共查询到20条相似文献,搜索用时 15 毫秒
1.
Current knowledge about the abundance, growth, and primary production of the seagrass Cymodocea nodosa (Ucria) Ascherson is biased towards shallow (depth <3 m) meadows although this species also forms extensive meadows at larger depths along the coastlines. The biomass and primary production of a C. nodosa meadow located at a depth of 8–11 m was estimated at the time of maximum annual vegetative development (summer) using reconstruction techniques, and compared with those available from shallow meadows of this species. A depth-referenced data base of values at the time of maximum annual development was compiled to that end. The vegetative development of C. nodosa at 8–11 m depth was not different from that achieved by shallow (depth <3 m) meadows of this species. Only shoot density, which decreased from 1637 to 605 shoots m−2, and the annual rate of elongation of the horizontal rhizome, which increased from 23 to 71 cm apex−1 year−1, were different as depth increased from <3 to 8–11 m. Depth was a poor predictor of the vegetative development and primary production of C. nodosa. The biomass of rhizomes and roots decreased with depth (g DW m−2 = 480 (±53, S.E.) − 32 (±15, S.E.) depth (in m); R2 = 0.12, F = 4.65, d.f. = 35, P = 0.0381) which made total biomass of the meadow to show a trend of decrease with depth but the variance of biomass data explained by depth was low. The annual rate of elongation of the horizontal rhizome showed a significant positive relationship with depth (cm apex−1 year−1 = 18 (±5.1, S.E.) + 5.0 (±1.33, S.E.) depth (in m); R2 = 0.50, F = 14.07, d.f. = 14, P = 0.0021). As shoot size and growth did not change significantly with depth, the reduction of shoot density should drive any changes of biomass and productivity of C. nodosa as depth increases. The processes by which this reduction of C. nodosa abundance with depth occur remain to be elucidated. 相似文献
2.
Mónica M. Vergara Florencia Fagalde Jan Fiedler Monika Sieger 《Inorganica chimica acta》2010,363(1):163-2714
New diruthenium complexes (PPN)4[(NC)4Ru(μ-bptz)Ru(CN)4], (PPN)41, and [(bpy)2Ru(μ-bptz)Ru(CN)4], 2, (PPN+ = bis(triphenylphospine)iminium; bptz = 3,6-bis(2-pyridyl)-1,2,4,5-tetrazine; bpy = 2,2′-bipyridine), were synthesised and characterised by spectroscopic and electrochemical techniques. The comproportionation constant Kc = 107.0 of the mixed-valent species [(NC)4Ru(μ-bptz)Ru(CN)4]3− as obtained by oxidation of 14− in CH3CN is much lower than the Kc = 1015.0 previously detected for [(H3N)4Ru(bptz)Ru(NH3)4]5+, reflecting the competition between CN− and bptz for the π-electron density of the metals. Comparison with several other bptz-bridged diruthenium(II,III) complexes reveals an approximate correlation between Kc and the diminishing effective π acceptor capacity of the ancillary terminal ligands. In addition to the intense MLCT absorption at λmax = 624 nm, the main IVCT (intervalence charge transfer) band of 13− was detected by spectroelectrochemistry at λmax = 1695 nm (in CH3CN; ε = 3200 M−1 cm−1). The experimental band width at half-height, Δν1/2 = 2700 cm−1, is slightly smaller than the theoretical value Δν1/2 = 3660 cm−1, calculated from the Hush approximation for Class II mixed-valent species. In agreement with comparatively moderate metal-metal coupling, the mixed-valent intermediate 13− was found to be EPR silent even at 4 K. The unsymmetrical mixed-valent complex [(bpy)2RuII(μ-bptz)RuIII(CN)4]+, obtained in situ by bromine oxidation of 2 in CH3CN/H2O, displays a broad NIR absorption originating from an IVCT transition at λmax = 1075 nm (ε ≈ 1000 M−1 cm−1, Δν1/2 ≈ 4000 cm−1). In addition, the lifetime of the excited-state of the mononuclear precursor complex [Ru(bptz)(CN)4]2− was measured in H2O by laser flash photolysis; the obtained value of τ = 19.6 ns reveals that bptz induces a metal-to-ligand electronic delocalisation effect intermediate between that induced by bpy and bpz (bpz = 2,2′-bipyrazine) in analogous tetracyanoruthenium complexes. 相似文献
3.
