Silicon-wire-based ultrasmall lattice filters with wide free spectral ranges

Using silicon-on-insulator-based silicon-wire waveguides with submicrometer cross sections, we constructed ultrasmall channel-dropping lattice filters for 1.5-microm infrared systems. The waveguide's low-loss bends with 2.5-microm radius reduce the total length of the filter to less than 100 microm and enlarge the free spectral range to more than 80 nm. The measured spectra show fine channel-dropping characteristics, and the results agree well with numerical predictions. Moreover, we have succeeded in tuning the dropping wavelength by adjusting the lengths of the delay lines.     

Controlled Formation of Low-Volume Liquid Pillars between Plates with a Lattice of Wetting Patches by Use of a Second Immiscible Fluid

We describe a method for forming an array of microdroplets between two plates, at least one of which is patterned with a lattice of wetting patches, using a second immiscible fluid to control droplet formation. The method may be useful for performing multiple, small-volume biochemical reactions in parallel. We analyze the forces responsible for droplet formation, describe results of a computer simulation using Surface Evolver, and derive an analytic criterion for droplet formation in terms of the contact angles of the droplet:second fluid interface on the wetting patches and surrounding surface, the diameter of the wetting patches, the distance between wetting patches, and the distance between the plates. Copyright 1999 Academic Press.     

Trapping of neutral mercury atoms and prospects for optical lattice clocks

We report vapor-cell magneto-optical trapping of Hg isotopes on the (1)S(0)-(3)P(1) intercombination transition. Six abundant isotopes, including four bosons and two fermions, were trapped. Hg is the heaviest nonradioactive atom trapped so far, which enables sensitive atomic searches for "new physics" beyond the standard model. We propose an accurate optical lattice clock based on Hg and evaluate its systematic accuracy to be better than 10;{-18}. Highly accurate and stable Hg-based clocks will provide a new avenue for the research of optical lattice clocks and the time variation of the fine-structure constant.     

Lipase‐Catalyzed Degradation of Polyester in Supercritical Carbon Dioxide

Enzymatic degradation of poly(ε‐caprolactone) has been successfully carried out in supercritical carbon dioxide (scCO₂). Candida antarctica lipase smoothly catalyzed the hydrolytic degradation in scCO₂ to give oligo(ε‐caprolactone). The degradation in the presence of acetone (5 vol.‐%) produced the oligomer of smaller molecular weight (less than 500) compared to that prepared without the additive. Matrix‐assisted laser desorption/ionization‐time of flight (MALDI‐TOF) mass spectrometry analysis showed that the degradation product was of a mixture of linear and cyclic oligomers. The addition of a very small amount of water also promoted the degradation of the polyester.     

Thin-layer ion-selective electrode detection of anticardiolipin antibodies in syphilis serology

A method for a serological diagnosis of syphilis is presented, in which a thin-layer ion-selective electrode is used for monitoring the complement-mediated immune lysis of antigen-sensitized phospholipid liposomes in microlitre sample volumes. The liposomes are loaded with tetrapentylammonium ions (TPA(+)) which are then released from the liposomes by the immuno reaction and are monitored by a TPA(+) ion-selective electrode. This is a direct but much amplified measure of the syphilitic antibodies to be assayed. The principles and evaluation of the method are given. The results have been compared and correlated with those of a conventional method.     

Lead Phthalocyanine: A one-dimensional conductor

The temperature dependence of the electrical resistivity of lead phthalocyanine (PbPc) films and the crystal structure of PbPc suggest that PbPc is a one-dimensional conductor.     

Spectroscopy of the 1S0-3P0 clock transition of 87Sr in an optical lattice

We report on the spectroscopy of the 5s(2) 1S0(F=9/2)-->5s5p 3P0(F=9/2) clock transition of 87Sr atoms (natural linewidth of 1 mHz) trapped in a one-dimensional optical lattice. Recoilless transitions with a linewidth of 0.7 kHz as well as the vibrational structure of the lattice potential were observed. By investigating the wavelength dependence of the carrier linewidth, we determined the magic wavelength, where the light shift in the clock transition vanishes, to be 813.5+/-0.9 nm.