The history of the modernization of the national standard for the unit of luminous intensity in Russia is presented: from the establishment of the first state light standard in 1925 at Main Chamber of Weights and Measures (today – the D. I. Mendeleev Institute for Metrology) under the leadership of P. I. Tikhodeev to its current version – the State primary standard for units of luminous intensity and luminous fl ux GET 5-2024. As a result of the latest modernization, the GET 5-2024 now includes newly developed and manufactured by All-Russian Research Institute for Optical and Physical Measurements standard facilities, based on the latest research findings. For the first time in global practice, the unit of luminous intensity – the candela – is reproduced in GET 5-2024 using a high-temperature blackbody model operating at a fixed thermodynamic temperature of 2856.67 K, corresponding to the phase transition melting point of the molybdenum-carbon compound δ(MoC)-C. This approach has enabled an expanded uncertainty in the reproduction of the candela not exceeding 0.2 % at the level of 388.52 cd (with a coverage factor 2). Additionally, the use of a variable-temperature blackbody model allows for the reproduction of luminous intensity in the range from 1 to 20000 cd, with an expanded uncertainty not exceeding 0.24 % (with a coverage factor 2). The unit of total luminous fl ux – the lumen – is reproduced using a goniometric method with a specially developed goniophotometer. The reproduction range for luminous fl ux is from 1 to 3500 lm, with an expanded uncertainty of 0.22–0.28 % (with a coverage factor 2). Thus, the modernization of GET 5-2024 has extended the reproduction ranges of the units of luminous intensity and luminous fl ux and improved the accuracy of their realization. The improved GET 5-2024 allows the reproduction of the unit of luminous intensity in accordance with the recommendations of the International Committee of Weights and Measures, which ensures international compatibility of the results of scientific and applied measurements, their accuracy, and also contributes to improving the quality of industrial products, increasing transport safety, etc.

The condition of applicability of the “Guide to the Expression of Measurement Uncertainty” (GUM), a translation into Russian in 1999 of the international document on metrology, is considered. The GUM is devoted to a new approach for domestic metrology at that time to assessing the accuracy of solving measurement problems using the indirect measurement method. The condition of applicability requires the negligible smallness of any uncertainties caused by the incompleteness of determining the quantities sought in the problem compared to the required accuracy of the result, although the translation states that “this is not always practical”. However, the VIM-3 International Dictionary of Metrology Terms introduced the term “defi nition uncertainty” for uncertainties of this kind and pointed out that in the GUM, defi nitional uncertainty is considered as negligible compared to other components of measurement uncertainty. In practice, there are numerous cases of using the GUM without checking mathematical models for inadequacy. The situation is aggravated by the fact that this manual does not contain a quantitative defi nition of the incompleteness of the mathematical model of the measuring object, although the need for statistical verifi cation of models for inadequacy is mentioned. Violation of the condition of applicability of the GUM can be eliminated by a cross-examination scheme.

The practical application of the Kalman filter in many technical applications leads to the divergence of the evaluation process. The existing methods of reducing estimation error and increasing the stability of the filtering procedure are focused only on assessing the state of specific systems. The analysis of the possibility of their generalized use is hampered by the nonlinear evolution of the a posteriori covariance matrix, which directly affects the convergence of the estimation error. To solve the problem of increasing the accuracy and stability of the filtration process, the article considers a stochastic estimation algorithm using the estimation vector at the output of the Kalman filter as an observer of the state vector of a dynamic system. Such use leads to an adaptive change in the intensity of measurement interference in the new filtering circuit, which reduces the frequency and amplitude of vibrations of the elements of the a posteriori covariance matrix and significantly increases the accuracy of the current estimate. The results of numerical modeling are presented, illustrating the effectiveness of the proposed approach. The proposed stochastic filtering method can be applied to a broad class of problems, including measurement processing, navigation, seismology, space research, and other areas.

This study presents a novel approach for the estimation and correction of geometric errors in twodimensional motion systems of coordinate measuring machines using the principles of differential geometry. Geometric errors are understood as the result of coordinate transformations between machine-measured (digital) and actual coordinates, described by the Jacobian matrix. The proposed method involves determining the components of the Jacobian matrix based on positional errors, deviations from straightness, angular deviations, and deviations from the mutual perpendicularity of the axes, measured using a Renishaw XL-80 laser interferometer. The correction model integrates error maps, numerical derivatives and integrals, and a moving average filter to minimize random noise. This method was experimentally validated on a computerized universal measuring microscope (UIM-21). The results of the end measure of length measurements before and after correction revealed significant reductions in data dispersion and the elimination of outliers, confirming improved measurement reliability. The approach offers practical advantages, including reduced calibration time, lower costs, and adaptability to various coordinate measuring machines configurations. The developed model enhances in-plane measurement accuracy and provides a foundation for applying differential geometry-based corrections to more complex multi-axis measuring systems.

