Nanostructure on taro leaves resists fouling by colloids and bacteria under submerged conditions

The antifouling and self-cleaning properties of plants such as Nelumbo nucifera (lotus) and Colocasia esculenta (taro) have been attributed to the superhydrophobicity resulting from the hierarchical surface structure of the leaf and the air trapped between the nanosized epicuticular wax crystals. The reported study showed that the nanostructures on the taro leaf surfaces were also highly resistant to particle and bacterial adhesion under completely wetted conditions. Adhesion force measurements using atomic force microscopy revealed that the adhesion force on top of the papilla as well as the area around it was markedly lower than that on the edge of an epidermal cell. The decreased adhesion force and the resistance to particle and bacterial adhesion were attributed to the dense nanostructures found on the epidermal papilla and the area surrounding it. These results suggest that engineered surfaces with properly designed nanoscale topographic structures could potentially reduce or prevent particle/bacterial fouling under submerged conditions.     

Food colloids research: Historical perspective and outlook

Trends and past achievements in the field of food colloids are reviewed. Specific mention is made of advances in knowledge and understanding in the areas of (i) structure and rheology of protein gels, (ii) properties of adsorbed protein layers, (iii) functionality derived from protein–polysaccharide interactions, and (iv) oral processing of food colloids. Amongst ongoing experimental developments, the technique of particle tracking for monitoring local dynamics and microrheology of food colloids is highlighted. The future outlook offers exciting challenges with expected continued growth in research into digestion processes, encapsulation, controlled delivery, and nanoscience.     

Reaction conducted under rather severe conditions for a colloidal catalyst - hydroformylation of propylene catalyzed by polymer-protected rhodium colloids

Hydroformylation of propylene has been conducted by a polymer-protected rhodium colloid catalyst with an activity of 130 mol butanal / g atom Rh·h. The neat colloid catalyst is stable enough for repeated use for 7 times lasting ∼50 h under the reaction condition (temperature: 363 K, pressure: 40 bar) with a total TON of 5,065 cycle / atom Rh.     

Food oral processing: Recent developments and challenges

As the very first step of food consumption, food oral processing is not only of great importance to food intake and the following digestion and adsorption, but also provides the necessary sensory attributes that please the consumer. Starting from the first bite, to oral manipulation including mastication and transportation, until bolus formation and swallowing, food products undergo a variety of physical and biochemical changes over a wide range of time and length scales. A number of efforts had been made to uncover the mechanisms in each oral processing step; some of which are still poorly understood. This review covers some of the most recent progress made in the area of food oral processing, with an emphasis on eating and swallowing difficulties in the elderly and the corresponding model food development. It also includes the oral surface coating and lubrication and the dynamic textural perception during food oral processing. The authors hope that this will facilitate food scientists, psychologists, dentists and other clinical researchers to further understand and reveal the detailed controlling mechanisms and governing principles of food oral processing.     

Preparation and characterization of silver colloids with different morphologies under ultrasonic field

In the ultrasonic field, stable silver colloids were produced by the reduction of AgNO₃ with the protection of PVP using KBH₄ or N₂H₄·H₂O as reductant. The main factors affecting the morphology of silver nanoparticles, such as distribution of the ultrasonic field, ultrasonic time, ultrasonic power, and the species of reductant, were studied. The silver colloids were identified by TEM and spectrophotometry. The results indicate that the factors such as distribution of the ultrasonic field, ultrasonic time, ultrasonic power, and the species of reductant have a great impact on the morphology of the silver nanoparticles. The size of the silver nanoparticles decreases with the ultrasonic power and ultrasonic time increasing. Ag nanoparticles prepared in standing wave field preferentially grow in a certain direction, which is propitious for forming hexagonal-and spherical-like silver nanoparticles. Monodispersed spherical silver nanoparticles are easily synthesized in the diffusion field. The stability of silver colloid becomes improved by ultrasonic treatment. For example, precipitate is not found after several weeks for the silver colloid prepared with an ultrasonic treatment time of 180 min. The silver nanoparticles prepared without ultrasonic treatment are large spherical-like and hexagonal. Well-dispersed spherical silver particles with a mean size of about 20 nm have been prepared under ultrasonic treatment. Spherical, spherical-like, and hexagonal silver nanoparticles can be obtained by changing the reductants. __________ Translated from Journal of Tianjin University, 2006, 39(1) (in Chinese)     

UV-curing under oxygen-deficient conditions

Four different coating formulations have been formulated with different amounts of photoinitiator and cured under different atmospheres (21, 5, 1 and 0% of oxygen). Surface cure and through cure were assessed for each combination. It was observed that the cure process for all formulations was strongly affected by the atmospheric conditions, and that the formulations required substantially less photoinitiator if cured under 5% of oxygen if compared to curing under air. Calculations show that the lower price of the formulation due to the decreased photoinitiator level may outweigh the additional equipment and running costs in specific cases. Therefore, UV-inertisation is not only attractive from a product quality point-of-view, but can also offer economic advantages.     

