Relational components of three attributes often regarded as individual variables (conflict, autonomy, and self-regulation) were examined in two studies. In Study 1, mothers and their 10-through 12-, 13-through 15-, or 16-through 17-year-old offspring reported expected times of transition to 47 adultlike behaviors (behavioral autonomy) and rated the importance of delaying each transition. Discrepancies from mothers' expectancies were found to be greatest for 13-through 15-year-olds. In Study 2, characteristics and correlates of conflict across different types of relationships were assessed. Sixth-grade and eighth-grade Hispanic American adolescents reported significant differentiation among relationships with mothers, fathers, and friends in frequency of conflict, conflict resolution strategies and sequelae, and correlates of adolescents'psychosocial competence. Variations suggest that multiple relationships may be involved in the development of autonomy and self-regulation during childhood and adolescence. Conflict, autonomy, and self-regulation long have been central to theory and research on adolescent development. For the most part, however, these terms have been embedded in individualistic views of ontogenetic change (Cooper, 1994). Autonomy has been regarded as a process of striving to gain freedom from parents and other influences (for a review, see Hill & Holmbeck, 1986); self-regulation, as a function of intrapsychic conflicts or internalization of external contingencies (for a review, see Kuczynski, 1995); and conflict, as a manifestation of intrapsychic turbulence and autonomy striving that were necessary components of separation from parents (e.g., Blos, 1979;Freud, 1969).
The reinforcement of polymer nanocomposites can be achieved through alignment or percolation of cellulose nanocrystals (CNCs). Here, we compare the efficacy of these reinforcement mechanisms in thermoplastic polyurethane (PU) elastomer nanocomposites containing thermally stable cotton CNCs. CNC alignment was achieved by melt spinning nanocomposite fibers, while a percolating CNC network was generated by solvent casting nanocomposite films with CNC contents up to 20 wt %. While in films both the CNCs and the PU matrix were entirely isotropic at all concentrations as confirmed by wide-angle X-ray scattering and birefringence analysis, the CNCs in the fibers exhibited a preferential orientation, which improved with increasing CNC concentration. Increasing the CNC concentration in the fibers reduces, however, the alignment of the PU chains, resulting in an entirely isotropic PU matrix at high CNC contents. The mechanical properties of films and fibers were evaluated using stress− strain measurements. Nanocomposite fibers with low CNC content exhibited superior stiffness, extensibility, and strength compared to the films, while the films displayed superior mechanical properties at high CNC concentrations. These findings are rationalized using common semiempirical models describing the reinforcing effects of CNC alignment in fibers (Halpin−Tsai) and CNC percolation in films (percolation model). The formation of a percolating CNC network leads to a stronger reinforcement than CNC alignment, as the reinforcing effect of the latter is limited by the comparably low aspect ratio of CNCs extracted from cotton. As a consequence, above the percolation threshold for cotton CNCs, isotropic nanocomposite PU films show a higher stiffness than aligned nanocomposite PU fibers.
Drug-diffusion kinetics in 2-hydroxyethyl methacrylate hydrogels were studied as a function of the crosslinking density and porosity. By varying the concentration of the crosslinker, tetraethylene glycol dimethacrylate, we demonstrated how the release of Timolol maleate could be optimized to allow for efficient drug delivery. FTIR and spectrophotometry supplied optical inferences into the functional groups present. By studying the swelling and degradation of hydrogels, supplemented with drug-release kinetics studies, the relationship between these two tenets could be formulated.
Molecular imprinted hydrogels can be made to have a high affinity for a certain compound or drug. A hydrogel can be loaded with a drug and upon a swelling action induced by a pH change or hydration process, the matrix can swell and release the drug. Our hydrogels mimic contact lenses for the purposes of ocular drug delivery. Our hydrogels were imprinted and tested with a prostaglandin derivative, bimatoprost used in the treatment for glaucoma. Major problems preventing entrance to clinical use are bioavailability and drug release kinetics. Our lenses were made to overcome these issues, and were tested for efficacy. The gels were synthesized and were tested to establish a clinically relevant drug delivery profile. Using UV-Vis Spectrophotometry we analyzed the drug released from the gels before, and after cycling. They show a desired and consistent dose release, and a kinetic profile that would indicate a large bioavailability. The testing would also indicate a strong reusability potential, as the hydrogels can release the same amount of drug for over 10,000 cycles (to simulate a daily use). Our samples were tested to show a 10 hour dose release time and they were able to withstand over 10,000 cycles of a swelling mechanical force without degradation or drug release alteration. We imaged the hydrogel lenses with an SEM to visualize if the matrix encountered deterioration over time due to the drug release mechanism. This is due to a need to understand long term use stability. The test results indicate a strong potential to be able to enter the market and be approved for clinical use.
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