In connection with the development and implementation of modern optoelectronic technologies in various branches of medicine, it is important to ensure high-quality functioning of devices for non-invasive spectrophotometric diagnostics of physiological parameters under the infl uence of such specific external factors as light noise of natural and artificial light sources. A mathematical model of fixed-frequency light noise is presented and it is shown that such noise is an additive interference in relation to the useful photoplethysmographic signal of the pulse oximeter channel. It is shown that when using photoplethysmographic methods for studying oxygen status parameters, the intensity of optical radiation transmitted through biological tissue depends on the level of arterial blood oxygen saturation. A mathematical model of the photoplethysmographic signal has been developed that allows taking into account the pulse wave parameters – the frequencies of the first and second harmonics of arterial blood pulsation, respiratory contractions. The light noise level is normalized to the photoplethysmographic signal level using the signal-to-noise ratio. It has been found that at a signal-to-noise ratio of 10; 5; 1, the ratios of the constant and variable components of the photoplethysmographic signal change on average by 6.7, 11.4, 15.7 %, respectively, compared to the case of no additive interference. The effect of light noise of various levels on the quality of fractional blood saturation level assessment was investigated and it was found that with a signal/noise ratio of 10; 5; 1, the relative error of this assessment is 3.676; 6.115; 8.077 %, respectively. A physical experiment was conducted with the participation of 30 subjects to determine the effect of illumination on the quality of fractional blood saturation level assessment by a multiwave pulse oximeter. The experimental data confirmed the results of model studies for a signal/noise ratio of 10 and 5. The results obtained can be used in the design and development of noninvasive spectrophotometric diagnostic devices and assessment of their performance under conditions of destabilizing factors.

The article considers an important practical problem that allows expanding the information on the laser beam parameters required for manufacturing and certification of laser sources. The only existing standardized numerical characteristic, the М 2 measure (GOST R ISO 11146-1-2008 “Lasers and laser installations (systems). Methods for measuring widths, divergence angles and propagation coefficients of laser beams”), which determines the quality of a laser beam, allows estimating the degree of similarity of the measured spatial distribution of the beam intensity only with the spatial distribution of the Gaussian intensity in the measurement plane. An alternative measure of similarity of the measured spatial distribution of the laser beam amplitude with a uniform distribution in the emitter plane or a spatial distribution of intensity with an arbitrary distribution in the measurement plane has been developed. It has been shown that the alternative measure of similarity when located in the emitter plane coincides with the aberration factor determining the source with the greatest axial luminous intensity. The proposed measure is universal and has a wider application than the М 2 measure, since it is associated with the characteristic of the field distribution homogeneity, the generalized area and the generalized diameter of the laser beam, which is an alternative to the beam diameter determined by GOST R ISO 11146-1-2008.

The article presents a method for determining the optical transparency of polyimide films used in the manufacture of fl exible electronics devices by laser carbonization. Information about the optical transparency of polyimide films in the visible and near-infrared ranges of the spectrum allows you to choose the optimal mode of laser carbonization. Using a calibrated radiation source and small-sized high-resolution spectrometers, data on the intensity of transmitted radiation through polyimide films of various thicknesses at several thousand wavelengths in the visible and near-infrared spectral ranges were obtained. Two operating wavelengths of solid–state lasers were selected from the obtained data array: 694.3 nm (ruby laser) and 1064 nm (neodymium-doped yttrium aluminum garnet laser, Nd:YAG). The dependences of the transmission coefficients of polyimide films with a thickness of 100, 200 and 300 microns on these wavelengths are constructed. It is shown that similar dependences can be constructed for all types of lasers emitting in the specified spectral ranges. Knowledge of the transmission coefficient of polyimide at various wavelengths will help to more accurately investigate and understand the essence of the physico-chemical processes occurring in the material when exposed to laser radiation of a certain wavelength. The proposed method for determining the optical transparency of polyimide films can be used to find the transmission intensity of any translucent materials used in laser and other technologies.

