85 research outputs found
Influence of probe pressure on diffuse reflectance spectra of human skin measured in vivo
Mechanical pressure superficially applied on the human skin surface by a fiber-optic probe influences the spatial distribution of blood within the cutaneous tissues. Upon gradual load of weight on the probe, a stepwise increase in the skin reflectance spectra is observed. The decrease in the load follows the similar inverse staircase-like tendency. The observed stepwise reflectance spectra changes are due to, respectively, sequential extrusion of blood from the topical cutaneous vascular beds and their filling afterward. The obtained results are confirmed by Monte Carlo modeling. This implies that pressure-induced influence during the human skin diffuse reflectance spectra measurements in vivo should be taken into consideration, in particular, in the rapidly developing area of wearable gadgets for real-time monitoring of various human body parameters
Photoacoustic imaging in biomedicine and life sciences
Photo-acoustic imaging, also known as opto-acoustic imaging, has become a widely popular modality for biomedical applications. This hybrid technique possesses the advantages of high optical contrast and high ultrasonic resolution. Due to the distinct optical absorption properties of tissue compartments and main chromophores, photo-acoustics is able to non-invasively observe structural and functional variations within biological tissues including oxygenation and deoxygenation, blood vessels and spatial melanin distribution. The detection of acoustic waves produced by a pulsed laser source yields a high scaling range, from organ level photo-acoustic tomography to sub-cellular or even molecular imaging. This review discusses significant novel technical solutions utilising photo-acoustics and their applications in the fields of biomedicine and life sciences
Monitoring of temperature-mediated phase transitions of adipose tissue by combined optical coherence tomography and Abbe refractometry
Observation of temperature-mediated phase transitions between lipid components of the adipose tissues has been performed by combined use of the Abbe refractometry and optical coherence tomography. The phase transitions of the lipid components were clearly observed in the range of temperatures from 24Β°C to 60Β°C, and assessed by quantitatively monitoring the changes of the refractive index of 1-to 2-mm-thick porcine fat tissue slices. The developed approach has a great potential as an alternative method for obtaining accurate information on the processes occurring during thermal lipolysis
Nanoparticle-free tissue-mimicking phantoms with intrinsic scattering
We present an alternative to the conventional approach, phantoms without scattering nanoparticles, where scattering is achieved by the material itself: spherical cavities trapped in a silicone matrix. We describe the properties and fabrication of novel optical phantoms based on a silicone elastomer polydimethylsiloxane (PDMS) and glycerol mixture. Optical properties (absorption coefficient Β΅a, reduced scattering coefficient Β΅s', and anisotropy factor g) of the fabricated phantoms were retrieved from spectrophotometric measurements (in the 400β1100 nm wavelength range) using the inverse adding-doubling method. The internal structure of the phantoms was studied under a scanning electron microscope, and the chemical composition was assessed by Raman spectroscopy. Composition of the phantom material is reported along with the full characterization of the produced phantoms and ways to control their parameters
Luminescent upconversion nanoparticles evaluating temperature-induced stress experienced by aquatic organisms due to environmental variations
Growing anthropogenic activities are significantly influencing the environment and especially aquatic ecosystems. Therefore, there is an increasing demand to develop techniques for monitoring and assessing freshwater habitats changes so that interventions can prevent irrevocable damage. We explore an approach for screening the temperature-induced stress experienced by aquatic organisms due to environmental variations. Luminescent spectra of upconversion [Y2O3: Yb, Er] particles embedded within Caridina multidentata shrimps are measured, while ambient temperature gradient is inducing stress conditions. The inverse linear dependence of logarithmic ratio of the luminescence intensity provides an effective means for temperature evaluation inside aquatic species in vivo. The measured luminescence shows high photostability on the background of complete absence of biotissues autofluorescence, as well as no obscuration of the luminescence signal from upconversion particles. Current approach of hybrid sensing has a great potential for monitoring of variations in aquatic ecosystems driven by climate changes and pollution
Coherent radiation from neutral molecules moving above a grating
We predict and study the quantum-electrodynamical effect of parametric
self-induced excitation of a molecule moving above the dielectric or conducting
medium with periodic grating. In this case the radiation reaction force
modulates the molecular transition frequency which results in a parametric
instability of dipole oscillations even from the level of quantum or thermal
fluctuations. The present mechanism of instability of electrically neutral
molecules is different from that of the well-known Smith-Purcell and transition
radiation in which a moving charge and its oscillating image create an
oscillating dipole.
