Ultrahigh Passive Cooling Power in Hydrogel with Rationally Designed Optofluidic Properties.

The cooling power of a radiative cooler is more than halved in the tropics, e.g., Singapore, because of its harsh weather conditions including high humidity (84% on average), strong downward atmospheric radiation (∼40% higher than elsewhere), abundant rainfall, and intense solar radiation (up to 1200 W/m2 with ∼58% higher UV irradiation). So far, there has been no report of daytime radiative cooling that well achieves effective subambient cooling. Herein, through integrated passive cooling strategies in a hydrogel with desirable optofluidic properties, we demonstrate stable subambient (4-8 °C) cooling even under the strongest solar radiation in Singapore. The integrated passive cooler achieves an ultrahigh cooling power of ∼350 W/m2, 6-10 times higher than a radiative cooler in a tropical climate. An in situ study of radiative cooling with various hydration levels and ambient humidity is conducted to understand the interaction between radiation and evaporative cooling. This work provides insights for the design of an integrated cooler for various climates.

Acid-responsive properties of fibrils from heat-induced whey protein concentrate.

The heat-induced fibrils of whey protein concentrate (WPC) have demonstrated an acid-responsive property; that is, the fibrils went through formation-depolymerization-reformation as pH was adjusted to 1.8, 6.5, and back to 1.8. We investigated the microstructure, driving force, and thermal stability of 3.0% (wt) WPC nanofibrils adjusted between pH 6.5 and 1.8 twice. The results showed that the nanofibrils had acid-responsive properties and good thermal stability after reheating for 10h at 90°C and adjusting pH from 1.8 to 6.5 to 1.8. The content of WPC fibril aggregates was not much different with the prolongation of heating times during pH variation. Although the nanofibrils' structure could be destroyed only by changing the pH, the essence of this destruction might only form fiber fragments, polymers that would restore a fibrous structure upon returning to pH 1.8. A described model for the acid-responsive assembly of fibrils of WPC was proposed. The fibrils went through formation-depolymerization-reformation by weaker noncovalent interactions (surface hydrophobicity) as pH changed from 1.8 to 6.5 back to 1.8. However, the fibrils lost the acid-responsive properties because much more S-S (disulfide) formation occurred when the solution was adjusted to pH 6.5 and reheated. Meanwhile, fibrils still possessed acid-responsive properties when reheated at pH 1.8, and the content of fibrils slightly increased with a further reduction of α-helix structure.

[Effect of various storage methods on shear bond strength of enamel of bovine teeth].

PURPOSE：The purpose of this study was to evaluate the effect of various storage methods on shear bond strength of enamel of bovine teeth and find the storage condition that could preserve the similar bond strength as the freshly extracted teeth. METHODS: One hundred and thirty freshly extracted bovine teeth were divided into 13 groups. One was the reference group and 12 were the experimental group. Each group contained 10 teeth. Teeth in the reference group were operated on the same day as the teeth were extracted, while teeth in the experimental groups were stored in different methods (4% formaldehyde solution at 4 ℃, 23 ℃, 1% chloramine T at 4 ℃, 23 ℃, distilled water at 4 ℃, 23 ℃). After stored for 30 days and 90 days, the bovine teeth were taken out and then the shear bond strength was tested. The data were analyzed with SPSS 20.0 software package. RESULTS: The bovine teeth stored in 4% formaldehyde and 1% chloramine T at 23 ℃ and in distilled water at 4 ℃ achieved similar bond strength as freshly extracted teeth at 30 days and 90 days, and the bond strength did not change over time. The bovine teeth stored in 4% formaldehyde solution and 1% chloramine T at 4 ℃ at 30 days had higher shear bond strength than freshly extracted bovine teeth, but over time the bond strength reduced and reached the similar level at 90 days. The bovine teeth stored in distilled water at 23 ℃ obtained similar bond strength as freshly extracted teeth at 30 days but over time the bond strength reduced until 90 days. CONCLUSIONS: Bovine teeth stored in 4% formaldehyde solution and 1% chloramine T at 23 ℃ and in distilled water at 4 ℃ achieved similar bond strength as freshly extracted teeth and does not change over time. These three methods are recommended for storing bovine teeth.

Comparative experiments of fibril formation from whey protein concentrate with homogeneous and secondary nuclei.

Two types of special structures, homogeneous and secondary nuclei, form during fibril formation. The structural and functional properties of amyloid fibrils in whey protein concentrate (WPC) with different ratios of added homogeneous nuclei to secondary nuclei were investigated. Thioflavin T fluorescence analysis and kinetic equations indicated that two types of nuclei could accelerate WPC fibrillation compared with WPC self-assembling into amyloid fibrils, thereby reducing the lag time and increasing the number of fibrils. However, there were considerable differences in the nucleation-inducing capability of WPC fibrillation between homogeneous and secondary nuclei. The number of fibrils formed by adding homogeneous nuclei was higher than that obtained with secondary nuclei, the increase in the Th T fluorescence intensity induced by homogeneous nuclei was 1.83-fold much than secondary nuclei. Meanwhile, secondary nuclei yielded a 2.71-fold faster aggregation rate of WPC than homogeneous nuclei, particularly during the first hour of thermal treatment (protein mass ratio of nuclei to WPC 1:1). The gelation time of WPC after secondary nuclei addition was shorter, from 10 h (WPC (2.0/6.5)) to 4 h (WPC + HN) to 2 h (WPC + SN); however, the gel microstructure of WPC after the addition of homogeneous nuclei was denser, yielding a preferred water holding capacity.

The structure and amphipathy characteristics of modified γ-zeins by SDS or alkali in conjunction with heating treatment.

γ-Zein was modified by SDS or alkali combined with heating treatments in water and in 70% ethanol to change its amphipathic properties and explore the relationship between amphipathic characteristic and structure. γ-Zein water-dispersibility was dramatically increased via alkali or SDS combined with heating treatments, but their ethanol-dispersibilities were significantly different during ethanol evaporation. High both water-dispersibility and ethanol-dispersibility were found from alkali modified γ-zein while high water-dispersibility but low ethanol-dispersibility were obtained from SDS modified γ-zein, indicating that alkali modified γ-zein had better amphipathic characteristic compared with SDS modified γ-zein. Alkali modified γ-zein with higher amphipathic characteristic possessed higher structural inversion ability since it was easy to recover its native state as solvent changing from water to ethanol, contrary to SDS modified γ-zeins whose amphipathic characteristic was not improved. Moreover, the higher structural inversion ability of alkali modified γ-zein depended on the recovery capability of α-helix structure as solvent altering.