Discovery of underground argon with low level of radioactive 39Ar and possible applications to WIMP dark matter detectors

We report on the first measurement of 39Ar in argon from underground natural gas reservoirs. The gas stored in the US National Helium Reserve was found to contain a low level of 39Ar. The ratio of 39Ar to stable argon was found to be <=4x10-17 (84% C.L.), less than 5% the value in atmospheric argon (39Ar/Ar=8x10-16). The total quantity of argon currently stored in the National Helium Reserve is estimated at 1000 tons. 39Ar represents one of the most important backgrounds in argon detectors for WIMP dark matter searches. The findings reported demonstrate the possibility of constructing large multi-ton argon detectors with low radioactivity suitable for WIMP dark matter searches.Comment: 6 pages, 2 figures, 2 table

Modern microwave methods in solid state inorganic materials chemistry: from fundamentals to manufacturing

No abstract available

STM imaging of symmetry-breaking structural distortion in the Bi-based cuprate superconductors

A complicating factor in unraveling the theory of high-temperature (high-Tc) superconductivity is the presence of a "pseudogap" in the density of states, whose origin has been debated since its discovery [1]. Some believe the pseudogap is a broken symmetry state distinct from superconductivity [2-4], while others believe it arises from short-range correlations without symmetry breaking [5,6]. A number of broken symmetries have been imaged and identified with the pseudogap state [7,8], but it remains crucial to disentangle any electronic symmetry breaking from pre-existing structural symmetry of the crystal. We use scanning tunneling microscopy (STM) to observe an orthorhombic structural distortion across the cuprate superconducting Bi2Sr2Can-1CunO2n+4+x (BSCCO) family tree, which breaks two-dimensional inversion symmetry in the surface BiO layer. Although this inversion symmetry breaking structure can impact electronic measurements, we show from its insensitivity to temperature, magnetic field, and doping, that it cannot be the long-sought pseudogap state. To detect this picometer-scale variation in lattice structure, we have implemented a new algorithm which will serve as a powerful tool in the search for broken symmetry electronic states in cuprates, as well as in other materials.Comment: 4 figure

Solute transport in cartilage undergoing cyclic deformation

There are no blood vessels in cartilage to transport nutrients and growth factors to chondrocytes dispersed throughout the cartilage matrix. Insulin-like growth factor-I (IGF-I) is a large molecule with an important role in cartilage growth and metabolism, however, it first must reach the chondrocytes to exert its effect. While diffusion of IGF-I through cartilage is possible, it has been speculated that cyclic loading can enhance the rate of solute transport within cartilage. To better understand this process, here a one-dimensional axisymmetric mathematical model is developed to examine the transport of solutes through a cylindrical plug of cartilage undergoing cyclic axial deformation in the range of 10(-3) -1 Hz. This study has revealed the role of timescales in interpreting transport results in cartilage. It is shown that dynamic strains can either enhance or inhibit IGF-I transport at small timescales (< 20 min after onset of loading), depending on loading frequency. However, on longer timescales it is found that dynamic loading has negligible effect on IGF-I transport. Most importantly, in all cases examined the steady state IGF-I concentration did not exceed the fixed boundary value, in contrast to the predictions of Mauk et al. (2003)