[Show abstract][Hide abstract] ABSTRACT: CoSb3-based skutterudite compounds are candidate materials for thermoelectric power generation in the mid-temperature range (600-900 K) because their thermoelectric properties can be enhanced by doping and filling. The joining property of thermoelectric module electrodes containing thermoelectric materials is of great importance because it can dominate the efficiency of the thermoelectric module. This study examined the properties of CoSb/Al/Ti/CuMo joined by the spark plasma sintering technique. Titanium thin foil was used to prevent the diffusion of copper into CoSb3 and Aluminum thin foil was used to improve the adhesion between CoSb3 and Ti. The insertion of an Aluminum interlayer between the Ti and CoSb3 was effective for joining CoSb3 to Ti by forming an intermediate layer at the Al-CoSb3 boundary without any micro cracks. Specifically, the adhesion strength of the Ti/Al/ CoSb3 joining interface showed a remarkable improvement compared with our previous results, without deterioration of electrical property in the interface.
Journal of the Korean Ceramic Society 11/2014; 51(6):549-553. DOI:10.4191/kcers.2014.51.6.549 · 0.27 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Background
In this study, we assessed the 50% effective concentration (EC50) of sevoflurane for reducing a rocuronium-induced reaction, based on the Dixon's up-and-down method. We also assessed the 50 and 95% effective end-tidal concentration of sevoflurane (ETsev), based on the probit regression curve of the probability of nonwithdrawal reaction.
We conducted a prospective, double-blind study in 23 males and 24 females. After using 2.5% thiopental sodium (4 mg/kg), anesthesia was induced in the patients. The patients then inhaled sevoflurane with 5 vol% in 6 L/min of oxygen. When the target ETsev was achieved, a nurse injected the intubating dose of rocuronium (0.6 mg/kg) for 5-10 s under the free flow of intravenous fluid. After the nurse evaluated the response, the nurse recorded the maximum heart rate during 30 s and the mean arterial pressure after rocuronium injection.
Based on Dixon's up-and-down method, the EC50 of sevoflurane was 2.5 ± 0.5 vol% in males and 2.5 ± 0.3 vol% in females. The probit regression curve of the probability of nonwithdrawal reaction showed that in males the 50% effective ETsev was 2.4 vol% (95% confidence interval [CI], 1.5-3.1 vol%) and the 95% effective ETsev was 3.5 vol% (95% CI, 2.9-11.0 vol%); in females, the 50% effective ETsev was 2.4 vol% (95% CI, 2.1-2.7 vol%) and the 95% effective ETsev was 3.0 vol% (95% CI, 2.7-4.5 vol%).
The inhalation of sevoflurane during the induction period may provide a simple and reliable means of reducing rocuronium-induced reactions without adverse hemodynamic changes. There was no significant difference between males and females.
Korean journal of anesthesiology 06/2014; 66(6):439-43. DOI:10.4097/kjae.2014.66.6.439
[Show abstract][Hide abstract] ABSTRACT: ZnO with different morphologies can be used various application depending on their shapes. Different morphologies of ZnO structures were synthesized by a catalysis-free thermal evaporation process. Their morphologies were dependent on the distance from the source to substrate on the same processing condition; in the result were products morphologies of the hollow, cage and star. Their shapes and crystalinity were evaluated by SEM and XRD, respectively. This work demonstrates what kind of growth factors would be involved in the final structure morphologies.
[Show abstract][Hide abstract] ABSTRACT: In this paper, we investigated characteristics of etching induced surface morphology variation by wet etching of GaN epilayer were grown on sapphire (0001) substrate by hydride vapor phase epitaxy (HVPE). As a results of scanning electron microscope (SEM) observation, three types of hexagonal etch pits (Edge, Screw, Mixed) were formed by the GaN epilayer thickness variations. A lot of etch pits, attributed to screw and mixed type TD, were observed at thinner epilayer, leading to high etch pit density. On the other hand, the thickness of GaN epilayer increased with the number of etch pits corresponding to edge and mixed dislocations, which are the majority of TDs are observed.
