Effect of La2O3-Dopant on Microstructure and Microwave Dielectric Properties of CaO-MgO-Nb2O5-TiO2 System Ceramics

With the development of microwave integratedsystem for wireless communication, requirements ofthe microwave device are combined with high dielec tric constants (εr), low dielectric losses (Q = 1/tanδ) and near zero temperature coefficient for stabili ty and frequency selectivity[1,2]. But it is hard to findmaterials that satisfy all above mentioned requiredcharacteristics. In general, a ceramic with a high di electric constant has a larger positive temperature coef fi…     

Preparation and photocatalytic activity of Fe3O4@SiO2@ZnO:La

In this study, Fe₃O₄@SiO₂@ZnO:La microspheres were successfully prepared. The microspheres have the advantages of both ZnO doped with La and the Fe₃O₄@SiO₂ structure such that the former improves the photocatalytic activity of ZnO and the latter can be reused. The X-ray diffraction (XRD), a field emission scanning electron microscope (SEM), a field emission transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), and a vibrating sample magnetometer (VSM) were used to characterize Fe₃O₄@SiO₂@ZnO:La microspheres. Methyl orange was used as the model molecule to study the effect of the Zn²⁺ concentration and the doping amount of La on the photocatalytic activity of Fe₃O₄@SiO₂@ZnO:La microspheres. Results show that in the synthesis of Fe₃O₄@SiO₂@ZnO:La microspheres, photocatalytic activity of the microspheres is enhanced first and weakened later with the increase of Zn²⁺ concentration. In the La doping process, the photocatalytic activity of Fe₃O₄@SiO₂@ZnO:La microspheres is enhanced with the increase in the La doping amount. The magnetic photocatalysts not only have high photocatalytic activity, but also can be reused. After being reused five times, the photocatalyst's degradation rate of methyl orange is still as high as 81%, which shows that magnetic photocatalysts have prospective wider applications in photocatalytic degradation of dye wastewater.     

Effects of La^3＋ on ATPase Activities of Plasma Membrane Vesicles Isolated from Casuarina Equisetifolia Seedlings under Acid Rain Stress

Asamainkindofmembranetransporter ,plasmamembraneATPasesfacilitatethetransportofminerals ,sugars,metabolites ,andothercompoundsacrossthemembraneofthecells ,onlybywhichcouldplantcellscommunicatewithenvironmenttotransfersubstanceandinformation ,whichisessentialforplantgrowthandcellularhomeostasis[1] .Astheexperimentmateri als ,thehighlypurifiedplasmamembranevesiclesfromCasuarinaequisetifoliaseedlingscultivatedunderartificialacidrainstress ,wereisolatedbyaqueoustwo-phasepartitioningmethods .Thest…     

镧对黑曲霉生理代谢的Hormesis效应

应用含有梯度外源镧(La)(0、16mg/L、64mg/L、256mg/L、512mg/L和1024 mg/L)的液体培养基培养黑曲霉,每间隔8h取样测定黑曲霉对还原糖和蛋白质的吸收和利用率。培养3天后,测定黑曲霉质膜三磷酸腺苷酶(ATPase),胞内乳酸脱氢酶(LDH)和淀粉酶活性,以及脂质过氧化产物(MDA)的变化。结果表明,在0～64mg/L外源La作用下,黑曲霉对还原糖和蛋白质的吸收与利用率、质膜Na+,K+-ATPase、Ca2+-ATPase、Mg2+-AT-Pase、胞内LDH酶和淀粉酶活性均随La3+的增加而升高,而MDA呈现下降趋势。在64mg/L～1024mg/L剂量范围内,上述生理指标则呈现相反的变化趋势。因此,La3+诱导了黑曲霉生理代谢的Hormesis效应。     

Properties of human hemoglobins with increased polarity in the alpha- or beta-heme pocket. Carbonmonoxy derivatives

The spectroscopic, conformational, and functional properties of mutant carbonmonoxy hemoglobins in which either the beta-globin Val67(E11) or the alpha-globin Val62(E11) is replaced by threonine have been investigated. The thermal evolution of the Soret absorption band and the stretching frequency of the bound CO were used to probe the stereodynamic properties of the heme pocket. The functional properties were investigated by kinetic measurements. The spectroscopic and functional data were related to the conformational properties through molecular analysis. The effects of this nonpolar-to-polar isosteric mutation are: (i) increase of heme pocket anharmonic motions, (ii) stabilization of the A0 conformer in the IR spectrum, (iii) increased CO dissociation rates. The spectroscopic data indicate that for the carbonmonoxy derivatives, the Val --> Thr mutation has a larger conformational effect on the beta-subunits than on the alpha-subunits. This is at variance with the deoxy derivatives where the conformational modification was larger in the heme pocket of the alpha-subunit (Cupane, A., Leone, M., Militello, V., Friedman, R. K., Koley, A. P., Vasquez, G. P., Brinigar, W. S., Karavitis, M., and Fronticelli, C. (1997) J. Biol. Chem. 272, 26271-26278). These effects are attributed to a different electrostatic interaction between Ogamma of Thr(E11) and the bound CO molecule. Molecular analysis indicates a more favorable interaction of the bound CO with Thr Ogamma in the beta-subunit heme pocket.     

