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3.
1. In membranes prepared from dark grown cells of Rhodopseudomonas capsulata, five cytochromes of b type ( E′ 0 at pH 7.0 +413±5, +270±5, +148±5, +56±5 and −32±5 mV) can be detected by redox titrations at different pH values. The midpoint potentials of only three of these cytochromes ( b148, b56, and b−32) vary as a function of pH with a slope of 30 mV per pH unit. 2. In the presence of a Co/N2 mixture, the apparent E′0 of cytochrome b270 shifts markedly towards higher potentials (+355 mV); a similar but less pronounced shift is apparent also for cytochrome b150. The effect of CO on the midpoint potential of cytochrome b270 is absent in the respiration deficient mutant M6 which possesses a specific lesion in the CO-sensitive segment of the branched respiratory chain present in the wild type strain. 3. Preparations of spheroplasts with lysozyme digestion lead to the release of a large amount of cytochrome c2 and of virtually all cytochrome cc′. These preparations show a respiratory chain impaired in the electron pathway sensitive to low KCN concentration, in agreement with the proposed role of cytochrome c2 in this branch; on the contrary, the activity of the CO-sensitive branch remains unaffected, indicating that neither cytochrome c2 nor the CO-binding cytochrome cc′ are involved in this pathway. 4. Membranes prepared from spheroplasts still possess a CO-binding pigment characterized by maxima at 420.5, 543 and 574 nm and minima at 431, 560 nm in CO-difference spectra and with an band at 562.5 nm in reduced minus oxidized difference spectra. This membrane-bound cytochrome, which is coincident with cytochrome b270, can be classified as a typical cytochrome “o” and considered the alternative CO-sensitive oxidase. 相似文献
4.
The thermophilic blue-green alga Synechococcus lividus was grown at 38 and 55°C. The reaction center chlorophyll-protein complexes (CP) of Photosystem (PS I) and PS II, CP aI and CP aII, were isolated by sodium dodecyl sulphate (SDS) polyacrylamide gel electrophoresis at 4°C. SDS solubilization of thylakoids was performed in the temperature range 0–65°C. The low-temperature absorption and fluorescence emission spectral properties of the isolated chlorophyll-protein complexes were analyzed. Only traces of CP aI were solubilized at temperatures below the lipid phase transition temperature. Instead, a minor PS I component, CP a′ I, was obtained that had absorption and fluorescence characteristics similar to those of CP aI. CP a′ I had a slightly lower mobility than CP aI in SDS-polyacrylamide gel electrophoresis. The amount of CP aI in the gel scan profile increased dramatically when solubilization was carried out above the phase transition temperatures, but started to decrease above 60°C. CP aII, on the other hand, could be efficiently extracted even at 0°C and was stable in the scan profile up to extraction temperatures of 30–40°C. Low-temperature absorption and fluorescence emission spectra were typical for CP aI and CP aII and no specific effects of the two growth temperatures on these properties were observed. The phase transition temperature was considered to be critical for the solubilization of CP aI, either because of the difficulties of SDS (especially as it forms micelles at low temperatures) in penetrating the solidified membrane lipids at temperatures below that of the phase transition or because the CP aI monomers of the PS I antennae are so strongly bound to each other that they cannot be dissociated by SDS before thermal agitation has reached a certain level that is achieved above the phase transition temperature. We consider both the difficulties in solubilizing CP aI at sub-transition temperatures and the heat stability of the two complexes as adaptations which enable Synechococcus to grow under extreme high-temperature regimes. 相似文献
5.
