403 research outputs found
Dose-dependent effect of ghrelin on gastric emptying in rats and the related mechanism of action
AbstractThe aim of this study was to investigate the dose-dependent effect of ghrelin on gastric emptying in rats and the related mechanism of action. Sixty Wistar rats were randomized into control and test groups, which respectively received intraperitoneal injection of normal saline and ghrelin at different doses (0.5 nmol/kg, 1.0 nmol/kg, 1.5 nmol/kg, 2.0 nmol/kg, and 2.5 nmol/kg). After 45 minutes, all rats were gavaged with semisolid paste. The gastric emptying rate was determined 30 minutes later, and the plasma cholecystokinin level was tested by radioimmunoassay. The mean gastric emptying rate in the test groups was significantly higher than in the control group (38.24 ± 7.15% and 27.18 ± 2.37%, respectively, p < 0.05). Medium and high doses of ghrelin (1.0 nmol/kg, 1.5 nmol/kg, 2.0 nmol/kg, and 2.5 nmol/kg), but not low dose (0.5 nmol/kg), accelerated the gastric emptying. In addition, the plasma cholecystokinin level in the test groups was significantly higher than in the control group (p < 0.01). The gastric emptying rate was positively correlated with the plasma cholecystokinin level (p < 0.01). Intraperitoneal injection of ghrelin at medium and high doses significantly accelerated gastric emptying in rats
Nonequilibrium dynamics of the localization-delocalization transition in the non-Hermitian Aubry-Andr\'{e} model
In this paper, we investigate the driven dynamics of the localization
transition in the non-Hermitian Aubry-Andr\'{e} model with the periodic
boundary condition. Depending on the strength of the quasi-periodic potential
, this model undergoes a localization-delocalization phase transition.
We find that the localization length satisfies with being the distance from the critical
point and being a universal critical exponent independent of the
non-Hermitian parameter. In addition, from the finite-size scaling of the
energy gap between the ground state and the first excited state, we determine
the dynamic exponent as . The critical exponent of the inverse
participation ratio (IPR) for the th eigenstate is also determined as
. By changing linearly to cross the critical point, we
find that the driven dynamics can be described by the Kibble-Zurek scaling
(KZS). Moreover, we show that the KZS with the same set of the exponents can be
generalized to the localization phase transitions in the excited states
A Sliding Mode based Cascade Observer for Estimation and Compensation Controller
The sliding mode observer can estimate the system state and the unknown
disturbance, while the traditional single-layer one might still suffer from
high pulse when the output measurement is mixed with noise. To improve the
estimation quality, a new cascade sliding mode observer containing multiple
discontinuous functions is proposed in this letter. It consists of two layers:
the first layer is a traditional sliding mode observer, and the second layer is
a cascade observer. The measurement noise issue is considered in the source
system model. An alternative method how to design the observer gains of the two
layers, together with how to examine the effectiveness of the compensator based
closed-loop system, are offered. A numerical example is provided to demonstrate
the effectiveness of the proposed method. The observation structure proposed in
this letter not only smooths the estimated state but also reduces the control
consumption
- …