Toxic Effects of Lanthanum, Cerium, Chromium and Zinc on Potamogeton Malaianus

iththerapiddevelopmentofrareearthindustryandextensiveapplicationofrareearthinagriculture ,agreatmanyofrareearthelements (REEs)werere leasedintoenvironment ,especiallywaterenviron ment ,andtheconsequentseriousenvironmentpollu tionhasattractedpeople′satten…     

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In order to accurately control the rare earth content in liquid steel in electroslag remelting (ESR) process, according to the ion and molecule coexistence theory (IMCT) of slag structure and corresponding phase diagrams, a thermodynamic calculating model for the evaluation of mass action concentrations (designated by Ni for structure unit i) for La2O3-Al2O3-CaF2 slag system was formulated. The results show that the calculated values of NLa2O3 are in good agreement with the reported measured values, indicating that this calculating model can wholly embody the characteristics of the slag system. The activity of La2O3 decreases with the increasing of the Al2O3 and CaF2 content, and Al2O3 is stronger than CaF2 in decreasing the activity of La2O3. But the activity of La2O3 increase with the increasing in temperature at the composition range of 30% La2O3, 20% Al2O3, 50% CaF2. Above all, the activity of La2O3 in La2O3-Al2O3-CaF2 slag system can be quantitatively analyzed by this thermodynamic model, and this model can provide a theoretical basis for precisely controlling the lanthanum content in molten steel in ESR process.     

Renewed interest in granulocyte transfusion therapy

The kinetics of the interaction of heme with hemopexin and albumin was monitored by measuring the time dependence of changes in the Soret absorption spectra. Since the protein binding sites can only bind heme monomers, the binding kinetics apparently reflected the slow dissociation of heme dimers, resulting from dimer/monomer equilibria in aqueous heme solutions. The dissociation of heme dimers is characterized by the rate constant of (3-4) x 10(-3) s(-1). The measurements further revealed significant differences in the kinetic profiles (slowing down the binding interaction) that were dependent on the storage time of heme solutions at room temperature. These presumably responded to the gradual formation of higher aggregates of heme, which cannot dissociate into dimers/monomers. Alternatively, partial autooxidation of heme molecules could increase the stability of heme dimers and obstruct specific binding of heme to the proteins.     

Calcium site specificity. Early Ca2+-related tight junction events

The molecular mechanisms by which Ca2+ and metal ions interact with the binding sites that modulate the tight junctions (TJs) have not been fully described. Metal ions were used as probes of these sites in the frog urinary bladder. Basolateral Ca2+ withdrawal induces the opening of the TJs, a process that is abruptly terminated when Ca2+ is readmitted, and is followed by a complete recovery of the TJ seal. Mg2+ and Ba2+ were incapable of keeping the TJ sealed or of inducing TJ recovery. In addition, Mg2+ causes a reversible concentration-dependent inhibition of the Ca2+-induced TJ recovery. The effects of extracellular Ca2+ manipulation on the TJs apparently is not mediated by changes of cytosolic Ca2+ concentration. The transition elements, Mn2+ and Cd2+, act as Ca2+ agonists. In the absence of Ca2+, they prevent TJ opening and almost immediately halt the process of TJ opening caused by Ca2+ withdrawal. In addition, Mn2+ promotes an almost complete recovery of the TJ seal. Cd2+, in spite of stabilizing the TJs in the closed state and halting TJ opening, does not promote TJ recovery, an effect that apparently results from a superimposed toxic effect that is markedly attenuated by the presence of Ca2+. The interruption of TJ opening caused by Ca2+, Cd2+, or Mn2+, and the stability they confer to the closed TJs, might result from the interaction of these ions with E-cadherin. Addition of La3+ (2 microM) to the basolateral Ca2+-containing solution causes an increase of TJ permeability that fully reverses when La3+ is removed. This effect of La3+, observed in the presence of Ca2+ (1 mM), indicates a high La3+ affinity for the Ca2+-binding sites. This ability of La3+ to open TJs in the presence of Ca2+ is a relevant aspect that must be considered when using La3+ in the evaluation of TJ permeability of epithelial and endothelial membranes, particularly when used during in vivo perfusion or in the absence of fixatives.     

