Neural network classifier for hyperspectral images of skin pathologies

This paper describes the use and results of a neural network classifier trained on a set of hyperspectral images of benign and malignant neoplasms. The analysis is carried out on 2D images extruded from hyperspectral data. The ranges of wavelengths at which the research is carried out is represented by the intervals 530–570 nm and 600–606 nm, which is caused by the assumption that the analysis of the entire spectral range is redundant and the prospect of saving resources. Melanoma, basal cell carcinoma (BCC), nevus and papilloma are accepted as primary classes, as the most dangerous, most common and non-malignant types of neoplasms, respectively. The neural network classifier is based on a three-block VGG network. With a training set included 1944 images, the classification accuracy for 4 types of samples was 92%.

Planar Modulated Reactance Surfaces for Endfire Antenna Applications

Modulated reactance synthesis for planar impenetrable electromagnetic surfaces for endfire radiation characteristics is presented. It is based on aperture field synthesis over the entire spectral range, where the desired radiation pattern is prescribed by a traveling-wave current over the aperture. Carefully constructed auxiliary waves in the evanescent spectrum are added and the total aperture fields are optimized such that the entire aperture surface becomes pointwise reactive. The optimized aperture fields define the modulated surface reactance that realizes the desired pattern when excited by a feed surface wave. The reactance distribution may be realized as modulated metasurfaces.

Effect of polyoxymethylene (POM-H Delrin) off-gassing within the Pandora head sensor on direct-sun and multi-axis formaldehyde column measurements in 2016–2019

Analysis of formaldehyde measurements by the Pandora spectrometer systems between 2016 and 2019 suggested that there was a temperature-dependent process inside the Pandora head sensor that emitted formaldehyde. Some parts in the head sensor were manufactured from the thermal plastic polyoxymethylene homopolymer (E.I. Du Pont de Nemour &amp; Co., USA; POM-H Delrin®) and were responsible for formaldehyde production. Laboratory analysis of the four Pandora head sensors showed that internal formaldehyde production had exponential temperature dependence with a damping coefficient of 0.0911±0.0024 ∘C−1 and the exponential function amplitude ranging from 0.0041 to 0.049 DU. No apparent dependency on the head sensor age and heating and cooling rates was detected. The total amount of formaldehyde internally generated by the POM-H Delrin components and contributing to the direct-sun measurements were estimated based on the head sensor temperature and solar zenith angle of the measurements. Measurements in winter, during colder (< 10 ∘C) days in general, and at high solar zenith angles (> 75∘) were minimally impacted. Measurements during hot days (> 28 ∘C) and small solar zenith angles had up to 1 DU (2.69×1016 molec. cm−2) contribution from POM-H Delrin parts. Multi-axis differential slant column densities were minimally impacted (<0.01 DU) due to the reference spectrum being collected within a short time period with a small difference in head sensor temperature. Three new POM-H Delrin free Pandora head sensors (manufactured in summer 2019) were evaluated for temperature-dependent attenuation across the entire spectral range (300 to 530 nm). No formaldehyde absorption or any other absorption above the instrumental noise was observed across the entire spectral range.

Схема VLS-монохроматора высокого разрешения для синхротронного излучения

A high-resolution monochromator with a broad spectral range of 125 – 4200 Angstrem is designed for the measuring beamline for the projected synchrotron radiation source "SKIF" (Novosibirsk). The optical configuration of the monochromator comprises a grazing-incidence concave mirror, a plane VLS grating, and an exit slit. It is planned to use two replaceable VLS gratings with central line frequencies of 600 mm-1 and 150 mm-1 intended for subranges of 125 – 1000 Angstrem and 900 – 4200 Angstrem , respectively. Wavelength tuning in each of the two subranges is effected by only the rotation of the VLS-gratings. Due to the proper choice of p_1 VLS-grating coefficients, the focal distance varies only slightly over the entire spectral range, and the p_2 VLS-grating coefficients are used to suppress the aberrations of the mirror and the gratings. The resolving power of the configuration obtained by numerical ray tracing exceeds 1000 in the 125 – 1000 Angstrem range and 2000 in the 900 – 4200 Angstrem range.

