The paper presents steady-state and time-resolved experiments on photophysical processes associated with photodynamic inactivation of infections provided by nebulization of Radachlorin ...photosensitizer solution. As models of surfaces subjected to photodynamic inactivation we used glass, plant leaf, mushroom cap peel and superficial fascia of chicken and salmon skin flaps. The oxygen content in the photosensitizer solution was varied by blowing with atmospheric air and with pure oxygen. It was shown that singlet oxygen was generated efficiently in the aerosol jet and that its amount increased noticeably at higher oxygen concentrations. The kinetics of photosensitizer photobleaching on different surfaces were found to be significantly different with characteristic decay times varying from seconds for leaf and glass to minutes for fascial flaps. This observation was attributed to much faster oxygen depletion on rough crumbly surfaces of biological samples due to effective oxidation reactions occurred. The singlet oxygen generation and degradation times, and the relative quantum yield were determined on different surfaces by recording time-resolved phosphorescence at about 1270 nm under normoxic and hyperoxic conditions and analyzed on the basis of the set of master equations. The results obtained provide reference marks for choosing optimal irradiation durations for photodynamic inactivation of pathogenic infectious agents (bacteria, mycobacteria, fungi, viruses) on mucous membranes, including the tracheobronchial tree.
•Singlet oxygen is efficiently generated in the aerosol jet.•Kinetics of photosensitizer photobleaching differs significantly depending on the surface type.•Singlet oxygen generation time drops significantly at hyperoxic conditions.
The investigation of in-vitro response of cell cultures derived from tumor material of individual patients with similar tumor localizations to photodynamic treatment is presented. Tumor types ...included in the research were renal cell carcinoma, melanoma and alveolar, synovial, lypo- and osteo- sarcomas. Long-term observations of treatment-induced morphological changes in cells were performed by means of digital holographic microscopy. A substantial variance in response of cells of individual patients with similar tumor types and localizations to photodynamic treatment with the same dose has been observed. These peculiarities are indicative of the demand to personalized protocols of photodynamic treatment. The elevated resistance of cells of some patients to treatment at high doses highlights potential limitations of photodynamic therapy for some patients. Digital holographic microscopy is shown to be an informative label-free noninvasive tool allowing for long-term monitoring of cell samples in vitro and providing quantitative information on necrosis rate and loss of cellular dry mass. The developed methodology can be generalized for analysis of cellular response to various therapies.
•Tumor cells of patients with the same malignancy show different response to PDT.•PDT can be inefficient for treatment of some patients.•Digital holography is informative in assessment of cells death dynamics.•Average phase shift and dry mass decrease exponentially in a course of cell necrosis.•Proliferative activity of cells does not correlate with their resistivity to PDT.
Time-resolved polarised fluorescence in flavin adenine dinucleotide (FAD) in water-propylene glycol mixtures has been studied as a function of propylene glycol concentration using the TCSPC ...technique. The fluorescence was excited by picosecond laser pulses either at 450 nm or at 355 nm, the wavelengths that belong to the first and second FAD absorption bands, respectively. The global fit procedure was used for the determination of fluorescence decay times, corresponding weighting coefficients, initial anisotropy and rotational diffusion time from experiment. The experimental data manifested a double-exponential decay in the whole range of propylene glycol concentrations with the decay times
$ \tau _1 $
τ
1
,
$ \tau _2 $
τ
2
and weighting coefficients
$ a_1 $
a
1
,
$ a_2 $
a
2
. The coefficients
$ a_1 $
a
1
and
$ a_2 $
a
2
and the corresponding relative fluorescence quantum yields
$ Q_{(1)rel} $
Q
(
1
)
r
e
l
and
$ Q_{(2)rel} $
Q
(
2
)
r
e
l
were shown to change dramatically with addition of propylene glycol to the solution and demonstrated the domination of contribution of longer decay time at medium and high propylene glycol concentrations. The rotational diffusion time
$ \tau _{rot} $
τ
r
o
t
manifested a sharp rise, up to 40 times with propylene glycol concentration that was practically proportional to solution viscosity. The initial anisotropy was determined to be equal to
$ r_0=0.35\pm 0.03 $
r
0
=
0.35
±
0.03
and
$ r_0=0.25\pm 0.02 $
r
0
=
0.25
±
0.02
under excitation at 450 nm and 355 nm, respectively. The dependence of fluorescence parameters on the solution viscosity and polarity was discussed taking into account FAD conformation distributions.