Cr3+或V3+替代Mn3+对La0.4Ca0.6MnO3电荷有序相的影响

用固相反应法制备了La0.4 Ca0.6 Mn1 -xCrxO3(LCMCO)和La0.4Ca0.6Mn1-yVyO3 (LCMVO)(x,y=0.00,006,0.08)多晶样品.通过XRD、M-T曲线、ESR谱线,研究了Cr3+或V3+替代Mn3+对La0.4Ca0.6MnO3电荷有序相的影响.实验结果表明:电荷有序相随着Cr掺杂浓度的增加而被破坏,在LCMCO体系中电荷有序相几乎完全消失;而当V掺杂时,虽然电荷有序相随着V成分的增加会逐渐变弱,但电荷有序相依然存在于LCMVO体系中.用V3+替代Mn3+只是对于长程的电荷有序仅仅起了隔断的作用;用Cr3+替代Mn3+破坏了CE型反铁磁的自旋序从而引起电荷序的融化.从实验上证明了电荷序CE型反铁磁体系中,电荷序和自旋序存在强耦合相互作用.     

Altering substrate specificity at the heme edge of cytochrome c peroxidase

Two mutants of cytochrome c peroxidase (CCP) are reported which exhibit unique specificities toward oxidation of small substrates. Ala-147 in CCP is located near the delta-meso edge of the heme and along the solvent access channel through which H2O2 is thought to approach the active site. This residue was replaced with Met and Tyr to investigate the hypothesis that small molecule substrates are oxidized at the exposed delta-meso edge of the heme. X-ray crystallographic analyses confirm that the side chains of A147M and A147Y are positioned over the delta-meso heme position and might therefore modify small molecule access to the oxidized heme cofactor. Steady-state kinetic measurements show that cytochrome c oxidation is enhanced 3-fold for A147Y relative to wild type, while small molecule oxidation is altered to varying degrees depending on the substrate and mutant. For example, oxidation of phenols by A147Y is reduced to less than 20% relative to the wild-type enzyme, while Vmax/e for oxidation of other small molecules is less affected by either mutation. However, the "specificity" of aniline oxidation by A147M, i.e., (Vmax/e)/Km, is 43-fold higher than in wild-type enzyme, suggesting that a specific interaction for aniline has been introduced by the mutation. Stopped-flow kinetic data show that the restricted heme access in A147Y or A147M slows the reaction between the enzyme and H202, but not to an extent that it becomes rate limiting for the oxidation of the substrates examined. The rate constant for compound ES formation with A147Y is 2.5 times slower than wild-type CCP. These observations strongly support the suggestion that small molecule oxidations occur at sites on the enzyme distinct from those utilized by cytochrome c and that the specificity of small molecule oxidation can be significantly modulated by manipulating access to the heme edge. The results help to define the role of alternative electron transfer pathways in cytochrome c peroxidase and may have useful applications in improving the specificity of peroxidase with engineered function.     

Effects of Rare Earth Elements on Promoting Isoflavonoid Production andRelease of Pueraria Lobata Hairy Roots in Vitro

The effects of various rare earth elements on growth and isoflavonoid production in hairy root cultures of Pueraria lobata (Willd.) Ohwi (strain TR2) cultured in 500 ml flasks were studied. After 32 days of culture, the biomass of hairy roots increase 15 times and reach 3.2 g dry weight. Hairy root growth was inhibited by Y203, NaSeO3 and Sm^3 be-cause of brown formation. But significant promoting effect on root growth due to callus formation was observed in La^3 treatments. It is the most noteworthy that the production of total isoflavonoids and puerarin was enhanced greatly by La^3 treatment. A major portion of increased total isoflavonoids and puerarin was released into medium in La^3 treatment whilethe hairy root viabilities were preserved. Some specific secondary metabolite release processes could be induced by La^3 and their possible mechanism is discussed.     