Ilka Schnfelder Jrg Gelbrecht Jrg Schnfelder Christian E. W. Steinberg 《Journal of phycology》2002,38(1):66-89
We explored statistical relationships between the composition of littoral diatom assemblages and 21 chemical and physical environmental variables in 69 lakes and 15 river sites in the lowland of northeastern Germany. Canonical correspondence analysis with single treatment and with forward selection of environmental variables was used to detect 11 important ecological variables (dissolved inorganic carbon [DIC], Na + , total phosphorus [TP], dissolved organic carbon [DOC], total nitrogen [TN], pH, oxygen saturation, dissolved iron, SO42 ? , NH4 + , soluble reactive silicium) and maximum water depth or Ca2 + or soluble reactive phosphorus that most independently explain major proportions of the total diatom variance among the habitats. Monte Carlo permutation tests showed that each contributed a significant additional proportion (P < 0.05) of the variance in species composition. Together, these 11 most important environmental variables explained 34% of the total variance in species composition among the sites and captured 73% of the explained variance from the full 21 parameters model. Weighted‐averaging regression and calibration of 304 indicator taxa with tolerance down‐weighting and classic deshrinking was used to develop transfer functions between littoral diatoms and DIC, pH, TP, TN, and Cl ? . The DOC:TP ratio was introduced and a weighted‐averaging model was developed to infer allochthonous DOC effects in freshwater ecosystems. This diatom‐DOC/TP model was significant (P < 0.001) and explained 7.6% of the total diatom variance among the sites, surpassing the inferential power of the diatom‐TP‐transfer function (7.3% explained variance). The root‐mean‐square errors of prediction of the models were estimated by jack‐knifing and were comparable with published data sets from surface sediment diatom samples. The data set of littoral diatoms and environmental variables allows use of the diatom‐environmental transfer functions in biomonitoring and paleolimnological approaches across a broad array of natural water resources (such as floodplains, flushed lakes, estuaries, shallow lakes) in the central European lowland ecoregion. 相似文献
4.
A diatom-phosphorus transfer function for shallow,eutrophic ponds in southeast England 总被引:18,自引:3,他引:18
Shallow ponds in southeast England are often eutrophic with high phosphorus concentrations. The aim of this study was to develop a diatom-phosphorus transfer function to enable past phosphorus levels in such waters to be inferred from the sediment record. A water chemistry survey of 123 randomly chosen, shallow, artificial ponds in southeast England was carried out. Principal components analysis (PCA) revealed that phosphorus was an important environmental variable. A subset of 31 sites was selected along a total phosphorus (TP) gradient (winter TP range 7–1123 µg 1-1), in order to explore the relationship between the surface-sediment diatom assemblages and the contemporary water chemistry using canonical correspondence analysis (CCA). Annual mean TP was the most significant variable in explaining the variance in the diatom species data.Weighted averaging (WA) regression and calibration techniques were used to generate a transfer function, enabling annual mean TP (range 25–646 µg 1-1) to be inferred from the diatom species TP optima of 102 common taxa in the dataset (r
2 = 0.79; RMSE = 0.161; RMSE(boot) = 0.279; n = 30). The model was applied to fossil diatom assemblages in a sediment core from Marsworth Reservoir, Hertfordshire, a Site of Special Scientific Interest (SSSI), with currently high TP levels of 476 µg 1-1, to reconstruct past epilimnetic annual mean TP concentrations.The study shows that artificial, shallow waters can be suitable for palaeolimnological research and that it is possible to reliably infer lake water TP using the WA technique, across a large range of phosphorus concentrations. This method has the potential to provide limnologists, conservationists and water quality managers with an estimate of pre-enrichment phosphorus concentrations and an indication of the onset and development of eutrophication at a site. This information is essential for lake management strategies and restoration programmes. 相似文献
5.
