In 10-minute speaking, N95 respirators significantly decreased SARS-CoV-2 emissions compared with no-mask wearing. However, SARS-CoV-2 was detected in the air even when wearing N95 and surgical masks in patients with high viral loads. Therefore, universal masking of infected and uninfected persons is important for preventing COVID-19 transmission via the air.

The crystal structure of biotite-1 M from Bancroft, Ontario, with the formula: $\left({\text{K}}_{1.96}{\text{Na}}_{0.13}{\text{Ca}}_{0.01}\right)\left({\text{Mg}}_{3.15}{\text{Fe}}_{2.59}^{2+}{\text{Ti}}_{0.17}{\text{Mn}}_{0.09}\right)\left({\text{Si}}_{5.98}{\text{Al}}_{1.92}{\text{Ti}}_{0.10}\right){\text{O}}_{20}\left[{\left(\text{OH}\right)}_{1.47}{\text{F}}_{1.98}\right]$, was determined by Rietveld refinement using high-resolution neutron powder diffraction at in situ temperatures ranging from 20 to 900°C. The room-temperature structure of the samples heated to between 400 and 900°C using an electric furnace in air was also refined. The crystal structures were refined to an RP of 2.98 — 5.06% and Rwp of 3.84–6.77%. For the in situ heating experiments in a vacuum, the unit-cell dimensions increased linearly to 600°C. The linear expansion coefficient for the c axis was 1.65 × 10−5°C−1, while those for the a and b dimensions were 4.44 × 10−6°C−1 and 5.21 × 10−6°C−1, respectively. Accordingly, the increase in the unit-cell volume up to 600 C occurred mainly along the c axis, resulting from the expansion in the K coordination sphere along that direction. Results for all K−O bonds were analyzed in terms of the lattice component and an inner component of the structural strain. The ditrigonal distortion decreased (3.76 at 20°C to 1.95 at 600°C) with temperature, because the shorter bonds expanded and the longer bonds contracted. The increase in the interlayer separation and the decrease in the interlayer octahedral flattening angle confirmed that the c-dominated expansion occurred in the interlayer region. In the case of the ex situ-heated samples, the cell dimensions decreased sharply at temperatures over 400 C. The octahedral sheet thickness and mean <M−O> distance decreased linearly due to oxidation of octahedral Fe. However, the interlayer separation and mean <K−O> distance decreased at temperatures over 400°C. At 400°C, dehydroxylation began to increase and interlayer regions became more constricted. The overall cell parameters decreased rapidly with increasing temperatures due to dehydroxylation. The large inner strain components in the K−O bonds also resulted in an increase in the considerable ditrigonal distortion (3.57° at 400°C to 6.15° at 900°C).

The preparation of transmission electron microscopy (TEM) samples from powders is quite difficult and challenging. For powders with particles in the 1–5 μm size range, it is especially difficult to select an adequate sample preparation technique. Epoxy is commonly used to bind powder, but drawbacks, such as differential milling originating from unequal milling rates between the epoxy and powder, remain. We propose a new, simple method for preparing TEM samples. This method is especially useful for powders with particles in the 1–5 μm size range that are vulnerable to oxidation. The method uses solder as an embedding agent together with focused ion beam (FIB) milling. The powder was embedded in low-temperature solder using a conventional hot-mounting instrument. Subsequently, FIB was used to fabricate thin TEM samples via the lift-out technique. The solder proved to be more effective than epoxy in producing thin TEM samples with large areas. The problem of differential milling was mitigated, and the solder binder was more stable than epoxy under an electron beam. This methodology can be applied for preparing TEM samples from various powders that are either vulnerable to oxidation or composed of high atomic number elements.

Oxidative stress may be affected by lead exposure as well as antioxidants, yet little is known about the interaction between dietary antioxidants and blood lead levels (BLL) on oxidative stress level. We investigated the interaction between dietary antioxidants and BLL on oxidative stress level. As part of the Biomarker Monitoring for Environmental Health conducted in Seoul and Incheon, Korea, between April and December 2005, we analysed data from 683 adults (female = 47·4 %, mean age 51·4 (sd 8·4) years) who had complete measures on BLL, dietary intakes and oxidative stress marker (urinary 8-hydroxy-2′-deoxyguanosine (8-OHdG)). Dietary intakes were assessed by a validated semi-quantitative FFQ, BLL was measured using atomic absorption spectrophotometry, and 8-OHdG by ELISA. Multivariate linear regression analyses were used to evaluate the influence of BLL on the association between dietary antioxidants and 8-OHdG. Geometric means of BLL and 8-OHdG concentrations were 4·1 (sd 1·5) μg/dl and 5·4 (sd 1·9) μg/g creatinine, respectively. Increases of vitamins C and E were significantly associated with the decrease of log10 8-OHdG in the adults from the lowest quartile of the BLL group ( ≤ 3·18 μg/dl, geometric mean = 2·36 μg/dl) than those of the highest quartile BLL group (>5·36 μg/dl, geometric mean = 6·78 μg/dl). Regarding antioxidant-related foods, vegetables excluding kimchi showed a higher inverse relationship with 8-OHdG in the lowest quartile BLL group than the highest group. These findings suggest a rationale for lowering the BLL and increasing the intake of dietary antioxidants in the urban population in Korea.

