Kites offer a potential advantage over today’s wind towers in terms of material used. Wind turbine towers require concrete foundations and steel structures just to keep the turbines at the right height. [1] There are two distinct methods to harvest airborne wind energy: onboard and ground-based generation. A study by Airborne Wind Europe, a trade association, found that a 50-megawatt kite farm would use 913 metric tons of material over a 20-year lifespan, compared with 2,868 metric tons for a typical wind tower farm. Using less material could make kite-based systems both greener and cheaper to build.

[2] Kites may also prove useful for deep-water offshore wind generation. Today, when the water is too deep to build a foundation, wind turbines instead float on massive, barge-like structures that must be able to bear the turbines’ weight and keep them stable. Because kites are less massive, they could use lighter and cheaper barges.

But these advantages come at the cost of complexity. For kites to make sense economically, they need to operate for long periods and with little or no human supervision. [3] That presents a tough computerized control problem; says Chris Vermillion, director of the Control and Optimization for Renewables and Energy Efficiency Lab at North Carolina State University and an adviser to Windlift, a kite-power technology company.

The kites aren’t simply floating passively in the air. Instead, they use the aerodynamics of the kite to fly “crosswind” patterns, a bit like a boat tacking back and forth across the wind. Flying perpendicular to the direction of the wind, their wings [4] generate lift and pull even harder against the tether. This extra lift translates into extra speed, which can either pull the tether with more force for ground-based generation or be turned into greater airspeed to drive onboard turbines faster. [5 However, the power available increases by at least an order of magnitude compared to flying without the crosswind motion.

But such tricky maneuvers require constant [6] adjustment and control of the kites, by either a pilot or a computer. Rigid kites are controlled by adjusting steering components such as flaps and rudders in the same way that airplanes are flown. Soft kites are controlled by adjusting the lengths of steering lines, similar to the way a parachute is guided.

The most advanced kite systems today are capable of flying under computer control for hours or days at a time, using either onboard and on-ground computers to make constant corrections in the steering. They tend to work very well while the wind remains [7] firm, Vermillion says.

But to go mainstream, the kites will have to be able to deal dependably with sudden and unpredictable changes such as strong wind gusts. They will also need to be able to take off and land automatically, [8]so that he kite moves away from the ground station during ground-gen, unwinding the tether from a drum, which then turns a generator.

“More work needs to be done to bring the technology to the level where the operational lifespans of the devices are on the order of [9] years and decades, as opposed to demonstrations that last days and weeks,” Vermillion says.

There’s also the problem of scale. Smaller kites are cheaper to make and easier to develop. But because the weight and drag of the tether increase with height, small kites don’t operate as well at 300 meters or higher, where the wind tends to be strongest. Companies want to scale up to larger, more efficient kites that can fly higher and produce megawatts of power. [10 ]The modeling of each part of the KGS is presented in the second section, including the kite simplified mathematical model, its produced mechanical power expression adopted in, and a fairly detailed modeling of the power transformation system. [11]

At Boston College, biomedical engineer Glenn Gaudette is using decellularization techniques on spinach leaves, coating them in human heart cells to engender cardiovascular tissues. [12] He was drawn to spinach in particular because its veiny structure is ideal for supplying oxygen and nutrients to heart cells, as well as to flush out metabolic waste. He plans to sew the central vein of the decellularized spinach onto the [13] hearts main artery, the aorta, in order to facilitate blood flow to damaged heart muscles. The rest of the leaf would blanket the general area, expanding and contracting with each heartbeat. Eventually, he also envisions folding spinach leaves into the shape of a human heart and sprouting an entire organ.

[14] Gaudette anticipates that less than five years of bench-side research likely remains before plant-based scaffolds can be used in clinical trials involving relatively straightforward tissues like skin. Before then, simple issues need addressing, such as ensuring that the soapy detergents used to decellularize the plants are fully washed away prior to implantation. And more serious concerns exist too. For instance, researchers need to determine how a patient’s immune system might respond to cellulose (although Gaudette’s unpublished work, as well as Pelling’s preliminary studies in mice and rats, has shown promising results). Gaudette thinks one strategy in humans might involve reverting a patient’s own cells back into stem cells, and cultivating them on the spinach scaffold prior to implantation. This might ultimately help the immune system accept the new tissue as part of the body.