Quality assessment of natural raw materials and derived consumer products is often done using conventional analytical techniques such as liquid and gas chromatography which are expensive and time consuming. This paper reports on the use of vibrational spectroscopy techniques as possible alternatives for the rapid and inexpensive assessment of the quality of ‘buchu oil’ obtained from two South African species; Agathosma betulina and Agathosma crenulata belonging to the Rutaceae family. Samples of A. betulina (55) and A. crenulata (16) were collected from different natural localities and cultivation sites in South Africa. The essential oil was obtained by hydrodistillation and scanned on Near infrared (NIR), mid infrared (MIR) and Raman spectrometers. The spectral data obtained was processed using chemometric techniques and orthogonal partial least squares discriminant analysis (OPLS-DA) was used to clearly differentiate between A. betulina and A. crenulata. The OPLS-DA technique also proved to be a useful tool to identify wave regions that contain biomarkers (peaks) that contributed to the separation of the two species. The three spectroscopy techniques were also evaluated for their ability to accurately predict the percentage composition of seven major compounds that occur in A. betulina ‘buchu’ oil. Using GC–MS reference data, calibration models were developed for the MIR, NIR and Raman spectral data to predict/profile the major compounds in ‘buchu oil’. A comparison of the three spectroscopy techniques showed that MIR together with PLS algorithms produced the best model (R2X = 0.96; R2Y = 0.88 and Q2Ycum = 0.85) for the quantification of six of the seven major oil constituents. The MIR model showed high predictive power for pseudo-diosphenol (R2 = 0.97), isomenthone (R2 = 0.97), menthone (R2 = 0.90), limonene (R2 = 0.91), pulegone (R2 = 0.96) and diosphenol (R2 = 0.85). These results illustrate the potential of MIR spectroscopy as a rapid and inexpensive alternative to predict the major compounds in buchu oil. 相似文献
6.
Bimetallic copper(II) and zinc(II) complexes of acyclic Schiff base ligands derived from amino acids
Abdessamad Arbaoui Noelia M. Sanchez-Ballester David L. Hughes 《Inorganica chimica acta》2011,365(1):96-102
The acyclic Schiff-base ligands (2-(OH)-5-(R3)C6H2-1,3-(HCNC(R1)(R2)CO2H), derived from the dialdehyde 2-hydroxy-5-R-1,3-benzenedicarboxaldehyde (R = Me or t-Bu) and two equivalents of the amino acids glycine, 2,2-diphenylglycine or phenylalanine, have been reacted with the metal acetates M(OAc)2 (M = Cu, Zn) in the presence of triethylamine, affording the complexes [HNEt3][M2(CH3CO2)2(2-(O)-5-(t-Bu)C6H2-1,3-(HCNC(R1)(R2)CO2)2] (M = Cu, R1 = R2 = C6H5, R3 = Me (1); M = Zn, R1 = R2 = H, R3 = t-Bu (2); M = Zn, R1 = R2 = C6H5, R3 = t-Bu (3); M = Zn, R1 = H, R2 = CH2C6H5, R3 = t-Bu (4)) in good yields. The crystal structures of 1·MeCN, 2·, 3·2MeOH, and 4·3MeOH have been determined. 相似文献
7.
Surface sediment diatom assemblages were examined from 26 freshwater sites near Isachsen (78°47N, 103°32W), Ellef Ringnes Island, a region of diverse and atypical water chemistry for high arctic sites. One hundred and sixty eight diatom taxa were identified from these samples, over 50% of which had not previously been recorded in the Canadian High Arctic. Variations in diatom assemblages were related to changes in measured environmental variables using multivariate techniques. Canonical correspondence analysis (CCA) indicated that five variables contributed significantly to explaining patterns of diatom variation (i.e., COND, DIC, Mn, TPF, TPU). The first CCA axis (=0.44) was primarily controlled by conductivity-related variables, while CCA axis 2 (=0.21) was related to particulate concentrations. Diatom-based inference models were generated for the reconstruction of conductivity (RMSEPjack=0.32, r2jack=0.76) and pH (RMSEPjack=0.40, r2jack=0.69). The strengths of these models indicate that it will be possible to reliably infer past trends in conductivity and pH from diatom assemblages preserved in dated sediment cores from the Isachsen region. 相似文献
8.