We show that parametrically excited molecular bunches can produce an easily
detectable coherent radiation flux of up to a microwatt.Comment: 4 page
Speckle dynamics under ergodicity breaking
Laser speckle contrast imaging (LSCI) is a well-known and versatile approach for the non-invasive visualization of flows and microcirculation localized in turbid scattering media, including biological tissues. In most conventional implementations of LSCI the ergodic regime is typically assumed valid. However, most composite turbid scattering media, especially biological tissues, are non-ergodic, containing a mixture of dynamic and static centers of light scattering. In the current study, we examined the speckle contrast in different dynamic conditions with the aim of assessing limitations in the quantitative interpretation of speckle contrast images. Based on a simple phenomenological approach, we introduced a coefficient of speckle dynamics to quantitatively assess the ratio of the dynamic part of a scattering medium to the static one. The introduced coefficient allows one to distinguish real changes in motion from the mere appearance of static components in the field of view. As examples of systems with static/dynamic transitions, thawing and heating of Intralipid samples were studied by the LSCI approach
Spread Layers of Lysozyme Microgel at Liquid Surface
The spread layers of lysozyme (LYS) microgel particles were studied by surface dilational rheology, infrared reflectionβabsorption spectra, Brewster angle microscopy, atomic force microscopy, and scanning electron microscopy. It is shown that the properties of LYS microgel layers differ significantly from those of Γ-lactoglobulin (BLG) microgel layers. In the latter case, the spread protein layer is mainly