Adolescent HIV Pre Exposure Prophylaxis Prescribing Practices Among Family Medicine Physicians: Limited Immediate Uptake

This study aims to: Examine the adolescent PrEP prescribing practices and knowledge of family medicine physicians. Begin to identify areas that might be key targets for interventions which may lead to increased adolescent PrEP prescribing uptake.https://jdc.jefferson.edu/fmposters/1005/thumbnail.jp

The internal structure of poly(methyl methacrylate) latexes in nonpolar solvents

Hypothesis: Poly(methyl methacrylate) (PMMA) latexes in nonpolar solvents are an excellent model system to understand phenomena in low dielectric media, and understanding their internal structure is critical to characterizing their performance in both fundamental studies of colloidal interactions and in potential industrial applications. Both the PMMA cores and the poly(12-hydroxystearic acid) (PHSA) shells of the latexes are known to be penetrable by solvent and small molecules, but the relevance of this for the properties of these particles is unknown. Experiments: These particles can be prepared in a broad range of sizes, and two PMMA latexes dispersed in n-dodecane (76 and 685 nm in diameter) were studied using techniques appropriate to their size. Small-angle scattering (using both neutrons and X-rays) was used to study the small latexes, and analytical centrifugation was used to study the large latexes. These studies enabled the calculation of the core densities and the amount of solvent in the stabilizer shells for both latexes. Both have consequences on interpreting measurements using these latexes. Findings: The PHSA shells are highly solvated (∼85% solvent by volume), as expected for effective steric stabilizers. However, the PHSA chains do contribute to the intensity of neutron scattering measurements on concentrated dispersions and cannot be ignored. The PMMA cores have a slightly lower density than PMMA homopolymer, which shows that only a small free volume is required to allow small molecules to penetrate into the cores. Interestingly, the observations are essentially the same, regardless of the size of the particle; these are general features of these polymer latexes. Despite the latexes being used as a model physical system, the internal chemical structure is complex and must be fully considered when characterizing them

Poly(dimethylsiloxane)-Stabilized Polymer Particles from Radical Dispersion Polymerization in Nonpolar Solvent: Influence of Stabilizer Properties and Monomer Type

Particles used in electrophoretic display applications (EPD) must possess a number of specific properties ranging from stability in a nonaqueous solvent, high reflectivity, low polydispersity, and high charge density to name but a few. The manufacture of such particles is best carried out in the solvent of choice for the EPD. This opens up new interests in the study of nonaqueous dispersion polymerization methods, which deliver polymer particles suspended in low dielectric constant solvents. We explore in this article the use of a poly(dimethylsiloxane) macromonomer for the stabilization of poly(methyl methacrylate) polymer particles in dodecane, a typical solvent of choice for EPDs. The use of this stabilizer is significant for this method as it is directly soluble in the reaction medium as opposed to traditionally used poly(12-hydroxystearic acid)-based stabilizers. Additionally, the present study serves as a baseline for subsequent work, where nonaqueous dispersion polymerization will be used to create polymer particles encapsulating liquid droplets and solid pigment particles. In this article, the influence of the macromonomer molecular weight and concentration on the properties of the synthesized particles is studied. In addition, we investigate the possibility of synthesizing polymer particles from other monomers both as a comonomer for methyl methacrylate and as the only monomer in the process. The influence of macromonomer concentration is also studied throughout all experiments

Surfactants with colloids: Adsorption or absorption?

The interaction of Aerosol OT (AOT) surfactant with systems of model colloids in nonaqueous solvents (water-in-oil microemulsions, surfactant-stabilized silica organosols, and sterically-stabilized PMMA latexes) is expected to be system specific. Two limiting cases are expected: adsorption, with surfactant located at the particle surfaces, or absorption, with surfactant incorporated into the particle cores. Experiments: Two approaches have been used to determine how AOT is distributed in the colloidal systems. The stability of the colloids in different alkanes (heptane to hexadecane, including mixtures) has been studied to determine any effects on the colloid surfaces. Contrast-variation small-angle neutron scattering (SANS) measurements of the colloid cores and of AOT-colloid mixtures in colloid-matched solvent have also been performed. Normalization to account for the different scattering intensities and different particle radii have been used to enable a system-independent comparison. Findings: AOT in water-in-oil microemulsions and surfactant-stabilized silica organosols is determined to be adsorbed, whereas, surprisingly, AOT in sterically-stabilized PMMA latexes is found to be absorbed. Possible origins of these differences are discussed

Sexual Behavior Patterns and PrEP Dosing Preferences in a large sample of North American Men who have Sex with Men

Pre-exposure prophylaxis (PrEP), taken as a single daily co-formulated pill containing tenofovir-emtricitabine, is a promising intervention to reduce the likelihood of HIV acquisition in at-risk individuals, including men who have sex with men (MSM). Little is known about the acceptability of less than daily, intermittent PrEP (iPrEP) regimens. We conducted an online survey of North American MSM to characterize their sexual frequency and planning behaviors and correlate these with PrEP dosing preferences. Of the 3,217 respondents who completed the survey, 46% reported engaging in unplanned condomless anal intercourse (CAI) at least once in the prior 3 months and 8% reported engaging in CAI more than once per week. In multivariable analysis, reporting unplanned CAI was associated with lower educational level, identifying as homosexual/gay as compared to bisexual, being in a monogamous relationship, having a higher self-perceived risk of HIV acquisition, higher income, engaging in CAI more than five times in the last 3 months, and not having visited a healthcare provider in the previous year. Frequent CAI (>1×/week) was associated with being younger, identifying as homosexual/gay as compared to bisexual, being in a monogamous relationship, and having a higher self-perceived risk of HIV. Having had only planned sex over the last 3 months was associated with a preference for event-based PrEP, while having frequent or unplanned CAI was associated with a preference for daily or time-driven PrEP regimens, respectively. Our findings suggest that preferences for different PrEP regimens are associated with the sexual frequency and planning behaviors of potential users