Risk compensation after COVID-19 vaccination: Evidence from vaccine rollout by exact birth date in South Korea.

We utilize the phased rollout of COVID-19 vaccines by exact birth date in South Korea as a natural experiment for testing risk compensation. People may resume face-to-face social activities following vaccination because they perceive lower risk of infection. Applying a regression discontinuity design based on birth date cutoffs for vaccine eligibility, we find no evidence of risk-compensating behaviors, as measured by large, high-frequency data from credit card and airline companies as well as survey data. We find some evidence of self-selection into vaccine take-up based on perception toward vaccine effectiveness and side effects, but the treatment effects do not differ between compliers and never-takers.

Erythrobacter oryzae sp. nov., isolated from rice paddy soil.

Two novel bacterial strains, designated as COR-2T and CR-8, were isolated from paddy soil. These isolates were aerobic, Gram-stain-negative, non-spore-forming, non-motile, rod-shaped, and formed orange-coloured colonies. Phylogenetic analysis based on 16S rRNA gene sequences showed that two strains formed a clear phylogenetic lineage with the genus Erythrobacter. Strains COR-2T and CR-8 showed 99.9 % 16S rRNA gene sequence similarity. Both strains had the highest 16S rRNA gene similarity of 99.1-99.7 % to Erythrobacter colymbi TPW-24T, Erythrobacter donghaensis SW-132T and Erythrobacter tepidarius DSM 10594T, respectively. The genome of strain COR-2T comprised 3 559 918 bp and the genomic DNA G + C content was 67.7 mol%. The average nucleotide identity and digital DNA-DNA hybridization values between strain COR-2T and its closely related species of the genus Erythrobacter were 79.3-85.5% and 24.1-29.1 %, respectively. The major respiratory quinone was Q-10, while the major fatty acids were C18 : 1 ω7c and C17 : 1 ω6c. The major polar lipids were phosphatidylethanolamine, phosphatidylglycerol, phosphatidylcholine, two unidentified phospholipids and eight unidentified lipids. Based on phylogenetic and phenotypic considerations, the two strains [COR-2T (type strain; = KACC 22941T=JCM 35529T) and CR-8 (= KACC 22945=JCM 35530)] are considered to represent novel species of the genus Erythrobacter, for which the name Erythrobacter oryzae sp. nov. is proposed.

Unexpected longevity, intergenerational policies, and fertility.

This paper studies the dynamic effects of longevity on intergenerational policies and fertility, distinguishing between effects of expected and unexpected longevity gains. Old agents become poorer from unexpected longevity gains than from expected gains, as they cannot prepare (save) for the former in advance. In an overlapping-generations model with means-tested pay-as-you-go social security, we show that young agents reduce their fertility when longevity increases because they need to save more for their old age ("life-cycle effect"), and in the unexpected case, they also need to pay taxes to support the impoverished elderly ("policy effect"). Using cross-country panel data on mortality rates and social expenditure, we find that an unexpected increase in life expectancy at age 65 lowers total fertility rate growth and government family-related spending growth while raising government old-age spending growth. Supplementary information: The online version contains supplementary material available at 10.1007/s00148-023-00943-3.

Later, Fewer, None? Recent Trends in Cohort Fertility in South Korea.

South Korea and other developed regions in East Asia have become forerunners of prolonged lowest-low fertility. South Korea's total fertility rate has been below 1.3 for two decades, the longest duration among OECD countries. Using vital statistics and census data, I study recent trends in the country's cohort fertility covering women born before the 1960s to those born in the 1980s. Analyzing outcomes at both the intensive margin of fertility (i.e., timing and number of children) and the extensive margin of family formation (i.e., marriage and childlessness), I document three novel patterns. First, the driver of low fertility has evolved across birth cohorts, from married women having later and fewer childbirths, to fewer women getting married, and finally to fewer women having children even if married. Second, a decomposition analysis of marriage and fertility changes indicates that the marriage and fertility decline was driven by changes within educational groups rather than by changes in women's educational composition. Third, the relationship between women's educational attainment and marriage or fertility was negative for the 1960s cohort, but an inverted U-shaped education gradient emerged beginning with the 1970s cohort.

Electrochemical Gene Amplification Signal Detection of Disposable Biochips Using Electrodes.

