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In 2017, the Korean government launched an unprecedentedly large-scaled latent tuberculosis infection (LTBI) screening project which covered more than a million individuals in congregate settings. A total of 1,047,689 participants of source population (n = 2,336,157) underwent LTBI testing from 2017 to 2018. The overall LTBI test uptake rate during this project was 44.8%. Workers in daycare centers (83.5%) and kindergartens (78.9%) showed high participation rate. A total of 1,012,206 individuals with valid results of interferon-gamma release assay (IGRA) were selected to constitute the IGRA cohort. Most of the enrolled participants in the IGRA cohort were in their working age. Approximately, three-quarters of total enrolled population were female. Investigating the LTBI prevalence, stages of LTBI care cascade, natural history of LTBI, efficacy of LTBI treatment and cost-effectiveness of LTBI screening are feasible within this IGRA cohort., Graphical Abstract

Increased awareness of adverse events following immunization (AEFI) can disrupt vaccination programs. In South Korea, a report of alleged influenza vaccine-related deaths attracted significant media attention in 2020. We retrieved the vaccination coverage and AEFI data to determine their association with media coverage. Between 2015 and 2019, the vaccination coverage rate ranged between 80.5% and 83.3%; however, the vaccination coverage rate declined significantly from 2020 to 2021 to 73.6% (p < 0.0001). During the 43rd week of 2020, following a large amount of media coverage on vaccine safety issues, the number of cases with AEFI reached 60. Between 2015 and 2020, the mortality rate ratios for influenza vaccines and non-vaccines ranged between 0.1296 (95% confidence interval (CI), 0.1262–0.1331, p < 0.0001) and 0.1608 (95% CI, 0.1572–0.1644, p < 0.0001). Vaccine safety surveillance should be continued in conjunction with investigation and transparent risk communication to maintain public trust in vaccines and vaccinations.

Background In February 2020, a coronavirus disease 2019 (COVID-19) outbreak was reported in fitness centers in Cheonan, Korea. Methods From February 24 to March 13, an epidemiological investigation was conducted on the fitness center outbreak. All those who were screened were tested for severe acute respiratory syndrome coronavirus-2 (SARS CoV-2) using real-time reverse transcriptase polymerase chain reaction. Contacts were traced and self-isolated for 14 days. We determined the epidemiological characteristics of confirmed cases of SARS-CoV-2 infection, and estimated the time-dependent reproduction number to assess the transmission dynamics of the infection. Results A total of 116 cases were confirmed, and 1,687 contacts were traced. The source cases were 8 Zumba instructors who led aerobics classes in 10 fitness centers, and had the largest average number of contacts. A total of 57 Zumba class participants, 37 of their family members, and 14 other contacts were confirmed as cases. The attack rate was 7.3%. The contacts at Zumba classes and homes had a higher attack rate than other contacts. The mean serial interval (± standard deviation) were estimated to be 5.2 (± 3.8) days. The time-dependent reproduction number was estimated to be 6.1 at the beginning of the outbreak, but it dropped to less than 1, 2 days after the epidemiological investigation was launched. Conclusion The results suggest that the COVID-19 outbreak was effectively contained with rigorous contact tracing, isolating, and testing in combination with social distancing without a lock-down., Graphical Abstract

The Korean influenza national immunization program was first established as an interim program in 1997, administering the influenza vaccine to low-income elderly adults. In 2005, the program assumed its present form of providing free influenza vaccination to adults aged ≥65 years. After turning over the influenza vaccination for elderly adults to the private sectors in 2015, the influenza vaccination coverage rate among this population increased to >80%. In addition, after the 2009 H1N1 influenza epidemic crisis, the vaccine was domestically produced. By reaching a 75% vaccination coverage rate in the target groups, it was possible to put an end to the influenza pandemic and fix the shortcomings of the system that existed at that time. The influenza vaccination program, provided free of cost, was extended to include infants aged

The Korea National Health and Nutrition Examination Survey (KNHANES) is a national surveillance system that has been assessing the health and nutritional status of Koreans since 1998. Based on the National Health Promotion Act, the surveys have been conducted by the Korea Centers for Disease Control and Prevention (KCDC). This nationally representative cross-sectional survey includes approximately 10 000 individuals each year as a survey sample and collects information on socioeconomic status, health-related behaviours, quality of life, healthcare utilization, anthropometric measures, biochemical and clinical profiles for non-communicable diseases and dietary intakes with three component surveys: health interview, health examination and nutrition survey. The health interview and health examination are conducted by trained staff members, including physicians, medical technicians and health interviewers, at a mobile examination centre, and dieticians’ visits to the homes of the study participants are followed up. KNHANES provides statistics for health-related policies in Korea, which also serve as the research infrastructure for studies on risk factors and diseases by supporting over 500 publications. KCDC has also supported researchers in Korea by providing annual workshops for data users. KCDC has published the Korea Health Statistics each year, and microdata are publicly available through the KNHANES website (http://knhanes.cdc.go.kr).

