Korea Research Institute Of Standards And Science Research Articles

Particulate Matter Induces Oxidative Stress and Ferroptosis in Human Lung Epithelial Cells.

Numerous toxicological studies have highlighted the association between urban particulate matter (PM) and increased respiratory infections and lung diseases. The adverse impact on the lungs is directly linked to the complex composition of particulate matter, initiating reactive oxygen species (ROS) production and consequent lipid peroxidation. Excessive ROS, particularly within mitochondria, can destroy subcellular organelles through various pathways. In this study, we confirmed the induction of ferroptosis, an iron-dependent cell death, upon exposure to an urban PM using RT-qPCR and signaling pathway analysis. We used KRISS CRM 109-02-004, the certified reference material for the analysis of particulate matter, produced by the Korea Research Institute of Standards and Science (KRISS). To validate that ferroptosis causes lung endothelial toxicity, we assessed intracellular mitochondrial potential, ROS overproduction, lipid peroxidation, and specific ferroptosis biomarkers. Following exposure to the urban PM, a significant increase in ROS generation and a decrease in mitochondrial potential were observed. Furthermore, it induced hallmarks of ferroptosis, including the accumulation of lipid peroxidation, the loss of antioxidant defenses, and cellular iron accumulation. In addition, the occurrence of oxidative stress as a key feature of ferroptosis was confirmed by increased expression levels of specific oxidative stress markers such as NQO1, CYP1B1, FTH1, SOD2, and NRF. Finally, a significant increase in key ferroptosis markers was observed, including xCT/SLC7A11, NQO1, TRIM16, HMOX-1, FTL, FTH1, CYP1B1, CHAC1, and GPX4. This provides evidence that elevated ROS levels induce oxidative stress, which ultimately triggers ferroptosis. In conclusion, our results show that the urban PM, KRISS CRM, induces cellular and mitochondrial ROS production, leading to oxidative stress and subsequent ferroptosis. These results suggest that it may induce ferroptosis through ROS generation and may offer potential strategies for the treatment of lung diseases.

Comparison of the standards for absorbed dose to water of the IAEA and the KRISS, Korea in accelerator photon beams

A bilateral comparison was conducted between the International Atomic Energy Agency (IAEA) and the Korea Research Institute of Standards and Science (KRISS) to measure the absorbed dose to water in accelerator photon beams. KRISS served as a linking laboratory to compare the IAEA standard with the key comparison reference value (KCRV) of the BIPM.RI(I)–K6 program, in which KRISS participated in 2017.Two ionization chambers from the IAEA were used as transfer instruments for the comparison. Both laboratories measured the calibration coefficients of these instruments and calculated the ratios. The ratio of the KRISS standard to the KCRV was applied to obtain the degree of equivalence of the IAEA, along with its uncertainty. The largest deviation of the IAEA measurement from the KCRV was 3.4 mGy/Gy, significantly smaller than the expanded uncertainty of 10.7 mGy/Gy (k = 2, 95% level of confidence).This study demonstrates the equivalence of IAEA's measurement standard for accelerator photon beams to other primary standard dosimetry laboratories. It provides evidence for the satisfactory operation of IAEA's quality management system and enhances the international credibility of the IAEA SSDL network, particularly in high-energy accelerator photon beams from linear accelerators.

Evaluation of the relativistic redshift in frequency standards at KRISS

Relativistic redshift correction should be accurately considered in frequency comparisons between frequency standards. In this study, we evaluated the relativistic redshift at Korea Research Institute of Standards and Science (KRISS) using three different methods, depending on whether the approach was traditional or modern or whether the geopotential model was global or local. The results of the three methods agreed well with one another, and the height of an Yb optical lattice clock (KRISS-Yb1) was determined to be 75.15 m with an uncertainty of 0.04 m with respect to the conventionally adopted equipotential surface W0CGPM , the value of which is defined to be 62 636 856.0 m2s−2. Accordingly, the relativistic redshift of KRISS-Yb1 was evaluated to be 8.193(4) × 10−15. These data are applicable to the frequency standards at KRISS, one of which regularly participates in the calibration of the International Atomic Time.

