Near-Field Optical Microscope with Tapping Illumination and Synchronous Detection

We use the tapping illumination and synchronous detection in a scanning near-field optical microscopy to obtain a near-field optical signal that is separated from the far-field signal. The illumination light was irradiated from the bent fiber tip vibrating normal to the sample surface. The transmitted light synchronized with the tapping vibration was observed. The obtained image of an organic film shows that this technique is effective for the weak contrast samples.This paper was originally presented at the 5th International Conference on NEAR FIELD OPTICS and RELATED TECHNOLOGIES (NFO-5), which was held on December 6–10, 1998 at Coganoi Bay Hotel, Shirahama, Japan, in cooperation with the Japan Society of Applied Physics and Mombusho Grant-in Aid for Scientific Research on Priority Areas “Near-field Nano-optics” Project, sponsored by Japan Society for the Promotion of Science.     

Double coverings of 2‐paths by Hamilton cycles*

A double Dudeney set in K_n is a multiset of Hamilton cycles in K_n having the property that each 2‐path in K_n lies in exactly two of the cycles. A double Dudeney set in K_n has been constructed when n ≥ 4 is even. In this paper, we construct a double Dudeney set in K_n when n ≥ 3 is odd. © 2002 Wiley Periodicals, Inc. J Combin Designs 10: 195–206, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ) DOI 10.1002/jcd.10003     

Four (E,Z,E)‐1‐(4‐alkoxy­phen­yl)‐6‐(4‐nitro­phen­yl)hexa‐1,3,5‐trienes

The crystal structures of the four E,Z,E isomers of 1‐(4‐alk­oxy­phen­yl)‐6‐(4‐nitro­phen­yl)hexa‐1,3,5‐triene, namely (E,Z,E)‐1‐(4‐methoxy­phen­yl)‐6‐(4‐nitro­phen­yl)hexa‐1,3,5‐triene, C₁₉H₁₇NO₃, (E,Z,E)‐1‐(4‐ethoxy­phen­yl)‐6‐(4‐nitro­phen­yl)hexa‐1,3,5‐triene, C₂₀H₁₉NO₃, (E,Z,E)‐1‐(4‐nitro­phen­yl)‐6‐(4‐n‐propoxyphen­yl)hexa‐1,3,5‐triene, C₂₁H₂₁NO₃, and (E,Z,E)‐1‐(4‐n‐butoxy­phen­yl)‐6‐(4‐nitro­phen­yl)hexa‐1,3,5‐triene, C₂₂H₂₃NO₃, have been determined. Inter­molecular N⋯O dipole inter­actions between the nitro groups are observed for the meth­oxy derivative, while for the eth­oxy derivative, two adjacent mol­ecules are linked at both ends through N⋯O dipole–dipole inter­actions between the N atom of the nitro group and the O atom of the eth­oxy group to form a supra­molecular ring‐like structure. In the crystal structures of the n‐prop­oxy and n‐but­oxy derivatives, the shortest inter­molecular distances are those between the two O atoms of the alk­oxy groups. Thus, the nearest two mol­ecules form an S‐shaped supra­molecular dimer in these crystal structures.     

Syringe-cartridge solid-phase extraction method for patulin in apple juice

A syringe-cartridge solid-phase extraction (SPE) method was developed for determination of patulin in apple juice. A 2.5 mL portion of test sample was passed through a conditioned macroporous SPE cartridge and washed with 2 mL 1% sodium bicarbonate followed by 2 mL 1% acetic acid. Patulin was eluted with 1 mL 10% ethyl acetate in ethyl ether and determined by reversed-phase liquid chromatography using a mobile phase consisting of 81% acetonitrile, 9% water, and 10% 0.05M potassium phosphate buffer, pH 2.4. Recoveries averaged 92% and the relative standard deviation was 8.0% in test samples spiked with 50 ng/mL patulin. The method appears to be applicable for monitoring apple juice samples to meet the U.S. Food and Drug Administration compliance action level of 50 microg/kg in an industrial quality assurance laboratory environment.     