The dynamic properties of photoinduced alignment and surface relief grating (SRG) formation asafunction ofexcitationwavelength(lex ¼454,488,514,532,568,and 647nm)areexamined using five azobenzene-derivative polymers, whose absorption spectra are tuned by substituting different electron-withdrawing groups (CF3, CN, CNCl, NO2, (CN)2). The dynamics sensitively depend on lex. The fastest rate of photoinduced alignment is observed when lex is between lmax of

Photo-tunable photonic crystals were prepared from three dimensional (3D) colloidal crystal templates using a photoresponsive azopolymer. For the preparation of azopolymer infiltrated photonic crystals, silica colloidal crystals were fabricated by gravity sedimentation, a self-assembly technique. The interstitial voids between colloidal particles were filled with azopolymer and azopolymer inverse opals were produced by treatment with aqueous hydrofluoric acid. These photonic crystals exhibited stop bands in their transmission spectra measured in the normal incidence to the (111) plane of face centered cubic (fcc). The photonic bandgap of the azopolymer infiltrated opal and inverse opal could be controlled by the refractive index change due to the photoinduced orientation of azobenzene chromophores. When the azopolymer photonic crystals were irradiated with linearly polarized light, their bandgap positions were shifted to shorter wavelength regions with increasing irradiation time. This behavior experimentally produced a photoinduced orientation of the azobenzene groups in parallel with the incidence of the excitation light. Through such an out-of-plane orientation of azo chromophores, parallel to the [111] fcc crystallographic axis, the effective refractive index of the photonic crystal medium was decreased. Therefore, a blue-shift in bandgap positions was consequently induced with 20-40 nm tuning ranges. The out-of-plane orientation was confirmed by angular resolved absorption spectral measurements.

We report a novel compact all-fiber technique to control the beam propagation and beam pattern in free space. By coating an azo-polymer thin film layer on the optical fiber end surface, various surface relief grating (SRG) structures were inscribed over the film using a single step direct exposure of interference patterns to form a novel organic/inorganic composite fiber optics beam shape converter. The linear and concentric SRGs were experimental characterized along with numerical simulations.

For use in hybrid solar cells consisting of TiO2 and poly[2-methoxy, 5-(2 � -ethyl-hexyloxy)-1,4-phenylenevinylene] (MEH-PPV), a TiO2 nanostructure which has periodic hexagonal hole arrays was fabricated using surface relief gratings on azobenzene-functionalized polymer films as a template in the sol–gel reaction of a Ti-precusor. The ordered bulk heterojunction solar cells, prepared with the TiO2 nanostructure and MEH-PPV, have a higher power conversion efficiency of 0.21% compared to bilayer and random bulk heterojunction solar cells fabricated with thin-dense TiO2 films and randomly networked TiO2 nanoparticles, respectively, under one sun with air mass 1.5 global illumination. © 2007 Elsevier B.V. All rights reserved.

Azobenzene functionalized polyisocyanate and cyclic trimer with the same chemical composition were synthesized via anionic living polymerization. Thin films were prepared through a simple spin coating process, especially even with low molecular weight of trimer, it was possible to form optically transparent films. Photoinduced phenomena of dichroism, birefringence and holographic surface relief grating formation were investigated in relation to their molecular structures by irradiation of Ar ion laser beam. Compared to the azo polymer, generally the cyclic trimer showed faster growth rate of birefringence and increased diffraction efficiency during holographic surface grating formation, due to the absence of long polymer backbones and the lack of their complicated entanglements, but the final saturated values were smaller. The efficient surface relief grating formation was confirmed from the AFM images, which showed regularly defined sinusoidal relief structures.

We report on the synthesis of a spiro-fluorene derivative with bulky tert-butyl-substituted triphenylamine structure. The compound was synthesized in an attempt to enhance both hole injection and physical properties. A series of copolymers of the compound and a spiro-anthracenefluorene structure were synthesized, and their physical, optical, and electrochemical characteristics were investigated. The polymers showed good thermal stability with decomposition temperatures in excess of 389 °C and high glass transition temperatures in the range of 112−207 °C. The emission characteristics of the polymers were similar to that of dialkyl polyfluorenes. Cyclic voltametry studies revealed that the energy level of polymers can be tuned by adjusting the spiro-triphenylamine content with a tuning range of about 0.5 eV. Organic light-emitting diodes were fabricated using the polymers. All of the devices showed an emission in the deep blue region, and the copolymers showed improved hole injecting/transporting characteri...

