Performance assessment of a new laser system for efficient spin exchange optical pumping in a spin maser measurement of <Superscript>129</Superscript>Xe EDM

We demonstrate spin-exchange optical pumping of ¹²⁹Xe atoms with our newly made laser system. The new laser system was prepared to provide higher laser power required for the stable operation of spin maser oscillations in the ¹²⁹Xe EDM experiment. We studied the optimum cell temperature and pumping laser power to improve the degree of ¹²⁹Xe spin polarization. The best performance was achieved at the cell temperature of 100 ^°C with the presently available laser power of 1 W. The results show that a more intense laser is required for further improvement of the spin polarization at higher cell temperatures in our experiment.     

Improvement of magnetic intergranular isolation and evaluation of read/write characteristics on SmCo5 perpendicular magnetic thin films

SmCo₅ alloy is a promising candidate for ultra-high-density perpendicular magnetic recording (PMR) media because of its high uniaxial magnetocrystalline anisotropy K_u of more than 1.1×10⁸ erg/cm³. Previously, we successfully achieved high K_u in a sputter-deposited SmCo₅ thin film by introducing a Cu/Ti dual underlayer. However, in order to apply the SmCo₅ films to practical PMR media, it is necessary to decrease medium noise. A granulated magnetic film comprising of small and magnetically decoupled grains is effective in reducing the medium noise. In this paper, we have proposed a new granular film that is fabricated by partial thermodiffusion of Cu between the Sm-Co continuous layer and the Cu underlayer, which is granulated using compositional segregation caused by the addition of Ta₂O₅. We have analyzed the magnetic properties, magnetic domain size, and magnetization reversal process of the proposed SmCo₅ film. The magnetic domain size decreased and the magnetization reversal process changed from the magnetic-wall-motion mode to a coherent rotation mode to some extent on isolation of magnetic grains. The read/write characteristics of granulated SmCo₅ double-layered media were also evaluated. The medium noise decreased and the signal-to-noise ratio increased for the granulated double-layered (PMR) medium.     

New efficient organic activators for highly enantioselective reduction of aromatic ketones by trichlorosilane

[reaction: see text] Aryl ketones were reduced to the corresponding alcohols with excellent enantioselectivity (up to 99.7% ee) by Cl3SiH in the presence of a catalytic amount of N-formyl-alpha'-(2,4,6-triethylphenyl)-L-proline as an activator. Both carboxyl group at the alpha-position of the activator and 2,4,6-triethylphenyl group at the alpha'-position were critical for the high enantioselectivity.     

High static pressure alters spin trapping rates in solution. Dependence on the structure of nitrone spin traps

Using a competitive spin trapping method, relative spin trapping rates were quantified for various short-lived radicals (methyl, ethyl, and phenyl radicals). High static pressure was applied to the competitive spin-trapping system by employing high-pressure electron spin resonance (ESR) equipment. Under high pressure (490 bar), spin trapping rate constants for alkyl and phenyl radicals increased by 10 to 40%, and the increase was dependent on the structure of nitrone spin traps. A maximum increase was obtained when tert-butyl(4-pyridinylmethylene)amine N-oxide (4-POBN) was used as a spin trap. Activation volumes (DeltaDeltaV(double dagger)) for the two spin trapping reactions were calculated to be -17-(-9) cm(3) mol(-1) for the 4-POBN system.     

Medicinal Flowers. Part 29. Acylated Oleanane‐Type Triterpene Bisdesmosides: Perennisaponins G,H, I,J, K,L, and M with Pancreatic Lipase Inhibitory Activity from the Flowers of Bellis perennis

The MeOH extract from the flowers of Bellis perennis was found to show pancreatic‐lipase inhibitory activity (IC₅₀ 455 μg/ml). From the extract, seven new triterpene saponins named perennisaponins G ( 1 ; IC₅₀ 163 μM ), H ( 2 ; 137 μM ), I ( 3 ; 147 μM ), J ( 4 ; 148 μM ), K ( 5 ; 223 μM ), L ( 6 ; 81.4 μM ), and M ( 7 ; 195 μM ) were isolated as pancreatic lipase inhibitors. The stereostructures of 1 – 7 were elucidated on the basis of chemical and spectroscopic evidence.     

