Dentifrice Rheology
Laba Dennis in Rheological Proper ties of Cosmetics and Toiletries, 2017
Another method described by Block is based on measuring the adhesion-cohesion properties of the paste. The sample was placed between two disks, and the vertical force required to pull the disks apart was determined. Stringiness was measured as extension just as the thin neck of paste ruptured. An Instron tensiometer was used. Force was plotted against distance of extension just at snapping of the paste neck. Such plots of extension versus force clearly showed differences between different compositions. Maximum cohesive force was reached quickly, an indication that this was the force needed to lift the disk over the first few millimeters from the surface. It was related to the time required to exhibit thixotropy. Stringiness is a consumer-apparent deficiency, and was easily measured.
Characterization Of Fluids And Gases
Sujoy K. Guba in Bioengineering in Reproductive Medicine, 2020
An adaptation based upon the very simple and convenient apparatus devised by Aberg and Gislen29 is shown in Figure 7.7 The pipette is first partially filled by pouring in the amniotic fluid through the funnel keeping the valve open. Thereafter the valve is closed. A syringe piston is driven at a fixed rate by means of a motor and screw arrangement so as to push a column of air at a steady rate. The column of air pushes out at very low pressure above the atmospheric pressure the amniotic fluid. Under this condition the drops are formed more or less by gravitational forces and yet it is possible to obtain a measure of the volume displaced per unit time knowing the piston size and the movement rate. The falling drops interrupts a light beam and the light pulses are detected by a photocell and the pulses counted by means of a pulse counter. In this situation the volume pumped per unit time divided by the number of drops falling in the same interval gives the drop volume. From the drop volume the surface tension is derived using Equation 7.4. The system can be calibrated by running fluid of known surface tensions such as water, ethanol and benzene. Also at times a check is made against direct determination of amniotic fluid surface tension with a standard surface tension apparatus the du Nouy Tensiometer.
Soft Tissue Surgery of the Knee
Timothy W R Briggs, Jonathan Miles, William Aston, Heledd Havard, Daud TS Chou in Operative Orthopaedics, 2020
The tendons can then be dissected free of the pes medially, carefully preserving as much graft length as possible. This will give a graft of two tendons, which are joined at one end and free at the other. Alternatively, the graft can be prepared in situ. Muscle tissue is scraped off the tendons. Each tendon is sutured, using a whip-stitch, for 30 mm at either end. The two tendons are then passed through the loop of a cortical suspensory button device and folded in half to create a four-strand single bundle graft (Figure 12.18). The graft is then tensioned, in order to prevent stretching in situ. If a tensiometer is available, it is usually tensioned to 80 N (20 lb) for 10 minutes. Next, the graft is measured: most are 8–10 mm, with 7 mm being a minimum acceptable diameter.
Some observations on the liquid crystalline and gel behaviors of aqueous dispersions of a prodrug
Published in Drug Development and Industrial Pharmacy, 2019
Li Tao, Jinjiang Li, Swathi Pinamanenni, Krishnaswamy Raghavan
Surface tension measurement of BMS-830216 in acetate buffer (50 mM, I = 300 mM) (pH = 4) was performed using the Du Noüy ring method (CSC Precision Tensiometer, CSC Scientific Company, Fairfax VA). To perform surface tension measurement, the ring was first cleaned by burning off organic contaminants in flame (Bunsen burner) followed by attaching back to the lever arm of the tensiometer. Then, a sample was carefully transferred to a measurement vessel. Subsequently, the whole vessel was placed onto the sample table of the tensiometer, followed by adjusting the table-top until the ring was slightly submerged into the solution with its position centered to the measurement vessel. Slowly and evenly, the table-top was lowered, and consequently the ring was simultaneously raised. The surface tension reading was recorded when the ring broke through the surface. All measurements were carried out at room temperature (23 ± 3 °C).
Enhancement of ocular anti-glaucomic activity of agomelatine through fabrication of hyaluronic acid modified-elastosomes: formulation, statistical optimisation, in vitro characterisation, histopathological study, and in vivo assessment
Published in Journal of Microencapsulation, 2023
Asmaa Ashraf Nemr, Galal Mohamed El-Mahrouk, Hany Abdo Badie
The surface tension test is an essential test for ocularly applied formulations as it ensures the uniform spreading of the formulation on corneal surface (Hegde et al.2013). Also, it determines the penetration of the drug through the cornea. The surface tension of the AGM-loaded optimum formula was performed by the Du Nouy ring force tensiometer (model K-6, Krϋss GmbH, Hamburg, Germany). First, calibration of the tensiometer with distilled water was performed. Then, 30 ml of distilled water and the optimum formula were used for performing the test. The gap between the ring of the tensiometer and the surface of the tested liquid is adjusted to be equal to 4.5 mm and the surface tension of distilled water was 72 mN/m (Lee et al.2012; Vicario-de-la-Torre et al.2014).
Biophysical and chemical stability of surfactant/budesonide and the pulmonary distribution following intra-tracheal administration
Published in Drug Delivery, 2019
Chung-Ming Chen, Chien-Hsiang Chang, Chih-Hua Chao, Mei-Hui Wang, Tsu-Fu Yeh
The surface tension data were determined by commercial pulsating bubble tensiometer and drop shape tensiometer (model FTA-1000 B class, First Ten Angstroms, USA), respectively. For the surface tension measurements obtained by the commercial pulsating bubble tensiometer (Enhorning, 1977), a bubble was created in the aqueous sample and the pressure difference across the air/liquid interface, used to evaluate the surface tension at the interface, was followed with time. The equilibrium surface tension was then determined until no significant change was detected in the surface tension observations (Chang & Franses, 1994). As for the commercial drop shape tensiometer, a drop of samples was formed in the air environment and the surface tension at the interface of the drop was then evaluated from the profile of the drop (Zuo & Neumann, 2005). Although the drop profile, or corresponding surface tension, could be followed with time, evaporation of the drop could not be totally avoided (the drop size would be decreased with time) and it is unfeasible to measure the surface tension for a very long time. Depending on the dynamic adsorption behavior of the surface active components in the samples, the measured surface tension may not be close to the equilibrium surface tension. For Curosurf suspensions, the dynamic surface tension was decreased fast. However, the adsorption timescale of budesonide suspension was long, or the dynamic surface tension was decreased very slowly. In order to fairly compare the surface tension data of the samples to explore the added effect of budesonide suspension, the data reported in Table 2 were obtained right after the sample drops were formed.
Related Knowledge Centers
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