Crystallographic, molecular modeling, and biophysical characterization of the valine beta 67 (E11)-->threonine variant of hemoglobin

The crystal structure of the mutant deoxyhemoglobin in which the beta-globin Val67(E11) has been replaced with threonine [Fronticelli et al. (1993) Biochemistry 32, 1235-1242] has been determined at 2.2 A resolution. Prior to the crystal structure determination, molecular modeling indicated that the Thr67(E11) side chain hydroxyl group in the distal beta-heme pocket forms a hydrogen bond with the backbone carbonyl of His63(E7) and is within hydrogen-bonding distance of the N delta of His63(E7). The mutant crystal structure indicates only small changes in conformation in the vicinity of the E11 mutation confirming the molecular modeling predictions. Comparison of the structures of the mutant beta-subunits and recombinant porcine myoglobin with the identical mutation [Cameron et al. (1993) Biochemistry 32, 13061-13070] indicates similar conformations of residues in the distal heme pocket, but there is no water molecule associated with either of the threonines of the beta-subunits. The introduction of threonine into the distal heme pocket, despite having only small perturbations in the local structure, has a marked affect on the interaction with ligands. In the oxy derivative there is a 2-fold decrease in O2 affinity [Fronticelli et al. (1993) Biochemistry 32, 1235-1242], and the rate of autoxidation is increased by 2 orders of magnitude. In the CO derivative the IR spectrum shows modifications with respect to that of normal human hemoglobin, suggesting the presence of multiple CO conformers. In the nitrosyl derivative an interaction with the O gamma atom of Thr67(E11) is probably responsible for the 10-fold increase in the rate of NO release from the beta-subunits. In the aquomet derivative there is a 6-fold decrease in the rate of hemin dissociation suggesting an interaction of the Fe-coordinated water with the O gamma of Thr67(E11).     

Luminescent and thermometric properties of dual emitting Eu~(2+)/Sm~(3+) co-doped Sr_4La(PO_4)_3O phosphor based on energy transfer

Eu²⁺/Sm³⁺co-doped dual-emitting Sr₄La(PO₄)₃O phosphors were synthesized through a convenient high temperature solid state reaction in reductive atmosphere.The structure,luminescence,energy transfer and temperature-dependent luminescence properties of Eu²⁺/Sm³⁺co-doped Sr₄La(PO₄)₃O phosphors were researched and analyzed in detail.The blue emission of Eu²⁺and the red emission of Sm³⁺can work together as FIR signals.Based on the different response characteristics of these two ion emissions to temperature,Sr₄La(PO₄)₃O:Eu²⁺/Sm^(³⁺)phosphor achieves the relative sensitivity of0.48384%/K and a wide range of temperature measurements from room temperature to 573 K.The results reveal that the Sr₄La(PO₄)₃O:Eu²⁺/Sm³⁺phosphor has application prospect in the field of high temperature optical thermometry.The energy transfer mechanism is proved to be the dipole-dipole interaction between Eu²⁺and Sm³⁺ions.     

Evidence for stabilization of the low-spin state of cytochrome P450 due to shortening of the proximal heme bond

The cytochrome P450 superfamily of enzymes is ubiquitous, being responsible for the metabolism of a wide range of endogenous and xenobiotic compounds. However, the detailed mechanism of the catalytic cycle of these enzymes is still not fully understood. We describe results, obtained from first principles molecular simulations, which indicate that the low-spin state of the Fe3+ ion, present in the heme moiety at the active site of a cytochrome P450 enzyme, may be stabilized by shortening of the proximal bond of the heme. Calculations indicate that a bond length of less than approximately 2.05 A between the heme Fe3+ ion and the cysteine S, which forms the proximal ligand, would result in the stabilization of the low-spin state of the Fe3+, inhibiting the progress of the P450 catalytic cycle. Our investigation uses novel first principles modeling techniques which treat the entire system quantum-mechanically.     

低量La3+掺杂WO3的表征及其光解水催化性能的研究

采用低热固相反应法制备了低量La3+(0.05%)掺杂的WO3催化材料,采用XRD、XPS和DRS对样品进行了表征和分析,考察了样品光催化分解水制氧的活性。结果表明,0.05%La3+掺杂可使WO3光谱响应范围向可见光区拓展。XPS分析表明,La3+掺杂可导致粉体表面晶格氧的增加。在可见光辐射下光催化分解水制氧的试验中,0.05%La3+掺杂WO3的光催化析氧速率高达177μmol/(L.h),是未掺杂WO3的1.8倍。     

Effects of Lanthanum and Europium on Rooting of Plantlet Eriobotrya Japonica Lindl. in vitro

