DERMATOLOGIC GELS SPREADABILITY MEASURING METHODS COMPARATIVE STUDY

Objective: The main objective of our study is the comprehensive analysis and characterization of the existing spreadability evaluation strategies, the comparison of the obtained results reproducibility and convergence through the example of the 9 most widely used dermatological gels. Methods: Dolobene®, Flucinar®, Ketorol®, Contractubex®, Dr. Theiss Venen gel®, Solcoseryl®, Deep Relief®, Hepatrombin® pharmacopoeia gel samples were analyzed using parallel-plate, “slip and drag”, and viscometry methods. Analysis was performed in flow mode at 32±0.2 °C, over shear rates ranging from 0 to 350 s−1, increasing over a period of 120 s, and was maintained at the superior limit for 10 s and then decreased during the same period. At least 5 replicates of each sample were evaluated, and the upward flow curves were fitted using the Casson mathematical model. Results: Solcoseryl® and Dolobene® showed the best spreadability in the parallel-plate method (3115.66±50.00 and 3316.63±50.00, respectively); Contractubex® and Dolobene showed the best spreadability in the “slip and drag” test (73.46±0.5 and 18.32±0.5, respectively); Solcoseryl® and Contractubex® showed the best spreadability in the viscometry test (43.86±0.5 and 76.92±0.5, respectively). Conclusion: This study analyzed the existing methods for determining the spreadability using commercially available samples of the dermatological gels as examples. The viscometric and the "Slip and drag" methods use different characteristics of spreadability, giving a complex evaluation of the measured parameter in vitro. Therefore, the combination of these two methods has the greatest prospects for reliable determination of this indicator.

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Effect of low fibrinogen concentrations on the rheology of human blood in vitro

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1979.236.3.h447 ◽

1979 ◽

Vol 236 (3) ◽

pp. H447-H450

Author(s):

W. Blattler ◽

P. W. Straub ◽

C. Jeanneret ◽

G. S. Horak

Keyword(s):

Human Blood ◽

Cell Aggregation ◽

Fibrinogen Concentration ◽

Shear Rates ◽

Red Blood Cell Aggregation ◽

Low Concentrations ◽

Normal Human ◽

High Concentrations

The influence of low concentrations of fibrinogen on the rheology of normal human blood was investigated with an instrument that permitted simultaneous determination of viscosity and the state of red blood cell aggregation and deformation. Fibrinogen, in concentrations of 9-82 mg/100 ml, decreased blood viscosity at all shear rates below the value obtained with red blood cells suspended in serum. At concentrations above 116 mg/100 ml viscosity was increased. Aggregate formation increased progressively as the fibrinogen concentration increased, necessitating higher dispersing shear rates. The deformation and alignment of the red cells, occurring at a shear rate of 230 s-1, was facilitated by low concentrations. The effect of fibrinogen on low-shear viscosity is explained by the formation of different kinds of aggregates. At low concentrations, the aggregates consist of only few cells forming spherelike particles displaying hemodynamic properties better than those of the single discoid cells. At normal or high concentrations big rodlike aggregates occur and increase resistance to flow.

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DEVELOPMENT OF A BLOOD ANALOG FOR THE HEMODYNAMIC EFFICIENCY EVALUATION OF CARDIOVASCULAR DEVICES

Proceedings of the Canadian Engineering Education Association (CEEA) ◽

10.24908/pceea.v0i0.3986 ◽

2011 ◽

Author(s):

T. T. Nguyen ◽

R. Mongrain ◽

S. Prakash ◽

J. -C. Tardif

Keyword(s):

Shear Stress ◽

Blood Cells ◽

Exposure Duration ◽

Parallel Plate ◽

Efficiency Evaluation ◽

Cardiovascular Devices ◽

Shear Rates ◽

Custom Made ◽

Plate Geometry

Accurate simulation of blood hemolytic potential (i.e. the destruction of red blood cells) would be a valuable tool to evaluate blood-interacting devices. Indeed, such a model would alleviate several practical problems with manipulating real blood (addition of anticoagulants and antibiotics, filtration, etc.). In the present study, we have developed a blood analog which is a suspension of micron-sized natural polymeric gel particles, each encapsulating a dye agent. These particles release the dye agent through shear-induced diffusion and fragmentation from exposure to high, non-physiological shear rates. A controlled shear field was applied to blood analog samples using a custom-made grooved parallel plate geometry device as previously reported in the literature. The device was designed to apply a shear stress and shear exposure duration in the range of 0.15 – 269.18 Pa and 156 - 1297 ms, respectively. From the results obtained, a correlation between the human index of hemolysis and the concentration of the released dye agent can be found. Therefore, the use of the proposed suspensions appears suitable as a blood analog for the in vitro evaluation of the destructive effects of cardiovascular devices.

