Titanium dipyrrolylmethane derivatives: rapid intermolecular alkyne hydroamination

Alkynes are rapidly hydroaminated by primary amines using titanium dipyrrolylmethane derivatives as catalyst.     

Polyclonal-based ELISA for the identification of cyclohexanedione analogs that inhibit maize acetyl coenzyme-A carboxylase

Cyclohexanedione herbicides inhibit monocotyledonous acetyl coenzyme-A carboxylase (ACCase; E.C. 6.4.1.2.), which catalyzes the first committed step in fatty acid biosynthesis. Although the target site has been identified, little is known about the mechanisms involved in herbicide binding. An immunological study was undertaken to create a model to better characterize the herbicide-enzyme interaction. Cyclohexanedione-specific antiserum was raised in New Zealand white rabbits by immunizing them with a cyclohexanedione analog-bovine serum albumin conjugate. Two indirect enzyme-linked immunosorbent assays (ELISA) were developed using 2 different cyclohexanedione analogs conjugated to ovalbumin as coating conjugates. Nineteen cyclohexanedione analogs, 13 active ACCase inhibitors, and 6 inactive analogs were tested for their ability to compete with both coating conjugates for antiserum binding. All active ACCase inhibitors were observed to compete with both coating conjugates, whereas all inactive analogs failed to compete with at least one coating conjugate. On the basis of these results, the immunological model could be used to distinguish all active ACCase inhibitors from inactive analogs using the 2 ELISAs sequentially.     

Production of high quality shocks for equation of state experiments

In this paper we describe the quality requirements that a shock wave must fulfil to make equation of state (EOS) measurements possible: planarity, no-preheating and stationarity of the shock. Experimental measurements have been performed at the Max Planck Institut für Quantenoptik (Garching). We also present simple analytical models that allow to verify shock stationarity and absence of preheating. Received 17 June 2002 Published online 21 January 2003 RID="a" ID="a"e-mail: batani@mib.infn.it RID="b" ID="b"Present address: Pro-beam, Behrinsta?e 6, 85152 Planegg b. München, Germany. RID="c" ID="c"UMR 7605     

Energy transfer at optical frequencies to silicon-on-insulator structures

The refractive-index distribution that is intrinsic to the silicon-on-insulator (SOI) material system makes it possible for optical-frequency guided waves to be confined by the SOI silicon layer. The same refractive-index distribution is unusual among nonmetals in that it is possible for those SOI guided waves to interact strongly with nearby optical-frequency radiators, absorbers, and scatterers (e.g., atoms, molecules, and nanoparticles). We calculate the guided-mode excitation efficiency for an exterior particle near the SOI surface and show that it can attain values greater than 80% under appropriate conditions, thus showing that the SOI waveguide system is an attractive platform for the study of optical-frequency surface interactions.     

RF coils for combined MR and hyperthermia studies: II. MR coil as an hyperthermic applicator

Single loop surface coil, often used in MR studies, was evaluated for its performance as an inductive hyperthermic applicator. The heat deposition pattern produced by the surface coil at 84 MHz and 34 MHz was mapped in muscle-mimicking agar phantoms. Temperatures were measured simultaneously at 64 points using multiple-junction thermocouples.     

Observation and characterization of the fluorescence decay of the 2s2p(6)np 1P(o) excited states of Ne

Fluorescence decay of the 2s2p(6)np (1)P(o) excited states of neon has been observed directly for the first time. This process has also been observed indirectly by threshold photoelectron spectroscopy and in electron/photon coincidences. The measurements have allowed this weak decay channel to be characterized and branching ratios derived. The fluorescence excitation spectrum is well described by a simple Rydberg model that highlights the interplay and competition between the decay channels of autoionization and fluorescence.     

New perspective on cosmic coincidence problems

Cosmological data suggest that we live in an interesting period in the history of the universe when rho(Lambda) approximately rho(M) approximately rho(R). The occurrence of any epoch with such a "triple coincidence" is puzzling, while the question of why we happen to live during this special epoch is the "Why now?" problem. We introduce a framework which makes the triple coincidence inevitable; furthermore, the "Why now?" problem is transformed and greatly ameliorated. The framework assumes that the only relevant mass scales are the electroweak scale M(EW), and the Planck scale M(Pl) and requires rho(1/4)(Lambda) approximately M(2)(EW)/M(Pl) parametrically. Assuming that the true vacuum energy vanishes, we present a simple model, where a false vacuum energy yields a cosmological constant of this form.