The redox-active doubly bridged species [{Mo(NO)(TpMe2)Q}2] [TpMe2 = tris(3,5-dimethylpyrazol-1-yl)hydroborate, Q = O(CH2)nO, n = 3, 5, or OCH2(CF2)n−2CH2O, n = 5, 6], and a chelate complex [Mo(NO)-(TpMe2)O(CH2)5O] were prepared and characterised by elemental and mass analyses, 1H NMR and IR spectroscopy. The bimetallic species with C3, C5, and C5(F) bridges exhibit two well-resolved reduction processes in their cyclic voltammograms (ΔE1/2 values of 290, 170, and 170 mV, respectively). These results indicate that the presence of the second bridge increases the extent of electrochemical interactions (by ca. 90-130 mV) in comparison with their singly bridged analogues. All non-fluorinated and the chelate species were catalytically active in cathodic reduction of chloroform. 相似文献
9.
Claudio Pettinari Fabio Marchetti Alessandro Marinelli Anna Bellusci 《Inorganica chimica acta》2009,362(12):4593-3227
The sterically hindered tetrakis-(3-(p-tolylpyrazolyl)borate [pz0Tpp-Tol] has been prepared and its reaction with CuX2.nH2O (X = Cl or acetate (OAc), M(NO3)2.6H2O (M = Ni, or Co) and MCl2 (M = Zn or Cd) has been investigated. [M(pz0Tpp-Tol)X(Hpzp-Tol)] (M = Cu, X = Cl or OAc; M = Ni or Co, X = NO3) and [M(pz0Tpp-Tol)Cl(Hpzp-Tol)2-n(H2O)n] have been synthesised and their spectroscopic properties described, the five-coordinated Cu species being also structurally characterized. The methyl groups in the para-tolyl fragments of the ligand strongly influences the stoichiometry and structure of the metal complexes. 相似文献
10.
Sergey S. Karlov Anastasia A. Selina Yuri F. Oprunenko Victor A. Tafeenko Judith A.K. Howard 《Inorganica chimica acta》2007,360(2):563-578
A new series of mono- and diphenylsubstituted silatranes and boratranes N(CH2CH2O)2(CHR3CR1R2O)MZ (M = Si, Z = CH2Cl, CCPh, H, OMenth, R1, R2, R3 = H, Ph; M = B, Z = nothing, R1, R2, R3 = H, Ph) have been synthesized. Both transalkoxylation and stepwise modification of a preformed metallatrane skeleton were used. The chloromethyl derivatives N(CH2CH2O)2(CHRCHRO)SiCH2Cl (R = H, Ph) react with tert-BuOK under intramolecular cycle expansion to give 1-tert-butoxy-2-carba-3-oxahomosilatranes N(CH2CH2O)(CH2CH2OCH2)(CHRCHRO)SiOtBu (R = H, Ph). The treatment of boratranes N(CH2CH2O)2(CH2CR1R2O)B (R1,R2 = H, Ph) with triflic acid and trimethylsilyl triflate results in the products of electrophilic attack at the nitrogen atom. The molecular structures of four silatranes and one boratrane bearing phenyl groups in the atrane skeleton were determined by the X-ray structure analysis. 相似文献
11.
