meeting, a molecular model for these pH effects based on the result of our second study was presented. Multiple μs-long, unrestrained molecular dynamic (MD) simulations of a phosphatidylcholine lipid bilayer were carried out and showed a concentration dependent reduction in the area per lipid and an increase in bilayer thickness, in agreement with experimental data. Further, H 3O + preferentially accumulated at the water–lipid interface, suggesting the localised pH at the membrane surface is much lower than the bulk bathing solution. Another significant finding was that the hydrogen bonds formed by H 3O + ions with lipid headgroup oxygens are, on average, shorter in length and longer-lived than the ones formed in bulk water. In addition, the H 3O + ions resided for longer periods in association with the carbonyl oxygens than with either phosphate oxygen in lipids. In summary, the MD simulations support a model where the hydrogen bonding capacity of H 3O + for carbonyl and phosphate oxygens is the origin of the pH-induced changes in lipid packing in phospholipid membranes. These molecular-level studies are an important step towards a better understanding of the effect of pH on biological membranes. 相似文献
7.
Proton pumping pyrophosphatase (H +-PP iase) of pea stem mitochondriaappears to be localized on the inner surface of the inner membrane.Aminohexanediphosphonate and dichloromethylenediphosphonateexert different inhibitory effects on this activity and on thatof tonoplast. Antibody raised against membrane-bound mitochondrialH +-PP iase does not react with tonoplast vesicles. Thus, plantmitochondrial H +PP iase seems to have a molecular structure differentfrom that of vacuolar H +-PP iase. (Received August 2, 1996; Accepted October 18, 1996) 相似文献
8.
Periodic density functional theory (DFT) calculations were performed to investigate the adsorption of H 2O on U(001) surface. The metallic nature of uranium atom and different adsorption sites of U(001) surface play key roles in the H 2O molecular dissociate reaction. The long-bridge site is the most favorable site of H 2O-U(001) adsorption configuration. The triangle-center site of the H atom is the most favorable site of HOH-U(001) adsorption configuration. The interaction between H 2O and U surface is more evident on the first layer than that on any other two sub-layers. The dissociation energy of one hydrogen atom from H 2O is ?1.994 to ?2.215 eV on U(001) surface, while the dissociating energy decreases to ?3.351 to ?3.394 eV with two hydrogen atoms dissociating from H 2O. These phenomena also indicate that the O ads can promote the dehydrogenation of H 2O. A significant charge transfer from the first layer of the uranium surface to the H and O atoms is also found to occur, making the bonding partly ionic. 相似文献
9.
Protonation of produces the well-characterized polymolybdates, but at concentrations below 10 −3 M the dominant species is monomeric molybdic acid, H 2MoO 4. It is likely to be the species adsorbed on manganese oxide, a process thought to control levels in the ocean, because of the strong proton dependence of adsorption. The molecular structure of H 2MoO 4 is elusive, since it occurs only in dilute solutions. Using 244 nm laser excitation, near resonance with O → Mo charge-transfer electronic transitions of H 2MoO 4, we have detected a 919 cm −1 Raman band assignable to νsMoO. Using DFT, we have computed geometries and vibrational modes for the various structures consistent with the H 2MoO 4 formula. We tested the computations on a series of Mo(VI) oxo complexes with known vibrational frequencies, at several levels of theory. Best agreement with experimental values, at reasonable computational cost, was obtained with the B3LYP functional, employing a LANL2DZ ECP basis set for Mo and the 6-311+G(2df,p) basis set for O and H. Among the possible H 2MoO 4 structures only those based on the MoO 3 unit, with one, two or three coordinated water molecules, gave a scaled frequency for νsMoO that was within two standard deviations of 919 cm −1. Best agreement was obtained for MoO 3(H 2O) 3. The MoO 2 and MoO structures gave frequencies that were too high. The Mo(OH) 6 structure could be excluded, because its vibrational frequencies shift down strongly upon H/D exchange, whereas the 919 cm −1H 2MoO 4 band shifts up 1 cm −1 in D 2O. 相似文献
10.
