A practical treatment for the three-body interactions in the transcorrelated variational Monte Carlo method: application to atoms from lithium to neon

We suggest a practical solution to dealing with the three-body interactions in the transcorrelated variational Monte Carlo method (TC-VMC). In the TC-VMC method, which was suggested in our previous paper [N. Umezawa and S. Tsuneyuki, J. Chem. Phys. 119, 10015 (2003)], the Jastrow-Slater-type wave function is efficiently optimized through a self-consistent procedure by minimizing the variance of the local energy. The three-body terms in the transcorrelated self-consistent-field equation, which have been simply ignored in our previous works, are efficiently calculated by the Monte Carlo numerical integration. We found that our treatment for the three-body interactions is successful for atoms from Li to Ne.     

Study of chemiluminescence in O + NO elementary reaction by a crossed beam technique

Chemiluminescent spectra of nitrogen dioxide in the visible region have been observed in the O + NO elementary reaction by a crossed beam technique. Dependences of the emission intensity on both the nitric oxide and atomic oxygen fluxintensities were first order, and the emission was concentrated near the crossin point. These results show that the chemiluminescence observed is due to the chemically excited NO₂ formed in the binary reaction between NO and O.     

Highly saddle shaped (porphyrinato)iron(III) iodide with a pure intermediate spin state

Combined analyses using NMR, EPR and M?ssbauer spectroscopy as well as SQUID magnetometry have revealed that highly saddle shaped Fe(OETPP)I adopts an essentially pure intermediate spin state in spite of the coordination of an iodide ligand.     

Gingipains, the major cysteine proteinases and virulence factors of Porphyromonas gingivalis: structure, function and assembly of multidomain protein complexes

Gingipains, extracellular cysteine proteinases of Porphyromonas gingivalis, constitute the major virulence factor of this periodontopathogenic bacterium. They are the product of three genes, two coding for an Arg-specific (RgpA and RgpB) and one for a Lys-specific proteinase (Kgp). Proteinase domains of RgpA and RgpB are virtually identical; however, the gene encoding the former enzyme is missing a large segment coding for hemaglutinin / adhesin (HA) domains. The latter domains are present also in Kgp. The tertiary structure of RgpB revealed that the proteinase domain of gingipains has a protein fold referred to as the caspase-hemoglobinase fold. On this basis, they are also evolutionary related to other highly specific proteinases including clostripain, caspases, legumains and separase (clan CD of cysteine peptidases). Gingipains are produced as large preproproteins and are subject to elaborate, not yet fully understood, secretion, glycosylation, activation, and maturation processes. How they traverse the outer membrane is unknown, although it can be hypothesized that they use an autotransporter pathway. Apparently during transport through the periplasm the LPS-like glycan moiety is added at the conserved C-terminal portion of progingipains. At the cell surface pro-gingipains fold into partially active, single-chain zymogens and undergo autocatalytic, intermolecular processing. Two sequential cleavages within the profragment domain enhance zymogen activity and in the case of RgpA and Kgp are followed by excision of the individual HA domains. These domains are further truncated at the C-terminus by concerted action of Kgp and carboxypeptidase and form a non-covalent multidomain, multifunctional complex anchored into the outer membrane by the glycated, C-terminal HA domain. This hypothetical scenario is a reasonable explanation for the occurrence of many forms of gingipains.     

Preparation of polysiloxanes from silicic acid. VII. Effects of the degree of esterification and alkyl groups on condensations of silicic acid esters and formation of fibrous silica

Silicic acid esters were prepared by the reaction of the silicic acid in tetrahydrofuran with various alcohols such as such as methanol, ethanol, 2-propanol, 1-butanol, 2-methyl-2-propanol and 1-octanol, using an esterification apparatus designed especially to allow the preparation of silicic acid esters from alcohols with low boiling points or appreciable steric hindrance. With the intent of obtaining a spinnable ester solution by condensation of silicic acid esters, the effects of the degree of esterification (DE) and alkyl group on gel time and spinnability are investigated. An increase in the DE and the size of the alkyl group led to an increase in the gel time of the esters. Esters solutions with a good spinnability were prepared from n-butyl and isopropyl esters with DEs of 40–50%. In addition, the gel permeation chromatography of condensing esters with low DEs showed a rapid increase in molecular weight. The results showed that spinnability depended on DE and the ester's alkyl group. Fibers could be formed with length of about 10–100 cm from ethyl, isopropyl, and n-butyl esters with DEs 40–50% and with length of 10 cm from octyl ester with DE 26%.     