Reaction of [(p-cymene)RuCl2(PPh3)] (1) or [Cp∗MCl2(PPh3)] (Cp∗ = C5Me5) (3a: M = Rh; 4a: M = Ir) with 1-alkynes and PPh3 were carried out in the presence of KPF6, generating the corresponding alkenyl-phosphonio complexes, [(p-cymene)RuCl(PPh3){CHCR(PPh3)}](PF6) (2a: R = Ph; 2b: R = p-tolyl) or [Cp∗MCl(PPh3){CHCPh(PPh3)}](PF6) (5: M = Rh; 6: M = Ir). Similar reactions of complexes [Cp∗RhCl2(L1)] (3a: L1 = PPh3; 3c: L1 = P(OMe)3) with L2 (L2 = PPh3, PMePh2, P(OMe)3) gave [Cp∗RhCl(L1)(L2)](PF6) (7bb: L1 = L2 = PMePh2; 7ca: L1 = P(OMe)3, L2 = PPh3; 7cc: L1 = L2 = P(OMe)3). Alkenyl-phosphonio complex 5 was treated with P(OMe)3 or 2,6-xylyl isocyanide, affording [Cp∗RhCl(L){CHCPh(PPh3)}](PF6) (8a: L = P(OMe)3; 8b: L = 2,6-xylNC). X-ray structural analyses of 2a, 6 and 8a revealed that the phosphonium moiety bonded to the Cβ atom of the alkenyl group are E configuration. 相似文献
12.
Adriana Lorenzotti Claudio Pettinari Brian W. Skelton 《Inorganica chimica acta》2005,358(11):3190-3200
New silver(I) acylpyrazolonate derivatives [Ag(Q)], [Ag(Q)(PR3)]2 and [Ag(Q)(PR3)2] (HQ = 1-R1-3-methyl-4-R2(CO)pyrazol-5-one, HQBn = R1 = C6H5, R2 = CH2C6H5; HQCHPh2 = R1 = C6H5, R2 = CH(C6H5)2; HQnPe = R1 = C6H5, R2 = CH2C(CH3)3; HQtBu = R1 = C6H5, R2 = C(CH3)3; HQfMe = R1 = C6H4-p-CF3, R2 = CF3; HQfEt = R1 = C6H5, R2 = CF2CF3; R = Ph or iBu) have been synthesized and characterized in the solid state and solution. The crystal structure of 1-(4-trifluoromethylphenyl)-3-methyl-5-pyrazolone, the precursor of proligand HQfMe and of derivatives [Ag(QnPe)(PPh3)2] and [Ag(QnPe)(PiBu3)]2 have been investigated. [Ag(QnPe)(PPh3)2] is a mononuclear compound with a silver atom in a tetrahedrally distorted AgO2P2 environment, whereas [Ag(QnPe)(PiBu3)]2 is a dinuclear compound with two O2N-exotridentate bridging acylpyrazolonate ligands connecting both silver atoms, their coordination environment being completed by a phosphine ligand. 相似文献
13.
A competition method is proposed to determine the complexation constants between At(I) and At(III) species and complexing agents. The method, tested with an inorganic ligand, thiocyanate ion (SCN−), and an organic macromolecule, thiacalix[4]arenetetrasulfonate (LH4) is based on solid/liquid separation or liquid/liquid extraction. For the solid/liquid separation, the cationic exchanger Dowex 50X8 was used. The interaction of At(I) and At(III) with the cationic exchanger is specific but could not be described by the expected cation exchange process. Most probably, At(I, III) interacts with a “strong” site (in weak amount) to form a surface complex at the surface of the resin organic skeleton. For the liquid/liquid separation, chloroform, toluene and hexane were used. All solvents extract astatine species with distribution coefficients varying between 0.7 and 120. The extraction process was shown to be independent of aqueous phase characteristics (pH, ionic strength) and was explained by the solvation of astatine species by the organic solvent. The effect of the addition of the thiacalix[4]arenetetrasulfonate on the solid/liquid or liquid/liquid distribution coefficients could be well described by the formation of a 1:1 complex with stability constants of log β1 = 4.5 ± 0.4 and 3.3 ± 0.3 for At(I) and At(III), respectively. For the thiocyanate ion, the data measured in the presence of the organic solvents could be explained by the formation of both 1:1 and 1:2 At:SCN complexes. In the case of the solid/liquid separation, data analysis was hampered by the probable formation of a ternary complex between At(I, III), SCN− and the functional groups of the resin. As for the calixarene, the interaction strength appeared slightly higher for At(I) (log β2 = 5.9 ± 0.3 and log β1 = 3.8 ± 0.2 for 1:2 and 1:1 complexed species, respectively) than for At(III) (log β2 = 5.3 ± 0.2 and log β1 = 2.8 ± 0.2 for 1:2 and 1:1 complexed species, respectively). 相似文献
14.