Stream restoration is an important process affecting the ecological health of stream ecosystems. There have been numerous cases of restoration, dealing with either structural or biological changes. In Korea, most restoration projects have merely dealt with improving hydrological characteristics or water quality; however, in recent years the improvement of ecological characteristics has been an increasing focus for restoration projects. In this study, we utilized data collected from 5675 stream sites in May 2007 to discover general patterns of anthropogenic modification in Korean streams. The survey results after application of the stream modification index (SMI; presence or absence type; high scores indicate more disturbed) provided a general distribution of disturbed/undisturbed streams or rivers in the watershed. We then compared the level of modification with the socio-geographical patterns (population, land coverage, elevation, and slope) for the watershed. The results show that streams in highly populated areas suffered from human modification compared with other well-preserved stream sites. In metropolitan cities, urbanized areas had positive relationship as identified by a high SMI. On the other hand, agricultural land cover identified an SMI increase for lowland river area. In general, mountainous streams possessed a better status in stream morphology due to different land-cover patterns (i.e., mainly forested area); however, some mountainous areas were impacted by concentrated summer rainfall. We could distinguish the forcing variables (i.e., land use pattern) for the disturbed streams through a comparison between the SMI and geographical information; the SMI application was able to identify areas of high necessity for restoration.

This study aimed to investigate whether aquaporin 3 (Aqp3) mRNAs are expressed in immature oocytes and altered during in vitro maturation process. Five- to 6-week-old female ICR mice were primed by gonadotropin for 24 and 48 h. Immature oocytes obtained 48 h after priming were also matured in vitro for 17 to 18 h. In vivo matured oocytes were obtained after 48 h priming followed by hCG injection. Total RNAs were extracted from 80 to 150 oocytes in each experimental group, and the levels of Aqp3 mRNA were quantified by real-time reverse transcriptase polymerase chain reaction. The experiments were repeated twice using different oocytes. The Aqp3 mRNA was expressed in immature oocytes, as well as in in vitro and in vivo matured oocytes. The expression level was higher in immature oocytes obtained 48 h after priming (17.2 ± 8.6, mean ± SD) than those with no priming (5.7 ± 0.8) or obtained 24 h after priming (2.5 ± 0.8). The expression of Aqp3 mRNA decreased after in vitro maturation (1.2 ± 0.5), which was similar to in vivo matured oocytes (1.0 ± 0.0). Our work demonstrated that Aqp3 mRNA expression increased during the development of immature oocyte but decreased after completion of in vitro maturation. The results indicate that AQP3 is certainly needed for the acquisition of immature oocytes’ full growing potential within antral follicles.

A bistable effects of Au nano-crystals embedded in poly(N-vinylcarbazole) (PVK) were observed. Subsequently we investigated dependency of the nonvolatile memory behavior on curing temperature for the Au nano-crystals embedded in the PVK. For the study, in the devices of different curing temperatures we measured current-voltage characteristics for the devices and investigated the formation of the Au nano-crystals using cross sectional transmission electron microscopy (TEM). The nonvolatile memory behavior depends on the curing temperature, which is attributed to the suitable formation of the Au nano-crystal.

A significant degradation of current gain of InP/InGaAs/InP double heterojunction bipolar transistors was observed after passivation. The amount of degradation depended on the degree of surface exposure of the p-type InGaAs base layer according to the epi-structure and device structure. The deposition conditions such as deposition temperature, kinds of materials (silicon oxide, silicon nitride and aluminum oxide) and film thickness were not major variables to affect the device performance. The gain reduction was prevented by the BOE treatment before the passivation. A possible explanation of this behavior is that unstable non-stoichiometric surface states produced by excess In, Ga, or As after mesa etching are eliminated by BOE treatment and reduce the surface recombination sites.

AlxGa1-xN sample with x=0.36 was epitaxially grown on sapphire by MOCVD. SAW velocity of 5420 m/s and TCF (temperature coefficient of frequency) of -51.20 ppm/°C were measured from the SAW devices fabricated on the AlxGa1-xN sample, when kh value was 0.078, at temperatures between –30 °C and 60 °C Electromechanical coupling coefficient was ranged from 1.26 % to 2.22 %. The fabricated SAW filter have shown a good device performance with insertion loss of -33.853 dB and side lobe attenuation of 20 dB.

