Spin-dependent lepton-nucleon scattering data have been used to investigate the validity of the concept of quark-hadron duality for the spin asymmetry A1. Longitudinally polarized positrons were scattered off a longitudinally polarized hydrogen target for values of Q2 between 1.2 and 12 GeV2 and values of W2 between 1 and 4 GeV2. The average double-spin asymmetry in the nucleon resonance region is found to agree with that measured in deep-inelastic scattering at the same values of the Bjorken scaling variable x. This finding implies that the description of A1 in terms of quark degrees of freedom is valid also in the nucleon resonance region for values of Q2 above 1.6 GeV2.

Journal Article↗

PubMed2001

Longitudinal electroproduction of charged pions from (1)H, (2)H, and (3)He.

Separated longitudinal and transverse cross sections for charged pion electroproduction from (1)H, (2)H, and (3)He were measured at Q(2) = 0.4 (GeV/c)(2) for two values of the invariant mass, W = 1.15 GeV and W = 1.60 GeV, in a search for a mass dependence which would signal the effect of nuclear pions. This is the first such study that includes recoil momenta significantly above the Fermi surface. The longitudinal cross section, if dominated by the pion-pole process, should be sensitive to nuclear pion currents. Comparisons of the longitudinal cross section target ratios to a quasifree calculation reveal a significant suppression in (3)He at W = 1.60 GeV. The W = 1.15 GeV results are consistent with simple estimates of the effect of nuclear pion currents, but are also consistent with pure quasifree production.

Journal Article↗

PubMed2001

Observation of polarization in bottomonium production at square root of s = 38.8 GeV.

We present a measurement of the polarization observed for bottomonium states produced in p-Cu collisions at square root of s = 38.8 GeV. The angular distribution of the decay dimuons of the Upsilon(1S) state shows no polarization at small values of the fractional longitudinal momentum x(F) and transverse momentum p(T) but significant positive transverse production polarization for either p(T)>1.8 GeV/c or for x(F)>0.35. The Upsilon(2S+3S) (unresolved) states show a large transverse production polarization at all values of x(F) and p(T) measured. These observations challenge NRQCD calculations of the polarization expected in the hadronic production of bottomonium states.

Journal Article↗

PubMed2001

Hydrocortisone replacement dosage influences intraocular pressure in patients with primary and secondary hypocortisolism.

BACKGROUND: It has been suggested that the variation of intraocular pressure (IOP) during the day follows the diurnal variation of serum cortisol. There is also a higher risk of ocular hypertension and glaucoma in patients taking excessive oral steroid treatment. We assessed whether different replacement doses of hydrocortisone (HC) influenced IOP. METHODS: Seventeen patients (six Addison's disease, 11 hypopituitarism; seven males) aged 24-58 years mean 42.7 years and 20 control subjects (nine males) aged 20--59 years mean 38.7 years were studied. On the first visit, the 17 patients had been taking HC replacement doses, 20 mg morning and 10 mg afternoon. Serum cortisol and IOP in both eyes (Goldmann applanation tonometer) were measured at 0900, 1100, 1300, 1500, 1700 hours with HC 20 mg taken after the 0900 h assessment. The dose of HC was then reduced to 10 mg morning and 10 mg afternoon for 1 week and the measurements were repeated in 16 patients, with HC 10 mg taken at 0900 h. RESULTS: In the patients the peak serum cortisol occurred at 1100 h after the 0900 h HC dose. Cortisol levels were significantly higher at 1100, 1300, 1500 and 1700 h after taking 20 mg compared to 10 mg HC. The mean (SEM) IOP (mmHg) was significantly higher after 20 mg HC compared with 10 mg HC at 1300 h: 14.7(0.6) v 13.1(0.6) (P = 0.004) and at 1500 h: 14.4(0.6) v 13.1(0.5) (P = 0.04). The total mean (SEM) daily IOP score was significantly higher after 20 mg HC compared with 10 mg HC: 14.5(0.3) v 13.5(0.3) (P = 0.0002). The total mean (SEM) daily IOP score after the 20 mg HC dose compared with the control subjects was: 14.5(0.3) v 13.7(0.3) (P = 0.08). CONCLUSION: Intraocular pressures during the day are influenced by the morning hydrocortisone replacement dosage with significantly higher intraocular pressure levels in the early afternoon following 20 mg compared with 10 mg. A morning hydrocortisone dose of 10 mg leads to a more physiological intraocular pressure profile during the day. These data support the view that a daily replacement dose of 30 mg hydrocortisone may be excessive.

Addison Disease↗

PubMed1999

Bilateral microcornea and unilateral macrophthalmia resulting in incorrect intraocular lens selection.

A 79-year-old man with symmetrical microcornea and a dense unilateral nuclear sclerotic cataract had cataract extraction by phacoemulsification. The SRK/T formula suggested a 10.0 diopter (D) intraocular lens (IOL) for emmetropia (axial length 26.58 mm). The non-cataract eye required a 25.0 D IOL for emmetropia (axial length 21.51 mm). Biometric measurements were rechecked, and an 18.0 D IOL was implanted (axial length 24.02 mm). The 6 week postoperative refraction of -13.0 + 2.0 x 25 necessitated IOL exchange (10.0 D). Six weeks postexchange, the refraction was -3.75 + 2.5 x 30. This illustrates that symmetrical anterior microphthalmos does not always coexist with symmetrical posterior microphthalmos. Awareness of the association of symmetrical microcornea and unilateral colobomatous macrophthalmia may aid appropriate IOL selection in future cases.

Aged↗

PubMed1998