Stay time measurements for Xe,Kr, and CO2 physisorbing on Ni and Cu surfaces

A pulsed molecular beam apparatus is used to measure mean stay times for gases physisorbing on cooled surfaces. Most of the data are for Xe on nickel surfaces. Data are also presented for Kr and CO₂ on nickel, Xe on copper, and Xe on ion-sputter-cleaned nickel. All targets are polycrystalline. Surface temperatures range from 92 to 125 K and measured stay times range from 10^?5 to 10^?3 s. Heats of adsorption and pre-exponential factors deduced from the data indicate that the adsorption is localized (immobile) and suggest that the sputter-cleaned targets may be approximately clean. A model relating the shape of the detector signal to the mean stay time is presented and its validity is assessed. Measured speed distributions for the desorbing molecules exhibit an excess of slow molecules compared to that expected for simple effusion. At lower surface temperatures where longer stay times are observed, a peculiar detector signal dip is observed which appears to indicate that the adsorbing beam pulses temporarily reduce the steady state desorption rate of background atoms.     

Evidence for charge Kondo effect in superconducting Tl-doped PbTe

We report results of low-temperature thermodynamic and transport measurements of Pb1-xTlxTe single crystals for Tl concentrations up to the solubility limit of approximately x=1.5%. For all doped samples, we observe a low-temperature resistivity upturn that scales in magnitude with the Tl concentration. The temperature and field dependence of this upturn are consistent with a charge Kondo effect involving degenerate Tl valence states differing by two electrons, with a characteristic Kondo temperature T(K) approximately 6 K. The observation of such an effect supports an electronic pairing mechanism for superconductivity in this material and may account for the anomalously high T(c) values.     

Synthesis of novel iodo derived bicalutamide analogs

A series of optically active nonsteroidal selective androgen receptor modulators with structures analogous to bicalutamide was prepared by replacing the trifluoromethyl group with iodine and the sulfonyl linker by oxygen.     

A rare earth-DOTA-binding antibody: probe properties and binding affinity across the lanthanide series

An antibody that binds rare earth complexes selectively could be used as a docking station for a set of probe molecules, of particular interest for medical imaging and therapy. The rare earths are rich in probe properties, such as the paramagnetism of Gd, the luminescence of Tb and Eu, and the nuclear properties of Lu and Y. We find that antibody 2D12.5, initially developed to bind analogues of Y-DOTA (1,4,7,10-tetraazacyclododecane-N,N',N' ',N' '-tetraacetic acid) for radiotherapy, binds not only Y-DOTA analogues but also analogous DOTA complexes of all of the lanthanides. Surprisingly, chelates of some metals such as Gd3+ bind more tightly than the original Y3+ complex. When the shape of the complex is perturbed by either increasing or decreasing the radius of the lanthanide ion, the thermodynamic stability of the protein-ligand complex changes in a regular fashion. The behavior of DeltaDeltaG as a function of ionic radius fits a parabola, as might be expected for a system that behaves in a thermodynamically elastic way. The broad specificity and high affinity of this antibody for all rare earth-DOTA complexes make it particularly interesting for applications that take advantage of the unique characteristics of lanthanides. For example, UV excitation of the Tb-DOTA-2D12.5 complex leads to energy transfer from aromatic side chains of the antibody to bound Tb-DOTA, enhancing green terbium luminescence >104 relative to unbound Tb-DOTA.     

Sub-ppt detection limits for copper ions with Gly-Gly-His modified electrodes

An electrochemical metal ion sensor has been developed with a detection limit of less than 0.2 ppt by the covalent attachment of the tripeptide Gly-Gly-His as a recognition element to a 3-mercaptopropionic acid modified gold electrode.     

The -exponent of the -local spectrum

Let be a fixed odd prime. In this paper we prove an exponent conjecture of Bousfield, namely that the -exponent of the spectrum is for . It follows from this result that the -exponent of is at least for and , where denotes the -connected cover of .

     

Conversion of unpolarized light to polarized light with greater than 50% efficiency by photorefractive two-beam coupling

All known polarizers operate through a separation of orthogonal electric field components, one of which is subsequently discarded. As a result, 50% of the unpolarized incident light is wasted in the process of conversion to polarized light. We demonstrate a new method by which we use the optical power in the ordinarily discarded component as the pump to amplify the retained component through photorefractive two-beam coupling to achieve greater than 50% throughput.     

Suppression of magnetic relaxation by a transverse alternating magnetic field

The evolution of the spatial distribution of the magnetic induction in a superconductor after the action of the alternating magnetic field perpendicular to the trapped magnetic flux has been analyzed. The observed stabilization of the magnetic induction profile is attributed to the increase in the pinning force, so that the screening current density becomes subcritical. The last statement is corroborated by direct measurements.