Reaction of RuCl(η 5-C 5H 5( pTol-DAB) with AgOTf (OTf = CF 3SO 3) in CH 2Cl 2 or THF and subsequent addition of L′ (L′ = ethene (a), dimethyl fumarate (b), fumaronitrile (c) or CO (d) led to the ionic complexes [Ru(η 5-C 5H 5)( pTol-DAB)(L′)][OTf] 2a, 2b and 2d and [Ru(η 5-C 5H 5)( pTol-DAB)(fumarontrile- N)][OTf] 5c. With the use of resonance Raman spectroscopy, the intense absorption bands of the complexes have been assigned to MLCT transitions to the iPr-DAB ligand. The X-ray structure determination of [Ru(η 5-C 5H 5)( pTol-DAB)(η 2-ethene)][CF 3SO 3] (2a) has been carried out. Crystal data for 2a: monoclinic, space group P2 1/ n with A = 10.840(1), b = 16.639(1), C = 14.463(2) Å, β = 109.6(1)°, V = 2465.6(5) Å 3, Z = 4. Complex 2a has a piano stool structure, with the Cp ring η 5-bonded, the pTol-DAB ligand σN, σN′ bonded (Ru-N distances 2.052(4) and 2.055(4) Å), and the ethene η 2-bonded to the ruthenium center (Ru-C distances 2.217(9) and 2.206(8) Å). The C = C bond of the ethene is almost coplanar with the plane of the Cp ring, and the angle between the plane of the Cp ring and the double of the ethene is 1.8(0.2)°. The reaction of [RuCl(η 5-C 5H 5)(PPh) 3 with AgOTf and ligands L′ = a and d led to [Ru(η 5-C 5H 5)(PPh 3) 2(L′)]OTf] (3a) and (3d), respectively. By variable temperature NMR spectroscopy the rottional barrier of ethene (a), dimethyl fumarate (b and fumaronitrile (c) in complexes [Ru(η 5-C 5H 5)(L 2)(η 2-alkene][OTf] with L 2 = iPr-DAB (a, 1b, 1c), pTol-DAB (2a, 2b) and L = PPh 3 (3a) was determined. For 1a, 1b and 2b the barrier is 41.5±0.5, 62±1 and 59±1 kJ mol −1, respectively. The intermediate exchange could not be reached for 1c, and the Δ G# was estimated to be at least 61 kJ mol −. For 2a and 3a the slow exchange could not be reached. The rotational barrier for 2a was estimated to be 40 kJ mol −. The rotational barier for methyl propiolate (HC≡CC(O)OCH 3) (k) in complex [Ru(η 5-C 5H 5)(iPr-DAB) η 2-HC≡CC(O)OCH 3)][OTf] (1 k) is 45.3±0.2 kJ mol −1. The collected data show that the barrier of rotational of the alkene in complexes 1a, 2a, 1b, 2b and 1c does not correlate with the strength of the metal-alkene interaction in the ground state. 相似文献
6.
The shear piezoelectricity was observed in oriented films of poly-β-hydroxybutyrate (PHB) and copolymers of β-hydroxybutyrate (HB) and β-hydroxyvalerate (HV). The piezoelectric stress constant 3 14 = e′ 14 − ie″ 14 (polarization/strain), the piezoelectric strain constant d14 = d′ 14 − id″ 14 (polarization/stress), the elastic constant c = c′ + ic″ and the dielectric constant = ′ − i″ were determined at a frequency of 10 Hz over a temperature range from −150° to +150°C. Piezoelectric relaxations as well as elastic and dielectric relaxations were clearly observed at the glass transition temperature of about 15°C. In order to evaluate the piezoelectric constants ( e2 and d2) for the piezoelectric phase which consists of the crystalline region and the oriented non-crystalline region, a spherical dispersion two phase model was utilized. Assuming the appropriate fixed values for the elastic and dielectric constants in the piezoelectric phase, d2 and d2 were calculated as a function of temperature. For a PHB and a copolymer (17 HV/83 HB), e2 and d2 showed relaxations, leading to a conclusion that the instantaneous piezoelectric constant in the crystalline phase is constant independent of temperature but the piezoelectric constant in the oriented non-crystalline phase is relaxational and has the opposite sign. For a copolymer (25 HV/75 HB) and a chloroform treated copolymer (17 HV/83 HB), e2 and d2 were constant independent of temperature, indicating that the oriented non-crystalline phase has disappeared owing to the increased molecular flexibility due to copolymerization or annealing in chloroform vapour. 相似文献
7.
