Won Jun Song

Role of n-dopant based electron injection layer in n-doped organic light-emitting diodes and its simple alternative

We investigate the enhancement mechanism of the electroluminescence (EL) of alkali metal based n-doped organic light-emitting diodes (OLEDs). The dual role of the n-dopant (carrier transport and lowering of the injection barrier) induces a trade-off. When the electron transport layer (ETL) is optimally doped by the n-dopant for the highest conductivity, the amount of n-dopant at the ETL/cathode interface is insufficient to form enough chemical bonds with the cathode for efficient carrier injection. This insufficient amount of n-dopant limits the carrier injection properties. To solve this problem, we demonstrated that the addition of an electron injection layer (EIL) comprised of the n-dopant could increase its presence at the interface and, thereby, improve the carrier injection properties and, consequently, the EL efficiency. Moreover, simply using an alkali-metal alloy (rather than co-deposition) on the n-doped ETL as a cathode, instead of using the additional EIL, greatly improves the EL efficiency of...

Reflectivity-induced Variation in Implant Layer Lithography

Scaling of designs to the 45nm and future nodes presents challenges for block level lithography. Shrinking distances between devices drive aggressive resist placement tolerances, challenging the ability to control critical dimension (CD). In particular, the potential variation in shallow trench isolation oxide may result in variation of resist profile and CD, thereby affecting edge placement accuracy. Potential sources of this include wafer-to-wafer or within-wafer STI trench depth variations, and STI CMP variations that may be induced by active area pattern density fluctuations. Some other potential sources of CD fluctuation include oxide sidewall variation, and implant level overlay or CD errors modulating the proximity to the oxide sidewall. Depending on the actual variation of isolation oxide and the exposure latitude of the resist, the CD variations simply from oxide variation may consume a large portion of the CD budget. Several examples are given of variations in resist profile and CD arising from these substrate effects. The CD uniformity of a test structure was shown to decrease dramatically with the addition of a BARC to the resist stack, most likely due to the suppression of substrate reflectivity variations. Simulations performed using Panoramic Technologies software demonstrated the potential sensitivity of the factors outlined above on CD and profile errors. A comparison of simulated vs. experimental results is made for a case of intentional overlay error, showing the failure mode of the resist profile as the mask edge passes from STI to the active area. The simulations using a full physical model provided with the simulation software predict a resist foot forming over the active area, which was confirmed experimentally.

Chronic obstructive pulmonary disease severity is associated with severe pneumonia

CONTEXT: Chronic obstructive pulmonary disease (COPD) is a heterogeneous disorder, and various aspects of COPD may be associated with the severity of pneumonia in such patients. AIMS: We examined the risk factors associated with severe pneumonia in a COPD population. MATERIALS AND METHODS: We performed a retrospective observational study using a prospectively collected database of pneumonia patients who were admitted to our hospital through emergency department between 2008 and 2012. Patients with hospital-acquired pneumonia and those with an immunocompromised status were excluded. RESULTS: Of 148 pneumonia patients with COPD for whom chest computed tomography (CT) scans were available, 106 (71.6%) and 42 (28.4%) were classified as non-severe and severe pneumonia, respectively. Multivariate logistic regression analysis revealed that the severity of airflow limitation [odds ratio (OR), 2.751; 95% confidence interval (CI), 1.074-7.050; P = 0.035] and the presence of emphysema on a chest CT scan (OR, 3.366; 95% CI, 1.104-10.265; P = 0.033) were independently associated with severe pneumonia in patients with COPD. CONCLUSIONS: The severity of COPD including the airflow limitation grade and the presence of pulmonary emphysema were independently associated with the development of severe pneumonia.

Clinical significance of differentiating post‐intubation and post‐tracheostomy tracheal stenosis

Post‐intubation tracheal stenosis (PITS) and post‐tracheostomy tracheal stenosis (PTTS) are serious complications in mechanically ventilated patients. Although the aetiologies and mechanisms of PITS and PTTS are quite different, little is known about the clinical impact of differentiating one from the other.

Pulmonary function assessment in the early phase of patients with smoke inhalation injury from fire

OBJECTIVES Fire smoke contains toxic gases and numerous chemical compounds produced by incomplete combustion, and may cause injury to the airways. Increased airway reactivity, as well as a decrease in lung function, has been reported as a sequela of smoke inhalation injury. This study was undertaken to assess lung functions in the early phase of patients with smoke inhalation damage from fires. METHODS A total of 15 patients with fire smoke inhalation (fire smoke group) and 15 subjects with chronic cough but no previous history of lung disease (chronic cough group) were enrolled. For diagnosis of inhalation injury, we performed bronchoscopy, high-resolution computed tomography (HRCT), as well as arterial carboxyhemoglobin (COHb) at admission. Clinical characteristics, pulmonary function tests (PFTs) and mannitol bronchial provocation tests (BPTs) were analyzed and compared between the two groups. RESULTS In fire smoke group, initial COHb levels and the PaO2/FiO2 ratio were (14.8±18.49)% and 425.7±123.68, respectively. Of seven patients performing HRCT, 4 (57.1%) showed the CT findings compatible with lung involvement of inhalation injury. Post bronchodilator value of the percent of forced vital capacity (FVC) and forced expiratory volume in 1 second (FEV1) were (76.0±24.27)% and (79.8±27.82)%, respectively. Pre-and post- bronchodilator forced expiratory flow between 25% and 75% of the FVC (FEF25-75) and the percent predicted FEF25-75 were 2.41±1.47 vs. 2.65±1.45 L (P=0.045), and (68.7±37.29)% vs. (76.4±36.70)% (P=0.031), respectively. Two patients (13.3%) had positive bronchodilator response (BDR). In fire smoke and chronic cough group, all the subjects showed mannitol BPTs within normal limits. CONCLUSIONS Fire smoke inhalation leads to mild obstructive small airway disease pattern of pulmonary function in the early phase of patients with fire smoke damage. Further studies, however, need to be followed to identify the relationship between airway narrowing to inhaled mannitol and smoke inhalation injury.

