High-temperature molecular magnets based on cyanovanadate building blocks: spontaneous magnetization at 230 k

The molecular-based magnetic materials Cs(2)Mn(||)[V(||)(CN)(6)] (1) and (Et(4)N)(0.5)Mn(l.25)- [V(CN)(5)].2H(2)O (2) (where Et is ethyl) were prepared by the addition of manganese(II) triflate to aqueous solutions of the hexacyanovanadate(II) ion at 0 degrees C. Whereas 1 crystallizes in a face-centered cubic lattice, 2 crystallizes in a noncubic space group. The cesium salt (1) has features characteristic of a three-dimensional ferrimagnet with a Néel transition at 125 kelvin. The tetraethylammonium salt (2) also behaves as a three-dimensional ferrimagnet with a Néel temperature of 230 kelvin; only two other molecular magnets have higher magnetic ordering temperatures. Saturation magnetization measurements indicate that in both compounds the V(II) and high-spin Mn(II) centers are antiferromagnetically coupled. Both 1 and 2 exhibit hysteresis loops characteristic of soft magnets below their magnetic phase-transition temperatures. The high magnetic ordering temperatures of these cyano-bridged solids confirm that the incorporation of early transition elements into the lattice promotes stronger magnetic coupling by enhancing the backbonding into the cyanide pi* orbitals.     

High-Tc Molecular-Based Magnets: Ferrimagnetic Mixed-Valence Chromium(III)-Chromium(II) Cyanides with Tc at 240 and 190 Kelvin

Molecular-based magnets with high magnetic-ordering temperatures, T(c), can be obtained by mild chemistry methods by focusing on the bimetallic and mixed-valence transition metal micro-cyanide of the Prussian blue family. A simple orbital model was used to predict the electronic structure of the metal ions required to achieve a high ordering temperature. The synthesis and magnetic properties of two compounds, [Cr(5)(CN)(12)].10H(2)O and Cs(0.75) [Cr(2.125)(CN)(6)].5H(2)O, which exhibited magnetic-ordering temperatures of 240 and 190 kelvin, respectively, are reported, together with the strategy for further work.     

A molecular-based magnet with a fully interlocked three-dimensional structure

A compound has been synthesized with the formula (rad)(2)Mn(2)[Cu(opba)](3)(DMSO)(2).2H(2)O, where rad(+) is 2-(4-N-methylpyridinium)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, opba is orthophenylenebis(oxamato), and DMSO is dimethyl sulfoxide. It consists of two nearly perpendicular graphite-like networks with edge-sharing Mn(II)(6)Cu(II)(6) hexagons. The two networks are fully interlocked with the same topological relationship as that between adjacent rings of a necklace. The compound has three kinds of spin carriers: Mn(II) and Cu(II) ions, antiferromagnetically coupled through oxamato bridges, and rad(+) radical cations, bridging the Cu(II) ions through the nitronyl nitroxide groups and forming Cu-rad chains. The temperature dependence of the magnetization reveals that below 22.5 K, the compound behaves as a magnet.     

镁钾配施对寒地水稻产量的影响

[目的]研究镁钾配施对寒地水稻(Oryza sativa L.)产量的影响,以确定适宜的镁钾配比量。[方法]以空育131为材料,按照随机区组设计,研究镁肥、钾肥对水稻产量的影响,并探明镁肥、钾肥最佳施用比例。[结果]在高中低施钾区,按照七水硫酸镁与氧化钾1∶1(钾肥165.0 kg/hm2,镁肥100.5 kg/hm2)或者1∶2(钾肥276.0 kg/hm2,镁肥100.5 kg/hm2)的重量比配施,能够在水稻关键生育时期合理增加水稻叶片氮含量;按照七水硫酸镁与氧化钾1∶2的重量比配施,能够保持群体叶面积指数趋于合理,不发生早衰和贪青现象;按照七水硫酸镁配施比例与氧化钾2∶1(钾肥165.0 kg/hm2,镁肥201.0 kg/hm2)的重量比配施,能够通过增加穗数和结实率提高产量,产量为9 660 kg/hm2。[结论]该研究对于保持土壤养分平衡,进一步增加水稻产量和改善稻米品质,促进水稻产业可持续发展具有深远意义。     

An Inorganic Double Helix: Hydrothermal Synthesis, Structure, and Magnetism of Chiral [(CH3)2NH2]K4[V10O10(H2O)2(OH)4(PO4)7]{middle dot}4H2O

Very complicated inorganic solids can be self-assembled from structurally simple precursors as illustrated by the hydrothermal synthesis of the vanadium phosphate, [(CH(3))(2)NH(2)]K(4)[V(10)O(10)(H(2)O)(2)(OH)(4)(PO(4))(7)].4H(2)O, 1, which contains chiral double helices formed from interpenetrating spirals of vanadium oxo pentamers bonded together by P(5+). These double helices are in turn intertwined with each other in a manner that generates unusual tunnels and cavities that are filled with (CH(3))(2)NH(2)(+) and K(+) cations, respectively. The unit cell contents of dark blue phosphate 1, which crystallizes in the enantiomorphic space group P4(3) with lattice constants a = 12.130 and c = 30.555 angstroms, are chiral; only one enantiomorph is present in a given crystal. Magnetization measurements show that 1 is paramagnetic with ten unpaired electrons per formula unit at higher temperatures and that antiferromagnetic interactions develop at lower temperatures.     