Quantum Computing Research at the National Metrology Institute

With a wide range of promising applications arising from unprecedented computing performance, quantum computing has recently received great attention. This technology that relies on quantum superposition and quantum entanglement can be realized in various physical platforms such as superconducting quantum devices, optical systems, semiconductor nanostructures and neutral atoms and so on. The Korea Research Institute of Standards and Science (KRISS), the national metrology institute of Korea, is actively carrying out research on quantum computing technologies with its extensive experience and expertise obtained from the development of measurement standards and precision measurement technologies based on diverse physical systems. In this article, we briefly discuss quantum computing research activities at KRISS.

Development of a coulometry system at the Korea Research Institute of Standards and Science and evaluation of the measurement uncertainty originating from the system

Coulometry is used to realize the definition of the mole and enables the direct determination of the purity of high-purity substances that are used as standards for other relative measurements with very small measurement uncertainty. However, despite several studies reporting the development of accurate and precise coulometry systems, there is a lack of detailed description of the system and systematic evaluation of the measurement uncertainty arising from the system. In this study, coulometry systems constructed at the Korea Research Institute of Standards and Science (KRISS) are described in detail and the uncertainties associated with these systems are systematically evaluated using a bottom-up approach. The relative expanded uncertainty resulting from the measurement system for the amount-of-substance content of acid in high-purity potassium hydrogen phthalate is approximately 0.0005%. The performance of the KRISS coulometry systems has been verified through several international comparisons and comparative measurements using certified reference materials.

Bilateral comparison between viscosity measurement standard systems developed by KRISS and PTB

The viscosity measurement standard systems developed by the Korea Research Institute of Standards and Science (KRISS) and Physikalisch–Technische–Bundesanstalt (PTB) were compared, and the international equivalence of the standard viscosity measurement system built by KRISS was confirmed. In the system developed by KRISS, the measurement range of the viscosity measurement standard system was 0.3–100000 mm2/s with 0.17–0.5% uncertainty (U, k = 2). The density of a liquid was measured using a pycnometer, and an absolute viscosity of 0.3–8000 mPas was measured with an uncertainty of 0.18–0.6%. The viscosity measurement standard systems of KRISS and PTB were bilaterally compared, using three different viscosity standard liquids synthesized by PTB, under six experimental conditions. Considering the uncertainty, the calculated En was < 1 (0.17–0.72) for all experimental cases. Therefore, we confirmed the viscosity standard system created recently by KRISS to be significantly equivalent to that developed by PTB.

Smokestack gas velocity measurements using 3D pitot tubes in a coal-fired power plant

On the path to carbon neutrality to reduce greenhouse gas (GHG) emissions, the Korean government has mandated legislation for controlling and monitoring GHG emissions emitted from smokestacks. A continuous emission measurement (CEM) method is considered to be the most reliable for determining CO2 emissions from stationary sources. In Korea, an S-type Pitot tube is the most popular technique to measure the gas velocity in a smokestack, but it will result in a certain error when the non-axial velocity components exist. To vanquish this limitation, Korea Research Institute of Standards and Science (KRISS) developed a nulling smokestack flow measurement (NSFM) instrument equipped with 3D Pitot tubes for taking on-site stack gas velocity measurements. 3D Pitot tubes used in this research, such as prism Pitot tube and sphere Pitot tube, are calibrated in the KRISS airspeed system. The instrument using 3D Pitot tubes with the nulling technique is expected to diminish the restriction on S-type Pitot tubes, and to enhance the quality of the GHG emission measurements in the smokestack. The 3D Pitot tubes can measure both axial and non-axial velocity components of a flow, whereas the S-type Pitot tubes can measure only the axial velocity component. The averaged axial velocity of the stack gas as measured by this instrument has expanded uncertainty of 3.3% (P = 95%, k = 2) for both prism and sphere Pitot tubes.