According to Gaudette, there’s still work to be done, but researchers are getting closer. “It's fun to dream, right?” he says. “I think we have an opportunity to start a new industry.”

Like Pelling’s lab, Gaudette’s team has begun engineering edible, plant-based scaffolds capable of producing environmentally-friendly, lab-grown meat. While bread crumb scaffolds would be well-suited to what Gaudette calls ground “mush meat,” [15] soy protein is a spherical protein isolated from soy beans and it has long storage stability.

As researchers continue to scan the grocery aisles for the next scaffold innovation, [16] its becoming clear that some plants are better suited to certain applications than others. For example, Gaudette’s colleagues are using bamboo to regenerate teeth because it’s tough and has a small diameter. Peaches, by contrast, are far too soft to support structures for grinding and chomping food.

Gaudette’s work on spinach scaffolds has become recommended reading for students in bioengineer Grissel Trujillo de Santiago’s biomaterials class at Tecnológico de Monterrey in Mexico. [17] Growing up in Brazilian slums, Trujillo de Santiago is finding ways to 3D print living tissues. Like Gaudette and Pelling, she aims to engineer elegant ways to [18] fabricate vascular systems that mimic human blood vessels. Unlike Gaudette and Pelling, though, her team is using water-filled networks called hydrogels rather than cellulose.

She’s intrigued by the possibility of employing plant-derived structures to grow both human tissues and edible meats. The latter application, in particular, would require scaffolds to be cost-effective and scalable, she says, to meet the demands of carnivores around the world.

In terms of medical uses, Trujillo de Santiago says the Pelling lab’s previous success implanting mice with apple scaffolds is promising. Besides testing the scaffolds in humans and ensuring our immune systems respond well to the plant-based material, she says researchers will need to demonstrate that their implants will function like the tissues they are intended to augment or replace.

Although Trujillo de Santiago has yet to experiment with plant-derived scaffolds herself, she is beginning to use plant viruses to create structures for mammalian cells. The viruses are harmless to mammals such as mice and humans, and come together to form a mesh-like material that helps anchor cells. [19] As she puts it “We have this portfolio of biomaterials in nature that we can use for human health.”

[20] Back at the University of Ottawa Pelling, Modulevsky and their colleague Charles Cuerrier have founded a company based on their most promising decellularized fruits and veggies. One of their techniques, which uses asparagus scaffolds to regenerate spinal cords in rats, was recently designated a breakthrough device by the U.S. Food and Drug Administration. Unlike many existing scaffolds that are designed to degrade over time, [21] the Pelling lab inserts are less likely to be broken down by enzymes in the human body and release toxic byproducts. Although it will be a few years until their decellularized asparagus will be tested in humans, the researchers are optimistic.

Not every vegetable will lead to a breakthrough device, but Pelling says each new idea has value. “Your students—the ones who are willing to work in a lab like this—they're going through the exercise of discovery,” he says. “And when you stumble onto the random discovery that’s actually important, your whole team is trained and ready to execute.”

After the strict pandemic restrictions lifted, Holmes returned to campus with her colleagues. There, she continued concocting various soda bread recipes and baking them in the lab’s sterilization oven. She’s now nearing graduation, and intends to apply the open-minded approach she learned in the Pelling lab to a career in speech pathology. Her main take-away? [22]

Between the eighth and eleventh centuries A. D., the Byzantine Empire [23] brought an almost unparalleled economic and cultural revival, a recovery that is all the more striking because it followed a long period of severe internal decline. [24] By the early eighth century, the empire had lost roughly two-thirds of the territory it had possessed in the year 600, its remaining area was being raided by Arabs and Bulgarians, who at times threatened to take Constantinople and extinguish the empire altogether. The wealth of the state and its subjects was greatly diminished, and artistic and literary production had virtually [25] ceased. By the early eleventh century, however, the empire had regained almost [26] half of its lost possessions; its new frontiers were secure, and its influence extended far beyond its borders. The economy had recovered, the treasury was full, and art and scholarship had advanced.