[Show abstract][Hide abstract] ABSTRACT: The relatively recently developed I-gel (Intersurgical Ltd., Workingham, England) is a supraglottic airway device designed for single-use that, unlike conventional LMAs, does not require an inflatable cuff. In addition, the I-gel, much like the Proseal LMA (PLMA), has a gastric drainage tube associated with an upper tube for decompression of the stomach, thereby avoiding acid reflux and decreasing the risk of pulmonary absorption. The purpose of this study was to compare PLMA and I-gel devices in patients undergoing gynecological laparoscopy based on sealing pressure before and during pneumoperitoneum, insertion time, and gas exchange.
Following Institutional Review Board approval and written informed consent, 30 adult patients were randomly allocated to one of two groups (the PLMA or I-gel group). In each case, insertion time and number of attempts were recorded. After successful insertion, airway leak pressure was measured.
Successful insertion and mechanical ventilation with both supraglottic airway devices was achieved on the first attempt in all 30 patients, and there were no significant differences with respect to insertion time. Likewise, leak pressure did not vary significantly either between or within groups after CO(2) insufflation. In addition, differences between leak volume and leak fraction between groups were not significant.
The results of our study indicate that the I-gel is a reasonable alternative to the PLMA for controlled ventilation during laparoscopic gynecologic surgery.
Korean journal of anesthesiology 12/2012; 63(6):510-4. DOI:10.4097/kjae.2012.63.6.510
[Show abstract][Hide abstract] ABSTRACT: Although acute tolerance to opioids, especially to remifentanil, has been demonstrated consistently in animal studies, the results of clinical trials in humans are controversial. The aim of this study was to determine whether intraoperative infusions of remifentanil used as an adjuvant in general anesthesia result in acute tolerance, an event manifested by increased postoperative pain and a higher opioid requirement than usual.
Sixty patients who underwent surgery under general anesthesia for spinal fusion were randomly assigned to receive sevoflurane-nitrous oxide-oxygen (group SO, n = 20), sevoflurane-remifentanil-nitrous oxide-oxygen (group SR, n = 20), or propofol-remifentanil-oxygen (group PR, n = 20) in a double-blinded manner. All patients within 1 hour after induction received PCA (fentanyl 0.4 µg/kg/ml and ondansetron 16 mg) administered intravenously at a basal infusion rate of 1 ml/h, after being intravenously injected with a loading dose of fentanyl (1 µg/kg). Data for fentanyl requirement, verbal Numerical Rating Scale (NRS) pain score at rest, and presence of nausea or vomiting were collected at 1, 24, and 48 hours after surgery.
We did not find any significant difference in postoperative PCA fentanyl requirements, NRS or side effects among the groups.
Remifentanil as an adjuvant to sevoflurane or propofol in general anesthesia for adults having surgery for spinal fusion does not appear to cause acute opioid tolerance or hyperalgesia in patients. However, further studies are needed to elucidate whether sevoflurane and propofol exert a clinically significant effect on opioid-induced tolerance or hyperalgesia and whether this effect is related to the age of the patient, the dose and duration of remifentanil given and the intensity of pain experienced postoperatively.
Korean journal of anesthesiology 08/2012; 63(2):103-7. DOI:10.4097/kjae.2012.63.2.103
[Show abstract][Hide abstract] ABSTRACT: This study was designed to compare the outcomes of two different surgical techniques: conventional transperitoneal laparoscopic varicocele ligation (CTL-VL), and laparoendoscopic single-site varicocele ligation (LESS-VL), using transumbilical home-made single port device.
Our sample included 82 male patients with 92 clinically palpable varicoceles who underwent varicocelectomy. The patients were randomly allocated to one of two groups according to varicocele ligation technique. Early postoperative complications, hospital stay, time to return to work, degree of satisfaction, and semen parameters were assessed. A visual analogue scale (VAS) pain score that ranged from 0 to 10 and analgesia requirements during the postoperative course were used to evaluate postoperative pain.
The operating room time and hospital stay of the two study groups were comparable, but time to return to normal activity was significantly shorter in the LESS group compared with the CTL group (P = 0.025). Both VAS and the postoperative use of analgesics were significantly lower during postoperative days 2 (P = 0.005) and 3 (P = 0.047) in patients who underwent LESS-VL compared with patients who underwent CTL-VL. Significant improvements in sperm count, motility, and morphology were observed in both groups (P < 0.001; at each of the variables in both groups), but the proportion of patients who showed improvement was not significantly different between the two groups.
