Observation of two-neutrino double-beta decay in 136Xe with the EXO-200 detector

We report the observation of two-neutrino double-beta decay in (136)Xe with T(1/2) = 2.11 ± 0.04(stat) ± 0.21(syst) × 10(21) yr. This second-order process, predicted by the standard model, has been observed for several nuclei but not for (136)Xe. The observed decay rate provides new input to matrix element calculations and to the search for the more interesting neutrinoless double-beta decay, the most sensitive probe for the existence of Majorana particles and the measurement of the neutrino mass scale.     

Preparation of water-soluble magnetic nanocrystals using aryl diazonium salt chemistry

A novel and facile methodology for the in situ surface functionalization of Fe(3)O(4) nanoparticles is proposed, based on the use of aryl diazonium salts chemistry. The grafting reaction involves the formation of diazoates in a basic medium. These species are unstable and dediazonize along a homolytic pathway to give aryl radicals which further react with the Fe(3)O(4) NPs during their formation and stop their growth. Advantages of the present approach rely not only on the simplicity, rapidity, and efficiency of the procedure but also on the formation of strong Fe(3)O(4)-aryl surface bonds, highly suitable for further applications.     

Integrability,computation and applications

The study of integrable systems and the notion of integrability has been re-energized with the discovery that infinite-dimensional systems such as the Korteweg-de Vries equation are integrable. In this paper, the following novel aspects of integrability are described: (i) solutions of Darboux, Brioschi, Halphen-type systems and their relationships to monodromy problems and automorphic functions, (ii) computational chaos in integrable systems, (iii) we explain why we believe that homoclinic structures and homoclinic chaos associated with nonlinear integrable wave problems, will be observed in appropriate laboratory experiments.     

Free channel fourier transform in the long-rangen-body problem

Research supported by NSF grant DMS-8807816.     

LINC-NIRVANA: MCAO toward Extremely Large Telescopes

LINC-NIRVANA is a Fizeau (imaging) interferometer exploiting the full spatial resolution of a 23 m class telescope in the combined beam of the Large Binocular Telescope supported through Multi-Conjugated Adaptive Optics (MCAO). By means of science cases, we show how LINC-NIRVANA takes advantage of the MCAO, increasing the sky coverage of the instrument and the field of view for the Fringe and Flexure tracker. We introduce the MCAO system of LINC-NIRVANA in detail, which in a first step will be installed with two deformable mirrors per arm and has the provision to be upgraded with a third mirror. The MCAO system implements several novel concepts proposed for extremely large telescopes, such as layer oriented MCAO, optical co-adding of guide stars, or Multiple Field of View sensing. LINC-NIRVANA will demonstrate some of the concepts for the first time on sky. To cite this article: W. Gaessler et. al., C. R. Physique 6 (2005).     

Optical backward mixing in sodium nitrite

We present an experimental study of backward mixing of argon laser lines and CO laser lines to generate visible light in sodium nitrite. Angle tuning has been measured. Some special aspects of the observed super narrow band-width of backward interactions are discussed.     

Size-dependent magnetic properties of CoFe2O4 nanoparticles prepared in polyol

Highly crystalline CoFe(2)O(4) nanoparticles with different diameters ranging from 2.4 to 6.1 nm have been synthesized by forced hydrolysis in polyol. The size can be controlled through adjusting the nominal water/metal molar ratio. X-ray diffraction, transmission electron microscopy, x-ray absorption spectroscopy and (57)Fe M?ssbauer spectrometry were employed to investigate the structure and the microstructure of the particles produced. Magnetic measurements performed on these particles show that they are superparamagnetic with a size-dependent blocking temperature. At 5 K, high saturation magnetization (~85 emu g(-1)) approaching that of the bulk was found for the larger particles, whereas a very large coercivity (14.5 kOe) is observed for the 3.5 nm sized particles.     

Ultrafast mass spectrometry based bioanalytical method for digoxin supporting an in vitro P-glycoprotein (P-gp) inhibition screen

The evaluation of interactions between drug candidates and transporters such as P‐glycoprotein (P‐gp) has gained considerable interest in drug discovery and development. Inhibition of P‐gp can be assessed by performing bi‐directional permeability studies with in vitro P‐gp‐expressing cellular model systems such as Caco‐2 (human colon carcinoma) cells, using digoxin as a substrate probe. Existing methodologies include either assaying ³H‐digoxin with liquid scintillation counting (LSC) detection or assaying non‐labeled digoxin with liquid chromatography–tandem mass spectrometric (LC‐MS/MS) analysis at a speed of several minutes per sample. However, it is not feasible to achieve a throughput high enough using these approaches to sustain an early liability screen that generates more than a thousand samples on a daily basis. To address this challenge, we developed an ultrafast (9 s per sample) bioanalytical method for digoxin analysis using RapidFire?, an on‐line solid‐phase extraction (SPE) system, with MS/MS detection. A stable isotope labeled analog, d3‐digoxin, was used as internal standard to minimize potential ionization matrix effect during the RF‐MS/MS analysis. The RF‐MS/MS method was more than 16 times faster than the LC‐MS/MS method but demonstrated similar sensitivity, selectivity, reproducibility, linearity and robustness. P‐gp inhibition results of multiple validation compounds obtained with this RF‐MS/MS method were in agreement with those generated by both the LC‐MS/MS method and the ³H‐radiolabel assay. This method has been successfully deployed to assess P‐gp inhibition potential as an important early liability screen for drug–transporter interaction. Copyright © 2011 John Wiley & Sons, Ltd.     

Specific thermoresponsiveness of PMMA-block-PDMAEMA to selected ions and other factors in aqueous solution

Poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) is a functional polymer that presents positive charges at low and neutral pHs. Copolymers bearing PDMAEMA blocks usually show a thermal behavior in water marked by a lower critical solution temperature (LCST). This behavior suggests them as interesting “smart” materials for several applications such as water decontamination and many others. In the present work, the LCST of a poly(methyl methacrylate)-block-poly(2-(dimethylamino)ethyl methacrylate) (PMMA-b-PDMAEMA) synthesized by RAFT was measured in several conditions in aqueous solution. It was demonstrated that ionic strength modulates the LCST and this effect depends on the nature of the anion. For instance, weakly hydrated anions such as perchlorate make the LCST lower as the ionic strength gets higher, on the other hand, strongly hydrated ions such as sulfate have not shown a marked effect on LCST. Those results were understood as a consequence of the specific binding of each anion onto the positive-charged PDMAEMA chains, changing the interactions between the chains and water molecules, as well as affecting their pK _a and the ionic interactions. Also, as expected, the LCST is very dependent on pH. The overall results point to the opportunity of modulating very precisely the thermal behavior of PMMA-b-PDMAEMA systems by usual solution conditions such as the type of the anion present.