Real-time Polymerase Chain Reaction (RT-PCR), a molecular diagnostic technology, is spotlighted as one of the quickest and fastest diagnostic methods for the actual coronavirus (SARS-CoV-2). However, the fluorescent label-based technology of the RT-PCR technique requires expensive equipment and a sample pretreatment process for analysis. Therefore, this paper proposes a biochip based on Electrochemical Impedance Spectroscopy (EIS). In this paper, it was possible to see the change according to the concentration by measuring the impedance with a chip made of two electrodes with different shapes of sample DNA.

Open Platform Cameras Based Bio-Imaging Evaluation System.

With the active development of mobile devices, a variety of ultra-small, high-definition, and open platform-based cameras are being mass-produced. In this paper, we established an emulation system to verify the bio-imaging performance of the bulky and expensive high-performance cameras and various smartphone cameras that have been used in bio-imaging devices. In the proposed system, the linearity of the brightness gradient change of four types of cameras was compared and analyzed. Based on these results, three cameras were selected in order of excellent linearity, and gel image analysis results were compared.

Quantitative Analysis of Fluorescence Detection Using a Smartphone Camera for a PCR Chip.

Most existing commercial real-time polymerase chain reaction (RT-PCR) instruments are bulky because they contain expensive fluorescent detection sensors or complex optical structures. In this paper, we propose an RT-PCR system using a camera module for smartphones that is an ultra small, high-performance and low-cost sensor for fluorescence detection. The proposed system provides stable DNA amplification. A quantitative analysis of fluorescence intensity changes shows the camera's performance compared with that of commercial instruments. Changes in the performance between the experiments and the sets were also observed based on the threshold cycle values in a commercial RT-PCR system. The overall difference in the measured threshold cycles between the commercial system and the proposed camera was only 0.76 cycles, verifying the performance of the proposed system. The set calibration even reduced the difference to 0.41 cycles, which was less than the experimental variation in the commercial system, and there was no difference in performance.

Transition of Son Preference: Evidence From South Korea.

Sex ratio at birth remains highly skewed in many Asian countries because of son preference. The ratio in South Korea, however, declined beginning in 1990 and reached the natural range in 2007. We study changes in child gender effects on fertility and parental investment during this period of decreasing sex ratio at birth. We find that gender discrimination on the extensive margin (fertility), such as sex-selective abortions and son-biased stopping rules, have nearly disappeared among recent cohorts. On the intensive margin (parental inputs), boys receive higher expenditures on private academic education, have mothers with fewer hours of labor supply, and spend less time on household chores relative to girls. These gender gaps have also narrowed substantially, however, over the past two decades. We consider alternative explanations, but altogether, evidence suggests the weakening of son preference in South Korea.

Experimental method for measuring color appearance shifts in high-dynamic-range luminance conditions.

We present an experimental method to determine color appearance shifts under high-dynamic-range conditions. A couple of light booths with variable luminance provide high-dynamic-range luminance conditions, and a perceptual color shift between the two booths is determined using color appearance matching. For red, green, yellow, and blue groups of four surface color samples, color shifts were measured for nine subjects under a dual illumination at background luminance levels of $100\,\,{{\rm cd/m}^2}$100cd/m2 and $4700\,\,{{\rm cd/m}^2}$4700cd/m2. We observed significant perceptual hue shifts toward blue with magnitudes of 2.5 to 3.9 and 5.0 to 6.9 CIELAB units, for the red and green samples, respectively, and decreases in chroma for most samples when changed from low to high luminances.

Food Additive Titanium Dioxide and Its Fate in Commercial Foods.

Titanium dioxide (TiO2) is one of the most extensively utilized food additives (E171) in the food industry. Along with nanotechnology development, the concern about the presence of nanostructured particles in E171 TiO2 and commercial food products is growing. In the present study, the physicochemical properties of commercially available E171 TiO2 particles, including particle size distribution, were investigated, followed by their cytotoxicity and intestinal transport evaluation. The fate determination and quantification of E171 TiO2 in commercial foods were carried out based on the analytical procedure developed using simulated foods. The results demonstrated that TiO2 is a material mainly composed of particles larger than 100 nm, but present as an agglomerated or aggregated particle in commercial foods with amounts of less than 1% (wt/wt). Titanium dioxide particles generated reactive oxygen species and inhibited long-term colony formation, but the cytotoxicity was not related to particle size distribution or particle type (food- or general-grade). All TiO2 particles were mainly transported by microfold (M) cells, but also by intestinal tight junction. These findings will be useful for TiO2 application in the food industry and predicting its potential toxicity.