1,10-Phenanthroline-5,6-dione (C 12H 6N 2O 2 (1)) reacts with V(η 6-mesitylene) 2 and Ti(η 6-toluene) 2 affording coordination compounds of general formula M( O, O′---C 12H 6N 2O 2) 3 (M=Ti (2); M=V (3)) which further react with TiCl 4 or TiCp 2(CO) 2 yielding the tetrametallic species M( O, O′---C 12H 6N 2O 2--- N, N′) 3(M′L n) 3 (M=V, M′L n=TiCl 4 (4); M=Ti, M′L n=TiCp 2 (5); M=V, M′L n=TiCp 2 (6)). The complex salt [Fe( N, N′---C 12H 6N 2O 2) 3][PF 6] 2 (7) has been obtained from iron(II) chloride tetrahydrate and 1 in the presence of NH 4PF 6. The reaction of 7 with TiCp 2(CO) 2 affords the tetrametallic derivative [Fe( N, N′---C 12H 6N 2O 2--- O, O′) 3(TiCp 2) 3][PF 6] 2 (8). TiCl 2(THF) 2 reacts with MCp 2( O, O′---C 12H 6N 2O 2) to give MCp 2( O, O′---C 12H 6N 2O 2--- N, N′)TiCl 2 (M=Ti (9); M=V (10)). By reaction of TiCp 2( O, O′---C 12H 6N 2O 2--- N, N′)TiCl 2 (9) with C 12H 6N 2O 2, the bimetallic derivative TiCp 2( O, O′---C 12H 6N 2O 2--- N, N′)TiCl 2( O, O′---C 12H 6N 2O 2) (11) has been prepared, which readily adds to TiCl 4, to give the trimetallic titanium derivative TiCp 2( O, O′---C 12H 6N 2O 2--- N, N′)TiCl 2( O, O′---C 12H 6N 2O 2--- N, N′)TiCl 4 (12). VCp 2( O, O′---C 12H 6N 2O 2--- N, N′)TiCl 2 (10) reacts with the tris-chelate iron(II) cation 7 affording the heptametallic cationic complex [Fe( N, N′---C 12H 6N 2O 2--- O, O′)TiCl 2( N, N′---C 12H 6N 2O 2--- O, O′)VCp 2] 3 +2 isolated as the hexafluorophosphate 13. 相似文献
8.
A number of N, N′-bis(4-substituted phenyl)-1,7-diaza-12-crown-4 and N, N′-bis(4-substituted phenyl)-1, 10-diaza-18-crown-6 (where the substituents are OCH 3, CH 3, H, Cl, respectively) have been prepared by cyclization reaction of a ditosylate with the appropriately substituted diol. These new macrocyclic ligands have been characterized by means of elemental analysis, IR, 1H NMR and MS spectra. The crystal structures of N, N′-bis(4-chlorophenyl)-1,10-diaza-18-crown-6 (21) and its complex with barium thiocyanate Ba(SCN) 2 (22) have been determined by single crystal X-ray diffraction. The crystallographic data are as follows: 21: C 24H 32Cl 2N 2O 4, orthorhombic, P2 12 12 1, A=4.852(1), B=11.989(2), C=41.231(8) Å, V=2398.7(8) Å 3, Z=4; 22: C 26H 32Cl 2N 4O 4S 2Ba, monoclinic, P2 1/ c, A=8.801(2), B=11.653(9), C=15.756(6) Å, ß=105.96(3)°, V=1553.7(14) Å 3, Z=2. In the complex, the Ba atom is eight-coordinate (O(1), O(2), O(1)′, O(2)′, N(1), N(1)′, N(21), N(21)′) to form a distorted D6h geometry with the Ba atom at the center of crystallographic symmetry. 相似文献
10.
This report describes the effect of temperature on the mechanical viscoelastic properties such as: storage modulus ( E′), loss modulus ( E″), and loss tangent (tan δ) of the collagen sponges modified with hyaluronic acid (HA). In order to detect collagen–HA copolymer denaturation and to assess its thermal stability, the differential scanning calorimetry (DSC) supplemented by thermogravimetric (TG) measurements was used. The denaturation temperature ( Td) of unmodified collagen samples increased from 69 to 86 °C for cross-linked samples, respectively. These temperature dependencies show remarkable changes in E′ and E″ at selected temperature up to 226 °C for all samples due to the release of loosely and strongly bound water. The influence of HA on the viscoelastic behavior of collagen is manifested by a shift of the tan δ peak associated with the process of decomposition towards higher temperatures resulting in a higher thermo-stability of the modified scaffolds. 相似文献
11.