Non-invasive real-time imaging of reactive oxygen species (ROS) using multispectral auto-fluorescence imaging technique: a novel tool for redox biology

Detecting reactive oxygen species (ROS) that play a critical role as redox modulators and signalling molecules in biological systems currently requires invasive methods such as ROS - specific indicators for imaging and quantification. We developed a non-invasive, real-time, label-free imaging technique for assessing the level of ROS in live cells and thawed cryopreserved tissues that is compatible with in-vivo imaging. The technique is based on autofluorescence multispectral imaging (AFMI) carried out in an adapted fluorescence microscope with an expanded number of spectral channels spanning specific excitation (365 nm-495 nm) and emission (420 nm-700 nm) wavelength ranges. We established a strong quantitative correlation between the spectral information obtained from AFMI and the level of ROS obtained from CellROX staining. The results were obtained in several cell types (HeLa, PANC1 and mesenchymal stem cells) and in live kidney tissue. Additioanly, two spectral regimes were considered: with and without UV excitation (wavelengths > 400 nm); the latter being suitable for UV-sensitive systems such as the eye. Data were analyzed by linear regression combined with an optimization method of swarm intelligence. This allowed the calibration of AFMI signals to the level of ROS with excellent correlation (R= 0.84, p=0.00) in the entire spectral range and very good correlation (R= 0.78, p=0.00) in the limited, UV-free spectral range. We also developed a strong classifier which allowed us to distinguish moderate and high levels of ROS in these two regimes (AUC= 0.91 in the entire spectral range and AUC = 0.78 for UV-free imaging). These results indicate that ROS in cells and tissues can be imaged non-invasively, which opens the way to future clinical applications in conditions where reactive oxygen species are known to contribute to progressive disease such as in ophthalmology, diabetes, kidney disease, cancer and neurodegenerative diseases.

Electrochromic Properties of Polycrystalline Nb2O5 Thin Films with Mg2+ Ions

ABSTRACTSol-gel derived Nb2O5 thin films crystallize to a stable hexagonal phase on annealing at 600°C in air. These films have been intercalated with Mg2+ ions for the first time and the structural and the optical changes on intercalation have been reported. Films were intercalated and deintercalated with Mg2+ ions in galvanostatic mode. Mg intercalated films show about 35% transmittance variations in the entire spectral range. The FTIR studies show the formation of Mg-O-Nb bonds along with the formation of Nb-OH and Mg-O bonds. Small quantities of water is adsorbed during intercalation resulting in the formation of Mg(OH)2. The coloration is completely reversible on deintercalation. Formation of MgNb2O6 phase is seen on intercalation with 1M concentration of the electrolyte, which is found to be 'x' dependent, where ‘x’ is the ratio of the intercalated ions to the Nb atoms. 0.1 M electrolyte does not show the formation of this phase.

Determining Acid Equilibrium Constants by Means of Chromatic Parameters

A method has been developed for the determination of acid-base equilibrium constants, which is applicable to compounds that absorb in the visible. The tristimulus (X, Y, Z) and the colorimetric coordinate values ( L, a, b) of the chromatic space CIELAB 1976 are calculated by means of the transmittances of the entire spectral range. The curves, in the a,b plane, of chromatic differences vs. pH intersect at a pH value agreeing with the p Ka; this configuration occurs because a chromatic equilibrium of both species takes place at this point, which corresponds to the chemical equilibrium. With this method, the acidity constants are found easily and quickly, and they yield very good results. The validity of the method has been tested with the acid-base indicator bromophenol blue, obtaining p Ka= 3.943 at 25 °C; this result is compared with those obtained through the usual spectrophotometric methods. Also, thermodynamic magnitudes obtained from p Ka values at different temperatures from 20 to 70 °C have been determined, resulting in Δ H0 = -(13.93 ± 0.88) kj mol−1 Δ S0 = -(122.6 ± 2.8) J K−1 mol−1.