This relatively small-scale study suggests that LESS-VL is a safe and effective alternative to CTL-VL that provides surgeons with a minimally invasive surgical option and the ability to hide the surgical incision within the umbilicus.
[Show abstract][Hide abstract] ABSTRACT: A deletion 8p syndrome is a relatively uncommon congenital disease characterized by mental retardation associated with multiple malformation that make anesthetic management a challenge. Anesthetic management of a patient with deletion 8p syndrome may pose a serious problem mainly from difficult tracheal intubation, aspiration complication and cardiac malformation. We experienced a case of 10 year-old boy with a deletion 8p syndrome who underwent appendectomy under the general anesthesia. Intubation was performed by video glidescope after unsuccessful attempt with Macintosh laryngoscope. A high arched palate, short neck, poor patient cooperation due to mental retardation and occasional autistic behaviour made airway management difficult. This case should alert anesthesiologists to the greater difficulties of managing patients with deletion 8p syndrome.
Korean journal of anesthesiology 10/2011; 61(4):332-5. DOI:10.4097/kjae.2011.61.4.332
[Show abstract][Hide abstract] ABSTRACT: To determine the most suitable effect-site concentration of remifentanil during lightwand intubation when administered with a target-controlled infusion (TCI) of propofol at 4.0 μg/mL without neuromuscular blockade.
Prospective study using a modified Dixon's up-and-down method.
Operating room of an academic hospital.
28 ASA physical status 1 and 2 patients, aged 18-65 years, scheduled for minor elective surgery.
Anesthesia was induced by TCI propofol effect-site concentration to 4.0 μg/mL, and the dose of remifentanil given to each patient was determined by the response of the previously tested patient using 0.2 ng/mL as a step size. The first patient was tested at a target effect-site concentration of 4.0 ng/mL of remifentanil. If intubation was successful, the remifentanil dose was decreased by 0.2 ng/mL; if it failed, the remifentanil dose was increased by 0.2 ng/mL. Successful intubation was defined as excellent or good intubating conditions.
The remifentanil effect-site concentration was measured. The optimal effect-site concentration of remifentanil for lightwand tracheal intubation during propofol induction using 2% propofol target effect-site concentration to 4 μg/mL was 2.16 ± 0.19 ng/mL. From probit analysis, the effect-site concentration of remifentanil required for successful lightwand intubation in 50% (EC50) and 95% (EC95) of adults was 2.11 ng/mL (95% CI 1.16-2.37 ng/mL) and 2.44 ng/mL (95% CI 2.20-3.79 ng/mL), respectively.
A remifentanil effect-site concentration of 2.16 ± 0.19 ng/mL given before a propofol effect-site concentration of 4 μg/mL allowed lightwand intubation without muscle relaxant.
[Show abstract][Hide abstract] ABSTRACT: The Glidescope® videolaryngoscope is a new device for tracheal intubation that provides an improved view of the larynx. This study was performed to compare the Glidescope with the McGrath videolaryngoscope in terms of time to intubation (TTI) and number of attempts.
Patients were randomly allocated to one of two groups, Glidescope or McGrath group, by using computer-generated numbers. Tracheal intubation was attempted by an anesthesiologist with extensive experience using these two devices. The operator recorded ease of visualization of glottic structures based on the classification described by Cormack and Lehane. Number of failures, number of attempts and their duration, total intubation time, and events during the whole procedure were recorded. The duration of one attempt was defined as the time elapsed between picking up the endotracheal tube and verification of tracheal intubation with visualization of three expiratory carbon dioxide waveforms. TTI was defined as the sum of the duration of all intubation attempts (as many as three), excluding preoxygenation procedures.
TTI was significantly shorter for the Glidescope® compared to the McGrath® laryngoscope (40.5 vs. 53.3 s, respectively, P < 0.05). However, glottic views obtained at intubation were similar between the two groups. Number of intubation attempts was not significantly different between the two groups (1.03 ± 0.19 vs 1.10 ± 0.32, respectively) (mean ± SD).