Well-ordered TiO2 nanostructures such as 1-dimensional nanowire arrays, 2-dimensional square and hexagonal hole arrays, and 3-dimensional wire junction arrays were fabricated by a simple, controllable, economical, and reproducible method using surface relief gratings on azobenzene-functionalized polymer films as a template in the sol–gel reaction of a Ti precusor. In addition, as an application of TiO2 nanostructure, transparent electrodes were patterned by selective dry etching with the TiO2 nanowire array etch mask. Scanning electron microscope and atomic force microscope images confirmed the successful formation of a variety of well-ordered TiO2 nanostructures and nanopatterning of transparent electrodes.

Synthesis and characterization of new naphthalene-based PFCB aryl ether polymeric isomers with 1,5-, 1,6-, 2,6-, and 2,7-linkages were described. Monomers of perfluorocyclobutane (PFCB) poly- (aryl ether)s, 1,5-, 1,6-, 2,6-, and 2,7-bis(trifluorovinyloxy)naphthalene, were synthesized from dihydroxy- naphthalenes in two steps and polymerized by 2﷿ + 2﷿ step-growth cyclopolymerization. The naphthalene- based PFCB polymers (PFNs) had a relatively high Tg in the range 106-144 °C and excellent thermal stability at temperatures up to 400 °C. Among PFN polymeric isomers, Tg of the 1,5-linked PFCB polymer (1,5-PFN) was 30-40 °C higher than those of the other naphthalene isomers due to its high steric hindrance around the backbone. The refractive index and birefringence of the PFN polymers in the form of spin-coated films were determined. The PFN isomeric polymers showed tunability in refractive index and the birefringence of the order of 1,5 < 1,6 < 2,6 < 2,7-PFN and 1,5 < 1,6 < 2,7 < 2,6-PFN, respectively. PFN isomers had low birefringences below 0.002 except 2,6-PFN. The lowest value in birefringence was 0.0008 of 1,5-PFN due to its highly kinked structure. Plastic optical fibers of homopolymers, 1,5- and 2,7-PFN, and copolymers, 2,7-co-1,5-PFN and 2,7-PFN-co-6F-PF, were prepared, and optical losses and windows of them were observed. The attenuation loss of PFN polymers was about 0.17-0.27 dB/cm at the wavelength of near-IR optical sources. 1,5-PFN had a lower optical loss than 2,7-PFN. The optical loss of the 2,7-co-1,5-PFN copolymer was effectively reduced compared with that of 2,7-PFN. The lowest optical loss polymer for PFCB POF was 2,7-PFN-co-6F-PF of 0.07 dB/cm at the wavelength of the optical loss window and 0.17 dB/cm at 1300 nm.

Using a cantilever type nanoprobe having a 100㎚m aperture at the apex of the pyramidal tip of a near-field scanning optical microscope (NSOM), nanopatterning of polymer films are conducted. Two different types of polymer, namely a positive photoresist (DPR-i5500) and an azopolymer (Poly disperse orange-3), spincoated on a silicon wafer are used as the substrate. A He-Cd laser with a wavelength of 442㎚ is employed as the illumination source. The optical near-field produced at the tip of the nanoprobe induces a photochemical reaction on the irradiated region, leading to the fabrication of nanostructures below the diffraction limit of the laser light. By controlling the process parameters properly, nanopatterns as small as 100㎚ are produced on both the photoresist and azopolymer samples. The shape and size variations of the nanopatterns are examined with respect to the key process parameters such as laser beam power, irradiation time or scanning speed of the probe, operation modes of the NSOM (DC and AC modes), etc. The characteristic features during the fabrication of ordered structures such as dot or line arrays using NSOM lithography are investigated. Not only the direct writing of nano array structures on the polymer films but also the fabrication of NSOM-written patterns on the silicon substrate were investigated by introducing a passivation layer over the silicon surface. Possible application of thereby developed NSOM lithography technology to the fabrication of data storage is discussed.