Final report on APMP.EM-K2 key comparison of resistance standards at 10 MΩ and 1 GΩ

Main textIn order to link the National Metrology Institutes (NMI) organized in Asia Pacific Metrology Programme (APMP) to the key comparison CCEM-K2, APMP.EM-K2 key comparison was piloted by the Korea Research Institute of Standards and Science (KRISS), beginning in July 2010 and completed July 2014 with the participation of 13 National Metrology Institutes (NMIs). The results of this key comparison for 10 MΩ and 1 GΩ standards indicate good agreement among the 13 participating NMIs despite the long comparison period. Agreement is well within the level of confidence of 95%.To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database https://www.bipm.org/kcdb/.The final report has been peer-reviewed and approved for publication by the CCEM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

APMP-APLAC joint proficiency testing programs for elemental analysis in food with metrological reference values: Assessment of participants' performance considering measurement uncertainties

The Asia Pacific Metrology Program (APMP) and the Asia Pacific Laboratory Accreditation Cooperation (APLAC) joint Proficiency Testing (PT) programs for toxic elements such as cadmium (Cd) and lead (Pb) or nutritional elements such as iron (Fe) and zinc (Zn) in food were organized by the Korea Research Institute of Standards and Science (KRISS) with the aim of enhancing the quality of measurement and metrological traceability in various economies of the Asia Pacific region by evaluating the performance with rigorous evaluation. Three APMP-APLAC joint PT programs for elemental analyses were carried out by KRISS sequentially, where candidate certified reference materials (CRMs) were used as the PT materials and metrologically traceable certified reference values (RVs) were used as the PT assigned values for the evaluation of participants' results, which allows reliable evaluation of participant performance. This article describes the operation of the PTs and the overall performance of the participating laboratories. The effectiveness of these joint PT programs and trends in PT performance assessment are also discussed. These PT programs confirm the significant importance of using the metrologically traceable RVs instead of the consensus values from participants as the PT assigned value for reliable assessment. The lack of understanding of the concept of coverage factor, degree of freedom, standard uncertainty, and expanded uncertainty was revealed by some participants in these PT programs. Interpreting the zeta-scores or En scores, which are derived by using measurement uncertainties, in conjunction with the z-scores is highly meaningful for assessing participants' ability in measurement capabilities and measurement uncertainty evaluation. Assessment of participants' performance considering measurement uncertainties helps the participants to check how reasonable their measurement uncertainty estimation was. The results of PTs also demonstrated that these PT programs are useful for improving the measurement capability of the laboratories, whereas more capability-building in uncertainty evaluation is required for further improvement.

Development of a miniature digital data processing 4πβ(LS)-γ(LaBr3) coincidence system at KRISS

A miniature 4πβ(LS)–γ(LaBr3) coincidence system for the activity measurement of beta-gamma-emitting nuclei was developed using digital data processing at the Korea Research Institute of Standards and Science (KRISS). The system was configured with two photomultiplier tubes for beta measurements, and two LaBr3 gamma detectors. A pilot experiment was conducted using a60Co source. The highest beta-detection efficiency achieved with 60Co was found to be 93.7%. The activity concentration with the new system was found to be (5665 ± 27) kBq (k = 2). This value is in agreement with the reference ionization chamber at KRISS within the uncertainty of the new system.

Air temperature dependencies on the structure of thermometer screens in summer at Daejeon, South Korea

AbstractResults and accuracy of air temperature measurements made by meteorological thermometers hosted in thermometer screens strongly depend on the structure of the thermometer screen itself. In this study, the experiment was designed and conducted to understand the effect of radiation on air temperature observation. In order to control radiation sensitivity of thermometer screen, an umbrella made of Al alloy was installed over the thermometer screen (KTU). Air temperatures measured from five thermometer screens have been studied for several weather conditions using a 2‐month field experiment at Korea Research Institute of Standards and Science (KRISS). The experiments comprised two version of KRISS type, which artificially ventilated thermometer screen (KTE and KTU) and three naturally ventilated round‐shaped multi‐plate thermometer screens (BT1, BT2, VT). The results showed that the air temperature of the KTU was approximately 0.10–0.50°C lower than the other group of thermometer screens without an umbrella, which blocked direct solar radiation. During the night, the umbrella minimizes the longwave energy from the KTU to the atmosphere. So the air temperature was roughly 0.10–0.18°C higher than that of the other group without the umbrella. It is confirmed that the umbrella installed over the thermometer screen minimizes the radiation sensitivity of the thermometer screen, and it has a significant effect on air temperature measurements.