The dielectric constant, ′, and the dielectric loss, ″, for gelatin films were measured in the glassy and rubbery states over a frequency range from 20 Hz to 10 MHz; ′ and ″ were transformed into M* formalism ( M*=1/( ′− i″)= M′+ iM″; i, the imaginary unit). The peak of ″ was masked probably due to dc conduction, but the peak of M″, e.g. the conductivity relaxation, for the gelatin used was observed. By fitting the M″ data to the Havriliak–Negami type equation, the relaxation time, τHN, was evaluated. The value of the activation energy, Eτ, evaluated from an Arrhenius plot of 1/ τHN, agreed well with that of Eσ evaluated from the DC conductivity σ0 both in the glassy and rubbery states, indicating that the conductivity relaxation observed for the gelatin films was ascribed to ionic conduction. The value of the activation energy in the glassy state was larger than that in the rubbery state. 相似文献
12.
Cigarette smoke is known to generate free radicals by various mechanisms. In this study involving 30 non-smokers and 30 smokers, we show that urinary excretion of 5-(hydroxymethyl) uracil (HMUra) was not different in the two groups (6.54±2.07 vs. 6.70±1.68 nmol/mmol creatinine). In contrast, 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxo-dGuo) excretion increased by 16% (1.16±0.35 vs. 1.35±0.50 nmol/mmol creatinine, p=0.039). Results concerning 8-oxo-dGuo are in agreement with those of previous studies. We observed significant multiple correlations between HMUra and creatinine ( rp=0.44), BMI ( rp=-0.27) and nicotine derivatives ( rp=0.26). Multiple correlation analysis showed relations between 8-oxo-dGuo on the one hand, and: creatinine ( rp=0.36), nicotine derivatives ( rp=0.29), BMI ( rp=-0.24) on the other. 相似文献
13.
The storage moduli ( G′) of phase-separated co-gels formed by quench-cooling mixed solutions of gelatin and potato maltodextrin (Paselli SA-2 and SA-6) have been related quantitatively to the experimentally-determined concentration-dependence of G′ for the constituent polymers. Distribution of water between the phases was examined explicitly by using polymer blending laws to derive calculated moduli for gelatin-continuous and maltodextrin-continuous networks over the entire range of solvent partition. Allowance was made for the direct contribution of polymer chains, and for density differences between the phases, in calculating relative phase-volumes. The effect of gel formation prior to phase-separation was calculated using classical theory for network de-swelling. Good agreement with observed moduli for more than 30 gelatin/maltodextrin combinations was achieved using a single adjustable parameter, p (the ratio of solvent to polymer in the gelatin phase divided by the same ratio for the maltodextrin phase), with an optimum value of p ≈ 1·8 for both SA-6 and SA-2. 相似文献
14.
A novel one-pot three-component condensation reaction of an aldehyde, β-ketoester and 2-aminobenzimidazole or 2-aminobenzothiazole in 1,1,3,3- N, N, N′, N′-tetramethylguanidinium trifluoroacetate as an ionic liquid is described. During the course of this reaction 4 H-pyrimido[2,1- b]benzimidazoles or 4 H-pyrimido[2,1- b]benzothiazoles are formed in high yields at 100 °C. The ionic liquid can be recovered conveniently and reused efficiently. 相似文献
15.
In order to assess effects of drying method on chemical composition and NIR spectra of pasture silage, 20 samples of silages from permanent pastures of different qualities were subsampled and dried either by forced draught oven at 65°C or freeze-dried. Samples were analysed for crude protein (CP), crude fibre (CF), neutral detergent fibre (NDF), acid detergent fibre (ADF), gross energy (GE) and in vitro digestible organic matter in the dry matter (DOMD) and composition expressed on a dry-matter (DM) basis, either obtained as oven 105°C DM (DM 105°) or toluene DM (DM tol). Effects of the drying method on chemical composition were estimated by paired comparisons. Near-infrared reflectance (NIR) spectra were taken and the difference spectra between treatments for each sample were plotted in order to visually inspect effects of treatments, either as log 1/ R or transformed by their first derivative. Principal components explaining spectral variability were computed and samples graphically displayed according to the eigenvalues of the first (1 and 2), or second (2 and 3) pairs of principal components. Oven-drying resulted in a reduction in CP ( p<0.02) content and an increase in CF ( p<0.1), NDF ( p<0.001) and ADF ( p<0.06) content of silages, when expressed on a DM 105° basis. When expressed on a DM tol basis, a reduction in CP ( p<0.02) and DOMD ( p<0.06) content was observed with oven drying, but fibre fractions were not affected ( p>0.1). Effects of the drying treatment were visually apparent on NIR spectra when plotted as log 1/ R against wavelengths, mainly as a baseline shift. Difference spectra (OD − FD), both as log 1/ R and its first derivative, showed consistent absorption bands, indicative of different molecular responses of OD and FD silages to incident light. Plotting samples according to eigenvalues of the first two or second two principal components suggests that drying methods affect the distribution of samples. This is also indicative of an effect of drying treatment on spectral features and reinforces the general advice that sample processing should be consistent in order to avoid adding errors to NIR analysis. 相似文献
16.
