A Study on the N2O Reduction Rate According to Temperature and Residence Time in the Exhaust Gas Atmosphere Emitted on Combustion of Air and Oxygen.

N2O is a hazardous greenhouse gas. It should be reduced to solve global warming problems. In this study, experiments of N2O thermal decomposition were conducted by simulating the exhaust gas atmosphere emitted during the combustion of air and pure oxygen in an actual circulating fluidized bed system and incinerator system. As a result of comparing the N2O reduction rate in N2 and CO2 atmospheres, the N2O reduction rate in the CO2 atmosphere was 20% higher than that in the N2 atmosphere. It is judged that the N2O reduction rate is high in a CO2 atmosphere (exhaust gas from pure oxygen combustion) due to complex factors such as the reverse reaction, the diffusion coefficient, and static pressure-specific heat. Therefore, pure oxygen combustion increases the reduction rate of nitrous oxide. In addition, when operated with an appropriate residence time and temperature, a reduction effect of more than 95% can be expected, and the fuel consumption rate is also expected to improve.

Progression of optic atrophy in traumatic optic neuropathy: retrograde neuronal degeneration in humans.

OBJECTIVE: We used optical coherence tomography (OCT) to document the time course of retrograde neuronal degeneration following indirect optic nerve injury. METHODS: We retrospectively studied patients diagnosed with unilateral indirect traumatic optic neuropathy (TON). Patients with total or near-total optic atrophy were included. All patients underwent complete ophthalmological examinations, including OCT imaging, within 1 day and at 1, 2, 3, 4, 6, 8, 12, 24, and 48 weeks after trauma. RESULTS: The mean thicknesses of the circumpapillary retinal nerve fiber layer (cpRNFL) and macular retinal ganglion cell-inner plexiform layer (mGCIPL) decreased significantly at 2 weeks after trauma (p = 0.027 and p = 0.043). Changes in mGCIPL thickness preceded changes in cpRNFL thickness. The rates of reduction in mGCIPL and cpRNFL thicknesses were greatest between 2 to 4 weeks and 4 to 6 weeks after trauma. The reduction in mGCIPL thickness then slowed, and stabilized at 12 weeks after trauma. The proportions of cpRNFL and mGCIPL losses at 2, 4, 6, 8, and 12 weeks compared to 24 weeks were 17.1, 33.7, 59.8, 77.9, and 87.9% and 30.0, 73.3, 76.1, 88.3, and 97.9%, respectively. CONCLUSIONS: OCT revealed optic atrophy progression 2 weeks after trauma, which was most rapid from 2 to 6 weeks, and then gradually stabilized. Loss of retinal ganglion cell bodies and dendrites seemed to precede the axonal degeneration. Observations of morphological changes in retinal layers using OCT in TON patients improve our understanding of retrograde neuronal degeneration of the central nervous system.

Effect of the Oxygen Concentration and Temperature on Thermal Decomposition of N2O in an Inert Gas.

Nitrous oxide (N2O) is one of the greenhouse gases that contribute to global warming. But, there are few methods for controlling N2O directly. It is essential to reduce N2O to solve environmental problems. In this study, we investigate the O2 concentration dependence of N2O decomposition under an argon-based gas mixture in a high-temperature thermal reactor. The gas concentrations are calculated using CHEMKIN. The results confirm that more N2O is converted to N2 or NO at lower O2 concentrations. Therefore, the conversion process is hindered by increasing the O2 concentration. We propose a modified parameter of N2O decomposition, and it is employed in the CHEMKIN calculations. With the modified parameter, the experimental results are in a similar tendency to the calculated results.

Clinical outcomes of Ahmed glaucoma valve implantation without fixation of a plate: The free plate technique.