Long-length ultrafine-grained (UFG) Ti rods are produced by equal-channel angular pressing via the conform scheme (ECAP-C) at 200°C, which is followed by drawing at 200°C. The evolution of ...microstructure, macrotexture, and mechanical properties (yield strength, ultimate tensile strength, failure stress, uniform elongation, elongation to failure) of pure Ti during this thermo-mechanical processing is studied. Special attention is also paid to the effect of microstructure on the mechanical behavior of the material after macrolocalization of plastic flow. The number of ECAP-C passes varies in the range of 1–10. The microstructure is more refined with increasing number of ECAP-C passes. Formation of homogeneous microstructure with a grain/subgrain size of 200nm and its saturation after 6 ECAP-C passes are observed. Strength properties increase with increasing number of ECAP passes and saturate after 6 ECAP-C passes to a yield strength of 973MPa, an ultimate tensile strength of 1035MPa, and a true failure stress of 1400MPa (from 625, 750, and 1150MPa in the as-received condition). The true strain at failure failure decreases after ECAP-C processing. The reduction of area and true strain to failure values do not decrease after ECAP-C processing. The sample after 6 ECAP-C passes is subjected to drawing at 200¯C resulting in reduction of a grain/subgrain size to 150nm, formation of (101¯0) fiber texture with respect to the rod axis, and further increase of the yield strength up to 1190MPa, the ultimate tensile strength up to 1230MPa and the true failure stress up to 1600MPa. It is demonstrated that UFG CP Ti has low resistance to macrolocalization of plastic deformation and high resistance to crack formation after necking.
•The chemical interaction between Pr1−xSrxFe1−yCoyO3 and YSZ intensifies with increasing x and y.•The Pr1−xSrxFe0.8Co0.2O3 compositions possess minimum thermal expansion at Sr content of x = 0.3.•The ...conductivity of Pr1−xSrxFe0.8Co0.2O3 increases with increasing Sr content.•The polarization resistance of Pr1−xSrxFe1−yCoyO3 in contact with GDC decreases with increasing x.
The new cathode materials Pr1−xSrxFe1−yCoyO3 (0 ≤ x ≤ 0.4; y = 0.2, 0.5) for SOFC have been studied. The materials were synthesized by the self-propagating high-temperature synthesis method. It was shown that the chemical activity of Pr1−xSrxFe1−yCoyO3 (PSFC) with respect to Zr0.84Y0.16O2−δ (YSZ) electrolyte increases with increasing concentration of Sr and Co, whereas the interaction with Ce0.73Gd0.27O2−δ (GDC) electrolyte was not found. The thermal expansion of praseodymium ferro-cobaltite nonlinearly depends on the Sr content with a minimum at x = 0.3. The conductivity of the investigated materials increases with an increase of Sr and Co content. The cathode materials in contact with YSZ have a high polarization resistance (a few Ω cm2 at 850 °C) due to their chemical interaction. Replacement of YSZ electrolyte with GDC results in the reduction of the polarization resistance by an order of magnitude. The Pr0.6Sr0.4Fe0.8Co0.2O3 in contact with GDC has the lowest polarization resistance of 0.05 Ω cm2 at 850 °С.
Annealing behavior of severely-deformed titanium Grade 4 Dyakonov, G.S.; Mironov, S.; Enikeev, N. ...