Clinical Utility of Additional Measurement of Total Lung Capacity in Diagnosing Obstructive Lung Disease in Subjects With Restrictive Pattern of Spirometry

BACKGROUND: Total lung capacity (TLC), forced expiratory flow between 25 and 75% (FEF25-75%), peak expiratory flow (PEF), or post-bronchodilator volume response is recommended to detect obstructive abnormalities in the lung. The present study was performed to evaluate the usefulness of these pulmonary function test (PFT) parameters to diagnose obstructive lung disease in subjects with a restrictive pattern of spirometry. METHODS: A retrospective study was conducted in 64 subjects with a restrictive pattern of spirometry (normal FEV1/FVC and low FVC) out of 3,030 patients who underwent all pre- and post-bronchodilator spirometry and lung volume measurement between April 2008 and December 2010. After subjects were clinically classified into those with obstructive lung disease, restrictive lung disease, and mixed lung disease, the agreements between the clinical diagnosis and PFT classification according to TLC, FEF25-75%, PEF, and post-bronchodilator response criteria were compared. RESULTS: Of 64 subjects, 18 (28.1%) were classified with obstructive lung disease, 39 (60.9%) had restrictive lung disease, 1 (1.6%) had mixed lung disease, and 6 (9.4%) had no clinical lung disease. Among the 58 subjects with clinical lung disease, 22 (37.9%), 37 (63.8%), 33 (56.9%), and 3 (5.2%) were classified as having obstructive pattern based on TLC, FEF25-75%, PEF, and post-bronchodilator response criteria, respectively. The kappa coefficients for the agreement between the clinical classification and PFT classification using TLC, FEF25-75%, PEF, and post-bronchodilator response criteria in 58 subjects were 0.59, 0.18, 0.17, and < 0.01, respectively. CONCLUSIONS: The additional measurement of TLC is more useful than FEF25-75%, PEF, and post-bronchodilator response for diagnosis of obstructive lung disease in subjects with a restrictive pattern of spirometry, when obstructive lung disease is clinically suspected.

Clinical implications of differentiating between types of post- tracheostomy tracheal stenosis

Background Post-tracheostomy tracheal stenosis (PTTS) can be divided into four types according to stenosis mechanism and site: subglottic, stoma, cuff, and tip granuloma. However, there is little information available regarding clinical differences among types of PTTS; therefore, we evaluated the clinical differences between these types. Methods We retrospectively evaluated 99 PTTS patients who underwent interventional bronchoscopy between 2004 and 2014. Patients were divided into two groups according to pathophysiological similarities as follows: subglottic or stoma type (n=59) and cuff or tip type (n=40). Results There were no differences in baseline characteristics between groups. However, silicone stents were more frequently needed in patients with subglottic or stoma type stenosis (76%) than those with cuff or tip type stenosis (55%, P=0.031) to maintain airway patency. On the contrary, permanent tracheostomy was more frequently performed in patients with cuff or tip type stenosis (50%) than those with subglottic or stoma type stenosis (19%, P=0.002). Finally, successful removal of the tracheostomy tube without surgery and procedure- or disease-related mortality were more frequently achieved in patients with subglottic or stoma type stenosis (71%) than those with cuff or tip type stenosis (45%, P=0.012). Conclusions Although there were no significant differences in baseline characteristics between PTTS types, patients with subglottic or stoma type stenosis had more favorable outcomes than those with cuff or tip type stenosis. Therefore, it could be important to distinguish between types of PTTS when assessing prognosis.

Mycobacterium abscessus Lung Disease in a Patient with Kartagener Syndrome.

Primary ciliary dyskinesia (PCD) is characterized by the congenital impairment of mucociliary clearance. When accompanied by situs inversus, chronic sinusitis and bronchiectasis, PCD is known as Kartagener syndrome. The main consequence of impaired ciliary function is a reduced mucus clearance from the lungs, and susceptibility to chronic respiratory infections due to opportunistic pathogens, including nontuberculous mycobacteria (NTM). There has been no report of NTM lung disease combined with Kartagener syndrome in Korea. Here, we report an adult patient with Kartagener syndrome complicated with Mycobacterium abscessus lung disease. A 37-year-old female presented to our hospital with chronic cough and sputum. She was ultimately diagnosed with M. abscessus lung disease and Kartagener syndrome. M. abscessus was repeatedly isolated from sputum specimens collected from the patient, despite prolonged antibiotic treatment. The patients condition improved and negative sputum culture conversion was achieved after sequential bilateral pulmonary resection.

Current development status and issues of AMOLED toward an invaluable display

Organic Light-Emitting Device (OLED) has been attracted much interests to realize a flat panel display owing to its promising characteristics. Active matrix OLED can make it possible to make big displays with the good image qualities and create new values and concepts, such as a flexible display, transparent display, and so on. However, in spite of the big potential of the AMOLED, it is still needed to improve lifetime, efficiency and productivity for large size displays. In this paper, we present current development status and issues of the AMOLED toward an ultimate champion among flat panel displays.