Hybrid optical resonator type laser proposed for direct coupling into optical fiber

Combining one stable resonator with a concave mirror and a coupling-hole plane mirror, and another unstable resonator having a concave mirror and a convex mirror, a new hybrid optical resonator type laser has been proposed by overlapping the concave mirror as a common one and fitting the convex mirror exactly to the coupling-hole. Using theABCD law, the so-called g-parameters are first found for beam confinement. Then, based on the eigen-equation, the field distribution on the plano-convex mirror is obtained with the g-parameters above. Knowing this field distribution results in an effective transmittanceG _{e e}. Finally, the ratio of the inner convex to outer plane mirror radii can be determined for an optimum coupling in both the limiting cases of homogeneously and inhomogeneously broadened gain media. Some numerical examples will also be given for a CO₂ laser having the proposed hybrid resonator.     

Measurements of equilibrium water vapor pressures for the dehydration of magnesium, manganese and cobalt formate dihydrates by means of the transpiration method

The equilibrium water vapor pressures for the thermal dehydration of Mg(HCO(2))(2). 2H(2)O, Mn(HCO(2))(2). 2H(2)O and Co(HCO(2))(2). 2H(2)O were measured by means of the transpiration method. These hydrates form isomorphous crystals with space group P21/c. In this structure, the water molecules lie in the planes parallel to the (100) planes. Thermodynamic data such as DeltaG, DeltaH and DeltaS were derived from the values of the water vapor pressures. The relationship between these thermodynamic data and the crystal structures is discussed.     

Positive heterotropic cooperativity for selective guest binding via electronic communications through a fused zinc porphyrin array

Upon binding with C60 and diamines, such as 4,4'-bipyridine (bpy) and N,N,N',N'-tetramethylhexane-1,6-diamine (TMHDA), cyclic host 1 possessing two electronically coupled binding sites displays negative homotropic cooperativity and positive heterotropic cooperativity, and their ternary mixtures preferentially form inclusion complexes with hetero-guest pairs 1 supersetC60*bpy and 1 supersetC60*TMHDA under appropriate conditions. Spectroscopic titration profiles in toluene at 20 degrees C demonstrated that the association constants (Kassoc) of C60 with monodiamine complexes 1 supersetbpy (2.8 x 105 M-1) and 1 supersetTMHDA (1.5 x 105 M-1) are 8.5 and 4.5 times greater than that of C60 with guest-free 1 (3.3 x 104 M-1), respectively. On the other hand, mono-C60 complex 1 supersetC60 was 6.1 times more accessible than guest-free 1 toward TMHDA. Absorption spectroscopy in the absence of 1 indicated no direct interaction between C60 and diamines.     

Phlomisflavosides A and B, new flavonol bisglycosides from Phlomis spinidens

From the aerial parts of Phlomis spinidens, two new flavonol bisglycosides, phlomisflavosides A (1) and B (2), were isolated together with the known compounds, astragalin, isoquercitrin, lamiridoside, phlomoside A, shanzhiside methyl ester, 8-O-acetylshanzhiside methyl ester, phlorigidoside C, rodioloside (=salidroside), forsythoside B, citroside A and lariciresinol-4'-O-beta-D-glucoside. The structures of the new compounds were elucidated based on spectral and chemical evidence.     

Nucleophilic aromatic substitution reactions of fluorobenzenechromium complexes with P-chiral secondary phosphine-boranes: synthesis of optically pure P-chiral (dialkyl)arylphosphine-boranes

Optically pure P-chiral (dialkyl)arylphosphine-boranes having high structural diversity were prepared by two- or three-component coupling of fluorobenzenechromium complexes, P-chiral secondary phosphine-boranes, and other nucleophiles. The stereochemical integrity at the P-stereogenic center was completely retained during the S_NAr process when the reaction was carried out in THF at low temperature.     

Side chain-directed assembly of triangular molecular panels into a tetrahedron vs. open cone

Despite their structural similarity, triangular tetradentate ligands 2b and 2c experience different assembly pathways on complexation with (en)Pd(NO3)2 to give M8L4 tetrahedral (3) and open cone (4) structures, respectively, due to steric restriction by side chains at the corner or on the edge of the ligands.     

Super acid-induced Pummerer-type cyclization reaction: improvement in the synthesis of chiral 1,3-dimethyl-1,2,3,4-tetrahydroisoquinolines

Improved synthesis of four stereoisomeric chiral 1,3-dimethyl-1,2,3,4-tetrahydroisoquinolines (1a, b, ent-1a, b) was achieved via the super acid-induced cyclization of chiral N-[1-methyl-2-(phenylsulfinyl)ethyl]-N-(1-phenylethyl)formamides (4a, b, ent-4a, b) using the Pummerer-type cyclization reaction as a key step. The cyclization leading to the isoquinoline ring proceeded in a quantitative manner when trifluoromethane sulfonic acid (TFSA) was used as the super acid, although Friedel-Crafts-type alkylation of 4-phenylsulfanyl TIQ derivatives (5) with benzene used as the solvent accompanied cyclization to yield the 4-phenyl-TIQs (7). The byproduct (7) was exclusively formed when a large excess amount of TFSA was used.     

Polymerization of silylacetylenes by W and Mo catalysts

Polymerization of HC?CSiMe₃ homologues (HC?CSiMe₂R; R = n-C₆H₁₃, CH₂CH₂Ph, CH₂Ph, Ph, and t-Bu) was studied by use of W and Mo catalysts. W catalysts provided polymers in good yields from all these monomers. Mo catalysts gave mainly a polymer from HC?CSiMe₂–t-Bu, but virturally only cyclotrimers from sterically less croweded monomers (R = n-C₆H₁₃, CH₂CH₂Ph, CH₂Ph, and Ph). Polymers with flexible R groups (n-C₆H₁₃, CH₂CH₂Ph, and CH₂Ph) were totally soluble, their number-average molecular weights being 7000–18,000. Polymers with inflexible R groups (Ph and t-Bu) were partly insoluble. Every polymer was a yellow rubber or powder, and had the structure, \documentclass{article}\pagestyle{empty}\begin{document}$ \rlap{--} [{\rm CH} = {\rm C}\left( {{\rm SiMe}_{\rm 2} {\rm R}} \right)\rlap{--} ]_n $\end{document}. The results were compared with the polymerization and polymer of HC?CSiMe₃.