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Merete Haedersdal - One of the best experts on this subject based on the ideXlab platform.
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fractional laser assisted drug delivery laser Channel Depth influences biodistribution and skin deposition of methotrexate
Lasers in Surgery and Medicine, 2016Co-Authors: E H Taudorf, Catharina M Lerche, Andres M Erlendsson, Peter A Philipsen, Steen Honore Hansen, Christian Janfelt, Uwe Paasch, Rox R Anderson, Merete HaedersdalAbstract:Background and Objective Ablative fractional laser (AFXL) facilitates delivery of topical methotrexate (MTX). This study investigates impact of laser-Channel Depth on topical MTX-delivery. Materials and Methods MTX (1% [w/v]) diffused for 21 hours through AFXL-exposed porcine skin in in vitro Franz Cells (n = 120). A 2,940 nm AFXL generated microscopic ablation zones (MAZs) into epidermis (11 mJ/Channel, MAZ-E), superficial-dermis (26 mJ/Channel, MAZ-DS), and mid-dermis (256 mJ/Channel, MAZ-DM). High performance liquid chromatography (HPLC) was used to quantify MTX deposition in full-thickness skin, biodistribution profiles at specific skin levels, and transdermal permeation. Fluorescence microscopy was used to visualize UVC-activated MTX-fluorescence (254 nm) and semi-quantify MTX distribution in skin. Results AFXL increased topical MTX-delivery (P < 0.001). Without laser exposure, MTX-concentration in full-thickness skin was 0.07 mg/cm2, increasing sixfold (MAZ-E), ninefold (MAZ-DS), and 11-fold (MAZ-DM) after AFXL (P < 0.001). Deeper MAZs increased MTX-concentrations in all skin layers (P < 0.038) and favored maximum accumulation in deeper skin layers (MAZ-E: 1.85 mg/cm3 at 500 μm skin-level vs. MAZ-DM: 3.75 mg/cm3 at 800 μm, P = 0.002). Ratio of skin deposition versus transdermal permeation remained constant, regardless of MAZ Depth (P = 0.172). Fluorescence intensities confirmed MTX biodistribution through coagulation zones and into surrounding skin, regardless of thickness of coagulation zones (6–47 μm, P ≥ 0.438). Conclusion AFXL greatly increases topical MTX-delivery. Deeper MAZs deliver higher MTX-concentrations than superficial MAZs, which indicates that laser Channel Depth may be important for topical delivery of hydrophilic molecules. Lasers Surg. Med. © 2016 Wiley Periodicals, Inc.
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Fractional laser-assisted drug delivery: Laser Channel Depth influences biodistribution and skin deposition of methotrexate.
Lasers in surgery and medicine, 2016Co-Authors: E H Taudorf, Catharina M Lerche, Andres M Erlendsson, Peter A Philipsen, Steen Honore Hansen, Christian Janfelt, Uwe Paasch, Rox R Anderson, Merete HaedersdalAbstract:Background and Objective Ablative fractional laser (AFXL) facilitates delivery of topical methotrexate (MTX). This study investigates impact of laser-Channel Depth on topical MTX-delivery. Materials and Methods MTX (1% [w/v]) diffused for 21 hours through AFXL-exposed porcine skin in in vitro Franz Cells (n = 120). A 2,940 nm AFXL generated microscopic ablation zones (MAZs) into epidermis (11 mJ/Channel, MAZ-E), superficial-dermis (26 mJ/Channel, MAZ-DS), and mid-dermis (256 mJ/Channel, MAZ-DM). High performance liquid chromatography (HPLC) was used to quantify MTX deposition in full-thickness skin, biodistribution profiles at specific skin levels, and transdermal permeation. Fluorescence microscopy was used to visualize UVC-activated MTX-fluorescence (254 nm) and semi-quantify MTX distribution in skin. Results AFXL increased topical MTX-delivery (P
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Fractional laser‐assisted delivery of methyl aminolevulinate: Impact of laser Channel Depth and incubation time