Design and fabrication of a heat switch for a SQUID-based superconducting gravimeter

Korea Research Institute of Standards and Science (KRISS) has started to design a Superconducting Gravimeter system based on a SQUID sensor. In this paper, we describe the design and fabrication of fundamental components of the superconducting circuit. Heat switches (HSWs) were fabricated using surface-mounted device (SMD) resistors and niobium (Nb) wires in a variety of ways to provide DC current to superconducting coils. The HSWs were tested regarding response time, wave form, and aging features at a cryogenic temperature (4.2 K) for 40 days. These results allowed us to optimize the HSW designs, superconducting housing, and superconducting circuits of the system. The system was designed as a drive controller to inject constant current into the superconducting coils and to control the operating times of the HSWs and the constant current. In addition, we also describe a suitable method for calculating the inductance of the closed superconducting loops.

International comparison CCQM-K165: dimethyl sulfide in nitrogen at 5 nmol mol-1

Main textDimethyl sulfide (DMS) is produced mainly by the metabolic activities of oceanic phytoplankton and the most abundant natural sulfur compound in the atmosphere. DMS plays an important role for climate change since it is oxidized and forms sulfate aerosols in the atmosphere, affecting the Earth's radiation budget directly and indirectly. DMS is designated as one of the target reactive gases and monitored in the World Meteorological Organization (WMO) Global Atmospheric Watch (GAW) programme. It is important to accurately monitor its global background levels with SI traceability for better understanding of the role of DMS in climate change. This comparison is organized by Korea Research Institute of Standards and Science (KRISS). Gas mixtures gravimetrically prepared by KRISS are used for demonstrating measurement equivalence at the highest metrological level. This comparison (Track C) is designed to underpin participants' measurement capabilities of trace level DMS in nitrogen at the nominal amount fraction of 5 nmol mol-1.To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database https://www.bipm.org/kcdb/.The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Key comparison BIPM.RI(I)-K1 of the air-kerma standards of the KRISS, Republic of Korea and the BIPM in 60Co gamma radiation

Main textA new key comparison of the standards for air kerma of the Korea Research Institute of Standards and Science (KRISS), Republic of Korea, and the Bureau International des Poids et Mesures (BIPM) was carried out in the 60Co radiation beam of the BIPM in March 2022. The comparison result, based on the calibration coefficients for two transfer chambers and expressed as a ratio of the KRISS and the BIPM standards for air kerma, is 1.0006 with a combined standard uncertainty of 1.8 parts in 103. The result agrees within the uncertainties with the direct comparison carried out in 2010. The results are analysed and presented in terms of degrees of equivalence, suitable for entry in the BIPM key comparison database.To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database https://www.bipm.org/kcdb/.The final report has been peer-reviewed and approved for publication by the CCRI, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Key comparison BIPM.RI(I)-K4 of the absorbed dose to water standards of the KRISS, Republic of Korea and the BIPM in 60Co gamma radiation

Main textA first key comparison of the standards for absorbed dose to water of the Korea Research Institute of Standards and Science (KRISS), Republic of Korea, and the Bureau International des Poids et Mesures (BIPM) was carried out in the 60Co radiation beam of the BIPM in March 2022. The comparison result, based on the calibration coefficients for two transfer standards and evaluated as a ratio of the KRISS and the BIPM standards for absorbed dose to water, is 0.9986 with a combined standard uncertainty of 3.8 parts in 103. The results are analysed and presented in terms of degrees of equivalence, suitable for entry in the BIPM key comparison database.To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database https://www.bipm.org/kcdb/.The final report has been peer-reviewed and approved for publication by the CCRI, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Development of a new KRISS low frost-point generator with improved uncertainty from 7 nmol·mol−1 to 1000 nmol·mol−1

