190 research outputs found

    Polarization and relaxation of radon

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    Investigations of the polarization and relaxation of 209^{209}Rn by spin exchange with laser optically pumped rubidium are reported. On the order of one million atoms per shot were collected in coated and uncoated glass cells. Gamma-ray anisotropies were measured as a signal of the alignment (second order moment of the polarization) resulting from the combination of polarization and quadrupole relaxation at the cell walls. The temperature dependence over the range 130^\circC to 220^\circC shows the anisotropies increasing with increasing temperature as the ratio of the spin exchange polarization rate to the wall relaxation rate increases faster than the rubidium polarization decreases. Polarization relaxation rates for coated and uncoated cells are presented. In addition, improved limits on the multipole mixing ratios of some of the main gamma-ray transitions have been extracted. These results are promising for electric dipole moment measurements of octupole-deformed 223^{223}Rn and other isotopes, provided sufficient quantities of the rare isotopes can be produced.Comment: 4 pages, 4 figure

    Structure-property relationships of novel phosphonate-functionalized networks and gels of poly(β-amino esters)

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    pH sensitivity, biodegradability and high biocompatibility make poly(β-amino esters) (PBAEs) important biomaterials with many potential applications including drug and gene delivery and tissue engineering, where their degradation should be tuned to match tissue regeneration rates. Therefore, we synthesize novel phosphonate-functionalized PBAE macromers, and copolymerize them with polyethylene glycol diacrylate (PEGDA) to produce PBAE networks and gels. Degradation and mechanical properties of gels can be tuned by the chemical structure of phosphonate-functionalized macromer precursors. By changing the structure of the PBAE macromers, gels with tunable degradations of 5–97% in 2 days are obtained. Swelling of gels before/after degradation is studied, correlating with the PBAE identity. Uniaxial compression tests reveal that the extent of decrease of the gel cross-link density during degradation is much pronounced with increasing amount and hydrophilicity of the PBAE macromers. Degradation products of the gels have no significant cytotoxicity on NIH 3T3 mouse embryonic fibroblast cells

    Mass Measurement of 27^{27}P for Improved Type-I X-ray Burst Modeling

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    Light curves are the primary observable of type-I x-ray bursts. Computational x-ray burst models must match simulations to observed light curves. Most of the error in simulated curves comes from uncertainties in rprp process reaction rates, which can be reduced via precision mass measurements of neutron-deficient isotopes in the rprp process path. We perform a precise atomic mass measurement of 27^{27}P and use this new measurement to update existing type-I x-ray burst models to produce an improved light curve. High-precision Penning trap mass spectrometry was used to determine the atomic mass of 27^{27}P. Modules for Experiments in Stellar Astrophysics (MESA) was then used to simulate x-ray bursts using a 1D multi-zone model to produce updated light curves. The mass excess of 27^{27}P was measured to be -670.7±\pm 0.6 keV, a fourteen-fold precision increase over the mass reported in AME2020. The 26^{26}Si(p,γp, \gamma)27^{27}P and reverse photodisintegration reaction rates have been determined to a higher precision based on the new, high precision mass measurement of 27^{27}P, and MESA light curves generated using these rates. Changes in the mass of 27^{27}P seem to have minimal effect on XRB light curves, even in burster systems tailored to maximize impact. The mass of 27^{27}P does not play a significant role in x-ray burst light curves. It is important to understand that more advanced models don't just provide more precise results, but often qualitatively different ones. This result brings us a step closer to being able to extract stellar parameters from individual x-ray burst observations. In addition, the Isobaric Multiplet Mass Equation (IMME) has been validated for the A=27,T=3/2A=27, T=3/2 quartet, but only after including a small, theoretically predicted cubic term and utilizing an updated excitation energy for the T=3/2T=3/2 isobaric analogue state of 27^{27}Si.Comment: 8 pages, 7 figure

    Information About Salix Matsudana

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    This article provides information about Salix matsudana, popularly known as willow, and also explains its structure, habitat and medicinal benefits

    Energy properties of rotational bands of 170-174Yb isotopes

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    Accounting for Coriolis mixing of experimentally known rotational bands non-adiabatic effects in energy of low-lying excited states are investigated, within phenomenological model. The Calculations for isotopes 170,172,174,176yb, are carried out. The energy and wave function structure of excited states are calculated. The finding reveals that the bands mixing has been found to have considerable impact on the wave function of low-lying states 0+ and 2+ bands
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