The moisture content of coal affects the adsorption capacity of CO 2 on the coal surface. Since the hydrogen bonds are formed between H 2O and oxygen functional group, the H 2O cluster more easily adsorbs on the coal micropore than CO 2 molecule. The coal micropores are occupied by H 2O molecules that cannot provide extra space for CO 2 adsorption, which may leads to the reduction of CO 2 adsorption capacity. However, without considering factors of micropore and oxygen functional groups, the co-adsorption mechanisms of CO 2 and adsorbed H 2O molecule are not clear. Density functional theory (DFT) calculations were performed to elucidate the effect of adsorbed H 2O to CO 2 adsorption. This study reports some typical coal-H 2O···CO 2 complexes, along with a detailed analysis of the geometry, energy, electrostatic potential (ESP), atoms in molecules (AIM), reduced density gradient (RDG), and energy decomposition analysis (EDA). The results show that H 2O molecule can more stably adsorb on the aromatic ring surface than CO 2 molecule, and the absolute values of local ESP maximum and minimum of H 2O cluster are greater than CO 2. AIM analysis shows a detailed interaction path and strength between atoms in CO 2 and H 2O, and RDG analysis shows that the interactions among CO 2, H 2O, and coal model belong to weak van der Waals force. EDA indicates that electrostatic and long-range dispersion terms play a primary role in the co-adsorption of CO 2 and H 2O. According to the DFT calculated results without considering micropore structure and functional group, it is shown that the adsorbed H 2O can promote CO 2 adsorption on the coal surface. These results demonstrate that the micropore factor plays a dominant role in affecting CO 2 adsorption capacity, the attractive interaction of adsorbed H 2O to CO 2 makes little contribution. 相似文献
11.
Abstract The main goal of this paper is to study the oxygen adsorption on the Zr(0001) surface using first-principles total-energy calculations based on density-functional theory. We present preliminary results which concern the atomic oxygen adsorption on the Zr(0001) surface. We first report a static study where we calculate the atomic structure and adsorption energy for oxygen occupying various surface and subsurface sites at three different coverages: Θ = 1/4, 1/2, and 1 ML. We find that oxygen atoms are preferentially adsorbed into the octahedral holes between the 2nd and 3rd metallic layers. We secondly perform ab initio molecular dynamics calculations for the Zr(0001) – (3 × 3) – O system to show how the oxygen can penetrate through the surface and how it finally reaches its equilibrium position, trapped between the 1st and 2nd zirconium layers. 相似文献
12.
A paramagnetic binuclear molybdenum(V) thioglycolate of composition Mo 2(L) 5(H 2O) 2 (H 2L = CH 2SHCOOH, thioglycolic acid) has been synthesized by direct reduction of molybdenum(VI) oxide hydrate (MoO 3 · H 2O) with thioglycolic acid in an argon atmosphere. Based on the combined results of elemental analysis, EPR, IR 1H NMR, electronic spectra, magnetic susceptibility, cyclic voltametry and x-ray photoelectron spectral measurements, it is concluded that in the title compound, both the molybdenum atoms are in pentavalent state with octahedral coordination through both sulphur and oxygen atoms of thioglycolic acid and water molecules. The two molybdenum ions have slightly different coordination environments due to bridging thioglycolate ions. 相似文献
13.
An empirical model was applied to describe the growth related formation of scleroglucan in batchwise cultivation of Sclerotium rolfsii. In this case, the level of oxygen supply controls the carbon flux into glucan, biomass, and CO 2 evolution and therefore determines the yield coefficients Y Glucan/BDM and Y BDM/O2. It was observed that scleroglucan formation is enhanced under microaerobic conditions. However, as the empirical model and data of actual batch cultivations show, different maxima exist for product end concentration [g/l] and volumetric productivity [g/ld] depending on the total oxygen uptake during cultivation. A sufficient bulk mixing of the highly viscous culture suspension becomes particularly important during large-scale cultivations. In addition, the scleroglucan production process proved to be shear sensitive. A correlation between the attainable molecular weight of the glucan and the stirrer tip velocity in bioreactors of different sizes is presented. For all these reasons, a scale-up of this process is very complex. Large-scale cultivations under microaerobic conditions, aiming for maximum product end concentration, were slowed down by poor bulk mixing leading to a lower carbon flux into glucan formation. On the other hand, a scale-up designed for maximum volumetric productivity using high oxygen supply was successfully conducted up to a reactor volume of 1.500 l. To minimize the loss in product quality (molecular weight of the glucan) due to high stirrer tip velocities, a mixing concept was developed employing reduced agitation combined with maximum aeration to secure a sufficient axial bulk mixing in the reactor. 相似文献
14.