Performance evaluation of optimal real-time polymerase chain reaction achieved with reduced voltage.

BACKGROUND: Polymerase chain reaction (PCR) is used in nucleic acid tests of infectious diseases in point-of-care testing. Previous studies have demonstrated real-time PCR that uses a micro-PCR chip made of packing tape, double-sided tape, and a plastic cover with polycarbonate or polypropylene on a black matte printed circuit board substrate. Despite the success of DNA amplification and fluorescence detection using an early version of the micro-PCR chip, reaching the target temperature was fairly slow and, as a result, the total running time was getting longer. To reduce this runtime, the micro-PCR chip was modified by reducing the heater pattern size of the PCB substrate to one-quarter of the original size or less, while maintaining the ability of the heating pattern to cover the reservoir area of the microfluidic channel. In subsequent experiments, DNA amplification failed several times. During the analysis of the cause of this failure, it was found that the reagent was boiling with the heating range from 25 to 95 °C. METHODS: As a method of DNA amplification verification, images were captured by digital single-lens reflex camera to detect FAM fluorescence using diagonal illumination from a blue LED light source. The images were automatically captured at 72 °C (the extension step in nucleic acid amplification) and the brightness of the captured images was analyzed to con-firm the success of DNA amplification. RESULTS: Compared to the previous chip with a larger heating pattern size, the current chip appears to generate excess energy as the size of the heating pattern was reduced. To reduce this excess energy, the initial voltage was lowered to 2 V and 2.5 V, which is equivalent to a one-fifth and one-quarter voltage-power reduction in pulse width modulation control, respectively. In both voltage reduction cases, the DNA amplification was successful. CONCLUSIONS: DNA amplification tests may fail due to the excess energy generated by reducing the heater pattern size of the PCB substrate. However, the tests succeeded when the voltage was reduced to 2 V or 2.5 V. The 2.5 V power test was more efficient for reducing the overall running time.

Fluorescence detection test by black printed circuit board based microfluidic channel for polymerase chain reaction.

This paper proposes the optimal structure of a PCB-based micro PCR chip constructed on a PCB substrate using commercial adhesive tapes and plastic covers. The solder mask of the PCB substrate was coated black, and the area where the reaction chamber is attached was legend printed with white silk to minimize the noise during fluorescence detection. The performance of the PCR and fluorescence detection was compared using 6 types of reaction chambers, each made with different double-sided tapes. Three of the chambers were unsuccessful in completing the PCR. The performance of the other three chambers that successfully amplified DNA was compared using Taqman probe for Chlamydia Trachomatis DNA. The amplified product was illuminated diagonally with a blue LED to excite the product just before imaging, and the LED was turned off when the image was captured to prevent quenching of the probe. The images were taken 10 seconds prior to the last extension step for each cycle using a DSLR camera. The experiments were run as a quartet for each three chambers made with different double-sided tape. The results showed that there were significant difference between the three tapes.

Absolute measurement of hyperspectral and angular reflection.

A new instrument for absolute measurement of hyperspectral and angular reflection is presented. The instrument determines absolute values of angular reflection quantities in a wavelength range from 380 to 780 nm with a 3 nm spectral resolution by using a white source and a CCD-based spectroradiometer. Through uncertainty evaluation, the measurement uncertainty is determined as 1.4%-2.9% (k=2) for white diffuse material of Spectralon. The gonioreflectometric determination and an integrating-sphere-based reflection measurement traceable to KRISS spectral reflectance scale are compared by determining hemispherical reflectance, which results in agreement in their uncertainties.

Measurement of rod and cone effects in mesopic visual sensitivity by varying viewing field.

To investigate the effects of rods and cones in mesopic visual sensitivity, we perform spectral sensitivity experiments by varying viewing fields and adaptation levels. We obtain mesopic spectral sensitivities for 2° and 10° centrally viewing fields and a (10°-20°) peripherally viewing field at adaptation luminance levels of 0.04 cd/m², 0.4 cd/m², and 1.8 cd/m². The spectral shapes are examined through comparison with the Commission International de l'Eclairage luminous efficiency functions. We observe a decrease of visual sensitivity with an increase of adaptation luminance and the dependence of visual sensitivity on viewing field. The observation is discussed in terms of the interaction between rods and cones.