Interwoven metal-organic framework on a periodic minimal surface with extra-large pores

Interpenetration (catenation) has long been considered a major impediment in the achievement of stable and porous crystalline structures. A strategy for the design of highly porous and structurally stable networks makes use of metal-organic building blocks that can be assembled on a triply periodic P-minimal geometric surface to produce structures that are interpenetrating-more accurately considered as interwoven. We used 4,4',4"-benzene-1,3,5-triyl-tribenzoic acid (H(3)BTB), copper(II) nitrate, and N,N'-dimethylformamide (DMF) to prepare Cu(3)(BTB)(2)(H(2)O)(3).(DMF)(9)(H(2)O)(2) (MOF-14), whose structure reveals a pair of interwoven metal-organic frameworks that are mutually reinforced. The structure contains remarkably large pores, 16.4 angstroms in diameter, in which voluminous amounts of gases and organic solvents can be reversibly sorbed.     

解钾菌解钾效率检测方法的比较

以中慢生根瘤菌S-15和类芽胞杆菌S-17作为供试菌株,采用细胞破碎、NH4OAc浸提、H2O2溶液消煮及不作任何前处理等4种方法,利用火焰光度计检测解钾菌发酵液中K+含量,并计算解钾菌在培养基中的解钾效率。结果表明,配制的3种钾系列标准溶液所绘制的钾标准曲线较为接近,R2分别高达0.994 4、0.9997、0.999 8。采用H2O2消煮后所测得的K+浓度最高,2株解钾菌的解钾效率分别达到101.1%、125.1%,与其他处理组之间有显著性差异。用H2O2溶液处理所得到的解钾率更能真实反映解钾菌的解钾作用。     

植株叶片全钾简易快速测定方法研究

分别用１ｍｏｌ／ＬＮＨ４ＯＡＣ、１．０８０ｍｏｌ／ＬＨ２ＳＯ４和Ｈ２Ｏ浸提植株叶片中的钾,然后用火焰光度法测定,测定结果与Ｈ２ＳＯ４－Ｈ２Ｏ２消煮法作比较结果表明：１ｍｏｌ＝Ｌ ＮＨ４ＯＡＣ、１．０８０ｍｏｌ／Ｌ Ｈ２ＳＯ４作浸提剂的测定结果与Ｈ２ＳＯ４－Ｈ２Ｏ２消煮法测定结果差异不显著;１５、３０和４５ｍｉｎ３种浸提时间的测定结果差异不显著;以稀Ｈ２Ｓ巡提剂,硫酸浓度分别为０．９００、０．９７２     

靖远县沿黄灌区春玉米平衡施肥研究

研究了氮、磷、钾肥用量对靖远县沿黄灌区春玉米经济性状与产量的影响,建立了氮肥（X1）、磷肥（X2）和钾肥（X3）与春玉米产量（Y）之间的回归方程。通过对回归方程优化解析,得出春玉米最佳施肥量为N365．25kg／hm^2、P2O576．96kg／hm^2,K2O103．50kg／hm^2,玉米产量可达15545,40kg／hm^2;最佳经济施肥量为N328．65kg／hm^2、P2O587．60kg／hm^2、K2O112．35kg／hm^2,玉米产量可达15532．50kg／hm^2。     