Competitive Trapping of Nitric Oxide (NO) Between Fe(III)-dithiocarbamate Complex and Liposome-encapsulated Trimethylammonio-PTIO: Effects of Ligand Structure, Charge on Liposome Surface, and External Pressure on NO-trapping Rates

Using a competitive nitric oxide (NO)-trapping method between Fe–dithiocarbamate (DTC) complexes and liposome-encapsulated 2-[4-trimethylammonio]-4,4,5,5-tetramethyl-imidazoline-1-oxyl 3-oxide (TMAPTIO), NO-trapping rates of Fe–DTC complexes in the presence of phosphatidylcholine liposomes were quantified for five kinds of Fe–DTC complexes. We investigated how the DTC ligand structure influences the NO-trapping rates of Fe–DTC complexes. The negatively charged liposomes give a higher NO-trapping rate of Fe–DTC complexes than do the positively charged ones, suggesting that the presence of a charge on the liposome surface affects the NO-trapping rate processes of Fe–DTC complexes. In addition, on the basis of the pressure dependence experiments for the competitive reaction, we evaluated the difference in activation volumes between the NO-trapping reactions by Fe–DTC complexes and TMA-PTIO, which allowed us to consider possible reaction mechanisms for the NO-trapping processes.     

Two‐factors each component of which contains a specified vertex

It is shown that if G is a graph of order n with minimum degree δ(G), then for any set of k specified vertices {v₁,v₂,…,v_k} ? V(G), there is a 2‐factor of G with precisely k cycles {C₁,C₂,…,C_k} such that v_i ∈ V(C_i) for (1 ≤ i ≤ k) if or 3k + 1 ≤ n ≤ 4k, or 4k ≤ n ≤ 6k ? 3,δ(G) ≥ 3k ? 1 or n ≥ 6k ? 3, . Examples are described that indicate this result is sharp. © 2003 Wiley Periodicals, Inc. J Graph Theory 43: 188–198, 2003     

Synthesis of 2,4-disubstituted thiazoles from (Z)-(2-acetoxyvinyl)phenyl-lambda3-iodanes: nucleophilic substitution of alpha-lambda3-iodanyl ketones with thioureas and thioamides

In the presence of triethylamine, (Z)-(2-acetoxy-1-alkenyl)phenyl-lambda(3)-iodanes react with thioureas or thioamides in MeOH to give 2,4-disubstituted thiazoles directly in good yields. The reaction probably involves generation of highly reactive alpha-lambda(3)-iodanyl ketones through ester exchange of the beta-acetoxy group with liberation of methyl acetate, followed by nucleophilic substitutions with thioureas or thioamides.     

Preparation of macroreticular chelating resins containing mercapto groups from 2,3-epithiopropyl methacrylate/divinylbenzene copolymer beads and their adsorption capacity

Macroreticular chelating resins containing mercapto groups were prepared by the reaction of 2,3-epithiopropyl methacrylate/divinylbenzene macroreticular copolymer beads with ethanolic potassium hydrogensulfide solution for 1 h at 50°C. The adsorption capacities of this resin for Ag⁺, Hg²⁺, Pb²⁺ and Cd²⁺ were determined at various pH values. In the acidic region, the resin shows a high affinity for Ag⁺ and Hg²⁺ and high resistance against air oxidation. Cadmium is readily eluted with 1 mol dm^?3 hydrochloric acid; silver, mercury and copper ions can be eluted with 1 mol dm^?3 hydrochloric acid containing 5% (w/v) thiourea. The proposed resin appears to be useful for the removal of As³⁺ from aqueous solutions.     

Hydrolysis and Condensation Processes of Titanium iso-Propoxide Modified with Catechol: An NMR Study

The hydrolysis and condensation processes of titanium iso-propoxide modified with catechol (C₆H₄(OH)₂; H₂cat) have been investigated by ¹H, ¹³C and ¹⁷O nuclear magnetic resonance spectroscopy. The hydrolysis reactions of the modified titanium iso-propoxide in the system with Ti:tetrahydrofuran (THF):H₂O = 1:20:x (x = 1, 2 and 5 in a molar ratio) are essentially completed in the initial stage (<1 h), and the condensation reactions also proceed significantly during this stage. Upon hydrolysis with H₂O/Ti = 1, the iso-propoxy groups are selectively hydrolyzed and the catecholate groups remain bound to titanium. With H₂O/Ti = 2 and 5, both the iso-propoxy and catecholate groups are hydrolyzed, and the hydrolysis of the iso-propoxy groups is relatively preferential. Approximately half the catecholate groups are stably bound to titanium, even after hydrolysis with H₂O/Ti = 5.