ABSTRACT
A theoretical underpinning of the standard model of fundamental particles and interactions is CPT invariance, which requires that the laws of physics be invariant under the combined discrete operations of charge conjugation, parity and time reversal. Antimatter, the existence of which was predicted by Dirac, can be used to test the CPT theorem-experimental investigations involving comparisons of particles with antiparticles are numerous. Cold atoms and anti-atoms, such as hydrogen and antihydrogen, could form the basis of a new precise test, as CPT invariance implies that they must have the same spectrum. Observations of antihydrogen in small quantities and at high energies have been reported at the European Organization for Nuclear Research (CERN) and at Fermilab, but these experiments were not suited to precision comparison measurements. Here we demonstrate the production of antihydrogen atoms at very low energy by mixing trapped antiprotons and positrons in a cryogenic environment. The neutral anti-atoms have been detected directly when they escape the trap and annihilate, producing a characteristic signature in an imaging particle detector.
ABSTRACT
Aspartame (L-aspartyl-L-phenylalanine methyl ester) is a widely used high potency dipeptide sweetener. Developmental toxicology studies have been performed in several species documenting no effects of high doses of aspartame. Recently, a study by Mahalik and Gautieri [1984) Res. Commun. Psychol. Psychiatry Behav. 9, 385-403) reported a delay in the achievement age for the visual placing response in mice pups after maternal administration of high dosages of aspartame during late gestation. In the present study developmental parameters were determined in offspring of CF-1 mice after maternal administration of aspartame at 500, 1000, 2000, and 4000 mg/kg body wt by oral gavage. Aspartame was administered on Days 15 through 18 of gestation. Maternal body weight, food consumption, gestation length, reproductive indices, and litter size were not affected by aspartame treatment. In the pups, body weights, negative geotaxis, and surface and midair righting reflexes were not altered by treatment. There was no delay in the development of the visual placing response regardless of the method employed for assessment (grid or rope) or the manner by which the data were analyzed. There were also no changes in time of eye opening, reflex pupil closure, and ophthalmoscopic examination in the offspring. Thus, neither physical nor functional development was altered in mice after in utero exposure to extremely large dosages of aspartame. More specifically, in utero exposure to aspartame did not affect the development of the visual system in mice.