An azobenzene based perfluorocyclobutane (PFCB) aryl ether polymer, poly(4-(phenylazo)triphenylamine-1,2-hexafluorocyclobutyl ether), was synthesized by using a palladium catalyzed amination reaction and the 2 þ 2 cyclodimerization of 4-((trifluorovinyl)oxy)bromobenzene. This polymer was designed and synthesized to permit azo chromophores to be incorporated, thus introducing photoinduced dynamic behavior into the PFCB containing polymer structure. The polymer exhibited a Tg of about 122 8C, and the maximum absorption of the azo chromophores was 407 nm in the film state. A thin film was prepared through a spin coating process, and the rapid growth of diffraction efficiency was then achieved by irradiation with an interference beam. The efficient formation of holographic surface relief gratings was also verified from AFM images, which show regularly defined and aligned grating structures.

The dynamic properties of photoinduced molecular alignment and holographic inscription of surface relief gratings (SRG) were investigated depending on absorption wavelength of ππ* and nπ* transition in donor–acceptor type of azopolymers, which contain different electron-withdrawing substituents [CF3, CN, CNCl, NO2, (CN)2] on the azobenzene. As the cis–nπ* absorption band approaches the excitation wavelength (488 nm), the photoinduced molecular alignment rapidly occurs. The rate of SRG formation was proportional to the rate of the photoinduced molecular alignment when the ππ* absorption wavelength of the trans is higher than 440 nm.

We report the fabrication and characteristics of surface relief grating on the end surface of silica optical fiber with a diameter of 125 μm. One- and two-dimensional gratings were inscribed on the fiber surface covered with azo polymer thin-film layer using interferometric methods. Diffraction beam patterns of the zeroth and the first order due to surface relief gratings were observed using a 635 nm laser, and the relation between the measured diffraction beam pattern and the grating period was also investigated.

The aim of the study was to evaluate the prevalence of restrictive ventilatory defect and to determine the risk factors in subjects with spirometrically-defined restrictive ventilatory defect. We used the population-based, fourth-2, 3 (2008, 2009) and fifth (2010-2012) Korea National Health and Nutrition Examination Survey (KNHANES) to analyze 15,073 subjects, aged ≥40 yr who underwent spirometry. Chest radiographs were also analyzed to identify restrictive lung disease. Spirometrically-defined restrictive ventilatory defect (FEV1/FVC≥70% and FVC

We report a novel all-fiber, maskless lithograpic technology to form various concentric grating patterns for micro zone plate on azo polymer film. The proposed technology is based on the interference pattern out of the cleaved end of a coreless silica fiber (CSF)-single mode fiber (SMF) composite. The light guided along SMF expands into the CSF segment to generate various circular interference patterns depending on the length of CSF. Interference patterns are experimentally observed when the CSF length is over a certain length and the finer spacing between the concentric rings are obtained for a longer CSF. By using beam propagation method (BPM) package, we could further investigated the concentric interference patterns in terms of intensity distribution and fringe spacing as a function of CSF length. These intereference patterns are directly projected over azo polymer film and their intensity distrubution formed surface relief grating (SRG) patterns. Compared to photoresist films azo polymer layers produce surface relief grating (SRG), where the actual mass of layer is modulated rather than refractive index. The geometric parameters of the CSF length as well as diameter and the spacing between the cleaved end of a CSF and azo polymer film, were found to play a major role to generate various concentric structures. With the demonstration of the circular SRG patterns, we confirmed that the proposed technique do have an ample potential to fabricate micro fresnel zone plate, that could find applications in lens arrays for optical beam formings as well as compact photonic devices.

We report on a new polyfluorene derivative containing a spiroanthracenefluorene unit with a remote C-10 position that provides facile substitution of alkyl groups. An ethylhexyl group was introduced into the spiroanthracenefluorene unit and the ethylhexyl-substituted spiroanthracenefluorene was polymerized via an Ni(0)-mediated polymerization. The polymer showed a high spectral stability with respect to heat treatment, UV irradiation, and high current passage. A light-emitting device based on this polymer showed an emission in a deep blue region with CIE color coordinates of x = 0.17 and y = 0.12.

A novel, high Tg azobenzene-based amorphous molecular material, spiro-ADA, was designed and synthesized via a palladium catalyzed amination reaction. The introduction of bulky spiro linked bifluorene with the non-planar structure of triphenylamine of spiro-ADA prevented crystallization of the molecules and led to good amorphous film formation and thermal stability with a high glass transition temperature of 147 °C. Photoinduced behavior such as optically induced birefringence, diffraction efficiency, and surface relief gratings (SRGs) were investigated in relation to their unique molecular structures. Because of the high concentration of azobenzene groups and a low molecular mass, the films showed a very rapid response to linearly polarized light, a high diffraction efficiency of 38.7%, and a large modulation depth of around 320 nm. In addition, the thermal stability of SRGs inscribed on the spiro-ADA film was measured and found to be very stable below Tg despite its low molar mass and the absence of any chain entanglement.