Lasers in surgery and medicine, 2012Co-Authors: C.s. Haak, Rox R Anderson, William A. Farinelli, Joshua Tam, Apostolos G. Doukas, Merete HaedersdalAbstract:Background and Objectives Pretreatment of skin with ablative fractional lasers (AFXL) enhances the uptake of topical photosensitizers used in photodynamic therapy (PDT). Distribution of photosensitizer into skin layers may depend on Depth of laser Channels and incubation time. This study evaluates whether Depth of intradermal laser Channels and incubation time may affect AFXL-assisted delivery of methyl aminolevulinate (MAL). Materials and Methods Yorkshire swine were treated with CO2 AFXL at energy levels of 37, 190, and 380 mJ/laser Channel and subsequent application of MAL cream (Metvix®) for 30, 60, 120, and 180 minutes incubation time. Fluorescence photography and fluorescence microscopy quantified MAL-induced porphyrin fluorescence (PpIX) at the skin surface and at five specific skin Depths (120, 500, 1,000, 1,500, and 1,800 µm). Results Laser Channels penetrated into superficial (∼300 µm), mid (∼1,400 µm), and deep dermis/upper subcutaneous fat layer (∼2,100 µm). Similar fluorescence intensities were induced at the skin surface and throughout skin layers independent of laser Channel Depth (180 minutes; P
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fractional laser assisted delivery of methyl aminolevulinate impact of laser Channel Depth and incubation time
Lasers in Surgery and Medicine, 2012Co-Authors: Rox R Anderson, Merete Haedersdal, C.s. Haak, William A. Farinelli, Joshua Tam, Apostolos G. DoukasAbstract:Background and Objectives Pretreatment of skin with ablative fractional lasers (AFXL) enhances the uptake of topical photosensitizers used in photodynamic therapy (PDT). Distribution of photosensitizer into skin layers may depend on Depth of laser Channels and incubation time. This study evaluates whether Depth of intradermal laser Channels and incubation time may affect AFXL-assisted delivery of methyl aminolevulinate (MAL). Materials and Methods Yorkshire swine were treated with CO2 AFXL at energy levels of 37, 190, and 380 mJ/laser Channel and subsequent application of MAL cream (Metvix®) for 30, 60, 120, and 180 minutes incubation time. Fluorescence photography and fluorescence microscopy quantified MAL-induced porphyrin fluorescence (PpIX) at the skin surface and at five specific skin Depths (120, 500, 1,000, 1,500, and 1,800 µm). Results Laser Channels penetrated into superficial (∼300 µm), mid (∼1,400 µm), and deep dermis/upper subcutaneous fat layer (∼2,100 µm). Similar fluorescence intensities were induced at the skin surface and throughout skin layers independent of laser Channel Depth (180 minutes; P < 0.19). AFXL accelerated PpIX fluorescence from skin surface to deep dermis. After laser exposure and 60 minutes MAL incubation, surface fluorescence was significantly higher compared to intact, not laser-exposed skin at 180 minutes (AFXL-MAL 60 minutes vs. MAL 180 minutes, 69.16 a.u. vs. 23.49 a.u.; P < 0.01). Through all skin layers (120–1,800 µm), laser exposure and 120 minutes MAL incubation induced significantly higher fluorescence intensities in HF and dermis than non-laser exposed sites at 180 minutes (1,800 µm, AFXL-MAL 120 minutes vs. MAL 180 minutes, HF 14.76 a.u. vs. 6.69 a.u. and dermis 6.98 a.u. vs. 5.87 a.u.; P < 0.01). Conclusions AFXL pretreatment accelerates PpIX accumulation, but intradermal Depth of laser Channels does not affect porphyrin accumulation. Further studies are required to examine these findings in clinical trials. Lasers Surg. Med. 44: 787–795, 2012. © 2012 Wiley Periodicals, Inc.
R. Mark Wilson - One of the best experts on this subject based on the ideXlab platform.
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Flow geometry flattens viscous fingers
Physics Today, 2012Co-Authors: R. Mark WilsonAbstract:A simple gradient in Channel Depth can suppress the interfacial instability that always occurs when a less viscous fluid pushes against a more viscous one.
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Flow geometry flattens viscous fingers
Physics Today, 2012Co-Authors: R. Mark WilsonAbstract:A simple gradient in Channel Depth can suppress the interfacial instability that always occurs when a less viscous fluid pushes against a more viscous one. A simple gradient in Channel Depth can suppress the interfacial instability that always occurs when a less viscous fluid pushes against a more viscous one.
