Hydrophobic CuO Nanosheets Functionalized with Organic Adsorbates.

A new class of hydrophobic CuO nanosheets is introduced by functionalization of the cupric oxide surface with p-xylene, toluene, hexane, methylcyclohexane, and chlorobenzene. The resulting nanosheets exhibit a wide range of contact angles from 146° (p-xylene) to 27° (chlorobenzene) due to significant changes in surface composition induced by functionalization, as revealed by XPS and ATR-FTIR spectroscopies and computational modeling. Aromatic adsorbates are stable even up to 250-350 °C since they covalently bind to the surface as alkoxides, upon reaction with the surface as shown by DFT calculations and FTIR and 1H NMR spectroscopy. The resulting hydrophobicity correlates with H2 temperature-programmed reduction (H2-TPR) stability, which therefore provides a practical gauge of hydrophobicity.

How dynamic adsorption controls surfactant-enhanced boiling.

Improving boiling is challenging due to the unpredictable nature of bubbles. One way to enhance boiling is with surfactants, which alter the solid-liquid and liquid-vapor interfaces. The conventional wisdom established by previous studies suggests that heat transfer enhancement is optimized near the critical micelle concentration (CMC), which is an equilibrium property that depends on surfactant type. However, these studies only tested a limited number of surfactants over small concentration ranges. Here, we test a larger variety of nonionic and anionic surfactants over the widest concentration range and find that a universal, optimal concentration range exists, irrespective of CMC. To explain this, we show that surfactant-enhanced boiling is controlled by two competing phenomena: (1) the dynamic adsorption of surfactants to the interfaces and (2) the increase in liquid dynamic viscosity at very high surfactant concentrations. This dynamic adsorption is time-limited by the millisecond-lifetime of bubbles on the boiling surface-much shorter than the timescales required to see equilibrium behaviors such as CMC. At very high concentrations, increased viscosity inhibits rapid bubble growth, reducing heat transfer. We combine the effects of adsorption and viscosity through a simple proportionality, providing a succinct and useful understanding of this enhancement behavior for boiling applications.

Consumption of energy beverage is associated with attenuation of arterial endothelial flow-mediated dilatation.

AIM: To investigate whether consumption of an energy drink will acutely impair endothelial function in young healthy adults. METHODS: Energy drinks are being consumed more and more worldwide, and have been associated with some deaths in adolescents and young adults, especially when consumed while exercising. After fasting and not smoking for at least 8 h prior, eleven medical students (9 males) received an electrocardiogram, blood pressure and pulse check, and underwent baseline testing (BL) of endothelial function using the technique of endothelium-dependent flow mediated dilatation (FMD) with high-resolution ultrasound (according to recommended guidelines of the University of Wisconsin Atherosclerosis Imaging Research Program Core Laboratory). The subjects then drank an energy beverage (EB), a 24-oz can of Monster Energy, and the above was repeated at 90 min after consumption. The relative FMD (%) was calculated as the ratio between the average post-cuff release and the baseline diameter. Each image was checked for quality control, and each artery diameter was measured from the media to media points by two experts, 3 measurements at the QRS complex, repeated on 3 separate beats, and then all were averaged. RESULTS: Subjects characteristics averages (given with standard deviations) include: Age 24.5 ± 1.5 years, sex 9 male and 2 female, weight 71.0 ± 9.1 kg, height 176.4 ± 6.0 cm, BMI 22.8 ± 2.7 kg/m2. The hemodynamics were as follows, BL vs EB group respectively (mean ± SD): Heart rate 65.2 ± 11.3 vs 68.2 ± 11.8 beats per minute, systolic blood pressure 114.0 ± 10.4 mmHg vs 114.1 ± 10.4 mmHg, diastolic blood pressure 68.8 ± 9.3 mmHg vs 70.6 ± 7.1 mmHg; all were not significantly different. However after drinking the EB, a significantly attenuated peak FMD response was measured (mean ± SD): BL group 5.9% ± 4.6% vs EB group 1.9% ± 2.1%; P = 0.03). Given the increased consumption of energy beverages associated with exercise in young adults, more research is needed. CONCLUSION: Energy beverage consumption has a negative impact on arterial endothelial function in young healthy adults.