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Evaluating Effects of Conditioning Formulations on Hair
Published in Randy Schueller, Perry Romanowski, Conditioning Agents for Hair and Skin, 2020
Although streaming potential analysis of fibers has been used in the textile chemistry for some time, the simultaneous measurement of electrokinetic parameters (streaming potential and conductivity) and permeability of fiber plugs is a relatively new approach to study both model conditioning actives and complete commercial formulations (18,42). A simplified scheme of a DEPA experiment is presented in Figure 6. A typical experimental protocol includes the measurements of untreated hair, treatment with a conditioning agent, and measurements of the kinetics of sorption/desorption of ions during rinsing with a test solution (5 x 10~5 M KC1). The streaming potential data, converted into zeta potentials by means of the Smoluchowski equation, give information about the state of the fiber surface and the presence of adsorbed anionic or cationic groups. Conductivity, on the other hand, is related to the presence of free ions in the test solution (although surface conductivity of hair may also be a contributing factor), and its variation in the course of experiment is due to the desorption of ions into the test solution. In addition to this, changes in the flow rates (permeability) indicate variations in the volume of the fibers (i.e., swelling or shrinking) or deposition of surfactant or polymer on the fiber surface.
The Electrical Properties of Cells
Published in Richard C. Niemtzow, Transmembrane Potentials and Characteristics of Immune and Tumor Cell, 2020
where gx is the conductance of some univalent ion, X, Px is its permeability, [X]o and [X]i are the external and internal concentrations of ion X, and the other symbols have been previously described. Intuitively, the relationship implies that the permeability is a measure of an ion’s ability to move across the membrane under conditions of no net driving force, while the conductance is a measure of the ease of movement of ions in response to a driving force. The ease of movement is, of course, related to the permeability, but is also related to the driving force. To express this relationship in another fashion: permeability is a measure of the “selectivity” of an ion pathway across the membrane, while conductivity is a measure of the “interaction” of the ions with the pathway.
Safety Limits for Clinical NMR Examinations
Published in Bertil R. R. Persson, Freddy Ståhlberg, Health and Safety of Clinical NMR Examinations, 2019
Bertil R. R. Persson, Freddy Ståhlberg
The conductivity of muscle is about 0.1 S/m at 10 kHz and 1 kHz and brain tissue has a conductivity of about 0.2 S/m. Thus, applying Equation 4 and assuming an average value for tissue conductivity of 0.2 S/m and a body radius of 0.15 m, the limit applied to current density of 0.3 A/m2 RMS for pulses of the half-periods exceeding 10 msec restricts the RMS rate of change of the z-gradient magnetic flux density to
A novel nasal co-loaded loratadine and sulpiride nanoemulsion with improved downregulation of TNF-α, TGF-β and IL-1 in rabbit models of ovalbumin-induced allergic rhinitis
Published in Drug Delivery, 2021
Soad A. Mohamad, Mohamed A. Safwat, Mahmoud Elrehany, Sherif A. Maher, Ahmed M. Badawi, Heba F. Mansour
Droplet size is an important characteristic for evaluation of the stability of nanoemulsion and improvement of drug bioavailability (Xi et al., 2009). It is an essential factor since it influences the drug release and biological absorption (Parul et al., 2013). Depending on the appearance, viscosity and entrapment results, F1, F2 and F3 were selected for this investigation. The mean droplet size, polydispersity index and zeta potential of these formulations are displayed in Table 3. F3 demonstrated the smallest droplet size (85.2±0.2nm) while F1 showed the largest one (149±2nm). F2 and F3 had the lowermost values of PDI (0.44±0.02 and 0.35±0.0 respectively) while F1 exhibited a PDI value of 0.78±0.01. Zeta Potential ranged from −20.8 to −29.7mV with F2 having the highest value. The electrical conductivity values ranged from 0.00 to 0.02 mS/cm. Thus, F2 and F3 were selected for following investigations.
In vivo magnetic nanoparticle hyperthermia: a review on preclinical studies, low-field nano-heaters, noninvasive thermometry and computer simulations for treatment planning
Published in International Journal of Hyperthermia, 2020
Harley F. Rodrigues, Gustavo Capistrano, Andris F. Bakuzis
However, as pointed out by Kozissnik et al., the establishment of a clinical safe limit should not be performed without taking into account the intrinsic dependence of the skin's electrical conductivity (109]. For instance, modeling the skin as a real dielectric medium, using the condition in which the Atkinson criterion was determined (with the AMF frequency m−1 (in SI units: one Simiens corresponds to [S] = 1 A2.s3.kg−1.m−2). Comparatively, if we consider the value of 100 kHz used for humans treatments, then this same parameter falls three-orders of magnitude to −4 S.m−1 [132–135]. In this context, it should be noted that according to Atkinson's own expression for the non-localized heat loss power (24] and, if the Atkinson’s experiment were performed at 100 kHz (the same frequency of the AMF applicator for humans), then the new limit that would need to be exceeded in order to produce the same value of 8 A.m−1.s−1) ≅ 1.11 × 1010 A.m−1.s−1 .
Transient blood–brain barrier disruption is induced by low pulsed electrical fields in vitro: an analysis of permeability and trans-endothelial electric resistivity
Published in Drug Delivery, 2019
Shirley Sharabi, Yael Bresler, Orly Ravid, Chen Shemesh, Dana Atrakchi, Michal Schnaider-Beeri, Fabien Gosselet, Lucie Dehouck, David Last, David Guez, Dianne Daniels, Yael Mardor, Itzik Cooper
The numerical model calculated the electric field distribution between the electrodes. First the model was solved without conductivity changes. The results of the constant conductivity model demonstrated that in the center of the TW insert, the electric field between the electrode is relatively uniform and can be approximated as voltage-to-distance ratio. Around the edge of the electrodes, higher electrical fields are developed. In order to incorporate the changes in conductivity, the electric field of for each voltage was considered uniform and was calculated as the voltage-to-distance ratio. The time constant of the function describing the dependence of the change in TEER in the pulse voltage was modified accordingly (divided by 0.68 cm) and the equation was multiplied by the conductivity of the initial cells to account for the changes. The conductivity was thus described as: σ0 is the initial conductivity and E is the electric field.