a monolayer, and the interactions between particles lead to the increase in the dynamic surface elasticity by up to 140 mN/m. In contrast, the dynamic elasticity of the LYS microgel layer does not exceed the values for pure protein layers. The compression isotherms also do not exhibit specific features of the layer collapse that are characteristic for the layers of BLG aggregates. LYS aggregates form trough three-dimensional clusters directly during the spreading process, and protein spherulites do not spread further along the interface. As a result, the liquid surface contains large, almost empty regions and some patches of high local concentration of the microgel particles
Promotion Effect of Alkali Metal Hydroxides on Polymer-Stabilized Pd Nanoparticles for Selective Hydrogenation of CβC Triple Bonds in Alkynols
Postimpregnation of Pd nanoparticles (NPs) stabilized within hyper-cross-linked polystyrene with sodium or potassium hydroxides of optimal concentration was found to significantly increase the catalytic activity for the partial hydrogenation of the CβC triple bond in 2-methyl-3-butyn-2-ol at ambient hydrogen pressure. The alkali metal hydroxide accelerates the transformation of the residual Pd(II) salt into Pd(0) NPs and diminishes the reaction induction period. In addition, the selectivity to the desired 2-methyl-3-buten-2-ol increases with the K- and Na-doped catalysts from 97.0 up to 99.5%. This effect was assigned to interactions of the alkali metal ions with the Pd NPs surfaces resulting in the sitesβ separation and a change of reactants adsorption
Π‘Π΅ΠΏΡΠΈΡΠ΅ΡΠΊΠΈΠΉ ΡΠΎΠΊ Ρ Π²Π·ΡΠΎΡΠ»ΡΡ : ΠΊΠ»ΠΈΠ½ΠΈΡΠ΅ΡΠΊΠΈΠ΅ ΡΠ΅ΠΊΠΎΠΌΠ΅Π½Π΄Π°ΡΠΈΠΈ ΠΠ±ΡΠ΅ΡΠΎΡΡΠΈΠΉΡΠΊΠΎΠΉ ΠΎΠ±ΡΠ΅ΡΡΠ²Π΅Π½Π½ΠΎΠΉ ΠΎΡΠ³Π°Π½ΠΈΠ·Π°ΡΠΈΠΈ Β«Π€Π΅Π΄Π΅ΡΠ°ΡΠΈΡ Π°Π½Π΅ΡΡΠ΅Π·ΠΈΠΎΠ»ΠΎΠ³ΠΎΠ² ΠΈ ΡΠ΅Π°Π½ΠΈΠΌΠ°ΡΠΎΠ»ΠΎΠ³ΠΎΠ²Β»