[27] After all, these three forms of progress have gone together in a number of states and civilizations. Rome under Augustus and fifth-century Athens provide the most obvious examples in antiquity. Moreover, an examination of the apparent sequential connections among military, economic, and cultural forms of progress might help explain the dynamics of historical change.

The common explanation of these apparent connections in the case of Byzantium would run like [28] this, when the empire had turned back enemy raids on its own territory and had begun to raid and conquer enemy territory, Byzantine resources naturally expanded and more money became available to patronize art and literature. Therefore, [29] Byzantine military achievements led to economic advances, which in turn led to cultural revival.

No doubt this hypothetical pattern did apply at times during the course of the recovery. [30] However it is not clear that military advances invariably came first, economic advances second, and intellectual advances third. (4) Finally, the Byzantine revival of learning appears to have begun even earlier. (3) The beginning of the empire’s economic revival, however, can be placed between 810 and 830. (1) A number of notable scholars and writers appeared by 788 and, by the last decade of the eighth century, a cultural revival was in full bloom, a revival that lasted until the fall of Constantinople in 1453.  (2) In the 860s, the Byzantine Empire [31] began to recover from Arab incursions so that by 872 the military balance with the Abbasid Caliphate had been permanently altered in the empire’s favor.Thus the commonly expected order of military revival followed by economic and then by cultural recovery was reversed in Byzantium. [32] The wealth of Constantinople can be seen by how Justin I used 3,700 pounds/1.66 tonnes of gold just for celebrating his own consulship. [33]

If we abolish the dream displacement, we attain through analysis quite certain conclusions regarding two problems of the dream which are most disputed—as to what [34] ignites a dream at all, and as to the connection of the dream with our waking life. There are dreams which at once expose their links with the events of the day; in others no trace of such a connection can be found. [35] By the aid of analysis, it can be shown that every dream, without any exception,linking up with our impression of the day, or perhaps it would be more correct to say of the day previous to the dream. The impressions which have incited the dream may be so important that we are not surprised at our being occupied with them whilst awake; in this case we are right in saying that the dream carries on the chief interest of our waking life. More usually, however, when the dream contains anything relating to the impressions of the day, it is [36] so trivial, unimportant, and undeserving that we can only recall it with an effort. The dream content appears, then, even when coherent and intelligible, to be concerned with those indifferent trifles of thought undeserving of our waking interest. The depreciation of dreams is largely due to the predominance of the indifferent and the worthless in their [37] content.

[38] Analysis relies un such arguments to prove worthy. When the dream content discloses nothing but some indifferent impression as instigating the dream, analysis ever indicates some significant event, which has been replaced by something indifferent with which it has entered into abundant associations. Where the dream is concerned with uninteresting and unimportant conceptions, analysis [39] revealed the numerous associative paths which connect the trivial with the momentous in the psychical estimation of the individual. It is only the action of displacement if what is indifferent obtains recognition in the dream content instead of those impressions which are really the stimulus, or instead of the things of real interest. In answering the question as to what provokes the dream, as to the connection of the dream, in the daily troubles, we must say, in terms of the insight given us by replacing the manifest latent dream content: The dream does never trouble itself about things which are not deserving of our [40] concern during the day, because trivialities which do not trouble us during the day have no power to pursue us whilst asleep.

What provoked the dream in the example which we have [41] recounted? The really unimportant event, that a friend invited me to a free ride in his cab. The table d'hôte scene in the dream contains an allusion to this indifferent motive, for in conversation I had brought the taxi parallel with the table d'hôte. But I can indicate the important event which has as its substitute the trivial one.[42] A few days before I had disbursed a  a member of my family for large sum of money who is very dear to me. Small wonder, says the dream thought, if this person is grateful to me for this—[43] this love is not cost-free. But love that shall cost nothing is one of the prime thoughts of the dream. The fact that shortly before this I [44] had several drives with the relative in question puts the one drive with my friend in a position to recall the connection with the other person. The indifferent impression which, by such ramifications, provokes the dream is subservient to another condition which is not true of the real source of the dream—the impression must be a recent one, we may now ask whence the wish fulfilled in the dream originates.