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Gloves
Published in Robert N. Phalen, Howard I. Maibach, Protective Gloves for Occupational Use, 2023
Marie-Noëlle Crépy, Pierre Hoerner
Elastomers must be formulated with chemical additives to reach the glove's desired properties such as mechanical resistance, barrier integrity, color, and aging protection. In the latex dipping process, these various chemicals should be incorporated directly into the water dispersion. As most of these chemicals are not water-soluble, they should be introduced as dispersions. Such dispersions need to be prepared and stabilized properly.
Properties of the Arterial Wall
Published in Wilmer W Nichols, Michael F O'Rourke, Elazer R Edelman, Charalambos Vlachopoulos, McDonald's Blood Flow in Arteries, 2022
The theory of large deformations in elastomers in terms of the coiling and uncurling of their long molecular chains using thermodynamic postulates has been quite successful in studying rubber elasticity, and on the assumption that these properties are shared by soft body tissues, elastomeric theory has been applied in physiology by King (1950) and King and Lawton (1950). A review of their analysis was given by Stacy et al. (1955). More recently, the mechanical characterization of polyurethane elastomer for biomedical applications has been reported (Kanyanta and Ivankovic, 2010).
Baroreceptors: Morphology and Mechanics of Receptor Zones and Discharge Properties of Baroafferents*
Published in Irving H. Zucker, Joseph P. Gilmore, Reflex Control of the Circulation, 2020
I have reviewed in some detail the viscoelastic properties of arteries in order to caution against premature conclusions about the tension–strain relations of the geometrically and structurally rather complex carotid sinus receptor regions where the assumptions underlying the incremental approaches (isotropy, homogeneity of the vessel wall) are no longer valid. These obstacles can possibly be circumvented by using “strain energy density” per wall volume as a scalar quantity for expressing wall deformation. This approach derives from finite deformation theory and has been applied to describing the behavior of elastomers. It relates the work done on the wall (volume–pressure relations) to wall deformation in all directions, and requires information about wall volume, pressure, length, and diameter. Strain energy density of the carotid sinus wall follows both circumferential and longitudinal stretch but continues to increase above 200 mmHg when length has already reached its plateau (Koushanpour and Kelso, 1972).
Developing a process for assessing equivalency of wheelchair cushion pressure redistribution performance
Published in Assistive Technology, 2020
Stephen Sprigle, Steven Pubillones
Future work. This work represents early effort in the potential development of a test method for measuring cushion performance with the intent of establishing thresholds for defining equivalency of cushions with similar performance. Most importantly, the value of measuring stress and strain as a reflection of wheelchair cushion performance must be evaluated. Relatedly, the value of defining cushion equivalency must be assessed. The development of such a test method requires addressing myriad issues related to instrumentation, procedures and data analysis. With respect to instrumentation, the use of a compliant indentor must be addressed as its use is more complicated than that of a rigid model. This includes assessment of whether and how the mechanical properties of the elastomer changes over time. If properties change in a manner that impacts stress and strain measurements, the indentor will have to have a defined useful life, after which it must be retired. Testing procedures must address factors such as the conditioning of cushions prior to testing, the load and time parameters used during testing and the number of trials needed to report reliable stress and strain measurements. The means by which stress and strain measurements are analyzed with respect to equivalency must be studied and finalized. Multiple equivalency options have been presented, all of which have benefits and drawbacks.
Vaginal multipurpose prevention technologies: promising approaches for enhancing women’s sexual and reproductive health
Published in Expert Opinion on Drug Delivery, 2020
Trinette Fernandes, Krishna Baxi, Sujata Sawarkar, Bruno Sarmento, José das Neves
Vaginal rings are polymeric, flexible, torus-shaped devices intended to be placed in the vagina and provide sustained drug release from a few days to several months. Different products based on vaginal rings have been available since the 1990s, particularly for hormonal contraception. A recent systematic review of data from randomized controlled clinical trials and observational studies found that rings are widely accepted by women in low- and middle-income countries, although issues related to sex intercourse, cognitive/emotional burden, and unintentional expulsion from the vagina may negatively impact use [105]. The type of polymer used for producing rings is an important factor which governs various characteristics like flexibility, ease of administration, and release kinetics. Commonly used materials are silicone elastomers, ethylene/vinyl acetate copolymers, and polyurethanes. Rings can feature various designs, but the two simplest designs (in which commercially available rings are based on) are the matrix and reservoir systems. Their engineering is crucial in order to determine drug release kinetics. More recently, variations to more traditional designs have been developed including segmented matrix, segmented reservoir, multicore, sandwich, tablet insert, and pod insert ring designs [50,106].
Biomimetic hydroxyapatite/poly xylitol sebacic adibate/vitamin K nanocomposite for enhancing bone regeneration
Published in Artificial Cells, Nanomedicine, and Biotechnology, 2019
Zhipeng Dai, Minyan Dang, Wenzhi Zhang, Sumathra Murugan, Seoh Wei Teh, Haiyan Pan
Poly-condensation reaction was applied to synthesize PXSA. A prepolymer was formed by stirring xylitol, sebacic acid and adipic acid in a round bottom flask for 1 h at 140 °C under nitrogen gas blanket. The mixture was heated further at 150 °C and condensation of h was continued for another 5 h to obtain the PXSA polymer. The formed product gradually showed increasing viscosity with increased reaction time. The cross-linked elastomer was applied for further characterization. Ester bond formed between monomers of sebacic acid, xylitol and adipic acid was verified through FTIR analysis. Upon confirmation, 10 wt% of PXSA polymer were mixed with pure HAP and heated for ∼10 min in microwave oven (2.5 GHz, LG, India) at 720 W to form HAP/PXSA composite.