A-B Phase Conversion and Coexistence of Superfluid 3He in Aerogel

We have studied phase transition of superfluid ³He at 2.4 MPa in cylindrical aerogel by NMR method. When the liquid is cooled down from the normal state, the A-like phase appears below superfluid transition temperature T _c ^a which is suppressed in comparison with the transition temperature of the bulk liquid. With further cooling below the certain temperature T _ab,c ^a , the A-like phase is converted into the B-like phase gradually. Both phases stably coexist within about 90 μK. When you keep the temperature constant in which both phases coexist, the A-B phase conversion stops. With furthermore cooling, the whole liquid becomes the B-like phase. The cwNMR spectra at the coexistence state suggest that the B-like phase is not uniformly distributed in the A-like phase like a large number of small bubbles in a liquid, but separated as a whole from the A-like phase. By applying a field gradient which changes as a function of square of radius, we found that the A-like phase is in the edge part with a cylindrical shape and the B-like phase is in the central part with a columnar shape.      

Developmental changes in the kinetics of glucose and urea in Holstein calves

Because weaning is the point when the nutrient composition of feed changes for the neonatal ruminant, the present experiment was conducted to assess the developmental changes in the kinetics of glucose and urea over this period, using stable isotopes of glucose and urea, at 4, 13, and 24 wk in calves. Plasma concentrations of nonesterified fatty acids, amino-N, urea-N, and insulin-like growth factor-I increased, but that of growth hormone decreased with age. The plasma glucose concentration increased at 13 wk of age and thereafter decreased at 24 wk of age. The glucose irreversible loss and recycling rates were significantly higher at 4 wk of age than at 13 and 24 wk of age. On the other hand, the irreversible loss and recycling rates of urea, as well as the urea pool size, were higher at 24 wk of age than at 4 and 13 wk. It is concluded that weaning at 6 wk is the pivotal time for the alteration of glucose kinetics. However, the aging process, but not weaning, is important for changes in the kinetics of urea in calves.     

Oral clonidine premedication reduces minimum alveolar concentration of sevoflurane for tracheal intubation in children

BACKGROUND: Sevoflurane is a useful anesthetic for inhalational induction in children because of its low solubility in blood and relatively nonpungent odor. Clonidine has sedative and anxiolytic properties and reduces the requirement for inhalation agents. Nitrous oxide (N2O) also decreases the requirement of inhaled anesthetics, but the effect is variable. The minimum alveolar concentration for tracheal intubation (MAC(TI)) of sevoflurane was assessed with and without N2O and clonidine premedication. METHODS: Seventy-two patients, aged 3-11 yr, were assigned to one of six groups (n = 12 each). They received one of three preanesthetic medications (two groups for each premedication): placebo (control), 2 microg/kg oral clonidine or 4 microg/kg oral clonidine. In one group of each premedication, anesthesia was induced with sevoflurane in oxygen; in the other group, anesthesia was induced with sevoflurane in the presence of 60% N2O. Each concentration of sevoflurane at which tracheal intubation was attempted was predetermined according to Dixon's up-and-down method and held constant for at least 20 min before the trial RESULTS: The MAC(TI) of sevoflurane in the absence of N2O (mean +/- SEM) was 3.2 +/- 0.2%, 2.5 +/- 0.1%, and 1.9 +/- 0.2% in the control, 2-microg/kg clonidine, and 4-microg/kg clonidine groups, respectively. Nitrous oxide (60%) decreased the MAC(TI) of sevoflurane by 26%, 24%, and 27% in the control, 2-microg/kg clonidine, and 4-microg/kg clonidine groups. CONCLUSIONS: Oral clonidine premedication decreased the MAC(TI) of sevoflurane. Nitrous oxide also decreased the MAC(TI). The combination of clonidine and N2O lessened the MAC(TI) of sevoflurane more than did either drug alone.