Vortices in vibrated granular rods

We report the experimental observation of novel vortex patterns in vertically vibrated granular rods. Above a critical packing fraction, moving ordered domains of nearly vertical rods spontaneously form and coexist with horizontal rods. The domains of vertical rods coarsen in time to form large vortices. We investigate the conditions under which the vortices occur by varying the number of rods, vibration amplitude and frequency. The size of the vortices increases with the number of rods. We characterize the growth of the ordered domains by measuring the area fraction of the ordered regions as a function of time. A {\em void filling} model is presented to describe the nucleation and growth of the vertical domains. We track the ends of the vertical rods and obtain the velocity fields of the vortices. The rotation speed of the rods is observed to depend on the vibration velocity of the container and on the packing. To investigate the impact of the direction of driving on the observed phenomena, we performed experiments with the container vibrated horizontally. Although vertical domains form, vortices are not observed. We therefore argue that the motion is generated due to the interaction of the inclination of the rods with the bottom of a vertically vibrated container. We also perform simple experiments with a single row of rods in an annulus. These experiments directly demonstrate that the rod motion is generated when the rods are inclined from the vertical, and is always in the direction of the inclination.Comment: 6 pages, 10 figure, 2 movies at http://physics.clarku.edu/vortex uses revtex

Downstream green processes for recovery of bioactives from algae

Nowadays, macro- and microalgae are being increasingly used as promising raw materials for the food, cosmetic and pharmaceutical industries, thanks to their biodiversity and its variety on valuable bioactive compounds such as carbohydrates, polyunsaturated lipids, proteins and pigments, among others. Furthermore, more efficient and environmentally friendly processes for bioactives’ recovery are requested not only by the industry but also by the society. This chapter presents an overview on the use of downstream green processes, mainly based on compressed fluids extraction techniques, in order to recover bioactives from algae that can be lately used in several potential applications for the food, pharmaceutical and cosmetic industries, which is the pillar of algae-based biorefinery.Peer reviewe

Nanotechnology and Plant Extracts as a Future Control Strategy for Meat and Milk Products

Plant extracts, well known for their antibacterial and antioxidant activity, have potential to be widely used preservatives in the food industry as natural alternatives to numerous synthetic additives which have adverse impacts on health and the environment. Most plant compounds and extracts are generally recognized as safe (GRAS). The use of preservatives is of great importance for perishable foods such as meat and milk, which, along with their products, are commonly consumed food items globally. However, the bioavailability of plant compounds could be diminished by their interaction with food components, processing, and storage. Nanoencapsulation of plant extracts, especially essential oils, is an effective method for their application in food model systems. This technique increases the bioactivity of plant compounds by increasing their physical stability and reducing their size, without negative effects on organoleptic properties. Furthermore, a recent study showed that plant extracts act as good bioreductants for biosynthesis of nanoparticles. This so-called green synthesis method using plant extracts is a rapid, relatively inexpensive, safe, and efficient method for synthesis of nanoparticles including silver, gold, iron, lead, copper, cobalt, palladium, platinum, zinc, zinc oxide, titanium oxide, magnetite, and nickel. Some of these nanoparticles have antimicrobial potential which is why they are of great interest to the food industry. In this chapter, the nanoencapsulation of plant extracts and plant extract-mediated synthesis of nanoparticles and their potential application in order to improve the safety and quality and prolong the shelf life of meat and milk products are reviewed and discussed