Π ΡΡΠ°ΡΡΠ΅ ΠΏΡΠ΅Π΄ΡΡΠ°Π²Π»Π΅Π½Ρ ΠΎΡΠ½ΠΎΠ²Π½ΡΠ΅ ΠΏΠΎΠ»ΠΎΠΆΠ΅Π½ΠΈΡ ΠΊΠ»ΠΈΠ½ΠΈΡΠ΅ΡΠΊΠΈΡ
ΡΠ΅ΠΊΠΎΠΌΠ΅Π½Π΄Π°ΡΠΈΠΉ ΠΏΠΎ ΡΠ΅ΠΏΡΠΈΡΠ΅ΡΠΊΠΎΠΌΡ ΡΠΎΠΊΡ ΡΒ Π²Π·ΡΠΎΡΠ»ΡΡ
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ΠΠ±ΡΠ΅ΡΠΎΡΡΠΈΠΉΡΠΊΠΎΠΉ ΠΎΠ±ΡΠ΅ΡΡΠ²Π΅Π½Π½ΠΎΠΉ ΠΎΡΠ³Π°Π½ΠΈΠ·Π°ΡΠΈΠ΅ΠΉ Β«Π€Π΅Π΄Π΅ΡΠ°ΡΠΈΡ Π°Π½Π΅ΡΡΠ΅Π·ΠΈΠΎΠ»ΠΎΠ³ΠΎΠ² ΠΈΒ ΡΠ΅Π°Π½ΠΈΠΌΠ°ΡΠΎΠ»ΠΎΠ³ΠΎΠ²Β» Π²Β 2023Β Π³. ΠΠΊΡΡΠ°Π»ΡΠ½ΠΎΡΡΡ ΠΏΡΠΎΠ±Π»Π΅ΠΌΡ ΡΠ²ΡΠ·Π°Π½Π° ΡΠΎ Π·Π½Π°ΡΠΈΡΠ΅Π»ΡΠ½ΠΎΠΉ ΡΠ°ΡΠΏΡΠΎΡΡΡΠ°Π½Π΅Π½Π½ΠΎΡΡΡΡ ΠΈΒ Π²ΡΡΠΎΠΊΠΈΠΌΠΈ ΠΏΠΎΠΊΠ°Π·Π°ΡΠ΅Π»ΡΠΌΠΈ Π»Π΅ΡΠ°Π»ΡΠ½ΠΎΡΡΠΈ ΠΏΡΠΈ ΡΠ΅ΠΏΡΠΈΡΠ΅ΡΠΊΠΎΠΌ ΡΠΎΠΊΠ΅. Π Π΅ΠΊΠΎΠΌΠ΅Π½Π΄Π°ΡΠΈΠΈ Π²ΠΊΠ»ΡΡΠ°ΡΡ Π²ΠΎΠΏΡΠΎΡΡ ΡΡΠΈΠΎΠ»ΠΎΠ³ΠΈΠΈ, ΠΏΠ°ΡΠΎΠ³Π΅Π½Π΅Π·Π°, ΠΊΠ»ΠΈΠ½ΠΈΡΠ΅ΡΠΊΠΎΠΉ ΠΊΠ°ΡΡΠΈΠ½Ρ, ΠΌΠ΅ΡΠΎΠ΄ΠΎΠ² Π»Π°Π±ΠΎΡΠ°ΡΠΎΡΠ½ΠΎΠΉ ΠΈΒ ΠΈΠ½ΡΡΡΡΠΌΠ΅Π½ΡΠ°Π»ΡΠ½ΠΎΠΉ Π΄ΠΈΠ°Π³Π½ΠΎΡΡΠΈΠΊΠΈ ΡΠ΅ΠΏΡΠΈΡΠ΅ΡΠΊΠΎΠ³ΠΎ ΡΠΎΠΊΠ°. ΠΡΠ΅Π΄ΡΡΠ°Π²Π»Π΅Π½Π° ΡΡΠ°ΡΡΠΎΠ²Π°Ρ ΠΈΠ½ΡΠ΅Π½ΡΠΈΠ²Π½Π°Ρ ΡΠ΅ΡΠ°ΠΏΠΈΡ ΡΠ΅ΠΏΡΠΈΡΠ΅ΡΠΊΠΎΠ³ΠΎ ΡΠΎΠΊΠ°, Π²ΠΊΠ»ΡΡΠ°Ρ ΠΏΠΎΠ΄Ρ
ΠΎΠ΄Ρ ΠΏΠΎ Π½Π°Π·Π½Π°ΡΠ΅Π½ΠΈΡ Π²Π°Π·ΠΎΠΏΡΠ΅ΡΡΠΎΡΠ½ΡΡ
ΠΈΒ ΠΈΠ½ΠΎΡΡΠΎΠΏΠ½ΡΡ
ΠΏΡΠ΅ΠΏΠ°ΡΠ°ΡΠΎΠ², ΡΠ΅ΠΊΠΎΠΌΠ΅Π½Π΄Π°ΡΠΈΠΈ ΠΏΠΎ Π²ΡΠ±ΠΎΡΡ Π°Π½ΡΠΈΠ±Π°ΠΊΡΠ΅ΡΠΈΠ°Π»ΡΠ½ΡΡ
ΠΏΡΠ΅ΠΏΠ°ΡΠ°ΡΠΎΠ², ΠΎΡΠΎΠ±Π΅Π½Π½ΠΎΡΡΠΈ ΠΈΠ½ΡΡΠ·ΠΈΠΎΠ½Π½ΠΎΠΉ ΠΈΒ Π°Π΄ΡΡΠ²Π°Π½ΡΠ½ΠΎΠΉ ΡΠ΅ΡΠ°ΠΏΠΈΠΈ, Π²Β ΡΠΎΠΌ ΡΠΈΡΠ»Π΅ ΠΏΡΠΈ ΡΠ΅ΡΡΠ°ΠΊΡΠ΅ΡΠ½ΠΎΠΌ ΠΊΒ ΡΠ΅ΡΠ°ΠΏΠΈΠΈ ΡΠ΅ΠΏΡΠΈΡΠ΅ΡΠΊΠΎΠΌ ΡΠΎΠΊΠ΅. ΠΠ±ΡΡΠΆΠ΄Π΅Π½Ρ Π²ΠΎΠΏΡΠΎΡΡ Ρ
ΠΈΡΡΡΠ³ΠΈΡΠ΅ΡΠΊΠΎΠ³ΠΎ Π»Π΅ΡΠ΅Π½ΠΈΡ ΠΎΡΠ°Π³Π° ΠΈΠ½ΡΠ΅ΠΊΡΠΈΠΈ. ΠΡΠ΅Π΄ΡΡΠ°Π²Π»Π΅Π½Ρ ΠΊΡΠΈΡΠ΅ΡΠΈΠΈ ΠΊΠ°ΡΠ΅ΡΡΠ²Π° ΠΎΠΊΠ°Π·Π°Π½ΠΈΡ ΠΌΠ΅Π΄ΠΈΡΠΈΠ½ΡΠΊΠΎΠΉ ΠΏΠΎΠΌΠΎΡΠΈ Π²Π·ΡΠΎΡΠ»ΡΠΌ ΠΏΠ°ΡΠΈΠ΅Π½ΡΠ°ΠΌ ΡΒ ΡΠ΅ΠΏΡΠΈΡΠ΅ΡΠΊΠΈΠΌ ΡΠΎΠΊΠΎΠΌ ΠΈΒ Π°Π»Π³ΠΎΡΠΈΡΠΌΡ Π΄Π΅ΠΉΡΡΠ²ΠΈΠΉ Π²ΡΠ°ΡΠ° ΠΏΡΠΈ Π΄ΠΈΠ°Π³Π½ΠΎΡΡΠΈΠΊΠ΅ ΠΈΒ ΠΈΠ½ΡΠ΅Π½ΡΠΈΠ²Π½ΠΎΠΉ ΡΠ΅ΡΠ°ΠΏΠΈΠΈ ΠΏΠ°ΡΠΈΠ΅Π½ΡΠΎΠ² ΡΒ ΡΠ΅ΠΏΡΠΈΡΠ΅ΡΠΊΠΈΠΌ ΡΠΎΠΊΠΎΠΌ
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