OBJECTIVE: This study compared surgical outcomes between free plate Ahmed glaucoma valve (FPAGV) implantation without plate fixation and conventional Ahmed glaucoma valve (CAGV) implantation with plate fixation. METHODS: A retrospective, comparative case series study. Patients with refractory glaucoma who underwent FPAGV or CAGV implantation and were followed >1 year were enrolled consecutively. We reviewed medical records, including data on postoperative intraocular pressure (IOP) and postoperative complications. The success rate and early postoperative hypertensive phase were compared between groups. RESULTS: A total of 74 patients with CAGV implantations and 36 patients with FPAGV implantations were studied. The average follow-up periods were 23.3 ± 2.6 months (CAGV) and 22.8 ± 2.8 months (FPAGV; p = 0.424). The surgery time was significantly shorter in the FPAGV group than in the CAGV group (42.6 ± 4.1 vs. 47.3 ± 5.4 min; p < 0.001). Postoperative IOP at 1 week and 1 month were significantly lower in the FPAGV group than in the CAGV group (11.8 ± 3.6 and 14.0 ± 5.3 mmHg vs. 18.7 ± 5.5 and 22.2 ± 5.2 mmHg; p = 0.012 and p = 0.002, respectively). An early postoperative hypertensive phase occurred in 62 eyes, and the frequency was greater in the CAGV group (50 eyes) than the FPAGV group (12 eyes; p = 0.001). There was no significant difference in postoperative complications between the two groups (p = 0.735). The success rate was 84.2% in the FPAGV group and 80.6% in the CAGV group 24 months after surgery (p = 0.367). CONCLUSION: FPAGV implantation was associated with a shorter surgery time, without any change in the extent of IOP reduction or complication rate. This procedure may be considered a good alternative for CAGV implantation in patients with refractory glaucoma.

Using the Thickness Map from Macular Ganglion Cell Analysis to Differentiate Retinal Vein Occlusion from Glaucoma.

PURPOSE: We hypothesized that the thickness map from macular ganglion cell analysis (GCA) acquired from spectral-domain optical coherence tomography can be used to differentiate retinal vein occlusion (RVO) from glaucoma. METHODS: In this retrospective case control study, 37 patients with resolved RVO and 74 patients with primary open-angle glaucoma (POAG) were enrolled. Two independent examiners diagnosed patients with RVO or POAG based on the topographic pattern in the GCA thickness map. Inter-observer agreement for a decision between RVO and POAG was assessed using kappa statistics. Diagnostic specificity and accuracy were calculated. RESULTS: Inter-observer agreement was good, with a kappa value of 0.765 (95% confidence interval, 0.634-0.896, p < 0.001). The diagnostic specificity of RVO from POAG using the GCA thickness map was 93.2% and diagnosis accuracy was 80.4%. CONCLUSIONS: An irregular GCA thickness map represents a simple and convenient differential diagnostic clue to distinguish RVO from POAG.

Effects of Topical Prostaglandin Analog on Macular Thickness Following Cataract Surgery with Postoperative Topical Bromfenac Treatment.

PURPOSE: To evaluate changes in macular thickness in patients continuing prostaglandin analog (PGA) treatment during the perioperative period involving bromfenac treatment. METHODS: Patients with glaucoma who were using a topical PGA were randomly assigned to two groups in this randomized controlled trial: PGA continuing study group and PGA discontinued glaucoma control group. Patients without ocular diseases other than cataract were enrolled into the non-glaucomatous group. After the cataract surgery, the patients used bromfenac twice per day for 4 weeks. Optical coherence tomography was performed in all patients preoperatively and at 1 month postoperatively. Changes in macular thickness were compared among the three groups. RESULTS: There were 32 eyes in the study group, 33 eyes in the glaucoma control group, and 58 eyes in the non-glaucomatous group. We found statistically significant postoperative changes in central macular thickness in all groups (4.30 ± 8.01 µm in the PGA continuing group, 9.20 ± 13.88 µm in the PGA discontinued group, and 7.06 ± 7.02 µm in the non-glaucomatous group, all p < 0.008), but no significant difference among the three groups (p = 0.161). Cystoid macular edema occurred in only one patient in the non-glaucomatous group (p = 0.568). CONCLUSIONS: Continuous use of PGAs during the perioperative period was not significantly associated with increased macular thickness after uncomplicated cataract surgery. In the absence of other risk factors (e.g., capsular rupture, uveitis, or diabetic retinopathy), discontinuing PGAs for the prevention of macular edema after cataract surgery with postoperative bromfenac treatment is unnecessary in patients with glaucoma.

Relationship between Tube Parameters and Corneal Endothelial Cell Damage after Ahmed Glaucoma Valve Implantation: A Comparative Study.