Effect of Sr-for-Ba isovalent substitution on the local structure, hole distribution and magnetic irreversibility of Cu(Ba,Sr)2YbCu2O6.95(2)

The effect of Sr^II-for-Ba^II isovalent substitution on the magnetic irreversibility field (H_irr) of Cu(Ba_1−ySr_y)₂YbCu₂O_6.95(2) (Cu-1212) sample series (y=0-0.4) is studied to reveal guiding rules for tailoring the intrinsic H_irr characteristics of high-T_c superconductors. It has been assumed that substitution of the larger alkaline-earth cation, Ba^II, by the smaller, Sr^II, might improve the H_irr characteristics as a consequence of the decrease in the thickness of nonsuperconductive blocking block (BB). However, results of the present work show that Sr substitution rather depresses the H_irr characteristics of the Cu-1212-phase superconductors even though the thickness of BB decreases. Both the amount of excess oxygen and the overall positive charge are confirmed to remain constant upon the Sr substitution by wet-chemical and X-ray absorption near-edge structure analyses, respectively. However, from neutron diffraction data analysis, it is found that Sr substitution breaks the conductive CuO chains in BB by shifting part of the excess oxygen atoms from the characteristic b-axis lattice site to the a-axis site. This is believed to decrease the concentration of mobile holes in the BB, as supported by the results of TEP measurements. The lower H_irr(T) lines of the Sr-substituted samples may thus be attributed to the lower concentration of mobile holes in BB.     

Molecular structures of five-coordinated halide ligated iron(III) porphyrin,porphycene, and corrphycene complexes

Molecular structures of 12 porphyrin analogues, Fe(III)(EtioP)X(1(a)-1(d)), Fe(III)(EtioCn)X(2(a)-2(d)), and Fe(III)(Etio-Pc)X(3(a)-3(d)), where X = F (a), Cl (b), Br (c), and I (d), are determined on the basis of X-ray crystallography. Combined analyses using M?ssbauer, (1)H NMR, and EPR spectroscopy as well as SQUID magnetometry have revealed that 3(d) exhibits a quite pure S = 3/2 spin state with a small amount of an S = 5/2 spin admixture. In contrast, all the other complexes show the S = 5/2 spin state with a small amount of the S = 3/2 spin admixture. The structural and spectroscopic data indicate a strong correlation between the spin states of the complexes and the core geometries such as Fe-N bond lengths, cavity areas, and DeltaFe values.     

Syntheses of arbutin-alpha-glycosides and a comparison of their inhibitory effects with those of alpha-arbutin and arbutin on human tyrosinase

The effects of 4-hydroxyphenyl alpha-glucopyranoside (alpha-arbutin) and 4-hydroxyphenyl beta-glucopyranoside (arbutin) on the activity of tyrosinase from human malignant melanoma cells were examined. The inhibitory effect of alpha-arbutin on human tyrosinase was stronger than that of arbutin. The K(i) value for alpha-arbutin was calculated to be 1/20 that for arbutin. We then synthesized arbutin-alpha-glycosides by the transglycosylation reaction of cyclomaltodextrin glucanotransferase using arbutin and starch, respectively, as acceptor and donor molecules. The structural analyses using 13C- and 1H-NMR proved that the transglycosylated products were 4-hydroxyphenyl beta-maltoside (beta-Ab-alpha-G1) and 4-hydroxyphenyl beta-maltotrioside (beta-Ab-alpha-G2). These arbutin-alpha-glycosides exhibited competitive type inhibition on human tyrosinase, and their K(i) values were calculated to be 0.7 mM and 0.9 mM, respectively. These arbutin-alpha-glycosides possessed stronger inhibitory activity than arbutin, but less activity than alpha-arbutin. These results suggested that the alpha-glucosidic linkage of hydroquinone-glycosides plays an important role in the inhibitory effect on human tyrosinase.     