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Flow geometry controls viscous fingering
Physics Today, 2012Co-Authors: R. Mark WilsonAbstract:A gradient in Channel Depth can suppress the instability that occurs when a less viscous fluid invades a more viscous one.
Anne Juel - One of the best experts on this subject based on the ideXlab platform.
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sensitivity of saffman taylor fingers to Channel Depth perturbations
Journal of Fluid Mechanics, 2016Co-Authors: Andres Francogomez, Alice B. Thompson, Andrew L. Hazel, Anne JuelAbstract:We examine the sensitivity of Saffman–Taylor fingers to controlled variations in Channel Depth by investigating the effects of centred, rectangular occlusions in Hele-Shaw Channels. For large occlusions, the geometry is known to support symmetric, asymmetric and oscillatory propagation states when air displaces a more viscous fluid from within the Channel. A previously developed Depth-averaged model is found to be in quantitative agreement with laboratory experiments once the aspect ratio (width/height) of the tube’s cross-section reaches a value of 40. We find that the multiplicity of solutions at finite occlusion heights arises through interactions of the single stable and multiple unstable solutions already present in the absence of the occlusion: the classic Saffman–Taylor viscous fingering problem. The sequence of interactions that occurs with increasing occlusion height is the same for all aspect ratios investigated, but the occlusion height required for each interaction decreases with increasing aspect ratio. Thus, the system becomes more sensitive as the aspect ratio increases in the sense that multiple solutions are provoked for smaller relative Depth changes. We estimate that the required Depth changes become of the same order as the typical roughnesses of the experimental system ( $1~{\rm\mu}\text{m}$ ) for aspect ratios beyond 155, which we conjecture underlies the extreme sensitivity of experiments conducted in such Hele-Shaw Channels.
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Sensitivity of Saffman–Taylor fingers to Channel-Depth perturbations
Journal of Fluid Mechanics, 2016Co-Authors: Andres Franco-gomez, Alice B. Thompson, Andrew L. Hazel, Anne JuelAbstract:We examine the sensitivity of Saffman–Taylor fingers to controlled variations in Channel Depth by investigating the effects of centred, rectangular occlusions in Hele-Shaw Channels. For large occlusions, the geometry is known to support symmetric, asymmetric and oscillatory propagation states when air displaces a more viscous fluid from within the Channel. A previously developed Depth-averaged model is found to be in quantitative agreement with laboratory experiments once the aspect ratio (width/height) of the tube’s cross-section reaches a value of 40. We find that the multiplicity of solutions at finite occlusion heights arises through interactions of the single stable and multiple unstable solutions already present in the absence of the occlusion: the classic Saffman–Taylor viscous fingering problem. The sequence of interactions that occurs with increasing occlusion height is the same for all aspect ratios investigated, but the occlusion height required for each interaction decreases with increasing aspect ratio. Thus, the system becomes more sensitive as the aspect ratio increases in the sense that multiple solutions are provoked for smaller relative Depth changes. We estimate that the required Depth changes become of the same order as the typical roughnesses of the experimental system ( $1~{\rm\mu}\text{m}$ ) for aspect ratios beyond 155, which we conjecture underlies the extreme sensitivity of experiments conducted in such Hele-Shaw Channels.
Adel A. Hegazy - One of the best experts on this subject based on the ideXlab platform.
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Technical note: Optimizing the thermohydraulic performance of flat-plate solar air heaters operating with fixed⧸variable pumping power
Renewable Energy, 1999Co-Authors: Adel A. HegazyAbstract:Abstract The validity of the analytical criterion derived for predicting optimum Channel Depth of conventional Solar Air Heaters (SAHs) has been explored for other flat-plate models of practical importance. Compared to the conventional design with air-Channel under the absorber, the considered two models have airflow over the absorber and on both sides of it, respectively. Particularly examined is the effect of Channel Depth-to-length ratio (D⧸L) on the performance characteristics of these single-pass SAHs. Performance simulation results confirm the applicability of the criterion for these models over a wide range of influencing parameters including specific pumping power (P), emissivity of Channel surfaces and wind heat transfer coefficient. It is found that the criterion successfully estimates the Channel Depth parameter (δp) that optimizes the performance for fixed or variable pumping-power operation. For the latter mode of operation, however, the ratio D⧸L = 3 ∗ 10−3 is recommended. Also, the performance diagram of a particular model design can easily be generalized if it is rated in terms of the analytical parameters δp and P⧸ L which tightens up the intimate dependence of heater performance on both Channel dimensions and flow pumping power.