基质栽培营养液氮磷钾补充水平对番茄养分吸收及产量品质影响

温室条件下,采用基质袋式栽培方式(长12.7 m、宽30 cm、高20 cm),通过改变营养液KNO_3与NH_4H_2PO_4含量得到4个不同营养液氮磷钾补充水平,各处理物质的量浓度比分别为:CK为Ca(NO_3)_2·4H_2O:KNO_3:NH_4H_2PO_4:MgSO_4·7H_2O=4.00:6.00:1.00:2.00,T1为Ca(NO_3)_2·4H_2O:KNO_3:NH_4H_2PO_4:MgSO_4·7H_2O=4.00:4.00:0.80:2.00,T2 为Ca(NO_3)_2·4H_2O:KNO_3:NH_4H_2PO_4:MgSO_4·7H2O=4.00:8.00:1.20:2.00,T3 为Ca(NO_3)2·4H_2O:KNsdfO_3:NH_4H_2PO_4: MgSO_4·7H_2O=4.00:10.00:1.40:2.00;研究营养液氮磷钾补充水平对基质栽培番茄品质、产量及养分吸收利用影响。结果表明,提高营养液氮磷钾水平可促进番茄各器官对氮磷钾吸收,超量施用抑制氮磷钾吸收;果实可溶性蛋白、维生素C、还原糖、可溶性总糖含量均随营养液氮磷钾补充水平提高呈先增后降趋势,而可溶性固形物与硝酸盐含量逐渐增加;各处理间单果重、产量差异显著;与CK相比,T2单果重增加6.85%、产量增加13.10%,T3单果重减少2.29%、产量减少2.92%,且存在显著差异。综合考虑番茄养分吸收利用、品质和产量等因素,在试验条件下,T2处理营养液氮磷钾补充水平最佳,推荐用量为:KNO3 8 mmol·L~(-1)、NH_4H_2PO_4 1.2 mmol·L~(-1)、Ca(NO_3)_2 ·4H_2O_4 mmol·L~(-1)、MgSO_4·7H_2O_2 mmol·L~(-1)。     

Oxygen binding in cyanmet hybrid and normal hemoglobins: applicability of sequential and two-state concerted models

The cyanmet hybrid hemoglobins alpha(2)beta(+CN)(2) and alpha(+CN)(2)beta(2) are widely held to be similar or equivalent in structure and subunit interactions to the partially oxygen-liganded species alpha(2)(beta * O(2))(2) and (alpha * O(2))(2)beta(2), respectively. An analysis of precise data on oxygen binding to the cyanmet hybrids and normal hemoglobin shows that if this is the case, then cooperative ligand binding in hemoglobin is more properly described by some model of the sequential type than by any twostate concerted model.     

渭北苹果不同形态钾与水交互作用及品质效应研究

1997～ 1998年对渭北旱塬红富士苹果不同形态钾与水的交互作用、品质效应及耦合模型进行了研究。根据试验测定结果建立了红富士苹果产量、一级果占有率、>80 %果面红色果占有率、可溶性固形物浓度与KCl,K2 SO4 ,H2 O3因素之间的函数模型。通过主因素分析得出各因素对产量及品质的影响顺序为产量 (y1 ) :x3(H2 O) >x2 (K2 SO4 ) >x1 (KCl) ;一级果占有率 (y2 ) :x3(H2 O) >x2 (K2 SO4 ) >x1 (KCl) ;>80 %果面红色果占有率(y3) :x2 (K2 SO4 ) >x1 (KCl) >x3(H2 O) ;可溶性固形物浓度 (y4 ) :x2 (K2 SO4 ) >x1 (KCl) >x3(H2 O)。并对渭北旱塬红富士苹果不同形态钾与水交互作用及品质效应规律进行了综合研究     

Structure of a three-dimensional, microporous molybdenum phosphate with large cavities

The synthesis, single-crystal x-ray structural characterization, and sorption properties of a microporous molybdenum phosphate, (Me(4)N)(1.3)(H(3)O)(0.7)[Mo(4)O(8)(PO(4))(2)] . 2H(2)O (Me, methyl), are presented. The three-dimensional framework is built up from Mo(4)O(8)(4+) cubes and PO(4)(3-) tetrahedra that are connected in such a way that large, cation-filled voids are generated; these voids constitute 25% of the volume of the solid. Absorption isotherms for water show the completely reversible uptake of 4 to 5 percent by weight water into the micropores of this compound, which corresponds to 10 to 12 percent by volume.     

Pentaborate Polyanion in the Crystal Structure of Ulexite, NaCaB5O6(OH)6{middle dot}5H2O

Triclinic ulexite crystals contain isolated borate polyanions [B(5)O(6)(OH)(6)](3-) related to the well known pentaborate polyanion [B(5)O(6)(OH)(4)](-) by addition of two hydroxyl groups to two opposite B-O triangles. The isolated ulexite polyanions form the [B(5)O(7)(OH)(4)](n)(3n-) chains previously found in crystals of the related mineral probertite, NaCaB(5)O(7)(OH)(4).3H(2)O.     

Crystal Structure of Kernite, Na2B4O6(OH)2 {middle dot} 3H2

Kernite, Na(2)B(4)O(6)(OH)(2). .3H(2)0, contains parallel infinite chains of the borate polyanion[B(4)O(6)(OH)(2)](n)(2n-). The chains are composed of six-membered rings containing one boron-oxygen triangle and two boron-oxygen tetrahedra. The rings are linked through commonly shared boron-oxygen tetrahedra.     