PURPOSE: We compared the clinical factors, including anterior chamber tube parameters, in patients with and without corneal endothelial cell damage after Ahmed glaucoma valve (AGV) implantation. METHODS: In this retrospective and comparative case series, patients who underwent AGV implantation were enrolled consecutively. Serial specular microscopy was performed before and after AGV implantation. Patients were divided into two groups depending on whether there was a significant decrease in corneal endothelial cell density (ECD), which was determined by each patient's rate of ECD change (%/year), calculated using linear regression analyses. Tube parameters such as the tube-cornea distance (TCD) and tube-cornea angle (TCA) were measured with anterior segment optical coherence tomography. Clinical factors related to the rate of ECD change were evaluated with regression analyses and compared between the two groups. The tipping point at which tube parameters became significantly associated with the rate of ECD change was identified with broken stick regression analyses. RESULTS: There were 30 eyes (32.3%) with ECD damage (group 1) and 63 eyes (67.7%) without damage (group 2). The mean rate of ECD change (%/year) was -18.82 ± 22.97 and 2.14 ± 2.93 in groups 1 and 2, respectively (p < 0.001). The TCA was the only clinical factor associated with the rate of ECD change (regression coefficient, ß = 1.254, p < 0.001). The tipping point in the TCA was 26.70° (95% confidence interval, CI: 23.75-29.64°). The mean TCD (mm) was 0.98 ± 0.38 and 1.26 ± 0.39 (p = 0.002), and the mean TCA (degrees) was 28.67 ± 7.79 and 36.35 ± 5.35 (p < 0.001) in groups 1 and 2, respectively. CONCLUSIONS: A wider TCA was protectively associated with the rate of ECD change, and the TCA was significantly narrower in patients with ECD damage. When inserting a tube into the anterior chamber, surgeons should therefore try to secure a wide TCA of about 30°. In patients with a narrow TCA after AGV implantation, increased attention should be directed toward whether ECD decreases continuously.

Changes in thickness of central macula and retinal nerve fibre layer in severe hypertensive retinopathy: a 1-year longitudinal study.

OBJECTIVE: To analyse the longitudinal changes in the thickness of the central macula and retinal nerve fibre layer (RNFL) in patients with hypertensive retinopathy (HTNR) using spectral-domain optical coherence tomography (SD-OCT). METHODS: This was a prospective cohort study. We studied 18 eyes of patients with HTNR of grade IV who had been followed up for more than 1 year, and 36 normal eyes (without any relevant medical history; the control group). Antihypertensive treatment successfully normalized the blood pressure of HTNR patients. The RNFL thickness and that of the central macula of HTNR patients were measured using a Cirrus HD-OCT instrument, and compared with those of the control group. RESULTS: At 12 months of follow-up, the mean thickness of the RNFL and central macula was significantly lower in the HTNR group than in the control group (the RNFL was measured first, and then the central macular thickness (CMT): 77.4 ± 9.1 and 233.8 ± 30.8 µm versus 94.1 ± 7.8 and 256.3 ± 28.1 µm, respectively; p < 0.05). With time, the RNFL thickness and CMT became significantly less than that at the initial diagnosis (p < 0.05). CONCLUSION: Severe HTNR causes a decrease in the thickness of the RNFL and central macula over time. Therefore, the impact of retinal changes associated with systemic diseases such as hypertension should be considered in analysing the thicknesses of the RNFL and central macula in ocular disorders, including retina, glaucoma and neuro-ophthalmologic diseases.

Learning Curve for Endoscopic Endonasal Dacryocystorhinostomy.

PURPOSE: To elucidate the learning curve for endoscopic endonasal dacryocystorhinostomy (EE-DCR) based on the results of EE-DCR performed by three surgeons at three different tertiary hospitals. METHODS: A retrospective review of the medical records of 386 eyes of 337 patients who had undergone EE-DCR by three surgeons at three tertiary hospitals and who were available for a >6-month postoperative observation period was conducted. The success of a given surgery was determined based on the results of a test performed during the patient's last outpatient visit to the hospital. The learning curve was identified by dividing the patients into four groups (20, 30, 40, and 50 eyes in each respective group) and comparing their success rates. RESULTS: The overall success rate of the entire study population was 86.3%. The success rates for each of three surgeons was 83.3%, 85.6%, and 88.1%, respectively. After dividing the patients into groups of 30 eyes each, all three surgeons showed a significant increase in surgery success rates after their first group of 30 eyes (p < 0.05). The overall success rate excluding the first 30 eyes was 92.9%, and all three surgeons exhibited a significantly improved success rate of >90% (A, 94.4%; B, 90.8%; C, 95.4%). CONCLUSIONS: A surgeon should be required to perform at least 30 EE-DCR procedures to obtain stable surgical skill for this procedure.

