326 research outputs found
Resonance Patterns in a Stadium-shaped Microcavity
We investigate resonance patterns in a stadium-shaped microcavity around
, where is the refractive index, the vacuum
wavenumber, and the radius of the circular part of the cavity. We find that
the patterns of high resonances can be classified, even though the
classical dynamics of the stadium system is chaotic. The patterns of the high
resonances are consistent with the ray dynamical consideration, and appears
as the stationary lasing modes with low pumping rate in the nonlinear dynamical
model. All resonance patterns are presented in a finite range of .Comment: 8 pages, 9 figure
Scarred Resonances and Steady Probability Distribution in a Chaotic Microcavity
We investigate scarred resonances of a stadium-shaped chaotic microcavity. It
is shown that two components with different chirality of the scarring pattern
are slightly rotated in opposite ways from the underlying unstable periodic
orbit, when the incident angles of the scarring pattern are close to the
critical angle for total internal reflection. In addition, the correspondence
of emission pattern with the scarring pattern disappears when the incident
angles are much larger than the critical angle. The steady probability
distribution gives a consistent explanation about these interesting phenomena
and makes it possible to expect the emission pattern in the latter case.Comment: 4 pages, 5 figure
Thyroid dysfunction in preterm infants born before 32 gestational weeks
Background
Thyroid hormones are critical for growth and brain development during the newborn period and infancy. Because of delayed maturation of the hypothalamic-pituitary-thyroid axis in preterm infants, thyroid dysfunction is common, and thyroid stimulating hormone (TSH) elevation is often delayed in preterm infants. The objective of this study was to determine the incidence of thyroid dysfunction requiring levothyroxine treatment and to identify its risk factors in preterm infants.
Methods
A retrospective cohort study was performed on preterm infants who were born before 32 gestational weeks and admitted to a single tertiary academic center for more than 8 weeks between January 2008 and December 2014. In these infants, serial thyroid function tests (TFTs) measuring serum TSH and free thyroxine (fT4) were routinely performed at 1, 3, and 6 weeks of postnatal age.
Results
Of the 220 preterm infants enrolled, 180 infants underwent TFTs at 1, 3, and 6 weeks of postnatal age and were included in the study. Of the 180 infants, 35 infants (19.4%) were started on levothyroxine treatment based on the results of serial TFTs. Among the 35 infants who were treated with levothyroxine, 16 infants (45.7%) had normal results on the initial TFT. Three of these 16 infants continued to have normal results on the second TFT. Thyroid dysfunction requiring levothyroxine treatment was significantly associated with maternal pregnancy-induced hypertension (adjusted odds ratio 2.64, 95% confidence interval 1.02–6.81).
Conclusions
Thyroid dysfunction requiring levothyroxine treatment occurred in nearly one-fifth of preterm infants born before 32 gestational weeks. Nearly half of the preterm infants who were treated with levothyroxine had normal TSH and fT4 levels at 1 week of postnatal age. The findings of the present study suggest that serial TFTs is important to find preterm infants who require levothyroxine treatment
Factors affecting determination of the optimal ketamine dose for pediatric sedation
Objective Children are sedated before undergoing diagnostic imaging tests in emergency medicine or pediatric sedation anesthesia units. The aim of this study was to identify variables potentially affecting the dose of ketamine required for induction of sedation in pediatric patients undergoing diagnostic imaging. Methods This retrospective study included children aged 0 to 18 years who underwent sedation with ketamine for computed tomography or magnetic resonance imaging in the pediatric sedation anesthesia unit of a tertiary medical center between January 2011 and August 2016. The children’s hemodynamic status and depth of sedation were monitored during the examination. We recorded data on demographics, categories of imaging tests, ketamine doses administered, adverse events, respiratory interventions, and duration of sedation. Data for patients who experienced adverse events were excluded. Results Sixty-six patients were included in the final analysis. Univariate linear regression analysis revealed that patient age, height, and body surface area (BSA) affected the sedative dose of ketamine administered. These three variables showed multicollinearity in multivariate linear regression analysis and were analyzed in three separate models. The model with the highest adjusted R-squared value suggested the following equation for determination of the dose of ketamine required to induce sedation: ketamine dose (mg)=-1.62+0.7×age (months)+36.36×BSA (m2). Conclusion Variables such as age and BSA should be considered when estimating the dose of ketamine required for induction of sedation in pediatric patients
Hole diffusion effect on the minority trap detection and non-ideal behavior of NiO/β-Ga2O3 heterojunction
A NiO/β-Ga2O3 heterojunction was fabricated by sputtering a highly p-doped NiO layer onto β-Ga2O3. This heterojunction showed a low leakage current and a high turn-on voltage (Von) compared to a Ni/β-Ga2O3 Schottky barrier diode. The extracted Von from the NiO/β-Ga2O3 heterojunction's forward current-voltage characteristics was ∼1.64 V, which was lower than the extracted built-in potential voltage (Vbi) obtained from the capacitance-voltage curve. To explain this difference, deep level transient spectroscopy and Laplace-deep level transient spectroscopy were employed to study majority and minority traps in β-Ga2O3 films. A minority trap was detected near the surface of β-Ga2O3 under a reverse bias of −1 V but was not observed at −4 V, indicating its dependence on hole injection density. Using Silvaco TCAD, the hole diffusion length from P+-NiO to β-Ga2O3 was determined to be 0.15 μm in equilibrium, which is increased with increasing forward voltage. This finding explained why the trap level was not detected at a large reverse bias. Moreover, hole diffusion from NiO into β-Ga2O3 significantly affected the β-Ga2O3 surface band bending and impacted transport mechanisms. It was noted that the energy difference between the conduction band minimum (CBM) of β-Ga2O3 and the valence band maximum (VBM) of NiO was reduced to 1.60 eV, which closely matched the extracted Von value. This supported the dominance of direct band-to-band tunneling of electrons from the CBM of β-Ga2O3 to the VBM of NiO under forward bias voltage
Chaos Synchronization of delayed systems in the presence of delay time modulation
We investigate synchronization in the presence of delay time modulation for
application to communication. We have observed that the robust synchronization
is established by a common delay signal and its threshold is presented using
Lyapunov exponents analysis. The influence of the delay time modulation in
chaotic oscillators is also discussed.Comment: 9 pages, 6 figure
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