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J Lucas

Publications and source records attributed to J Lucas.

At least 145 records · Page 8Linked to original sources
PubMed1971

Improvements in tests of long-range charge independence.

The procedure used to determine the pionnucleon coupling constant g(2) from multi-energy fits to nucleon-nucleon (N-N) scattering data has been shortened without a material loss of accuracy. The g(2) presetting effect is discussed in connection with the limited accuracy of g(2) determinations in general and the possibilities of the "optimized polynomial expansions". The desirability of the Yale graded introduction of one-pion exchange (OPE)-to-"searched" transition energies (E(tr)) is brought out. Corrections for virtual discontinuities in phase-shift-energy dependence at the E(tr) decreased the violation of long-range charge independence (LRCI). The effect of two-pion exchange (TPE) has been calculated on the ps theory as approximately 1 for go(2)(p-p) - go(2)(n-p), go(2) = g(2)/[unk]c; a result consistent with LRCI. Searching all phase parameters including g(2) for both isospin values I in g(2) determinations from n-p data, but with fixed I = 1 non-OPE phases as deduced from p-p data in the base search with frozen g(2), the OPE effect of the neutral pion, pi degrees , was separated from that of the charged pion, pi(c). The g(2) for pi(c) in n-p scattering is determined with much better statistical accuracy than that for pi degrees . The overall n-p value of g(2) is nearly equal to that for pi(c). The results suggest that the distinction between p-p and n-p values of g(2), if present, is in first approximation that arising from the difference between pi degrees -N and pi(c)-N couplings. Some limitations on the validity of the conclusions are mentioned.

Journal Article↗
PubMedDate not supplied

Low-dose esterified estrogen therapy: effects on bone, plasma estradiol concentrations, endometrium, and lipid levels. Estratab/Osteoporosis Study Group.

BACKGROUND: Prospective studies have shown that doses equivalent to conjugated equine estrogens of 0.625 mg/d or higher are needed to produce a significant increase in bone mineral density of the lumbar spine. OBJECTIVES: To determine the effects of unopposed esterified estrogens on bone mineral density, lipid levels, and endometrial tissue structure, and to relate these effects to changes in plasma estradiol levels. METHODS: Four hundred six postmenopausal women were given calcium, 1000 mg/d, and randomly assigned to receive continuous esterified estrogens (0.3, 0.625, or 1.25 mg/d) or placebo for 24 months. Bone mineral density measurements and endometrial and laboratory assessments were conducted every 6 months; plasma estradiol concentrations were measured after 12, 18, and 24 months. RESULTS: All doses of esterified estrogens produced significant increases in bone mineral density of the lumbar spine compared with baseline and with placebo at 6, 12, 18, and 24 months. Mean plasma estradiol levels increased with esterified estrogens dose, and individual subject bone mineral density changes appeared related to plasma estradiol concentrations. Clinically relevant rates of endometrial hyperplasia were noted only in the groups receiving 0.625 and 1.25 mg of esterified estrogens daily. Lipid changes were dose related and apparent in all groups. CONCLUSIONS: Esterified estrogens at doses from 0.3 to 1.25 mg/d, administered unopposed by progestin, produce a continuum of positive changes on bone and lipids. Plasma estradiol concentrations increased with esterified estrogens dose and were related to positive bone mineral densities. The 0.3-mg dose resulted in positive bone and lipid changes without inducing endometrial hyperplasia.

Bone Density↗
PubMedDate not supplied

MR-guided percutaneous ethanol ablation of liver tissue in a .2-T open MR system: preliminary study in porcine model.

The purpose of this study was to test the feasibility of MR-guided percutaneous ethanol ablation of liver tissue on a .2-T open MR scanner. Needles were placed by MR guidance first into an ex vivo sheep liver and then into livers of three anesthetized pigs, and injection of 10 ml of 96% alcohol was performed. T1 fast low-angle shot (FLASH), T2 turbo spin echo (TSE), and T1 spin echo (SE) images were obtained after incremental volumes of injection. In one pig, simultaneous injection of saline into normal liver was also performed with subsequent pathological correlation. Ethanol-infiltrated liver was hypointense to liver on all sequences, whereas saline caused no tissue signal changes on T1 SE and either isointense or hyperintense changes on T2 TSE images. Pathological examination confirmed ethanol-induced acute liver changes as compared with the control. MR guidance of needle placement and monitoring of ethanol effects on liver tissue is feasible. This may have implications for potential MR-guided hepatic tumor ablation.

Animals↗