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The intraoral permeability measurement as a screening for artifact formation by orthodontic products in MRI

Journal of Orofacial Orthopedics / Fortschritte der Kieferorthopädie ◽

10.1007/s00056-021-00360-9 ◽

2021 ◽

Author(s):

Felix H. Blankenstein ◽

Ulrike Kielburg ◽

Ludwig Melerowitz ◽

Daniel Stelmaszczyk

Keyword(s):

Magnetic Permeability ◽

Interrater Reliability ◽

Direct Determination ◽

Magnetic Flux Density ◽

Clinical Test ◽

Permeability Measurement ◽

Reliable Determination ◽

Artifact Formation

Abstract Aim Metal dental products lack precautionary statements regarding MR compatibility due to an exemption in the labelling obligation. Hence, it is difficult for radiologists to decide whether to remove fixed metal objects in patients prior to MRI. A solution could be the direct determination of the magnetic permeability (µr) as a decisive material-related predictor of artifact formation and other interactions. Thus, the applicability of an industrially used measurement device as a screening instrument and the relevance of the manufacturer’s application restrictions in vitro and in vivo were tested. Methods Precision and trueness were tested using self-made test objects with different dimensions and different permeability. To clarify whether the measurement results are affected by the remanence (BR) induced in the objects, 28 brackets of different materials were exposed to a weak and a strong external magnetic field and the magnetic flux density before and after these exposures was compared. The clinical test was performed on a volunteer with an orthodontic appliance experimentally composed of brackets with different levels of magnetic permeability (µr). Validity and intra- and interrater reliability were calculated using two rater groups consisting of four dentists and four medical-technical radiology assistants (MTRA), respectively. Results With coefficients of variation below 0.14%, precision was excellent regardless of object surface and size. Trueness was high on objects with µr ≤ 1.002, and decreased with increasing µr, for which size-dependent correction factors were calculated. Intra- and interrater reliability and validity were excellent and independent of professional intraoral manipulation experience. Conclusions The permeability measurement allows for a valid and reliable determination of the magnetizability of intraoral metal objects. When used as a screening tool to detect nonartifact-causing objects, no correction factor needs to be calculated. For the first time, it offers radiologists a decision support for the selective removal of only the highly permeable components of the multiband apparatus.

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In Vitro Determination of Thromboembolic States: Cellular, Molecular and Genetic Aspects

10.1055/s-0039-1687287 ◽

1979 ◽

Author(s):

L. Dintenfass

Keyword(s):

Blood Viscosity ◽

Apparent Viscosity ◽

Correlation Coefficients ◽

Significant Feature ◽

Direct Function ◽

Shear Rates ◽

Aggregation Of Platelets ◽

Severe Anxiety

Techniques of the in vitro formation of artificial thrombi under controlled conditions of shear rates, and the principles of their formation and morphology, were established by Dintenrass and Rozenberg between 1963 and 1967, and Dintenfass and Stewart in 1968. Aggregation of platelets was found to be a direct function of shear rate. It has been later established that that an elevation of the apparent viscosity of artificial (red-white, and white) thrombi is a significant feature of renal failure, hypertension, myocardial infarction, and peripheral vascular disease. In diabetes mellitus, diabetic and nondiahetic retinopathy, severe anxiety and cigarette smoking there is a serious elevation of the blood viscosity factors. The apparent viscosity of artificial thrombi and of the other blood viscosity factorsis correlated with the fibrinogen level, and albumin/fibrinogen ratios. Significance limits of these correlations vary in different disorders, and the correlation coefficients may exhibit both the negative and the positive signs, mainly depending on the ABO blood groups. Abnormality of the blood viscosity factors can be used probably for detection of the silent states of various diseases, as well as for prediction of impeding cardiovascular episodes.

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Water as a Blood Model for Determination of CO2 Removal Performance of Membrane Oxygenators

Membranes ◽

10.3390/membranes11050356 ◽

2021 ◽

Vol 11 (5) ◽

pp. 356

Author(s):

Benjamin Lukitsch ◽

Raffael Koller ◽

Paul Ecker ◽

Martin Elenkov ◽

Christoph Janeczek ◽

...

Keyword(s):

Boundary Layer ◽

Removal Rate ◽

In Vitro Tests ◽

Co2 Removal ◽

Reliable Determination ◽

Fluid Properties ◽

Membrane Oxygenators

CO2 removal via membrane oxygenators has become an important and reliable clinical technique. Nevertheless, oxygenators must be further optimized to increase CO2 removal performance and to reduce severe side effects. Here, in vitro tests with water can significantly reduce costs and effort during development. However, they must be able to reasonably represent the CO2 removal performance observed with blood. In this study, the deviation between the CO2 removal rate determined in vivo with porcine blood from that determined in vitro with water is quantified. The magnitude of this deviation (approx. 10%) is consistent with results reported in the literature. To better understand the remaining difference in CO2 removal rate and in order to assess the application limits of in vitro water tests, CFD simulations were conducted. They allow to quantify and investigate the influences of the differing fluid properties of blood and water on the CO2 removal rate. The CFD results indicate that the main CO2 transport resistance, the diffusional boundary layer, behaves generally differently in blood and water. Hence, studies of the CO2 boundary layer should be preferably conducted with blood. In contrast, water tests can be considered suitable for reliable determination of the total CO2 removal performance of oxygenators.

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