Simultaneous measurement of emittance, transmittance, and reflectance of semitransparent materials at elevated temperature.

A two-substrate method is developed to simultaneously determine emissivity, transmittance, and reflectance of semitransparent materials with a single measurement under the same environment at elevated temperature. The three quantities can be obtained through the emissivities of substrates and the apparent emissivities resulting from the radiance of the sample heated by substrates. The two-substrate method is compared with the conventional method by measuring sapphire samples with various thicknesses, resulting in good agreements for all the samples. The present method will be useful to measure the temperature dependence of optical properties of porous ceramic materials.

Measurement uncertainty evaluation for emission color and luminance of displays.

We present a measurement uncertainty evaluation for emission color and luminance of displays. The calibration procedures and the measurement uncertainties of a CCD-based spectroradiometer and a filter-type luminance meter are discussed. As evaluation examples, a Commission Internationale de l' Eclairage illuminant A, a liquid-crystal display with a light-emitting diode backlight, and a liquid-crystal display with a cold-cathode fluorescent lamp backlight are evaluated. The uncertainties in Commission Internationale de l' Eclairage 1931 (x,y) chromaticity coordinates are determined to be in a range from 0.0020 to 0.0050 (k=2). The uncertainties in luminance are obtained from 4.8% to 8.5% by using the spectroradiometer, while the filter-type luminance meter shows the uncertainties from 1.1% to 1.6% (k=2).

Picosecond pump-probe measurement of bandgap changes in SiO2/TiO2 one-dimensional photonic bandgap structures.

A picosecond pump-probe nonlinear optical measurement is performed in SiO2/TiO2 one-dimensional photonic bandgap structures fabricated by a solgel method. Both high and low band edges were examined by varying the probe wavelengths and angle tuning was also employed to further clarify the mechanism of a nonlinear optical response. The third-order nonlinear optical response in one-dimensional photonic bandgap structures that comprise TiO2 films is responsible for the nonlinear optical transmissions at both bandgap edges, with an 8% decrease at the low-energy edge and a 4.5% increase at the high-energy edge for a 355 nm pump intensity of 430 MW/cm2.

Determination of optical Kerr nonlinearity of a photonic bandgap structure by Z-scan measurement.

Through analysis of the dispersion relation in a photonic bandgap structure, the effective optical Kerr nonlinearity that determines a Z-scan profile particularly near the stop-band edges, is derived. Near and inside the stop band, the nonlinear optical phase change that originates from an off-resonant response is converted into a change in nonlinear optical intensity through Bragg reflection. The Z-scan measurement of a cholesteric liquid-crystal photonic bandgap structure confirmed that off-resonant Kerr nonlinearity is responsible for the characteristic open-aperture Z-scan profiles near the stop-band edges.

Electro-tunable optical diode based on photonic bandgap liquid-crystal heterojunctions.

Manipulation of light is in strong demand in information technologies. Among the wide range of linear and nonlinear optical devices that have been used, growing attention has been paid to photonic crystals that possess a periodic modulation of dielectric function. Among many photonic bandgap (PBG) structures, liquid crystals with periodic structures are very attractive as self-assembled photonic crystals, leading to optical devices such as dye lasers. Here we report a new hetero-PBG structure consisting of an anisotropic nematic layer sandwiched between two cholesteric liquid-crystal layers with different helical pitches. We optically visualized the dispersion relation of this structure, displaying the optical diode performance: that is, the non-reciprocal transmission of circular polarized light at the photonic-bandgap regions. Transmittance spectra with circularly polarized light also reveal the diode performance, which is well simulated in calculations that include an electro-tunable diode effect. Lasing action was also confirmed to show the diode effect with a particular directionality.

Enhanced optical nonlinearity near the photonic bandgap edges of a cholesteric liquid crystal.

The third-order Kerr nonlinear optical effect of a one-dimensional photonic bandgap structure of a cholesteric liquid crystal is investigated. In a femtosecond nonlinear transmission measurement, nonlinear optical changes in the bandgap edges are observed. From analysis of the dispersion relation, Kerr nonlinear coefficients of nematics, forming the cholesteric liquid crystal, are found to be enhanced by 1-2 orders of magnitude through the photonic bandgap structure.