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The feasibility of brain MRI with laser-polarized 129Xe in a small animal model is demonstrated. Naturally abundant 129Xe is polarized and introduced into the lungs of Sprague-Dawley rats. Polarized xenon gas dissolves in the blood and is transported to the brain where it accumulates in brain tissue. Spectroscopic studies reveal a single, dominant, tissue-phase NMR resonance in the head at 194.5 ppm relative to the gas phase resonance. Images of 129Xe in the rat head were obtained with 98-microliter voxels by 2D chemical shift imaging and show that xenon is localized to the brain. This work establishes that nuclear polarization produced in the gas phases survives transport to the brain where it may be imaged. Increases in polarization and delivered volume of 129Xe will allow clinical measurements of regional cerebral blood flow.

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We have measured the ratio g& /F& over the range 0.029 ( x ( 0.8 and 1.3 ( Q~( 10 (GeV/c) using deep-inelastic scattering of polarized electrons from polarized ammonia. An evaluation of the integral fo g~(x, Q2) dx at fixed Q2 = 3 (GeV/c)2 yields 0.127~0.004(stat)~0.010(syst), in agreement with previous experiments, but well below the Ellis-Jaffe sum rule prediction of 0.160~0.006. In the quark-parton model, this implies Aq = 0.27~0.10.PACS numbers: 13.60. Hb, 11. 55.Hx, 13.88.+e, 14.20.Dh Measurements of the longitudinal and transverse spindependent structure functions gi(x, Q ) and gq(x, Q ) for deep-inelastic lepton-nucleon scattering have become an increasingly important tool in unraveling the complex structures of the proton and neutron.Of particular interest are the integrals I t (Q ) = f"g (x,tQ )dx the proton and I i (Q ) = ftI gi (x, Q ) dx for the neutron.

The first magnetic resonance imaging studies of laser-polarized 129 Xe, dissolved in the blood and tissue of the lungs and the heart of Sprague-Dawley rats, are described. 129 Xe resonances at 0, 192, 199, and 210 ppm were observed and assigned to xenon in gas, fat, tissue, and blood, respectively. One-dimensional chemical-shift imaging (CSI) reveals xenon magnetization in the brain, kidney, and lungs. Coronal and axial twodimensional CSI show 129 Xe dissolved in blood and tissue in the thorax. Images of the blood resonance show xenon in the lungs and the heart ventricle. Images of the tissue resonance reveal xenon in lung parenchyma and myocardium. The 129 Xe spectrum from a voxel located in the heart ventricle shows a single blood resonance. Time-resolved spectroscopy shows that the dynamics of the blood resonance match the dynamics of the gas resonance and demonstrates efficient diffusion of xenon gas to the lung parenchyma and then to pulmonary blood. These observations demonstrate the utility of laser-polarized 129

Specific medical findings associated with reasons for placement provide health professionals with additional information to assess more accurately the health care needs of children entering foster care. As important, screening tests revealed high rates of vision problems and exposures to tuberculosis, warranting earlier and more comprehensive screening. Finally, children who have endured variations of neglect or failed placement may have more health problems than anticipated previously.

The A-dependence of the quasielastic A(e, e ′ p) reaction has been studied at SLAC with 2 H, C, Fe, and Au nuclei at momentum transfers Q 2 = 1, 3, 5, and 6.8 (GeV/c) 2 . We extract the nuclear transparency T (A, Q 2 ), a measure of the average probability that the struck proton escapes from the nucleus A without interaction. Several calculations predict a significant increase in T with momentum transfer, a phenomenon known as Color Transparency. No significant rise within errors is seen for any of the nuclei studied.PACS numbers: 25.30 In 1982, Mueller and Brodsky [1] proposed that in wide angle exclusive processes, the soft initial and final state interactions (ISI and FSI) of hadrons in nuclei would vanish at high energies. This effect, originally based on arguments using perturbative QCD, is called "Color Transparency" (CT), in reference to the disappearance of the color forces between the hadrons and nuclei. Evidence for the CT effect can be sought by measurement of the nuclear transparency T , defined as the ratio of the measured cross section to the cross section expected in the limit of complete CT (i.e., no ISI or FSI), as a function of the 4-momentum transfer squared, Q 2 , and nuclear mass, A. For CT to be observable in quasielastic A(e, e ′ p) scattering, the recoiling proton must maintain its reduced interaction with other nucleons over a distance comparable to the nuclear radius. This is probed directly by measuring the A dependence of T . At low energies, T < 1 because of absorption or deflection of the hadrons by ISI and FSI with the nucleus. As the energy increases, and if CT effects begin to dominate the scattering, T should increase towards unity [2]. Some recent models of CT predict significant increases in T for Q 2 as low as 5 (GeV/c) 2 [2-6]. We present measurements of T for the reaction A(e, e ′ p) on 2 H, C, Fe, and Au nuclei at Q 2 = 1, 3, 5, and 6.8 (GeV/c) 2 .The first experiment to investigate CT was performed by Carroll et al. [7] using simultaneous measurements of A(p, 2p) and H(p, 2p) reaction rates at Brookhaven National Laboratory. Their results showed T increasing for Q 2 ≃ 3-8 (GeV/c) 2 , but then decreasing for Q 2 ≃ 8-11 (GeV/c) 2 . Because of the subsequent decrease, the rise at lower momentum transfer cannot be taken as an unambiguous signal of CT. Ralston and Pire [6] suggest that the maximum in T is due to a soft process that interferes with the perturbative QCD amplitude in free proton-proton scattering but is suppressed in the nuclear environment. Such ambiguities should be smaller in A(e, e ′ p) reactions because of the simplicity of the elementary electron-proton interaction compared to the proton-proton interaction.

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