A series of homologous mononuclear dioxomolybdenum complexes were prepared and fully characterized with structurally related thiosemicarbazone ligands supplying a tridentate O,N,S donor set to the central metal atom. The ligands are derived from the prototype 2-hydroxybenzaldehyde-4-triphenylmethylthiosemicarbazone (H 2L). Within this series the crystal structures of 11 complex compounds [MoO 2(LR n)(dmf)] and [MoO 2(LR n)(MeOH)] were determined showing characteristic differences in the gross structural properties of the central metal core. From the variation of substituents in this ligand library the influences of electronic ligand effects on the spectroscopic, electrochemical, and functional properties of these biomimetic model complexes for molybdenum-containing oxotransferases are reported. 相似文献
15.
The adsorption of 5-AMP and 5-CMP was studied in saturated solutions of several soluble mineral salts (NaCl, Na 2SO 4, MgCl 2·6H 2O, MgSO 4·7H 2O, CaCl 2·2H 2O, CaSO 4·2H 2O, SrCl 2·6H 2O, SrSO 4, and ZnSO 4·7H 2O) as a function of pH, ionic strength, and surface area of the solid salt. The adsorption shows a pH dependence; this can be correlated with the charge on the nucleotide molecule which is determined by the state of protonation of the N-1 nitrogen of 5-AMP or N-3 nitrogen of 5-CMP and the phosphate oxygens. The adsorption which results from the binding between the nucleotide molecule and the salt surface is proposed as being due to electrostatic forces. It was concluded that the adsorption was reversible in nature. The adsorption shows a strong dependence upon ionic strength and decreases with increasing ionic strength. Surface area is shown to be an important factor in evaluating and comparing the magnitude of adsorption of nucleotides onto various mineral salts. The implications of the results of the study are discussed in terms of the importance of soluble mineral salts as adsorption sites in the characterization of the adsorption reactions of an adsorbed template in biogeochemical cycles. 相似文献
16.
WOCl 4 reacts with (Me 3Si) 2O and excess THF to give [WO 2Cl 2(THF)] 4 ( 1), a new tetrameric tungsten(VI)-oxo complex, which was characterized and crystal structure was determined by X-ray crystallography. Complex 1 has a roughly square planar tetranuclear structure bridged by μ-oxo ligands. Each tungsten atom is coordinated by two bridging oxygens, one terminal oxygen, two “axial” chlorine atoms and one “equatorial” O-bonded THF ligand. One of the two μ-oxo ligands is similar to the terminal oxygen atom and the other one is similar to the coordinated oxygen atom of the THF ligand, respectively, which confirmed a previous proposal. Four WO 3Cl 2(THF) octahedral are associated by sharing corners. Complex 1 is different from three known tetrameric tungsten analogues in its structural arrangement and properties. 相似文献
17.
The ability of pristine graphene (PG) and Al-doped graphene (AlG) to detect toxic acrolein (C 3H 4O) was investigated by using density functional calculations. It was found that C 3H 4O molecule can be adsorbed on the PG and AlG with adsorption energies about ?50.43 and – v30.92 kcal mol ?1 corresponding to the most stable configurations, respectively. Despite the fact that interaction of C 3H 4O has no obvious effects on the of electronic properties of PG, the interaction between C 3H 4O and AlG can induce significant changes in the HOMO/LUMO energy gap of the sheet, altering its electrical conductivity which is beneficial to sensor designing. Thus, the AlG may be sensitive in the presence of C 3H 4O molecule and might be used in its sensor devices. Also, applying an external electric filed in an appropriate orientation (almost stronger than 0.01 a.u.) can energetically facilitate the adsorption of C 3H 4O molecule on the AlG. 相似文献
18.
