Monte Carlo Analysis of Optical Interactions in Reflectance and Transmittance Finger Photoplethysmography

Photoplethysmography (PPG) is a non-invasive photometric technique that measures the volume changes in arterial blood. Recent studies have reported limitations in developing and optimising PPG-based sensing technologies due to unavailability of the fundamental information such as PPG-pathlength and penetration depth in a certain region of interest (ROI) in the human body. In this paper, a robust computational model of a dual wavelength PPG system was developed using Monte Carlo technique. A three-dimensional heterogeneous volume of a specific ROI (i.e., human finger) was exposed at the red (660 nm) and infrared (940 nm) wavelengths in the reflectance and transmittance modalities of PPG. The optical interactions with the individual pulsatile and non-pulsatile tissue-components were demonstrated and the optical parameters (e.g., pathlength, penetration depth, absorbance, reflectance and transmittance) were investigated. Results optimised the source-detector separation for a reflectance finger-PPG sensor. The analysis with the recorded absorbance, reflectance and transmittance confirmed the maximum and minimum impact of the dermis and bone tissue-layers, respectively, in the formation of a PPG signal. The results presented in the paper provide the necessary information to develop PPG-based transcutaneous sensors and to understand the origin of the ac and dc components of the PPG signal

Heat capacity of tantalum in the normal and superconducting states: Identification of the contributions

Tantalum is used as an example to show that a statistical thermodynamic approach applied in the regions of the superconducting and normal states of the metal can estimate the reliable thermodynamic parameters that are related to the heat capacity of the metal (electronic heat capacity coefficient ζ, Debye temperature θD) and can estimate their errors statistically. The calculated heat capacity and the determined low-temperature values of the parameters agree satisfactorily with the data of self-consistent thermodynamic calculations performed in an extended temperature range. © 2013 Pleiades Publishing, Ltd

Plum pudding random medium model of biological tissue toward remote microscopy from spectroscopic light scattering

Biological tissue has a complex structure and exhibits rich spectroscopic behavior. There is \emph{no} tissue model up to now able to account for the observed spectroscopy of tissue light scattering and its anisotropy. Here we present, \emph{for the first time}, a plum pudding random medium (PPRM) model for biological tissue which succinctly describes tissue as a superposition of distinctive scattering structures (plum) embedded inside a fractal continuous medium of background refractive index fluctuation (pudding). PPRM faithfully reproduces the wavelength dependence of tissue light scattering and attributes the "anomalous" trend in the anisotropy to the plum and the powerlaw dependence of the reduced scattering coefficient to the fractal scattering pudding. Most importantly, PPRM opens up a novel venue of quantifying the tissue architecture and microscopic structures on average from macroscopic probing of the bulk with scattered light alone without tissue excision. We demonstrate this potential by visualizing the fine microscopic structural alterations in breast tissue (adipose, glandular, fibrocystic, fibroadenoma, and ductal carcinoma) deduced from noncontact spectroscopic measurement

Mesoporous Silica and Composite Nanostructures for Theranostics

We discus methods for fabrication of silica and composite nanoparticles, which can be used in various biomedical applications. The most promising types of such nanostructures are hollow silica nanosheres, sil-ica coated plasmon-resonant nanoparticles (gold nanorods and gold-silver nanocages) and nanorattles. Mesoporous silica shell can be doped by desirable targeting molecules. Here we present the results of for-mation of nanocomposites composed of gold nanorods and double-layer silica shell. The secondary mesopo-rous silica shell is doped with a photosensitizer (hematoporphyrine in our case). We demonstate some of promising theranostics applications of these nanocomposites for bioimaging and in vivo therapy of tumors. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3548

Onset of magnetism in B2 transition metals aluminides

Ab initio calculation results for the electronic structure of disordered bcc Fe(x)Al(1-x) (0.4<x<0.75), Co(x)Al(1-x) and Ni(x)Al(1-x) (x=0.4; 0.5; 0.6) alloys near the 1:1 stoichiometry, as well as of the ordered B2 (FeAl, CoAl, NiAl) phases with point defects are presented. The calculations were performed using the coherent potential approximation within the Korringa-Kohn-Rostoker method (KKR-CPA) for the disordered case and the tight-binding linear muffin-tin orbital (TB-LMTO) method for the intermetallic compounds. We studied in particular the onset of magnetism in Fe-Al and Co-Al systems as a function of the defect structure. We found the appearance of large local magnetic moments associated with the transition metal (TM) antisite defect in FeAl and CoAl compounds, in agreement with the experimental findings. Moreover, we found that any vacancies on both sublattices enhance the magnetic moments via reducing the charge transfer to a TM atom. Disordered Fe-Al alloys are ferromagnetically ordered for the whole range of composition studied, whereas Co-Al becomes magnetic only for Co concentration >0.5.Comment: 11 pages with 9 embedded postscript figures, to be published in Phys.Rev.