The magnon pairing mechanism of superconductivity in cuprate ceramics

The magnon pairing mechanism is derived to explain the high-temperature superconductivity of both the La2-xSrxCu(1)O(4) and Y(1)Ba(2)Cu(3)O(7) systems. Critical features include (i) a one- or two-dimensional lattice of linear Cu-O-Cu bonds that contribute to large antiferromagnetic (superexchange) coupling of the Cu(II)(d(9)) orbitals; (ii) holes in the oxygen ppi bands [rather than Cu(III)(d(8))] leading to high mobility hole conduction; and (iii) strong ferromagnetic coupling between oxygen ppi holes and adjacent Cu(II)(d(9)) electrons. The ferromagnetic coupling of the conduction electrons with copper d spins induces the attractive interaction responsible for the superconductivity, leading to triplet-coupled pairs called "tripgems." The disordered Heisenberg lattice of antiferromagnetically coupled copper d spins serves a role analogous to the phonons in a conventional system. This leads to a maximum transition temperature of about 200 K. For La(1.85)Sr(0.15)Cu(1)O(4), the energy gap is in excellent agreement with experiment. For Y(1)Ba(2)Cu(3)O(7), we find that both the CuO sheets and the CuO chains can contribute to the supercurrent.     

Evidence for a phytotoxic hydroxy-aluminum polymer in organic soil horizons

The toxicity of A1 that has been mobilized in soil, streams, and lakes through acid deposition primarily has been attributed to mononuclear A1 species. Polynuclear A1 species are more toxic than mononuclear species, but they have not been considered to be significant in the environment. Aluminum-27 nuclear magnetic resonance (NMR) spectra of forested spodosol soil horizon samples show the presence of polynuclear A1O(4)A1(12)(OH)(24)(H(2)O)(12)(7+). The AlO(4)A1(12)(OH)(24)(H(2)O)(12)(7+) species accounted for 30 percent of the aqueous A1 observable by NMR, and this could make a significant contribution to the toxicity of the A1 in these soils.     

The Effect of H2O on the 410-Kilometer Seismic Discontinuity

The 410-kilometer seismic discontinuity is generally considered to be caused by a phase transformation of the main constituent of the upper mantle, olivine, alpha-(Mg,Fe)(2)SiO(4), to beta-(Mg,Fe)(2)SiO(4). Recent data show that H(2)O dissolves in olivine and other nominally anhydrous mantle minerals and that the partitioning of H(2)O between olivine and beta-(Mg,Fe)(2)SiO(4) is about 1:10. Such behavior strongly affects the region over which the alpha to beta phase transformation occurs and hence the seismic discontinuity that results. The observed width of the discontinuity constrains the maximum H(2)O content of upper mantle olivine to about 200 parts per million by weight.     

Tuhualite crystal structure

As judged by crystal structure analysis, the crystallochemical formula of tuhualite is (Na,K)(2)(VI) (Fe(+3))(2)(VI) (Fe(+2))(2)(VI) Si(12)O(30) . H(2)O, with four such formulas in the unit cell. The structure is characterized by six-repeat double chains of silicon tetrahedrons and chains of edge-sharing, alternating iron tetrahedrons and octahedrons. Chains of each kind are connected by corner sharing to four chains of the other type. The iron cations appear to be anomalously ordered with Fe(+2) in tetrahedral and Fe(+3) in octahedral sites.     

A mercury-catalyzed, high-yield system for the oxidation of methane to methanol

A homogeneous system for the selective, catalytic oxidation of methane to methanol via methyl bisulfate is reported. The net reaction catalyzed by mercuric ions, Hg(II), is the oxidation of methane by concentrated sulfuric acid to produce methyl bisulfate, water, and sulfur dioxide. The reaction is efficient. At a methane conversion of 50 percent, 85 percent selectivity to methyl bisulfate ( approximately 43 percent yield; the major side product is carbon dioxide) was achieved at a molar productivity of 10(-7) mole per cubic centimeter per second and Hg(II) turnover frequency of 10(-3) per second. Separate hydrolysis of methyl bisulfate and reoxidation of the sulfur dioxide with air provides a potentially practical scheme for the oxidation of methane to methanol with molecular oxygen. The primary steps of the Hg(II)-catalyzed reaction were individually examined and the essential elements of the mechanism were identified. The Hg(II) ion reacts with methane by an electrophilic displacement mechanism to produce an observable species, CH(3)HgOSO(3)H, 1. Under the reaction conditions, 1 readily decomposes to CH(3)OSO(3)H and the reduced mercurous species, Hg(2)(2+) The catalytic cycle is completed by the reoxidation of Hg(2)(2+) with H(2)SO(4) to regenerate Hg(II) and byproducts SO(2) and H(2)O. Thallium(III), palladium(II), and the cations of platinum and gold also oxidize methane to methyl bisulfate in sulfuric acid.