Materials science & engineering. A, Structural materials : properties, microstructure and processing,
01/2019, Letnik:
742
Journal Article
Recenzirano
The static-annealing behavior and evolution of the microstructure-strength relationship of severely-deformed commercial-purity titanium Grade 4 over the temperature range of 50–850 °C (0.16–0.57 Tm, ...where Tm is the melting point) were established. The severely-deformed material was obtained via equal-channel angular pressing (ECAP) using the Conform (ECAP-C) technique at 200 °C to an effective accumulated true strain of 8.4. The resulting ultrafine structure was stable to 400 °C. The excellent thermal stability was concluded to be associated with a strain-aging effect, i.e., the enhanced diffusion of solutes within this temperature interval resulting in the formation of solute atmospheres at/near dislocations. At 450–500 °C, rapid growth of strain-free grains occurred, which eliminated the severely-deformed microstructure and promoted softening. This process was deduced to be controlled primarily by grain-boundary energy and therefore was interpreted primarily in terms of grain growth rather than discontinuous recrystallization expected in this temperature range. A further increase in annealing temperature to 600 °C led to normal grain growth. Analysis of the microstructure-strength relationship suggested a significant influence of mechanical twinning on yield strength of the fully-annealed material. At 600 °C and higher temperatures, dissolution of constituent iron-rich particles was observed. This promoted a partial α → β transformation at the temperatures noticeably below the typical beta-transus of pure titanium (~880 °C). This phenomenon resulted in the precipitation of nanoscale β particles which imparted substantial strengthening. Water quenching of the material annealed at 850 °C gave rise to a β → α′ martensitic transformation. The latter process was governed by exceptionally strong variant selection and thereby provided a nearly-ideal restoration of crystallographic orientations of parent α-grains.
We report application of the fluorescence lifetime imaging microscopy (FLIM) for analysis of distributions of intracellular acidity using a chlorin-e6 based photosensitizer Radachlorin. An almost ...two-fold increase of the photosensitizer fluorescence lifetime in alkaline microenvironments as compared to acidic ones allowed for clear distinguishing between acidic and alkaline intracellular structures. Clusterization of a phasor plot calculated from fits of the FLIM raw data by two Gaussian distributions provided accurate automatic segmentation of lysosomes featuring acidic contents. The approach was validated in colocalization experiments with LysoTracker fluorescence in living cells of four established lines. The dependence of photosensitizer fluorescence lifetime on microenvironment acidity allowed for estimation of pH inside the cells, except for the nuclei, where photosensitizer does not penetrate. The developed method is promising for combined application of the photosensitizer for both photodynamic treatment and diagnostics.
•Variations of Radachlorin fluorescence lifetime in cells provide data on acidity.•Phasor plot clusterization allowed for automatic segmentation of acidic structures.•Automatically segmented acidic clusters coincided with LysoTracker fluorescence.
In this paper we apply the methodology based on the analysis of changes in acoustic wave velocities under static stress for measurements of the third-order elastic moduli in three polystyrene-based ...nanocomposites with different fillers: SiO2 particles, halloysite natural tubules, and carbon black particles. The samples were fabricated by the same technology and our data provide information on relative changes of nonlinear properties of the composites caused by addition of the fillers. The data obtained for composites are compared with that for commercial grade polystyrene. The substantial variations of the nonlinear elastic moduli for composites with different types of fillers are demonstrated and analyzed. The results are in a qualitative agreement with theoretical predictions.
•Polystyrene-based nanocomposites with different fillers demonstrate substantial variations of the nonlinear elastic moduli.•Variations of nonlinear moduli due to introduction of nanofillers can be of the order of several tens of %.•Nonlinear elastic moduli are more sensitive to introduction of fillers than linear ones.•Dependence of longitudinal wave velocity on applied stress allows for evaluation of nonlinear elasticity in glassy polymers.
High-resolution electron backscatter diffraction (EBSD) was used to examine the grain structure in long rods of ultrafine-grain (UFG) commercial-purity titanium produced for medical implants. The UFG ...material was obtained by equal channel angular pressing (ECAP) using a Conform scheme followed by rod drawing. The microstructure was found to be bimodal consisting of relatively coarse elongated grains containing well-developed substructure and ultrafine grains. The mean grain size was ~0.3μm, and the fraction of high-angle boundaries was ~45%. The material had a strong <101¯0>-fiber texture. An analysis of the microstructure–properties relationship showed that the increase in material strength developed during severe plastic deformation resulted from grain refinement and substructure evolution in comparable measure.
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