Ring coupled bimetallic derivatives (μ-η5:5-C5H4C5H4)[Nb(CO)4]2 and [μ-CH2(η5-C5H4)2][M(CO)4]2, where M = Nb and Ta have been prepared. The molecular structures of the latter two compounds have been determined: , triclinic, , a = 8.028(2) Å, b = 11.414(1) Å, c = 12.711(2) Å, α = 75.020(8)°, β = 80.34(2)°, γ = 79.46(2)°, V = 1097.3(4) Å3, Z = 2, R(F) = 2.79%; [μ-CH2(η5-C5H4)2][Ta(CO)4]2, triclinic, , a = 7.815(3) Å, b = 10.275(4) Å, c = 13.135(4) Å, α = 104.25(3)°, β = 100.26(4)°, γ = 96.86(3)°, V = 991.2(6) Å3, Z = 2, R(F) = 3.00%. 相似文献
15.
Wu Xu Julie A. Craft Marion Barens Jörg H. Albering Salah S. Massoud 《Inorganica chimica acta》2011,373(1):159-648
[M(TPA)Cl]ClO4·nH2O complexes (1: M = CoII, n = 0; 2: M = CuII, n = ½; 3: M = ZnII, n = 0) where TPA = tris(2-pyridylmethyl)amine, were synthesized and structurally characterized. The molecular structure of [Cu(TPA)Cl]ClO4·½H2O was determined by single crystal X-ray crystallography. In aqueous solution, the complex ions [M(TPA)Cl]+ (M = CoII or CuII) are hydrolyzed to the corresponding aqua species [M(TPA)(H2O)]2+. In contrast to the TBP [Cu(TPA)(H2O)]2+, the corresponding TBP cobalt(II) species showed severe distortion towards tetrahedral geometry. The interactions of the three complexes with DNA have been investigated at pH 7.0 (1.0 mM Tris-Cl buffer) and 37 °C. Significant DNA cleavages were obtained for complexes 1 and 2, whereas complex 3 did not show any detectable cleavage for DNA. Under pseudo Michaelis-Menten kinetic conditions, the kinetic parameters kcat and KM were determined as kcat = 6.59 h−1 and KM = 2.20 × 10−4 M for 1 and the corresponding parameters for 2 are kcat = 5.7 × 10−2 h−1 and KM = 6.9 × 10−5 M, and the reactivity of the complexes in promoting the cleavage of DNA decreases in the order 1 > 2 ? 3. The rate enhancements for the DNA cleavage by 1 and 2 correspond to 1.8 × 108 and 1.6 × 106, respectively, over the non-catalyzed DNA. The reactivity of the two complexes was discussed in relation to other related artificial nucleases. 相似文献
16.