The disadvantages of galvanically isolated converters that transmit information through an insulating barrier in digital or analog form are considered, such as the high cost of components or a conversion error of more than 1 %. Such galvanically isolated converters are necessary for the safe operation of equipment operating at voltages above 50 V. A galvanic analog signal separator has been developed that transmits information in analog form through an insulating barrier without transferring it (converting it) to digital form and has a conversion error of 0.22 % at rated voltage. This galvanic separator can be used as part of measuring devices such as converters, sensors, and analog signal transceivers without transferring information to digital form. A method of transmitting an analog information signal in the absence of an electrical connection is investigated, which makes it possible to reduce the error and increase the noise immunity of the converter.The circuit of the proposed galvanic analog signal separator is based on negative feedback, the circuit of which passes through a modulator, transformer and demodulator on the primary side. The signal from the output of the demodulator is sent to one of the two inputs of the error amplifier. The error amplifier adjusts the voltages at both inputs in strict accordance with each other, due to which the voltage at the output of the demodulator is exactly equal to the input voltage supplied to the other input of the error amplifier. The second demodulator, identical to the first one, is installed on the secondary side. The use of two demodulators made it possible to achieve accurate transmission of the analog signal from the primary side to the secondary side. A laboratory sample of a galvanic analog signal separator has been manufactured and tested. According to the test results, the expediency of using negative feedback has been confirmed: the relative conversion error has been reduced by three times compared to devices without feedback. The relative error of the conversion of the proposed device over the entire input voltage range was no more than 0.7 % and 0.22 % at the nominal input value. The device can be used as part of measuring equipment operating at high (more than 10 kV) voltages.

The manuscript discusses the challenges of metrological support for rapidly developing technologies, including electronics, radio vision, and security systems. To foster successful technological advancement, it is essential to expand the state standard base into a higher frequency range of 100–1000 GHz. This expansion is crucial for the verification and certification of devices and measuring instruments operating in the terahertz (millimeter) frequency range. Currently, the frequency range of the State Primary Standard for the unit of spectral power density of radio noise radiation, as defined in GET 21-2021, spans from 0.002 to 178.3 GHz. However, this frequency range is insufficient for the precise testing and certification of the high-precision devices and measuring instruments that are currently being developed. The manuscript presents the results of the development and study of the experimental sample of the primary standard of the unit of spectral power density of radio noise radiation in the frequency range of 220–300 GHz. The experimental sample includes a radiometer, a signal generator for the local oscillator channel, a low-temperature noise generator, a matched load, and a standard attenuator. The following characteristics of the experimental sample are achieved: the equivalent noise temperature of a low-temperature noise generator is from 103 K (220 Hz) to 120 K (300 GHz). The sensitivity of the comparator based on the radiometer is 0.86 K. The characteristics of the experimental sample are comparable with the characteristics of similar devices from the world's leading manufacturer, Radiometer Physics (Germany). The developed experimental sample can be used to calibrate low-noise receiving and amplifying devices of the terahertz range, which are finding increasing application in various fields of science and technology. An important area of application of the developed standard is also the verification of radiometers used in passive radar systems. Additionally, it is noteworthy that the developed radiometer (operating within 220–300 GHz) holds potential for scientific problems related to conducting radio astronomical terrestrial observations in the terahertz range, in particular in atmospheric transparency windows at wavelengths of 1.3 and 0.8 mm, where many spectral lines of atoms and molecules are concentrated.

Renal cell carcinoma is the most common form of kidney cancer (more than 90 % of all oncological pathologies of the kidney). At an early stage of development, renal cell carcinoma can be asymptomatic, and this significantly complicates its diagnosis. Commonly used methods for diagnosing renal cell carcinoma do not allow for timely detection of this disease at early stages, thus it is necessary to develop effective and non-invasive methods for its diagnosis using biological macromolecules detectable in blood – biomarkers of this type of cancer. Small nucleolar RNAs are of great interest as such biological macromolecules. In this study, a SiNW biosensor was designed and manufactured for the direct detection of small nucleolar RNA SNORA77 in the blood, associated with renal cell carcinoma. The key element of the SiNW biosensor developed is a nanowire chip based on “siliconon- insulator” structures. The chip is manufactured using a technology similar to Smart Cut, and contains an array of silicon nanowires with n-type conductivity, on whose surface DNA oligonucleotide probes are covalently immobilized. To ensure the specificity of the analysis, the nucleotide sequence of the immobilized DNA probes is complementary to the target sequence of the small nucleolar RNA SNORA77. Purified buffer solutions containing various concentrations of synthetic DNA oligonucleotides, whose sequence is similar to the target detectable sequence of SNORA77, have been analyzed. Using the SiNW biosensor developed, the detection limit of SNORA77 was determined to be approximately 10–17 M. The SiNW biosensor has allowed us to detect an elevated level of SNORA77 in a sample isolated from the blood plasma of a patient with confirmed diagnosis of renal cell carcinoma in comparison with that in a control sample isolated from the plasma of a patient with a non-oncologic disease. The results of the study will be useful for further development of early diagnostic systems for renal cell carcinoma.

