The Post-Curing of Waterborne Polyurethane-Acrylate Composite Latex with the Dynamic Disulfide-Bearing Crosslinking Agent.

The development of a dynamic network for commodity polymer systems via feasible methods has been explored in the context of a society-wide focus on the environment and sustainability. Herein, we demonstrate an adaptive post-curing method used to build a self-healable network of waterborne polyurethane-acrylate (WPUA) composite latex. The composite latex was synthesized via the miniemulsion polymerization of acrylates in the dispersion of waterborne polyurethane (PU), with commercial acetoacetoxyethyl methacrylate (AAEM) serving as the functional monomer. Then, a dynamic disulfide (S-S)-bearing diamine was applied as the crosslinking agent for the post-curing of the hybrid latex via keto-amine condensation, which occurred during the evaporation of water for film formation. It was revealed that the microphase separation in the hybrid films was suppressed by the post-curing network. The mechanical performance exhibited a high reliability as regards the contents of the crosslinking agents. The reversible exchange of S-S bonds meant that the film displayed associative covalent-adaptive networks in the range of medium temperature in stress relaxation tests, and ≥95% recovery in both the stress and the strain was achieved after the cut-off films were self-healed at 70 °C for 2 h. The rebuilding of the network was also illustrated by the >80% recovery in the elongation at break of the films after three crushing-hot pressing cycles. These findings offer valuable insights, not only endowing the traditional WPUA with self-healing and reprocessing properties, but broadening the field of study of dynamic networks to polymer hybrid latex.

The Multi-Step Chain Extension for Waterborne Polyurethane Binder of Para-Aramid Fabrics.

The comprehensive balance of the mechanical, interfacial, and environmental requirements of waterborne polyurethane (WPU) has proved challenging, but crucial in the specific application as the binder for high-performance polymer fiber composites. In this work, a multi-step chain extension (MCE) method was demonstrated using three kinds of small extenders and one kind of macro-chain extender (CE) for different chain extension steps. One dihydroxyl blocked small molecular urea (1,3-dimethylolurea, DMU) was applied as one of the CEs and, through the hybrid macrodiol/diamine systems of polyether, polyester, and polysiloxane, the WPU was developed by the step-by-step optimization on each chain extending reaction via the characterization on the H-bonding association, microphase separation, and mechanical properties. The best performance was achieved when the ratio of polyether/polyester was controlled at 6:4, while 2% of DMU and 1% of polysiloxane diamine was incorporated in the third and fourth chain extension steps, respectively. Under the condition, the WPU exhibited not only excellent tensile strength of 30 MPa, elongation of break of about 1300%, and hydrophobicity indicated by the water contact angle of 98°, but also effective interfacial adhesion to para-aramid fabrics. The peeling strength of the joint based on the polysiloxane incorporated WPU after four steps of chain extension was 430% higher than that prepared through only two steps of chain extension. Moreover, about 44% of the peeling strength was sustained after the joint had been boiling for 40 min in water, suggesting the potential application for high-performance fabric composites.

Cyclopentenone-Containing Tetrahydroquinoline and Geldanamycin Alkaloids from Streptomyces malaysiensis as Potential Anti-Androgens against Prostate Cancer Cells.

Malaymycin (1), a new cyclopentenone-containing tetrahydroquinoline alkaloid, and mccrearamycin E (2), a geldanamycin analogue bearing a rare ring-contracted cyclopentenone moiety, and a C2-symmetric macrodiolide (7) were isolated from Streptomyces malaysiensis SCSIO41397. Their structures including absolute configurations were determined by detailed analyses of NMR and HRMS data and ECD calculations. The occurrence of mccrearamycin E (2) bearing a ring-contracted cyclopentenone is rare in the geldanamycin class. All isolated compounds were evaluated for their cytotoxicities against five cancer cell lines. As a result, compounds 1, 4, 5, and 7 showed cytotoxicity against some or all of the five cancer cell lines with IC50 values ranging from 0.067 to 7.2 µM. In particular, compound 1 inhibited the growth of C42B and H446 cell lines with IC50 values of 67 and 70 nM, respectively. Malaymycin (1) significantly induced cell cycle arrest at the G0/G1 phase in C42B cell lines and caused cell shrinkage and inhibited the expression of the androgen receptor (AR) at both the mRNA and protein levels in a dose-dependent manner. Further examination by qRT-PCR analysis showed that 1 strongly suppressed the expression of AR target genes KLK2 and KLK3 in the C42B and 22RV1 cell lines, which suggested that 1 might be a promising potential lead compound for the development of a treatment for the castration-resistant prostate cancer (CRPC).

Cell Phones, Sexual Behaviors and HIV Prevalence in Rakai, Uganda: A Cross Sectional Analysis of Longitudinal Data.

Cell phones have increased communication and connection across the globe and particularly in sub-Saharan Africa-with potential consequences for the HIV epidemic. We examined the association among ownership of cell phones, sexual behaviors (number of sexual partners, alcohol use before sex, inconsistent condom use), and HIV prevalence. Data were from four rounds (2010-2016) of the Rakai Community Cohort Study (N = 58,275). Sexual behaviors and HIV prevalence were compared between people who owned a cell phone to people who did not own a cell phone. We stratified analysis by younger (15-24 years) and older (25+ years) age groups and by gender. Using logistic regression and after adjusting for sociodemographic characteristics, we found cell phone ownership was independently associated with increased odds of having two or more sexual partners in the past 12 months across age and gender groups (young men AOR 1.67, 95% CI 1.47-1.90; young women AOR 1.28 95% CI 1.08-1.53; older men AOR 1.54 95% CI 1.41-1.69; older women AOR 1.44 95% CI 1.26-1.65). Interestingly, young men who owned cell phones had decreased odds of using condoms inconsistently (AOR 0.66, 95% CI 0.57-0.75). For young women, cell phone ownership was associated with increased odds of using alcohol before sex (AOR 1.38 95% CI 1.17-1.63) and increased odds of inconsistent condom use (AOR 1.40, 95% 1.17-1.67). After adjusting for sociodemographic characteristics, only young women who owned cell phones had increased odds of being HIV positive (AOR 1.27 95% CI 1.07-1.50). This association was not mediated by sexual behaviors (Adjusted for sociodemographic characteristics and sexual behaviors AOR 1.24, 95% CI 1.05-1.46). While cell phone ownership appears to be associated with increased HIV risk for young women, we also see a potential opportunity for future cell phone-based health interventions.