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Optimization of flow-Channel Depth for conventional flat-plate solar air heaters
Renewable Energy, 1996Co-Authors: Adel A. HegazyAbstract:An analytical criterion for determining the optimum flow-Channel Depth of conventional flat-plate solar air heaters has been developed. The criterion gives the minimum Channel-Depth required to maximize the useful heat gain from the absorber plate to the flowing air for a particular pumping power. A parametric study was carried out to validate the engineering accuracy of the optimization criterion which was found to be considerably accurate over the entire range of variables covered. An expression for estimating the Channel-Depth-to-length ratio that yields an outlet air temperature equal to the absorber-plate mean temperature is also derived in terms of flow pumping power. This expression is of great importance for designers of this type of solar air heater.
Matthias Kraume - One of the best experts on this subject based on the ideXlab platform.
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comparison of the single bubble ascent in a newtonian and a non newtonian liquid a phenomenological piv study
Chemie Ingenieur Technik, 2016Co-Authors: L. Böhm, Manuel Brehmer, Matthias KraumeAbstract:This fundamental study of single bubbles rising in confined geometries was motivated by the aeration in membrane bioreactors. The parameters Channel Depth, bubble size, superimposed liquid velocity and rheology of the liquid (Newtonian, non-Newtonian) were varied. The flow field close to the bubble with a negative wake in the non-Newtonian liquid is discussed and a data presentation is introduced allowing a statistical analysis. Cumulative distribution functions for the velocity magnitude, vorticity, strain and shear stress are extracted from the flow fields for each parameter combination. Except for Channel Depth, almost all analyzed properties increased with increasing bubble size and superimposed liquid velocity. An influence of the rheology on the results is visible especially for the shear stress.
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Comparison of the Single Bubble Ascent in a Newtonian and a Non‐Newtonian Liquid: A Phenomenological PIV Study
Chemie Ingenieur Technik, 2015Co-Authors: Lutz Böhm, Manuel Brehmer, Matthias KraumeAbstract:This fundamental study of single bubbles rising in confined geometries was motivated by the aeration in membrane bioreactors. The parameters Channel Depth, bubble size, superimposed liquid velocity and rheology of the liquid (Newtonian, non-Newtonian) were varied. The flow field close to the bubble with a negative wake in the non-Newtonian liquid is discussed and a data presentation is introduced allowing a statistical analysis. Cumulative distribution functions for the velocity magnitude, vorticity, strain and shear stress are extracted from the flow fields for each parameter combination. Except for Channel Depth, almost all analyzed properties increased with increasing bubble size and superimposed liquid velocity. An influence of the rheology on the results is visible especially for the shear stress.
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Rising behaviour of single bubbles in narrow rectangular Channels in Newtonian and non-Newtonian liquids
International Journal of Multiphase Flow, 2014Co-Authors: Lutz Böhm, Tokihiro Kurita, Katsuki Kimura, Matthias KraumeAbstract:Abstract A phenomenological investigation of single bubbles ascending in a confined geometry with a rectangular cross section was done. Motivated by the goal to get a deeper understanding of the bubble behaviour in flat sheet membrane modules used in membrane bioreactors, the parameters Channel Depth (=spacing, 5–7 mm), bubble size (3–9 mm), superimposed liquid velocity (0–23.5 cm/s) and rheology of the continuous phase (Newtonian, shear-thinning) were varied. The shear-thinning liquid was used to simulate the rheological behaviour of activated sludge apparent in membrane bioreactors. The analysed properties included the rising paths, bubble shape, absolute and relative terminal rise velocities, friction factors and oscillation frequencies and amplitudes of the bubble. As expected, a significant influence of the rheology of the continuous phase was found on the rising behaviour. In the shear-thinning liquid, the bubbles followed mostly a straight rising path with negligible oscillations. The variation of the Channel Depth mainly had an influence on the terminal rise velocity of the bubbles ascending in the shear-thinning liquid with higher values in the Channel with the larger Channel Depth. Increasing the bubble size led to higher rising velocities and to enhanced oscillations.