Study results demonstrated that the Glidescope reduced total intubation time in comparison with the McGrath, in terms of TTI in patients with normal airways.
Korean journal of anesthesiology 07/2011; 61(1):19-23. DOI:10.4097/kjae.2011.61.1.19
[Show abstract][Hide abstract] ABSTRACT: The greater occipital nerve (GON) block has been frequently used for different types of headache, but performed with rough estimates of anatomic landmarks. Our study presents the values of the anatomic parameters and estimates the effectiveness of the ultrasound-guided GON blockade.
The GON was detected using ultrasound technique and distance from external occipital protuberance (EOP) to GON, from GON to occipital artery and depth from skin to GON was measured in volunteers. Patients with occipital headache were divided into two groups (ultrasound-guided block: group S, conventional blind block: group B) and GON block was performed. The same parameters were measured on group S and VAS scores were assessed at pretreatment, 1 week and 4 weeks after treatment on both groups.
The GON had distance of 23.1 ± 3.4 mm (right) and 20.5 ± 2.8 mm (left) from EOP to GON. Its depth below the skin was 6.8 ± 1.5 mm (right) and 7.0 ± 1.3 mm (left). The distance from GON to occipital artery was 1.5 ± 0.6 mm (right) and 1.2 ± 0.6 mm (left) in volunteers. Initial VAS score of group S and group B patients were 6.4 ± 0.2 and 6.5 ± 0.2. VAS score of 4 weeks after injection were 2.3 ± 0.2 on group S and 3.8 ± 0.3 on group B (P = 0.0003).
The parameters measured in this study should be useful for GON block and ultrasound-guided blockade is likely to be a more effective technique than blind blockade in occipital headache treatment.
Korean journal of anesthesiology 07/2011; 61(1):50-4. DOI:10.4097/kjae.2011.61.1.50
[Show abstract][Hide abstract] ABSTRACT: We report the thermoelectric properties of spark plasma-sintered In4Se3-In4Te3 materials. For comparison, pure In4Se3 and In4Se3 (80 wt.%)/In4Te3 (20 wt.%) mixture samples were prepared. In4Se3 and In4Te3 powders were synthesized by a conventional melting process in evacuated quartz ampoules, and a spark plasma method was used for the sintering of the pure In4Se3 and mixture samples. Thermoelectric and structural characterizations were carried out, and the mixing effect of In4Se3 and In4Te3 on the thermoelectric properties was investigated.
[Show abstract][Hide abstract] ABSTRACT: Boron carbide (B4C) is currently used in lightweight armors and high temperature materials, because it has high meting point, good hardness, low specific gravity and good mechanical properties. The sintering of boron carbide, however, is restricted by its high covalent bonding and B2O3 coatings on B4C particles surface which can cause a microstructural coarsening during sintering. Therefore, it is necessary to remove B2O3 film of By4C particles surface to restrict microstructural coarsening and densification of B4C. B4C ceramics were fabricated by a hot-press sintering and its sintering behavior, microstructure and mechanical properties were evaluated. The relative density of B4C ceramics were obtained by a hot-press sintering reached as high as 99% without any sintering additives. The mechanical properties of B4C ceramics was improved by a methanol washing which can remove B2O3 phase from a B4C powder surface. This improvement is resulted from the formation of homogeneous microstructure because the grain coarsening was suppressed by the elimination of B2O3 phase. Particularly, the mechanical properties of the sintered samples using a methanol washed powder improved compared with the samples using an as-received commercial powder.
[Show abstract][Hide abstract] ABSTRACT: Reexpansion pulmonary edema (RPE) is a rare but sometimes fatal complication of the treatment of lung collapse secondary to pneumothorax, pleural effusion, or atelectasis. We experienced a case of RPE that developed following decortication. A 46 year-old female had a decortication for pyothorax under one-lung anesthesia. There was no event during the operation and results of arterial blood gas analysis were within normal limits. After the operation, tracheal extubation was performed and 100% oxygen saturation on a pulse oximeter (SpO2) was maintained with 100% O2, (8 L/min) via mask ventilation with self-respiration. The patient, with 50% Venturi mask, was transported to the intensive care unit (ICU). On arrival at the ICU, a SpO2 of 80% was detected and arterial blood gas analysis revealed hypoxemia with acute hypercapnic respiratory acidosis. Fortunately, reexpansion pulmonary edema was detected early and intensive treatment was performed using mechanical ventilation with positive end-expiratory pressure. Tracheal extubation was performed after 1 day of mechanical ventilation. The reexpansion pulmonary edema was successfully treated and the patient recovered without any complications.