External quality assessment, conducted in the form of interlaboratory comparisons, is traditionally a tool for verifying laboratory qualifications and confirming the level of measurement accuracy required or claimed by laboratories. The authors identified industry-specific measurement features in laboratory medicine and analyzed long-term participation in the external quality assessment system. Based on these data, the authors concluded that in the absence of appropriate standards, certified reference materials and reference methods for many analytes, the external quality assessment system for medical laboratories acquires a different meaning and becomes an indispensable tool for obtaining objective data on the reproducibility/ consistency of the results obtained in different laboratories, identifying biases in the measurement results of participating laboratories. In such circumstances, an external quality assessment confirms the qualification of a medical laboratory in using a specific analytical technique in combination with reference clinical information corresponding to this particular technique. The results obtained may be of interest to specialists working at the interface of metrology and clinical laboratory diagnostics, as well as manufacturers of medical devices for in vitro diagnostics and external quality assessment providers.

In measuring the isotopic composition of substances and materials using an inductively coupled plasma quadrupole mass spectrometer, the main source of bias in the measured isotopic ratios is the detector dead time. In this regard, an important step in the development of reference materials for isotopic composition is the determination and correction of the results for dead time. This work is devoted to the determination and study of the effect of dead time on the results of isotopic ratios in the study of the isotopic composition of copper and zinc solutions enriched in ⁶⁵Cu and ⁶⁸Zn isotopes. The study considers several methods for determining the dead time based on measurements of the isotopic ratios of ⁶³Cu/⁶⁵Cu, ⁶⁴Zn/⁶⁸Zn, ⁶⁶Zn/⁶⁸Zn, ⁶⁷Zn/⁶⁸Zn, ⁷⁰Zn/⁶⁸Zn in solutions with different mass fractions of copper and zinc, as well as a method based on comparing the pulse and analog detector signal on an inductively coupled plasma quadrupole mass spectrometer. The uncertainties of dead time measurements by different methods are calculated. In the course of the work, optimal methods for determining the dead time are found and selected for further research. The detector dead time is (76±4) ns for enriched ⁶⁵Cu solution and (42±4) ns for enriched ⁶⁸Zn solution.

The effect of the density of wheat grain on the accuracy of measuring its moisture content by the ultra-high frequency method is considered. The method is based on amplitude dielectric metrology, in which the attenuation of an electromagnetic wave passing through the grain is analyzed. A single-parameter moisture meter operating at ultra-high frequencies and intended for use in grain processing production has been developed. The structural diagram of the moisture meter and the principles of its operation are presented The device's design incorporates a mathematical model that takes into account the electrophysical properties of grain material and its interaction with ultra-high frequency radiation at a fixed frequency. A prototype of the device has been manufactured and tested in real production conditions. Grain with different densities, such as 87, 116, and 145 kg/m3, has been investigated. It has been experimentally established that as the grain density decreases, the relative error in measuring its moisture content increases, especially at high moisture contents exceeding 14 %. At a moisture content of 18 % and a grain density of 145 and 87 kg/m3, the relative error in measurement was 9.8 % and 44.7 %, respectively. The calculated partial derivatives of the signal amplitude with respect to density are significantly higher in conditions of high humidity, which indicates a strong dependence of the moisture meter readings on the density of the material in these conditions: even a small change in density can significantly increase the measurement error at high humidity. Graphs of the moisture meter signal amplitude dependence on humidity at different values of density and the results of regression analysis confirming the need to take into account the density during the instrument calibration are presented. The absolute and relative errors of moisture measurement are estimated depending on the sample density. The results of the studies confirm the effectiveness of the ultra-high frequency method of rapid moisture assessment and the developed moisture meter, provided that the infl uence of density is corrected.