Fabrication,characterization, cytocompatibility,and biological activity of lemon fiber-filled polyester composites

The structure, cytocompatibility, and biological activity of composites prepared from polycaprolactone (PCL) and lemon fiber (LF) blends (PCL/LF) were evaluated. Acrylic acid-grafted PCL (PCL-g-AA) was used to enhance the desirable characteristics of these composites, which had better tensile properties than the corresponding PCL/LF composites. A cytocompatibility evaluation with normal human foreskin fibroblasts of the water released from the PCL/LF and PCL-g-AA/LF composites indicated that both materials were nontoxic. Moreover, LF enhanced the flavonoid and polyphenol contents and the anti-inflammatory and antioxidant properties of the PCL-g-AA/LF and PCL/LF composites. We analyzed the effects of these composites in mushroom tyrosinase activity and B16-F10 melanoma cells; the PCL/LF and PCL-g-AA/LF membranes demonstrated reduced tyrosinase activity. Composites of PCL-g-AA or PCL containing LF had better antibacterial activity.     

Enhancement in interfacial reactive compatibilization by chain mobility

This study investigates the role of polymer chain mobility, through the addition of a plasticizer, N-butylbenzene sulfonamide (BBSA), on the overall blending dynamics and interfacial copolymer chain formation in the reactive blending of brominated poly(isobutylene-co-p-methylstyrene) (BIMSM) and polyamide (PA). Compared to a non-reactive poly(isobutylene-co-p-methylstyrene) (IMSM)/PA blend, the reactive BIMSM/PA blend demonstrates a rapid, order of magnitude increase in viscosity, and attains a plateau viscosity at higher temperatures. The addition of a BBSA plasticizer (5–10 wt%) surprisingly increases the viscosity even further, suggesting an enhancement in interfacial reaction due to increased chain mobility. It is also found to increase the level of grafting from about 46 to 57% and has a significant influence on the morphology of the blend system. It is shown that the reactive grafting has an onset at lower temperatures for the blend system with 10 and 43% plasticizer. The morphologies of the blends with 5–10% plasticizer have a more uniform distribution (d_v/d_n) with a reduced d_v for the dispersed BIMSM particles. At 43 wt% plasticizer the blends show an increased phase size resulting from the significantly enhanced phase coalescence. These results indicate that enhanced chain mobility through plasticizer usage can impact interfacial compatibilization and phase coalescence and that a threshold level of 5–10 wt% plasticizer provides an optimum level of chain mobility for this reactive blending system.     

Effect of water aging on the apatite formation of a low-modulus Ti–7.5Mo alloy treated with aqueous NaOH

The objective of this experiment was to develop biomimetic calcium phosphate coatings on low-modulus Ti–7.5Mo substrates treated with NaOH aqueous solutions and subsequent water aging before soaking them in simulated body fluid (SBF). Specimens of commercially pure titanium (c.p. Ti) and Ti–7.5Mo were initially treated with 5 M NaOH at 60 °C for 24 h, resulting in the formation of a porous network structure composed of sodium titanate (Na₂Ti₅O₁₁). Afterward, the specimens were aged in distilled water at 80 °C for 12, 24, or 48 h, and subsequently immersed in 1.5SBF at 37 °C for either 1 or 13 days. The calcium phosphate-forming abilities of the c.p. Ti and Ti–7.5Mo achieved by a single NaOH treatment were low, but were significantly increased by the water aging. The amount of calcium phosphate deposited on the Ti–7.5Mo after NaOH treatment and subsequent water aging for 12 or 24 h was much greater than other conditions. The calcium phosphate-coated Ti–7.5Mo has strong potential as an artificial bone substitute or in other hard tissue-replacement materials with heavy load-bearing requirements due to a favorable combination of bioactivity, low elastic modulus, and low processing costs.     

