DMSA and its complexes with radioisotopes: review

Meso-2,3-dimercaptosuccinic acid (DMSA) forms stable complexes with a remarkable wide range of metal ions. This relatively small molecule has attracted increasing attention in the field of radiopharmacy, treatment of heavy metal intoxications and nanoparticles preparation. In this review detailed summary of all physical, chemical and biological properties of DMSA and its complex compounds with ^99mTc, ^186/188Re, ¹⁶⁶Ho, ¹⁷⁷Lu and ⁹⁰Y is provided. The clinical utilisation of DMSA complexes in the nuclear medicine and its use for treatment of heavy metal intoxication is briefly summarised. The aspects of its application in the field of nanoparticles preparation is behind the scope of this review, therefore it is only shortly described.     

Mu+H2 and Mu+D2 reaction kinetics from 480 To 675 K

This paper reports preliminary new measurements of the thermal reaction rate constants of muonium (Mu) with hydrogen and deuterium gases in the range 480–675 K. From Arrhenius plots of the measured reaction rate constants new values of the pre-exponential factors log₁₀ (A) and activation energies E_a have been determined for these reactions, representing a significant improvement over earlier results.     

Squeezed-light source for superresolving microscopy

We propose a source of multimode squeezed light that can be used for superresolving microscopy. This source is an optical parametric amplifier with a properly chosen diaphragm on its output and a Fourier lens. We demonstrate that such an arrangement produces squeezed prolate spheroidal waves that are the eigenmodes of the optical imaging scheme used in microscopy and discuss the conditions of the degree of squeezing and of the number of spatial modes in illuminating light.     

Origination and Transformation of the Monoclinic and Orthorhombic Phases in Reactor Powders of Ultrahigh Molecular Weight Polyethylene

Using powerful synchrotron X-ray radiation of the beamline “Belok” operated by the National Research Center “Kurchatov Institute,” we perform X-ray diffraction (XRD) study of an intact, virgin (not subjected to any external mechanical loads) particle isolated from reactor powder of ultrahigh molecular weight polyethylene. Along with the peaks originating from the orthorhombic phase, we detect the peaks characteristic of the monoclinic phase that is stable only under mechanical stress, suggesting that the mechanical stress that leads to the formation of the monoclinic phase and persists at room temperature develops during the polymer synthesis. The monoclinic phase gradually disappears when the particle is heated stepwise in increments of 5 K, and its peaks become undetectable when the temperature reaches 340 K. We contrast the results obtained for the phase composition of the virgin particle to those for a tablet prepared by compaction of the same reactor powder at room temperature. XRD analyses of the tablet were performed on D2 Phaser (Bruker) instrument. The monoclinic phase that originates during the polymer synthesis and the one that forms in the tablet during compaction have different parameters. We discuss the mechanisms by which these two different monoclinic phases originate during the processes involved.

     

Spontaneous polarization in one-dimensional Pb(ZrTi)O3 nanowires

Formation of spontaneous polarization in one-dimensional (1D) structures is a key phenomenon that reveals collective behaviors in systems of reduced dimensions, but has remained unsolved for decades. Here we report ab initio studies on finite-temperature structural properties of infinite-length nanowires of Pb(Zr0.5Ti0.5)O3 solid solution. Whereas existing studies have ruled out the possibility of phase transition in 1D chains, our atomistic simulations demonstrate a different conclusion, characterized by the occurrence of a ferroelectric polarization and critical behaviors of dielectric and piezoelectric responses. The difference is accounted for by the use of depolarizing effects associated with finite thickness of wires. Our results suggest no fundamental constraint that limits the use of ferroelectric nanowires and nanotubes arising from the absence of spontaneous ordering.     

Morphology-dependent photonic circuit elements

We theoretically propose and experimentally demonstrate the design of a novel one-dimensional ringlike macroscopic optical circuit element. The similarity between morphologies of an optical planar waveguide and a whispering-gallery axially symmetric solid-state resonator is used.     

Production of relativistic antihydrogen atoms by pair production with positron capture and measurement of the Lamb shift

A beam of relativistic antihydrogen atoms — the bound state ( e⁺) — can be created by circulating the beam of an antiproton storage ring through an internal gas target. An antiproton which passes through the Coulomb field of a nucleus will create e⁺e⁻ pairs, and antihydrogen will form when a positron is created in a bound instead of continuum state about the antiproton. The cross section for this process is roughly 3Z ² pb for antiproton momenta about 6 GeV/c. A sample of 600 antihydrogen atoms in a low-emittance, neutral beam will be made in 1995 as an accidental byproduct of Fermilab experiment E760. We describe a simple experiment, Fermilab Proposal P862, which can detect this beam, and outline how a sample of a few-10⁴ atoms can be used to measure the antihydrogen Lamb shift to 1 %. Work supported in part by Department of Energy contract DE-AC03-76SF00515 (SLAC). Work supported by Fondo Nacional de Investigación Científica y Tecnológica, Chile.     

Ultralow-threshold Raman lasing with CaF2 resonators

We demonstrate efficient Raman lasing with CaF2 whispering-gallery-mode resonators. Continuous-wave emission threshold is shown to be possible below 1 microW with a 5mm cavity, which is to our knowledge orders of magnitude lower than in any other Raman source. Low-threshold lasing is made possible by the ultrahigh optical quality factor of the cavity, of the order of Q=5x10(10). Stokes components of up to the fifth order were observed at a pump power of 160 microW, and up to the eighth order at 1 mW. A lasing threshold of 15 microW was also observed in a 100 microm CaF2 microcavity. Potential applications are discussed.     

Femtosecond optical vortices in air

We examine the robustness of ultrashort optical vortices propagating freely in the atmosphere. We first approximate the stability regions of femtosecond spinning pulses as a function of their topological charge. Next, we numerically demonstrate that atmospheric optical vortices are capable of conveying high power levels in air over hundreds of meters before they break up into filaments.     

Thin-film spatial filters

A thin-film optical filter used as a one-dimensional spatial filter is presented, and its design is briefly examined. The filter consists of a stack of quarter-wave dielectric layers upon a right-angle prism that selectively cancel a reflected or transmitted plane-wave front for various angles of incidence. Transmittance and reflectance are low-pass functions or high-pass functions of the angle of incidence with a high degree of steepness. In combination, these filters exhibit bandpass transmittance with a variable bandwidth. Applications to detection of extrasolar planets are briefly discussed.