Shedding light on the variability of optical skin properties: finding a path towards more accurate prediction of light propagation in human cutaneous compartments

YesFinding a path towards a more accurate prediction of light propagation in human skin remains an aspiration of biomedical scientists working on cutaneous applications both for diagnostic and therapeutic reasons. The objective of this study was to investigate variability of the optical properties of human skin compartments reported in literature, to explore the underlying rational of this variability and to propose a dataset of values, to better represent an in vivo case and recommend a solution towards a more accurate prediction of light propagation through cutaneous compartments. To achieve this, we undertook a novel, logical yet simple approach. We first reviewed scientific articles published between 1981 and 2013 that reported on skin optical properties, to reveal the spread in the reported quantitative values. We found variations of up to 100-fold. Then we extracted the most trust-worthy datasets guided by a rule that the spectral properties should reflect the specific biochemical composition of each of the skin layers. This resulted in the narrowing of the spread in the calculated photon densities to 6-fold. We conclude with a recommendation to use the identified most robust datasets when estimating light propagation in human skin using Monte Carlo simulations. Alternatively, otherwise follow our proposed strategy to screen any new datasets to determine their biological relevance.European Marie-Curie Actions Programme, Grant agreement no. 60788

Sensitive detection of voltage transients using differential intensity surface plasmon resonance system

This paper describes theoretical and experimental study of the fundamentals of using surface plasmon resonance (SPR) for label-free detection of voltage. Plasmonic voltage sensing relies on the capacitive properties of metal-electrolyte interface that are governed by electrostatic interactions between charge carriers in both phases. Externally-applied voltage leads to changes in the free electron density in the surface of the metal, shifting the SPR position. The study shows the effects of the applied voltage on the shape of the SPR curve. It also provides a comparison between the theoretical and experimental response to the applied voltage. The response is presented in a universal term that can be used to assess the voltage sensitivity of different SPR instruments. Finally, it demonstrates the capacity of the SPR system in resolving dynamic voltage signals; a detection limit of 10mV with a temporal resolution of 5ms is achievable. These findings pave the way for the use of SPR systems in the detection of electrical activity of biological cells

Utilization of ferrochrome slag in concrete production

Ferrochrome slag is waste resulted from the manufacture process of ligature melting. It is a porous material of dark grey-green colour with 2530 kg/m3 density and the open pores size from 1mm to 5 mm. After crushing crushed slag possesses the following characteristics or properties, namely: the least grain coarseness is 20 mm, the largest one is 120mm, the needle and plane grain content is 25.5%, so it refers to ordinary group of crushed stone, its crushability grade is M800, attrition grade AI and frostproofness is F25. Screenings or riddlings obtained by crushing and fractioning of slag possess gradation factor 2.9 and it refers it coarse sand group of class II. Concrete mixes have been investigated by using granite aggregates and ferrochrome ones. It is determined that mixes containing ferrochrome aggregate are stiffer than the traditional ones. In this case strength characteristics of the experimental concretes are 1.7 times higher than those of the traditional concretes. When evaluating approximate cement consumption for concrete made of ferrochrome slag aggregates it was established that such concrete possesses strength of B30 class, but by using granite aggregate in the concrete mix result in strength of B20 class. © Published under licence by IOP Publishing Ltd

Impact of tracer particles on the electrolytic growth of hydrogen bubbles

The thermocapillary effect at gas bubbles growing at micro-electrodes seems well understood. However, the interfacial flow measured in the upper bubble part decays faster than found in first simulations by Massing et al. ["Thermocapillary convection during hydrogen evolution at microelectrodes,"Electrochim. Acta 297, 929 (2019)]. Recently, Meulenbroek et al. attributed the origin of the difference to the influence of surfactants being present in the electrolyte ["Competing Marangoni effects from a stagnant cap on the interface of a hydrogen bubble attached to a microelectrode,"Electrochim. Acta 385, 138298 (2021)]. Surprisingly, the presence of tracer particles added to the electrolyte for measuring its flow was not yet considered. Our recent experiments reveal that varying the small amount of tracer particles added influences the bubble shape, its dynamics, and also the electrolyte flow nearby. We therefore present a model to describe the particle attraction to and the particle dynamics at the bubble interface, which allows us to quantify the impact. Corresponding simulations are validated against measurements for different bulk particle concentrations and show a good agreement of the tangential velocity profile at the bubble interface caused by thermo- and solutocapillary effects. Depending on the particle concentration, parts of the upper bubble interface are found to become stagnant. The results allow a deeper insight into the complex phenomena of electrolytic gas evolution and further put attention to a careful application of particle-based measurement techniques in gas-liquid systems.</p

Glycerol effects on optical, weight and geometrical properties of skin tissue

Complex study of glycerol e®ects on the skin tissue was performed. The change in optical, weight and geometrical parameters of the rat skin under the action of the glycerol solutions was studied ex vivo. Possible mechanisms of the skin optical clearing under the action of glycerol solutions of di®erent concentrations were discussed. The results can be helpful for re¯nement of models developed to evaluate the e®ective di®usion coe±cients of glycerol in tissues