[Show abstract][Hide abstract] ABSTRACT: We report microstructures and thermoelectric properties of In4Se3 thermoelectric materials. In4Se3 powder was synthesized by conventional melting process in evacuated quartz ampoules and sintering of In4Se3 was performed
by spark plasma method at various sintering temperature. The microstructure and density of the sintered body of In4Se3 were strongly dependent on the sintering temperature. Thermoelectric properties, such as electrical conductivity, Seebeck
coefficient and thermal conductivity, were also characterized and the effects of the sintering condition on the thermoelectric
properties were investigated.
[Show abstract][Hide abstract] ABSTRACT: Patients with chronic aortic regurgitation have a hemodynamically fragile equilibrium; increased afterload during infrarenal aortic cross-clamping and acute decompensation. The tolerance of patients with severe coronary artery disease to the stress of infrarenal aortic cross-clamping differs from patients without overt coronary artery disease. Therefore, careful anesthetic management is needed during infrarenal aortic cross-clamping in patients with aortic regurgitation and coronary artery disease. We describe the anesthetic management of a man with an infrarenal aortic aneurysm that underwent cardiac arrest after aortic-cross clamping for aortoiliac bypass surgery.
[Show abstract][Hide abstract] ABSTRACT: The use of remifentanil before propofol administration facilitates the insertion of the Laryngeal Mask Airway. We designed the present study to determine whether remifentanil would also create more suitable conditions for providing Cobra Perilaryngeal airway (CobraPLA) insertion when administered with propofol.
Both remifentanil and propofol were given as effect-site target-controlled infusions. There were four groups of 25 patients each. The propofol effect-site concentration was set at 6 microg/mL in all groups. Group R1 received a target effect-site remifentanil concentration of 1 ng/mL, Group R2 received remifentanil at 2 ng/mL, Group R3 received remifentanil at 3 ng/mL, and Group R4 received remifentanil at 4 ng/mL before the induction of anesthesia with propofol. The ease of insertion of CobraPLA was graded by the following 3-point scale: Grade 1, excellent, no response to CobraPLA insertion; Grade 2, acceptable, gagging or swallowing with insertion of CobraPLA; Grade 3, poor, unable to open mouth or biting upon insertion of CobraPLA.
The most patients ranked as excellent for the first CobraPLA insertion (Grade 1) were found in Group R4, which was significantly higher than Groups R1 and R2 (P < 0.01), whereas no significant difference was found when compared with Group R3. The duration of apnea showed a significant dose-related increase (P < 0.01), especially between Group R2 (median 2.95 min) and R3 (median 7.9 min), but there was no significant difference between Groups R3 and R4. The incidence of hypotension in Group R4 within 1 min after insertion of CobraPLA was significantly more than for Groups R1 and R2 (P < 0.01). No significant differences could be found between the incidence of hypotension between Group R3 and the other groups. The incidence of hypertension at 1 min postinsertion was significantly more common in Groups R1 and R2 than Groups R3 and R4 (P < 0.01).
An effect-site concentration of remifentanil of 2 ng/mL provides excellent conditions for insertion of the CobraPLA on the first attempt with minimal hemodynamic perturbations and a shorter duration of apnea.
Anesthesia and analgesia 05/2009; 108(5):1505-9. DOI:10.1213/ane.0b013e31819e0248 · 3.47 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We hypothesized that pressure control ventilation allows a more even distribution in the lung and better maintenance of the mean airway pressure than is achieved with volume control ventilation. We try to compare the effect of pressure control ventilation (PC) with that of volume control ventilation without an end-inspiratory pause (VC) during one-lung ventilation (OLV) in an anesthetized, paralyzed patient for performing thoracopic bullectomy of the lung.
Korean journal of anesthesiology 01/2009; 56(5). DOI:10.4097/kjae.2009.56.5.492