植物叶片水H 218O富集对大气中O 2和CO 2的 18O收支有着重要影响。蒸腾作用使植物叶片水H 218O富集, 而植物叶片水H 218O富集的程度主 要受大气水汽δ 18O和植物蒸腾水汽δ 18O的影响。过去, 通过引入稳态假设(蒸腾δ 18O等于茎水δ 18O)得到Craig-Gordon模型的闭合形式, 或 将植物整个叶片水δ 18O经过Péclet效应校正后得到植物叶片水δ 18O的富集程度。然而, 在几分钟到几小时的短时间尺度上, 植物叶片蒸腾 δ 18O是变化的, 稳态假设是无法满足的。最近成功地实现了对大气水汽δ 18O和δD的原位连续观测, 观测精度(小时尺度)可达到甚至优于稳定 同位素质谱仪的观测精度。在非破坏性条件下, 高时间分辨率和连续的大气水汽δ 18O和蒸腾δ 18O的动态观测, 将提高植物叶片水H 218O富集的 预测能力。该文综述了植物叶片水H 218O富集的理论研究的新进展、研究焦点和观测方法所存在的问题, 旨在进一步加深理解植物叶片水H 218O 富集的过程及其机制。 相似文献
19.
Considerable efforts have been made to develop reactive oxygen species (ROS) scavengers for removing high level of ROS. However, most of the reported ROS scavengers are nondegradable and involve harsh reaction conditions as well as utilize various surface ligands. In order to overcome these drawbacks, in the present work, we develop a facile and mild synthesis avenue for preparation of surface-clean hydrogen-doped molybdenum oxide (H0.34MoO3) via simply mixing MoO3 dispersion with aluminum foil under an acidic environment without any surface capping reagents at room temperature. The resulting H0.34MoO3 can act as a broad-spectrum ROS scavenger, including .OH, H2O2, O2−, and 1O2 as well as 2, 2-diphenyl-1-picrylhydrazyl (DPPH). The free radical scavenging activity of H0.34MoO3 achieves as high as 71.6% and 99.1% for .OH and DPPH scavenging, which is comparable and superior to that of ascorbic acid that is a classic free radical scavenger. More significantly, the resulting H0.34MoO3 is degrade, which can be degraded into molybdate ions under a neutral environment (pH 7.4). 相似文献
20.
The crystal and molecular structures of Th(oda) 2(H 2O) 4·6H 2O (1) and Na 2[Th(oda) 3]·2NaNO 3 (2) (oda = oxydiacetate) have been determined from three-dimensional X-ray diffraction data and refined by least squares to R = 0.049 and Rw = 0.049 for 2265 independent reflections for (1) and to R = 0.024 and Rw = 0.023 for 2196 independent reflections for (2).Crystal parameters are as follows: (1), tetragonal, space group P4 12 12, a = 10.335(2), c = 20.709(5) Å and Z = 4; (2), monoclinic, space group C2/c, a = 17.096(5), b = 9.451(2), c = 16.245(4) Å, β = 107.8(1) and Z = 4.In both compounds the thorium atom lies on a crystallographic two-fold axis. The co-ordination number for thorium in (1) is 10 (bicapped square antiprism geometry), the compound is monomeric, the two oda ligands are tridentate to the metal, and four water molecules complete the coordination sphere; in thorium (2) the coordination number is 9 (tricapped trigonal prism geometry) with three oda ligands tridentate to the metal, the [Th(oda) 3] 2? and NO 3? anions are held together through the sodium ions which are coordinated both to the oda carboxylic oxygens and to the nitrate oxygens.The ThO coordination distances are: in (1) 2.411(8), 2.414(9) for the carboxylic oxygens, 2.479(10) and 2.486(8) for water molecules and 2.697(9) for the etheric oxygen and in (2) 2.384(3), 2.402(4) and 2.402(4) for the carboxylic oxygens, 2.559(5) and 2.562(4) Å for the etheric oxygens. 相似文献
|