Marcus J. CalkinsP. Hemachandra Reddy 《生物化学与生物物理学报:疾病的分子基础》2011,1812(9):1182-1189
The purpose of our study was to assess mitochondrial biogenesis and distribution in murine primary neurons. Using 5-bromo-2-deoxyuridine (BrdU) incorporation and primary neurons, we studied the mitochondrial biogenesis and mitochondrial distribution in hippocampal neurons from amyloid beta precursor protein (AβPP) transgenic mice and wild-type (WT) neurons treated with oxidative stressors, rotenone and H2O2. We found that after 20 h of labeling, BrdU incorporation was specific to porin-positive mitochondria. The proportion of mitochondrial area labeled with BrdU was 40.3 ± 6.3% at 20 h. The number of mitochondria with newly synthesized DNA was higher in AβPP neuronal cell bodies than in the cell bodies of WT neurons (AβPP, 45.23 ± 2.67 BrdU-positive/cell body; WT, 32.92 ± 2.49 BrdU-positive/cell body; p = 0.005). In neurites, the number of BrdU-positive mitochondria decreased in AβPP cultures compared to WT neurons (AβPP, 0.105 ± 0.008 BrdU-positive/μm neurite; WT, 0.220 ± 0.036 BrdU-positive/μm neurite; p = 0.010). Further, BrdU in the cell body increased when neurons were treated with low doses of H2O2 (49.6 ± 2.7 BrdU-positive/cell body, p = 0.0002 compared to untreated cells), while the neurites showed decreased BrdU staining (0.122 ± 0.010 BrdU-positive/μm neurite, p = 0.005 compared to the untreated). BrdU labeling was increased in the cell body under rotenone treatment. Additionally, under rotenone treatment, the content of BrdU labeling decreased in neurites. These findings suggest that Aβ and mitochondrial toxins enhance mitochondrial fragmentation in the cell body, and may cause impaired axonal transport of mitochondria leading to synaptic degeneration. 相似文献
17.
Veiko Uri Krista LõhmusÜlo Mander Ivika OstonenJürgen Aosaar Martin MaddisonHeljä-Sisko Helmisaari Jürgen Augustin 《Ecological Engineering》2011,37(6):920-930
Short-rotation energy forestry is one of the potential ways for management of abandoned agricultural areas. It helps sequestrate carbon and mitigate human-induced climate changes. Owing to symbiotic dinitrogen (N2) fixation by actinomycetes and the soil fertilizing capacity and fast biomass growth of grey alders, the latter can be suitable species for short-rotation forestry. In our study of a young grey alder stand (Alnus incana (L.) Moench) on abandoned arable land in Estonia we tested the following hypotheses: (1) afforestation of abandoned agricultural land by grey alder significantly affects the soil nitrogen (N) status already during the first rotation period; (2) input of symbiotic fixation covers an essential part of the plant annual N demand of the stand; (3) despite a considerable N input into the ecosystem of a young alder stand, there will occur no significant environmental hazards (N leaching or N2O emissions). The first two hypotheses can be accepted: there was a significant increase in N and C content in the topsoil (from 0.11 to 0.14%, and from 1.4 to 1.7%, respectively), and N fixation (151.5 kg N ha−1 yr−1) covered about 74% of the annual N demand of the stand. The third hypothesis met support as well: N2O emissions (0.5 kg N ha−1 yr−1) were low, while most of the annual gaseous N losses were in the form of N2 (73.8 kg N ha−1 yr−1). Annual average NO3-N leaching was 15 kg N ha−1 yr−1 but the N that leached from topsoil accumulated in deeper soil layers. The soil acidifying effect of alders was clearly evident; during the 14-year period soil acidity increased 1.3 units in the upper 0-10 cm topsoil layer. 相似文献
18.
The binuclear mixed valence copper(I/II) compound [CuI(CN)3CuII(tn)2] (1) (tn = propane-1,3-diamine) and its acetonitrile adduct [CuI(CN)3CuII(tn)2] · 2MeCN (2) have been synthesized. Complex 1 crystallizes triclinic, space group , a = 8.117(2) Å, b = 8.389(2) Å, c = 11.920(2) Å, α = 108.728(3)°, β = 100.024(3)°, γ = 104.888(4)°, Z = 2, and compound 2 monoclinic, space group P21/m, a = 8.752(2) Å, b = 13.243(3) Å, c = 9.549(2) Å, β = 114.678(4)°, Z = 2. In both crystal structures, the binuclear [CuI(CN)3CuII(tn)2] complex with slightly different bonding geometries is formed. One of the three nitrogen atoms of a CuI(CN)3 moiety is coordinated to Cu(II) at the apex of a square-pyramid with two chelating ligands tn on its base. The shortest intramolecular CuII?CuII distance in 1 is 5.640(7) Å. The EPR behaviour of 1 has been investigated at room temperature and at 77 K. The magnetic properties were measured in the temperature range 1.8-300 K. 相似文献
19.
