Dongho Lee

Thermosoftening treatment of the nasotracheal tube before intubation can reduce epistaxis and nasal damage.

We evaluated whether a thermosoftening treatment with warm saline of a nasotracheal preformed tube can improve navigability through the nasal passageways and reduce epistaxis and nasal damage. A total of 150 patients were randomly allocated to three groups: Group I (untreated tube group, n = 50), Group II (35°C treated tube group, n = 50), and Group III (45°C treated tube group, n = 50). In Groups II and III, the tubes were softened at 35 ± 2°C and 45 ± 2°C with warm saline, respectively. In Group I the tube was prepared at room temperature (25 ± 2°C). The incidence of epistaxis and nasal damage in Groups II and III was significantly less than that of Group I (P < 0.05). Despite the more frequent incidence of smooth passage in Group III, no statistical difference was found among the groups. Logistic regression analysis also confirmed that epistaxis was more likely to be reduced when the tube had been thermosoftened (odds ratio = 1.46, 95% confidence interval = 1.02, 2.11). We conclude that simple thermosoftening treatment of the nasotracheal tube with warm saline helps to reduce epistaxis and nasal damage. Implications Thermosoftening treatment of a nasotracheal tube with warm saline before intubation can effectively reduce epistaxis and nasal damage. This technique is safe, easy, and suitable for all types of tubes and does not require additional implements.

Physicochemical properties, pharmacokinetics, and pharmacodynamics of a reformulated microemulsion propofol in rats.

Background:A newly developed microemulsion propofol consisted of 10% purified poloxamer 188 and 0.7% polyethylene glycol 660 hydroxystearate. The authors studied the physicochemical properties, aqueous free propofol concentration, and plasma bradykinin generation. Pharmacokinetics and pharmacodynamics were also evaluated in rats. Methods:The pH, particle size, and osmolarity of microemulsion propofol were measured using a pH meter, particle size analyzer, and cryoscopic osmometer, respectively. The aqueous free propofol and plasma bradykinin were measured by a dialysis method and radioimmunoassay, respectively. Microemulsion propofol was administered by zero-order infusion of 0.5, 1.0, and 1.5 mg · kg−1 · min−1 for 20 min in 30 rats. The electroencephalographic approximate entropy was used as a surrogate measure of propofol effect. Results:The pH, osmolarity, and particle size of microemulsion propofol are 7.5, 280 mOsm/l, and 67.0 ± 28.5 nm, respectively. The aqueous free propofol concentration in microemulsion propofol was 63.3 ± 1.2 μg/ml. When mixed with human blood, microemulsion propofol did not generate bradykinin in plasma. Although microemulsion propofol had nonlinear pharmacokinetics, a two-compartment model with linear pharmacokinetics best described the time course of the propofol concentration as follows: V1 = 0.143 l/kg, k10 = 0.175 min−1, k12 = 0.126 min−1, k21 = 0.043 min−1. The pharmacodynamic parameters in a sigmoid Emax model were as follows: E0 = 1.18, Emax = 0.636, Ce50 = 1.87 μg/ml, γ = 1.28, ke0 = 1.02 min−1. Conclusions:Microemulsion propofol produced a high concentration of free propofol in the aqueous phase. For the applied dose range, microemulsion propofol showed nonlinear pharmacokinetics.

Influence of surface properties on the performance of Cu(In,Ga)(Se,S)2 thin-film solar cells using Kelvin probe force microscopy

We have investigated the sulfurization process in a Cu(In,Ga)(Se,S)2 (CIGSS) absorber layer fabricated by a two-step sputter and selenization/sulfurization method in order to make an ideal double-graded band-gap profile and increase the open circuit voltage (Voc). The sulfurization process was controlled by temperature from 570 °C to 590 °C without changing H2S gas concentration and reaction time. Although the energy band-gap of the CIGSS absorber layer was increased with increasing sulfurization temperature, the Voc of the completed CIGSS device fabricated at 590 °C sulfurization temperature did not increase. In order to investigate this abnormal Voc behavior, the CIGSS absorber layer was measured by local electrical characterization utilizing Kelvin probe force microscopy, especially in terms of grain boundary potential and surface work function. Consequently, the abnormal Voc behavior was attributed to the degradation of grain boundary passivation by the strong sulfurization process. The optimum sulfurization temperature plays an important role in enhancement of grain boundary passivation. It was also verified that the Voc degradation in the CIGSS solar cell fabricated by the two-step method is more influenced by the grain boundary passivation quality in comparison with the slight non-uniformity of material composition among grains.