Mapping nanoscale elasticity and dissipation using dual frequency contact resonance AFM

We report on a technique that simultaneously quantifies the contact stiffness and dissipation of an AFM cantilever in contact with a surface, which can ultimately be used for quantitative nanomechanical characterization of surfaces. The method is based on measuring the contact resonance frequency using dual AC resonance tracking (DART), where the amplitude and phase of the cantilever response are monitored at two frequencies on either side of the contact resonance. By modelling the tip-sample contact as a driven damped harmonic oscillator, the four measured quantities (two amplitudes and two phases) allow the four model parameters, namely, drive amplitude, drive phase, resonance frequency and quality factor, to be calculated. These mechanical parameters can in turn be used to make quantitative statements about localized sample properties. We apply the method to study the electromechanical coupling coefficients in ferroelectric materials and the storage and loss moduli in viscoelastic materials.     

Post-interdisciplinary frames of reference: exploring permeability and perceptions of disciplinarity in the social sciences

The ProQuest Dissertations and Theses database contains records for approximately 2.3 million dissertations conferred at 1,490 research institutions across 66 countries. Despite the scope of the Dissertations and Theses database, no study has explicitly sought to validate the accuracy of the ProQuest SCs. This research examines the degree to which ProQuest SCs serve as proxies for disciplinarity, the relevance of doctoral work to doctoral graduates’ current work, and the permeability of disciplines from the perspective of the mismatch between SCs and disciplinarity. To examine these issues we conducted a survey of 2009–2010 doctoral graduates, cluster-sampled from Economics, Political Science, and Sociology ProQuest SCs. The results from the survey question the utility of traditional disciplinary labels and suggest that scholars may occupy a post-interdisciplinary space in which they move freely across disciplinary boundaries and identify with topics instead of disciplines.     

Concurrent assessment of personal,indoor, and outdoor PM2.5 and PM1 levels and source contributions using novel low-cost sensing devices

The intensity, frequency, duration, and contribution of distinct PM_2.5 sources in Asian households have seldom been assessed; these are evaluated in this work with concurrent personal, indoor, and outdoor PM_2.5 and PM₁ monitoring using novel low-cost sensing (LCS) devices, AS-LUNG. GRIMM-comparable observations were acquired by the corrected AS-LUNG readings, with R² up to 0.998. Twenty-six non-smoking healthy adults were recruited in Taiwan in 2018 for 7-day personal, home indoor, and home outdoor PM monitoring. The results showed 5-min PM_2.5 and PM₁ exposures of 11.2 ± 10.9 and 10.5 ± 9.8 µg/m³, respectively. Cooking occurred most frequently; cooking with and without solid fuel contributed to high PM_2.5 increments of 76.5 and 183.8 µg/m³ (1 min), respectively. Incense burning had the highest mean PM_2.5 indoor/outdoor (1.44 ± 1.44) ratios at home and on average the highest 5-min PM_2.5 increments (15.0 µg/m³) to indoor levels, among all single sources. Certain events accounted for 14.0%-39.6% of subjects’ daily exposures. With the high resolution of AS-LUNG data and detailed time-activity diaries, the impacts of sources and ventilations were assessed in detail.     

Expression of retinoid X receptors in human dermal fibroblasts

Retinoic acid (RA) is known to exert profound effects on growth and differentiation in human dermal fibroblasts. In the observations presented here, we examined the regulation of expression of members of the RXR multigene family in human dermal fibroblasts. We showed that the messenger RNAs for both RXR alpha and RXR beta are expressed in human fibroblasts, but that the messenger RNA for RXR gamma is not detectable in these cells. Electrophoretic mobility shift studies of binding to the beta 2RARE in human dermal fibroblasts demonstrated that a single complex binds to beta 2RARE in the absence of RA. Stimulating cells with all-trans RA induced a second complex. An antibody to the RXR beta protein supershifted both complexes, while an antibody to the RXR alpha S/B protein had no effect on the binding. These data demonstrate that RXR beta plays an important role in retinoid-regulated signal transduction pathways in human dermal fibroblasts and the regulation of expression of the RXR gene family is different from that of the RAR gene family.