ＲａｒｅＥａｒｔｈＥｌｅｍｅｎｔｓ (ＲＥＥｓ)ｈａｖｅｂｅｅｎｗｉｄｅｌｙｕｓｅｄｄｕｅｔｏｔｈｅｉｒｓｐｅｃｉａｌｅｌｅｃｔｒｉｃｓｔｒｕｃ ｔｕｒｅｓａｎｄｖａｒｉｅｔｉｅｓｏｆｂｉｏｌｏｇｉｃａｌａｃｔｉｖｉｔｙ .ＩｎＣｈｉｎａ ,ＲＥＥｓａｓｆｅｒｔｉｌｉｚｅｒａｄｄｉｔｉｖｅｓｉｎａｇｒｉｃｕｌ ｔｕｒｅｈａｖｅｂｅｅｎｅｘｔｅｎｓｉｖｅｌｙｕｓｅｄ .ＮｕｍｅｒｏｕｓｆｉｅｌｄｅｘｐｅｒｉｍｅｎｔｓａｎｄｐｏｔｓｔｕｄｉｅｓｓｕｇｇｅｓｔｔｈａｔＲＥＥｆｅｒｔｉｌｉｚｅｒａｐｐｌｉｃａｔｉ…     

Effect of lanthanide ions on the phase behavior of dipalmitoylphosphatidylcholine multilamellar liposomes

The effect of lanthanide ions (Ln3+) and their coordination compounds of diethylenetriamine pentaacetic acid (DTPA) on the phase behavior of dipalmitoylphosphatidylcholine (DPPC) multi-lamellar liposomes has been studied by differential scanning calorimetry (DSC), Raman spectroscopy, and freeze-fracture electron microscopic techniques. The displacement of Ca2+ binding on DPPC liposomes by lanthanide ions was also studied. The results show that the binding degree of four kinds of chloride salts with DPPC liposomes is: YbCl3 > GdCl3 > LaCl3 > CaCl2. Lanthanide ions increase the phase transition temperature of DPPC liposomes and decrease the membrane fluidity. Freeze-fracture electron microscopic results show that La3+ enhances the order of DPPC membrane. The effect of coordination compounds of lanthanides with DTPA on the phase behavior of DPPC liposomes is smaller than that of their chlorides. La3+, Gd3+, and Yb3+, can displace Ca2+ binding on DPPC liposomes, but there coordination compounds of DTPA can hardly displace Ca2+. Raman spectroscopic results show that a very slight effect in lateral packing order of DPPC liposomes was observed at various concentrations of lanthanides.     

Effect of Ni/（La＋Mg） Ratio on Structure and Electrochemical Performance of La-Mg-Ni Alloy System

As the alloy with the most suitable Ni/(La+ Mg) ratio has higher capacity and good cycle stability,theeffects of Ni/(La+Mg) ratios on the electrochemical performances of the La0.80 Mg0.20 Nix (x= 3.5 to 5.0) alloys have been investigated to find the most suitable Ni/(La+ Mg) ratio.The results of XRD and SEM observations show that the phase composition of the alloys varies with different Ni/(La+Mg) ratios.When Ni/(La+Mg) is notmore than 4.25,all the alloys contain LaNi5 and (La,Mg)2Ni7 phases,in addition,the LaMg and (La,Mg)Ni3 phases exist in the x=3.5 and 3.75 alloys,respectively.The LaMg2Ni9 phase exists in the x=4.25 alloy.There are the LaNi5 and LaMg2 Ni9 phases in the x= 4.5,4.75,and 5.0 alloys.The phase abundance and cell volume change with different Ni content.When the Ni/(La+Mg) ratio is not more than 4.25,the alloys possess excellent activation capability,however,the activation capabilities of the alloys decrease with a further increase in the Ni/(La+Mg)ratio.With increasing the Ni/(La+ Mg) ratio,the maximum discharge capacities,the medium voltages,and the cycle stabilities of the alloys first increase and then decrease.When the Ni/(La+Mg) ratio is 3.75,the corresponding alloyhas the maximum discharge capacity among all the alloys.However,the cycle stability of the Ni/(La+ Mg)= 4.0 alloy is better than that of the others.     

Investigation on the Use of the Weakly Basic Polyacrylate AnionExchanger Amberlite IRA-68 for Sorption and Separation of Iminodiacetate Complexes of Rare Earth Elements

Based on the determined affinity series of rare earth element complexes with IMDA for the anion-exchangers, purification of macroquantities of Nd^3 from Y^3 , Sm^3 from Ho^3 , La^3 from Nd^3 and La^3 from Pr^3 on the weakly basic gel anion-exchanger Amberlite IRA-68 was studied. Using the presented method on 1 L of Amberlite IRA-68 in the acetate form, it is possible to obtain about 240 g Nd2O3 purified from Y2O3. Great difference in affinity of La^3 and Nd^3 as well as Pr^3 complexes for this anion-exchanger in the acetate form indicates the possibility of applying this process for purification of lanthanum on the increased scale. On 1 L of Amberihe IRA-68 in the acetate form it is possible to obtain about 1125 g La2O3 purified from Nd2O3. On the basis of these results it can be assumed that unique properties of polyacrylate anion-exchangers enable their application for separation of rare earth elements.