Dramatic effects of excess oxygen on physical properties and crystal structure of La0.95Sr0.05MnOy single crystal

We have examined the effects of excess oxygen on the magnetization, electrical transport properties and crystal structure of La_0.95Sr_0.05MnO_y. An antiferromagnetic insulator phase confirmed in the as-grown crystal at low temperatures changed to a ferromagnetic insulator phase after the introduction of excess oxygen. The ferromagnetic transition temperature, T_C, systematically increased with increasing oxygen content, y, due to an increase in the mean valence of manganese. However, the T_C of crystals with excess oxygen was lower than that of the La_1−xSr_xMnO_3.00 having identical manganese valence. This is considered to be a result of the competition among the mean valence of manganese, the concentration of cation vacancies, and the mean ionic radius of cations at the A-site.     

Synthesis and phosphate uptake behavior of Zr4+ incorporated MgAl-layered double hydroxides

We synthesized Zr(4+) incorporated MgAl-layered double hydroxides, Mg(AlZr)-LDH(A) (where A denotes a counteranion in the interlayer space and is expressed as CO(3) for carbonate and Cl for chloride ions), with different molar ratios of Mg/(Al+Zr). Then we characterized their uptake behavior toward phosphate ions. CO(3)-type tertiary LDH materials synthesized at room temperature show low crystallinity, whereas the highly crystalline Cl-type tertiary LDH, [Mg(0.68)Al(0.17)Zr(0.14)(OH)(2)][Cl(0.26)(CO(3))(0.04)1.24H(2)O], was synthesized for the first time using a hydrothermal treatment at 120 degrees C. The distribution coefficients (K(d)) of oxo-anions were measured with a mixed solution containing trace amounts of the anions. The selectivity sequences were Cl(-), NO(-)(3)相似文献   

Squarefree P-modules and the cd-index

In this paper, we introduce a new algebraic concept, which we call squarefree P-modules. This concept is inspired from Karu's proof of the non-negativity of the cd-indices of Gorenstein* posets, and supplies a way to study cd-indices from the viewpoint of commutative algebra. Indeed, by using the theory of squarefree P-modules, we give several new algebraic and combinatorial results on CW-posets. First, we define an analogue of the cd-index for any CW-poset and prove its non-negativity when a CW-poset is Cohen–Macaulay. This result proves that the h-vector of the barycentric subdivision of a Cohen–Macaulay regular CW-complex is unimodal. Second, we prove that the Stanley–Reisner ring of the barycentric subdivision of an odd dimensional Cohen–Macaulay polyhedral complex has the weak Lefschetz property. Third, we obtain sharp upper bounds of the cd-indices of Gorenstein* posets for a fixed rank generating function.     

Ring Opening Three-Carbon Extension of 2-Carboethoxycyclo-Alkanones with 3-Bromo-1-(p-Tolylsulfonyl)Propene

Reaction with 1,8-diazabicyclo[5,4,0]undec-7-ene (DBU) of 2-[3-(p-tolylsulfonyl)-2-propenyl]-2-carboethoxycycloalkanones, derived from 2-carboethoxy-2-sodiocycloalkanones and 3-bromo-l-(p-tolylsulfonyl)propene, caused ring opening three-carbon extension in ethanol and three-carbon ring expansion in benzene to produce terminal dienes and cyclic dienes, respectively.     

Hereditary Spastic Paraplegia Protein Spartin Is an FK506-Binding Protein Identified by mRNA Display

1. Download : Download high-res image (197KB)
2. Download : Download full-size image

     

Characterization of Protein Complexes Containing Nucleoside Diphosphate Kinase with Characteristics of Light Signal Transduction through Phytochrome in Etiolated Pea Seedlings

Abstract— At 5 days after sowing of pea seeds in darkness, intact seedlings were either irradiated with red light for 40 s at 50 μmol/m²/s at the third internode or with red light as above and then with far-red light for 180 s at 0.4 μmol/m²/s, and the stems were sectioned from below the hook (mainly the third internodes) and placed in liquid N₂ in a mortar. The samples were well ground, and after the addition of extraction buffer, homogenates were centrifuged to prepare the crude membrane and soluble fractions. Red-light irradiation increased the phosphorylation of an 18 kDa protein, while far-red-light irradiation decreased it. The 18 kDa protein (formerly 15 kDa protein) was identified as nucleoside diphosphate kinase (EC 2.4.6) (NDP kinase) by western blotting using an NDP kinase-specific antibody. The membrane and the soluble fractions of the red-light-irradiated samples were separated by native polyacrylamide gel electrophoresis. The protein complexes prepared from the membrane and soluble fractions differed in their mobilities, as determined by two-dimensional electrophoresis and nonequilibrium pH gradient electrophoresis. The major protein spots from both samples were cut out from the gel and tested for NDP kinase and protein kinase activity. Both protein preparations showed NDP kinase activity and changes from nucleoside diphosphates and deoxynucleoside diphosphates to nucleoside triphosphates and deoxynucleoside triphosphates in the presence of [γ-³²P]ATP. Both preparations showed protein kinase phosphorylation of myelin basic protein (MBP) rather than histone H1 as protein substrates, suggesting that NDP kinase possesses a function similar to that of MAP kinase.     

Unique Participation of Unprotected Internucleotidic Phosphodiester Residues on Unexpected Cleavage Reaction of the Si?O Bond of the Diisopropylsilandiyl Group Used as a Linker for the Solid‐Phase Synthesis of 5′‐Terminal Guanylated Oligodeoxynucleotides

In connection with the synthesis of guanosine‐capped oligodeoxynucleotides on polymer supports, we found an unprecedented Si O bond cleavage reaction, which occurred when polymer‐linked oligodeoxynucleotides having unprotected internucleotidic phosphate groups were allowed to react with the guanosine 5′‐phosphorimidazolide derivative 18 in the presence of 4‐nitro‐6‐(trifluoromethyl)‐1H‐benzotriazol‐1‐ol (Ntbt‐OH) as an effective activator in pyridine. This side reaction was confirmed by the fact that the liquid‐phase reaction of DMTrTpT O Si(iPr₂)OEt 42 with a simpler model compound, methyl phosphorimidazolide 34 , in the presence of Ntbt‐OH gave DMTrTpT 43 . It turned out that the side reaction hardly occurs without unprotected internucleotidic phosphate groups on oligodeoxynucleotides. The detailed study of this side reaction disclosed that Ntbt‐OH directly attacks the Si‐atom to release oligonucleotides from the resin. It is likely that Ntbt‐OH serves as a very strong nucleophile in pyridine, especially to the Si‐atom of the linker.     

Mechanisms and kinetics of living radical polymerizations

The polymerization rates and activation processes of several variants of living radical polymerization (LRP) are discussed on the basis of recent experimental and theoretical results. Because of bimolecular termination, which is inevitable in LRP as well as in conventional radical polymerization, the time‐conversion curves of LRP have several characteristic features depending on the experimental conditions, such as the presence or absence of conventional initiation. Despite the presence of termination (and initiation, in some cases), polymers obtained by LRP can have a low polydispersity, provided that the number of terminated chains is small compared to the number of potentially active chains. A large rate constant of activation, k_act, is another fundamental requisite for low polydispersities. Systematic experimental investigation into k_act has clarified the exact mechanisms of activation in several LRP systems. The magnitudes of k_act was found to largely differ from system to system.