This study uses chlorophyll a fluorescence to examine the effect of environmentally relevant (1–4 h) exposures of thermal stress (35–45 °C) on seagrass photosynthetic yield in seven tropical species of seagrasses. Acute response of each tropical seagrass species to thermal stress was characterised, and the capacity of each species to tolerate and recover from thermal stress was assessed. Two fundamental characteristics of heat stress were observed. The first effect was a decrease in photosynthetic yield ( Fv / Fm) characterised by reductions in F and Fm′. The dramatic decline in Fv / Fm ratio, due to chronic inhibition of photosynthesis, indicates an intolerance of Halophila ovalis, Zostera capricorni and Syringodium isoetifolium to ecologically relevant exposures of thermal stress and structural alterations to the PhotoSystem II (PSII) reaction centres. The decline in Fm′ represents heat-induced photoinhibition related to closure of PSII reaction centres and chloroplast dysfunction. The key finding was that Cymodocea rotundata, Cymodocea serrulata, Halodule uninervis and Thalassia hemprichii were more tolerant to thermal stress than H. ovalis, Z. capricorni and S. isoetifolium. After 3 days of 4 h temperature treatments ranging from 25 to 40 °C, C. rotundata, C. serrulata and H. uninervis demonstrated a wide tolerance to temperature with no detrimental effect on Fv / Fm′ qN or qP responses. These three species are restricted to subtropical and tropical waters and their tolerance to seawater temperatures up to 40 °C is likely to be an adaptive response to high temperatures commonly occurring at low tides and peak solar irradiance. The results of temperature experiments suggest that the photosynthetic condition of all seagrass species tested are likely to suffer irreparable effects from short-term or episodic changes in seawater temperatures as high as 40–45 °C. Acute stress responses of seagrasses to elevated seawater temperatures are consistent with observed reductions in above-ground biomass during a recent El Niño event. 相似文献
17.
Neuropeptide Y (NPY) is a potent orexigenic peptide that is implicated in the feeding response to a variety of stimuli. The current studies employed mice lacking NPY ( Npy−/−) and their wild-type ( Npy+/+) littermates to investigate the role of this peptide in the feeding response to circadian and palatability cues. To investigate the response to a circadian stimulus, we assessed food intake during the 4-h period following dark onset, a time of day characterized by maximal rates of food consumption. Compared to Npy+/+ controls, intake of Npy− /− mice was reduced by 33% during this period (0.6 ± 0.1 g versus 0.9 ± 0.1 g; p ≤ 0.05). In contrast, intake did not differ between genotypes when measured over a 24-h period (3.7 ± 0.2 g versus 3.5 ± 0.3 g; p = ns). Furthermore, reduced dark cycle 4 h food intake in Npy− /− mice was not evident after a 24-h fast (1.4 ± 0.1 g for both genotypes; p = ns), despite a pronounced delay in the initiation of feeding (636 ± 133 s versus 162 ± 29 s; p ≤ 0.05). To investigate the role of NPY in the feeding response to palatability cues, mice were presented with a highly palatable diet (HP) for 1 h each day (in addition to having ad libitum access to chow) for 18 days. Npy+/+ mice rapidly increased daily HP intake such that by the end of the first week, they derived a substantial fraction of daily energy from this source (41 ± 3%). By comparison, HP intake was markedly reduced in Npy−/− mice during the first week (24 ± 7% of daily energy intake, p ≤ 0.05 versus Npy+/+), although it eventually increased (by Day 9) to values comparable to those of Npy+/+ controls. These experiments suggest that NPY contributes to the mechanism whereby food intake increases in response to circadian and palatability cues and that mechanisms driving food intake in response to these stimuli differ from those activated by energy restriction. 相似文献
18.