Subal Chandra Manna Ennio Zangrando Nirmalendu Ray Chaudhuri 《Inorganica chimica acta》2007,360(8):2589-2597
The complexes [Cu2(ox)(phen)2(H2O)2](NO3)2 (1), [Cu2(sq)(pmdien)2(H2O)2](ClO4)2 (2) and {[Cu3(pdc)3(4,4′-bipy)1.5(H2O)2.25] · 2.5(H2O)}n (3) [phen = 1,10-phenanthroline; pmdien = N,N,N′,N′,N″-pentamethyldiethylenetriamine; 4,4′-bipy = 4,4′-bipyridine; ox = oxalate dianion; sq = squarate dianion and pdc = pyridine 2,6-dicarboxylate] have been synthesized and characterized by X-ray single crystal structure determination, low temperature magnetic measurement and thermal study. Structure determination reveals that 1 and 2 are dinuclear copper(II) complexes bridged by oxalate and squarate dianions, respectively, while 3 is a hexanuclear species formed by three Cu(pdc)(H2O)-(4,4′-bipy)-Cu(pdc)(H2O) fragments, connected through long Cu-O(pdc) bonds in a centrosymmetric arrangement. In complex 1 H-bonds occurring between the coordinated water molecules and lattice nitrate anions result in eight-membered ring clusters with the concomitant formation of 1D supramolecular chain. The adjacent chains undergo π-π stacking forming a 2D architecture. In the crystal of 3 an extensive H-bonding scheme gives rise to a 3D supramolecular network. Low temperature magnetic study shows a strong antiferromagnetic coupling in 1 (J = −288 ± 2 cm−1, g = 2.21 ± 0.01, R = 1.2 × 10−6); and a very weak interaction in 2 and 3, the best-fit parameters being: J = −0.21 cm−1, g = 2.12 ± 0.01, R = 1.1 × 10−6 (2) and J = −1.34 cm−1 ± 0.1, g = 2.14 ± 0.01, R = 1.2 × 10−6 (3) (R defines as . 相似文献
20.
Fabio Marchetti Claudio Pettinari Augusto Cingolani Vyacheslav Vertlib 《Inorganica chimica acta》2005,358(6):1955-1962
New Ba acylpyrazolonate derivatives of formula [Ba(Q)2(tetraglyme)] (HQ = HQtbu = 1-Ph-3-Me-4-C(O)CH2But-5-pyrazolone; tetraglyme = 2,5,8,11,14-pentaoxapentadecane), [Ba(Q)2(tmeda)2] (HQ = HQtbu or HQpiv, where HQpiv = 1-Ph-3-Me-4-C(O)But-5-pyrazolone; tmeda = N,N,N′,N′-tetramethylethylenediamine), [Ba(Q)2(pmdien)(H2O)] (HQ = HQtbu or HQpiv; pmdien = N,N,N′,N″,N″-pentamethyldiethylenetriamine) and [Ba(Q)2(pmdien)(Meim)] (HQ = HQtbu or HQpiv; Meim = 1-methylimidazole) have been synthesized and analytically and spectroscopically characterized. They are mononuclear air and solution stable compounds containing an eight-coordinated barium atom. The X-ray crystal structures of the hydrates [Ba(Qtbu)2(pmdien)(H2O)] and [Ba(Qpiv)2(pmdien)(H2O)] show the water molecule directly bonded to Ba and involved in intermolecular H-bonding network. In the X-ray crystal structure of [Ba(Qpiv)2(pmdien)(Meim)], the Meim ligand substitutes the water of previous derivatives and decreases the strength of intermolecular interactions, lowering the melting point. The derivative [Ba(Qtbu)2(pmdien)(NEt3)] has been prepared from interaction of [Ba(Qtbu)2(pmdien)(H2O)] with excess triethylamine in acetonitrile. 相似文献