Direct evidence of void passivation in Cu(InGa)(SSe)2 absorber layers

We have investigated the charge collection condition around voids in copper indium gallium sulfur selenide (CIGSSe) solar cells fabricated by sputter and a sequential process of selenization/sulfurization. In this study, we found direct evidence of void passivation by using the junction electron beam induced current method, transmission electron microscopy, and energy dispersive X-ray spectroscopy. The high sulfur concentration at the void surface plays an important role in the performance enhancement of the device. The recombination around voids is effectively suppressed by field-assisted void passivation. Hence, the generated carriers are easily collected by the electrodes. Therefore, when the S/(S + Se) ratio at the void surface is over 8% at room temperature, the device performance degradation caused by the recombination at the voids is negligible at the CIGSSe layer.

Effect of various encapsulants for frameless glass to glass Cu(In,Ga)(Se,S)2 photovoltaic module

Cu(In,Ga)(Se,S)2 (CIGSS) modules with a frameless glass to glass (G2G) structure were successfully fabricated by replacing the currently used ethylene vinyl acetate (EVA) with new encapsulants such as polyolefins (POE), ionomer (IO) and liquid silicon (LSI), and their characteristics including optical, mechanical, and reliability properties were investigated. Most of the solid films for encapsulation except POE exhibit similar light transmittance in the visible-infrared wavelength range, while LSI shows the highest light transmittance with a difference of more than 2% in the overall wavelength range. The G2G structure encapsulated with IO exhibits superior values for the adhesion strength at which interface failure occurs (about 7.5 MPa) compared to other encapsulants. Water vapor transmittance ratio (WVTR) values of the encapsulants were evaluated to determine their suitability as water-resistant materials in terms of the CIGSS G2G structure. The IO encapsulant had the lowest WVTR value of about 1.75 g per m2 per day. Changes of cell-to-module (CTM) conversion ratio in the CIGSS G2G structure using various encapsulants were investigated using I–V measurements. The CIGSS G2G structure encapsulated by LSI shows the best CTM conversion ratio, since the module process occurs at the lowest temperature as compared with other encapsulants, therefore the module has a smaller thermal transient effect. Finally, the long-term reliability of the CIGSS modules based on various encapsulants was also evaluated by damp heat testing.

Enhancement of the photo conversion efficiencies in Cu(In,Ga)(Se,S)2 solar cells fabricated by two-step sulfurization process

Cu(In,Ga)(Se,S)2 (CIGSS) absorber layers were fabricated by using a modified two-stage sputter and a sequential selenization/sulfurization method, and the sulfurization process is changed from one-step to two-step. The two-step sulfurization was controlled with two different H2S gas concentrations during the sulfurization treatment. This two-step process yielded remarkable improvements in the efficiency (+0.7%), open circuit voltage (+14 mV), short circuit current (+0.23 mA/cm2), and fill factor (+0.21%) of a CIGSS device with 30 × 30 cm2 in size, owing to the good passivation at the grain boundary surface, uniform material composition among the grain boundaries, and modified depth profile of Ga and S. The deterioration of the P/N junction quality was prevented by the optimized S content in the CIGSS absorber layer. The effects of the passivation quality at the grain boundary surface, the material uniformity, the compositional depth profiles, the microstructure, and the electrical characteristics were exa...

Correction to: Optimization of Controllable Factors in the Aluminum Silicon Eutectic Paste and Rear Silicon Nitride Mono-Passivation Layer of PERC Solar Cells

The original version of this article unfortunately contained a mistake. The acknowledgements section was incomplete. The correct information is given below.