A new saturator-based low frost-point generator (LFPG 2) is developed at the Korea Research Institute of Standards and Science (KRISS), and its uncertainty is evaluated from 7 nmol·mol−1 to 1000 nmol·mol−1 in nitrogen. The humidity generator operates in the two-temperature two-pressure mode to achieve target water vapor concentrations. First, the apparatus of the generator and the operation procedures, including purging mode and generation mode, are introduced in depth. Then, all uncertainty factors that affect trace-moisture generations are analyzed using a hygrometer based on cavity-ring down spectroscopy. Consequently, the expanded relative uncertainties in the range of (7–1000) nmol·mol−1 are 5.0%–1.0% at a coverage factor of k = 2, respectively. It is found that the effect of water adsorption/desorption is significantly reduced with compact design and sufficient purging. Thus, the uncertainty of the generator is enhanced compared with trace-moisture standards in other national metrology institutes including the KRISS LFPG 1. Finally, the time scales of humidity generations for various flow rates are investigated for efficient calibration of the hygrometers.

Development of a movable 4πβ(LS)−γ coincidence counting system for activity standardization of β−γ emitters

A new movable 3PM-γ coincidence system, based on 4πβ(LS)−γ coincidence counting, for activity measurement of β-γ emitters has been designed at the Korea Research Institute of Standards and Science (KRISS). The system incorporates 3 PM tubes on the plane and two detectors placed above and below the center of the plane. The 3 PM tubes for β–counters in the plane are movable up to 100 mm from a liquid scintillation vial, thus enabling the variation of β−detection efficiencies by a geometrical technique. A NaI(Tl) γ-counter was set above for the present work. The β-event is determined by counting the logical sum of three double coincidences. All the necessary electronics, i.e., logical sum, adjusting the duration of dead-time of each counting channel and coincidence resolving times, and analyzing coincidence relation, were specially designed to be fabricated in an integrated circuit. Details of the detectors, the electronics, the overall movable 3PM-γ coincidence system are presented, as well as the results of investigations to assess its operating characteristics. Validation measurements have been performed with 60Co and 57Co sources. The highest β−detection efficiency achieved with 60Co and 57Co was 97% and 95%, respectively. The activity concentration determined with a new system agreed with calibrated values within the uncertainty range. Further results from validation measurements and the corresponding uncertainty budgets are presented.

Changes of KRISS primary standards by implementing ICRU 90 recommendation

The International Commission of Radiation Units and Measurements (ICRU) published report No. 90 (i.e., Key Data for Ionizing Radiation Dosimetry: Measurement Standards and Applications) in 2016. The present study explores the impact of ICRU 90 on the primary standards of the Korea Research Institute of Standards and Science (KRISS). To this end, first, two new correction factors (kii and kw) for the free-air ionization chambers were introduced; it influences the standards related to kV X-ray beams. The new correction factors were calculated by simulating the initial electrons’ generations using the GEANT4 code. The second recommendation considered was for changes in the mean excitation energies of graphite and water, and the use of the crystalline density of graphite in the stopping power evaluation. These recommendations should be adopted for the graphite-walled cavity chamber and graphite calorimeter, which are the primary standards of the KRISS for air kerma in gamma rays and absorbed dose to water in high-energy photons, respectively. EGSnrc code-based evaluations of the electron stopping-power ratios for gamma rays were performed for the KRISS graphite-walled cavity chamber. Regarding graphite calorimetry in high-energy photon beams, the recommendations on graphite and water have been studied and presented in a previous paper. The third consideration is the recommendation for increasing uncertainty of the mean energy of electrons expended in dry air per ion pair production, $${\left(W/e\right)}_{\mathrm{air}}$$ , from 0.15% to 0.35%. The impact of the increased uncertainty under the conditions of the use of the existing components was summarized, together with the overall changes to the KRISS primary standards related to air kerma. Consequently, the difference between the products of the calculated kii and kW for the free-air ionization chamber standard and the corresponding values given in the ICRU 90 report was less than 0.10% for mono-energetic photons in the range of 1–400 keV. Regarding the X-ray beams recommended by the Consultative Committee for Ionizing Radiation (CCRI), the calculated correction factors deviated from those of the Bureau International des Poids et Mesures (BIPM) standards by 0.03%. In the case of the graphite-walled cavity chamber, changes of 0.65–0.77% were observed for the gamma-ray air kerma standards. The observed changes were reasonable, considering that similar changes were found in those reported by other research groups. Regarding the combined uncertainties, the uncertainties for the air kerma primary standards increased up to approximately 0.40%, primarily because of $${\left(W/e\right)}_{air}$$ . The changes to the KRISS primary standards that were observed in the present study will be adopted for the measurements performed since 2021.