[Efficacy of tenofovir-based rescue therapy for patients with drug-resistant chronic hepatitis B].

BACKGROUND/AIMS: Tenofovir disoproxil fumarate (TDF) plays a pivotal role in the management of drug-resistant chronic hepatitis B. However, it remains unclear whether TDF-nucleoside analogue combination therapy provides better outcomes than TDF monotherapy. This study aimed to compare the efficacy of TDF monotherapy with that of TDF-nucleoside analogue combination therapy in patients with drug-resistant chronic hepatitis B. METHODS: This retrospective cohort study included 76 patients receiving TDF-based rescue therapy for more than 12 months. Suboptimal response was defined as serum HBV-DNA level of > 60 IU/mL during prior rescue therapy. Multi-drug resistance was defined as the presence of two or more drug resistance-related mutations confirmed by mutation detection assay. The relationship between baseline characteristics and virologic response (HBV DNA < 20 IU/mL) at 12 months were evaluated using logistic regression analysis. RESULTS: Fifty-five patients (72.4%) were suboptimal responders to prior rescue therapy, and 26 (34.2%) had multi-drug resistance. Forty-two patients (55.3%) received combination therapy with nucleoside analogues. Virologic response at 12 months was not significantly different between the TDF monotherapy group and TDF-nucleoside analogue combination therapy group (p = 0.098). The serum HBV DNA level was reduced to -4.49 ± 1.67 log10 IU/mL in the TDF monotherapy group and to -3.97 ± 1.69 log10 IU/mL in the TDF-nucleoside analogue combination therapy group at 12 months (p = 0.18). In multivariate analysis, female sex (p = 0.032), low baseline HBV-DNA level (p = 0.013), and TDF monotherapy (p = 0.046) were predictive factors for virologic response at 12 months. CONCLUSIONS: TDF monotherapy showed similar efficacy to that of TDF-nucleoside analogue combination therapy in patients with drug-resistant chronic hepatitis B.

Endoscopic Removal of a Proximally Migrated Metal Stent during Balloon Sweeping after Stent Trimming.

Placement of a self-expanding metal stent (SEMS) is an effective method for palliation of a malignant biliary obstruction. However, metal stents can cause various complications, including stent migration. Distally migrated metal stents, particularly covered SEMS, can be removed successfully in most cases. Stent trimming using argon plasma coagulation may be helpful in difficult cases despite conventional methods. However, no serious complications related to the trimming or remnant stent removal method have been reported due to the limited number of cases. In particular, proximal migration of a remnant fragmented metal stent after stent trimming followed by balloon sweeping has not been reported. We report an unusual case of proximal migration of a remnant metal stent during balloon sweeping following stent trimming by argon plasma coagulation. The remnant metal stent was successfully removed with rotation technique using a basket and revised endoscopically.

Diverticular Choledochal Cyst with a Large Impacted Stone Masquerading as Mirizzi's Syndrome.

Choledochal cysts are congenital anomalies of the biliary tract manifested by cystic dilatation of the extrahepatic and intrahepatic bile ducts. Choledochal cyst is not rare in far-East Asian countries. Type II choledochal cysts account for 2% of all such cysts. They are true diverticula of the extrahepatic bile duct and communicate with the bile duct through a narrow stalk. This condition is associated with significant complications, such as ductal strictures, stone formation, cholangitis, rupture and secondary biliary cirrhosis. We describe a case of a huge impacted stone in a diverticular choledochal cyst which masqueraded as an unusual cystic duct stone causing Mirizzi's syndrome.

Long QT syndrome and torsade de pointes associated with Takotsubo cardiomyopathy.

Prolongation of QTc interval associated with Takotsubo cardiomyopathy (TC) has previously been reported in published case series. We report an unusual case of a patient who presented with TC associated with long-QT syndrome and developed cardiac arrest secondary to torsade de pointes. Since QT prolongation and bradycardia persisted after the resolution of TC, the patient received permanent pacemaker. Since then additional event did not occur. QT prolongation and bradycardia could be persistent even after recovery of TC, and permanent pacemaker insertion may be a treatment option of long QT syndrome related with TC.