Foams under dynamic conditions

This review has been focused on the importance of dynamic effects in foam formation and stability. It has been demonstrated that as foams are always formed under dynamic conditions so the equilibrium adsorption coverage's will usually not yet be attained. This fact may have a pronounced effect on the magnitude of the forces stabilizing the foam films. It has been underlined that more attention should be focused on the conditions of the foams' formation and existence because the mutual importance of the different types of the foam stabilizing forces can vary significantly depending on the stage of foam life and the conditions of its existence. Thus, none of these forces can solely determine the properties of the varying foam systems.     

Thermoresponsive magnetic colloids

The combination of magnetic nanoparticles with thermoresponsive polymer systems leads to the formation of hybrid particle dispersions or composites with a variety of interesting properties and perspectives, including instant dispensability, thermoreversible formation of magnetic fluids, and novel magnetoresponsive properties. Special interest is gained by the magnetic heatability of magnetic particles that allows the activation of thermal effects by the application of a high-frequency electromagnetic field. This review summarizes the recent developments in this young field of research with application potential for magnetic separation, drug release systems, and for sensor and actuator purposes.     

How to impose stick boundary conditions in coarse-grained hydrodynamics of Brownian colloids and semi-flexible fiber rheology

Long-range hydrodynamics between colloidal particles or fibers is modelled by the fluid particle model. Two methods are considered to impose the fluid boundary conditions at colloidal surfaces. In the first method radial and transverse friction forces between particle and solvent are applied such that the correct friction and torque follows for moving or rotating particles. The force coefficients are calculated analytically and checked by numerical simulation. In the second method a collision rule is used between colloidal particle and solvent particle that imposes the stick boundary conditions exactly. The collision rule comprises a generalisation of the Lowe-Anderson thermostat to radial and transverse velocity differences.     

Aromaticity under star dust conditions

Astronomical observations have revealed diffuse interstellar bands ranging from blue in the visible spectrum to the near IR. It has been suggested that these bands exist, owing to the presence of polyaromatic hydrocarbons or fullerene in the vicinity of certain stars, and constitute residual material from stellar explosions. The intention here is to study the relative stability of these species, when exposed to extreme conditions. The aromaticity of polycarbon molecules is an important aspect of this explanation.     

Cesium sorption under nonequilibrium conditions

Sorption of cesium on montmorillonite has been studied under nonequilibrium conditions. Depending on the initial pH of the solutions, initial fast sorption was followed by slow additional sorption (acidic region) or desorption (basic region). Dissolution of main montmorillonite constituents in acidic solutions results in progressive changes in both surface structure and charge distribution. Additional sorption may be explained by an increase of charge density at the montmorillonite/electrolyte interface. Suspensions aged in basic region revealed partial cesium desorption. The diminishing of sorptive properties is explained by the formation of secondary precipitate which may effectively coat the montmorillonite/electrolyte interface and/or readsorption of released clay constituents.     

Catalytic transamidation under moderate conditions

The carboxamide group is generally inert, except under harsh conditions or in the presence of highly evolved enzymes. We have identified several metal complexes that efficiently catalyze transamidation reactions of amide/amine mixtures under moderate conditions. This unprecedented reactivity represents an important step toward our long-term goal of using dynamic combinatorial chemistry to generate new amide-based molecules with interesting structures and functions.     

Cu-catalyzed cross-couplings under ligandless conditions

The possibility to carry out Cu-catalyzed cross-couplings under ligandless conditions was studied.It was found that by using K_3PO_4 as the base,the cross-coupling could proceed successfully between aryl iodides and several types of nucleophiles.Aryl bromides were completely inactive under the same reaction conditions.     

Accelerated glycosylation under frozen conditions

O-Glycosylations using thiomethyl glycosides as donors were compared under both frozen and unfrozen conditions. In the presence of MeOTf as a promoter, enormous rate acceleration was observed when the glycosylation was conducted in p-xylene below its freezing point.