Key comparison study on protein quantification: purity-assessed recombinant protein contents in buffer solution using insulin analogue

Main textThe key comparison CCQM-K151 protein quantification: Purity-assessed recombinant protein contents in buffer solution using Insulin analogue was coordinated by Korea Research Institute of Standards and Science (KRISS) under the auspices of the Protein Analysis Working Group (PAWG) of the Consultative Committee for Amount of Substance: Metrology in Chemistry and Biology (CCQM) CCQM.Nine National Metrology Institutes and Designated Institutes participated. Participants were required to assign the mass fraction of human insulin analogue (Ins) present as the main component in the comparison sample for CCQM-K151.This study provided the means for assessing measurement capabilities for determination of purity-evaluated recombinant proteins up to 10 kDa containing up to 3 disulfide cross-links in an aqueous calibration solution using amino acid based ID-LC-MS. Sample purity was confirmed by coordinating lab. Nine results were submitted. All results applied the LC-MS/MS method and isotope dilution mass spectrometry (ID-MS) method for quantification of Ins by amino acid analysis through acid hydrolysis. Among nine results, the Key Comparison Reference Value (KCRV) was assigned with six results. The assigned KCRV was the arithmetic mean of the six results, of 3440 mg/kg with a combined standard uncertainty of 13.5 mg/kg, the k-factor for the estimation of the expanded uncertainty of the KCRVs was chosen as k=2.57. Three participants, reported lower values than the other six, requested another set of test materials for additional experiments to investigate source of discrepancy in their results, and therefore were excluded from KCRV estimation in CCQM-K151. Three participants progressed substantial experiments with further investigation into their negative-biased factor, and actively proved their measurement capability. The degree of equivalence (with the KCRV) and its uncertainty was calculated for each result. Six of the participants were able to demonstrate the ability to quantitatively determine purity-assessed recombinant protein in buffer solution.To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Long-term drift analysis of Zener voltage standards and proposal of an initial calibration interval using calibration records accumulated for 15 years

In electrical metrology, voltage is a key quantity together with resistance for realising all electric standards in the low-frequency range. Zener voltage standards are accepted as the most stable to disseminate voltage references traceable to the Josephson standard devices. We study the long-term drift of the Zener devices to propose their initial calibration interval (CI), statistically analysing the calibration records accumulated for 15 years at the Korea Research Institute of Standards and Science (KRISS). First, we apply the direct method where the measurement reliability is obtained by integrating the probability density functions acquired from kernel density estimation (KDE). Markov chain Monte Carlo (MCMC) has been successfully demonstrated to determine the parameters of the Weibull reliability model. A numerical experiment was performed to confirm that the MCMC method works properly and is able to replace the S3 method of NCSLI. The direct method agrees with the MCMC within the highest posterior density (HPD) obtained by the MCMC method. The KDEs of the parameters acquired by the MCMC method enable the uncertainty of the parameters to be expressed in probability distributions rather than in confidence intervals. The final result proposes an initial CI of the 10 V output taps in the Zener devices without any calibration record of 8.8 months with a 0.91-month standard deviation for 90% of the measurement reliability target (MRT) and a 16 μV tolerance limit.