Dibenzo[b, e]-7,7,8,8-tetraneopentyl- and dibenzo[b, e]-7,7,8,8-tetraisopropyl-7,8-disilabicyclo[2.2.2]octa-2,5-dienes: interaction with tetracyanoethylene and transition metal chlorides

Dibenzo[b,e]-7,7,8,8-tetraalkyl-7,8-disilabicyclo[2.2.2]octa-2,5-dienes (1: R = ^tBuCH₂; 2: R = ⁱPr) were prepared by the reaction of ClR₂SiSiR₂Cl with lithium anthracenide in 1,2-dimethoxyethane (DME) at room temperature. The structure of 1 was determined by X-ray crystallography. Crystal data for 1: monoclinic, rC2/c, A = 12.941(2), B = 14.601(1), C = 35.109(6) Å, β = 94.957(7)°, V = 6609(2) ų, Z= 8, R = 0.048, R_w = 0.053 for 4037 reflections. Compounds 1 and 2 show the bathochromic shift of ¹L_a and ¹L_b bands in UV spectra and exhibit considerably low oxidation potentials due to effective σ-π conjugation. Compounds 1 and 2 form charge-transfer complexes with tetracyanoethylene (TCNE). In the case of 1, the charge-transfer complex (1: TCNE = 2: 1) could be isolated as crystals and the structure was determined by X-ray crystallography. Crystal data for the 1-TCNE complex: monoclinic, C2/c, A= 10.267(2), b = 36.077(4), C = 20.022(4) Å, β = 100.680(8)°, V = 7288(2) ų, Z = 4, R = 0.045, R_w = 0.077 for 4120 reflections. The action of transition metal chlorides on 2 resulted in [4+2] cycloreversion to form ClⁱPr₂SiSiⁱPr₂Cl and anthracene.     

24,24-Dimethylvitamin D3-26,23-lactones and their 2α-functionalized analogues as highly potent VDR antagonists

Novel vitamin D receptor (VDR) antagonists, 24,24-dimethyl-1α-hydroxyvitamin D₃-26,23-lactones (8 and 9) and their C2α functionalized analogues (8a-c and 9a-c) were efficiently synthesized and their biological activities were evaluated. The construction of vitamin D₃ triene skeleton was achieved by palladium-catalyzed alkenylative cyclization of A-ring precursor enyne (22 and 22a-c) with CD-ring bromoolefin having a 24,24-dimethyl-α-methylene-γ-lactone unit on the side chain (13 and 14). The CD-ring precursors 13 and 14 were prepared by using chromium-mediated allylation of the aldehyde 10 derived from vitamin D₂. On the other hand, the A-ring enyne having 2α-(3-hydroxypropyl) group (22b) was newly synthesized from epoxide 15 using regio- and stereoselective alkylation methodology. The potency of the antagonistic activity of the newly designed analogues (8 and 9) increased up to 12 times that of TEI-9647 (2). Furthermore, introduction of the three motifs, that is, a methyl (8a and 9a), an ω-hydroxypropyl (8b and 9b) or an ω-hydroxypropoxyl group (8c and 9c) into the C2α position of 8 and 9, respectively, resulted in remarkable enhancement, up to 89 times, of the antagonistic activity on VDR.     

Does Gd@C82 have an anomalous endohedral structure? Synthesis and single crystal X-ray structure of the carbene adduct

We report here the results on single crystal X-ray crystallographic analysis of the Gd@C82 carbene adduct (Gd@C82(Ad), Ad = adamantylidene). The Gd atom in Gd@C82(Ad) is located at an off-centered position near a hexagonal ring in the C2v-C82 cage, as found for M@C82 (M = Sc and La) and La@C82(Ad). Theoretical calculation also confirms the position of the Gd atom in the X-ray crystal structure.