Telomerase maintains the length of telomeres in immortal cells and is also often associated with cell proliferation. Cholesteatoma epithelium is characterized by a dysregulation with hyperproliferative growth. The study evaluated the telomerase activity in cholesteatoma and normal retro-auricular skin to discover the relationship between telomerase expression and clinical findings. Twenty-two samples of cholesteatoma and 15 samples of retro-auricular skin were obtained from patients undergoing middle-ear surgery. The telomerase activity was detected by the telomerase repeat amplification protocol (TRAP) assay method. Seventeen of the 22 (77.3 per cent) cholesteatoma cases expressed telomerase activity, whereas none of the 15 retro-auricular normal skin (0 per cent) detected telomerase activity. There was no significant difference between telomerase expressions and clinical findings, including hearing level, duration of disease, and the degree of extension (p>0.05). The high expression of telomerase in cholesteatoma suggests that the activation of telomerase may be related to the proliferative nature of cholesteatoma.

Boundary properties between two adjacent grains with different crystallographic orientation relation are important factors in deciding the mechanical properties of materials. in our previous reports, we introduced the geometric compatibility equation as a factor determining the brittle crack propagation condition into the adjacent grain in banitic low alloy steel as follows:

M = cos α · cos θ

where α is the angle between crack normal in the cracked grain-I and normal to (001) plane in the adjacent grain-II and θ is the angle between normal to (001) plane in the grain II and loading axis.(see FIG. 1) Higher M gives greater possibility to the crack propagation. The geometric compatibility factor (M) could be easily calculated from the crystallographic data obtained from Electron Backscatter Diffraction (EBSD) analysis, and successfully predicted actual crack propagation plane. We also found that there was a critical M value to arrest the brittle crack propagation at the boundaries.

Boundary properties between two adjacent grains with different crystallographic orientation relation are important factors in deciding the mechanical properties of materials. The concept of the geometric compatibility factor has been introduced in order to explain the relationship between transfer of deformation mode and crystal orientation. In the same manner, when the brittle crack propagates, grain boundary also obstructs crack propagation. Therefore it is also possible to introduce the concept of geometric compatibility considering the crystallographic orientation in analyzing the crack propagation.

In this study, the characteristics of the brittle crack propagation in bainitic low alloy steel with compositions shown in table 1 have been investigated using EBSD analysis. A 3-point bending test was performed at -100°C and the secondary crack below fracture surface was analyzed in relation to the crystallographic orientation. In order to explain the behavior of crack propagation, modified geometric compatibility factor, M was introduced considering loading axis and crystallographic orientation relationship.

Bainitic low alloy steel has a complex microstructure exhibiting several types of boundaries. The boundaries in bainitic steel, although certain boundaries are absent with respect to the alloy composition and the manufacturing process, could be typically divided into 4 types; dislocation cell boundary, lath boundary, packet boundary, and prior austenite grain boundary, in increasing order of size. The size and distribution of the respective boundaries are an important factor which controls the mechanical properties of the steels, including brittle fracture. In the present research, the characteristics of the boundaries in the bainitic low alloy steels were investigated in view of misorientation between grains enclosed by the respective boundaries.

The alloys investigated were Mn-Mo-Ni low alloy forging steels having chemical compositions shown in TABLE 1. Steel-A was manufactured by the Vacuum Carbon Deoxidation(VCD) process. For the finer prior austenite grain size, Steel-B was produced by the aluminium addition and the silicon killing process. Before EBSD analysis, the microstructures of the alloys were observed using SEM and TEM. EBSD measurements were obtained using a Link OPAL system(Oxford) linked to a JEOL JSM 6300 SEM operating at 15KeV with the sample tilted at 70°.

Monoclinic gallium oxide (β-Ga2O3) nanowires were catalytically synthesized by electric arc discharge of GaN powders mixed with a small amount (less than 5 %) of transition metals under a pressure of 500 Torr (80 %-Ar + 20 %-O2). Scanning electron microscope (SEM) and high-resolution transmission electron microscope (HRTEM) images showed that the average diameter of the wires were about 30 nm and their lengths were as long as up to one hundred micrometer, resulting in extremely large aspect ratio. Fourier diffractogram was indicative of single crystalline nature of the β-Ga2O3 wire. HRTEM image also showed β-Ga2O3 with twin defects at the center of the wire which might play as nucleation seeds. Both X-ray diffraction (XRD) patterns and FT-Raman spectra of the wires identified the observed nanowires as monoclinic crystalline gallium oxides.

Compression tests were performed on specially-oriented PST TiAl crystals to which strain gages were attached in order to precisely measure the three axial strains in the samples during deformation. It was found that all samples deform by plane strain except when the compression axis is nearly perpendicular to the lamellar planes. This measurement technique was used to determine the orientations in which the various slip systems are operative in PST samples, and this, in turn was employed to explain the shape of the flow stress vs. orientation curve. An important component of this explanation is the fact that slip of ordinary dislocations and twinning are closely coupled in this material, implying that the twinning must occur relatively slowly-at about the same rate that ordinary dislocations move. Atomistic calculations have shown that a slow twinning process is to be expected in this material at low temperatures, perhaps even by a thermally activated process.