Search for η

We measured missing mass spectrum of the ^{12}C(γ,p) reaction for the first time in coincidence with potential decay products from η^{'} bound nuclei. We tagged an (η+p) pair associated with the η^{'}N→ηN process in a nucleus. After applying kinematical selections to reduce backgrounds, no signal events were observed in the bound-state region. An upper limit of the signal cross section in the opening angle cosθ_{lab}^{ηp}<-0.9 was obtained to be 2.2 nb/sr at the 90% confidence level. It is compared with theoretical cross sections, whose normalization ambiguity is suppressed by measuring a quasifree η^{'} production rate. Our results indicate a small branching fraction of the η^{'}N→ηN process and/or a shallow η^{'}-nucleus potential.

Impact of oral iron challenges on circulating non-transferrin-bound iron in healthy Guatemalan males.

INTRODUCTION: Oral iron as a supplement has been associated with adverse health consequences, especially in the context of young children with active malaria. A potential aggravating role of non-transferrin-bound iron (NTBI) has been proposed. MATERIAL AND METHODS: NTBI responses in both a fasting and post-oral iron dosing situation were related to serum iron concentration and ferritin status. Fasting and 1, 2, and 3 h postdose serum samples were obtained in conjunction with oral ferrous sulfate supplementation in aqueous solution of 0, 15, 30, 60, 120 and 240 mg Fe in a cohort of 8 healthy Guatemalan men over a 9-week metabolic protocol. Hemoglobin, serum ferritin, percent transferrin saturation, serum iron and NTBI were all measured. RESULTS: Circulating levels of serum iron and NTBI increased in a graded fashion in response to oral iron, with the relative increment for NTBI slightly greater than that of iron. Detectable NTBI was occasionally measured in fasting specimens, more frequently in subjects with high ferritin status. Post-iron NTBI responses, by contrast, were higher in normal-ferritin subjects in absolute terms, and rose with increasing postabsorptive serum iron responses. DISCUSSION: The appearance and response of circulating NTBI were consistent with recognized principles of iron regulation.

Corneal hydration affects ablation during laser in situ keratomileusis surgery.

BACKGROUND: Studies in animal eyes indicate that the level of corneal hydration affects the ablation rate of laser surgery; the greater the hydration is, the less the ablation for a given laser pulse. Our study is an assessment in human eyes comparing the effects on ablation by blotting the corneal stromal surface under a corneal flap created for laser in situ keratomileusis (LASIK) procedures between sets of excimer laser pulses, with ablation depth in eyes not blotted between sets of laser pulses. METHODS: We modified the surgical technique for LASIK procedures to assess the effects of the level of hydration on excimer laser ablation depth per pulse. In group 1, 40 eyes underwent LASIK surgery without any modification. Group 2 was composed of 36 eyes having LASIK procedures, but the corneal surfaces were kept relatively dry by blotting of the stromal surface between sets of laser pulses. RESULTS: Six months after surgery, the mean spherical equivalent refractive change was from -8.38 diopters (D) to -1.44 D in group 1 and from -7.93 D to -0.09 D in group 2. For predictability, the deviation from the target refraction after surgery was assessed. Thirty-three percent (13 of 40) in group 1 and 25% (9 of 36) in group 2 were within +/-0.5 D. Forty-eight percent (19 of 40) in group 1 and 50% (18 of 36) in group 2 were within +/-1 D. Six months after surgery, 80% or more in both groups were within +/-2 D. There was myopic regression in all patients. Three months after surgery, regression averaged -0.71 D in group 1 and -1.15 D in group 2. CONCLUSIONS: Corneal hydration levels affect the efficiency of laser ablation in LASIK procedures. With less hydrated corneas, ablation effects were greater than for corneas not blotted during the procedure, but these patients appear to undergo greater myopic regression.

Localized in vivo high-resolution NMR imaging using gradient subencoding technique.

A new spatial localization technique for in vivo high-resolution imaging is presented here. In contrast to other localization techniques that use a series of rf pulses to define a volume of interest, only one rf pulse is utilized in the proposed method for selection of a region to be imaged. Instead of rf pulses for region selection, subencoding gradient pulses are used for the localization together with a convolution process on each phase-encoding gradient by a set of additional gradients (e.g., y direction). Then the 2-D localization is completed by restricting the bandwidth in the readout direction (e.g., x direction). The latter is simply achieved by using a low-pass filter in the receiver system. By applying this technique on a human body, localized in vivo high-resolution images are obtained for the knee with much improved resolution. 100 x 100 microns in-plane (x,y plane) resolution images obtained from the human knee demonstrate that localized in vivo high-resolution imaging for both human and animals is possible with an in-plane resolution of below 100 microns.

Nuclear magnetic resonance microscopy with 4-microns resolution: theoretical study and experimental results.

Nuclear magnetic resonance (NMR) microscopy with 4-microns resolution, a step closer to the 1-micron resolution with which in vivo cellular imaging would be possible is described. An analysis of the ultimate resolution and voxel size dependent signal-to-noise ratio (SNR) in NMR microscopy is presented and experimentally verified. For microscopic scale objects (less than 1-mm diameter), the SNR based on the geometrical scale factor(s) is found to be proportional to sn where n less than 2, rather than n = 3 as previously supposed. This comes about because of a drastic reduction in sample noise coupled with a significant sensitivity gain realized in small diameter radiofrequency coils. A new pulse sequence which reduces both diffusion dependent resolution degradation and signal attenuation is presented. The selection of optimal bandwidth and acquisition time for maximal SNR is discussed. Experimental results obtained on both a 2.0-T whole-body system and a 7.0-T small bore system adapted for microscopy indicate the potentials of 4-microns resolution microscopy with the existing magnets.