Muscle damage resulting from eccentric exercise provides a useful model of oxyradical-induced injury and can be used to examine age-related responses to oxidative stress. Sixteen young (26.4 ± 3.3 years) and 16 older (71.1 ± 4.0 years) healthy men were randomly assigned to 1000 IU/d vitamin E or placebo for 12 weeks and ran downhill for 45 min at 75% VO 2max, once before and following supplementation. Blood samples were obtained before (baseline) and immediately postexercise (0 h), and at 6, 24, and 72 h postexercise to determine antioxidant status, muscle damage, lipid peroxidation, and DNA damage. Following exercise, young and older men experienced similar increases in serum creatine kinase (CK), F 2-isoprostanes (iPF 2; p < .001) and malondialdehyde (MDA; p < .01), although iPF 2 peaked at 72 h postexercise and MDA peaked at 0 h. Oxygen Radical Absorbance Capacity (ORAC) decreased at 72 h ( p < .01) and correlated with the rise in iPF 2, MDA, and CK in the young men ( p < .05). Leukocyte 8-hydroxy-2′-deoxyguanosine (8-OHdG) was unaffected by exercise. Vitamin E decreased peak CK in young men, while in older men it decreased resting levels of iPF 2 and suppressed the 24 h postexercise increases in iPF 2 ( p < .05). Thus, vitamin E supplementation induced modest changes eccentric exercise-induced oxidative stress, although differentially between the young and older subjects, while age had no direct influence on these responses among this group of physically fit subjects. 相似文献
19.
The heteroditopic ligand 4′-(4,7,10-trioxadec-1-yn-10-yl)-2,2′:6′,2″-terpyridine, 2, contains an N, N′, N″-donor metal-binding domain that recognizes iron(II), and a terminal alkyne site that selectively couples to platinum(II). This selectivity has been used to investigate routes to the formation of heterometallic systems. The single crystal structures of ligand 2 and the complex [Fe(2) 2][PF 6] 2 are reported. 相似文献
20.
Five heterometallic compounds with formulae [Ba(H 2O) 4Cr 2(μ-OH) 2( nta) 2] · 3H 2O (I), [M( bpy) 2(H 2O) 2] [Cr 2(OH) 2( nta) 2] · 7H 2O, where M 2+ = Zn, (II); Ni, (III); Co, (IV) and [Mn(H 2O) 3( bpy)Cr 2(OH) 2( nta) 2] · ( bpy) · 5H 2O (V); bpy = 2,2′-bipyridine, ( nta = nitrilotriacetate ion) have been prepared by reaction of I with the corresponding M II-sulfates in the presence of 2,2′-bipyridine. Substances I–V have been characterized by magnetic susceptibility measurements, EPR and X-ray determinations. I represents a 2D coordination polymer formed by coordination of centrosymmetrical dimeric chromium(III) units and Barium cations. The 10-coordinate Ba polyhedron is completed by four water molecules. Compounds II–IV are isostructural and consist of non-centrosymmetric dimeric anions [Cr 2(μ-OH) 2( nta) 2] 2−, complex cations [M II( bpy) 2(H 2O) 2] 2+ and solvate water molecules. The octahedral coordination of chromium atoms implies four donor atoms of the nta3− ligands and two bridging OH groups. Multiple hydrogen bonds of coordinated and solvate water molecules link anions and cations in a 3D network. A similar [Cr 2(μ-OH) 2( nta) 2] 2− unit is found in V. The bridging function is performed by a carboxylate oxygen atom of the nta ligand that leads to the formation of a trinuclear complex [Mn( bpy)(H 2O) 2Cr 2(μ-OH) 2( nta) 2]. Experimental and calculated frequency and temperature dependences of EPR spectra of these compounds are presented. The fine structure appearing on the EPR spectra of compound V is analyzed in detail at different temperatures. It is established that the main part of the EPR signals is due to the transitions in the spin states of a spin multiplet with S = 2. Analyses of experimental and calculated spectra confirm the absence of interaction between metal ions (M II) and Cr-dimers in complexes III and IV and the presence of weak Mn–Cr interactions in V. The temperature dependence of magnetic susceptibilities for I–V was fitted on the basis of the expression derived from isotropic Hamiltonian including a bi-quadratic exchange term. 相似文献
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