XANES Study on the Generation and Distribution of Holes via Ca Substitution and O Doping in Cu(Ba0.8Sr0.2)2(Yb1−xCax)Cu2O6+z

Generation of holes is facilitated in the Cu(Ba_0.8Sr_0.2)₂ (Yb_1−xCa_x)Cu₂O_6+z (Cu-1212) system by two independent ways, i.e., by Ca substitution (0≤x≤0.35) and O doping (0<z<1). The distribution of holes between the CuO₂-(Yb_1−xCa_x)-CuO₂ block containing two identical superconductive CuO₂ planes and the “charge-reservoir” block consisting of a single CuO_z chain has been quantitatively investigated by means of O K-edge and Cu L_2,3-edge X-ray absorption near-edge structure (XANES) spectroscopy. The resultant values for the CuO₂-plane hole concentration are compared with those calculated employing the bond-valence-sum (BVS) method from the neutron powder diffraction (NPD) data previously reported for the same samples. The results of the two methods are in good agreement. The two independent hole-doping ways are found to result in different distributions of holes over the crystal, i.e., different ratios of hole numbers at the CuO₂ plane and the CuO_z chain. With Ca substitution holes are directed efficiently into the CuO₂ plane, while for O doping holes are more homogeneously distributed between the CuO₂ plane and the CuO_z chain. Moreover, the value of T_c at a fixed CuO₂-plane hole concentration is shown to be higher for Ca-substituted than for O-doped samples.     

Study of photopolymers. XXX. Syntheses of new di(meth) acrylate oligomers by addition reactions of epoxy compounds with active esters

Some dimethacrylate oligomers were synthesized by new addition reactions of 2,2-(4-hydroxyphenyl)propane diglycidyl ether (BPGE) or glycidyl methacrylate (GMA) with phenyl methacrylates such as phenyl methacrylate (PMA), 4-nitrophenyl methacrylate (NPMA), 2,4-dichlorophenyl methacrylate (DCPMA), 4-methoxyphenyl methacrylate (MPMA), and (4-cinnamoyloxy)phenyl methacrylate (CIPMA) using tetrabutylammonium bromide as a catalyst at 120°C. The other new dimethacrylate or diacrylate oligomers were also prepared by the addition reactions of GMA or glycidyl acrylate with active esters such as di(S-phenyl)thioisophthalate (PTIP), di(4-nitrophenyl)isophthalate (NPIP), di(4-nitrophenyl)adipate (NPAD), and di(4-nitrophenyl)sebacate (NPSB) under similar reaction conditions. Furthermore, the rates of photochemical reaction of the obtained dimethacrylate oligomers were measured with 3 mol % of various photosensitizers such as benzoin iso-propyl ether (BIPE), 2-ethylanthraquinone (EAQ), and benzophenone (BP). The rate of photochemical reaction of BPGE-DCPMA oligomer was higher than those of BPGE-PMA, BPGE-NPMA, and BPGE-MPMA oligomers using BIPE as a photosensitizer. However, the photochemical reactivity of the unsensitized BPGE-CIPMA was almost the same as that of the sensitized BPGE-DCPMA. On the other hand, when EAQ was used as a photosensitizer, GMA-PTIP oligomer showed much higher reactivity than GMA-NPAD, GMA-NPSB, and GMA-NPIP oligomers. Also it was shown that the activity of EAQ as a sensitizer was higher than BIPE and BP in the photochemical reaction of BPGE-DCPMA oligomer.